The method according to the invention can be used, for example, in a gas filter for the removal of organic sulphur compounds from natural gas for a PEMFC fuel cell. The invention also relates to a method for depositing metal salts on a support material to prepare the adsorbent.

State of the art The'polymer electrolyte (or proton exchange) membrane fuel cell' (PEMFC) is an important candidate for relatively small scale applications as stationary micro combined heat and power (ß1-CHP) and in electric transport. The fuel for the PEMFC is hydrogen. In the short term, successful use of PEMFCs is dependent on the availability of hydrogen, for which there is as yet no (large scale) infrastructure. Currently, therefore, throughout the world a great deal of work is being carried out on small catalytic fuel conversion systems to generate hydrogen from logistical fuels such as diesel, petrol, naphtha, LPG and natural gas where the fuel cell is installed. Amongst these logistical fuels, the use of natural gas offers many advantages in this regard. For instance, natural gas has a high energy density, is relatively clean and can easily be stored in liquid form. Moreover, natural gas (still) occurs all over the world, frequently in appreciable quantities.

Depending on nature and origin, natural gas contains a greater or lesser amount of sulphur, for example in the form of naturally occurring compounds such as mercaptans and other organosulphur compounds, hydrogen sulphide and carbonyl sulphide. For domestic use natural gas is first desulphurised at the source, after which a sulphur-containing odorant is added on the grounds of safety considerations with regard to leaks. This is subject to statutory regulations in various countries. Widely used odorants are, inter alia, ethyl mercaptan (EM), normal-propyl mercaptan (NPM), iso-propyl mercaptan (IPM), secondary-butyl mercaptan (SBM), tertiary-butyl mercaptan (TBM), dimethyl sulphide (DMS), dimethyl disulphide, diethyl sulphide, diethyl disulphide, tetrahydrothiophene (THT) and mixtures of these odorants. Which odorant or which mixture of odorants is used

depends on, inter alia, the degree of adsorption of the odorant (s) on specific constituents of the soil through which the natural gas pipelines run. The cyclic sulphide tetrahydro- thiophene (THT, tetramethylene sulphide), which is widely used in the Netherlands and in the rest of Europe, offers many advantages for use as a natural gas odorant, such as a low odour limit, a typical'gas'odour, not being readily oxidisable in gas distribution systems and a relatively good soil permeability. In the Netherlands approximately 18 mg THT is added per m3 natural gas. This corresponds to approximately 5 ppm sulphur. Incidentally, Dutch natural gas naturally contains little sulphur.

A typical conversion system for natural gas comprises the following process steps: 1. a natural gas processor for converting natural gas to synthesis gas via, for example, catalytic partial oxidation, 2. a water gas shift section to minimise the CO content and to maximise the hydrogen content in the synthesis gas, 3. a system for the preferential oxidation of the final residues of carbon monoxide in the synthesis gas in order to prevent poisoning of the PEMFC, 4. a PEMFC unit and an afterburner.

The catalysts that are used in such a natural gas conversion chain (steps 1-3) and in the polymer fuel cell are sensitive to sulphur in the fuel. This applies in particular to the low- temperature shift catalyst based on copper and zinc oxide and the platinum-based anode catalyst of the polymer fuel cell. The sensitivity of the other catalytic process steps to sulphur is uncertain, but is probably high. As a precaution it is therefore best to remove sulphur compounds from the natural gas with the aid of a suitable filter material before the gas is used in the conversion chain.

Based on the annual demand for heat by an average Dutch household, a u-CHP installation will use approximately 1,200 m3 natural gas for the production of electricity and heat. This quantity will have to be desulphurised to protect the natural gas conversion chain and to protect the fuel cell. A quantity of 1,200 m3 natural gas to be purified corresponds to approximately 21.6 g THT. For a filter volume of 5 litres the capacity of the filter material must be at least 4.32 g THT per litre. For a bulk density of the filter material of 0.6 kg/l this corresponds to a sulphur adsorption capacity of approximately 0.6 % (m/m) (as S).

Incidentally, a u-CHP installation can consume distinctly more than 1,200 in natural gas.

For instance, additional heat demand is met by a peak burner. THT does not have to be removed from the natural gas that is burned in this burner. This also applies for the natural gas that is used for cooking and producing hot tap water.

For successful use in a natural gas-fired micro combined heat and power installation, a THT filter must preferably meet the following conditions: (a) high activity and selectivity for the removal of THT (that is to say as low as possible a residual content of THT in the filtered natural gas), (b) not give rise to an exothermic reaction during the adsorption process (c) a capacity that is so high that the filter has to be replaced at most once a year (for example during the annual service of the system), (d) a size that is as small as possible (maximum 5 litres, assuming that a p-CHP installation will be approximately the same size as a conventional central heating installation (volume of approximately 200-300 1), (e) robust (not sensitive to variations in gas demand and gas composition (with the exception of THT)), (f) inexpensive in use, (g) easy to fit and to replace, (h) no or manageable drawbacks from the environmental standpoint in fitting, use and disposal of spent filter material.

Because of the variety of natural and added sulphur compounds that can occur in logistical fuels, in conventional fuel conversion systems (industrial hydrogen production (petro) chemistry) use is often made of a two-step process to remove sulphur from the feed.

Briefly, this process consists of hydrodesulphurisation (HDS; catalytic conversion of organosulphur compounds with (recycled) H2 to give H2S), followed by removal of H2S by means of, for example, iron oxides or zinc oxide. These technologies have more than proved their worth on the industrial scale. The industrial HDS/ZnO technology is less suitable for a relatively small scale application such as the removal of THT from natural gas for micro combined heat and power because of the scale, complexity and cost price.

Little is disclosed in the literature with regard to the direct (one-step) removal of low concentrations of THT from natural gas in the context of hydrogen production for PEMFC applications. In general the use of active charcoal, molecular sieves or zeolites is mentioned as technology for the removal of sulphur compounds from natural gas at ambient temperature. For instance, in WO 00/71249 a molecular sieve is described as adsorbent and catalyst for the removal of sulphur compounds from both gases (for example ethyl mercaptan from natural gas) and liquids and in EP-A 781 832 the use of type A, X, Y and MFI zeolites as adsorbents for H2S and THT in natural gas is described. However, the adsorption capacity of such adsorbents for odorants such as THT in natural gas is so low that for annual use in a domestic u-CHP installation a large volume of adsorbent is required (typically more than 10 litres). This is not desirable in a small scale installation. It is also necessary that the zeolite is exchanged with specific cations, washed to remove salt residues and then calcined at temperatures between 250-500 °C.

In EP-A 1 121 977 a novel zeolite is described as adsorbent for the removal of sulphur compounds from, for example, natural gas. The zeolite is of the X, Y or p type and contains-ion-exchanged-silver, copper, zinc, iron, cobalt or nickel. In particular, the <BR> <BR> silver-exchanged Y zeolite (Ag (Na) -Y) is found to be very effective in the removal of a mixture of 1.2 ppm TBM and 1.8 ppm DMS from town gas (87.8 % methane, 5.9 % ethane, 4.6 % propane, 0.8 % n-pentane and 0.8 % i-pentane). When this gas is passed through, the sulphur is removed virtually quantitatively. When the zeolite becomes saturated, the sulphur concentration in the filtered gas rises. When a level of 0.1 ppm is reached, the zeolite is found to have adsorbed approximately 4 % (m/m) sulphur (as S).

