This invention relates to methods of making catalyst precursors comprising one or more amorphous copper hydroxycarbonate compounds including Georgeite, and catalysts derived therefrom.

Georgeite is a hydrated copper hydroxy-carbonate. It is amorphous and therefore distinct from the crystalline malachite, Cu ₂ (C0 ₃ )(OH) ₂ or azurite, Cu ₃ (C0 ₃ )2(OH) ₂ materials.

Catalysts precursors for methanol synthesis, or water gas shift include copper-zinc oxide- alumina materials. These catalysts are typically prepared by co-precipitation using aqueous alkaline precipitants to de-stabilise aqueous acidic metal solutions of copper and zinc in the presence of a soluble aluminium source or a hydrated alumina. The co-precipitation in water is very fast and the co-precipitate slurries are aged under controlled pH conditions to ripen the resulting crystalline copper-zinc materials, comprising for example Rosasite,

(Cu,Zn) ₂ (C0 ₃ )(OH) ₂ , or Aurichalcite, (Zn,Cu) ₅ (C0 ₃ ) ₂ (OI-l) ₆ as well as crystalline copper and zinc carbonates. The aged materials are often dried and calcined to convert the copper and zinc compounds to the respective oxides and then shaped into pellets. The active catalysts may be then formed by reducing the copper to elemental form using a hydrogen-containing gas, which is often done in-situ. Alternatively the shaped calcined material may be subjected to a reduction step ex-situ and the surface of the resulting catalyst passivated to facilitate safe transport and storage.

Georgeite and azurite containing materials were prepared by Pollard et al in Appl. Catal. A. General, 85 (1992) pages 1-11. The method used to prepare the Georgeite samples is not suitable for preparing a catalyst because the quenching technique employed would result in unacceptably high sodium levels. The authors only tested the azurite materials.

The present invention uses a C0 ₂ -antisolvent technique to prepare the Georgeite-containing catalyst precursor, which can be isolated and dried. Conventional co-precipitation / ageing methods of catalyst preparation do not allow a dry amorphous material to be isolated.

US2010/0226845 describes Hopcalite-type catalysts for the oxidation of CO comprising phase- separated intimately mixed nanoparticles of copper and manganese oxide. The catalysts are prepared by contacting a solution of copper and manganese salts in a solvent with a supercritical antisolvent (such as C0 ₂ ) to precipitate a mixed metal oxide precursor, which may be calcined.

It has been found surprisingly that a catalyst precursor comprising Georgeite may be formed using this technique, optionally with other components, and converted to a catalyst with surprising activity. Accordingly, the present invention provides a method for making a dry particulate catalyst precursor comprising one or more amorphous metal hydroxycarbonates of Cu and Zn, including Georgeite and/or zincian Georgeite by (i) contacting a solution comprising a soluble copper compound and a soluble zinc compound, with a supercritical carbon dioxide antisolvent to precipitate the catalyst precursor, (ii) recovering the precipitate and (iii) drying the precipitate. The invention further provides an oxidic catalyst precursor comprising the dry particulate catalyst precursor in which at least a portion of the copper has been converted into copper oxide. The invention further provides a catalyst comprising the catalyst precursor, or the oxidic catalyst precursor, in which at least a portion of the copper has been reduced to elemental form.

By "Georgeite" we mean an amorphous copper hydroxycarbonate, which may be hydrated. Preferably the Georgeite is of formula Cu ₅ (C0 ₃ )3(OH)4.xH ₂ 0, where x = 0 to 6. The Georgeite content of the dry particulate catalyst precursor may be > 10% wt, preferably > 25% wt, more preferably > 50% wt, most preferably > 90% wt. In addition to Georgeite, other amorphous copper hydroxycarbonate materials maybe present. The catalyst precursor may also contain copper hydroxycarbonate precursors such as copper acetate. The presence of the different copper hydroxycarbonate materials and copper acetate may be determined by known methods such as FTIR. XRD may be used to determine the presence of crystalline materials.

