GB2085314A - Hydrocarbon cracking process and catalyst - Google Patents

Abstract

The reaction of a hydrocarbon with steam or carbon dioxide or a mixture thereof in net endothermic conditions to produce a gas containing carbon oxides and hydrogen is carried out using a catalyst comprising the product of thermally decomposing and reducing intimately associated compounds of nickel and/or cobalt and of at least one metal whose oxide is difficultly reducible to metal; and a water- insoluble compound of an alkali metal oxide with an acidic or amphoteric oxide or mixed oxide. Owing to the high activity and resistance to carbon formation of the catalyst the process is especially advantageous when different hydrocarbon feedstocks are to be used at different times.

Description

SPECIFICATION Catalytic process and catalyst This invention relates to a catalytic process for reacting hydrocarbons with steam to give gases containing hydrogen and to a catalyst suitable for such a process.

Such a process is operated on a large scale using a supported nickel catalyst but it is known that the catalytic metal could be cobalt or a platinum group metal, alone or mixed with each other or with nickel.

When the hydrocarbon feedstock is methane and the ratio of molecules of steam to atoms of carbon in the hydrocarbon is at least about 1.5 there is substantially no side-reaction to produce carbon. Using higher hydrocarbons or less steam resulted in deposition of carbon on the catalyst until the effect of alkali was discovered (UK 953877 and 1003702). A supported nickel catalyst containing alkali is, however, much less active than the corresponding alkali-free catalyst and it also presents the difficulty that alkali is volatile in steam and is carried downstream and deposited on cold surfaces such as heat exchanger tubes.Although industrial hydrogen production by the reaction of steam with naphtha hydrocarbons is established, no highly active catalyst of the alkalised type has become industrially available and thus efficient operation of a plant using more than one hydrocarbon feedstock alternatively has not been achieved.

One previous attempt to produce a highly active alkalised supported nickel catalyst, described in our UK 1040066, involves reacting acidic or amphoteric catalyst support material with alkali before introducing a nickel compound. The resulting catalyst, however, showed no decisive advantage over a catalyst made according to UK 1003702.

Afurther proposal to avoid the difficulties of the alkalised catalyst, described in UK 1182829, involves using an alkali-free catalyst made by reducing a precursor comprising an intimate mixture of magnesium aluminium spinel with a mixed solid phase of nickel oxide and magnesium oxide. Such a catalyst effects the steam-naphtha reaction to carbon oxides and hydrogen for long periods without carbon deposition.

However, apparently because free magnesia is present, this catalyst may be adversely affected by steam and, should regeneration be needed after accidental carbon deposition, it cannot benefit by alkali-catalysis of the steam carbon reaction.

Alongside the above proposals, which are essentially concerned with the steam-hydrocarbon reaction in net-endothermic conditions, there have been proposals to react steam with hydrocarbons higher than methane in conditions, principally involving temperatures below 600"C, in which the exothermic methanation reaction CO + 3H2 CH4 + H2O takes place to an extent sufficient to supply almost all the heat required for the endothermic reaction or possibily more than that heat requirement.The catalysts for this reaction are much more active than those used for the net-endothermic reaction but are not robust enough to be used at over about 600"C. It has been proposed to stabilise them for use in the exothermic methanation reaction at over 6009C by having present catalyst support material such as kaolin (UK 1509557) or aluminous cement (German OLS 2461482).

We have now found a way of adapting these high activity catalysts to generation in net-endothermic conditions. As a result we are able to provide a process capable of reacting steam with a range of hydrocarbons at about equal efficiency.

According to the invention a process for reacting a hydrocarbon with steam or carbon dioxide or a mixture thereof in net endothermic conditions to produce a gas containing carbon oxides and hydrogen is characterised by using a catalyst comprising the following components: (a) the product of thermally decomposing and reducing intimately associated compounds of nickel and/or cobalt and of at least one metal whose oxide is difficultly reducible to metal; and (b) a water-soluble compound of an alkali metal oxide with an acidic or amphoteric oxide or mixed oxide.

The main active metal, nickel or cobalt or a mixture thereof, is present to the extent of 3 - 80% W/w calculated as equivalent NiO on the total catalyst, more typically 10 - 60% W/w. The active metal content of component (a) is preferably at least 20% W/w calculated as equivalent NiO, especially more than 40% W/w.

Preferably component (a) contains no more than 5% of NiO + CoO not in intimate association with the difficultly reducible oxide. There may be auxiliary active metal present, for example one or more platinum group metals, the concentration of which is typically in the range 0.01 to 1.0% W/w calculated as equivalent palladium metal on the total catalyst.