Because of the large amount of silver on the zeolite, the commercial cost price will be high.

Moreover, after use the spent material will have to be treated as chemical waste. It is also found that the zeolite has to be washed and then calcined (approximately 400 °C) after impregnation or ion exchange. This document also gives results of comparative adsorption experiments with commercial zeolites and other commercial adsorbents such as active charcoal, zinc oxide, active alumina and silica gel. With the exception of an Na-X zeolite (capacity 0.23 % (m/m) S) all these materials are found to have a very low adsorption capacity (< 0.08 % (m/m) as S) for TBM and DMS.

Summary of the invention The aim of the invention is therefore to find a method for the removal of naturally occurring and/or deliberately added sulphur-containing organic compounds, such as the odorant THT from a fuel gas like natural gas, in which an inexpensive and environmentally friendly material is used that has a high activity and high capacity for the removal of sulphur-containing organic odorants, such as THT from natural gas, at relatively low temperatures. A further aim of this invention is to find a method that is able to remove naturally occurring and/or deliberately added sulphur-containing organic compounds, such as odorants, from fuel gases at room temperature and operating temperature. A further aim is to find a method with which use is made of adsorbents that are easy and inexpensive to prepare.

Surprisingly, it has been found that support materials on which metal salts have been deposited are particularly active, without further calcination or drying at high temperatures then being needed, in the removal of organosulphur compounds from natural gas at room temperature and operating temperature (for example approximately 30-50 °C) and, for example, are able to adsorb an appreciable amount of THT. The invention therefore relates to a method for the removal of organosulphur compounds from a fuel gas stream wherein the gas stream is brought into contact with an adsorbent, characterised in that the adsorbent is a support material comprising a metal salt.

In a specific embodiment, the invention relates to a method for the removal of organosulphur compounds from a fuel gas stream wherein the gas stream is brought into contact with an adsorbent, characterised in that the adsorbent is a support material on which a metal salt has been deposited, and wherein no heat treatment of the support material is carried out after the deposition of the metal salt, except for a heat treatment at temperatures below 100 °C.

The invention also relates to a method for depositing a metal salt on a support material, comprising : - mixing the desired amount of metal salt of approximately 0.2-50 % (m/m) (based on the metal with respect to the support material) with a liquid,

- mixing the solution or suspension with the support material at temperatures of up to approximately 60-80 °C, with stirring and/or ultrasound waves - drying the product obtained at temperatures of up to approximately 60-80 °C.

The invention also relates to adsorbents that have been obtained or can be obtained in this way and to the use of such adsorbents for the removal of organosulphur compounds from fuel gas streams, and wherein no heat treatment of the support material is carried out after the deposition of the metal salt, except for a heat treatment at temperatures below 100 °C.

The invention also relates to a combination of a gas filter based on an adsorbent and a (PEMFC) fuel cell, characterised in that the adsorbent is a support material on which a metal salt has been deposited (and wherein no heat treatment of the support material is carried out after the deposition of the metal salt, except for a heat treatment at temperatures below 100 °C.

Description of the invention The support material on which metal salts have been deposited and that is used as adsorbent in the method of the invention can be a material chosen from the group consisting of natural or synthetic clay mineral, (active) charcoal, natural or synthetic zeolite, molecular sieve, (active) alumina, (active) silica, silica gel, diatomaceous earth and pumice, or other adsorbents known to those skilled in the art (such as, for example, monolites constructed from the abovementioned support materials). Preferably, the support material has a BET surface area of at least approximately 1 m2/g, for example between approximately 1 and 1,500 m2/g, like approximately 5 and 1,500 m2/g. In one embodiment the BET surface area is between approximately 10 and 500 m2/g. In one embodiment the support materials are adsorbents, that is to say the support materials are also already able to adsorb organosulphur compounds without the deposited metal salt. In one embodiment the support materials are porous, such as is the case with, for example, zeolites or aluminas. In other embodiments the support material is one of the materials as described above, with the exception of zeolite, or one of the materials as described above with the exception of a clay mineral from the hormite group, or one of the materials as described above with the exception of zeolite and a clay mineral from the hormite group, or one of the materials as described above with the exception of sepiolite.

Clay minerals that are suitable and do not belong to the hormite group are, for example, bentonite, montmorillonite, vermiculites, smectites, halloysites, hydrotalcites, kaolinites, illites, saponites and hectorites. In one embodiment the support material is chosen from one of these clay minerals.

Suitable metals are transition metals, lanthanides and also some alkali metals or alkaline earth metals, such as metals from the groups la, Ib, IIb, Eb, IVb, Vb, Veb, vu of the periodic system. In particular, this embodiment comprises a method where the metal is chromium, manganese, iron, cobalt, nickel or copper. Suitable metal salts are, for example, chlorides, nitrates, sulphates, chlorates, phosphates, formates, carbonates, oxalates, acetates, etc. In one embodiment an adsorbent is used where the support material is impregnated or mixed with an iron (II) salt or iron (m) salt. In another embodiment metal chlorides are used and the invention comprises, for example, a method where the metal salt is iron (II) chloride or iron (ni) chloride. The salts can also be coordinated by water molecules. The support material can also be provided with combinations of metal salts, for example salts of iron <BR> <BR> and chromium, or copper and chromium, copper and iron, etc. , more particularly, for example, sepiolite impregnated with a copper salt (such as copper acetate) and an iron salt (such as iron (ni) chloride). The loading with the metal in the form of a metal salt will depend on the metal chosen. In general, the amount of metal will be approximately 0.2- 50 % (m/m) (based on the metal with respect to the support material), for example approximately 0.2-40 % (m/m), preferably between 0.5 and 20 % (m/m), for example 2,5 or 10 % (m/m).

The support material can be physically mixed with the metal salt, with or without the addition of a small amount of liquid (for example water, ethanol or another low-boiling liquid). A suitable adsorbent for the method of the invention can be obtained by this means.

In one embodiment of the invention a method is used with which the metal salt is applied to the support material by means of impregnation. Preferably, this is carried out using aqueous solutions or suspensions at temperatures of up to approximately 60-80 °C, for example at room temperature. With this method use can be made of the incipient wetness technique ('dry impregnation'). In a specific embodiment a method is used with which the support material, for example sepiolite, is impregnated with iron (E) chloride.

The adsorbent can be loaded with the metal salt (depositing of metal salts) with means known to the person skilled in the art, like e. g. wet impregnation (the volume of a liquid with (solved) salt is larger than the pore volume of the adsorbent); dry impregnation (or "incipient wetness" : volume of liquid with (partially solved) salt is equal to pore volume of adsorbent); with ion-exchange (exchange in the liquid phase, wherein the metals (ions) to be exchanged are at least partially solved in the liquid as ions (or as complexed ions) and wherein the adsorbent is stirred in the liquid with the metals to be exchanged); or with the dry mixing as mentioned above (without liquid).

Good results are achieved when the support material is loaded as follows: 'the desired amount of metal salt approximately 0.2-50 % (m/m) (based on the metal with respect to the support material) is mixed with a liquid, the solution or suspension is mixed with the support material, at temperatures of up to approximately 60-80 °C, with stirring and/or ultrasound waves 'the whole is dried (in air) at temperatures of up to approximately 60-80 °C.

