Hydrogen is currently used mainly in industry, in activities such as the manufacture of fertilizers, petroleum processing, methanol synthesis, annealing of metals and producing electronic materials. In the foreseeable future, the emergence of fuel cell technology will extend the use of hydrogen to domestic and vehicle applications.

With respect to vehicle applications the proton exchange membrane (PEM) fuel cell vehicle is expected to be the most promising one for private and public transportation. The first automobile manufacturers have successfully launched prototype vehicles comprising PEM fuel cell stacks not larger than a conventional combustion engine. These stacks offer a permanent power of about 40 to 50 kWe while operating with pure hydrogen. Advanced experiences from powering submarines with PEM fuel cells show for the PEM fuel cell system technology a rapid development whereby the choice of fuel for a passenger vehicle did not so far keep pace.- Generally, three possible fuel options are discussed. They are hydrogen, methanol and gasoline whereby for both the latter, -high temperature fuel processors are required onboard instead of appropriate means for the storage of-pure

hydrogen.-This is still a task to be generally resolved-for the storage of liquid hydrogen, which is connected with the technical challenge of the logistics and-cryogenics.

Currently, fuel processing technologies tend to generate hydrogen instantly onboard based either on steam-reforming or on partial oxidation. Each approach has its merits. While partial oxidation is a fast exothermic process resulting in rapid start-up and short response times, steam reforming is endothermic and very efficient, producing hydrogen from both the fuel and the steam.

As shown in the prior art an ideal fuel processor is likely a combination of partial oxidation and steam reforming (see EP 0 217 532, EP 0 262 947). These documents show that the two reactions can be carried out simultaneously in a catalyst that has been described according to the European patent application EP 0 495 534 as comprising a ceria stabilized zirconia carrier promoted with Rhodium and/or Ruthenium thereon. This catalyst led to a considerable yield of hydrogen avoiding instantly the generation of-significant carbon monoxide amounts which would otherwise jeopardize the reliability and life time of the catalyst.

The international patent application WO 99/48805 presents a process for the catalytic generation of hydrogen by the self- sustaining combination of partial oxidation and steam reforming of a hydrocarbons, such as straight or branch chain hydrocarbons having 1 to 15 carbon atoms and include methane, propane, butane, hexane, heptane, normal-octane, iso-octane, naphthas, liquefied petroleum gas and reformulated gasoline petrol and diesel fuels. It is already from the afore- mentioned documents well-known to contact a mixture of the hydrocarbon, an oxygen-containing gas and steam with the catalyst comprising dispersed rhodium on a refractory oxide support material which is a mixture of ceria and zirconia. It is outlined as essentially that the catalyst is manufactured

from physically mixed ceria and zirconia to form the support material. According to example 1 of this document the conversion rate for methane is 98. 5% at an gas hourly space velocity (GHSV) close to 20,000 per hour-which led with the other data given in example 1 to an H2 Yield of 22.4 % and a CH4 selectivity of 22.8 %. Therefore, the space time yield, that means the hydrogen production rate (1/h * 1 reactor volume), lies in the range of 1,900 per hour which delivers a thermal power of about 4.75 kW per litre of reactor volume.

Taking into consideration the elevated temperature of 555°C, too, it can be easily derived therefrom that this power density will hardly match the ideas of those who intend to bring a PEM fuel cell vehicle to the market.

For these reasons, it is the aim of the invention to offer a process for preparing a catalyst that shows a significantly higher selectivity for hydrocarbons, i. e. CH4, that results in increased values for the achievable power density. It is further an object of the invention to provide a process for catalytically generating hydrogen and a process for operating a fuel cell system taking advantage on this improved power density.

According to the invention this aim with respect to the process for preparing a catalyst is reached by the following process steps: a) forming an impregnated support material by impregnating a metal oxide or a mixture of metal oxides with a soluble rare earth metal compound or with a soluble mixture of rare earth metal compounds; b) drying the impregnated support material; and c) forming the catalyst by dispersing a precious metal or a mixture of precious metals on the impregnated support material.