The difficultly reducible oxide preferably includes an oxide of a metal having a stable trivalent or tetravalent oxide. Such a metal will normally be from an "A" group of the Periodic Table (as published in "Abridgments of Specifications" by the UK Patent Office) since "B" group compounds tend to deactivate the catalytic metals used in the process of the invention. Suitable trivalent metals include Group IIIA metals (including rare earths), vanadium, chromium and manganese. Suitable tetravalent metals include Group IVA metals and thorium. In addition U308 can be used, alone or with one or more of the others mentioned.

Especially suitable metals are aluminium, titanium, zirconium and hafnium and mixtures thereof.

The difficultly reducible oxide can be or include an oxide of a divalent metal, especially one from Group IIA of the Periodic Table. Preferably it is one, for example magnesium, capable of forming a spinel with the trivalent metal oxide or an inverse spinel with the tetravalent oxide.

If component (a) includes an alkali metal compound, that compound is present in too small a concentration to decrease significantly its catalytic activity. Usually this means a concentration of not more than 2% W/w calculated as equivalent K2O on component (a). If desired an activating concentration - typically in the range 0.2 to 1.0% W/w - can be present. For the sake of controllability in manufacture the alkali content is preferably as low as possible.

Component (a) is very suitable a composition usable as a methanation catalyst at an outlet temperature of under 500"C. Thus for example it can be a catalyst for methanation accompanying low temperature steam naphtha reaction, that is, a "CRG" catalyst, as made by co-precipitation of nickel and aluminium Salts with an alkali metal hydroxide or carbonate to give an intimate mixture consisting of 18 to 79%Wlw of NiO, balance Awl203. Such mixtures are described in UK 820257 and 969637, but for the present invention the preparation described in 969637 is modified by omitting the final addition of alkali. A further example containing also chromium oxide is described in UK 1550749. A co-precipitated nickel oxide/magnesia/alumina catalyst precursor as described in UK 1182829 is suitable as component (a).Further, analogous compositions prepared by interaction of sparingly soluble compounds of the metals in aqueous suspension, especially in conditions leading to formation of phases containing compounds of more than one such metal, can be used.

For this method the sparingly soluble compounds may have been freshly but separately precipitated.

Component (a) may be one or more complex compounds having a composition expressed by the general formula MX2+My3+(OH)2x + 3y - 2z(A2-)z.aH2O in which M2+ is nickel and/or cobalt optionally in combination with a further divalent metal that is normally solid and whose oxide is difficultly reducible to metal: M3+ is one or more trivalent metals whose oxide is difficultly reducible to metal; A2- is a divalent inorganic anion; and x, y, z and a are positive whole or fractional numbers that satisfy the relationships: x5 between 0.25 and 8.0 y is between 0.167 and 0.05 x+y a is between 0.25 and 1.0 x+y and/orthermal decomposition products of one or more such compounds, are present.In such compounds preferably x = 2 to 16, y = 2, z = 0.5 to 2.5, a = 1.5 to 6.0 subject to the condition that 2x + 3y - 2z is not less than 7.5 orgreaterthan 34; and more preferably x = 2 to 8,y = 2, z = 0.5 to 1.4 and a = 1.5 to 5.0 subject to the condition that 2x + 3y - 2z is not less than 7.5 or greater than 20. Very suitably = 6, y = 2, z = 1 and a=4.

A definition of "difficultly reducible" is to be found in the "Handbook of Chemistry and Physics", 32nd edition, 1950-51, pages 1521 - 1523. In addition to the metals mentioned therein, chromium oxide is considered to be difficultly reducible, since it is not reduced by hydrogen at atmospheric pressure at 10000C.

A suitable compound has a composition expressed by the formula: M5Mg Al2 (OH),6 CO3. 4H2O; and/or the formula: MsA12 (OH)16 CO3. 4H2O where M is nickel or cobalt.

Divalent anion A2- is conveniently carbonate, but others are possible provided they do not contain interfering elements, such as sulphur or halogen, which could act as catalyst poisons.

Component (b) can include in principle a compound of any alkali metal. In practice, however, lithium compounds are limited to processes in which the carbon deposition tendency is low, because the vapour pressure of Li OH is too low to catalyse the reaction of much carbon with steam. Conversely the vapour pressure of the hydroxide of rubidium or cesium is higher than is usually needed and may be so high that the catalyst becomes depleted in it and loses its capacity for continuous carbon free operation. Satisfactory results are usually obtained using compounds of sodium or potassium. It is within the invention to use more than one alkali metal in a particular element of catalyst or to use different alkali metals in different zones of a reactor in which the process is carried out.