If a suspension is used, the incipient wetness method can be employed.

Therefore, the invention also comprises a method for the deposition of metal salts on a support material, comprising mixing the desired amount of metal salt of approximately 0.2-50 % (m/m) (based on the metal with respect to the support material) with a liquid, mixing the solution or suspension with the support material at temperatures of up to approximately 60-80 °C, with stirring and/or ultrasound waves, and drying the product obtained at temperatures of up to approximately 60-80 °C. The person skilled in the art may also combine steps for loading the support material. The method for loading the support material according to the invention can generally be described by: 1. providing the desired amount of metal salt approximately 0.2-50 % (m/m) (based on the metal with respect to the support material), and optionally mixing the metal salt with a liquid, 2. providing the support material, and optionally mixing the support material with a liquid, 3. mixing the metal salt, metal salt solution or metal salt suspension of step 1 and the support material or support material suspension of step 2, at temperatures of up to approximately 60-80 °C, and optionally admixing a liquid,

4. the whole is dried at temperatures of up to approximately 60-80 °C.

Usually, this mixing will mean stirring, but e. g. also a ball mill can be used for mixing the solution or suspension with the support material. During or after mixing, ultrasound waves can be used. Ultrasound waves can also be used to improve or speed up solving and/or suspending the desired amount of metal salt in liquid.

After impregnation, or optionally another method for the deposition of the metal salt (or combinations of metal salts), the adsorbent obtained can be subjected to a subsequent heat treatment (inter alia drying). This heat treatment (after the metal salt has been deposited on the support material) should preferably be carried out at relatively low temperatures. In one embodiment the invention comprises a method with which a heat treatment is carried out on the support material after the deposition of the metal salts, at temperatures below 100 °C.

Preferably, a method is employed with which a heat treatment is carried out on the support material after the deposition of the metal salts, at temperatures below 80 °C, for example at 30,40 or 50 °C, for a few hours in air. By this means it can be ensured that metal salts are not converted, or are not substantially converted, to metal oxides. What is meant by non- conversion of the metal salts to metal oxides is that a substantial proportion of the metal salt remains in its original form, as it was deposited, or optionally is partially oxidised, for example to an oxychloride. A substantial proportion, for example 50 % (m/m) or more will not continue to oxidise to a metal oxide (MxOy) but will remain on the support material in the form of a metal salt or optionally metal oxy-salt. The person skilled in the art will understand that the above described temperatures may depend upon the kind of metal salt and on the used atmosphere. The invention is also directed to a method wherein one does not heat to or above temperatures where the metal salt is not thermally stable anymore.

The heat treatment (like drying) can also be performed in a reducing (e. g. H2) or neutral (e. g. N2) atmosphere. The person skilled in the art will understand that the maximal temperatures as mentioned above will then be the same or may be larger, but only up to temperatures to which the metal salts are thermally stable. Preferably, the heat treatment is performed at temperatures lower than 100 °C, more preferably at or below 80 °C.

Mixing metal salts with another material to obtain an adsorbent for sulphur compounds is disclosed in US 5 853 681. This document describes low temperature (< 150 °C) sulphur adsorbents which in the active form consist of copper carbonate, basic copper carbonate and/or copper hydroxide together with a small amount of alumina and a binder. This adsorbent for low temperature desulphurisation contains a much larger amount of metal salt than the adsorbents according to the invention and that are used in the method according to the invention. The adsorbent according to US 5 853 681 contains a minimum of 75 % (m/m) metal salts. A specific support is not employed. It is thus a bulk adsorption material and as such differs from a porous support loaded with the (much) smaller amount of metal salt according to the invention. Moreover, US 5 853 681 is targeted at desulphurisation of a different class of sulphur compounds, specifically H2S.

Surprisingly, it is found that the impregnated support materials according to the invention, for example impregnated clay minerals from the hormite group, or, for example, bentonite or alpha-alumina, that have been impregnated and dried at relatively low temperatures, have good adsorptions for THT, even at adsorption temperatures of approximately 30-50 °C. Mercaptans are also better adsorbed when a support material has been impregnated with a, for example, copper salt, such as copper acetate. Therefore, according to the invention an adsorbent is obtained which has a good capacity for organosulphur compounds in the fuel gas stream even at higher temperatures (for example approximately 30-50 °C). This adsorbent is easy and inexpensive to prepare. An adsorbent can also be obtained that is able to adsorb various organosulphur compounds. Surprisingly, it is found that merely impregnating support materials (at low temperatures) already yields the result that adsorbents for organosulphur compounds are obtained that are suitable for removing these sulphur compounds from fuel gas streams.

In applications such as, for example, micro combined heat and power (p-CHP) plants, where the temperature of the adsorbent can be increased by the proximity of the plant, the clay mineral that has been provided with a metal salt, in particular a clay mineral impregnated with a metal salt, has advantages.

The method according to the invention works over a broad temperature range. In particular, the invention comprises a method with which the organosulphur compounds are removed

at a temperature of between-40 and 120 °C, more preferentially between-10-60 °C, for example 10-50 °C. The temperature that is chosen will depend on the adsorbent (for example also on the metal salt deposited) and on the application. The relatively low temperature that can be used is advantageous compared with adsorption methods that work only at high temperature, for example > 200 °C.

The adsorbents according to the invention are able to remove sulphur compounds that occur naturally and/or are added as odorant to natural gas streams, such as carbonyl sulphide, mercaptans, thiophenes and thiophanes, etc. Particularly good results are obtained in the case of the removal of gaseous organosulphur compounds that belong to the group of mercaptans and thiophenes. Here organic sulphur compounds are understood to be sulphur compounds containing at least one Cl-C8 hydrocarbon group, the sulphur atom being in the divalent state and not bonded to oxygen or another hetero-atom. In particular, the compounds concerned are compounds having the general formula CmHnSs, where m is 1-8, in particular is 2-6, n is an even number of at least 4 and between 2m-6 and 2m+2, in particular 2m or 2m+2, and s is 1 or 2. These compounds include alkyl mercaptans, dialkyl sulphides, dialkyl disulphides and the cyclic analogues thereof. Examples are dimethyl sulphide, dimethyl disulphide, tert-butyl mercaptan and in particular tetrahydrothiophene (THT). The invention therefore comprises a method for the removal of gaseous organosulphur compounds such as mercaptans, sulphides or cyclic sulphides. Thiophene and thiophenol can also be bound by the adsorbents according to the invention.

A specific problem with adsorption filters is competitive adsorption. Thus, for example, natural gas also contains an appreciable quantity of higher hydrocarbons and, for example, the amount of pentane in Dutch natural gas for commercial use is higher than the amount of THT added. Surprisingly, the adsorbents according to the invention adsorb the THT very well, despite the competitive presence of pentane and higher alkanes in the natural gas. The method according to the invention can therefore also be used for the adsorption of organic sulphur compounds from streams of fuel gas other than natural gas, such as LPG or town <BR> <BR> gas, and other light hydrocarbons, such as propane, butane, pentane, etc. , or combinations thereof.

