Mechanistic Studies of Catalytic Methanol Synthesis. Final Report

摘要

The catalytic methanol production on a Cu-Zn-oxide catalyst was studied at 17 atm and about 200 C in a batch reactor. The initial rate measurement was performed for different CO sub 2 /CO ratios in the feed. The rate was found to increase with increasing CO sub 2 /CO, for a fixed H sub 2 partial pressure. This behavior was observed for catalysts at different stages of deactivation, and from 195 to 225 C. Addition of a small amount of water vapor greatly suppressed the rate. When C exp 18 O sub 2 was used in a feed of CO sub 2 :CO:H sub 2 = 3:10:20, the initial rate of production of methanol- exp 18 O was found to be about half the rate of production of methanol- exp 16 O. In view of the much lower partial pressure of CO sub 2 than CO in the feed, this result suggests that the hydrogenation rate of CO sub 2 on a per mole basis is faster than that of CO. This is consistent with the above initial rate data. Production of C exp 16 O exp 18 O and C exp 16 O sub 2 were also rapid, which indicated rapid exchange of the lattice oxygen with CO sub 2 . The production of H sub 218 O was also rapid, being about twice as fast as the methanol production rate. Thus under the conditions of initial rate measurements, the water-gas shift reaction is rapid. The relative rates of hydrogenation of CO sub 2 and CO were also determined near chemical equilibrium by the relaxation method. Nonequilibrium thermodynamic theories were applied to describe the relaxation process. The physical meaning of the equilibrium exchange rate for a complex reaction was discovered. A method was developed to mesure the equilibrium exchange rates of the simultaneous reactions in methanol synthesis. 18 references, 4 figures, 3 tables. (ERA citation 09:022112)