Study on Highly Active Catalysts and a Once-Through Process for Methanol Synthesis from Syngas

摘要

Highly active CNT-promoted co-precipitated Cu-ZnO-Al_2O_3 catalysts, symbolized as Cu_iZn_jAl_k-x%CNTs, were prepared, and their catalytic activity for once-through methanol synthesis from syngas was investigated. The results illustrated that, under the reaction conditions (at 493 K, 5.0 MPa, the volume ratio of H_2/CO/CO_2/N_2= 62/30/5/3, GHSV= 4000 h~(-1), the observed single-pass CO-conversion and methanol-STY over a Cu_6Zn_3Al_1-12.5%CNTs catalyst reached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h·g)) over the corresponding CNT-free catalyst, Cu-6Zn_3Al_1, respectively. The characteristic studies of the catalysts revealed that appropriate incorporation of a minor amount of the CNTs into the Cu_iZn_jAl_k brought about little change in the apparent activation energy of the methanol synthesis reaction, however, led to a considerable increase in the catalyst's active Cu surface area and pronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on the surface of the functioning catalyst, which would be favorable to increasing the rate of the CO hydro-genation reactions. Moreover, the operation temperature for methanol synthesis over the CNT-promoted catalysts can be 10-20 degrees lower than that over the corresponding CNT-free contrast system, which would contribute considerably to an increase in equilibrium CO-conversion and CH_3OH-yield.