The present invention also comprises a combination of (1) a gas filter based on an adsorbent, characterised in that this adsorbent is a support material on which metal salts have been deposited, and (2) a fuel cell, in particular of the PEMFC type. In practice, such a combination comprises, respectively, (a) an adsorbent for removal of, in particular, organosulphur compounds from fuel gases (in particular natural gas), (b) a fuel conversion chain (in which, as described above, the fuel gases (in particular natural gas) are converted to synthesis gas) and (c) the actual PEMFC unit and an afterburner. The fuel gas stream can e. g. be natural gas, LPG, etc, and is fed via lines or other means known by the person skilled in the art from (a) via (b) to (c).

The present invention also comprises the use of an adsorbent according to the invention for removal of, in particular, organosulphur compounds from fuel gases (in particular natural gas), in applications where also one or more catalysts are used, which can be deteriorated by the presence of such organosulphur compounds, e. g. one or more catalysts for the removal of one or more of CO, NO, NO2 (etc. ), N20 and hydrocarbons (which are left in the fuel gas stream). The advantage of such a use (wherein the adsorbent is used as gas filter in a fuel gas stream) is that when e. g. the catalysts to remove e. g. CO, NO, N02 (etc.), N20 and hydrocarbons are now not or at least less poisoned by organosulphur compounds which are present in the fuel gas stream before the fuel gas stream was brought into contact with the adsorbent of the invention. The fuel gas stream can e. g. be natural gas, LPG, etc, and is fed via lines or other means known by the person skilled in the art. Hence, the invention is also directed to a use of the adsorbent of the invention for diminishing deterioration of one or more selected of the group consisting of a catalyst, a material and a device by direct or indirect presence of an organosulphur compound in a fuel gas stream.

With direct or indirect presence is meant that the catalyst, device or material positioned downstream of the adsorbent of the invention may be deteriorated by organosulphur compounds in the fuel gas stream (direct) but may also or alternatively be deteriorated by reaction products or derivatives of organosulphur compounds (e. g. due to a reaction or decomposition of the organosulphur compound in a means that used the fuel gas stream) (indirect). The person skilled in the art will understand that, when using such gas stream, the adsorbent according to the invention is positioned upstream in the fuel gas stream, and the other catalyst, material or device is position downstream with respect to the adsorbent according to the invention. Instead of catalysts, or next to catalysts, materials or devices,

that are vulnerable to the direct or indirect presence of organosulphur compounds, can be protected downstream of the adsorbent. Such materials or devices can e. g. be steel, lines, pipes, other adsorbents, detectors, etc. , which may e. g. be deteriorated by the presence of compounds like sulphuric acid, SOx, H2S etc..

The amount of the adsorbent to be used will have to be determined depending on the amount of natural gas to be purified. As described above, for the consumption by an average household, a volume of 1200 m3 natural gas per year will have to be purified. For example, the method can be carried out using approximately 0.25-3 gram adsorbent (for example based on sepiolite) per m3 (Dutch) natural gas, preferably 0.5-2. 5 gram. For a natural gas flow rate of approximately 0.2 m3/h approximately 0.15-0. 5 gram adsorbent will have to be used. In practice it is found that approximately 35-150 gram adsorbent is sufficient for the adsorption of 1 gram THT.

In one embodiment of the invention a method is used that is characterised in that a clay mineral from the hormite group is used as support material. Minerals from the hormite group are, for example, palygorskite, attapulgite, sepiolite and paramontmorillonite.

Combinations of minerals or combinations with other adsorbents can optionally also be used. Preferably, sepiolite is used as clay mineral. The minerals from the hormite group are known from the literature. Sepiolite and palygorskite are, for example, described by Galan (Clay Minerals (1996), 31,443-453). Adsorbents according to the invention that are based on clay minerals from the hormite group, and in particular sepiolite, can cope with large volumes without becoming saturated and have a high activity and selectivity for the organosulphur compounds. This makes these adsorbents exceptionally suitable for the removal of organosulphur compounds from fuel gas streams that, for example, are intended for membrane fuel cells. The sepiolite that is used is natural sepiolite, such as, for example, is mined in Spain. This means that the sepiolite may be'contaminated'with other minerals, such as bentonite, attapulgite, dolomite, etc. and also zeolites. Especially for the adsorption of THT it is the case that the higher the sepiolite content of the adsorbent the better are the adsorption characteristics thereof. Preferably, the adsorbent that is based on a clay mineral from the hormite group contains 50 % (m/m), for example 80 or 90 % (m/m) or more sepiolite. More generally this means that the adsorbent preferably contains more than 50 % (m/m), for example 80 or 90 % (m/m), of the clay mineral from the hormite group. Hence,

e. g. the term adsorbent comprising 80 % (m/m) sepiolite may be a natural sepiolite comprising 80 % (m/m) of the pure mineral, as can e. g. be detected by X-ray, etc.

In general, the adsorbents also have to be sieved, i. e. treated in such a way that particles are obtained with a desired particle size. This particle size will depend on the geometry used for the reactor. As a rule of thumb, the rule that is known to those skilled in the art of at least 10 particles over the diameter of the reactor bed and at least 50 particles over the length of the reactor bed can be adopted. A good'plug flow'is obtained if this rule is maintained. A person skilled in the art will size the reactor such that the residence time of the gas in the reactor is maximum in order thus to enable an efficient as possible adsorption of the organosulphur compounds on the adsorbent.

A suitable filter is, for example, of the packed-bed type; a cylindrical pot in which the adsorbent can be placed. Stainless steel (for example grade 316L) is the preferred structural material because of the strength, the ease with which it can be processed and the relatively high chemical inertia. However, various plastics can also be used (PVC, Teflon, polycarbonate, PET). The absorbent can be kept in a fixed position in said cylindrical pot by mounting it between grids or perforated plates, which on their turn are fixed by means of rims within the pot and/or springs. A porous grid (glass filter) made of Pyrex glass, on which the adsorbent grains are placed, is on, for example, a raised (inner) rim in the cylindrical pot, above the natural gas outlet. On top of the bed of adsorbent there is an analogous glass filter on top of which a specific amount of inert, spherical fill material is deposited (for example glass beads with approximately the same dimensions as the adsorbent grains). This bed of glass beads serves to distribute the stream of natural gas uniformly over the diameter of the reactor (plug flow) so that optimum contact with the adsorbent grains is guaranteed. Finally, the fill in the cylindrical filter pot can be held in place via a (stainless steel) spring fixed at the top (natural gas inlet) with a perforated stainless steel gas distribution plate thereon. The dimensions of the filter pot of course depend on the quantity of natural gas to be filtered per year. For 1200 m3 a total volume of approximately 4 1 could suffice, depending on the adsorbent. Suitable dimensions are, for example, a height of the filter pot of 30 cm and a diameter of 13 cm. However, other ratios are also possible, provided that the criteria for good plug flow are met. In this context it is important that the combination of particle size, height of the filter pot and the natural gas

stream to be treated must not give rise to a distinct pressure drop over the bed containing adsorbent grains. <BR> <BR> <P>The gas filter herein, can be any volume like a reactor, vessel, pot, etc. , comprising the adsorbent of the invention, through which or over which the fuel gas stream is led. This can <BR> <BR> e. g. be a single-bed adsorption system, or a packed-bed system, etc. , like e. g. described in Hydrocarbon Processing, May 1996,129 ; US 2004/0031841; US 2003/0099875, US 2003/047078 ; WO 2004/014520 etc.. Hence, the term gas filter in the invention describes in general a closed volume, comprising at least one opening as inlet and at least one opening as outlet for the fuel gas stream, and comprising the adsorbent of the invention, e. g. as grains or particles, wherein the volume, the at least one inlet, the at least one outlet and the adsorbent are positioned in such a way that the fuel gas stream can enter through the at least one opening the fuel gas stream can flow over or flow through or flow over and flow through the adsorbent, and the fuel gas stream can leave the closed volume through the at least one opening. By using such gas filter, the fuel gas stream behind the gas filter comprises advantageously less or no organosulphur compounds, thereby e. g. saving the <BR> <BR> catalysts to remove e. g. CO, NO, N02 (etc. ), N20 and hydrocarbons, which may be positioned downstream of the adsorbent in the fuel gas stream, or other materials and devices..

