Catalytic prepn. of methanol from synthesis gas contg. hydrogen@, carbon mon:oxide and carbon di:oxide - by sepg. methyl formate from prod. and feeding back to reactor to increase yield

摘要

In the catalytic prepn. of methanol from synthesis gas contg. hydrogen, carbon monoxide and carbon dioxide at 220-300 deg. C and at 20-120 bar pressure to give a methanol-contg. vapour. The vapour is drawn off and cooled to 20-60 deg. C giving a condensate contg. water, methanol and methyl formate and a gaseous mixture of hydrogen, carbon monoxide and carbon dioxide which is fed back to the reactor. A methyl formate-contg. fraction with 10-100 wt.% of methyl formate is sepd. from condensate and fed back to the reactor and mixed with synthesis gas. The methyl formate fraction is sprayed into the synthesis gas as a fluid. The methyl formate fraction is heated to 170-240 deg. C by the synthesis gas before being fed to the reactor. The fraction contains at least 30 wt.% of methyl formate, and is sepd. by distn. under pressure of 1-7 bar. The synthesis gas may have methyl formate from an extraneous source added before it enters the reactor. The methyl formate reacts with excess hydrogen to give further methanol. ADVANTAGE - Makes better use of the synthesis gas, giving increased yield of methanol. In an example, a synthesis gas contg. 3 vol.% CO2, 10 vol%CO, 70 vol% H2 and 17 vol% of CH4+N2 was reactred in a reactor (2) at 250 deg. C and 50 bar in the presence of a copper-zinc catalyst. A condensed product contg. 85.94 g of methanol and 0.65 g of methyl formate per hour was obtained and fed to a distillation column (17) working at 60 deg. C. The vapour produced was cooled to 20 deg. C giving a fluid product contg. 30 wt.% of methyl formate which was pumped (19) back to the synthesis gas line (1). Methanol prodn. rose to 86.65 g/h.