One-pot production of dioctyl ether from 1,2-octanediol over rutile-titania-supported palladium-tungsten catalyst

Abstract

Direct synthesis of dioctyl ether by catalytic reduction of 1,2-octanediol (1,2-OcD) was investigated with various supported catalysts containing W and noble metals. The combination of rutile TiO2 support and Pd with W showed the highest yield of dioctyl ether, up to ca. 45 % (carbon-based). The catalytic activity much depended on the W loading amount, and the amount corresponded to monolayer coverage or more was necessary to obtain good yield. The data at low conversion levels showed that the reaction started with WOx/TiO2-catalyzed dehydration of 1,2-OcD to octanal, which then reacted with 1,2-OcD to give acetal. The stepwise hydrogenolysis of the acetal gave dioctyl ether. The WOx-Pd/TiO2 was significantly deactivated during uses, and the deactivated catalyst even lost the activity in 1,2-OcD dehydration. The characterization results of the used catalyst were not much different from the fresh one with XRD, Raman, NH3-TPD, IR of adsorbed pyridine and XAFS techniques. Metastable minor site on WOx/TiO2 was probably responsible to the catalytic activity.