These abovementioned characteristics make the adsorbents suitable as filter material for large scale use of micro combined heat and power for domestic use. The invention therefore also relates to the use of an adsorbent for the removal of organosulphur compounds from fuel gas streams, characterised in that the adsorbent is a support material on which metal salts have been deposited.

Another embodiment of the invention relates to the method according to the invention where the adsorbent is combined with a second adsorbent. This has the advantages that more (different) organosulphur compounds can be adsorbed or that, for example, mixtures of organosulphur compounds can be better removed from fuel gas streams. What is achieved by this means is, as a further aim, that as broad as possible a spectrum of organosulphur compounds can be efficiently removed from fuel gas streams with the aid of the method of the invention. This second adsorbent can be chosen from the

abovementioned group of support materials, or other materials that are known as adsorbents to those skilled in the art. Here, with combination of adsorbents man made combination of adsorbents are meant, either as mixtures or as combination in series.

However, e. g. natural sepiolite may comprise other material than sepiolite, that may also be able to adsorb organosulphur compounds.

When reference is made to a second adsorbent this means that in any event a second (different) adsorbent is present in addition to the adsorbent according to the invention (that is based on a support material on which metal salts have been deposited). The term'second adsorbent'can also be used to refer to a combination of adsorbents, just as the term'both' does not have to relate to only one additional adsorbent, but can also signify a number of adsorbents, in addition to an adsorbent according to the invention (e. g. from the hormite group). If combinations of ('second') adsorbents are used, these can, for example, be used in the form of mixtures, or as filters placed in series (that is to say spatially separated). The second adsorbent can be a different adsorbent in that the percentage by weight of metal salt loaded is different or because the metal salt (or combination of metal salts) is different or because the support material is a different type, or combinations thereof.

The second adsorbent can be a loaded or non-loaded material. If reference is made to the loading of a second adsorbent, this means that if several adsorbents are present, in addition to the adsorbent according to the invention, at least one of these additional adsorbents has been loaded with (i. e. provided with) a metal (salt and/or oxide). The manner in which this can be carried out has been described above in connection with the loading of support materials with metal salts. Metal oxides can be obtained by oxidising suitable salts (see, for example, US 2002/005229) or, for example, by physically mixing with suitable oxides. If zeolites are used as second adsorbent, these zeolites can also be ion-exchanged with metal salts and the zeolites can then be washed, dried and calcined (see, e. g. EP 1121977).

In a specific embodiment the invention comprises a combination of adsorbents consisting of a clay mineral from the hormite group that has been provided with a metal salt (loaded hormite, for example sepiolite impregnated with iron (m) chloride) and a clay mineral from the hormite group that has not been provided with a metal salt (non-loaded hormite, for example sepiolite). The advantage of such a combination is that a higher capacity for, for

example, mercaptans can be obtained. For practical applications, the loaded hormite can make up approximately 10 % (V/V) or more of the total combination of adsorbents.

The combination of adsorbents can be arranged in various ways. Thus, the invention comprises both a combination of adsorbents, where the adsorbents are mixed (for example by physically mixing the adsorbents) and a combination where the adsorbents are arranged in series. For example, a pressed filter or a filter arrangement in which loaded sepiolite (for example sepiolite impregnated with iron (tir) chloride), non-loaded sepiolite and active charcoal are present one after the other. Depending on the application, a person skilled in the art can choose between a large number of binary, ternary and optionally higher order combinations.

When the combination of adsorbents comprises a mixture of adsorbents, the volume of the gas filter of the invention comprises this mixture of adsorbents. The adsorbents can be mixed before the volume of the gas filter is loaded with these adsorbents. When the adsorbents are arranged in series, one can e. g. load the gas filter sequentially with the adsorbents, such that the fuel gas stream can first be led over and/or through the first adsorbent and then be led over and/or through the second adsorbent (or further adsorbents).

One may however also use two volumes, e. g. two gas filters, which are arranged in series.

In the case of combinations of adsorbents, especially in the case of mixtures, the combination preferably contains 30 % (m/m) or more of the adsorbent according to the invention (that is based on a support material on which metal salts have been deposited), for example 50,60 or 70 % (m/m) or more. In this context account can be taken of the loading of one or more of the adsorbents with the metal salt and of the intended application.

In a specific embodiment, the invention relates to a combination of adsorbents, where at least one of the adsorbents has been impregnated with iron (chloride.

In addition to the use of one adsorbent, these above combinations of adsorbents can also be used in the method of the invention. Preferably, in applications where adsorbents are arranged in series and where one (or more) adsorbents are loaded, the gas stream is first fed through a loaded adsorbent and then fed through an optionally non-loaded adsorbent.

The invention also relates to a combination of adsorbents, characterised in that at least one of the adsorbents is a support material on which metal salts have been deposited. The invention also comprises the use of a combination of adsorbents, as described above, for the removal of organosulphur compounds from fuel gas streams, for example from natural gas, town gas or LPG. The invention also relates to a combination of a gas filter based on a combination of adsorbents according to the invention (see above) and a fuel cell.

Herein, metals from the groups la, Ib, IIb, Eb, IVb, Vb, VIlb, vm of the periodic system, comprise metals like K, Rb, Cs; Cu, Ag, Au; Zn; Sc, Y, La and lanthanides like e. g. Ce, Pr, Gd, Tb, Dy, Tm, Yb and Lu; Ti. Zr and Hf; V, Nb and Ta; Mn, Re; Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt. In a preferred embodiment, metals from groups Eb, IVb, Vb, Veb, vu of the periodic system (i. e. groups 3-12 of the IUPAC periodic table of the elements). In a more preferred embodiment, the adsorbent of the invention comprises salts like chlorides, nitrates, sulphates, chlorates, phosphates, formates, carbonates, oxalates and acetates of chromium, manganese, iron, cobalt, nickel, copper or Zn (or combinations thereof). Herein, the term adsorbent is also directed to combinations of adsorbents. The phrase"support material on which metal salts have been deposited"means the same as support material on which a metal salt has been deposited, and wherein no heat treatment of the support material is carried out after the deposition of the metal salt, except for a heat treatment at temperatures below 100 °C. The phrase"wherein no heat treatment of the support material is carried out after the deposition of the metal salt, except for a heat treatment at temperatures below 100 °C"means that one may, after depositing the metal salt or metal salts, the support material (including the metal salt or salts) can be subjected to a heat treatment. In case such a heat treatment (or heat treatments) is performed, the temperature is kept below about 100 °C.