The acidic or amphoteric oxide of component (b) is typically from Groups IIIA to VIA of the Periodic Table.

Among these that can be present are oxides of aluminium, titanium, zirconium or phosphorus. In order to provide the required insolubility in water the compounds should have such oxides in polymeric form. Thus for example alkali metal aluminates are unsuitable but the beta aluminas: beta M2O .11 Al203 betal M2O .7 to 8 Al203 beta11 M20 .5 to 6 Al203 (where M is an alkali metal) are a basis for useful catalysts. Lithium aluminium spinel and potassium polyphosphate can be used. As well as compounds of isopoly acids (such as polyphosphoric acid), those of heteropoly acids such as phospho-tungsto-molybdic acid are suitable. Very suitable compounds are aluminosilicates, for example kalsilite K Al SiO4, nepheline Na Al SiO4, orthoclase K Al Si3O5 and other felspars.

In addition to the alkali metal compound component (b) can include materials such as catalyst supports and hydraulic cements, that function as diluents or mechanical strengthening agents or in other auxiliary ways. One convenient way of introducing component (b) is as a calcined alkalised steam reforming catalyst containing one or more of the above-mentioned compounds, for example ICI catalyst 46 - 1. Such a component (b) can make a significant contribution to the activity of the catalyst; it is also possible that the alkali that has deactivated the nickel in component (b) is incapable of deactivating component (a).

The mutual proportions and dispositions of components (a) and (b) can be chosen, like the nature of the alkali metal compound, to suit the relative catalytic activity and carbon-resistance required. For maximum carbon-resistance the two components are preferably both very finely divided, for example both passing an ASTM 140 sieve (0.104 mm). In such a finely divided combination there is a greater chance of liquid alkali migrating from component (b) to component (a) and causing deactivation. Consequently component (b) should then contain little if any unreacted alkali and preferably contains only 70 - 100% of the alkali required to react with all its acidic and amphoteric oxides. Alternatively or additionally component (a) contains a small quantity of acidic or amphoteric material capable of neutralising alkali in course of migration.For a lower degree of carbon resistance but less chance of deactivation a particle size in the range 140 to 10 ASTM (0.1 to 2.0 mm) is suitable. The particle sizes so far mentioned relate to powdered components brought together in shaped units or coatings, as disclosed below. The invention includes also operation in catalyst beds in which components (a) and (b) are present in different shaped pieces mixed randomly or in distinct coated regions on a support structure. Usually in such a bed no shaped piece of component (a) is more than 10 mm downstream of a piece of component (b).

The catalyst units are as commonly used in catalyst technology, for example compressed cylinders or rings or partitioned rings, extruded shapes such as cylinders or such rings, approximate spheres or irregular lumps, for use in fixed beds, small-to-medium particles for use in fluidised or suspendible beds, and coatings applied to surfaces such as reactor walls, fibres, honeycombs and metal or alloy units or structures.

The starting hydrocarbon can be any of those proposed for use in the catalytic steam/hydrocarbon reaction. Off gases containing hydrocarbons and hydrogen, methane, natural gas, LPG and naphthas boiling at up to 350"C (especially up to 220"C) are the chief examples. The process is especially suitable for processes required to use different feedstocks at different times, for example natural gas in summer and naphtha in winter. "Hydorcarbon" in this specification is to be understood as including hydrocarbon derivatives, of which methanol, dimethyl ether and isobutyraldehyde are the examples so far seriously considered as feedstocksfor hydrogen production.A particular use of the process is in endothermic steam reforming of the product of the methane-producing steam/hydrocarbon reaction, because the catalyst is not subject to carbon deposition in the event of accidental breakthrough of higher hydrocarbon from the preceding stage. Another important use is in high throughput conditions such that conventional catalysts suffer deactivation by carbon and thus cause "hot-banding" or steam reformer tubes.

The proportions of steam and carbon dioxide relative to hydrocarbon and to each other depend on the purpose for which the hydrogen-containing gas is required. Typical proportions, expressed as molecules of steam plus carbon dioxide per atom of carbon in the hydrocarbon are 1.2 to 2.0 for making metallurgical reducing gas, 2.0 to 4.0 for making town gas, 2.5 to 5.0 for making ammonia synthesis gas and 2.0 to 7.0 for making hydrogen or synthesis gas for methanol, liquid hydrocarbons or oxygenated hydrocarbons. The use of steam without carbon dioxide is convenient for all these purposes except synthesis of liquid hydrocarbons or oxygenated hydrocarbons, for which hydrogen and carbon monoxide in the ratio between about 1:1 and 2:1 are required.For methanol synthesis, although the stoichiometric requirement is 2 molecules of hydrogen per molecule of carbon monoxide (corresponding to 3 per molecule of carbon dioxide), it is customary to use steam without carbon dioxide, rather than incur the expense of providing the carbon dioxide.

