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1、Catalysis and Its Reaction Kinetics,By Xuzhude & Jiang XianzhengDepartment of ChemistryZhejiang University,Chapter 1 Introduction and Basic Conception, 1.1 Significance of catalysis to modern chemical industry Some concepts catalysis catalyst catalytic activity catalyzed reaction,The importance of c
2、atalyst,The first catalytic process of industrial significance was developed as early as 1875. It is Platinum (Pt) catalyzed oxidation of SO2 to SO3 which was then converted to sulfuric acid H2SO4There are no such progresses of modern chemical industry without catalysis More than eighty percents (80
3、%) of chemical engineering processes involve catalysis,Several important applied fields of catalysis,Synthesis of Ammonia - a typical illustration for the development of catalyst Fe-Al2O3-K2ON2 + 3H2 2NH3 this reaction almost can not be observed at the atmosphere pressure and room temperature even t
4、hrough its G is negative.BASF first achieved the industrial process of ammonia synthesis in 1910, and won the Nobel prize of 1932.,Several important applied fields of catalysis,Petroleum refiningcatalyzed cracking of crude oil and/or heavy oil to enrich the light oil components. Hydrocarbon with lar
5、ger molecular weight cracks to smaller molecules. SiO2-Al2O3, ZSM-5 zeoliteReforming: converting alkyl hydrocarbon to aromatic hydrocarbon Platinum Pt,Several important applied fields of catalysis,Polymer: Synthesized fiber, robber, and plastic polymerization of olefin (ester, acrylonitrile .) Zeagl
6、er-Natta type catalyst -TiCl4/AlEt3 Production of primary organic chemicalsaminoxidation of propene to acrylonitrile CH2=CHCH3 + NH3 + 1/2O2 CH2=CHCN +3H2O P-Mo-Bi, multi-component catalyst,Several important applied fields of catalysis,Production of primary organic chemicalsaminoxidation of propene
7、to acrylonitrile CH2=CHCH3 + NH3 + 1/2O2 CH2=CHCN +3H2O P-Mo-Bi, multi-component catalyst Oxidation of ethylene to aldehyde CH2=CH2 + 1/2O2 CH3CHO PdCl2 / CuCl2 complexing catalys,Several important applied fields of catalysis,Manufacturing fine chemicals In whole patents involving catalysis issued i
8、n Japan, those dealing with fine chemicals had been increased by about three times, from 7.1 % to 24.8 % during the period of 1975 - 1984. Environment protectionCatalyst for automobile tail gas. Converting NOx and CODesulfurating catalyst for flue gas,Main research interests,Mechanism of catalysisKi
9、netics of catalyzed reactionThe relation between catalytic properties and structure of catalystDeveloping new catalysts and new catalytic techniques,Some frontier research direction,Heterogenelization of homogeneous catalysisCatalysis in C1 chemistry: converting CO, CO2, and CH4 to products of econo
10、mical importanceFilm (membrance) catalysisBiological Enzyme catalysisPhotocatalysis and photosynthesisComputer optimization in catalyst design and preparationSpecialist systemPattern recognitionArtificial intelligence, 1.2 Concept and definition,Catalysis The concept of catalysis is a method of cont
11、rolling the rate and direction of a chemical reactionCatalyst A catalyst is a substance that increases the rate of reaction towards to equilibrium without being appreciably consumed in the process. Catalyst can not change the ultimate equilibrium determined by thermodynamics. Its role is restricted
12、to accelerating the rate of approaching to equilibrium., 1.2 Concept and definition,Catalyzed reactionThe basic concept is that a catalyzed reaction involves the chemisorption of one or more of the reactants onto the surface of the catalyst, rearrangement of the bonding and desorption of the product
13、.In general, catalyst participates in certain intermediate steps of a reaction to alter the reaction pathway and to lower the activation energy, hence increases the reaction rate constant.,catalyst surface reactant A intermediate M product P,Ea M Ea P A, 1.2 Concept and definition,k = Aexp(-Ea/kT)wh
14、en Ea decreases k has got increased In fewer cases, catalyst may also change the magnitude of pre- exponential factor, 1.3 Classification of catalysis,Biological enzyme catalysis2H2O2 2H2O + O2enzymeHomogeneous catalysis CH3COOC2H5 C2H5OH + CH3COOHH2SO4the most important homogeneous catalyst is solu
15、ble transition metal complex, 1.3 Classification of catalysis,Heterogeneous catalysisSolid acidic and basic catalyst CH3OH gasoline ZSM-5 zeolite, acidic 2CH4 + O2 C2H4 + 2H2OMgO, basicSupported catalyst CH4 + H2O CO +3H2 (syngas) Ni/Al2O3Oxide catalyst, insulator or semiconductor CO + H2 CH3OHCuO/Z
16、nOMetal catalyst C6H6 (Benzene) + 3H2 C6H12 (Cyclohexane) Ni, 1.4 Activity, selectivity and life time of catalyst,Activityconversion XA = (nA0 - nA) / nA0 100%nA0: initial quantity of reactantnA: residual reactant at the end of reactionSpace-time yield (especial for solid catalyst)quantity of produc
17、t formed per unit time per unit volume of catalystKmol/hrm3 g/minL, 1.4 Activity, selectivity and life time of catalyst,Selectivity k1 CH3CHO(P) + H2 Cu, 250 CC2H5OH(A) k2 C2H4(B) + H2O Al2O3, 350 C selective factor s = k1/k2selectivity sP = a/p nP / (nA0 - nA) 100% or sP = nP / (nP + nB) 100% here
18、a=1 and p=1 Stoichimetric coefficient Yield y = a/p nP / nA0 100% y = XA sP, 1.4 Example,For the reaction of methanol dehydrogen to methyl aldehyde CH3OH HCHO + H2If the methanol feed rate is 5.0 kmol/hr and the product is 3.8 kmol/hr aldehyde with 0.7 kmol/hr methanol as residual conversion XA XA =
19、 (nA0-nA) / nA0100% = (5.0-0.7) / 5.0100% = 86.0%selectivity sP sp = a/pnP / (nA0 - nA)100% = 3.8 / (5.0-0.7) 100% = 88.4%yield y y = nP / nA0 100% = 3.8 / 5.0 100% = 76.0%, 1.4 Life time of catalyst,deactivation of catalyst A catalyst lose its activity or its selectivity for a wide variety of reaso
20、ns. The causes may be due to: poisoning sulfur compound fouling carbon deposit reduction of active area sintering loss of active species sublimation or migration, 1.5 composition of solid catalyst,2C2H4 + O2 2CH3CHO Pd / SiO2N2 + 3H2 2NH3-Fe / Al2O3 + K2OActive componentPd, -FePromoterK2OSupporterSiO2, Al2O3,
