Abstract
The hydrothermal stability of TiO2- and ZrO2-based materials was studied by exposing the samples to liquid water at 523K for 60h in a batch reactor. No phase transformation or loss in BET surface area was observed for TiO2-based materials that had initial BET surface area of less than 52m2/g. In contrast, the BET surface area decreased and the primary crystallite size increased for all ZrO2-based materials tested. The BET surface area decreased and the primary crystallite size increased for high BET surface area TiO2 (156m2/g) and ZrO2 (246m2/g). Silica-containing TiO2 only lost 30% of its high BET surface area (from 128 to 90m2/g). In contrast a material composed of silica–phosphate–ZrO2 lost 56–72% of its BET surface area. Using the crystalline TiO2 as a support, we prepared and tested a Pt–ReOx/TiO2 catalyst for hydrodeoxygenation of sorbitol. Pt–ReOx/TiO2 was almost 2 times more active on a total Pt basis than Pt–ReOx/C catalyst. Between 0.1 and 0.9wt% of coke formed on the catalyst surface after reaction depending on the reaction conditions. The coke could be removed and the catalyst activity completely regenerated by an oxidation-reduction treatment. The catalyst showed only minimal change in BET surface area, TiO2 phase and TiO2 crystallite size after more than 163h of time on stream. The CO chemisorption of Pt–ReOx/TiO2 increased after reaction which was probably due to migration of ReOx species away from the Pt during the reaction.
Published Version
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