Methane steam reforming commercial catalyst

INVESTIGATION OF SYNTHESIS GAS PRODUCTION FROM METHANE BY PARTIAL OXIDATION OVER SELECTED STEAM REFORMING COMMERCIAL CATALYSTS... 

The Deactivation of Tar Cracking Stones and of Commercial Methane Steam Reforming Catalysts In the Upgrading of the Exit Gas from Steam Fluidized Bed Gasifiers of Biomass and Organic Wastes... 

THE DEACTIVATION OF TAR CRACKING STONES ( DOLOMITES, CALCXTES, MAGNESITES) AND OF COMMERCIAL METHANE STEAM REFORMING CATALYSTS IN THE UPGRADING OF THE EXIT GAS FROM STEAM FLUIDIZED BED GASIFIERS OF BIOMASS AND ORGANIC WASTES ... 

With commercial methane steam reforming catalyst very good results are being obtained- Not only the methane in the exit gas but also higher hydrocarbons and tars can be eliminated by steam reforming, fig.4,... 

Find et al. [25] developed a nickel-based catalyst for methane steam reforming. As material for the microstructured plates, AluchromY steel, which is an FeCrAl alloy, was applied. This alloy forms a thin layer of alumina on its surface, which is less than 1 tm thick. This layer was used as an adhesion interface for the catalyst, a method which is also used in automotive exhaust systems based on metallic monoliths. Its formation was achieved by thermal treatment of microstructured plates for 4h at 1000 °C. The catalyst itself was based on a nickel spinel (NiAl204), which stabUizes the catalyst structure. The sol-gel technique was then used to coat the plates with the catalyst slurry. Good catalyst adhesion was proven by mechanical stress and thermal shock tests. Catalyst testing was performed in packed beds at a S/C ratio of 3 and reaction temperatures between 527 and 750 °C. The feed was composed of 12.5 vol.% methane and 37.5 vol.% steam balance argon. At a reaction temperature of 700°C and 32 h space velocity, conversion dose to the thermodynamic equilibrium could be achieved. During 96 h of operation the catalyst showed no detectable deactivation, which was not the case for a commercial nickel catalyst serving as a base for comparison. 

Sulfur-free odorants have been developed and commercialized, but are not yet commonly used [108]. They contain a mixture of 37 wt% methylacrylate, 60 wt.% ethylacrylate and 2.5 wt.% methylethylpyrazine. It has been proven that these components do not affect the performance of a rhodium catalyst during methane steam reforming. 

A commercial nickel catalyst was used for methane steam reforming performed at a 500 °C reaction temperature, a S/C ratio of 3.0 and atmospheric pressure, while the permeate side was evacuated. The performance of the vapour deposited platinum membrane was similar to the plated dense palladium membrane. In the permeate of the deposited ruthenium and palladium membranes, small amounts of carbon oxides and also methane were observed. While it was expected that all these species had passed through the membranes by diffusion, in addition some methane was converted into carbon dioxide over the noble metals of the membranes. Kikuchi et al. demonstrated by simulations that conversion and hydrogen permeation in a membrane reactor is higher, where the first portion of the catalyst bed is not coupled to the membrane. Such an arrangement as shown in Figure 7.16 would clearly save expensive membrane surface area. Experimental work by Itoh et al. performed for methanol steam reforming [521] confirmed the assumptions of Kikuchi et al. 

There are a number of major industrial problems in the operation of the steam reforming of methane. These include the formation of carbon on the surface of the catalyst, the sulphidation of the catalyst by the H2S impurity in commercial natural gas, and the decline of catalytic activity due to Ostwald ripening of the supported catalyst particles by migration of catalyst atoms from the smaller to the larger particles, as the temperature is increased. A consideration of the thermodynamics of the principal reaction alone would suggest that the reaction shifts more favourably to the completion of the reaction as the temperature is increased. 

They used a Ni-containing catalyst. In contrast to steam reforming of methane, methane partial oxidation is exothermic. However, the partial oxidation requires pure oxygen, which is produced in expensive air separation units that are responsible for up to 40% of the cost of a synthesis gas plant (2) (in contrast, the steam reforming process does not require pure oxygen). Therefore, the catalytic partial oxidation of methane did not attract much interest for nearly half a century, and steam reforming of methane remained the main commercial process for synthesis gas manufacture. 

Catalysts were prepared by incipient wetness impregnation of commercial supports using cobalt nitrate as a precursor. Metallic cobalt species were active centers in the ethanol steam reforming. Over 90% EtOH conversion achieved. Nature of support influences the type of byproduct formation. Ethylene, methane and CO are formed over Co supported on A1203, Si02 and MgO, respectively... 

It follows that most work reported over the last few years on steam reforming and methanation has been concerned with nickel catalysts. The following sections will therefore deal mostly with nickel-based catalysts, particularly those which have some importance in commercial practice. Particular stress will be laid on work, with which the author has been associated, concerned with steam reforming and methanation catalysts but mention will also be made of parallel studies from other laboratories. In sections on the catalysts for steam dealkylation and steam reforming of methanol, where catalyst selectivity is a prerequisite, other types of catalyst will also be discussed. 

Other Commercial Catalyst Formulations. Many papers and patents have recently appeared which are also addressed to the problem of maintaining mechanical strength as well as activity and chemical stability during steam reforming and methanation. Hence, only selected examples will be given in the following paragraphs. 

Coke Deposition on a Commercial Nickel Oxide Catalyst During the Steam Reforming of Methane... 

The steam reforming of methane cycle suffers from the problem of coke deposition on the catalyst bed. The primary objective of this project was to study the stability of a commercial nickel oxide catalyst for the steam reforming of methane. The theoretical minimum ratios of steam to methane that are required to avoid deposition of coke on the catalyst at various temperatures were calculated, based on equilibrium considerations. Coking experiments were conducted in a tubular reactor at atmospheric pressure in the range of 740-915°C. 

Steam reforming of hydrocarbons has become the most widely used process for producing hydrogen. One of the chief problems In the process Is the deposition of coke on the catalyst. To control coke deposition, high steam to hydrocarbon ratios, n, are used. However, excess steam must be recycled and It Is desirable to minimize the magnitude of the recycle stream for economy. Most of the research on this reaction has focused mainly on kinetic and mechanistic considerations of the steam-methane reaction at high values of n to avoid carbon deposition ( L 4). Therefore, the primary objective of this studyis to determine experimentally the minimum value of n for the coke-free operation at various temperatures for a commercial catalyst. 

All steam reforming catalysts in the activated form contain metallic nickel as active component, but the composition and structure of the support and the nickel content differ considerably in the various commercial brands. Thus the theoretical picture is less uniform than for the ammonia synthesis reaction, and the number of scientific publications is much smaller. The literature on steam reforming kinetics published before 1993 is summarized by Rostrup - Nielsen [362], and a more recent review is given by K. Kochloefl [422]. There is a general agreement that the steam reforming reaction is first order with respect to methane, but for the other kinetic parameters the results from experimental investigations differ considerably for various catalysts and reaction conditions studied by a number of researchers. 

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