催化剂Catalysis

催化剂与反应物形成中间体，把一步高能垒的反应变成若干低能垒的步骤。由阿伦尼乌斯方程 k = A·e^(−Ea/RT)，活化能降低几十 kJ/mol 就可使速率增大数百万倍。催化剂同等程度加快正逆反应，因此只缩短达到平衡的时间，平衡常数不变。催化剂还具有选择性，同一反应物用不同催化剂可得到不同产物。

The catalyst forms intermediates with the reactants, replacing one high barrier with several lower ones. By the Arrhenius equation k = A·e^(−Ea/RT), lowering Ea by a few tens of kJ/mol can raise the rate millions of times. Forward and reverse reactions speed up equally, so the catalyst only shortens the time to equilibrium without changing K. Catalysts are also selective: different catalysts can turn the same reactants into different products.

1835 年瑞典化学家贝采利乌斯总结了多种“只需存在就能引起反应”的现象，提出 catalysis 一词（希腊语“解开”）。1894 年奥斯特瓦尔德给出现代定义：催化剂改变反应速率而不出现在最终产物中，并指出它不能改变平衡，他因催化与平衡研究获 1909 年诺贝尔化学奖。

In 1835 the Swedish chemist Berzelius gathered several cases of substances that cause reactions merely by being present and coined catalysis, from the Greek for loosening. In 1894 Ostwald gave the modern definition: a catalyst changes the rate without appearing in the final products and cannot shift an equilibrium. He received the 1909 Nobel Prize in Chemistry for work on catalysis and equilibrium.

按物相分为均相催化（如酸催化酯化、威尔金森催化剂）和多相催化（如合成氨的铁催化剂、汽车尾气三效催化剂）；酶是高效专一的生物催化剂。20 世纪以来，齐格勒-纳塔催化剂（1963 年诺贝尔奖）、不对称催化（2001 年）、烯烃复分解（2005 年）、钯催化偶联（2010 年）和有机小分子催化（2021 年）多次获诺贝尔奖。约 90% 的化工过程使用催化剂。

By phase, catalysis is homogeneous (acid-catalysed esterification, Wilkinson's catalyst) or heterogeneous (the iron catalyst for ammonia, three-way catalytic converters); enzymes are highly efficient, specific biological catalysts. Ziegler–Natta catalysts (Nobel 1963), asymmetric catalysis (2001), olefin metathesis (2005), palladium-catalysed coupling (2010) and organocatalysis (2021) have all won Nobel Prizes. About 90% of chemical processes use catalysts.