2004年化学反应工程期末考试参考答案（英文）.doc

2004年化学反应工程期末考试参考答案 A. Choose one of the four answers (5 points for each one, 25 points in total) 1. Activation energy might be taken as an indication of ( C ) A the difficulty of a reaction. B the complicacy of a reaction. C the temperature sensitivity of a reaction. D the energy of the reactant absorbed or exhausted. 2. Based on what model and boundary conditions, the dimensionless mean residence time ( C ) A Tank in series model B The dispersion model with closed boundary conditions C The dispersion model with open boundary conditions D None 3. Within three coefficients concerning about diffusion, ①dispersion coefficient, ②molecular diffusion coefficient and ③Knudsen diffusivity, if we sort them from large to small, the suitable order is ( D ) A ③>②>① B ③>①>② C ②>①>③ D ①>②>③ 4. For the reaction A→R, second order kinetics, proceeds in a batch reactor, the final concentration of A is 0.01 mol/l. If the initial concentration CA0 is 1 mol/l, it takes 283[sec]. If the initial concentration CA0 is 5 mol/l, it takes 285[sec]. How long we need if the initial is 5 mol/l and final is 1 mol/l? ( A ) A 2 [sec] B 10 [sec] C >10 [sec] D Between 2 and 10 [sec] 5. A gas-phase reaction 2A+B→C, starting with 50% A, 25% B and 25% inert, the expansion factor εA is ( C ) A -1 B 1 C -0.5 D 0.5 B. A liquid-phase reaction A+B→products is conducted in an isothermal batch reactor. The reaction is first order with respect to each reactant, with kA=0.025 Lmol-1s-1, CA0=0.5molL-1, and CB0=1.0molL-1. Determine the time required for 75% conversion of A. (20 points) C. For a mixed flow reactor of volume 6m3 operating with a steady-state (liquid) feed rate of 0.4m3 min-1, what fraction of the exit stream (i) is of age less than 10 min? (ii) has been in the tank longer than 30 min? (20 points) D. A reaction A→R is to take place on a porous catalyst pellet (dp=6 mm, De=10-6m3/m.cat.s ). How much is the rate slowed by pore diffusional resistance if the concentration of reactant bathing the particle is 100 mol/m3 and the diffusion-free kinetics are given by (20 points) Choose one of the following two problems to solve as you like, don’t choose both. E. To deduce the residence time distribution for a mixed flow reactor. (15 points) F. The reaction takes place in a mixed flow reactor. Determine the optimal space time and the maximal concentration of main product R. (15 points) 第 4 页