Copper containing catalysts suffer from a problem that, upon heating above about 250°C, the copper atoms tend to sinter together giving a decrease in the copper surface area after a period of use at elevated temperature with consequent loss of activity. In order to alleviate this problem, the catalyst precursor further comprises zinc to stabilise the resulting copper material. The zinc may be present as a zinc compound. Such as a zinc oxide, a zinc carbonate or a zinc hydroxy-carbonate. Alternatively or in addition, at least a portion of the zinc replaces a portion of the copper in the Georgeite phase, thus forming a zinc-containing- or zincian-Georgeite. Thus Georgeite in the present invention includes zincian Georgeite, which may be of formula (Cui _-y Zn _y )5(C0 ₃ )3(OH)4.xH ₂ 0, in which x = 0 to 6 and y = 0.05 to about 0.3, preferably 0.1 to 0.3. Zinc hydroxycarbonate precursors such as zinc acetate may also be present in the dry catalyst precursor. Hence the catalyst precursor may comprise one or more zinc-free amorphous copper hydroxycarbonates including Georgeite and/or one or more zinc-containing amorphous copper hydroxycarbonates including zincian Georgeite as well as residual copper- hydroxycarbonate and zinc-hydroxycarbonate precursors such as copper acetate and zinc acetate.

In some instances it may be desirable to include a support material in the dry particulate catalyst precursor. The support material may comprise an oxide or hydrated metal oxide of alumina, silica, titania, zirconia, aluminosilicate or a mixture thereof, or a zeolite. Preferably the support material comprises an alumina or hydrated alumina. The alumina may be included directly, for example as boehmite or an alumina sol, or formed from aluminium compounds that decompose to the oxide or hydrated oxide during the preparation procedure. However it has been found that, surprisingly, stable catalysts may be prepared without the inclusion of a support material.

The catalyst precursor may further comprise one or more promoter compounds selected from oxides of Mg, Cr, Mn, V, Ti, Zr, Ta, Mo, W, Si and rare earths. Magnesium is a preferred promoter. However it has been found that, surprisingly, stable catalysts may be prepared without the inclusion of an oxidic promoter compound.

The catalyst precursor composition comprises, prior to calcination and/or reduction, a dry particulate composition comprising one or more amorphous metal hydroxycarbonates of Cu and Zn, including Georgeite and/or zincian Georgeite, optionally with alumina or hydrated alumina dispersed therein and optionally containing one or more Mg, Cr, Mn, V, Ti, Zr, Ta, Mo, W, Si or rare earths compounds, particularly Mg compounds, as a promoter. Residual copper and zinc hydroxycarbonate precursors may also be present. The dry particulate catalyst precursor preferably contains 20-70% wt copper, preferably 30-70% wt (expressed as CuO). The mole ratio ratio of Cu:Zn may be 1 : 1 or higher but is preferably is in the range 2: 1 to 3.5: 1 by weight for methanol synthesis catalysts and in the range 1.4:1 to 2.0:1 for water-gas shift catalysts. If a support is included, it may be present in an amount in the range 5 to 30% by weight, preferably 5 to 25% wt. If a promoter compound is included, it may be present in an amount in the range 0.1 - 10% wt, preferably 0.5 to 5% wt. As alkali metals are not used in the preferred preparative method, the alkali metal content of the catalyst precursor or oxidic catalyst precursor may be lower than conventional catalyst materials. Accordingly preferably, the catalyst precursor or oxidic catalyst precursor have an alkali metal content, especially a sodium or potassium content, of < 100ppm. Low alkali metal- containing catalysts offer improved selectivity in methanol synthesis and in the water-gas shift reaction.

The catalyst precursor may be prepared using the apparatus as described in the aforesaid US2010/0226845. The apparatus may therefore comprise: (i) a supply vessel in which the solution containing the soluble copper compound is placed, (ii) a precipitation vessel, which may be temperature controlled, to which the solution is pumped through a capillary supply line, and (iii) a supercritical C0 ₂ supply fed by a pump to the precipitation vessel. The capillary solution supply-line and supercritical C0 ₂ supply line are desirably arranged in the precipitation vessel such that the solution droplets, as they exit the capillary, are rapidly diffused into by the supercritical C0 ₂ , causing expansion and simultaneously reducing the solvent power to precipitate the Georgeite-containing material. It is convenient to include a filter within the precipitation vessel to collect the precipitated material. By de-pressurising the precipitation vessel, the precipitated catalyst precursor may be recovered as a powder.

The copper and zinc compounds may be any suitably soluble salt, such as the metal acetates, nitrates, sulphates or chlorides. Preferably both salts have the same anion. More preferably the metal acetates are used as this overcomes the problem of NOx emissions during subsequent processing.

The solvent may be any polar organic solvent, such as DMSO or DMF, but is preferably an alcoholic solution, especially an ethanol solution. Water is desirably included in the solution as it is believed to be important in the formation of the Georgeite phase. Water may be included up to a concentration of 20% vol, preferably 5-15% vol.