Examples Test equipment and test conditions for Example 1 The adsorption experiments were carried out in a manually operated flow apparatus constructed from-for THT adsorption-inert materials such as Teflon (pipes, taps, flow meters) and glass (reactor). The apparatus operates under virtually atmospheric pressure and ambient temperature and has a connection to the local natural gas network. Moreover, there is a facility for feeding pre-heated compressed air through the bed of adsorbent for,

for example, regeneration experiments. The total amount of natural gas fed through is measured using a standard dry gas meter. The natural gas or air flow through the apparatus can be adjusted by means of a flow meter positioned downstream of the reactor. THT in natural gas is automatically measured by a Shimadzu gas chromatograph equipped with a flame photometric detector which has a detection limit of approximately 20 ppb for THT.

The apparatus furthermore has an electrochemical THT detector for indicative measurements (resolution and detection limit approximately 0.2 ppm) of the THT content in the natural gas. An adsorption experiment starts with placing approximately 70 ml adsorbent material (particle size 1-3 mm) in the glass reactor (internal diameter 2.5 cm, height of the bed approximately 15 cm), after which the apparatus can be checked for leaks.

The automatic analysis is then started and the natural gas is fed via the reactor bypass to the gas chromatograph to determine the input concentration of THT in the natural gas (approximately 5 ppm). When this input concentration is stable, the natural gas is fed through the reactor via the gas meter. During this operation the temperature in the bed of adsorbent is measured using a thermocouple. The experiment is terminated when the THT concentration in the filtered natural gas is found to be greater than or equal to 0.1 ppm.

Table 1 lists the samples tested and the test conditions.

Example 1 (not according to the invention) In this example sepiolite (obtainable as dust-free granules; > 18 % (m/m) sepiolite and < 20 % (m/m) zeolite) is compared with various conventional adsorbents such as active charcoal (Norit, code RB1 ; based on turf, steam-activated, extruded, not impregnated); copper-and chromium-impregnated active charcoal (Norit, code RGM1; based on turf, steam-activated and impregnated); and copper oxide/zinc oxide/alumina (BASF R3-12; metal/metal oxide). The sepiolite, which has not been loaded with a metal salt, is able to bind the most sulphur. The copper and the chromium on the impregnated active charcoal are present in the form of metal oxides.

Table 1: List of samples tested and test conditions for Examples 1 and 2 Adsorbents tested: Active charcoal, Active charcoal impregnated with copper and chromium, Copper oxide/zinc oxide/alumina, Sepiolite

Volume of bed of adsorbent: 70 ml Weight of bed of adsorbent: 27-75 g Particle size: 1-3 mm Gas flow rate: 3 1/min (standard temperature and pressure: 20 °C ; 1 atm) Superficial linear gas velocity 10 cm/sec Temperature of bed of adsorbent: 16 °C-25 °C (ambient temperature) Pressure of bed of adsorbent: 1.1 bar (a) Composition of natural gas (% (V/V)) 78. 4 % methane, 4.13 % ethane, 0.95 % propane, 0. 30 % butane (n-and iso-), 0.04 % pentane, 0.05 % hexane, 13.8 % nitrogen, 2.21 % carbon dioxide 18 mg/m3 THT Results of THT adsorption tests On the basis of the breakthrough curves recorded (not shown) it is found that the non- loaded sepiolite (sepiolite sample SA1) adsorbs five to ten times more THT than the active charcoals and the copper oxide/zinc oxide/alumina material. The capacities derived for THT adsorption are shown in Table 2 together with the amount of adsorbent material required for an annual amount of natural gas of 1200 m3, to be purified from gaseous organic sulphur compounds.

Table 2: List of capacity results for THT adsorption experiments (Example 1) Adsorbent m3 filtered natural gas THT adsorption Required filter size for per litre adsorbent at capacity in % (m/m) S 1200 m3 natural gas 0. 1 ppm breakthrough at 0. 1 ppm Vol (1) Weight (kg) of THT breakthrough of THT Active charcoal 50 0.07 24.0 11.4 Active charcoal 111 0.16 10.8 5.0 impregnated with Cu/Cr CuO/ZnO/alumina 100 0.06 12.0 13.5 Sepiolite 589 0.54 2.0 1.5 It can be seen from Table 2 that for use as THT filter for a ll-CHP installation, in the case of sepiolite only 2 litres of material is needed to remove THT from the amount of natural gas required annually.

Example 2 Preparation of adsorbents An amount of support material was placed in a glass beaker and mixed with as much FeCl3 as needed to obtain a loading of approximately 10 % (m/m) Fe after drying. An amount of water such that the resulting substance was just moist was then added, whilst stirring well.

Finally, the moist substance was dried for at least 24 hours in an oven at 40 °C in air. The material prepared in this way contains approximately 10 % (m/m) Fe and is ready for use for adsorption tests. The Fe203 on gamma-alumina adsorbent (DYCAT; code D-021) was prepared via dry impregnation of the gamma-alumina with a water-soluble iron salt, drying and calcination at high temperature (> 200 °C). The resulting adsorbent contains approximately 9 % (m/m) iron.

Test equipment and test conditions The adsorption experiments were carried out in the manually operated flow apparatus described below (under Test equipment and test conditions for Example 3-6). Table 3 lists the samples tested and the test conditions. For comparison, a non-loaded version of each adsorbent was also tested.

Table 3. List of samples tested and test conditions for THT adsorption experiments Adsorbents tested: Test 1 : 9 % (m/m) Fe (as Fe203) on gamma-alumina Test 2: 10% (mm Fe (as FeCl3) on alpha-alumina Test 3: 10% (mm Fe (as FeCl3) on gamma-alumina Test 4-5: 10 % (m/m) Fe (as FeCl3) on sepiolite Test 6: 10 % (m/m) Fe (as FeCl3) on bentonite Volume and weight of bed of adsorbent: 10 ml, 5-10 g Particle size: 0. 5-1 mm Gas flow rate (STP): 0.5 I/min Superficial linear gas velocity: 5 cm/sec Temperature of bed of adsorbent: 40 °C (ambient temperature) Pressure of bed of adsorbent: 1.1 bar (a) Fuel gas for Test 1-4,6 (% (V/V)) : 78.4 % methane, 4.13 % ethane, 0.95 % propane, (natural gas from local gas supply) 0. 30 % butane (n-and iso-), 0. 04 % pentane, 0.05 % hexane, 13. 8 % nitrogen, 2.21 % carbon dioxide, 18 mgim3 THT Fuel gas composition for Test 5 (% (V/V)) : 81. 33 % methane, 2. 80 % ethane, 0. 40 % (synthetic natural gas (Air Liquide) from gas cylinder propane, 0. 10% n-butane, 14. 47% nitrogen, (water volume 501)) 0.9 % carbon dioxide, 4 ppmv TBM (tertiary- butyl mercaptan)

Results The capacities determined for adsorption of the sulphur compounds are given in Table 4.

