PROPERTIES OF NI/SIO2 CATALYSTS - RELATIONSHIP TO ETHER FORMATION FROM ALCOHOLS

The objective of this study was better understanding of the relationships among structural, chemical, and physical properties of Ni/SiO2 and ether formation in the reaction of alcohols. The primary reactions investigated were those of the conversion of 1-butanol at 1 atm, 160°C and conversion <25%. Further characterization of catalyst acidic/metallic properties was conducted with 1,1-dimethylcyclopropane at 80°C. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of Ni in the various catalysts. Two series of catalysts were investigated: 0.7, 2.7, 4.7, and 8.5 wt% Ni/SiO2 prepared by precipitation of basic NiCO3 on the silica, and 4.8 and 6.0 wt% Ni/SiO, prepared by neutral impregnation with nickel nitrate. Various pretreatment and reduction conditions were investigated; for the 0.7-8.5% series it was found that the temperature of drying prior to reduction /reaction was an important variable. For the 8.5% catalyst, temperature of reduction also became an important factor. Study of the ether formation activities for various catalysts from both series, in conjunction with XPS investigation and 1-1 dimethylcyclopropane reactivity, indicated that the active site for ether formation is an acidic nickel silicate promoted by Ni(0). Ether formation is inversely related to surface-reduced Ni on these catalysts, thus it does not appear that large ensembles of zero-valent nickel play a significant role in the catalysis. © 1991.