催化简介.pptVIP

Advanced principles in catalysisChapter One：Catalysis and Catalysts Yongdan Li Department of Catalysis Science and Technology Catalytic phenomenon 有奖竞猜: 出处? 相关人物? 待月西厢下 迎风户半开 月移花影动 疑是玉人来 Definition of Catalysis A catalyst is a substance that selectively transforms reactants into products, through an uninterrupted and repeated cycle of elementary steps in which the catalyst participates while being regenerated in its original form at the end of each cycle during the life of the catalyst. M. Boudart, Perspectives in Catalysis (J.M. Thomas and K.I. Zamaraev, Eds) Blackwell, Oxford, 1992, p. 183 Definition of Catalysis A catalyst is a substance that increases the rate at which a chemical reaction approaches equilibrium without itself becoming permanently involved in the reaction. James T. Richardson Principles of Catalyst Development Plenum Press, New York and London, 1989 一个催化剂是一种物质，它增加一个化学反应达到平衡的速率，但它本身不永久的牵涉在反应中。 Definition of Catalysis Property Actively involved in the reaction It is a reactant Contact action---No remote superpower Follow all chemical laws Increase the rate of approaching equilibrium Can not change thermodynamic equilibrium Not permanently involved One site catalyze the reaction of many molecules in a sequential manner Example－Ammonia synthesis N2 ＋ 3H2 ? 2NH3 Activation energy for gas phase reaction as high as 57 kcal/mole Catalytic pathway H2 ? 2Ha N2 ? 2Na Na + Ha ? NHa NHa + Ha ? (NH2)a (NH2)a + Ha ? (NH3)a (NH3)a ? NH3 Adsorption of nitrogen is rate limiting step with an activation energy of 12 kcal/mole。 At 500 oC increase the rate of reaction by 1013 times！ Operating conditions: - T : as low as 78 K and as high as 1500 K - P : as low as 10-9 and as high as 103 bar - reactants in gas phase - reactants in polar or non polar solvents - with or without assistance of photons, radiation or electron transfer at electrodes - with pure metals as unreactive as gold or as reactive as sodium - with multicomponent and mu