TECHNICAL FIELD

The present invention relates generally to methods of making supported catalysts (e.g. supported gold, ruthenium, palladium, or platinum catalysts), particularly carbon- supported catalysts (e.g. carbon-supported gold, ruthenium, palladium, or platinum catalysts). The present invention further relates to the supported catalysts made by said methods and the use of the supported catalysts to make vinyl chloride, for example by acetylene hydrochlorination. In particular, the present invention relates generally to methods of making supported gold catalysts, particularly carbon-supported gold catalysts, and the catalysts made by said methods. The present invention further relates to the use of the supported gold catalysts to make vinyl chloride, for example by acetylene hydrochlorination.

BACKGROUND

The hydrochlorination of acetylene to produce vinyl chloride monomer (VCM) as the precursor to polyvinyl chloride (PVC) is currently a large scale industrial process, particularly in coal rich areas such as China. Over 13 million tonnes of VCM are produced annually through acetylene hydrochlorination with the vast majority utilising mercuric chloride (HgCh) catalysts supported on activated carbon. The mercury catalyst poses significant environmental concerns due to volatile HgCh subliming from the catalyst bed, up to 0.6 kg Hg/tonne VCM production. Due to the environmental impact of this process, the recently ratified Minamata convention dictates that all new VCM plants must use mercury free catalysts and in the near future all existing industrial plants must switch to mercury free alternatives. This has revived the commercial interest in using gold (Au) and other metals as a catalyst for this reaction.

The conditions used to prepare the gold catalysts are thought to affect the acetylene hydrochlorination reaction profiles. Typically, acidic and/or strongly oxidising solvents are used to carry out a wet impregnation of a HAuCL precursor in order to obtain active catalysts. Concentrated nitric acid, hydrochloric acid and aqua regia (a mixture of nitric acid and hydrochloric acid, often in a ratio of 1 :3 v/v nitric acid : hydrochloric acid) have been used to produce active catalysts. Compositions comprising organic compounds (e.g., pyridine, A/,/V-dimethylformamide and imidazole) and thionyl chloride (SOC ) termed“organic aqua regia (OAR)” have been used as alternatives to the acidic and/or strongly oxidising solvents. However, OAR does not provide a real environmentally friendly alternative compared to other approaches. Alternatively, active catalysts may be prepared in aqueous media in the presence of sulphur-containing ligands However, the toxicity of sulphur-containing ligands such as thiocyanate makes large scale preparations and utilisation unsuitable.

It is therefore desirable to provide alternative and/or improved methods for making catalysts suitable to make vinyl chloride by acetylene hydrochlorination. It is therefore desirable to provide alternative and/or improved methods for making gold catalysts suitable to make vinyl chloride by acetylene hydrochlorination.

BRIEF DESCRIPTION OF THE FIGURES

The present invention may be further described with reference to the following Figures in which:

Figure 1 shows a) Steady state acetylene conversion of 1% Au/C catalysts prepared by wet impregnation of HAuCU from various alcohol (·), ketone (A), ether (¨) and aqueous solvents (■); the dotted line indicates the activity of the conventionally prepared aqua regia catalyst b) X-ray diffraction patterns of fresh 1% Au/C catalysts prepared with these various solvents ( Test Conditions: 90 mg catalyst, 23.5 ml_ min ^-1 C2H2, 23.7 ml_ min ^-1 HCI and 2.70 ml_ min ¹ Ar, 200 °C);

Figure 2 shows a) Steady state acetylene conversion of 1% Au/C catalysts prepared by wet impregnation of HAuCU from extra dry acetone with the addition of various amounts of water b) X-ray diffraction patterns of fresh 1% Au/C catalysts prepared with various acetone/water mixtures ( Test Conditions: 90 mg catalyst, 23.5 ml_ min ^-1 C2H2, 23.7 ml_ min- ¹ HCI and 2.70 ml_ min ¹ Ar, 200 °C);

Figure 3 shows Time-online acetylene hydrochlorination activity profile of the Au/C- Acetone (A), Au/C-Aqua regia (·) and AU/C-H2O (¨) catalysts ( Test Conditions: 90 mg catalyst, 23.5 ml_ min ¹ C2H2, 23.7 ml_ min ¹ HCI and 2.7 ml_ min ¹ Ar, 200 °C);

Figure 4 shows a) Representative STEM-HAADF image of the freshly prepared 1 % Au/C-Acetone material b) Au l_3-edge XANES of 1% Au/C-Acetone prior to reaction (- fresh) and after 4 h of reaction (- used), 1% Au/C-aqua regia and Au foil c) Linear combination fitting of the Au L3-edge XANES for 1% Au/C-aqua regia, 1% Au/C-Acetone (fresh) and 1% Au/C-Acetone (used) d) Fourier transform of the k ³ -weighted c EXAFS data of 1% Au/C-Acetone (fresh) and 1% Au/C-Acetone (used), 1 % Au/C-Aqua regia and Au foil;

Figure 5 shows Two-day time-on-line acetylene hydrochlorination activity profiles of the Au/C-Acetone (A) and Au/C-aqua regia (■) catalysts ( Test Conditions: 90 mg catalyst, 23.5 mL min- ¹ C ₂ H ₂ , 23.7 mL min ¹ HCI and 2.7 mL min ¹ Ar, 200 °C);

Figure 6 shows X-ray diffraction patterns of catalysts prepared using various solvents and drying temperatures with nominal metal loading of 1 wt% Au;

Figure 7 shows X-ray diffraction patterns of fresh Au/C-Acetone catalyst (fresh), Au/C- Acetone after 4h of reaction (used 4 h) and after a further 3 h of reaction (used 7 h);

Figure 8 shows the acetylene hydrochlorination activity profile of the Au/C-Acetone (■) catalysts ( Test Conditions: 90 mg catalyst, 23.5 mL min ¹ C ₂ H ₂ , 23.7 mL min ¹ HCI and

2.7 mL min ¹ Ar, 180 °C);

Figure 9 shows the acetylene hydrochlorination activity profile of the Pt/C-Acetone (·) catalysts ( Test Conditions: 90 mg catalyst, 23.5 mL min ¹ C ₂ H ₂ , 23.7 mL min ¹ HCI and

2.7 mL min- ¹ Ar, 180 °C);

Figure 10 shows the acetylene hydrochlorination activity profile of the Pd/C-Acetone (A) catalysts ( Test Conditions: 90 mg catalyst, 23.5 mL min ¹ C ₂ H ₂ , 23.7 mL min ¹ HCI and

2.7 mL min- ¹ Ar, 180 °C);

Figure 11 shows the acetylene hydrochlorination activity profile of the Ru/C-Acetone (¨) catalysts ( Test Conditions: 90 mg catalyst, 23.5 mL min ¹ C ₂ H ₂ , 23.7 mL min ¹ HCI and

2.7 mL min- ¹ Ar, 180 °C);

Figure 12 shows the Fourier transform of the k ³ -weighted c EXAFS data of 1 % Au/C- Acetone (fresh -■) and 1% Au/C-Acetone (used - T) and Au foil (¨); Figure 13 shows the Fourier transform of the k ³ -weighted c EXAFS data of 1 % Pt/C- Acetone (fresh -■) and 1 % Pt/C-Acetone (used - T) and Pt foil (¨);

Figure 14 shows the Fourier transform of the k ² -weighted c EXAFS data of 1 % Pd/C- Acetone (fresh -■) and 1 % Pd/C- Acetone (used - T) and Pd foil (¨);

Figure 15 shows the Fourier transform of the k ² -weighted c EXAFS data of 1 % Ru/C- Acetone (fresh -■) and 1 % Ru/C-Acetone (used - T) and Ru foil (¨);

Figure 16 shows a representative STEM-HAADF image of the freshly prepared 1 % Au/C- Acetone material;

Figure 17 shows a representative STEM-HAADF image of the used 1 % Au/C-Acetone material;

Figure 18 shows a representative STEM-HAADF image of the freshly prepared 1 % Pt/C- Acetone material;

Figure 19 shows a representative STEM-HAADF image of the used 1 % Pt/C-Acetone material;

Figure 20 shows a representative STEM-HAADF image of the freshly prepared 1 % Pd/C- Acetone material;

Figure 21 shows a representative STEM-HAADF image of the used 1 % Pd/C-Acetone material;

Figure 22 shows a representative STEM-HAADF image of the freshly prepared 1 % Ru/C- Acetone material;

Figure 23 shows a representative STEM-HAADF image of the used 1 % Ru/C-Acetone material;

Figure 24 shows X-ray diffraction patterns of fresh Au/C-Acetone catalyst;

Figure 25 shows X-ray diffraction patterns of fresh Pt/C-Acetone catalyst; Figure 26 shows X-ray diffraction patterns of fresh Pd/C-Acetone catalyst;

Figure 27 shows X-ray diffraction patterns of fresh Ru/C-Acetone catalyst;

Figure 28 shows Pt l_3-edge XANES of 1 % Pt/C-Acetone prior to reaction compared with Pt foil and Pt(acac)2;

Figure 29 shows Pd K-edge XANES of 1 % Pd/C-Acetone prior to reaction compared with Pd foil and Pd(acac)2;

Figure 30 shows Ru K-edge XANES of 1% Ru/C-Acetone prior to reaction compared Ru foil and Ru(acac)3.

SUM MARY

In accordance with a first aspect of the present invention there is provided a method for making a catalyst, the method comprising combining a gold, ruthenium, palladium, or platinum precursor, a solvent, and a support material, wherein the solvent comprises an organic solvent and wherein the solvent does not comprise organic aqua regia.

In certain embodiments of the first aspect of the present invention the precursor is a gold precursor.

