反应工程课件

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,催,化反应工程,Catalytic Reaction Engineering,李翔,西部校区化工实验楼,B325,Xiang Li B-325, Chemical Engineering Laboratory, Western Campus,Tel,：,84986124,E-mail: lixiang,d,教材和讲义,CRE,王安杰，周裕之，赵蓓,.,化学反应工程学,.,化学工业出版社,O. Levenspiel,Chemical Reaction Engineering,. John Wiley & Sons, Inc. 1999.,3. I. Chorkendorff, J.W. Niemantsverdriet.,Concepts of Modern Catalysis and Kinetics,. WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2003.,2.,Chemical Reaction Kinetics,2.1 Conversion and Molar Fraction,2.2 Rate equation,2.3,The reaction order,2.4,Temperature Dependence of Reaction Rate,2.5,Kinetic theory,2.6,Autocatalytic Reactions,Reaction rate,CRE,2 . 1 Conversion and Molar Fraction,CRE,Conversion,In the Batch Reactor,In the Steady-State Flow Reactor,Molar Fraction,2 . 1. 1 Conversion,CRE,1. In the Batch Reactor,Suppose that,n,A0,is the initial amount of A in the reactor at time,t,=0, and that,n,A,is the amount of A at time,t .,Then the conversion of A in constant volume system is given by,(2.1),(2.2),(2.3),(2.4),(2.5),2 . 1. 1 Conversion,CRE,Suppose that I is an inert, then,：,n,t0,is the initial amount of A in the reactor at time zero,n,t,is the amount of all components at time,t,:,(2.6),(2.7),(2.8),Expansion Factor,：,(2.9),(2.10),Expansion Ratio,：,2 . 1. 1 Conversion,CRE,The Steady-State Flow Reactor,Since the composition in steady-state reactor is uniform throughout, the conversion is given by,：,(2.11),(2.12),2 . 1. 2 Molar Fraction,CRE,Batch Reactor,：,Steady-State Flow Reactor,：,The expressions of molar fraction for he two systems are same,(2.13),(2.14),(2.15),(2.16),(2.17),(2.18),(2.19),例,2.1,CRE,2A + B,2C,在一间歇反应器中进行,C,A0,= 2 kmol,m,-3,，,C,B0,= 5 kmol,m,-3,，,C,C0,=1 kmol,m,-3,，,C,I0,= 10 kmol,m,-3,。其中,I,为溶剂，不参与反应。,假定反应液的密度不变，试求,x,A,= 80 %,时各组分的浓度和摩尔分率。,a =2, b = 1, c = 2,B,= 5/2 = 2.5, ,C,= 1/2 = 0.5, ,I,= 10/2 = 5,例,2.1,CRE,2A + B,2C,在一间歇反应器中进行,C,A0,= 2 kmol,m,-3,，,C,B0,= 5 kmol,m,-3,，,C,C0,=1 kmol,m,-3,，,C,I0,= 10 kmol,m,-3,。其中,I,为溶剂，不参与反应。,假定反应液的密度不变，试求,x,A,= 80 %,时各组分的浓度和摩尔分率。,a =2, b = 1, c = 2,B,= 5/2 = 2.5, ,C,= 1/2 = 0.5, ,I,= 10/2 = 5,例,2.1,CRE,2A + B,2C,在一间歇反应器中进行,C,A0,= 2 kmol,m,-3,，,C,B0,= 5 kmol,m,-3,，,C,C0,=1 kmol,m,-3,，,C,I0,= 10 kmol,m,-3,。其中,I,为溶剂，不参与反应。,假定反应液的密度不变，试求,x,A,= 80 %,时各组分的浓度和摩尔分率。,a =2, b = 1, c = 2,B,= 5/2 = 2.5, ,C,= 1/2 = 0.5, ,I,= 10/2 = 5,例,2.1,CRE,2A + B,2C,a =2, b = 1, c = 2,B,= 5/2 = 2.5, ,C,= 1/2 = 0.5, ,I,= 10/2 = 5,C,B,=,C,A0,B,- (b/a,),x,A, = (2)2.5 (1/2)(0.8) = 4.2,C,c,=,C,A0,c,- (c/a,),x,A, = (2)0.5 (2/2)(0.8) = 2.6,C,I,=,C,A0,I,= 2,5 =10,例,2.1,CRE,2A + B,2C,a =2, b = 1, c = 2,B,= 5/2 = 2.5, ,C,= 1/2 = 0.5, ,I,= 10/2 = 5,A,=,( -2 1 + 2 )/2 = -0.5,y,A0,=,2/,(2+5+1+10)= 0.111,A,= ,A,y,A0,= (-0.5)(0.111) = -0.055,1 + ,A,x,A,= 1 + (-0.0555)(0.8) = 0.956,例,2.1,CRE,2A + B,2C,A,=,-0.5,y,A0,= 0.111 ,A,= -0.055,1 + ,A,x,A,= 0.956,y,A,= (0.111)(1-0.8)/0.956 = 0.0232,y,B,= (0.111)2.5 (1/2)(0.8)/0.956 = 0.244,y,C,= (0.111)0.5 + (2/2)(0.8) /0.956 = 0.151,y,I,= (0.111)(5)/0.956 = 0.581,CRE,Single Reaction,Multiple Reactions,Heterogenous Reactions,2 . 2,Rate Equation,2 . 2 . 