The achievable results have indicated much higher CH4 selectivity when impregnating the metal oxide with a soluble

rare earth metal compound and afterwards dispersing the promoter metal. Due to the improved nano-distribution (the impregnated support material did not show in XRD analyses any peak for the rare earth metal compound) the catalytic activity of the catalyst has been increased significantly.

The amount of the rare earth metal compound necessary can be instantly decreased vastly as compared with the catalyst according to example 1 of the WO 99/48805.

It could be found that excellent results are achieved when the metal oxide is zirconia. Alternatively, possible materials as refractory support material can be at least one of the group titania, alumina silica and hafnia.

With respect to a suitable rare earth metal compound excellent hydrogen conversion rates result from using a cerium-salt as a rare earth compound. As a compound capable to be prepared for the impregnation process step, there may be employed, for example, cerium hydroxide, a cerium halide, a cerium oxyhalide, cerium nitrate, cerium carbonite, cerium acetate, cerium oxalate, a cerium alkoxide such as cerium methoxide, cerium ethoxide, cerium propoxide, cerium isopropoxide or cerium butoxide, or the like. Among these compounds, the cerium alkoxide may be preferably employed.

Beside using a cerium compound, also a compound or a mixture of compounds from at least one rare earth metal selected from the group containing Praseodym, Neodym and Gadolinium.

For achieving an excellent micro-distribution of the precious metal the dispersion of the precious metal or the mixture of precious metals can be reached by impregnating the impregnated support material with a soluble precious metal compound or with a soluble mixture of precious metal compounds.

Two of the most preferred precious metals-are rhodium or ruthenium. As a raw material of rhodium, there may be mentioned, for example, a rhodium halide such as rhodium chloride or the like; a halogenated rhodinate such as sodium chlororhodinate, ammoniumchlororhodinate or the like; a halogenated rhodinic acid such as chlororhodinic acid or the like; a rhodiumhydroxide such as rhodium (III) hydroxide, rhodium (IV) hydroxide or the like; rhodium nitrate; rhodium oxide; or an organic rhodium compound such as rhodium carbonyl or the like. The raw material of ruthenium, there may be mentioned, for example, a ruthenium halide such as ruthenium iodide, ruthenium chloride or the like; a halogenated ruthenate such as ammonium chlororuthenate or the like; a halogenated ruthenic acid such as chloro-ruthenic acid or the like; a ruthenate such as potassium ruthenate or the like; or an organic ruthenium compound such as ruthenium carbonyl or the like. Among these raw materials for the precious metal ingredients of the catalyst, ruthenium- nitrosyl nitrate is preferably employed.

Furthermore, these raw materials for the precious metal ingredient of the catalyst may be employed singly or in combination of two or more.

In order to gain a long term stabile refractory support material an amount of rare earth metal compound from 0.1 to 30, preferably 0.5 to-15 weight per cent of the total weight of the catalyst is highly recommended. This composition lead to significant lower amounts of the rare earth metal compound as compared to the catalyst disclosed in the prior art, i. e. in the WO 99/048805 (mentioned before) that discloses a physical mixture of equally zirconia and ceria as starting ingredients.

In order to support the catalytic activity in a sufficient manner and owing to the impregnation process step, the amount of precious metal is 0.01 to 10, preferably 0.05 to 2 weight

per cent of the total weight of the catalyst which is advantageous with respect to the manufacturing costs, too.

According to the invention a process for the catalytic generation of hydrogen by a combination of partial oxidation and steam reformation of a hydrocarbon is provided that comprises : a) vaporizing the hydrocarbon; b) forming a gas mixture by adding steam and oxygen or an oxygen-containing gas to the vaporized hydrocarbon; c) contacting said gas mixture with a catalyst manufactured according the method given in any one of the claims 1 to 11 under the condition of elevated temperature and pressure as compared with standard condition (20°C, 1 bar).

As being observed during the test series performed under this above-mentioned conditions the temperatures for gaining an satisfying amount of hydrogen from both gaseous (C1 to C3) and liquid (C4 to Ciao) hydrocarbons in the catalytic reactor are significantly lower as compared with conventional endothermic natural gas and naphtha based hydrogen plants.