In certain embodiments of the first aspect of the present invention the precursor is a ruthenium precursor.

In certain embodiments of the first aspect of the present invention the precursor is a palladium precursor.

In certain embodiments of the first aspect of the present invention the precursor is a platinum precursor.

In accordance with a second aspect of the present invention there is provided a method for making a catalyst, the method comprising combining a gold precursor, a solvent, and a support material, wherein the solvent comprises an organic solvent and wherein the solvent does not comprise organic aqua regia. In certain embodiments of the first aspect of the invention, the method comprises forming a solution of the precursor in the solvent, and combining the solution with the support material.

In certain embodiments of the second aspect of the invention, the method comprises forming a solution of the gold precursor in the solvent, and combining the solution with the support material.

In certain embodiments of the first aspect of the invention, the method further comprises drying the product of the step of combining the precursor, solvent and support material.

In certain embodiments of the second aspect of the invention, the method further comprises drying the product of the step of combining the gold precursor, solvent and support material.

In certain embodiments of any aspect of the invention, the solvent has an ET(30) polarity equal to or less than about 62. For example, the solvent may have an ET(30) polarity equal to or less than about 60 or equal to or less than about 55 or equal to or less than about 50.

In certain embodiments of any aspect of the invention, the solvent comprises equal to or less than about 50 vol% water. For example, the solvent may comprise equal to or less than about 10 vol% water or equal to or less than about 5 vol% water.

In certain embodiments of any aspect of the invention, the solvent has a pH equal to or greater than about 5. For example, the solvent may have a pH equal to or greater than about 6 or equal to or greater than about 7.

In certain embodiments of any aspect of the invention, the solvent has a boiling point equal to or less than about 120°C. For example, the solvent may have a boiling point equal to or less than about 100°C or equal to or less than about 90°C.

In certain embodiments of any aspect of the invention, the support material may comprise, consist essentially of or consist of carbon such as activated carbon. In accordance with a third aspect of the present invention there is provided a catalyst comprising atomically dispersed cationic gold species and a support material, wherein: equal to or greater than about 58% of the gold exists in the Au(l) oxidation state; and/or

equal to or less than about 42% of the gold exists in the Au(lll) oxidation state; and/or

the catalyst provides a steady state acetylene conversion greater than about 18%; and/or

equal to or greater than about 80% of the gold in the catalyst is atomically dispersed.

In accordance with a fourth aspect of the present invention there is provided a catalyst comprising atomically dispersed cationic gold, ruthenium, palladium, or platinum species and a support material.

In certain embodiments of the fourth aspect of the present invention the catalyst provides a steady state acetylene conversion greater than about 18 %.

In certain embodiments of the fourth aspect of the present invention equal or greater than about 80 % of the gold or ruthenium or palladium or platinum in the catalyst is atomically dispersed.

In certain embodiments of the fourth aspect of the present invention equal to or greater than about 58%, for example equal to or greater than about 70%, of the gold exists in the Au(l) oxidation state.

In certain embodiments of the fourth aspect of the present invention equal to or greater than about 60 %, for example equal to or greater than about 70% or equal to or greater than about 80%, of the ruthenium exists in the Ru(lll) oxidation state.

In certain embodiments of the fourth aspect of the present invention equal to or greater than about 60%, for example equal to or greater than about 70% or equal to or greater than about 80%, of the palladium exists in the Pd(ll) oxidation state. In certain embodiments of the fourth aspect of the present invention equal to or greater than about 60%, for example equal to or greater than about 70% or equal to or greater than about 80%, of the platinum exists in the Pt(ll) oxidation state.

In accordance with a fifth aspect of the present invention there is provided a catalyst obtained by and/or obtainable by a method according to any aspect or embodiment of the present invention. The catalyst of the fifth aspect of the present invention may be in accordance with the catalyst of the third or fourth aspect of the present invention, including all embodiments thereof in any combination.

In certain embodiments of any aspect of the present invention, equal to or less than about 10 % of the gold or ruthenium or palladium or platinum in the catalyst exists in the form of nanoparticles. For example, equal to or less than about 5 % of the gold or ruthenium or palladium or platinum in the catalyst exists in the form of nanoparticles.

In certain embodiments of any aspect of the present invention, equal to or less than about 10 % of the gold in the catalyst exists in the form of nanoparticles. For example, equal to or less than about 5 % of the gold in the catalyst exists in the form of nanoparticles.

In certain embodiments of any aspect of the present invention, equal to or greater than about 80 % of the gold or ruthenium or palladium or platinum in the catalyst is atomically dispersed. For example, equal to or greater than about 90 % of the gold or ruthenium or palladium or platinum in the catalyst is atomically dispersed.

In certain embodiments of any aspect of the present invention, equal to or greater than about 80 % of the gold is atomically dispersed. For example, equal to or greater than about 90 % of the gold in the catalyst is atomically dispersed.

In certain embodiments of any aspect of the present invention, equal to or less than about 10 % of the gold or ruthenium or palladium or platinum in the catalyst exists in the form of dimers and sub nanometre clusters. For example, equal to or less than about 5 % of the gold or ruthenium or palladium or platinum in the catalyst exists in the form of dimers and sub nanometre clusters. In certain embodiments of any aspect of the present invention, equal to or less than about 10 % of the gold exists in the form of dimers and sub nanometre clusters. For example, equal to or less than about 5 % of the gold exists in the form of dimers and sub nanometre clusters.

In certain embodiments of any aspect of the present invention, the catalyst has an X- Ray Diffraction pattern that does not have a 2Q reflection at one or more of 38, 44, 64 and 77°. This may, for example, be particularly applicable to gold catalysts.

In certain embodiments of any aspect of the present invention, the catalyst has an X- Ray Diffraction pattern that does not have a 2Q reflection at one or both of 42.2 and 44°. This may, for example, be particularly applicable to ruthenium catalysts.

In certain embodiments of any aspect of the present invention, the catalyst has an X- Ray Diffraction pattern that does not have a 2Q reflection at 40°. This may, for example, be particularly applicable to palladium catalysts.

In certain embodiments of any aspect of the present invention, the catalyst has an X- Ray Diffraction pattern that does not have a 2Q reflection at one or more of 42.9, 46.4, 67.9, 81.8 and 86.2°. This may, for example, be particularly applicable to platinum catalysts.

The catalyst in accordance with any aspect or embodiment of the present invention (including all combinations thereof) may, for example, provide a steady state acetylene conversion greater than about 3 %. For example, the catalyst in accordance with any aspect or embodiment of the present invention (including all combinations thereof) may provide a steady state acetylene conversion greater than about 18 %.

In accordance with a sixth aspect of the present invention there is provided a use of a catalyst in accordance with any aspect or embodiment of the present invention (including all combinations thereof) in a method of making vinyl chloride, for example in a method of hydrochlorination of acetylene.

Certain embodiments of any aspect of the present invention may provide one or more of the following advantages: • good (e.g. improved) activity, for example for acetylene hydrochlorination;

• good (e.g. improved) stability, for example for acetylene hydrochlorination;

• good (e.g. improved) selectivity, for example for vinyl chloride;

• less severe process conditions (e.g. reduced temperature and/or pressure, less acidic reactants, reduced number of reactants);

• environmentally friendly product and/or process.

The details, examples and preferences provided in relation to any particulate one or more of the stated aspects of the present invention will be further described herein and apply equally to all aspects of the present invention. Any combination of the embodiments, examples and preferences described herein in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein, or otherwise clearly contradicted by context. DETAILED DESCRIPTION

Method of Making a Catalyst

There is provided herein a method of making a catalyst. The method comprises combining a gold precursor, ruthenium precursor, palladium precursor, or platinum precursor, a solvent, and a support material. The term“precursor” is used herein to generally refer to gold precursors, ruthenium precursors, palladium precursors and platinum precursors. The method may, for example, comprise combining a gold precursor, a solvent and a support material. As used herein, the term “combining” involves contacting the one or more products. This may, for example, comprise mixing or stirring the products together.

The method may, for example, be referred to as an impregnation or a wet impregnation method, whereby the precursor is impregnated on a catalyst support material, for example whereby the precursor is dissolved in the solvent and then impregnated on a catalyst support material. The method may, for example, be referred to as an impregnation or a wet impregnation method, whereby the gold precursor is impregnated on a catalyst support material, for example whereby the gold precursor is dissolved in the solvent and then impregnated on a catalyst support material. The method may, for example, be an incipient wetness impregnation method whereby the amount of solution used is calculated to be just enough to fill the pores of the support. Therefore, the method may comprise forming a solution of the precursor in the solvent, and combining the solution with the support material. Therefore, the method may comprise forming a solution of the gold precursor in the solvent, and combining the solution with the support material. The method may, for example, comprise dissolving the precursor in the solvent, and combining the solution with the support material. The method may, for example, comprise dissolving the gold precursor in the solvent, and combining the solution with the support material. The precursor solution may, for example, be combined with the support material in drops, for example with stirring, or by spraying.

The amount of each of the precursor, solvent and support material may be selected in order to obtain the desired amount of catalyst, for example with a desired gold or ruthenium or palladium or platinum loading level. The amount of each of the gold precursor, solvent and support material may be selected in order to obtain the desired amount of catalyst, for example with a desired gold loading level.

The combining of the precursor, solvent and support material may take place under any suitable conditions. For example, the combining of the gold precursor, solvent and support material may take place under any suitable conditions. For example, the combining may take place at ambient temperature and/or pressure. For example, the combining may take place at a temperature ranging from about 15°C to about 25°C. For example, the combining may take place at a pressure ranging from about 95 to about 105 kPa, for example about 101 kPa. Stirring may be used to combine the precursor, solvent and support material. Stirring may be used to combine the gold precursor, solvent and support material.

