Chemical reaction during catalyst

Ohmic heating of catalyst is often used as a simple method of igniting the chemical reaction during reactor startup, for instance, in the oxidation of ammonia on platinum-rhodium gauze catalysts. Another application is the prevention of cold-start emissions from automotive catalysts responsible for much of the residual pollution still produced from this source (21). The startup times needed for the catalyst to attain its operating temperature can be cut by a factor of 5 or more by installing an electrically heated catalyst element with a metallic support upstream of the main catalyst unit. Direct electrical catalyst heating permits facile temperature control but requires a well-defined catalyst structure to function effectively. 

Other minor uses of antimony include the manufacture of glass and ceramics and the production of plastics. In glass and ceramics, a small amount of antimony insures that the final product will be clear and colorless. In the production of plastics, antimony is used as a catalyst. A catalyst is a substance that increases the rate of a chemical reaction. The catalyst does not undergo any change itself during the reaction. 

The stepwise chemical reactions during hydrogen generation when Co, W, B and P catalysts are used are shown below [10] ... 

In chemical reactions, a catalyst participates in a reaction either to initiate the reaction or influence the rate of the reaction, and it is regenerated during the course of the reaction. Therefore, only a small amount of the catalyst must be used. Enzyme catalyzed reactions are ubiquitous in biological systems. Figure 7.12 shows an energy profile of a catalyzed and an uncatalyzed reac-tion.2 Clearly, the catalyzed reaction is more complex in that it has more steps, but complexation with the enzyme catalysts leads to a lower activation energy, and there is a similarity to Figure 7.1. Indeed, catalysis by an enzyme can... 

As you might imagine, consideration of the acidic or basic character of the solid adsorbent used for a TLC experiment can be particularly important if the substances to be analyzed contain functional groups that are sensitive to acids or bases. In a worst-case scenario, the adsorbent may function as a catalyst to destroy the functionality by chemical reaction during the course of the analysis this greatly complicates the interpretation of the TLC results. 

For most chemical reactions, a catalyst is required to obtain the desired product. The catalyst performance in MRs can be influenced positively or negatively by the use of a membrane. It is well known that the withdrawal of hydrogen during dehydrogenation in an MR will likely favor coking processes, promoting deactivation of the catalyst. This implies that MRs require catalysts with improved stability. However, in the Fischer-Tropsch synthesis, the use of membranes to extract water from the reaction zone may protect the catalyst from... 

In addition to their protein part, most enzymes also contain a small nonprotein part called a cofactor. A cofactor can be either an inorganic ion, such as Zn2+, or a small organic molecule, called a coenzyme. A coenzyme is not a catalyst but is a reactant that undergoes chemical change during the reaction and... 

Catalyst Basically a phenomenon in which a relatively small amount of substance augments the rate of a chemical reaction without itself being consumed recovered unaltered in form and amount at the end of the reaction. It generally accelerates the chemical change. The materials ordinarily used to aid the polymerization of most plastics are not catalysts in the strict sense of the word (they are consumed), but common usage during the past century has applied this name tathem. 

The dimethylbenzenes (xylenes) are very important industrial chemicals recovered during the refining of petroleum. All three xylenes are used to produce the corresponding aromatic dicarboxylic acids by reaction with oxygen over a catalyst. 

The chromium catalyst for polymerization differs from catalysts in other chemical reactions in the sense that it is eventually consumed. During the reaction, the polymer molecules fill up the pores, and exert considerable pressure upon the support. Consequently the catalyst breaks up and remains in a finely dispersed form in the end product. 

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