Suitable raw materials for this process are hydrocarbons in form of a straight chain or branch chain hydrocarbon containing 1 to 10 carbon atoms; the hydrocarbon contains 1 to 10 carbon atoms derived from the classification paraffins, olefins, naphtenes and aromatics (PONA) and isomers therein.

As examples there may be mentioned that the hydrocarbon is selected from methane, ethane, propane, butane, pentane, hexane, heptane, octane and their isomers, natural gas, naphthas, liquefied petroleum gas, isomerates, platformates and other blending components of the gasoline pool giving research octane numbers (RON = 85 to 100).

With respect to the content of oxygen in the gas mixture it is preferred to use air or enriched air as the oxygen

containing gas such that the content of oxygen is greater than 20 % vol. and less than 80 % vol.

Other preferred process conditions are: a) the steam to carbon ratio is between 1 to 10, preferably 2 to 5; and/or b) the ratio of oxygen to hydrocarbon in the feed and the oxygen required by stoichiometry is between 0.5 to 1; and/or c) the ratio of steam to hydrocarbon in the feed and the steam required by stoichiometry is between 1 to 10, preferably 2 to 5; and/or d) the temperature is between 200 and 700°C, preferably between 450 and 600°C ; and/or e) the pressure is between 1 to 20 bar, preferably between 1.5 to 8 bar; and/or f) the gas hourly space velocity is between 20000 to 200,000 per hour.

With respect to the method for operating a fuel cell system the solution according to the invention comprises a process for the catalytic generation of hydrogen being performed under the conditions as described above.

In order to decrease the complexity of the fuel cell system it is foreseen that after vaporizing a gasoline the catalytic generation of hydrogen takes place at temperatures lower than 700°C followed by a preferential oxidation process (PROX). In this embodiment downstream the vaporizer the catalyst is placed performing as a POX-reactor.

Additional advantageous variations of the inventions may be derived from the other dependent claims.

The present invention is further described by way of the following illustrative examples with respect to the preparation of the POX catalyst and the micro reactor data.

Example 1: Methane partial oxidation with Rh and Ru catalyst 1.1 Catalyst preparation A batch of catalyst with a nominal composition of 1% Rh/5% CeO/ZrO2 and 10% Ru/10% CeO/Zr02 (based on the proportion of the precursors) was prepared by first impregnating the crushed zirconia support material with an aqueous Ce-salt solution to form a slurry. This slurry has been dried by the rotavap method at temperature of 85°C and calcining the product in an airflow oven to provide a cerium impregnated support (CeO/ZrO2).

In detail, the Cerium doped support has been prepared as follows: 1 gram of crushed zirconia support, granules of 0.125-0. 25 mm particle diameter, was impregnated with stirring with 4.0 ml of cerium (IV) ammonium nitrate (12.78 mg Ce/ml). The resulting slurry was transferred to a rotavap apparatus and dried at 85°C and 100 mbar pressure. Drying was completed in a drying oven at 125°C for 3 hours under 100 mbar pressure. Calcination with an airflow of 100 ml/minute at 500°C for three hours completed the preparation of the cerium doped support (5% Ce/ZrO2).

It should be pointed out at this occasion that the support material may be in all other reasonable form suitable for fixed bed reactor applications, such as spheres, extrudates, cylinders, tablets, rings and half-rings. It could be alternatively also in the form of monoliths or other structured support packings, such as ceramic honeycomb bodies, stacks of juxtaposed metallic plate-type catalysts having the catalytic material coated on the surfaces of the metallic plates, for fixed bed applications.

Secondly, this Cerium-impregnated zirconia support material was impregnated with an aqueous Rh-salt solution and an

aqueous Ru-salt solution resp. to form a slurry followed by drying the slurry by the rotavap method and afterwards calcining the product in an airflow oven to give the nominal compositions 1% Rh/5% CeO/ZrO2 (hereinafter referred to as PSI Cat. Rh) and 10% Ru/10% CeO/zr02 (hereinafter referred to as PSI Cat. Ru).

