Reforming process principles

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. 

Steam reforming is the principle process for carbon monoxide and hydrogen production. Steam reforming process is applied for several industrial applications to provide the necessary amount of the synthesis gas. Those industries such as oil refineries, iron and steel manufacturing, methanol and ammonia synthesis, and other several petrochemical industries. The future demand for synthesis gas utilization will increase especially when methanol is used as a combustible fuel in large scale and when compact fuel-cells is used in wider applications. 

Chapter 10 contains a literature survey of the basic fluidized bed reactor designs, principles of operation and modeling. The classical two- and three phase fluidized bed models for bubbling beds are defined based on heat and species mass balances. The fluid dynamic models are based on kinetic theory of granular flow. A reactive flow simulation of a particular sorption enhanced steam reforming process is assessed. 

In chap 11 an overview of the basic designs, principles of operation, and modeling of fixed packed bed reactors is presented. The basic theory is applied to describe the performance of particular chemical processes operated in fixed packed bed reactors. That is, porous media reactive flow model simulations of particular packed bed sorption enhanced steam reforming processes are assessed. 

Including reforming of natural gas. In principle, fuel cells are expected to show the highest overall efficiencies. These are lowered in real plants by the up-stream reforming process, due to losses in the conversion to H2 and the need for preheating of input gases. 

One of the first success of zeolites as catalysts, and the first commercial molecular shape selective catalytic process, was the use of erionite in a post-reforming process named selectoforming (39). Ihis 8 MR zeolite was able, based on the principle of size exclusion, to selectively crack the short chain n-parafiins to produce LPG. To avoid the deactivation by coke NiS was deposited on the zeolite. The erionite based catalyst is generally located at the bottom of the last reactor of the reformer unit and operates then at the reformer pressure, and at the temperature of the last reformer reactor. When more flexibility was to be achieved from the selectoforming, the catalyst is introduced... 

The most important aspects of these three processes are summarized in Table 7.7. Pre- and post-combustion processes, as well as oxy-fuel combustion power qrcles, all give a significant reduction in thermal efficiency, and both material and operative costs for a power plant based on these processes would be quite high. Concerning the C02-capture, membranes can be applied in all the three processes cited. In principle, both polymeric and inorganic membranes can be used to produce clean fuel from a mixture gas (from coal gasification or steam-reforming processes) (Bredesen et al., 2004). From one side, due to their simplicity, flexibility, ability to maintain... 

In principle, the tubular reformer is a steam cracker filled with catalyst. Feed preheaters can also be considered steam crackers, each characterised by a KSF and corresponding olefin yields. As olefins are coke precursors in the steam reforming process, preheaters should be designed for a low KSF or the problem should be eliminated by installation of a prereformer (refer to Sections 1.2.3 and 5.3.4). 

In contrast to pure hydrogen, hydrocarbons are converted in a reforming process, generating a hydrogen-rich reformate gas that can be fed to the fuel cell. Steam reforming, in principle, is an endothermic process that requires an external heat supply. Compared to autothermal reforming, the reformate gas is not diluted with nitrogen. 

The failure of the collaborative approach led to a decision by the ERC to commission a comprehensive review of the response system. The Humanitarian Response Review of August 2005 found major shortcomings in humanitarian preparedness and response, finding that as a sector, protection requires special and urgent attention. Its recommendations focused on three key areas humanitarian leadership, funding, and coordination. These became the three initial pillars of the Humanitarian Reform process, later (p. 304) joined by partnership, linked to the development of the Global Humanitarian Platform Principles of Partnership. 

Many late transition metals such as Pd, Pt, Ru, Rh, and Ir can be used as catalysts for steam reforming, but nickel-based catalysts are, economically, the most feasible. More reactive metals such as iron and cobalt are in principle active but they oxidize easily under process conditions. Ruthenium, rhodium and other noble metals are more active than nickel, but are less attractive due to their costs. A typical catalyst consists of relatively large Ni particles dispersed on an AI2O3 or an AlMg04 spinel. The active metal area is relatively low, of the order of only a few m g . ... 

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 ... 

Work in the [riw] program coincided with a far-reaching reform of European chemicals policy. This opened up extensive opportunities for not only an analytical, but also consultative (interventional) accompaniment of this extensive institutional innovation . For SubChem this was primarily a matter of developing some fundamental correlations and founded (quahtative) arguments regarding possible ecological, health and economic opportunities and risks arising from the EU Commission s proposals for a new chemicals policy. Contributions for operationalisation of the precautionary principle and the economic effects of the REACH process to be expected were particularly in demand. 

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