什么是催化

藉添加催化剂而改变化学反应速率（通常是加速）的现象，催化剂通常与反应物作用，但最後会再生，因此量保持不变，不会影响化学反应的平衡情况。催化剂会减少反应物和产物之间的活化能障碍。在两个或两个以上的联立反应中，相同的反应物和化合反应可以得到不同的产物，而且产物的分布受所选用的催化剂影响，催化剂可以选择性地加速其中某一反应。为降低化学反应的速度向反应中添加的另外物质称为抑制剂。在均相催化反应中，催化剂是以分子形式分散在与反应物相同的相中（一般是气相或液相）。而非均相催化反应则是反应物与催化剂在不同的相中，其间被相界面隔开。绝大多数非均相催化剂是固体，而反应物则是气体或液体。非均相（多相）催化一般都是透过至少一种反应物在催化剂表面的化学吸附（与表面形成化学键）来进行的，催化反应的位置就是这吸附层。为了使表面积达到最大，这种催化剂通常是磨成细粉状或是高度透气的固体。催化对现代化工业非常重要。参阅enzyme。

catalysis

Modification (usually acceleration) of a chemical reaction rate by addition of a catalyst, which combines with the reactants but is ultimately regenerated so that its amount remains unchanged and the chemical equilibrium of the conditions of the reaction is not altered. Catalysts reduce the activation energy barrier between reactants and products. When more than one reaction is possible, a catalyst that accelerates only one reaction pathway selectively enhances the creation of its product. Catalysis is inhibited if the reactant or the catalyst is removed or altered by any of several types of agents (inhibitors). Catalysis in a single phase (e.g., in a liquid solution or gaseous mixture) is homogeneous; that in more than one phase (e.g., in a liquid and a solid) is heterogeneous. Chemisorption, a type of heterogeneous catalysis, often involves bonding between the catalyst's solid surface and the reactant, changing the nature of the chemisorbed molecules. To make the accessible surface area as large as possible, such catalysts are finely powdered or highly porous solids. Catalysis is essential to the modern chemical industry. See also enzyme.