催化剂工程(第二讲)全解.ppt

Chapter 1 : Introduction 1.1 Introduction 1.2 Reactors for solid-catalyzed reactions 1.3 reactor design equations-basic definitions Catalysis in modern society 1.1.8.2Heterogeneous catalysis The reasons for this are simple. Homogeneous systems are well-behaved and can be investigated by simple physical methods, e. g. spectroscopically, that allow the detection of intermediates and the investigation of the reaction kinetics. The study of heterogeneous systems requires sophisticated instrumentation. The results are not always conclusive, because the reactions are difficult to reproduce. 1.1.8.2Heterogeneous catalysis Heterogeneous systems have been favored by industrialists because they pose simpler engineering problems. Continuous operations are possible here and separation of reaction products is simple. the gaseous reactants(for instance) are allowed to pass over a solid catalyst where the reaction takes place and products emerge as gases that may be separated and condensed, etc. 1.1.8.2Heterogeneous catalysis Heterogeneous catalysts still account for the production of the major part of petroleum and petrochemical products. They account for all the catalysts could be listed as follows: (1)A heterogeneous catalyst exists in a different phase from the reactant molecules-often as a solid in contact with either a gaseous or liquid reactants. 1.1.8.2Heterogeneous catalysis Adsorption:the binding of molecules to a surface. Absorption: refers to the movement of molecules into the interior of a material. (5)The initial step in heterogeneous catalysis is the adsorption of reactants onto the surface of a catalyst. The surface of metal catalysts are highly reactive in comparison to interior atoms. Interior atoms have fully satisfied bonding interactions with neighbor atoms. Atoms on the surface lack a complete set of bonding partners, and thus can bind and react with other molecules in the environment. 1.1.8.3Enzyme catalysis In general, enzymes are proteins produ