The temperature at the outlet is typically in the range 600 - 11 00'C, depending on the intended use of the gas. Thus it may be for example 700 - 950"C for the synthesis gases or town gas or hydrogen intermediate gas or 900 - 11 00'C for metallurgical reducing gas. The inlet temperature is typically in the range 300 - 600"C but may be up to 700"C if the starting hydrocarbon is methane.

The pressure is typically in the range 1 - 50 ata and especially over 10 ata, for example 15 - 40 ata in making ammonia synethesis gas or town gas, or for example 10 - 30 ata in making methanol synthesis gas or hydrogen; for other uses lower pressures are typical, for example 1 - 5 ata in making reducing gas.

The process can be carried out in any steam reforming plant. The commonest plant is one in which the catalyst is disposed in tubes externally heated in a combustion furnace operated at atmospheric pressure and the steam-hydrocarbon mixture is fed from top to bottom. The double-pass tube, which is fed from the top and discharges gas upwards through an internal axial tube, is equally suitable and so is the analogous tube fed from the bottom and discharging gas downwards.The heating fuel in the furnace can be the same (apart from not having been purified) as the process feedstock, but equally can be a hydrocarbon unsuitable forcatalyticsteam reforming owing to impurityortoo-high molecularweight. In a useful process the heating fuel is waste gas, chiefly methane, discharged from a fuel cell powered by hydrogen produced by the process of the invention. In a process of increasing importance the heating medium is helium used as coolant in a nuclear reactor.

If desired a plant involving heating in absence of catalyst followed by adiabatic reaction over the catalyst can be used.

The process according to the invention can be used in the zone of a steam hydrocarbon reaction in which carbon deposition would take place over an alkali-free conventional catalyst, but followed by a zone using a conventional catalyst. The first-mentioned zone is typically 10 - 50% of a steam reforming tube when the feedstock is naphtha or 3- 20% when the feedstock is methane.

Certain catalysts according to the invention have been broadly described in our UK patent 1509557. These, however, contain active metal only in component (a), and accordingly the invention provides also new catalysts or precursors in which component (b) also contains active metal or oxide. Owing to the presence of alkali such metal may be less active than the metal in component (a) but for the present definition it is assumed to be all active. A suitable active metal concentration in component (b) is in the range 10 - 40% if it is non-noble, and/or 0.1 to 1.0% if it is noble; its alkali content is 1 - 10% W/w as K2O.

The catalysts to be used in the process of the invention can be made by mixing the two components in the ratio and at the particle sizes required, possibly with auxiliary materials such as catalyst supports and binders such as aluminous cement. Unless component (b) contains over about 2% W/w of free alkali, the mixing can be dry or in the presence of water and accordingly shaping can be dry compression or a wet method such as extrusion, granulation or wash-coating.

EXAMPLE 1 Preparation ofcomponent (a) The following solutions were made up: Solution A 6 kg sodium aluminate 20 I 80% w/v nitric acid 9.25 kg nickel as nitrate and 1.25 kg "light" MgO Waterto volume 1251 Solution B 62.5 kg sodium carbonate in 375 1 of solution.

Solution C 7.5 kg sodium hydroxide in 151 of water.

Solutions A and B were heated to 85"C, and solution A added to solution B as quickly as possible. Solution C was then added to the slurry formed. With water used for washing out tanks, total volume of slurry was 800 1, this was boiled for 30 minutes to form crystalline Ni Mg carbonate hydroxide and allowed to cool.

The precipitate was washed by reslurrying and filtering several times, before drying at 120"C. The product was milled (ASTM 200) and a sample of it was calcined at425'Cfor6 hours. Its % W/w composition was as follows after allowing for a loss of 7.4 at 900"C: NiO 68.7 At203 20.8 MgO 7.3 CaO 1.2 Na2O 0.09 Preparation of component (b) A sample of rings of ICI catalyst 46 - 1 was milled to pass a 200 ASTM sieve.

(This catalyst contains about 20% W/w of NiO when in the oxidic precursor form as used. The support comprises magnesia and an iron-containing aluminious cement. It contains potassium to the extent of about 6.0% W/w calculated as K2O, and this is mainly in the form of kalsilite. A description of the preparation of such a catalyst is given in UK 1003702).

