ALCOHOL SYNTHESIS FROM SYNGAS OVER NICKEL-CATALYSTS - EFFECT OF COPPER AND LITHIUM ADDITION

Carbon monoxide hydrogenation at 5 MPa was investigated on silica-supp orted Ni, Ni-Cu, Ni-Li and Ni-Cu Li catalysts, with special focus on C 2+OH formation. Copper addition does not result in formation of higher alcohols while lithium does. Over Ni-Cu Li/SiO2, selectivities toward s alcohols as high as 85% are observed and higher alcohols such as eth anol and propanol were effectively produced. Addition of copper to nic kel results in a remarkable stabilization of the catalytic activity wh ile lithium promotion increases aging of the catalyst significantly. I nfrared spectroscopy of adsorbed carbon monoxide shows that copper add ition inhibits subcarbonyl formation (Ni(CO)x, x = 2 or 3) and increas es the relative abundance of linear species. When lithium promoter is added to Ni/SiO2, some is deposited on the silica support whilst the r emaining decorates the metal particles. Subcarbonyl species are stabil ized by lithium addition. The spectra obtained over Ni-Cu-Li/SiO2 are practically composed of only two bands, subcarbonyl and linear. By com paring catalytic pattern and infrared data it is concluded that the pr esence of subcarbonyl species is related to catalyst aging and that ac tive sites for C2 + OH formation are, either isolated nickel atoms ass ociated with Li+, or linked to subcarbonyl formation.