Chemical reactions reforming

Chemical reactions (reforming and shift reactions) take place at the anode side, and chemical heat effects represent an important heat source (sink) term for the anode and the fuel channel. 

Powerforming is basically a conversion process in which catalytically promoted chemical reactions convert low octane feed components into high octane products. The key to a good reforming process is a highly selective dual-function catalyst. The dual nature of this catalyst relates to the two separate catalyst functions atomically dispersed platinum to provide... 

In this work, the MeOH kinetic model of Lee et al. [9] is adopted for the micro-channel fluid dynamics analysis. Pressure and concentration distributions are investigated and represented to provide the physico-chemical insight on the transport phenomena in the microscale flow chamber. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-reformer channel. 

P., Detailed characterization of various porous alumina based catalyst coatings within microchannels and their testingfor methanol steam reforming, Chem. Eng. Res. Des., special issue on Chemical Reaction Engineering (2003) submitted for publication. 

In order for a chemical reaction to occur, there must be a collision between the reactants at the correct place on the molecule, the reactive site. That collision is necessary to transfer kinetic energy in order to break old chemical bonds and reform new ones. If the collision doesn t transfer enough energy, no reaction will occur. 

Humidification/Dehumidification Water often is added or removed in fuel cell systems to promote or prevent certain chemical reactions. For some reactions, excess water can help to drive the reaction, while too much requires larger equipment and can even reduce the yield of a reaction or decrease the performance of a fuel cell. Excess water often is utilized to increase the yield of reforming reactions and the water gas shift. 

Reactions 2-1 through 2-3 show the most common chemical reactions that occur in the polluted atmosphere. The reason is that nitrogen dioxide is the strongest absorber of sunlight. At a latitude of 40 the typical turnover lifetime for nitrogen dioxide is about 1.4 min. This means that, every 1.4 min on the average, half the nitn en dioxide molecules are photodissociated (Reaction 2-1) and reformed (Reaction 2-3). No other molecule in smog is so active. 

Attention will be focussed on three typical chemical reaction schemes. For the first illustration, two parallel competing reactions are considered. For instance, it may sometimes be necessaru to convert into a desired product only one component in a mixture. The dehydrogenation of six-membered cycloparaffins in the presence of five-membered cycloparaffins without affecting the latter is one such example of a selectivity problem in petroleum reforming reactions. In this case, it is desirable for the catalyst to favour a reaction depicted as... 

Flexibility regarding the mode of chemical reaction (oxidizing, reducing, steam reforming, cracking)... 

Chemical reactions enhanced by catalysts or enzymes are an integral part of the manufacturing processes for the majority of chemical products. The total market for catalysts and enzymes amounts to 11.5 billion (2005), of which catalysts account for about 80%. It consists of four main applications environment (e.g., automotive catalysts), 31% polymers (e.g., polyethylene and polypropylene), 24% petroleum processing (e.g., cracking and reforming), 23% and chemicals, 22%. Within the latter, particularly the catalysts and enzymes for chiral synthesis are noteworthy. Within catalysts, BINAPs [i.e., derivatives of 2,2 -bis(diphenylphosphino) -1, l -bis-l,l -binaphthyl) have made a great foray into chiral synthesis. Within enzymes, apart from bread-and-butter products, like lipases, nitrilases, acylases, lactamases, and esterases, there are products tailored for specific processes. These specialty enzymes improve the volumetric productivity 100-fold and more. Fine-chemical companies, which have an important captive use of enzymes, are offering them to third parties. Two examples are described here ... 

Count Claude-Louis Berthollet, 1748-1822. French chemist and physician. Professor at the ficole Normale. He collaborated with Lavoisier in his researches and in reforming chemical nomenclature. Bertbollet s Essai de statique chimique emphasized the importance of the relative masses of the reacting substances in chemical reactions. 

A comparison has been made of Platforming and of thermal reforming from the standpoint of yield-octane number relationships, product properties, hydrocarbon types, and with respect to the nature of chemical reactions responsible for improvement of octane number. Comparison is based on studies of thermal reforming in a commercial operation at a Pennsylvania refinery and in a pilot plant on a midcontinent naphtha and in pilot plants and laboratory Platforming on the same stocks. 

Reforming a naphtha to a higher octane rating must involve at least one of the following chemical reactions (a) production of aromatics, (6) production of highly branched paraffins, (c) production of olefins, or (d) lowering the molecular weight of the hydrocarbons in the naphtha. 

The early hydroforming catalysts were a big step forward in directing the chemical reactions of reforming to a desired end—namely, the formation of aromatics. These catalysts, however, were far from perfect. They required frequent regeneration with the attendant high plant investment cost and they fell short in octane number improvement due to a lack of isomerization ability. 

Regardless of how fast a chemical reaction takes place, it usually reaches an equilibrium position at which there appears to be no further change, because the reactants are being reformed from the products at the same rate at which they are reacting to form the products. This position of equilibrium commonly is characterized at a given temperature by a constant K,., called the equilibrium constant (see Chapter 16). The equilibrium constant commonly is measured at several different temperatures for a given reaction, because these values of are related to the Kelvin temperature (T) at which they are measured the relationship is... 

Reforming is the conversion primarily of naphthenes and alkanes to aromatics, but other chemical reactions also occur under commercial conditions. Platinum or platinum/rhenium are the hydrogenation-dehydrogenation component of the catalyst and alumina is the acid component responsible for skeletal rearrangements. 

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