The method may further comprise a drying step. For example, the method may further comprise drying the product of the step of combining the precursor, solvent and support material. For example, the method may further comprise drying the product of the step of combining the gold precursor, solvent and support material. For example, the method may further comprise drying in order to remove the solvent.

The drying may, for example, occur at a temperature higher than the boiling point of the solvent. For example, the drying may occur at a temperature at least about 2°C higher, for example at least about 3°C higher, for example at least about 4°C higher, for example at least about 5°C higher than the boiling point of the solvent. For example, the drying may occur at a temperature up to about 15°C higher, for example up to about 12°C, for example up to about 10°C higher than the boiling point of the solvent. For example, the drying may occur at a temperature from about 2°C higher to about 15°C higher than the boiling point of the solvent, for example from about 5°C higher to about 10°C higher than the boiling point of the solvent. The drying may, for example, occur at a temperature equal to or less than about 120°C. For example, the drying may occur at a temperature equal to or less than about 1 10°C, for example equal to or less than about 100°C, for example equal to or less than about 90°C. The drying may, for example, occur at a temperature equal to or greater than about 40°C. For example, the drying may occur at a temperature equal to or greater than about 50°C or equal to or greater than about 60°C. For example, the drying may occur at a temperature ranging from about 40°C to about 120°C, for example from about 50°C to about 100°C, for example from about 60°C to about 90°C.

The drying may, for example, take place at ambient pressure or higher. For example, the drying may take place at a pressure ranging from about 95 to about 105 kPa, for example equal to or greater than about 101 kPa, for example from about 101 kPa to about 105 kPa.

The drying may, for example, take place until the mass of the product does not change. The drying may, for example, take place until all of the solvent is removed. The drying may, for example, take place for up to about 24 hours, for example up to about 20 hours, for example up to about 16 hours.

The drying may, for example, take place under the flow of an inert gas. By inert gas, it is meant a gas that does not react with the catalyst produced by the method. The drying may, for example, take place under the flow of nitrogen gas (N2).

The method for making the catalyst may, for example, be in accordance with the method described in G. Malta et ai, Science, 2017, 355, pages 1399-1403 (the contents of which are incorporated herein by reference), except that a different solvent and optionally a different temperature and/or pressure is used.

The method for making the catalyst may, for example, exclude the use of any additional reducing agents. The method for making the catalyst may, for example, exclude an additional step (i.e. in addition to the steps described herein) intended to reduce the gold, ruthenium, palladium or platinum in the catalyst. This may, for example, be reflected in the atomically dispersed state of the metal species and/or the oxidation state of the metal in the catalyst. For example, the catalyst may not comprise or may comprise only a small amount of Au(0) or Ru(0) or Pd(0) or Pt(0).

The method for making the catalyst may, for example, exclude the use of a linear or branched chain alkene fixing agent. The method may, for example, exclude the use of a fixing agent. The method for making the catalyst may, for example, exclude a fixing step using a linear or branched chain alkene. The method for making the catalyst may, for example, exclude a fixing step.

The precursor (i.e. gold precursor or ruthenium precursor or palladium precursor or platinum precursor) may be any compound including gold, ruthenium, palladium, or platinum that is suitable to make a catalyst comprising atomically dispersed cationic gold, atomically dispersed cationic ruthenium, atomically dispersed cationic palladium, or atomically dispersed cationic platinum as described herein. The precursor may, for example, dissolve in the solvent used in the method for making a catalyst described herein. The precursor may, for example, include one or more acetylacetonate ligands.

The gold precursor may be any compound including gold that is suitable to make a catalyst comprising atomically dispersed cationic gold as described herein. The gold precursor may, for example, dissolve in the solvent used in the method for making a catalyst described herein. The gold precursor may, for example, include one or more chloride anions.

Suitable gold precursors include, for example, elemental gold (Au), chloroauric acid (HAuCU) such as chloroauric trihydrate and/or tetra hydrate), gold (III) chloride (AuCh), gold (I) chloride (AuCI), gold acetate (e.g. gold (III) acetate, Au(0 ₂ CCH ₃ ) ₃ ) and combinations of one or more thereof.

Suitable ruthenium precursors include, for example, ruthenium (III) acetylacetonate (Ru(acac)3), ruthenium (III) chloride (RuCh), and combinations thereof.

Suitable palladium precursors include, for example, palladium (II) acetylacetonate (Pd(acac)2), palladium (II) acetate (Pd(OAc)2), palladium (II) nitrate dehydrate (Pd(NC>3)2.2H20), and combinations of one or more thereof. Suitable platinum precursors include, for example, platinum (II) acetylacetonate (Pt(acac)2), which may also be referred to as platinum (II) 2,4-pentanedionate. The solvent may, for example, have an ET(30) polarity equal to or less than about 62. For example, the solvent may have an ET(30) polarity equal to or less than about 60, for example equal to or less than about 58, for example equal to or less than about 56, for example equal to or less than about 55, for example equal to or less than about 54, for example equal to or less than about 52, for example equal to or less than about 50, for example equal to or less than about 48, for example equal to or less than about 46, for example equal to or less than about 45, for example equal to or less than about 44, for example equal to or less than about 42, for example equal to or less than about 40. For example, the solvent may have an ET(30) polarity equal to or less than about 50. For example, the solvent may have an ET(30) polarity ranging from about 20 to about 60, for example from about 25 to about 55, for example from about 30 to about 50, for example from about 35 to about 50.

Advantageously, the present inventors have provided methods for making a gold or ruthenium or palladium or platinum catalyst that do not require the use of strongly acidic or highly oxidising solvents such as aqua regia and organic aqua regia. Advantageously, the present inventors have provided methods for making a gold catalyst that do not require the use of strongly acidic or highly oxidising solvents such as aqua regia and organic aqua regia. The presently disclosed methods for making a catalyst also do not require the use of sulphur-containing ligands.

The solvent comprises an organic solvent. The solvent may, for example, consist essentially of or consist of one or more organic solvents. The organic solvent may, for example, be selected from the group consisting of alcohols, ketones, esters, ethers, sulphoxides, nitriles and amides. The solvent may, for example, comprise, consist essentially of or consist of a mixture of different solvents. For example, the solvent may comprise, consist essentially of or consist of a mixture of one or more organic solvents. The solvent may, for example, be a non-aqueous solvent. The solvent may be a liquid solvent. The organic solvent is not organic aqua regia. As used herein, the term“organic aqua regia” refers to a solvent comprising (for example consisting essentially of or consisting of) thionyl chloride (SOC ) and one or more organic compounds such as pyridine, N,N- dimethylformamide and imidazole.

The term“alcohol” may relate to any organic compound in which the hydroxyl functional group (-OH) is bound to a carbon (R-OH). R may, for example, be a straight chain or branched chain or cyclic hydrocarbon, which may be saturated or unsaturated. R may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The alcohol may, for example be selected from methanol, ethanol, 1-propanol, 2-propanol, n-butanol, sec-butanol, isobutanol and tert-butanol.

The term“ketone” may relate to any organic compound including a -C=0 group bound to two carbon atoms (R(CO)R). Each R may independently be a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. Each R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively the R groups may be linked to form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The ketone may, for example, be selected from acetone, butanone, pentanone and hexanone (e.g. cyclohexanone).

The term“ester” may relate to any organic compound including a -C(=0)(OR) group bound to a carbon atom (RC(O)OR). Each R may independently be a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. Each R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively the R groups may be linked to form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The ester may, for example, be an alkyl acetate such as ethyl acetate.

The term“ether” may relate to any organic compound including an -O- group bound to two carbon atoms (R-O-R). Each R may independently be a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. Each R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively the R groups may be linked to form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The ether may, for example, be selected from dialkyl ethers (where each alkyl group may be the same or different) such as diethyl ether and tetrahydrofuran.

The term“sulphoxide” may relate to any organic compound including an -S(=0) group, where the S atom is bound to two carbon atoms (R-S(=0)-R). Each R may independently be a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. Each R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively the R groups may be linked to form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The sulphoxide may, for example, be a dialkyl sulphoxide (where each alkyl group may be the same or different) such as dimethyl sulphoxide (DMSO).

The term“nitrile” may relate to any organic compound including a -CºN group bound to a carbon atom (R-CºN). R may be a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively R may form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The nitrile may, for example, be selected from alkylnitriles such as acetonitrile.

The term“amide” may relate to any organic compound including a R-C(=0)-NRR group. Each R may independently be hydrogen or a straight chain or branched chain hydrocarbon, which may be saturated or unsaturated. Each R may independently comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. Alternatively one or more R groups may be linked to form a cyclic molecule, which may be saturated or unsaturated. The cyclic molecule may, for example, comprise from 1 to 20 carbon atoms, for example from 1 to 10 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms. The amide may, for example, be selected from dialkylformamide (where each alkyl group may be the same or different) such as dimethylformamide (DMF).

The hydrocarbons in the alcohols, ketones, esters, ethers, sulphoxides, nitriles and amides may or may not be substituted with one or more other functional groups.

The solvent may, for example, comprise, consist essentially of or consist of one or more of methanol, ethanol, propanol, butanol, acetone, butanone, ethyl acetate, diethyl ether, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and cyclohexanone. For example, the solvent may, for example, comprise, consist essentially of or consist of one or more of methanol, ethanol, propanol, butanol, acetone, butanone, ethyl acetate, diethyl ether and tetrahydrofuran (THF). For example, the solvent may comprise, consist essentially of or consist of acetone.

