Kataliz: Versiyalar orasidagi farq

Kontent oʻchirildi Kontent qoʻshildi
yangi
 
kTahrir izohi yoʻq
Qator 1:
[[File:Verbrennung eines Zuckerwürfels .png|thumb|300px|Chapda: qisman karamellashgan [[qand]], oʻngda: qandni kul bilan yondirilmoqda (bu yerda kul - katalizator).]]
'''Kataliz''' katalizator, deb ataluvchi modda vositasida [[kimyoviy reaksiya]] tezligining oʻzgarishidir. Reaksiyada ishtirok etayotgan [[reagent]]lardan farqli oʻlaroq, katalizator reaksiyaga kirishmaydi. Reaksiyani tezlatuvchi katalizatorlar musbat katalizator, sekinlatuvchilari esa ''ingibitor'' deyiladi. Katalizator faolligini oshiruvchi moddalar ''promouter'', kamaytiruvchi moddalar esa ''katalitik zahar'', deb ataladi.
 
Catalytic reactions have a lower rate-limiting [[free energy (thermodynamics)|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 catalyst]]s for reactions of [[carbonyl]] compounds, or form specific intermediates that are not produced naturally, such as osmate [[ester]]s in [[osmium tetroxide]]-catalyzed [[dihydroxylation]] of [[alkene]]s, or cause [[lysis]] of reagents to reactive forms, such as [[atomic hydrogen]] in [[catalytic hydrogenation]].
 
[[Chemical kinetics|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. A [[Nanomaterial-based catalyst]] is an example of a heterogeneous catalyst. Analogous events associated with [[substrate (chemistry)|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, typical secondary processes include [[coking]] where the catalyst becomes covered by [[polymer]]ic side products. Additionally, heterogeneous catalysts can dissolve into the solution in a solid–liquid system or evaporate in a solid–gas system.