Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

摘要

Thermal decomposition of formic acid on SiO_2, CeO_2 and γ-Al_2O_3 was studied as an elementary step of reverse water–gas shit reaction(RWGS) over supported Au catalysts. γ-Al_2O_3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al_2O_3: three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al_2O_3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO_2 and H_2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al_2O_3.