Table 4. List of capacity results from adsorption experiments Adsorption capacity in gram/litre adsorbent at 0.1 ppm breakthrough Adsorbent (test no. ) Support Metal salt + support Test, fuel gas (sulphur compound) Fe203 on gamma-alumina (1) < 0. 5 1. 3 1.1 (THT) FeCl3 on alpha-alumina (2) < 0. 5 5.8 2.1 (THT) FeCl3 on gamma-alumina (3) < 0. 5 3.8 3.1 (THT) FeCl3 on sepiolite (4) 3.4 12.5 4.1 (THT) FeCl3 on sepiolite (5) 0.5 8.9 5.2 (TBM) FeCl3 on bentonite (6) < 1. 7 4.1 6.1 (THT) It can be seen from Table 4 that supports loaded with FeCl3 all adsorb more THT than an adsorbent loaded with Fe203. Moreover, it is found, surprisingly, that upgrading any support with FeCl3 in all cases leads to a greater adsorption of sulphur than the adsorption of sulphur by the non-loaded support. The iron chloride/sepiolite adsorbent is very good compared with other materials as far as the adsorption of THT from natural gas is concerned. The results of Test 5 clearly show that the FeCl3/sepiolite adsorbent has more potential for the removal of TBM than the non-loaded sepiolite. It further shows that for good adsorption of organosulphur compounds one has to prevent substantial conversion of the metal salt to an oxide.

Test equipment and test conditions for Example 3-6 The adsorption experiments were carried out in a manually operated flow apparatus that was connected via two on/off taps and an outflow safety device (needle valve) to the 100 mbar (o) (o = overpressure) natural gas supply network. Any desired (cylinder) gas can also be connected via this connection. The apparatus is also connected via an on/off tap and a pressure regulator to the central compressed air facility.

For experiments with LPG, the apparatus was connected to an LPG vaporiser via an outflow safety device and a pressure regulator. The vaporiser was provided with flexible and stainless-steel-reinforced LPG feed and discharge lines. Both gaseous and liquid LPG can be supplied from the tanks intended for these (a 25 1 heating gas tank for supplying LPG vapour and a 36 1 tank for supplying LPG liquid). In the case of supply of liquid LPG, the pressurised (approximately 5-8 bara) (liquid) LPG is vaporised in the vaporiser with the aid of hot water at 50 °C. A pressure regulator integrated in the vaporiser then reduces the LPG vapour pressure to approximately 0.1-0. 2 bar (o). Finally, the LPG pressure is brought down to 0.1 bar (o) via a pressure regulator fitted in the feed line to the reactors.

The gas flow rate and the total amount of gas fed in are controlled by means of a flow meter fitted downstream of the reactors and by means of a gas meter fitted upstream of the reactors, respectively. In order to be able to study the adsorption behaviour of sulphur- containing odorants (for example tetrohydrothiophene, tertiary-butyl mercaptan and ethyl mercaptan) on various porous materials, the apparatus was provided with two glass packed- bed reactors with an internal volume of approximately 0. 1 1 (Reactor 1) and approximately 0.05 1 (Reactor 2), respectively. The temperature in the reactor bed of the larger reactor, which is not thermostat-controlled, can be measured during an adsorption test using a type K thermocouple. The smaller reactor is partially submerged in a water bath, by means of which the temperature can be set to between-5 °C and 80 °C. Downstream of the reactor the sulphur concentration in the fuel gas is determined automatically using a Shimadzu gas chromatograph equipped with a flame photometric detector which has a detection limit of approximately 20 ppb for organic sulphur compounds. The apparatus also has a facility for manual determination of the concentration of sulphur compounds via two electrochemical monitors (THT and mercaptans). The gas flowing out of the apparatus is fed to the open air via a separate off-gas pipe. A small side stream of the gas flowing out is tapped off for analysis by the GC-FPD. To prevent undesired adsorption of sulphur compounds on steel

gas pipes and the like, the apparatus is as far as possible constructed of materials inert to adsorption, such as Teflon (pipes, taps, flow meters) and glass (reactors). Table 5 lists the samples tested and the test conditions.

Table 5: List of samples tested and test conditions for Example 3-6 Adsorbents tested: Example 3: 5 % (m/m) Cu-impregnated sepiolite Example 4: 2 % (m/m) Cu-impregnated sepiolite Example 5: 2 % (m/m) Cu-impregnated sepiolite Volume of bed of adsorbent: 10 ml Weight of bed of adsorbent: 5-6 g Particle size: 0.5-1 mm Gas flow rate: 0.5 1/min (standard temperature and pressure: 20 °C ; 1 atm) Superficial linear gas velocity: 5 cm/sec Temperature of bed of adsorbent: 40 °C (ambient temperature) Pressure of bed of adsorbent: 1.1 bar (a) Fuel gas composition for Example 3 81.33 % methane, 2.80 % ethane, 0.40 % propane, (% (V/V)) : 0.10 % n-butane, 14.47 % nitrogen, 0.9 % carbon (synthetic natural gas (Air Liquide) from gas dioxide, 4 ppmv TBM (tertiary-butyl mercaptan) cylinder (water volume 501)) 1.4 ppmv DMS (dimethyl sulphide) Fuel gas composition for Example 4 78.4 % methane, 4.13 % ethane, 0.95 % propane, (% (V/V)) : 0.30 % butane (n-and iso-), 0.04 % pentane, (natural gas from local gas supply) 0.05 % hexane, 13.8 % nitrogen, 2.21 % carbon dioxide, 18 mg/m3 THT Fuel gas composition for Example 5 Approximately 60 % propane, (% (V/V)) : approximately 40 % butane (n-and iso-), (commercial LPG (BK-autogas) from heating gas approximately 2 ppmv EM (ethyl mercaptan) tank) For reference, each of the above gas mixtures was also tested with the untreated sepiolite that is commercially available as dust-free granules. An adsorption experiment starts with placing approximately 10 ml adsorbent material (particle size 0.5-1 mm) in the smaller glass reactor, after which the apparatus is checked for leaks. The automatic analysis is then started and the natural gas is fed via the reactor bypass to the gas chromatograph to determine the input concentration of sulphur in the fuel gas (approximately 1-5 ppm).

Once this input concentration is stable, the natural gas is fed via the gas meter through the reactor, which is thermostat-controlled at 40 °C. The experiment is terminated when the concentration of sulphur compounds in the filtered fuel gas is found to be greater than or equal to 0.1 ppm.

Examples 3-5: Impregnation with copper An amount of 25 gram sepiolite with a particle size of 0.5-1. 0 mm was weighed out accurately and placed in a glass beaker. In the case of so-called'dry impregnation' (incipient wetness), this amount of sepiolite can adsorb at most approximately 40 ml water.

1.57 gram copper acetate was then weighed out and dissolved in approximately 40 ml demineralised water in a glass beaker with the aid of vibrating at room temperature in an ultrasonic bath for approximately 10 minutes. The sepiolite was then impregnated with the resulting solution via dry impregnation. After brief stirring by hand, the impregnated sepiolite was dried in air for a minimum of 24 hours in a drying oven at 40 °C. The material dried in this way contains approximately 2 % (m/m) Cu2+ and is ready for use for adsorption tests. A sample containing 5 % (m/m) Cu2+ was prepared in the same way as described above.

Results The capacities determined for adsorption of the sulphur compounds are given in Table 6.

Table 6. List of capacity results for adsorption experiments Sulphur compound Adsorption capacity in gram/litre adsorbent for 0.1 ppm breakthrough Example Sepiolite Cu-impregnated sepiolite TBM 3 0.5 > 12 (5 % (m/m) Cu) THT 4 3. 4 2. 3 (2 % (m/m) Cu) EM 5 < 0. 1 1.2 (2 % (m/m) Cu) The fuel gas from Examples 3 and 5 also contains a small amount of DMS. The capacity results for DMS have not been included in Table 6.

