Characteristics and catalytic properties of glycothermal-derived zirconia supported cobalt catalysts in carbonmonoxide hydrogenation

Abstract

Nanocrystalline ZrO2 have been prepared by the glycothermal method with two different glycols [1,4-butanediol (BG) and 1,5-pentanediol (PeG)] with various Zr concentrations of zirconium n-propoxide (ZNP) solution (20.5 and 29.5 %) in the starting materials. Large surface area zirconias with crystallite sizes of 3-4 nm were obtained. Use of zirconia prepared in 1,4-butanediol with lower amount of Zr content as a support for cobalt catalyst resulted in the highest H2 chemisorption and initial CO hydrogenation activities. Due to the different crystallization mechanism of ZrO2 in the two glycols, the metal-support interaction for the zirconia prepared in 1,4-BG was lower than the ones prepared in 1,5-PeG as shown by lower reduction temperature in the TPR profiles. However, activity of such catalyst decreased sharply resulting in lower steady-state reaction rates than those of 1,5-PeG supported onces. Addition of small amount of Si during ZrO2 synthesis was found to enhance steady-state rates of the cobalt catalysts supported on ZrO2 prepared in 1,4-BG. Commercial zirconia in micron and nano-size were obtained from Aldrich for comparison purposes. The cobalt catalysts supported on commercial nano-size ZrO2 exhibited higher CO hydrogenation activity than that the ones supported on micron-size ZrO2. However, cobalt catalysts supported on ZrO2 prepared by the glycothermal method exhibited the highest activities. There is a possibility to develop the glycothermal derived ZrO2 as cobalt catalyst supports for CO hydrogenation, however, the type of the glycol and Zr concentration must be carefully chosen in order to prepare high activity Co/ZrO2 catalysts