什麼是催化

藉添加催化劑而改變化學反應速率（通常是加速）的現象，催化劑通常與反應物作用，但最後會再生，因此量保持不變，不會影響化學反應的平衡情況。催化劑會減少反應物和產物之間的活化能障礙。在兩個或兩個以上的聯立反應中，相同的反應物和化合反應可以得到不同的產物，而且產物的分佈受所選用的催化劑影響，催化劑可以選擇性地加速其中某一反應。爲降低化學反應的速度向反應中添加的另外物質稱爲抑制劑。在均相催化反應中，催化劑是以分子形式分散在與反應物相同的相中（一般是氣相或液相）。而非均相催化反應則是反應物與催化劑在不同的相中，其間被相界面隔開。絕大多數非均相催化劑是固體，而反應物則是氣體或液體。非均相（多相）催化一般都是透過至少一種反應物在催化劑表面的化學吸附（與表面形成化學鍵）來進行的，催化反應的位置就是這吸附層。爲了使表面積達到最大，這種催化劑通常是磨成細粉狀或是高度透氣的固體。催化對現代化工業非常重要。參閱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.