In detail, the POX Catalyst then has been prepared as follows: 5.1 ml rhodium nitrate (10 mg Rh/ml) was added to 5 grams of doped support with stirring for three hours. The slurry was transferred to a rotavap apparatus and dried at 85°C and 100 mbar pressure. Drying was completed in a drying oven overnight at 120°C. Calcination with an airflow of 100 ml/min. at 550°C for three hours completed the preparation of the POX catalyst with a nominal composition of 1% Rh/5% Ce/ZrO2- 1.2 Microreactor Data A small bed of granulated catalyst (0.1 g) in the size range of (0.125 to 0.250 mm), nominal composition 1% Rh/5% CeO/ZrO2, was placed in a glass lined steel reactor and positioned at the center of an electrically heated oven. At a pressure of 4 bar absolute, the catalyst was activated by degassing in flowing nitrogen at 300°C, followed by a catalyst reduction with hydrogen at 80 ml/minute at 550°C. The stoichiometry for the partial oxidation/steam reforming process of methane to hydrogen is CH4 + 0.5 02 + H20 = C02 + 3 H2- (1) A gas mixture of methane (6.0 standard ml/min), nitrogen (25 standard ml/min), oxygen (3.0 standard ml/min) and steam (18.8 standard ml/min) was passed through the catalyst bed at an oven temperature of 550°C. At this temperature, 68.5% of the methane was converted to reformate containing 24.4% H2/9. 3% C02/1. 4% CO/64.7 N2 (plus water and unreacted methane). The catalyst was 720 hours onstream at various

temperatures (450 to 550°C) and conditions, indicating significant stability.

In comparison with the prior art catalyst according to WO 99/48805, page 8, example 1 (hereinafter referred to as"JM Cat. Ex 1") containing of the same nominal composition the experimental data is listed below in table 1: PSI Cat. Rh PSI Cat. Ru JM Cat. Ex 1 Temp. °C 550 550 555 Pressure bar 4 4 appr. 2 GHSV h-1 45, 312 44, 928 19, 620 Inlet CH4 % 11. 3 13. 7 14. 5 XH20/X02 3. 1/1 3. 4/1. 1 3. 2/1.1 CH4 Conv., % 68. 5 66. 6 98. 5 H2 Yield, % 52. 5 51. 1 22. 4 CH4 Select., % 76. 6 76. 6 22. 8 STY, 1 H2/h/lrv 8, 102 6, 626 1, 915 GHSV : gas hourly space velocity, litres feed gas/hour/litre reactor volume (Irv) B : molar ratio of species into the reactor/species from equation given above Conversion * selectivity = Yield STY: space time yield, hydrogen production rate in litres H2/h/lrv Table 1: Experimental data of Example 1 The advantage of the cerium impregnation of the PSI Cat. Rh and the PSI Cat. Ru over the catalyst made from a physical mixture of supports CeO and Zr02 (JM Cat. Ex. 1) can be seen from the higher H2 production (STY) at higher flow rates (GHSV) due to the higher selectivity 76.6 versus 22.8.

Example 2: Partial oxidation of isooctane, platformer feeds

Comparison catalysts were prepared by two methods: 2.1 The first batch for this example has been prepared with the Cerium impregnation according to Example 1,1. 1, giving a nominal composition of 1% Rh/5% CeO/ZrO2.

2.2 The second batch for this example started with a physical mixture of CeO and ZrO2 in the same proportions as under 2.1 followed by Rh impregnation to give a nominal composition of 1% Rh/5% CeO/ZrO2, i. e. following the procedure of Example 1 in the WO 99/48805.

In a microreactor as in Example 1,1. 2, two representative liquid feeds (isooctane und refinery platformate feed with research octane number, RON = 75) were used to compare the activity of the catalyst preparation 2.1 and 2.2 at the same experimental conditions for partial oxidation (POX) to produce hydrogen. The stoichiometry for the partial oxidation of isooctane is C8H18 + 2 02 + 12 H20 = 8 C02 + 21 H2 (2) and the experimental data is given in Table 2 below: Isooctan Feed Cat. 2.1 Cat. 2.1 Cat. 2.2 Cat. 2.2 Temp., °C 450 475 450 475 Pressure, bar 5 5 5 5 WHSV, h-1 8 8 8 8 % H2 (dry) 14. 0 17. 0 7. 4 13. 1 Hotspot, °C 45 45 35 34 STY, 1 H2/h/Irv 5312 6849 2447 4807 WHSV: isooctane feed rate in grams/hour/gram of catalyst STY: hydrogen production rate in litres H2/h/lrv Table 2: Experimental Data of Example 2, Isooctan feed

Once again, the advantage of the cerium impregnation (Cat.