The precipitation is preferably performed at <60°C, more preferably <50°C, most preferably ≤45°C. The minimum temperature is desirably that at which a single phase is maintained at the pressure of the supercritical C0 ₂ and is preferably >10°C, more preferably >20°C, most preferably >30°C and especially >35°C. A particularly suitable temperature range to produce the amorphous copper hydroxycarbonate precursor material is 35-40°C. The catalyst precursor may be dried under air or an inert gas such as nitrogen at temperatures up to about 120°C. The dried particulate catalyst precursor comprises one or more amorphous metal hydroxycarbonates of Cu and Zn, including Georgeite and/or zincian Georgeite and residual unreacted metal compounds from the solution. The catalyst precursor may be calcined to convert at least a portion of the copper and zinc in the catalyst precursor to an oxide and form an oxidic catalyst precursor powder. The calcination may be effected at temperatures in an excess of 275°C and is suitably effected at temperatures in the range 300 to 500°C. The calcination may be performed in air or under an inert gas such as nitrogen.

The oxidic catalyst precursor powder may be shaped using conventional methods, for example into pellets. The shaped oxidic precursor may be provided to end-users for reduction in the vessel in which it is to be used to give an active copper catalyst in-situ, or a reduced and passivated catalyst may be provided, which offers faster, simpler activation.

Alternatively, the amorphous catalyst precursor containing one or more amorphous copper hydroxycarbonates may be subjected to a step of direct reduction to convert at least a portion of the copper directly to elemental form. The reduced powder material may then be passivated and pelleted to give the final catalyst. Reduction of the copper compounds may conveniently be achieved by exposing the catalyst precursor or oxidic catalyst precursor to a hydrogen- and/or carbon monoxide containing gas at atmospheric or elevated pressure. Reduction is preferably performed at the lowest temperature at which it will proceed. Thus conventional hydrogen reduction techniques may be used wherein a dilute hydrogen stream, e.g. 2% H ₂ in N ₂ is used and the catalyst precursor heated slowly until reduction commences at about 80°C. Reduction of oxidic precursors is sufficiently complete by 200°C or even 150°C.

Direct reduction of the amorphous catalyst precursor, may be performed with high

concentrations of hydrogen in the reducing gas stream for the entire reduction stage without the problems normally observed in the reduction of copper-oxide containing materials. In one embodiment therefore, reduction of catalyst precursors containing copper hydroxycarbonate materials is performed by exposing the dried catalyst precursor to hydrogen-containing gas streams comprising >50% vol hydrogen, more preferably >75% vol hydrogen, especially >90% vol hydrogen. If desired, substantially pure hydrogen may even be used.

Reduction is typically performed until no further water and carbon dioxide are evolved from the catalyst precursor. The reduction normally converts at least 50% of the reducible copper compounds to metal but is preferably continued until >95% of the reducible copper is converted to metal.

In the reduced state, because of the high surface area, the copper may rapidly and

exothermically react with oxygen and moisture present in the air and so is preferably passivated for safe storage, transportation and installation. Passivation may be performed using dilute oxygen and/or carbon dioxide or the catalyst precursor powder may be coated with an oxygen barrier material. Passivation may be achieved by using inert gas/air mixtures, such as nitrogen/air mixtures, whereby the air concentration is slowly increased over a period in order to generate a thin metal oxide layer on the copper surfaces. Typically oxygen is introduced using air at a rate sufficient to maintain the temperature of the catalyst precursor at between 10 and 100°C, preferably 10 and 50°C, especially 20-40°C during the passivation. For example the reduced material may be exposed to an inert gas, e.g. nitrogen, flow and air added at 0.1 % vol. This is carefully increased over a period of time to 0.5% vol oxygen, then 1 % vol, then 2% vol, 5% vol and so on until the oxygen content is that of air. Alternatively, reduced catalyst compositions may be passivated using a gas mixture comprising carbon dioxide and oxygen with a C0 ₂ :0 ₂ ratio > 2:1 in order to form a thin layer of a metal carbonate, e.g. a metal hydroxycarbonate, on the surface.

Shaping of the oxidic catalyst precursor powder or the directly reduced and passivated catalyst powder may be performed in a number of ways: (i) Pre-compaction and pelleting of the powders, such that the shaped units are pellets,

(ii) Combination of the powders with one or more binders, and optionally one or more further powder materials and tumbling to form spherical agglomerates or granules, (iii) Conversion of the powders into a slurry (preferably non-aqueous),

kneading/grinding in a pan mill and extrusion to form extrudates.

