Steam reforming, of methane

Methane. The largest use of methane is for synthesis gas, a mixture of hydrogen and carbon monoxide. Synthesis gas, in turn, is the primary feed for the production of ammonia (qv) and methanol (qv). Synthesis gas is produced by steam reforming of methane over a nickel catalyst. 

I.V. Yentekakis, Y. Jiang, S. Neophytides, S. Bebelis, and C.G. Vayenas, Catalysis, Electrocatalysis and Electrochemical Promotion of the Steam Reforming of Methane over Ni Film and Ni-YSZ cermet Anodes, Ionics 1, 491-498 (1995). 

Discuss the importance of the steam-reforming process for the production of hydrogen and synthesis gas. Is this process endothermic or exothermic What is the rate-limiting step for the steam reforming of methane ... 

Tong, J. et al., Experimental studies of steam reforming of methane in a thin Pd-based membrane reactor, Ind. Eng. Chem. Res., 44, 1454, 2005. 

De Maria, G. et al., Thermochemical conversion of solar energy by steam reforming of methane, Energy, 11, 805, 1986. 

Boehmer, M. et al., Solar steam reforming of methane, Proc. Bienn. Congr. Int. Sol. Energy Soc., Pergamon, Oxford, 823,1992. 

Berman, A., Karn, R., and Epstein, M., Steam reforming of methane on Ru-catalysts for solar hydrogen production, Abstracts of 232 ACS National Meeting, Paper FUEL-140, Amer. Chem. Soc. San Francisco, CA, 2006. 

Yokota, O. et al., Steam reforming of methane by using a solar simulator controlled by H20/ CH4 = 1/1, Appl. Organomet. Chem., 14,867,2000. 

Reijers, H.Th.J., S.E.A. Valster-Schiermeier, P.D. Cobden, and R.W. van den Brink, Hydrotalcite as C02 Sorbent for Sorption-Enhanced Steam Reforming of Methane, ECN Report RX-05-122, July 2005. 

Uemiya, S., N. Sato, H. Ando, T. Matsuda, and E. Kikuchi, Steam reforming of methane in a hydrogen permeable membrane reactor, Appl. Catal., 67,223-230,1991c. 

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. 

The principle of Le Chatelier shows that when the pressure applied to a gaseous system is increased, the equilibrium composition will change in order to reduce the number of gaseous molecules. In the case of the steam reforming of methane, the partial pressures of methane and steam will increase as the pressure is increased. In the water-gas reaction, where the number of molecules is the same on both sides of the equation, the effect of increasing... 

The reaction shown above for the steam reforming of methane led to the formation of a mixture of CO and H2, the so-called synthesis gas. The mixture was given this name since it can be used for the preparation of a large number of organic species with the use of an appropriate catalyst. The simplest example of this is the coupling reaction in which methane is converted to ethane. The process occurs by the dissociative adsorption of methane on the catalyst, followed by the coupling of two methyl radicals to form ethane, which is then desorbed into the gas phase. 

Electropox [Electrochemical partial oxidation] Also called Pox. An electrochemical process for oxidizing methane to syngas. It combines the partial oxidation and steam reforming of methane with oxygen separation in a single stage. Invented in 1988 by T. J. Mazanec at BP Chemicals. An industrial-academic consortium to develop the process was formed in 1997. 

SMART H2 [Steam Methane Advanced Reformer Technology] A process for making hydrogen by the steam reforming of methane. It differs from similar systems in housing the catalyst within a proprietary heat exchanger. Developed by Mannesmann KTI in 1996 it was planned for installation in Salisbury, MD, in late 1997. 

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. 

Ethanol and methane steam reforming reactions were studied assuming that the exit composition of the ethanol reformer depends on the steam reforming of methane. The competition for the same active site for ethanol and methane reforming maximizes the H2 and C02 production and minimizes the CO formation Catalysts were prepared by incipient wet impregnation. 20 wt% Ni supported on ZnO exhibited better performance compared to that supported on La203, MgO and A1203... 

In some applications water-gas-shift (WGS) is coupled with other reactions. For example, the steam reforming of methane to produce hydrogen is one example where both the forward and reverse reaction may be involved. However, this reaction is accomplished at high temperatures and the reaction is usually considered to be at equilibrium at the high temperatures used. In the following these high temperature processes will not be covered only those instances where the WGS reaction is the dominant reaction that is used to produce and/or purify hydrogen is considered. 

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