Preparation of2-component catalyst Three parts by weight of the calcined sample of component (a) were mixed dry with 1 part by weight of component (b) and 0.08 part by weight of graphite powder. The mixture was compressed into 5.4 x 5.4 mm cylinders, crushed to pass a 20 ASTM sieve, then recompressed into squat 5.4 x 3.6 mm cylinders.They had the following properties: Micromeritics: Mean vertical crush strength (MVCS) 18 - 27 kg bulk density I.0lgcm-3 helium density 3.77 g cm-3 mercury density 1.63g cm-3 pore volume 0.35 cm3 g -1 surface area 109 m2 g-1 Composition % W/w (after allowing for 13.0 loss at 900"C) NiO 56.4 Al203 23.4 Fe203 1.7 CaO 4.1 SiO2 3.2 MgO 8.5 K2O 1.5 This material is a catalyst precursor. Conversion to active catalyst and use in steam hydrocarbon reforming processes are described below.

EXAMPLE 2 Component (a) was a sample of uncalcined material as described in Example 1. Component (b) was the same as in Example 1. A dry mixture of 4 parts by weight of (b), 1 or (a) and 0.5 of substantially silica free calcium aluminate cement ("ALCOA" - RTM) and 0.11 part by weight of powdered graphite was compressed as described in Example 1. The resulting cylinders were heated to 425"C over 7 hours, held at that temperature for 6 hours and cooled. Such calcination effected a weight loss of 23.9%. They were immersed in water for 16 hours, drained and then dried at 120"C.

Their properties were: Micromeritics: MVCS 64 kg bulk density 1.16 g cm -3 helium density 3.58 g cm-3 mercury density 1.91 g cm-3 pore volume 0.24 cm3 g-1 surface area 140 m29-1 Composition % W/w (after allowing for 12.5 loss at 9000C) NiO 51.9 At203 27.4 Fe2O3 1.5 CaO 5.0 SiO2 2.85 MgO 8.2 K2O 1.3 This material is a catalyst precursor. Conversion to active catalyst and use in steam-hydrocarbon reforming processes are described below.

Processes using catalystA (a) Steam natural gas reforming af atmospheric pressure An electrically heated laboratory tubular reactor of 2.54 cm internal diameter was charged with a mixture of catalyst precursor A (5 ml) and 3.35 to 4.5 mm fused alumina chips (16 ml). The charge was heated to 450"C and the precursor reduced to active catalyst by passing 100% hydrogen through it at the rate of 50 1 h- for 4 hours.

The hydrogen supply was then replaced by a mixture of steam and natural gas of % V/v composition 91 CH4, 2 N2, 3.5 C2H6. (Before mixing, the steam was at 330"C and the gas at 200"C). Two feed rates were used, namely steam 96.3 ml h-1 of water, gas 43 1 h-1 i.e. space velocity 34200 h-1; steam 240.5 ml h-1 of water, gas 107 1 h-1 i.e. space velocity 85500 h-1.

The molar steam to carbon ratio was 3.0 for each feed rate. At each feed rate a set of runs was carried out at various outlet temperatures between 500 and 750"C and the outlet gas composition was measured chromatographically.

The same runs were carried out using a commercially available nickel-alumina/aluminous cement steam natural gas reforming catalyst crushed to chips of size range 3.35 to 4.75 mm.

Table 1 shows the percentages of unconverted methane in the outlet gases, in comparison with the percentages that would be present if equilibrium were reached.

TABLE 1 Outlet methane % V/v Temperature Catalyst A Commercial catalyst Equilibrium "C 34200 h 1 85500 h 1 34200 h 85500 h 500 37.5 50.9 73.9 74.6 20.8 542 27.0 - - - 550 - 37.8 62.6 64.6 12.3 600 18.7 29.7 49.1 57.3 6.0 640 9.6 - - - 650 - 22.2 37.8 52.8 2.0 700 6.9 18.3 30.0 50.0 0.7 720 6.1 - 20.0 750 - 15.2 - 45.5 0.2 It is evident that, although neither catalyst brings the mixture to equilibrium at the space velocity used, catalyst A is substantially more active than the commercial catalyst.

(b) Steam natural gas reforming at 28 bar abs pressure An electrically heated laboratory tubular reactor of 2.54 cm internal diameter was charged with a mixture of catalyst precursor A (40 ml) and fused alumina chips (520 ml). The charge was heated to 650" and reduced to active catalyst by passing a 10:90 hydrogen/steam mixture at 28 bar abs pressure through it for 20 hours.