For example, when the precursor is a gold precursor, the solvent may comprise, consist essentially of or consist of one or more of methanol, ethanol, propanol, butanol, acetone, butanone, ethyl acetate, diethyl ether, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and cyclohexanone. For example, when the precursor is a gold precursor, the solvent may comprise, consist essentially of or consist of one or more of methanol, ethanol, propanol, butanol, acetone, butanone, ethyl acetate, diethyl ether and tetrahydrofuran (THF).

For example, when the precursor is a ruthenium precursor, a palladium precursor, or a platinum precursor, the solvent may comprise, consist essentially of, or consist of acetone.

The solvent may, for example, comprise equal to or less than about 50 vol% water. For example, the solvent may comprise equal to or less than about 45 vol%, for example equal to or less than about 40 vol%, for example equal to or less than about 35 vol%, for example equal to or less than about 30 vol%, for example equal to or less than about 25 vol%, for example equal to or less than about 20 vol%, for example equal to or less than about 15 vol%, for example equal to or less than about 10 vol%, for example equal to or less than about 5 vol% water. For example, the solvent may comprise 0 vol% water. For example, the solvent may comprise from 0 vol% to about 50 vol% or from about 0 vol% to about 30 vol% or from about 0% to about 10 vol% water. The solvent may, for example, have a boiling point equal to or less than about 120°C. For example, the solvent may having a boiling point equal to or less than about 1 15°C or equal to or less than about 1 10°C or equal to or less than about 100°C or equal to or less than about 90°C or equal to or less than about 80°C. For example the solvent may have a boiling point equal to or greater than about 40°C or equal to or greater than about 50°C or equal to or greater than about 60°C. For example, the solvent may, for example, have a boiling point ranging from about 40°C to about 120°C or from about 50°C to about 100°C or from about 60°C to about 90°C.

The solvent may, for example, have a pH equal to or greater than about 5. For example, the solvent may have a pH equal to or greater than about 5.5 or equal to or greater than about 6 or equal to or greater than about 6.5 or equal to or greater than about 7 or equal to or greater than about 7.5 or equal to or greater than about 8 or equal to or greater than about 8.5 or equal to or greater than about 9. The solvent may, for example, have a pH equal to or less than about 14. For example, the solvent may have a pH equal to or less than about 13.5 or equal to or less than about 13 or equal to or less than about 12.5 or equal to or less than about 12. For example, the solvent may have a pH ranging from about 5 to about 14 or from about 6 to about 13 or from about 6.5 to about 12.

One or more of the following may be excluded from use in the presently disclosed methods (e.g. the solvent may not comprise, consist essentially of and/or consist of one or more of the following):

• an aqueous solution of nitric acid;

• an aqueous solution of hydrochloric acid;

• an aqueous solution of a combination of nitric acid and hydrochloric acid (aqua- regia);

• an aqueous solution of hydrogen peroxide;

• thionyl chloride and pyridine;

• thionyl chloride and A/,/\/-dimethylformamide;

• thionyl chloride and imidazole;

• thionyl chloride and one or more organic compounds;

• thionyl chloride;

• pyridine;

• A/,/\/-dimethylformamide; • imidazole;

• a strong acid;

• a strong mineral acid;

• a sulphur-containing ligand;

· 1 ,10-phenanthroline;

• Au-thiocyanate complexes;

• Schiff-base Au (e.g. Au(lll)) complexes other than the gold precursor;

• Au (e.g. Au(lll)) complexes other than the gold precursor;

• sulphates, sulphonates, thiourea, thionyl chloride, thiopropionic acid, thiomalic acid, thiosulfate and/or thiocyanates.

In certain embodiments, the methods for making a catalyst described in WO 2013/008004 are excluded from the presently disclosed methods for making a catalyst. Thus, the presently disclosed methods may exclude methods comprising impregnating the catalyst support material with a solution of gold or a compound thereof and a sulphur- containing ligand to form a gold complex and then drying the impregnated support. For example, the presently disclosed methods may exclude methods comprising impregnating the catalyst support material with a solution of gold or a compound thereof and a sulphur-containing ligand to form a gold complex.

A mineral acid refers to any acid derived from one or more inorganic compounds including, for example, sulphuric acid, nitric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid and boric acid. A strong acid refers to any acid that completely dissociates in water.

ET(30) polarity is determined by the method disclosed in C. Reichardt, Agnew. Chem. Int. Ed., 1979, 18, pages 98-110, the contents of which are incorporated herein by reference. The catalyst support material may be any support material suitable to make a catalyst comprising atomically dispersed cationic gold or ruthenium or palladium or platinum as described herein. The catalyst support material may be any support material suitable to make a catalyst comprising atomically dispersed cationic gold as described herein. The catalyst support material may, for example, comprise, consist essentially of or consist of carbon. The carbon may, for example, be obtained from natural sources such as peat, wood, coal, graphite or combinations thereof. The carbon may, for example, be a synthetic carbon. The carbon may, for example, be activated carbon. The activated carbon may, for example, have been activated by steam, acid or another chemical. Activated carbon refers to a form of carbon that has a high surface area (equal to or greater than about 500 m ² per gram as determined by N ₂ gas adsorption). This is thought to be due to the presence of small, low-volume pores. For example, the activated carbon may have a surface area equal to or greater than about 800 m ² per gram, for example equal to or greater than about 1000 m ² per gram, for example equal to or greater than about 1500 m ² per gram, for example equal to or greater than about 2000 m ² per gram, for example equal to or greater than about 2500 m ² per gram, for example equal to or greater than about 3000 m ² per gram. The carbon may, for example, be doped carbon. The carbon may, for example, be high purity or ultra-high purity carbon. The carbon may, for example, be acid washed to remove impurities.

The catalyst support material may, for example, comprise one or more metal oxides such as zeolites, Ti0 ₂ , AI ₂ C>3, K ₂ 0, Zr0 ₂ , Ce0 ₂ , Si0 ₂ and combinations of one more thereof.

The support material (e.g. carbon such as activated carbon) may, for example, be ground to obtain a desired particle size prior to combination with the precursor and solvent. The support material (e.g. carbon such as activated carbon) may, for example, be ground to obtain a desired particle size prior to combination with the gold precursor and solvent.

The support material may, for example, be in the form of a powder, granules or particles in various shapes such as spheres, tablets, cylinders, multi-lobed cylinders, rings, monoliths or combinations of one or more thereof. The catalyst may, for example, be in the form of a monolith.

The support material may, for example, have an average particle size ranging from about 10 pm to about 5 cm. For example, the support material may have an average particle size ranging from about 20 pm to about 4 cm or from about 30 pm to about 3 cm or from about 40 pm to about 2 cm or from about 50 pm to about 1 cm.

Catalyst

There is also provided herein catalysts which may, for example, be obtained by or obtainable by a method as described herein, including all embodiments thereof. The catalyst described herein comprises atomically dispersed cationic gold or ruthenium or palladium or platinum species and a support material. The catalyst described herein may, for example, comprise atomically dispersed cationic gold species and a support material. The support material may be any support material described herein. The atomically dispersed cationic gold or ruthenium or palladium or platinum species may, for example, respectively be in the form of cationic atoms and/or cationic atoms coordinated to one or more ligands such as the ligands from the precursor such as Cl or acetylacetonate. The atomically dispersed cationic gold species may, for example, be in the form of cationic gold atoms and/or cationic gold atoms coordinated to one or more ligands such as Cl. In certain embodiments, the catalyst is not a catalyst described in WO 2013/008004. Thus, in certain embodiments, the catalyst is not a catalyst comprising a complex of gold with a sulphur-containing ligand on a support and is not a catalyst comprising gold, or a compound thereof, and trichloroisocyanuric acid or a metal dichloroisocyanurate on a support. In certain embodiments, the catalyst is not a catalyst comprising gold or a compound of gold and either a) sulphur, b) a compound of sulphur, or c) trichloroisocyanuric acid or a metal dichloroisocyanurate, on a support.

Atomic dispersion can be visualized using high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) as described in the examples below. Dimers, sub-nanometre clusters and nanoparticles can also be visualized using HAADF- STEM. The % of gold or ruthenium or palladium or platinum in the catalyst that is atomically dispersed and the % of gold or ruthenium or palladium or platinum that exists in the form of nanoparticles, dimers and sub-nanometre clusters can be calculated by X- Ray absorption data, assuming that Au(l), Au(lll), Ru(lll), Pd(ll), and Pt(ll) are isolated species and Au(0), Ru(0), Pd(0), and Pt(0) are in the form of nanoparticles. The % of gold in the catalyst that is atomically dispersed and the % of gold that exists in the form of nanoparticles, dimers and sub-nanometre clusters can be calculated by X-Ray absorption data, assuming that Au(l) and Au(lll) are isolated species and Au(0) is in the form of nanoparticles.

Equal to or greater than about 80 % of the gold or ruthenium or palladium or platinum in the catalyst may be atomically dispersed. For example, equal to or greater than about 82 % or equal to or greater than about 84 % or equal to or greater than about 85 % or equal to or greater than about 86 % or equal to or greater than about 88 % or equal to or greater than about 90 % or equal to or greater than about 92 % or equal to or greater than about 94 % or equal to or greater than about 95 % of the gold or ruthenium or palladium or platinum in the catalyst may be atomically dispersed. For example, up to about 100 % or up to about 99 % or up to about 98 % or up to about 97 % or up to about 96 % of the gold or ruthenium or palladium or platinum in the catalyst may be atomically dispersed. For example, from about 80 % to about 100 % or from about 85 % to about 100 % or from about 90 % to about 100 % or from about 95 % to about 100 % or from about 95 % to about 98% of the gold or ruthenium or palladium or platinum in the catalyst may be atomically dispersed.

