“catalyst”的概念、定义、翻译、参考文献-科学参考

catalyst

Chemistry

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Catalysts that have the same phase as the reactants are homogeneous catalysts (e.g. enzymes in biochemical reactions or transition-metal complexes used in the liquid phase for catalysing organic reactions). Those that have a different phase are hetereogeneous catalysts (e.g. metals or oxides used in many industrial gas reactions). The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. It thus increases the rate at which the reaction comes to equilibrium, although it does not alter the position of the equilibrium. The catalyst itself takes part in the reaction and consequently may undergo physical change (e.g. conversion into powder). In certain circumstances, very small quantities of catalyst can speed up reactions. Most catalysts are also highly specific in the type of reaction they catalyse, particularly enzymes in biochemical reactions. Generally, the term is used for a substance that increases reaction rate (a positive catalyst). Some reactions can be slowed down by negative catalysts (see inhibition).

Chemical Engineering

A substance that alters the rate of a chemical reaction without itself being consumed. While some catalysts are used in small quantities, such as the use of finely divided platinum in the decomposition of hydrogen peroxide, some catalysts are used in relatively large amounts such as in the Friedel–Crafts reaction:
$C_{6} H_{6} + C_{2} H_{5} \to C_{6} H_{5} C_{2} H_{5} + H C l$

in which anhydrous aluminium chloride catalyst is required to be at least 30 per cent of the mass of benzene feed to be effective.

Biology

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. It thus increases the rate at which the reaction comes to equilibrium, although it does not alter the position of the equilibrium. Enzymes are the catalysts in biochemical reactions; they are highly specific in the type of reaction they catalyse.

单词	catalyst
释义	catalyst Chemistry A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Catalysts that have the same phase as the reactants are homogeneous catalysts (e.g. enzymes in biochemical reactions or transition-metal complexes used in the liquid phase for catalysing organic reactions). Those that have a different phase are hetereogeneous catalysts (e.g. metals or oxides used in many industrial gas reactions). The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. It thus increases the rate at which the reaction comes to equilibrium, although it does not alter the position of the equilibrium. The catalyst itself takes part in the reaction and consequently may undergo physical change (e.g. conversion into powder). In certain circumstances, very small quantities of catalyst can speed up reactions. Most catalysts are also highly specific in the type of reaction they catalyse, particularly enzymes in biochemical reactions. Generally, the term is used for a substance that increases reaction rate (a positive catalyst). Some reactions can be slowed down by negative catalysts (see inhibition). Chemical Engineering A substance that alters the rate of a chemical reaction without itself being consumed. While some catalysts are used in small quantities, such as the use of finely divided platinum in the decomposition of hydrogen peroxide, some catalysts are used in relatively large amounts such as in the Friedel–Crafts reaction: $C_{6} H_{6} + C_{2} H_{5} \to C_{6} H_{5} C_{2} H_{5} + H C l$ in which anhydrous aluminium chloride catalyst is required to be at least 30 per cent of the mass of benzene feed to be effective. Biology A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. It thus increases the rate at which the reaction comes to equilibrium, although it does not alter the position of the equilibrium. Enzymes are the catalysts in biochemical reactions; they are highly specific in the type of reaction they catalyse.
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