卡持动力学方程的讨论 方程可重写为： 2MRDCot= -[1+(z-1)y]2/3 apro 2 z-1 -(1-y)2/3 固体颗粒完全反应时，=1，令所需时间为T,则： 2MRDCo 2-z2/3 apro 2 = z-1 a)对平板状颗粒， 29:=-r 2029= b)对圆柱形颗粒， 2 MRDCo:=名=（1-21-pn+1-201-p】 zln(z) apro 2 2(2-1) 2MRDCeTY apro 2 2(z-1) ?？?
卡特动力学方程的讨论 方程可重写为： 固体颗粒完全反应时， y=1, 令所需时间为 Tf，则： a) 对平板状颗粒， b) 对圆柱形颗粒， ？？？
1.52商 1.50 148 748e 0.6 柔 1.46 0.7 3+ 1.44 0.8 1.42 1.40 0.9 138 母 1.34 Carter 1.32 1.0 1 20 25 Time,hours mooringue →NiO ae 0.35 o.6 74%8gs 0.7 0.s0 0.8 0.55 Ginstling C.75 0.70 20 25 Fig.7-32.Plotting the kinetics of the reaction Ni+Oz-NiO,ac- cording to Crank-Ginstling and Brounshtein [Carter (1963)]
Carter Ginstling
Summary.A summary of the equations applicable to reactions controlled by diffusion through a nonporous solid product layer is given in Table 7-7. To facilitate evaluation of kinetic data for any value of the fraction reacted, R,the plots of the functions. y-1-(I-R)13 y=[1-(1-R)3]2 y=1-子R-(1-R)23 5-0 are given in Fig.7-35. 03 3 0102304a500780910 Frottion reacted,R Fig.7-35.Plots of different kineties equations
Table 7-7.Kinetic equations applicable to reactions controlled by diffusion through non- porous solid product.Reacting solid has the geometry of a sphere. 1)Jander's equation [l -(1-R)=kr Approximate 2)Crank-Ginstling Applicable to most and Brounshtcin's 1一子R一1-)23=k1 cases although not equation very exact 3)Valensi's equation [1 +(z-1)R]2.3+(z-1)(1-R)2/3 =kt Exact equation. LITERATURE Historical W.J.Mellor,Chemical Starics and Dynamics,London,Longmans,1904. C.F.Wenzel,Lehre ron Verwandrschaf,Dresden,1777.(First studies on rates of chemical reactions;rate of dissolution of metals in acids and the effect of acid concentration.) Introduction S.Glasstone,Textbook of Physical Chemistry,Princeton,Van Nostrand,1946. S.Glasstone and D.Lewis.Elements of Physical Chemistry (2nd ed.).Princeton,Van No- strand,1960. J.C.Jungers,et al.,Cinetique Chimique Appitqude,Paris,Technip,1958. K.J.Laidler,Chemical Kinerics (2nded.),New York,McGraw-Hill,1965. E.A.Moelwyn-Hughs,The Kinetics of Reactions in Solution,Oxford,Clarendon,1947. G.Pannetier and P.Souchay,Chemfcal Kinetics(trans.from French).New York,Elsevier, 1967
Kinetics of solid state reactions Phenomenological description of growth rate:W=kt W n Rate-determining process W=kt 1 chemical (interface)reaction W=k-ti2 112 diffusion through relative thin reactant/product layer W=k-til3 1/13 nucleation n=1:A porous or non-closed product layer is formed when e.g.: Gases are evolved during the reaction Volume differences exist between reactants and products n=1/2:Dense,closed layer is formed:diffusion is rate limiting step Parabolic rate law
Kinetics of solid state reactions Phenomenolo gical description of growth rate: W kt n g g W n Rate-determining process W = k1t 1 chemical (interface) reaction W = k2t1/2 1/2 diffusion through relative thin reactant/product layer W = k3t1/3 1/3 nucleation n = 1: A porous or non-closed product layer is formed when e.g.: – Gases are evolved during the reaction – Volume differences exist between reactants and products Volume differences exist between reactants and products n = 1/2: Dense, closed layer is formed: diffusion is rate limiting step – Parabolic rate law