Equal to or greater than about 80 % of the gold in the catalyst may be atomically dispersed. For example, equal to or greater than about 82 % or equal to or greater than about 84 % or equal to or greater than about 85 % or equal to or greater than about 86 % or equal to or greater than about 88 % or equal to or greater than about 90 % or equal to or greater than about 92 % or equal to or greater than about 94 % or equal to or greater than about 95 % of the gold in the catalyst may be atomically dispersed. For example, up to about 100 % or up to about 99 % or up to about 98 % or up to about 97 % or up to about 96 % of the gold in the catalyst may be atomically dispersed. For example, from about 80 % to about 100 % or from about 85 % to about 100 % or from about 90 % to about 100 % or from about 95 % to about 100 % or from about 95 % to about 98% of the gold in the catalyst may be atomically dispersed.

Equal to or less than about 10 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of dimers and sub-nanometre particles. For example, equal to or less than about 8 % or equal to or less than about 6 % or equal to or less than about 5 % or equal to or less than about 4 % or equal to or less than about 2 % or equal to or less than about 1 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of dimers and sub-nanometre particles. For example 0 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of dimers and sub-nanometre particles. For example from 0 % to about 10 % or from 0 % to about 5 % or from about 1 % to about 5 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of dimers and sub-nanometre particles.

Equal to or less than about 10 % of the gold in the catalyst may exist in the form of dimers and sub-nanometre particles. For example, equal to or less than about 8 % or equal to or less than about 6 % or equal to or less than about 5 % or equal to or less than about 4 % or equal to or less than about 2 % or equal to or less than about 1 % of the gold in the catalyst may exist in the form of dimers and sub-nanometre particles. For example 0 % of the gold in the catalyst may exist in the form of dimers and sub-nanometre particles. For example from 0 % to about 10 % or from 0 % to about 5 % or from about 1 % to about 5 % of the gold in the catalyst may exist in the form of dimers and sub-nanometre particles.

Equal to or less than about 10 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of nanoparticles. For example, equal to or less than about 8 % or equal to or less than about 6 % or equal to or less than about 5 % or equal to or less than about 4 % or equal to or less than about 2 % or equal to or less than about 1 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of nanoparticles. For example 0 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of nanoparticles. For example from 0 % to about 10 % or from 0 % to about 5 % or from about 1 % to about 5 % of the gold or ruthenium or palladium or platinum in the catalyst may exist in the form of nanoparticles. These values may correspond to the % of gold in the Au(0) or Ru(0) or Pd(0) or Pt(0) oxidation state.

Equal to or less than about 10 % of the gold in the catalyst may exist in the form of nanoparticles. For example, equal to or less than about 8 % or equal to or less than about 6 % or equal to or less than about 5 % or equal to or less than about 4 % or equal to or less than about 2 % or equal to or less than about 1 % of the gold in the catalyst may exist in the form of nanoparticles. For example 0 % of the gold in the catalyst may exist in the form of nanoparticles. For example from 0 % to about 10 % or from 0 % to about 5 % or from about 1 % to about 5 % of the gold in the catalyst may exist in the form of nanoparticles. These values may correspond to the % of gold in the Au(0) oxidation state.

Any nanoparticles present in the catalyst may, for example, have an average size ranging from about 1 nm to about 100 nm, for example from about 2 nm to about 50 mn. For example, any nanoparticles present in the catalyst may range from about 15 nm to about 30 nm, for example from about 18 nm to about 24 nm. This is measured using the Scherrer equation as described in the examples below.

The quantity of cationic gold or cationic ruthenium or cationic palladium or cationic platinum species in each oxidation state can be identified by X-Ray Absorption Spectroscopy (XAS) in the X-Ray Absorption Near-Edge Structure (XANES) region as described in the examples below. The quantity of cationic gold species in each oxidation state can be identified by X-Ray Absorption Spectroscopy (XAS) in the X-Ray Absorption Near-Edge Structure (XANES) region as described in the examples below.

In certain embodiments, the majority of the gold in the catalyst is in the Au(l) oxidation state.

In certain embodiments, the majority of the ruthenium in the catalyst is in the Ru(lll) oxidation state.

In certain embodiments, the majority of the palladium in the catalyst is in the Pd(ll) oxidation state.

In certain embodiments, the majority of the platinum in the catalyst is in the Pt(ll) oxidation state.

Equal to or greater than about 58 % of the gold in the catalyst described herein may exist in the Au(l) oxidation state. For example, equal to or greater than about 60 % or equal to or greater than about 65 % or equal to or greater than about 70 % or equal to or greater than about 75 % of the gold in the catalyst may exist in the Au(l) oxidation state. For example up to about 100 % or up to about 95 % or up to about 90 % or up to about 85 % or up to about 80 % of the gold in the catalyst may exist in the Au(l) oxidation state. For example from about 58 % to about 100 % or from about 60 % to about 95 % or from about 65 % to about 90 % or from about 70 % to about 85 % or from about 70 % to about 80 % or from about 72 % to about 78 % or from about 75 % to about 78 % or from about 75 % to about 80 % of the gold in the catalyst may exist in the Au(l) oxidation state.

Equal to or greater than about 60 % of the ruthenium in the catalyst described herein may exist in the Ru(lll) oxidation state. For example, equal to or greater than about 65 % or equal to or greater than about 70 % or equal to or greater than about 75 % or equal to or greater than about 80 % of the ruthenium in the catalyst may exist in the Ru(lll) oxidation state. For example up to about 100 % or up to about 95 % or up to about 90 % or up to about 85 % of the ruthenium in the catalyst may exist in the Ru(lll) oxidation state. For example from about 60 % to about 100 % or from about 70 % to about 95 % or from about 80 % to about 90 % of the ruthenium in the catalyst may exist in the Ru(lll) oxidation state. Equal to or greater than about 60 % of the palladium in the catalyst described herein may exist in the Pd(ll) oxidation state. For example, equal to or greater than about 65 % or equal to or greater than about 70 % or equal to or greater than about 75 % or equal to or greater than about 80 % of the palladium in the catalyst may exist in the Pd(ll) oxidation state. For example up to about 100 % or up to about 95 % or up to about 90 % or up to about 85 % of the palladium in the catalyst may exist in the Pd(ll) oxidation state. For example from about 60 % to about 100 % or from about 70 % to about 95 % or from about 80 % to about 90 % of the palladium in the catalyst may exist in the Pd(ll) oxidation state.

Equal to or greater than about 60 % of the platinum in the catalyst described herein may exist in the Pt(ll) oxidation state. For example, equal to or greater than about 65 % or equal to or greater than about 70 % or equal to or greater than about 75 % or equal to or greater than about 80 % of the platinum in the catalyst may exist in the Pt(ll) oxidation state. For example up to about 100 % or up to about 95 % or up to about 90 % or up to about 85 % of the platinum in the catalyst may exist in the Pt(ll) oxidation state. For example from about 60 % to about 100 % or from about 70 % to about 95 % or from about 80 % to about 90 % of the platinum in the catalyst may exist in the Pt(ll) oxidation state.

Equal to or less than about 42 % of the gold in the catalyst described herein may exist in the Au(lll) oxidation state. For example equal to or less than about 40 % or equal to or less than about 35 % or equal to or less than about 30 % or equal to or less than about 25 % of the gold in the catalyst may exist in the Au(lll) oxidation state. For example equal to or greater than about 0 % or equal to or greater than about 1 % or equal to or greater than about 2 % or equal to or greater than about 5 % or equal to or greater than about 10 % or equal to or greater than about 15 % or equal to or greater than about 20 % of gold in the catalyst may exist in the Au(ll l) oxidation state. For example from 0 % to about 42 % or from about 2 % to about 40 % or from about 5 % to about 35 % or from about 10 % to about 30 % or from about 15 % to about 25 % or from about 20 % to about 25 % of the gold in the catalyst may exist in the Au(lll) oxidation state.

The ratio of Au(l) : Au(lll) in the catalyst may, for example, be equal to or greater than about 1. For example, the ratio of Au(l) : Au(lll) in the catalyst may be equal to or greater than about 1.5 or equal to or greater than about 2 or equal to or greater than about 2.5 or equal to or greater than about 3. For example, the ratio of Au(l) : Au(lll) in the catalyst may be up to about 5.

All of the gold (i.e. 100 %) in the catalyst may, for example, exist in the Au(l) or Au(lll) oxidation state. Alternatively, some of the gold in the catalyst may, for example, exist in other oxidation states (such as Au(0)). For example, up to about 10 % or up to about 8 % or up to about 6 % or up to about 5 % or up to about 4 % or up to about 2 % of the gold in the catalyst exists in one or more oxidations states different to Au(l) and Au(lll) (for example Au(0) oxidation state). Equal to or less than about 10 % or equal to or less than about 8 % or equal to or less than about 6 % or equal to or less than about 5 % or equal to or less than about 4 % or equal to or less than about 2 % of the gold in the catalyst may exist in the Au(0) oxidation state.

Any value within the % ranges disclosed herein may be selected, provided the total % when considering all components totals 100 %.

Elemental gold (Au(0)) may be identified by the presence of 2Q reflections at 38, 44, 64 and 77° of an X-Ray Diffraction pattern.

Elemental ruthenium (Ru(0)) may be identified by the presence of 2Q reflections at 42.2 and 44° of an X-Ray Diffraction pattern.

Elemental palladium (Pd(0)) may be identified by the presence of the principal 2Q reflection at 40° of an X-Ray Diffraction pattern.

Elemental platinum (Pt(0)) may be identified by the presence of 2Q reflections at 42.9, 46.4, 67.9, 81.8 and 86.2° of an X-Ray Diffraction pattern.