2.1 and Cat. 2.2) over the physical mixture of supports Ceria and zirconia is seen from the higher H2 production (STY), at higher flow rates (GHSV) due to the higher selectivity. This higher activity is caused by the nano-distribution of the cerium on the zirconia support. In comparing the different catalysts, the catalyst prepared under impregnation with the aqueous cerium-salt solution does not show any peaks for ceria in an XRD analyses implying that both the ceria and the precious metal content are dispersed that far that grains over 50 Angström have not been built and as a consequence peaks for ceria and the precious metal could not be observed.

Table 3 below shows the corresponding data for the refinery platformer feed (RON =95). The amount of sulphur contained in the feed was lower than 1 ppm. Refinery Cat. 2.1 Cat. 2.1 Cat. 2.2 Cat. 2.2 platformer feed RON 95 Temp. , °C 450 475 450 475 Pressure, bar 5 5 5 5 WHSV, h-1 8 8 8 8 % H2 (dry) 10. 9 19. 5 6. 2 10. 0 Hotspot, °C 36 22 34 29 STY, l H2/h/Irv 4, 235 8,261 2,043 3, 578 Table 3: Experimental data for Example 2, Refinery platformer feed RON 95 With respect to the results from this example, too, the catalyst having impregnated cerium dispersed thereon shows superior behaviour over the catalyst starting with physically mixed ceria and zirconia.

Example 3: Partial Oxidation of isooctane

And last but not least, in a direct comparison of the partial oxidation of isooctane according to equation (2), the catalyst of this invention, Example 1,1. 1, was compared to the catalyst according to the prior art document WO 99/48805, Example 7, page 11, last paragraph to page 12, first paragraph (hereinafter referred to as"JM Example 7/'), at the same experimental conditions using 0.2 g catalyst in both cases. The results are given in Table 4 below: Isooctane feed PSI Cat. Rh JM Example 7 Catalyst wt. , g 0. 2 0. 2 Temp. , °C 550 550 Press. , bar 2 2 WHSV, h1 14. 7 14 Liquid i-C8, cm3/h 4. 2 4 Water, cm3/h 4. 1 4 Air, cm3/min 105 175 Conversion, % 64 100 Hotspot, °C 80 not known % H2 (dry) 36. 8 33 % C02 (dry) 17. 0 15 % CO (dry) 6. 0 5 % CH4 (dry) 2. 1 not known STY, 1 H2/h/lrv 28, 005 15, 153 ( ?) Table 4: Experimental data of Example 3, isooctane feed The example repeats showing that with the same quantity of catalyst and the same feed inlet conditions, more hydrogen was produced by PSI Cat. Rh, made by cerium impregnation of the support at a lower conversion than by the prior art catalyst JM Example 7, made by the physical mixture of the oxides of cerium and zirconium.

As pointed out by the interpretation of the results from the different examples the nano-distribution of the cerium compound on the zirconia lead to the significant increase of

the catalytic activity of the catalyst. As far as results for comparising catalyst containing other rare earth metal compounds than cerium compounds does not exist in the prior art it should be pointed out that this nano-distribution of a rare earth metal compound not only serves as a stabilizing compound for the metal oxide support compound by contributes in a non-neglectible manner already to the catalytic activity of the catalyst. Further, it has to be pointed out that the use of other precious metal compounds such as platinum, iridium but also compounds from tungsten, molybdenum, cobalt can be considered in a reasonable manner.

With respect to the afore-mentioned Rhodium content example have been prepared by slashing the rhodium content down to 0.1 wt%. It has to be pointed out that the performance in the light of this significantly lowered rhodium content decrease only by 50% in comparison with the 1 wt% rhodium catalysts.

In other words, although the content of the rhodium was cut down by a factor 10, the performance suffered only a 50% loss. According the limited world's annual production of rhodium successful results could have been even proved when limiting the consumption of rhodium significantly as compared to the experimental results giving above in detail.