The hydrogen/steam supply was then replaced by the steam-natural gas mixtures as described in paragraph (a) but at 28 bar abs pressure. Runs were carried out at 600"C, 750"C and then again at 600"C outlet temperature. The activity of catalyst A, in comparison with the commercial catalyst, is shown in Table 2 in terms of percentage methane converted, TABLE 2 Percentage methane conversion Temperature Catalyst A Commercial catalyst "C 34200 h-l 85500 h 34200 h 85500 h 600 14.4 14.0 10.0 5.6 750 - 52.3 - 38.9 600 17.4 14.1 10.1 4.9 It is evident that catalyst A is both more active and more stable than the commercial catalyst.

(c) Steam-naphtha reforming at28 bar abs pressure A reactor as used in (b) was charged with a mixture of 156 ml of catalyst procursor pellets and 364 ml of alumina chips. The charge was heated to 7400C and reduced to active catalyst by passing a mixture of hydrogen (3601 h-1)andsteam (1540 ml h-1; steam to hydrogen volume ratio 8:1) through it for 24 hours.

The hydrogen/steam supply was then replaced by a mixture of steam and the vapour of a straight-run naphtha of final boiling point 1700C, in a proportion giving a steam to carbon molar ratio of 3.0. An 18-day run at outlet temperature of 750"C but at various space velocities and steam ratios was carried out. A parallel run was carried out using commercially available catalyst 46 - 1. The results are shown in Table 3.

Note: "LHSV" is the rate of feed of naphtha measured as volume of liquid.

TABLE 3 Product gas composition % V/v Days LHSV on Catalyst ml Steam higher line h-1 ratio CO2 CO CH4 H2 hydrocarbons 6 A 516 3 18.5 9.9 12.0 59.6 10 A 514 3 19.2 10.7 12.6 57.5 10 46-1 517 3 17.5 10.4 NA NA C2 0.12 11 A 609 3 19.4 10.6 13.9 56.2 12 A 748 3 19.9 10.5 14.6 55.1 12.5 A 786 3 19.9 10.4 13.8 55.9 12.5 46-1 780 3 16.3 10.0 13.0 60.4 C30.34 13 A 496 3 19.0 10.5 12.4 59.0 13.5 A 529 2 17.6 13.3 20.7 48.4 14 A 534 1.75 16.6 13.0 20.1 50.2 14.5 A 534 1.5 15.4 15.9 26.1 42.6 14.5 46.1 524 1.5 14.2 12.4 28.0 45.4 18 A 537 3.0 18.8 10.4 16.1 54.7 18 46.1 517 3.0 16.8 9.9 NA NA C2 0.18 It is evident that catalyst A is at least as active as the commercial catalyst 46-1. No carbon was formed.

Processes using catalyst B (a) Steam-naphtha reforming at 28 bar abs pressure The procedure described in (c) above was repeated using catalyst precursor B; the results are shown in Table 4.

TABLE 4 Product gas composition % V/v Days LHSV on Catalyst ml Steam higher line h-1 ratio CO2 CO CH4 H2 hydrocarbons 7 B 535 3 18.6 9.9 13.5 57.9 C2 0.05 8 B 533 3 19.4 10.5 14.2 56.0 13 B 526 3 19.5 11.0 14.0 55.5 13 46-1 517 3 17.5 10.4 NA NA C2 0.12 13.5 B 618 3 17.2 10.9 13.6 57.1 14 B 747 3 16.5 10.2 NA NA 14.5 B 787 3 19.0 10.1 55.5 55.4 14.5 46-1 780 3 16.3 10.5 13.0 60.4 C2 0.34 15 B 522 3 20.1 11.0 13.9 54.9 16 B 526 1.75 17.3 13.8 25.3 43.6 16.5 B 519 1.5 16.8 13.9 27.2 42.1 16.5 46-1 524 1.5 14.2 12.4 28.0 45.4 19 B 906 3.0 20.5 10.8 16.0 52.8 Again the new catalyst is substantially equal to the commercial catalyst.

(b) Steam-methane reforming at atmospheric pressure A sample of catalyst B discharged from the steam-naphtha reforming run was tested as described in paragraph (a) of the catalyst A test, then further aged for 2 days at 7500C with a mixture of steam (96.3 ml h -' of water) and nitrogen (501 h-1). The space velocity in each steam-methane run was 34200 h-1. The percentages of unconverted methane in the product gases are shown in Table 5.

TABLE 5 Outlet methane % V/v Temperature Catalyst B Commercial catalyst C (fresh) as discharged further aged 445 69.8 - 490 56.0 71.1 500 - - 73.9 550 42.5 52.6 62.0 595 31.0 - 600 - 38.0 49.1 646 20.9 - 650 - 34.3 37.8 700 15.2 22.4 30.0 720 - - 20.0 750 14.2 11.2 Catalyst B has evidently retained a level of activity higherthan that of the commercial catalyst.

