Synthesis of large-surface area silica-modified zirconia by the glycothermal method

Abstract

Zirconia has been shown to be effective both as a catalyst and a support [1]. It has been found that zirconia has high catalytic activities for isomerization of olefins [2] and epoxides [3]. Zirconia is an important promoter in the catalytic converter system for automobile control and has been shown to help regulate the redox reaction of the ceria catalyst support. Several methods have been developed to increase the surface area and stabilize the tetragonal phase of zirconia. These include the addition of many different additives such as sulfate [4], potassium [5, 6], or rare earth ions [7–13]. It has been reported that the surface area of zirconia is enlarged by the presence of a small amount of silica in the sol-gel process [14, 15]. However the effect of these additives varied by the preparation method and the amount of additives. Inoue et al. have developed a processing method for zirconia that involve the thermal decomposition of zirconium alkoxides in organic solvents. Large surface area zirconia can be obtained directly without bothersome procedures such as purification of the reactants or handling in inert atmosphere [13, 16]. In this paper, we prepare silica-modified zirconia with high surface area and high thermal stability by the glycothermal method. Zirconium n-propoxide 15 g and an amount of tetraethyl orthosilicate at Si/Zr ratio of 0–0.15 were suspended in 130 ml of 1,4-butanediol and then this mixture was placed in a 300 ml autoclave. The autoclave was purged with nitrogen, and the mixture was heated to 300 ◦C and kept at 300 ◦C for 2 h. After the autoclave was cooled, the obtained product was repeatedly washed with methanol, collected by centrifugation and air-dried. The calcination of the product was carried out in a box furnace for 1 h. Powder X-ray diffraction (XRD) patterns were collected on a Siemens XRD D5000 using Cu Kα radiation and a carbonmonochromator. The crystallite size was calculated by the Scherrer equation from the half-height width of 202 diffraction peak. Scanning electron microscopy mea-