Reforming Reactions Process Principles

The embedded catalyst synthesized in this way shows higher thermal stability than the traditional catalyst obtained by incipient wetness impregnation. 

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In the sorption-enhanced reforming (SER) process, one of the gaseous reaction products (C02) of the catalytic reforming reaction is separated from the reaction zone by sorption. As a result, the equilibrium of the reaction is shifted toward products according to the Le Chatelier s principle. Balasubramanian et al. [18] studied the SMR reaction in the presence of CaO as a C02 acceptor. Thus, in addition to reactions 2.4 and 2.6, the reaction of C02 with the C02 acceptor (CaO) takes place in the reaction zone ... 

The SPARG (Sulfur Passivated Reforming) principle (ref. 3) allows operation below the carbon limit curve. It was demonstrated (ref. 4) that carbon-free operation could be obtained above a certain sulfur coverage at conditions which would otherwise result in carbon formation. Sulfur passivated reforming as practiced in the Topsoe SPARG process (ref. 5) solves the problem of carbon formation by "ensemble control" which means that the sites for carbon formation are blocked while sufficient sites for the reforming reactions are maintained. This effect is obtained by adding sulfur to the process feed. 

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). 

This review is concerned with a discussion of the reactions of hydrocarbons over bifunctional catalysts, primarily from the viewpoint of mechanism and kinetics. Some discussion will also be given of the structure and properties of typical bifunctional reforming catalysts, since this is somewhat helpful in understanding how the catalyst functions in promoting the various reactions. In addition, at appropriate places in the article, the practical application of the principles of bifunctional catalysis in commercial reforming processes will be considered. 

In principle, geminal radical pairs in polymeric matrices, A... B, can select among a myriad of processes. The empirically observed major modes of reaction and motion, summarized in Scheme 13.1, include (1) recombination to reform their precursor ... 

Methanol and ethanol have been considered as promising fuels for generating H2, especially for on-board fuel cell applications due to their easy availability, ability to transport, and reaction simplicity.52 121 159 169 For example, both alcohols have high H2-to-carbon ratio (H/C) of 4 and 3, respectively (Table 2.1). They could be synthesized from renewable sources such as biomass and thus the ability to close the carbon cycle.161 166 Unlike hydrocarbon fuels, methanol and ethanol are free from sulfur, and this avoids additional sulfur removal step in the fuel processing. In addition, methanol can be reformed at a lower temperature, around 300 °C, and this makes the fuel processing relatively simple and less complicated. Furthermore, unlike natural gas, which produces primarily syngas, reforming of methanol and ethanol can in principle produce a mixture of H2 and C02, and this would also simplify the downstream CO cleanup for fuel cells such as PEMFCs where CO is a poison. 

The concept that the removal of an undesired reaction product by selective adsorption from the reaction zone of an equilibrium-controlled reaction increases the conversion and the rate of formation of the desired component (based on Le Chatelier s principle) was used to develop a novel PSA process concept called SERP for direct production of fuel cell-grade hydrogen by steam reforming of methane (CH4 + 2H20 44 C02 + 4H2).57 61 The concept uses a physical admixture of a reforming (noble metal on alumina) catalyst and a chemisorbent (K2C03 promoted hydrotalcite), which selectively and reversibly chemisorbs C02 from a gas at a temperature of -450 °C in the presence of steam. The cyclic SERP steps consisted of the following ... 

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