Highly hydrothermal stable carbon-coated Pt/SiO2 catalysts to produce hydrogen via APR of polyols

Abstract

The activity, selectivity and stability of carbon-coated Pt(2.0%)/SiO⁠2 catalysts were investigated for producing hydrogen via the APR of xylitol and sorbitol at 498 K and 29.3 bar using polyol(1%)/water feeds in the 0.6 h⁠−1-2.4 h⁠-1 space velocity (WHSV) range. Two carbon-coated samples were prepared by treating with CH⁠4 at 1173 K for 6 h either SiO⁠2 (catalyst Pt/SiO⁠2-C6) or Pt/SiO⁠2 (catalyst (Pt/SiO⁠2)-C6). Untreated Pt/SiO⁠2 and Pt/ Al⁠2O⁠3 catalysts were also tested in the polyol APR reaction. Catalytic tests performed during 5 h showed that untreated Pt/SiO⁠2 was rapidly destroyed on stream whereas the H⁠2 productivity (mmol H⁠2/g⁠cat h) followed the order (Pt/SiO⁠2)-C6 > Pt/Al⁠2O⁠3 > Pt/SiO⁠2-C6. The hydrothermal stability of carbon-coated catalysts was investigated by performing the APR of xylitol for 72 h. Detailed characterization of spent catalysts by different spectroscopic and physical techniques revealed that the surface area, pore structure and Pt crystallite size distribution of the (Pt/SiO⁠2)-C6 catalyst were not modified on stream. Results showed that highly hydrothermal stable (Pt/SiO⁠2)-C6 catalyst was more active and selective than Pt/Al⁠2O⁠3 catalyst for producing hydrogen via the APR of polyols in the WHSV range investigated.