(iv) Conversion into a slurry as above, kneading/grinding in a pan mill and extrusion to give complex mouldings, such as monolithic structures or catalyst plates with or without secondary structure.

(v) Application of the powders to inert or likewise catalytically active supports by

means of wash-coating or similar processes.

In all processes, the use of binders and additives common in the art may be used.

Numerous other possibilities for further processing are also possible. Pre-compaction and pelleting of the powder is most suitable for preparing shaped units of the present invention. The pellet may be the conventional flat-ended cylindrical pellet. Cylindrical pellets for carbon oxide conversion processes suitably have a diameter in the range 3-10 mm and an aspect ratio (length / diameter) in the range 0.5-2.0. Alternatively, the shaped unit of the present invention may be in the form of rings or trilobes. In a preferred embodiment the shaped unit is in the form of a domed cylinder having two or more grooves running along its length. Alternatively, or in addition, the shaped units may have one or more through-holes extending there-through. Such highly domed cylindrical catalysts have improved packing and/or lower pressure drop than conventional non-fluted or non-holed shapes. The invention provides processes using the catalyst, in particular:

A. Methanol synthesis in which a gas mixture containing carbon monoxide, hydrogen and optionally carbon dioxide, is passed over the catalyst at a temperature in the range 200-320°C, a pressure in the range 20-250, especially 30-120, bar abs and a space velocity in the range 500-20000 h ^~ . The process can be on a once-through, or a recycle, basis and can involve cooling by indirect heat exchange surfaces in contact with the reacting gas, or by subdividing the catalyst bed and cooling the gas between the beds by injection of cooler gas or by indirect heat exchange. For this process the catalyst preferably contains copper, zinc oxide and optionally magnesia, with alumina.

B. Modified methanol synthesis in which the catalyst contains also free alumina of surface area 50-300 m ² g ^~ , so that the synthesis product is relatively rich in dimethyl ether. Temperatures, pressures and space velocities are similar to those for methanol synthesis but the synthesis gas contains hydrogen and carbon monoxide in a molar ratio of less than 2. C. Modified methanol synthesis in which the catalyst further contains an alkali metal at a level in the range 0.2 to 0.7% by weight, particularly potassium, added in a discrete step to the intimate mixture, so that the synthesis product contains higher alcohols (containing 2 to 5 carbon atoms), usually in addition to methanol. Process conditions are generally similar to those for B, but higher pressures and temperatures and lower space velocities in the stated ranges are preferred.

D. Low temperature shift reaction in which a gas containing carbon monoxide (preferably under 4% v/v on a dry basis) and steam (steam to total dry gas molar ratio typically in range 0.3 to 1.5) is passed over the catalyst in an adiabatic fixed bed at an outlet temperature in the range 200 to 300°C at a pressure in the range 15-50 bar abs. Usually the inlet gas is the product of "high temperature shift" in which the carbon monoxide content has been decreased by reaction over an iron-chromia catalyst at an outlet temperature in the range 400 to 500 °C, followed by cooling by indirect heat exchange. The outlet carbon monoxide content is typically in the range 0.1 to 1.0%, especially under 0.5% v/v on a dry basis.

E. Medium temperature shift in which the gas containing carbon monoxide and steam is fed at a pressure in the range 15-50 bar abs to the catalyst at an inlet temperature typically in the range 200 to 240°C although the inlet temperature may be as high as 280°C, and the outlet temperature is typically up to 300°C but may be as high as 360°C. These conditions are more severe than in D, such that the new catalyst is expected to be especially advantageous.

F. Low-medium temperature shift with heat exchange, in which the reaction in the catalyst bed occurs in contact with heat exchange surfaces. The coolant conveniently is water under such a pressure such that partial, or complete, boiling takes place. A suitable pressure is 15 to 50 bar abs and the resulting steam can be used, for example, to drive a turbine or to provide process steam for shift, or for an upstream stage in which the shift feed gas is generated. The water can be in tubes surrounded by catalyst or vice versa. Alternatively for alcohol synthesis reactions, instead of using a fixed bed catalyst, the catalyst may be suspended in a liquid. While in principle the particles obtained by the aforementioned techniques for obtaining a catalyst suitable for use in a fixed bed could also be used in suspension in a liquid, it is preferred to use the labile compounds as powder or in some small particle form agglomerated to an extent short of what is needed in a fixed bed process.