Because the available amount of the gas mixture in Example 3 ran out, no clear breakthrough of TBM was detected in this example. The capacity shown therefore relates to the total amount of gas fed through. A'temporary'breakthrough (maximum approximately 0.2 ppmv) of an unknown sulphur compound was detected for a relatively short time during the adsorption test. This compound was identified via a GC-MS analysis of a gas sample as the dimer of TBM (C4H9-S-S-C4H9, di-tertiary-butyl disulphide). In Example 5 diethyl disulphide (C2H5-S-S-C2H5, the oxidation product of ethyl mercaptan) was found to break through at a certain point in time. The capacity in Table 6 therefore also relates to the amount of filtered LPG vapour (gas mixture in Example 5) on breakthrough of approximately 0.05 ppmv diethyl disulphide (corresponds to 0.1 ppmv'S').

Breakthrough of ethyl mercaptan was not detected before the LPG heating gas tank ran out.

It can be seen from Table 6 that upgrading the sepiolite with copper leads to a clearly greater adsorption/conversion capacity, especially in the case of mercaptans TBM (in synthetic natural gas) and EM (in commercial LPG). In the case of THT, however, the performance of the sepiolite impregnated with copper is somewhat poorer than that of the untreated sepiolite.

Example 6: Impregnation with FeCl3 Preparation of adsorbent: An amount of 15 gram sepiolite with a particle size of 0.5-1. 0 mm was placed in a glass beaker and mixed with 4.35 gram FeCl3. An amount of water such that the resulting substance was just moist was then added, whilst stirring well. Finally, the moist substance was dried in air for at least 24 hours in an oven at 40 °C. The material prepared in this way contains approximately 10 % (m/m) Fe and is ready for use for adsorption tests.

Test equipment and test conditions The test equipment and test conditions are as described for Examples 3-6. The adsorption test was carried out using the natural gas from the local gas supply. In addition to the sepiolite loaded with iron, untreated sepiolite and active charcoal impregnated with copper and chromium (Norit, code RGM-1) were also tested under the same conditions for reference.

Results The THT capacity determined for the sepiolite loaded with iron is given in Table 7. For comparison, the THT capacities of untreated sepiolite and of active charcoal impregnated with copper and chromium are also included in the table.

Table 7: THT capacity of untreated sepiolite, active charcoal impregnated with copper and chromium and sepiolite loaded with Fe Adsorbent Adsorption capacity in gram/litre adsorbent for 0.1 ppm breakthrough Cu/Cr active charcoal 1.4 Untreated sepiolite 3.4 Fe3+-sepiolite 12.5 It can be seen from Table 7 that at a temperature of 40 °C the sepiolite loaded with iron is able to adsorb approximately 3.7 times more THT than untreated sepiolite and approximately 9 times more than the active charcoal impregnated with copper/chromium.

For a 1 kWe PEMFC micro combined heat and power installation this means that THT can be removed from the annual consumption of natural gas (approximately 1200 m3) with a volume of only about 2 litres of iron-sepiolite.

Example 7 Table 8 lists combinations of adsorbents according to the invention that can be used to remove (organo) sulphur compounds from fuel gas streams.

Table 8: Examples of filter composition for odorised fuel gases where the odorant mixture contains THT Odorant mixture Preferred composition of odorant filter THT Sepiolite-sepiolite impregnated with transition metal and/or active charcoal impregnated with copper/chromium THT + Sepiolite-sepiolite impregnated with transition metal or active charcoal one or more impregnated with copper/chromium mercaptans THT + Sepiolite impregnated with transition metal and non-loaded sepiolite

one or more mercaptans THT + Sepiolite-sepiolite impregnated with transition metal and active charcoal one or more impregnated with copper/chromium mercaptans THT + Sepiolite-sepiolite impregnated with transition metal and zeolite and/or molecular one or more sulphides sieve and/or active charcoal THT + Sepiolite-sepiolite impregnated with transition metal and/or active charcoal one or more impregnated with copper/chromium and/or zeolite and/or molecular sieve mercaptans + one or more sulphides The combinations of adsorbents can be combined, but they can also be arranged in series (spatially separated).

Example 8 Sepiolite that has been impregnated with FeCl3 according to the invention was dried in air at 40 °C and 80 °C for a few days. The material that was dried at 80 °C discoloured (dark brown), whilst this was not detected with the material that was dried at 40 °C.

Example 9: Comparison examples chlorides vs. oxides for adsorption of THT Preparation of adsorbents Support material was placed into a beaker and mixed with an amount of metal chloride, necessary to obtain a loading of approximately 10 % (m/m) after drying. Subsequently, under stirring, water was added to the mixture till the resulting paste showed the first traces of wetness. Finally, the moistened substance was dried for a minimum of 24 hours in an oven under air. The resulting material contains approximately 10 % (m/m) of the metal and is ready to use as an adsorbent. To investigate the effect of a higher drying temperature on the adsorption performance for THT in natural gas, part of the material has been dried for 24 hours at 120 °C under air. It is assumed that at least part of the metal chloride is converted into the corresponding metal oxide. According to the abovementioned procedure iron (hui) chloride, iron (ici) oxide, copper (In chloride and copper (U) oxide have been prepared.

Overview tested samples and test conditions for THT-adsorption experiments Tested adsorbents: Test 1: 10 % (m/m) Fe (as Fecal3) on sepiolite Test 2: at 120 °C air-dried adsorbent of Test 1 Test 3: 10 % (m/m) Cu (as CuCl2) on sepiolite Test 4: at 120 °C air-dried adsorbent Test 3 Volume and weight adsorbent bed: 10 ml; 6 g Particle size: 0.5-1 mm Gas flow rate (stp): 0. 6 1/min Superficial linear gas velocity 5.5 cm/sec Temperature adsorbent bed: 40 °C Pressure adsorbent bed: 1.1 bar (a) Fuel gas (vol. %): 78.4 % methane, 4.13 % ethane, 0. 95 % propane, 0.30 % (natural gas from the local grid) butane (n-and iso-), 0.04 % pentane, 0.05 % hexane, 13.8 % nitrogen, 2. 21% carbon dioxide, 18 mg/m3 THT Results After drying in air at 120 °C both the iron chloride and the copper chloride appeared to have changed colour, indicating a partly conversion into the corresponding oxides.

Overview capacity results adsorption experiments Adsorbent (test nr. ) Uptake capacity in gram THT/liter adsorbent at 0.1 ppmv break through Fecal3 on sepiolite (1) 12.5 FeCl3 on sepiolite dried at 120 °C (2) 3.2 CuClz on sepiolite (3) 5.4 CuCl2 on sepiolite dried at 120 °C (4) 4.0 From the table it is obvious that the metal chloride loaded samples adsorb more THT than the samples that were dried at 120 °C. The adsorbents comprising metal oxides, which were formed during the drying process possess at relatively high temperatures, have a smaller capacity for THT when compared to the corresponding chlorides. The adsorbents according to the invention have better adsorption properties that those of the prior art adsorbents, wherein the adsorbent, after loading with the metals, is subjected to a heat treatment at temperatures above 100 °C, e. g. 120°C or higher.