1 Single Reaction,CRE,The most useful measure of reaction rate for reactant A is then,The rates of reaction of all components are related by,(2.20),(2.21),(amount of A disappearing),(volume) (time),，,Note that this is an,intensive measure,The minus sign,means disappearance,2 . 2,. 2,Multiple Reactions,CRE,r,iA,is the rate of reaction of material,i.,(2.22),2 . 3 Reaction order,CRE,Power Rate Law,2 . 3 Reaction order,CRE,2.3.1 S,teady,-,state approximation,CRE,c,P,-,t,c,A,-,t,c,B,-,t,c,t,2.4 S,teady,-,state approximation,CRE,The rates of the elementary steps are,：,2A,A,*,+ A,r,1,= k,1,C,A,2,A,*,+ A,2A,r,2,= k,2,C,A*,C,A,A,*,C + D,r,3,= k,3,C,A*,From equation (2.21),：,r,1A*,= (1)r,1,= k,1,C,A,2,r,2A*,= (-1)r,2,= - k,2,C,A*,C,A,r,3A*,= (-1)r,3,= - k,3,C,A*,According to equation(2.22),，,the rate equation of A,*,is,：,r,A*,= r,1A*,+ r,2A*,+ r,3A*,= k,1,C,A,2,- k,2,C,A*,C,A,- k,3,C,A*,To give the,SSA,concentration of A,*,：,k,1,C,A,2,- k,2,C,A*,C,A,- k,3,C,A*,= 0,2.3.1 S,teady,-,state approximation,CRE,with the result,：,From equation (2.21),：,r =(- r,A,)/,1,= r,C,/,1,= r,D,/,1,then,r,C,= (,1,)r,3,= k,3,C,A*,Consistent with equations (a) and (b),：,At high pressure,k,2,C,A,k,3,，,the rate equation becomes,：,Order with respect to A is 1.,r = (k,3,k,1,/k,2,)C,A,(a),(b),At low pressure,k,2,C,A,k,3,，,the rate equation becomes,：,r = k,1,C,A,2,Order with respect to A is 2.,2 . 3 Reaction order,CRE,Catalytic Reactions:,2 . 3 Reaction order,CRE,Catalytic Reactions:,Steady state approximation,2 . 3 Reaction order,CRE,Catalytic Reactions:,2 . 3 Reaction order,CRE,Catalytic Reactions:,If the conversions from adsorbed intermediate into either product or reactant are fast, then catalyst surface will be mostly empty,. In this case the rate expression becomes equal to that of the uncatalyzed,reaction, and the order in the reactant becomes +1.,When the denominator becomes large, the surface is heavily occupied because either the reaction from intermediate to product or the reverse reaction to reactant is slow. the rate has become zero order in R.,2 . 3 Reaction order,CRE,The special case of a pseudo-zero order reaction arises if a reactant is present in large excess, and the reaction does not noticeably change the concentration of the reactant.,Hence, the orders of overall reactions should certainly not be treated,as universal constants,but rather as,a convenient parameterization that is valid for a specific set of reaction conditions,.,2.3.2 The Quasi-equilibrium,A,pproximation,CRE,LangmuirHinshelwood Kinetics:,2.3.2 The Quasi-equilibrium,approximation,CRE,2.3.2 The Quasi-equilibrium,approximation,CRE,2.3.2 The Quasi-equilibrium,approximation,CRE,2.3.2 The Quasi-equilibrium,approximation,CRE,2 . 3 Reaction order,CRE,For overall reactions the rate often cannot be written as a simple power law.,In this case orders will generally assume non-integral values that are only valid within a narrow range of conditions.,This is often satisfactory for the description of an industrial process in terms of a power-rate law. The chemical engineer in industry uses it to predict how the reactor behaves within a limited range of temperatures and pressures.,