The invention will now be further described by reference to the following Examples and by reference to Figures 1 and 2. Example 1. Catalyst precursor preparation

Catalyst precursor materials were produced using supercritical C0 ₂ anti-solvent in a precipitation vessel fed by supercritical C0 ₂ and a solution of metal acetates. The apparatus used, as described in the aforesaid US2010/0226845, comprised: (i) a supply vessel in which the solution containing a solution of a soluble copper compound and a soluble zinc compound, (ii) a temperature-controlled precipitation vessel, to which the solution was pumped through a capillary supply line, and (iii) a supercritical C0 ₂ supply fed by a pump to the precipitation vessel. The capillary solution supply-line and supercritical C0 ₂ supply line were arranged in the precipitation vessel such that the solution droplets, as they exit the capillary, are rapidly diffused into by the supercritical C0 ₂ . The product was collected on a filter placed within the precipitation vessel. a) Sodium-containing product. A 1 .5L solution of copper acetate monohydrate (5 mgml ^"1 ) and zinc acetate dihydrate (2.15 mgml ^"1 ) dissolved in a 9:1 ethanol:water solution was prepared in a beaker. The raw materials used were as purchased form a standard supplier with typical sodium contents. The precipitation vessel was prepared by pressurising with C0 ₂ to 1 10bar and heated to a temperature of 40°C. A constant flow of C0 ₂ was maintained at 6.4kgh ^"1 and was held at this rate for the rest of the experiment. A 9:1 ethanol:water solution was then pumped into the vessel for 5 minutes followed by the CuZn precursor solution for 3 hours and then the ethanol:water solution for 20 minutes all at a rate of 6.4mlmin-1. Following this, the system was left with only C0 ₂ flowing for 1 hour. The system was then depressurised and the resulting precipitated powder, dried in an oven at 95°C for 5 hour and then calcined for 6 hours at 300°C. The dried product prior to calcination was identified by FTIR as amorphous zincian Georgeite. The sodium content was measured to be 361 ppm. b) Low-sodium product. A 1 .5L solution of copper acetate monohydrate (5 mgml ^"1 ) and zinc acetate dihydrate (2.15 mgml ^"1 ) dissolved in a 9:1 ethanol:water solution was prepared in a beaker. The raw materials used were the low sodium forms purchased from a standard supplier with a measured sodium content of 30ppm. The precipitation vessel was prepared by pressurising with C0 ₂ to 1 10bar and heated to a temperature of 40°C. A constant flow of C0 ₂ was maintained at 6.4kgh ^"1 and was held at this rate for the rest of the experiment. A 9: 1 ethanol:water solution was then pumped into the vessel for 5 minutes followed by the CuZn precursor solution for 3 hours and then the ethanol:water solution for 20 minutes all at a rate of 6.4mlmin ^"1 . Following this the system was left with only C0 ₂ flowing for 1 hour. The system was then depressurised and the resulting product collected, dried in an oven at 95°C for 5 hour and then calcined for 6 hours at 300°C. The dried product prior to calcination was identified by FTIR as amorphous zincian Georgeite. The sodium content was measured to be 66ppm. The addition of water co-solvent resulted in the formation of carbonic acid during precipitation of the metal salts, which is believed to aid the formation of the zinc-containing Georgeite at the target 2: 1 Cu/Zn ratio. The correct Cu/Zn ratio with a 100% yield showed that the addition of water co-solvent produced a more controllable and robust process than water-free precipitations.

Amorphous Georgeite materials formed by conventional co-precipitation are unstable, and readily convert during ageing/washing into malachite materials. In addition to high sodium levels, the copper hydroxycarbonate phases produced by co-precipitation have highly phase segregated Cu and Zn that on calcination can result in poor Cu dispersions. Analysis has shown that by using the C0 ₂ -antisolvent method, zincian Georgeite phase can be produced with a high dispersion of Cu and Zn. This is due to the minimal surface tension within the system facilitating high nucleation rates and no diffusion boundary. Further still, very low Na content can be achieved by C02-antisolvent precipitation without the need for a washing step. The principle source of Na is from the initial acetate salt, subsequently by treating the metal acetates, very low Na content of 66ppm can be obtained in the Georgeite precipitate.

