什麼是催化劑

化學術語，能增加反應速率而其本身並不消耗的一種物質（參閲catalysis）。一個催化劑分子可在一分鐘內轉化成好幾百萬個反應物分子。氣態、液態和固態的催化劑可能是無機化合物、有機化合物，或是複雜的化合物。通常，催化作用是催化劑與一種反應物之間進行化學反應，生成一些中間化合物，它們互相之間或與另一反應物以更快的速度反應，生成所需最終產物。在中間化合物和反應物進行反應的過程中，催化劑一般能夠再生。催化劑和反應物之間的反應方式很不相同，使用固體催化劑時更為複雜。典型的催化反應有︰酸－礆反應，氧化－還原反應，生成配位錯合物和生成自由基的反應。來自反應物或反應本身產生的物質會抑制（降低）催化劑的效能。催化劑對所有的工業化學反應非常重要，特別是在提煉原油和合成有機化學制造方面。大部分的固體催化劑是細粒狀過渡元素（金屬）或它們的氧化物。在汽車的催化轉換器中，鉑催化劑把未能燃燒掉的烴和氮化合物轉化成不會對環境造成傷害的產物。水（特別是鹽水）會促進氧化和腐蝕。是已知最活躍和最易被挑選的催化劑。

catalyst

Any substance of which a small proportion notably affects the reaction rate of a chemical reaction without itself being changed or consumed (see catalysis). One molecule may transform several million reactant molecules a minute. Gaseous, liquid, or solid, catalysts may be inorganic compounds, organic compounds, or complex combinations. They tend to be highly specific, reacting with only one substance or a small set of substances. Substances that alter them or block reactants' access to them may inhibit (poison) them. Catalysts are essential to virtually all industrial chemical reactions, especially in petroleum refining and synthetic organic chemical manufacturing. Most solid catalysts are fine-grained transition elements (metals) or their oxides. In a car's catalytic converter, the platinum catalyst converts unburned hydrocarbons and nitrogen compounds to products harmless to the environment. Water, especially salt water, catalyzes oxidation (see oxidation-reduction) and corrosion. Enzymes are among the most active and selective catalysts known.