Metal oxides are commonly used as support materials in heterogeneous catalytic biofuel reactions due to their high specific surface areas, however, in the supercritical water (SCW) environment large losses of surface area by hydrolysis, sintering, and phase transformations of the support are often seen. In this work, binary oxides consisting of Al-Zr-O, Ti-Al-O, and Ti-Zr-O were prepared by a coprecipitation method and evaluated based on their stability in SCW for their applicability as catalyst support materials. The stability of the binary oxides is compared to commercial gamma alumina, anatase titania, and monoclinic zirconia supports.
Following exposure to SCW at 600°C and 250 bar, the crystal structures of samples were analyzed by X-ray diffraction and specific surface area and pore characteristics were evaluated by the BET method. Water in contact with the samples was checked for dissolution of the oxides by ICP-AES.