Hydrothermally stable regenerable catalytic supports for aqueous-phase conversion of biomass
•Crystalline TiO2 materials did not undergo phase transformation.•ZrO2 materials underwent phase transformation and became crystalline.•The Pt–ReOx/TiO2 catalyst showed high activity, stability, and regeneration in the conversion of sorbitol.
The hydrothermal stability of TiO2- and ZrO2-based materials was studied by exposing the samples to liquid water at 523 K for 60 h 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 52 m2/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 (156 m2/g) and ZrO2 (246 m2/g). Silica-containing TiO2 only lost 30% of its high BET surface area (from 128 to 90 m2/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 0.9 wt% 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 163 h 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.
Graphical abstractHydrothermally stable and regenerable Pt–ReOx/TiO2 catalyst was used for aqueous phase hydrodeoxygenation (APHDO) of sorbitol at 518 K and 6.21 MPa.Figure optionsDownload full-size imageDownload high-quality image (54 K)Download as PowerPoint slide
Journal: Catalysis Today - Volume 234, 1 October 2014, Pages 66–74