Example 2. (Comparative)

Conventional co-precipitated catalysts comprising Malachite. Copper nitrate and zinc nitrate (260mgml ) solution (aqueous) held in a first vessel at 65°C. Sodium Carbonate (1.5M cone) held in a second vessel at 65°C. The solutions were pumped simultaneously into a precipitation vessel with overhead stirring and kept at 65°C. The pH was maintained at 6.5 ± 0.3. The precipitated slurry sample flowed over into an ageing vessel again held at 65°C. The aged precipitate was recovered, dried at 1 10°C for 16h and then calcined at 300°C for 6h.

Example 3. Catalyst testing - Methanol synthesis

The calcined catalyst precursors were reduced in 2% H2 in N2 at 10 bar (2 deg/min to 90 deg C, then 1 deg C/min to 135 deg C, then 0.5 deg C/min to 225 deg C, 1 h hold). The catalytic test was performed in laboratory apparatus with 6% CO / 9.2% C02 / 17.8% N2 in H2 process gas, at 25 bar and varying flow rates and temperature. The following temperatures were investigated: (i) 175 deg C for 12 h and (ii) 190 deg C for 18 h followed by heating to 250 deg C over 70 h before returning to 175 deg C.

The methanol synthesis activity, expressed as methanol conversion relative to comparative Example 2 at 175°C, vs time for the catalysts of Examples 1 and 2 are depicted in Figure 1. The C02-antisolvent materials have a 15-20% higher initial activity than the co-precipitated CuZn comparative material. In addition, the by-product formation by the C02-antisolvent materials was measured for all three samples and compared to the performance of the equivalent co-precipitated material. The most important by-product for the methanol reaction is ethanol and the amount generated for each catalyst is shown in the table below where it can be seen that the performance of the low sodium zincian Georgeite catalyst in particular gave reduced ethanol levels.

Example 4. Catalyst testing - Water-gas shift process

Testing for the low-temperature shift reaction was performed in laboratory apparatus using a single stream six bed flow reactor. A conventional Cu/Zn/alumina LTS catalyst was compared with the co-precipitated catalysts and the catalysts prepared by the C02 antisolvent method.

The calcined catalyst precursors were reduced under the same conditions as for methanol synthesis. The same reaction conditions of 220°C and 27.5 bar pressure were used for each catalyst. The reactant gas stream was as follows;

Nitrogen 25.0%vol

Hydrogen 55.0%vol

Carbon Dioxide 16.0%vol

Carbon monoxide 4.0%vol

The gas stream was saturated with water vapour such that the H ₂ 0 content in the wet gas was 50% vol.

The standard mass velocity used for testing was 75000 lh ^" kg ^"1 . In-line analysis was performed to measure CO conversion. Selectivity was determined by measuring the methanol content within the knockout pots downstream of the shift reactor. Relative activities were calculated by altering the flow for each catalyst bed in order to achieve 75% CO conversion. The total system flow was maintained by using a bypass line.

The CO conversions (%) vs time for the catalysts of Examples 1 and 2 are depicted in Figure 2. The initial CO conversion of the standard LTS catalyst was 88.84% and decreased, due to deactivation of the catalyst, by 10.5% over 108.7h. The die-off curve is comparable with that normally expected for a LTS catalyst. The activity of the Comparative Example 2 (co-precipitated catalyst) was the lowest of all the unsupported materials. The zincian-Georgeite derived material produced using the standard purity metal acetate salts had an improved activity. The catalyst derived from the low sodium zincian Georgeite precursor showed significantly higher CO conversion than any other material tested. In addition to this the material is significantly more stable over the reaction time period compared to the other unsupported materials and the alumina-containing standard.

The stability of the C0 ₂ -antisolvent prepared materials compared to the conventional alumina supported standard is surprising as thermal sintering is considered the principle deactivation mechanism. The absence of the alumina would be expected to result in a catalyst more prone to sintering.

The selectivity of the catalysts towards the water gas shift reaction was determined by analysis of the effluent recovered from knock out pots downstream of the reactors. The methanol concentrations were taken at 1 15h after stabilisation. The results were as follows;

The methanol formation relative to CO conversion gives an indication of system selectivity. Higher CO conversion results in a relative increase in methanol formation. The thermodynamic viability of the C0 ₂ to methanol reaction pathway is enhanced by the water gas shift reaction. It is therefore unsurprising that increased water consumption in the LTS reaction will push the methanol synthesis reaction. The relative rates of methanol formation are low for all samples with the maximum of 629ppm of methanol being formed.