EXAMPLE 3 Catalysts having nickel-free component (b) Two component (a) precipitations were carried out: C. as described in Example 1; and B. as C, but without the step of adding sodium hydroxide to the slurry and boiling it.

As a result, whereas the nickel magnesium aluminium precipitate of C, like A and B, was a well crystallised sample of the materials described hereinbefore, that of D was substantially amorphous, according to X-ray diffraction. Each precipitate was washed dried and milled as before, than calcined until the loss at 900"C was 10% W/w.

A dry mixture of 14 parts of each calcined precipitate, 5.7 parts of cement (see Example 2), 1.2 parts of kalsilite K Al SiO4 and 0.7 part of graphite, all by weight, was compressed into cylinders 3.6 mm high by 5.4 mm diameter having a pellet density of 1.9 9 cm-3 and MVCS 90 kg. These cylinders were aged at 4500C for 8 hours, soaked in water for 16 hours and dried at 1200C in air for 2 hours. Their MVCS was now 136 kg and their composition % W/w: NiO 48.7 At203 37.2 CaO 5.5 SiO2 2.6 MgO 4.1 K2O 1.0 Na2O 0.3 loss at 900"C 12.2 Processes using catalysts CandD (a) Steam natural gas reforming at atmospheric pressure The runs described above for catalyst A were carried out.Then the catalyst C was aged by the following succession of treatments: steaming at 750" for 16 hours reducing in hydrogen at 450"C for 2 hours hydrogen treatment at 7000C for 64 hours re-testing at the low and high space velocities steaming at 750"C for 16 hours reducing at 700"C with hydrogen for 3 hours.

The catalyst were then re-tested at the low and high space velocities.

Catalyst D was tested in the same way, except that the ageing treatments were as follows: reducing in hydrogen at 700"C for 16 hours re-testing at low and high space velocities steaming at 7500C for 16 hours re-testing at low and high space velocities hydrogen treatment at 700"C for 16 hours.

Table 6 shows the percentages of unconverted methane in the outlet gases from the fresh and aged catalysts, in comparison with those obtained using a fresh commercially available catalyst.

TABLE 6 Outlet methane % W/w Temper Catalyst ature Fresh Aged Commercial "C 34200 h 1 85500 h 34200 h 85500 h 34200 h C 450 80.1 75.3 73.3 82.3 N/A 500 72.7 69.4 59.6 75.2 73.9 550 61.0 61.6 47.5 67.5 62.0 600 46.2 53.7 34.8 57.1 49.1 650 36.0 46.2 25.8 49.7 37.8 700 24.7 42.4 23.4 41.6 30.0 750 20.5 40.7 16.4 39.2 N/A D 450 59.6 68.5 59.6 69.8 500 47.7 57.4 45.0 62.2 550 32.4 48.6 31.8 50.6 600 24.5 40.4 20.8 41.0 )see 650 16.2 32.9 15.9 35.1 )above 700 12.2 28.7 9.6 26.8 750 10.6 26.1 7.3 23.5 It is evident that both catalysts are more active, even after ageing, than the commercial catalyst. Of the two catalysts C and D, D appears to be more active and stable.

(b) Steam-naphtha reforming at28 bar abs pressure The procedure described in (c) above was used. Table 7 shows the results for catalyst C, Table 8 for catalyst D. It is evident that catalysts C and D produce generally less higher hydrocarbon than commercial catalyst 46-1. No carbon was formed in any of the runs.