It is thought that the use of a solvent as described herein improves the dispersion of the gold or ruthenium or palladium or platinum species in the catalyst and therefore respectively reduces the formation of Au or Ru or Pd or Pt nanoparticles present in the catalyst. It is thought that the use of a solvent as described herein improves the dispersion of the gold species in the catalyst and therefore reduces the formation of Au nanoparticles present in the catalyst. Therefore, the diffraction peaks corresponding to metallic Au or metallic Ru or metallic Pd or metallic Pt may be reduced compared to catalysts made with other solvents, particularly aqueous solvents such as water. Therefore, the diffraction peaks corresponding to metallic Au (2Q reflections at 38, 44, 64 and 77° of an X-Ray Diffraction pattern) are reduced compared to catalysts made with other solvents, particularly aqueous solvents such as water. Therefore, the diffraction peaks corresponding to metallic Ru (2Q reflections at 42.2 and 44° of an X-Ray Diffraction pattern) may be reduced compared to catalysts made with other solvents, particularly aqueous solvents such as water. Therefore, the diffraction peaks corresponding to metallic Pd (2Q reflection at 40° of an X-Ray Diffraction pattern) may be reduced compared to catalysts made with other solvents, particularly aqueous solvents such as water. Therefore, the diffraction peaks corresponding to metallic Pt (2Q reflections at 42.9, 46.4, 67.9, 81.8 and 86.2° of an X-Ray Diffraction pattern) may be reduced compared to catalysts made with other solvents, particularly aqueous solvents such as water. Therefore, in certain embodiments, the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at one or both of 42.2 and 44°. Therefore, in certain embodiments, the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at 40°. Therefore, in certain embodiments, the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at one or more of 42.9, 46.4, 67.9, 81.8 and 86.2°. Therefore, in certain embodiments, the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at one or more of 38, 44, 64 and 77°. In certain embodiments, the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at at least 64 and 77°.

The catalysts described herein are thought to have an improved dispersion and consequently an improved activity compared to catalysts made using other solvents, particularly aqueous solvents such as water. Therefore, the catalyst may provide a steady state acetylene conversion equal to or greater than about 3 %. For example, the catalyst may provide a steady state acetylene conversion equal to or greater than about 5 % or equal to or greater than about 10 % or equal to or greater than about 15 % or equal to or greater than about 18 % or equal to or greater than about 20 %. The catalyst may, for example, provide a steady state acetylene conversion up to about 30 % or up to about 25 %. The catalyst may, for example, provide a steady state acetylene conversion ranging from about 3 % to about 30 %, for example from about 18 % to about 25 % or from about 19 % to about 25 % or from about 20 % to about 25 %. The steady state acetylene conversion refers to the maximum % conversion reached when using the catalyst in a method of acetylene hydrochlorination as described in the examples below.

The catalysts described herein may, for example, have a gold or ruthenium or palladium or platinum loading level from about 0.01 to about 2 % based on the total weight of the catalyst. For example, the catalysts described herein may have a gold or ruthenium or palladium or platinum loading level of from about 0.1 wt% to about 1.5 wt% or from about 0.5 wt% to about 1 wt%.

The catalysts described herein may, for example, have a gold loading level from about 0.01 to about 2 % based on the total weight of the catalyst. For example, the catalysts described herein may have a gold loading level of from about 0.1 wt% to about 1.5 wt% or from about 0.5 wt% to about 1 wt%.

Use of the Catalyst

The catalysts described herein may, for example, be used as catalysts or may be used in a chemical process. The catalysts described herein may, for example, be used in methods for making vinyl chloride, particularly in methods for making vinyl chloride by hydrochlorination of acetylene.

Any suitable conditions for acetylene hydrochlorination could be used and may be selected by persons of ordinary skill in the art using common general knowledge. The conditions may, for example, be in accordance with the conditions specified in G. Malta et al., Science, 2017, 355, pages 1399-1403.

The catalysts described herein may also be used in hydrochlorination of other alkynes or substituted alkynes (for example alkynes having from 2 to 20 carbon atoms, for example from 2 to 10 carbon atoms or from 2 to 8 carbon atoms or from 2 to 6 carbon atoms). The catalysts described herein may also be useful in other reactions involving hydrochloric acid and/or chlorine (e.g. CI2).

The following numbered paragraphs define particular embodiments of the present invention: 1. A method for making a catalyst, the method comprising combining a gold precursor, a solvent, and a support material, wherein the solvent comprises an organic solvent and wherein the solvent does not comprise organic aqua regia.

2. The method of paragraph 1 , wherein the combining comprises forming a solution of the gold precursor in the solvent, and combining the solution with the support material.

3. The method of paragraph 1 or 2, wherein the method further comprises drying the product of the step of combining the gold precursor, solvent and support material.

4. The method of any preceding paragraph, wherein the gold precursor is selected from elemental gold (Au), chloroauric acid (HAuCU) such as chloroauric trihydrate and/or tetrahydrate, gold (III) chloride (AuCh), gold (I) chloride (AICI), gold acetate and combinations of one or more thereof.

5. The method of any preceding paragraph, wherein the solvent has an ET(30) polarity equal to or less than about 62, for example equal to or less than about 60, for example equal to or less than about 55, for example equal to or less than about 50.

6. The method of any preceding paragraph, wherein the solvent has a boiling point equal to or less than about 120°C.

7. The method of any preceding paragraph, wherein the organic solvent is selected from the group consisting of alcohols, ketones, esters, ethers, sulphoxides, nitriles, amides and combinations of one or more thereof.

8. The method of any preceding paragraph, wherein the solvent does not comprise nitric acid and/or does not comprise hydrochloric acid and/or a combination of nitric acid and hydrochloric acid.

9. The method of any preceding paragraph, wherein the method does not comprise adding a sulphur-containing ligand to the gold precursor, solvent and support material.

10. The method of any preceding paragraph, wherein the solvent does not comprise a strong mineral acid. 11. The method of any preceding paragraph, wherein the solvent comprises equal to or less than about 50 vol% water, for example equal to or less than about 10 vol% water, for example equal to or less than about 5 vol% water.

12. The method of any preceding paragraph, wherein the solvent does not comprise water.

13. The method of any preceding paragraph, wherein the solvent has a pH equal to or greater than about 5 or equal to or greater than about 6.

14. The method of any preceding paragraph, wherein the support material comprises carbon such as activated carbon.

15. The method of paragraph 3, wherein the drying occurs at a temperature above the boiling point of the solvent.

16. The method of paragraph 3 or 15, wherein the drying occurs at a temperature up to about 10°C higher than the boiling point of the solvent.

17. The method of paragraph 3, 15 or 16, wherein the drying occurs at a temperature equal to or less than about 120°C, for example equal to or less than about 110°C, for example equal to or less than about 100°C, for example equal to or less than about 90°C.

18. A catalyst comprising atomically dispersed cationic gold species and a support material, wherein:

equal to or greater than about 58% of the gold exists in the Au(l) oxidation state; and/or

equal to or less than about 42% of the gold exists in the Au(lll) oxidation state; and/or

the catalyst provides a steady state acetylene conversion greater than about 18%; and/or

equal to or greater than about 80 % of the gold exists is atomically dispersed.

19. The catalyst of paragraph 18, wherein:

equal to or less than about 10 % of the gold exists in the form of nanoparticles; and/or equal to or greater than about 80 % of the gold exists is atomically dispersed; and/or

equal to or less than about 10 % of the gold exists in the form of dimers and sub nanometer clusters; and/or

the catalyst has an X-Ray Diffraction pattern that does not have a 2Q reflection at one or more of 38, 44, 64 and 77°.

20. The catalyst of paragraph 18 or 19, wherein the catalyst provides a steady state acetylene conversion of greater than about 3%, for example equal to or greater than about 18%.

21. A catalyst obtainable by and/or obtained by the method of any of paragraphs 1 to 17. 22. The catalyst of paragraph 21 , wherein the catalyst has one or more of the features specified in paragraphs 18 to 20.

23. Use of a catalyst of any one of paragraphs 18 to 22 in a method of making vinyl chloride.

24. The use of paragraph 23, wherein the method of making vinyl chloride comprises hydrochlorination of acetylene.

EXAMPLES

Example 1

Methods Catalyst Preparation

All carbon-supported gold catalysts were prepared via a wet impregnation method described in G. Malta et ai, Science, 2017, 355, pages 1399-1403, except that different solvents were used. Activated carbon (Norit® ROX 0.8) was initially ground to obtain a powder (150 - 200 mesh). The gold precursor, HAuCL-3H ₂ 0 (Alfa Aesar, 20 mg, assay 49%) was dissolved in the required solvent (2.7 ml). The gold precursor solution was added drop-wise, with stirring, to the activated carbon (0.99 g) in order to obtain a catalyst with a final metal loading of 1 wt.%. The resulting powder was dried at a boiling point of the solvent used, for 16 h under a flow of N2. The catalysts prepared using different solvents were denoted as Au/C-(solvents) and, wherever possible, solvents commercially available as“extra-dry solvents” sealed in nitrogen were used.

The solvents used, their ET(30) polarities, boiling points and related drying temperatures are shown in Table 1 below.

Table 1.

