Synthesis of ethanol from methanol and syngas through an indirect route containing methanol dehydrogenation, DME carbonylation, and methyl acetate hydrogenolysis

An indirect route containing methanol dehydrogenation, DME carbonylation, and methyl acetate hydrogenolysis was used for ethanol synthesis from methanol and syngas. DME was produced stably from the methanol dehydrogenation with a 90% yield over H-ZSM-5 at 453 K under 1 MPa. A cold trap was set behind the methanol dehydrogenation to collect the formed water and unreacted methanol. Rh/Cs2H2SiW12O40 was an excellent catalyst for the DME carbonylation to methyl acetate at 473 K. The selectivity for methyl acetate was very high (> 90%) and raising CO/DME ratio improved the DME conversion. A reaction intermediate similar to the homogeneous Rh-I system could be formed on the Rh/Cs2H2SiW12O40 surface. Cu/CeO2 was an excellent catalyst for the methyl acetate hydrogenolysis to methanol and ethanol at 523 K. Both active Cu0 species and active Cu+ species could be stabilized in the Cu/CeO2 catalyst. When three fixed-bed reactors and one cold trap were linked together to achieve the ethanol synthesis from methanol and syngas, an ethanol selectivity of 91.1% was obtained at a methanol conversion of 47.2% under 1 MPa.