TABLE 7 Product gas composition Days LHSV on Catalyst ml Steam %W/w mg m-3 line h~1 ratio CO2 CO CH4 H2 C2H6 C6H6 C7H8 7 C 520 3.0 17.1 9.9 13.2 59.8 - - 11 C 520 3.0 17.6 10.2 13.4 58.9 - - 11 46-1 520 3.0 19.9 11.0 12.7 56.3 - 25 11.5 C 600 3.0 17.8 9.8 13.0 59.3 - 35 21 12.5 C 755 3.0 17.5 9.7 14.0 58.9 - 59 36 12.5 46-1 750 3.0 16.3 8.9 11.3 63.0 0.43 125 21 13 C 520 3.0 17.3 10.6 14.1 58.0 - 71 77 14 C 520 2.5 17.0 11.5 16.9 54.5 - - 14.5 C 520 2.0 16.4 12.4 19.9 51.2 - - 15 C 520 1.75 15.7 13.3 22.8 48.2 - - 15.5 C 520 1.5 14.5 14.9 25.6 45.0 - - 18 C 520 3.0 17.5 10.8 13.4 58.3 - 10 20 C 840 3.0 17.0 10.6 13.5 58.9 - 23 21 C 900 3.0 17.0 11.3 14.3 57.4 - 36 21.5 C 960 3.0 16.6 11.5 14.1 57.8 - 37 22.5 C 1100 3.0 17.0 11.3 15.6 56.4 - 84 13 TABLE 8 Product gas composition Days LHSV on Catalyst ml Steam % W/w mg m-3 line h~1 ratio CO2 CO CH4 H2 C2H6 C6H6 C7H8 4 D 500 3.0 18.6 9.9 14.8 56.7 - - 11 D 550 3.0 20.8 9.8 15.4 53.9 - - 11 46-1 550 3.0 18.5 9.1 11.9 59.8 0.67 690 78 14 D 560 3.0 20.8 10.3 16.5 52.4 - - 14.5 D 610 3.0 18.1 8.9 15.4 57.5 - 10 15.5 D 800 3.0 17.8 8.1 15.6 58.5 - 400 89 15.5 46-1 800 3.0 16.5 9.8 10.4 61.8 1.02 2500 634 16 D 520 3.0 16.0 8.5 14.9 60.6 - - 17 D 520 2.5 14.5 9.7 18.6 57.2 - - 17.5 D 520 2.0 15.7 9.4 17.4 57.5 - - 18 D 520 1.75 14.8 10.6 22.8 51.7 - - 18.5 D 520 1.5 13.8 12.5 28.2 45.5 - - 21 D 520 3.0 18.1 8.8 15.4 57.7 - 69 24 22 D 810 3.0 17.7 7.3 13.6 61.3 - 24 23 D 900 3.0 16.0 7.9 15.8 60.2 - 68 27 23.5 D 970 3.0 17.3 7.6 15.2 59.7 0.11 99 42 24 D 1030 3.0 17.1 8.1 15.2 59.4 0.16 176 82 24 46-1 999 3.0 17.4 9.6 9.4 61.8 1.7 4320 1765

Claims (13)

1. A process for reacting a hydrocarbon with steam or carbon dioxide or a mixture thereof in net endothermic conditions to produce a gas containing carbon oxides and hydrogen, characterised by using a catalyst comprising the following components: (a) the product of thermally decoomposing and reducing intimately associated compounds of nickel and/or cobalt and of at least one metal whose oxide is difficultly reducible to metal; and (b) a water-insoluble compound of an alkali metal oxide with an acidic or amphoteric oxide or mixed oxide.

2. A process according to claim 1 in which component (a) is a catalyst made by co-precipitation of nickel and aluminium salts with an alkali metal carbonate to give an intimate mixture consisting of 18 to 79% W/w NiO, balance Al203.

3. A process according to claim 1 or claim 2 in which component (a) includes an oxide of a divalent metal capable of forming a spinel with a trivalent metal oxide or an inverse spinel with a tetravalent oxide.

4. A process according to any one of the preceding claims in which component (a) is the product of thermally decomposing and reducing a compound having a composition expressed by the formula: M6 Mg Al2 (OH)16 CO3. 4H2O; and/or the formula M6 Al2 (OH)16 COs . 4H20, where M is nickel or cobalt.

5. A process according to any one of the preceding claims in which component (b) contains an alkali metal aluminosilicate.

6. A process according to claim 5 in which component (b) is introduced as a calcined alkalised steam reforming catalyst.

7. A process according to any one of the preceding claims in which the catalyst is a bed of shaped pieces, components (a) and (b) are present in different pieces and no shaped piece of component (a) is more than 10 mm downstream of a piece of component (b).

8. A process according to any one of claims 1 to 6 in which the catalyst contains finely divided components (a) and (b) mixed together.

9. A process according to any one of the preceding claims in which the hydrocarbon reactant has a boiling point up to 220"C and is different at different times.

10. A process according to any one of the preceding claims in which hydrogen product is used to power a fuel cell and waste gas discharged from the fuel cell is used as the heating fuel in a furnace in which the net endothermic reaction takes place.

11. A process for reacting a hydrocarbon with steam or carbon dioxide or a mixture thereof, substantially as described with reference to any one of the foregoing Examples.

12. A gas containing carbon oxides and hydrogen whenever produced by a process according to any one of the preceding claims.

13. A catalyst precursor comprising (a) the product of thermally decomposing intimately associated compounds of nickel and/or cobalt and of at least one metal whose oxide is difficultly reducible to metal; and (b) a water soluble compound of an alkali metal oxide with an acidic or amphoteric oxide or mixed oxide; component (b) containing also an oxide of a catalytically active metal.