Catalyst Testing

Catalysts were tested for acetylene hydrochlorination in a fixed-bed polyimide (Kapton) microreactor (O.D. 6 , length 20 cm) contained within a heating block powered by two heating cartridges inside the block. The temperature was controlled by a Eurotherm controller with a type K thermocouple positioned in the centre of the heater block. Cakh/Ar (5.01% balanced in Ar, BOC) and HCI/Ar (5.05% balanced in Ar, BOC) gases were dried, using moisture traps, prior to introduction to the reactor. In all cases, the reactor was purged with Ar (99.99% BIP, Air Products) prior to admitting the hydrochlorination reaction mixture. The reactor was heated to 200 °C at a ramp rate of 5 °C min ^-1 and held at this temperature for 30 min, all under a flow of Ar (50 ml min ^-1 ). The reaction gas mixture of Cahh/Ar (23.56 ml min ^-1 ), HCI/Ar (23.76 ml min ^-1 ) and additional Ar (2.70 ml min ^-1 ) was introduced into the heated reactor chamber containing catalyst (90 mg) at a total gas hourly space velocity (GHSV) of -17,600 h ¹ , keeping the C2H2: HCI ratio at a constant value of 1 : 1.02. Typical time on stream experiments were conducted for 240 min (4 h). The gas phase products were analysed on-line using a Varian 450 GC equipped with a flame ionisation detector (FID). Chromatographic separation and identification of the products was carried out using a Porapak N packed column (6 ft ^c 1/8" stainless steel). 100 % C2H2 conversion gives a VCM productivity of 35.33 mol kg _cat ¹ h ¹ under the reaction conditions used. The experimental error in acetylene conversion was ±1 % for repeat tests.

Catalyst Characterization Powder X-ray diffraction (XRD) spectra were acquired using an X’Pert Pro PAN Analytical powder diffractometer employing a Cu K _a radiation source operating at 40 keV and 40 mA. The spectra were analysed using X’Pert High Score Plus software. The mean crystallite size of the metallic gold nanoparticles, where possible, were determined using the Scherrer equation assuming a spherical particle shape and a K factor of 0.89 at the reflection arising from the set of (111) Au planes, at 2Q = 38°.

X-ray absorption structure (XAS) spectra for all the Au/C samples were recorded at the Au l_3 absorption edge, in transmission mode, at the B18 beamline of Diamond Light Source, Harwell, UK. The measurements were performed using a QEXAFS set-up with a fast-scanning Si (111) double crystal monochromator. The Demeter software package (Athena and Artemis) was used for XAS data analysis of the Au/C absorption spectra in comparison to standards relative to a Au foil.

Materials for examination by scanning transmission electron microscopy (STEM) were dry dispersed onto a holey carbon TEM grid. These supported fragments were examined using BF- and HAADF-STEM imaging modes in an aberration corrected JEOL ARM- 200CF scanning transmission electron microscope operating at 200kV. This microscope was also equipped with a Centurio silicon drift detector (SDD) system for X-ray energy dispersive spectroscopy (XEDS) analysis.

Results

It has previously been reported that the preparation of Au/C catalysts via wet impregnation of HAuCL from aqueous solution results in large Au nanoparticles being present in the catalyst. These catalysts have little to no activity towards acetylene hydrochlorination under these dilute reaction conditions (see Liu et al., Catal. Sci. Technol., 2016, 6, pages 5144-5153).

1wt% Au/C catalysts were prepared by the method described above without the need for strongly oxidising solvents or the formation of stable complexes with sulfur containing ligands.

Steady state acetylene hydrochlorination activity was determined at GHSV = 17,600 IT ¹ and is reported in Figure 1 a for catalysts prepared with a series of solvents such as Ci - C ₄ alcohols. As the chain length of the alcohol used in the preparation increased, and consequently as the polarity of the solvent decreased, the acetylene hydrochlorination activity of the catalysts increased, from 3 % conversion for catalysts prepared in aqueous solvents to a value of 20 % conversion for samples prepared in C ₄ alcohols. Ketones such as acetone and 2-butanone, in addition to ethers such as tetrahydrofuran (THF), ethyl acetate and diethyl ether, were also tested to investigate the effect of decreasing the polarity further, resulting in a slight increase in conversion to 23 %. A catalyst prepared by the same method described above but using aqua regia solvent prepared Au/C catalyst gave a steady state conversion of 18 %, meaning that the catalysts prepared by simple wet impregnation of HAuCL from low polarity, easy to handle, solvents such as acetone, 2-butanol and THF performed better than the catalyst prepared in highly acidic oxidising conditions. All catalysts tested displayed a high selectivity to vinyl chloride monomer (>99 %).

The relative plateau of activity, when decreasing the polarity of the impregnation solvents, occurs at around 20-24 % and is likely to represent a practical limit of the dispersion that can be achieved by the Au-chloride species. X-ray diffraction patterns, reported in Figure 1 b, were recorded for samples prepared with a range of solvent polarities. In the sample prepared by wet impregnation from aqueous solution, clear reflections can be seen at 2Q - 38, 44, 64 and 77° which correspond to the face-centred cubic structure of metallic Au and, using the Schemer equation, corresponds to an average crystallite size of 20 nm. These features are present in the catalyst samples prepared with high polarity solvents, with reflections indicating average nanoparticle sizes ranging from 18-24 nm. These reflections can be seen to gradually decrease in intensity as the polarity of the solvent decreases, indicating a higher dispersion of the Au in the catalysts, corresponding to increased activity. The samples with the highest activities show very weak or un-detectable diffraction peaks corresponding to metallic Au, indicating high dispersions of cationic Au and supporting the premise that Au nanoparticles are not the active species for this reaction.

As the solvents used are not strongly acidic or oxidising, the reason for the high activity of the catalysts prepared with low polarity organic solvents could arise from (i) the hydrophilic/hydrophobic nature of the solvents, providing increased wetting of the carbon support materials which leads to higher dispersions, (ii) the ability to use lower drying temperatures, thus preventing Au agglomeration and (iii) the complete absence of water in the catalyst preparation. To probe this assertion further we investigated the use of low polarity solvents with high boiling points such as dimethylformamide (DMF), dimethyl sulphoxide (DMSO) and cyclohexanone. Table 2 reports the polarity, boiling points and drying temperatures used to produce these catalysts along with the acetylene conversion values. Table 2.

Test Conditions: 90 mg catalyst, 23.5 ml_ mirr ¹ C2H2, 23.7 ml_ mirr ¹ HCI and 2.7 ml_ min ¹ Ar, 200 °C.

While all the catalysts prepared with a high boiling point (>120 °C) solvents performed better than the catalyst prepared in aqueous solution, they were not as active as the samples prepared with low boiling point solvents (<120 °C) suggesting that the drying temperature is also a parameter effecting the performance of the catalysts. XRD analysis

(Figure 6) shows that the catalysts prepared at high drying temperatures contained Au nanoparticles, which is consistent with their lower activity. To probe if drying temperature was the only variable determining high activity and dispersion, a catalyst was prepared with acetone and dried at 140 °C for 16 h. As reported in Table 2, this catalyst showed identical activity to the sample prepared with acetone and dried at 40 °C, which demonstrates that effective catalysts can be prepared with low polarity solvents and low drying temperatures, but that these same catalysts can still be stable and just as active even at higher drying temperatures. This suggests that it is the increased wettability of the impregnation solution on the carbon support coupled with mild drying conditions that effectively anchors single highly dispersed Au species, rather than speciation being solely dictated by the drying temperature.

We further investigated the effect of the presence of water on the preparation of catalysts using as purchased extra dry acetone without any further treatment. Adding increasing amounts of water (5-50 vol%) to the acetone resulted in a decrease in activity of the as- prepared catalyst as shown in Figure 2a, until at 50 vol% the activity resembled that of samples prepared in aqueous solution. This measured reduction in activity correlated well with the development of characteristic reflections from metallic Au in the recorded XRD patterns, Figure 2b. This confirms the negative impact of the presence of water on the preparation of highly dispersed Au catalysts, in the absence of strong oxidising/acidic agents or ligands, to stabilise the supported Au in high oxidation states.

A time-on-line study was performed to compare the activity of the low polarity Au/C- Acetone catalyst with that of the acidic Au/C -aqua regia material and high polarity Au/C- H2O catalyst. Figure 3 shows the high stability of the Au/C-Acetone catalyst under reaction conditions, with a small (3 %) increase in conversion in the first 100 min, indicating a possible minor change in the Au oxidation state and a minimal induction period, followed by a further 140 min of steady conversion. The Au/C -aqua regia catalyst by comparison undergoes a pronounced induction period due to changes in Au oxidation state which have been previously studied by in situ X AS, resulting in a 15 % difference in conversion over the same timeframe. The oxidising aqua regia solvent therefore resulted in a catalyst with a lower final conversion to that of the more benign acetone- prepared catalyst and is highly suggestive that the likely different functionality of the carbon supports can play a key role in determining the induction periods of these catalysts through either stronger Au anchoring or facilitating more facile changes in oxidation state.

Further characterisation of this 1 % Au/C-Acetone catalyst by high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) revealed the Au speciation to be predominatly atomically dispersed Au species as well as some occasional dimeric Au species and sub nano-meter clusters, with no evidence at all of larger Au crystallites. A representative image is shown in Figure 4a.

