lastwords

catalysis

1-1
English German
catalysis subst. die Katalyse f
accesses today: 42 289.966 words in the dictionary accesses total: 48.830

Did you mean:


Catalysis aus Wikipedia. Zum Beitrag

Catalysis - Wikipedia, the free encyclopedia a.new,#quickbar a.new{color:#ba0000} /* cache key: enwiki:resourceloader:filter:minify-css:5:f2a9127573a22335c2a9102b208c73e7 */ Catalysis From Wikipedia, the free encyclopedia Jump to: , "Catalyst" redirects here. For other uses, see Catalyst (disambiguation). Solid heterogeneous catalysts such as in automobile catalytic converters are plated on structures designed to maximize their surface area. A low-temperature oxidation catalyst used to convert carbon monoxide to non-toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air. Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations. Catalysts that speed the reaction are called positive catalysts. Substances that interact with catalysts to slow the reaction are called inhibitors (or negative catalysts). Substances that increase the activity of catalysts are called promoters, and substances that deactivate catalysts are called catalytic poisons. Catalytic reactions have a lower rate-limiting free energy of activation than the corresponding uncatalyzed reaction, resulting in higher reaction rate at the same temperature. However, the mechanistic explanation of catalysis is complex. Catalysts may affect the reaction environment favorably, or bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced naturally, such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause lysis of reagents to reactive forms, such as atomic hydrogen in catalytic hydrogenation. Kinetically, catalytic reactions are typical chemical reactions; i.e. the reaction rate depends on the frequency of contact of the reactants in the rate-determining step. Usually, the catalyst participates in this slowest step, and rates are limited by amount of catalyst and its "activity". In heterogeneous catalysis, the diffusion of reagents to the surface and diffusion of products from the surface can be rate determining. Analogous events associated with substrate binding and product dissociation apply to homogeneous catalysts. Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated, or destroyed by secondary processes. In heterogeneous catalysis, typica... mehr

Catalysis aus Wikipedia. Zum Beitrag


TOP WORDS A B C D E F G H I J K L M N O P Q R S T U V W X Y Z