To further probe the speciation of the Au in the catalyst we conducted X-ray absorption spectroscopy (XAS) at the Au l_3-edge (11.92 keV). The X-ray absorption spectra at the Au l_3-edge of the fresh Au/C-Acetone catalyst and after reaction for 5 h were recorded, in addition to that for the Au/C-aqua regia catalyst, and analysed in the X-ray absorption near-edge structure (XANES) region. Analysis of the normalised white line intesity corresponding to the Au 2p _3/2 5d primary transition can be used as a direct probe of the 5d occupancy of the Au species present in the catalyst. Through comparison with standards for Au(lll) (- white line intensity, 1.1) and Au(l) (- white line intensity, 0.6) previously reported in literature (see Chang ei al., RSC Adv. , 2014, 5, pages 6912-6918 and Pantelouris et ai, JACS, 1995, 117, pages 1 1749-11753), it is possible to quantitatively determine the nature of the cationic Au species present in the catalysts. Analysis of the XANES region of the three Au/C catalysts intially reveals signficantly different post-edge features in comparison to a metallic Au foil, as reported in Figure 4b. This supports the XRD and STEM analysis that there are no extended metallic Au structures present in the fresh catalysts prepared with acetone or aqua regia. The normalised white line height of the fresh samples prepared with acetone and aqua regia suggest that both catalysts are a mixture of Au(l) and Au(lll) species, with the acetone catalyst being slightly more Au(l) rich than the comparable samples prepared using aqua regia, based on a lower normalised white line height intensity ( ca . 0.66 for Au/C-Acetone and ca. 0.78 for Au/C -aqua regia). Three different Au standards were used to perform a linear combination fitting (LCF) analysis of the Au l_3-edge XANES: Au(lll) (KAuCL/[AuCh] ^_ ), Au(l) ([AuCL]-), and a Au-foil standard spectra, as is shown in Figure 4c. The LCF confirms the cationic nature of the Au in the acetone derived catalyst with the Au predominantly existing in the Au(l) oxidation state (77%). This is similar in nature to the catalyst prepared using aqua regia albeit with a different distribution of Au(l) - (57%) and Au(lll) - (43%).

After 5 h of use, a small contribution from Au(0) could be detected in the Au/C-Acetone catalyst, indicating some instability of the cationic Au species. The reduction of Au species may be responsible for the deactivation of the catalysts. The stability observed in the acetylene hydrochlorination tests suggests that agglomeration takes place during the heating ramp to reaction temperatures and not actually during the reaction itself. Extended X-ray absorption fine structure (EXAFS) data for the Au/C-Acetone and Au/C- aqua regia catalysts (Figure 4d) indicated a lack of long-range order and no characteristic Au-Au distances, when compared to the Au foil standard, for both of these catalysts, in agreement with the X-ray diffraction and the HAADF-STEM analysis. An increase in intensity of the Fourier transform of the used catalysts at distances corresponding to those of the Au foil was observed in the used catalysts consistent with the LCF analysis.

To determine the stability of the Au/C-Acetone catalyst, a prolonged reaction was performed. After 4 h of reaction, the catalyst was cooled to room temperature under a flow of Ar, left sealed for 16 h, heated under an Ar flow and then tested under reaction conditions for a further 3 h. The same test was performed with the Au/C-aqua regia material for comparison. This test, illustrated in Figure 5, shows the good stability of the Au/C-Acetone catalyst, maintaining a conversion between 19-20 % for over 5 h, indicating that after the first 100 min of reaction the Au oxidation states and dispersion remained relatively stable. Figure 7 shows the XRD pattern of the Au/C-Acetone catalyst after 7 h of reaction, compared with that of the fresh material and the catalyst used for 4 h. The characteristic reflections of Au nanoparticles increased slightly in size after 7 h of reaction suggesting the slow sintering of the catalyst at extended reaction times. Furthermore, due to the lack of catalyst deactivation it is likely that this Au(0) forms during the heat up or initial stages of the reaction before stabilising. It worth noting that weak reflections from NaCI could also be observed in the XRD patterns of the catalysts especially when synthesized with ultra-dry solvents. This was attributed to the carbon support materials containing NaCI which could easily recrystallize in the ultra-dry organic solvents, but in aqueous solvents it can be readily dissolved and get well dispersed over the catalyst.

In conclusion we show that it is possible to prepare effective Au/C acetylene hydrochlorination catalysts consisting of atomically dispersed cationic Au species by a simple wet impregnation method, using low polarity solvents with low boiling points rather than the aggressive acidic and oxidising solvents typically used. These catalysts perform comparably to catalysts prepared with aqua regia in terms of activity and stability and have been shown to be structurally similar. Furthermore, there was no significant induction period associated with the rapid evolution of Au oxidation state often seen in catalysts prepared with highly oxidising solvents. This preparation method allows the facile preparation of single site Au catalysts with relatively high metal loadings compared to other reported systems and should allow the potential of these materials to be fully exploited by removing the need to deal with highly acidic waste during catalyst preparation.

Example 2

Methods

Catalyst Preparation

All carbon-supported catalysts were prepared via a wet impregnation method described in G. Malta et ai, Science, 2017, 355, pages 1399-1403, except that different solvents were used. Activated carbon (Norit® ROX 0.8) was initially ground to obtain a powder (150 - 200 mesh). The precursor was dissolved in acetone (2.7 ml). The precursor solution was added drop-wise, with stirring, to the activated carbon (0.99 g) in order to obtain a catalyst with a final metal loading of 1 wt.%. The resulting powder was dried at 5-10°C higher than the boiling point of the solvent used (acetone), for 16 h under a flow of N2. Wherever possible, solvents commercially available as“extra-dry solvents” sealed in nitrogen were used.

The gold precursor was HAUCI4.3H2O (Alfa Aesar, 20 mg, assay 49%).

The ruthenium precursor was Ru (III) acetylacetonate (Aldrich).

The palladium precursor was Pd (II) acetylacetonate (Aldrich).

The platinum precursor was Pt (II) 2,4-pentanedionate (Alfa Aesar).

Catalyst Testing

Catalysts were tested for acetylene hydrochlorination in a fixed-bed polyimide (Kapton) microreactor (O.D. 6 mm, length 20 cm) contained within a heating block powered by two heating cartridges inside the block. The temperature was controlled by a Eurotherm controller with a type K thermocouple positioned in the centre of the heater block. C2H2/Ar (5.01 % balanced in Ar, BOC) and HCI/Ar (5.05% balanced in Ar, BOC) gases were dried, using moisture traps, prior to introduction to the reactor. In all cases, the reactor was purged with Ar (99.99% BIP, Air Products) prior to admitting the hydrochlorination reaction mixture. The reactor was heated to 180 °C at a ramp rate of 5 °C min ¹ and held at this temperature for 30 min, all under a flow of Ar (50 ml min ¹ ). The reaction gas mixture of C2H2/Ar (23.56 ml min ¹ ), HCI/Ar (23.76 ml min ¹ ) and additional Ar (2.70 ml min ¹ ) was introduced into the heated reactor chamber containing catalyst (90 mg) at a total gas hourly space velocity (GHSV) of -17,600 h ¹ , keeping the C2H2: HCI ratio at a constant value of 1 : 1.02. Typical time on stream experiments were conducted for 240 min (4 h). The gas phase products were analysed on-line using a Varian 450 GC equipped with a flame ionisation detector (FID). Chromatographic separation and identification of the products was carried out using a Porapak N packed column (6 ft ^c 1/8" stainless steel). 100 % C2H2 conversion gives a VCM productivity of 35.33 mol kg _cat ¹ h ¹ under the reaction conditions used. The experimental error in acetylene conversion was ±1 % for repeat tests. Catalyst Characterisation

Powder X-ray diffraction (XRD) spectra were acquired using an X’Pert Pro PAN Analytical powder diffractometer employing a Cu K _a radiation source operating at 40 keV and 40 mA. The spectra were analysed using X’Pert High Score Plus software.

The Au/C, Ru/C, Pt/C and Pd/C catalysts were characterised via X-ray Absorption Spectroscopy (XAS) before reaction (Fresh) and after 240 min of reaction (Used). X-ray absorption spectroscopy (XAS) spectra for all the samples were recorded in transmission mode, at the B18 beamline of Diamond Light Source, Harwell, UK. The measurements were performed using a QEXAFS set-up with a fast-scanning Si (111) double crystal monochromator. The Demeter software package (Athena and Artemis) was used for XAS data analysis of the absorption spectra.

X-ray absorption spectroscopy (XAS) was conducted at the Au L3-edge (11.92 keV), Pt L3-edge, Pd K-edge, or Ru K-edge. The X-ray absorption spectra of the fresh catalysts, in addition to the corresponding metal precursors (HAuCL, Pt(acac)2, Pd(acac)2, and Ru(acac)3) and metal foils (Au(0), Pt(0), Pd(0), and Ru(0)), were recorded and analysed in the X-ray absorption near-edge structure (XANES) region and in the Extended X-Ray Absorption Fine Structure (EXAFS) region.

Materials for examination by scanning transmission electron microscopy (STEM) were dry dispersed onto a holey carbon TEM grid. These supported fragments were examined using BF- and HAADF-STEM imaging modes in an aberration corrected JEOL ARM- 200CF scanning transmission electron microscope operating at 200kV. This microscope was also equipped with a Centurio silicon drift detector (SDD) system for X-ray energy dispersive spectroscopy (XEDS) analysis. Results

It was found that the Au/C, Ru/C, Pt/C, and Pd/C catalysts were all active for the production of vinyl chloride monomer (see Figures 8 to 11). In all cases, the metal in the catalysts (Au, Ru, Pt and Pd) remained as cations and not in metallic form as predicted (see Figures 24 to 27, which lack 2Q reflections indicating the presence of Au(0) or Ru(0) or Pt(0) or Pd(0)). For the Ru, Pt and Pd catalysts, a replacement of the ligands surrounding the metal centre, from“acac” to“chlorine”, was observed. Overall, the catalysts are still single metal catalysts (see Figures 12 to 15). This was confirmed by Scanning Electron Transmission Microscopy (STEM). All catalysts comprised atomically dispersed metals (see Figures 16 to 23).

The XANES spectra of the catalysts show an overlap with the corresponding metal precursors but not with the metal foil. Since the metal precursors have an oxidation state of Ru(lll), Pd(ll), or Pt(ll) and the metal foils have an oxidation state of (0), the metals in the catalysts have an oxidation state of Ru(lll), Pd(ll), or Pt(ll) (see Figures 24 to 30).

The foregoing broadly describes certain embodiments of the present invention without limitation. Variations and modifications as will be readily apparent to those skilled in the art are intended to be within the scope of the present invention as defined in and by the appended claims.