Mesoporous H3PW12O40-silica composite:: Efficient and reusable solid acid catalyst for the synthesis of diphenolic acid from levulinic acid

Mesoporous H3PW12O40-silica composite catalysts with controllable H3PW12O40 loadings (4.0-65.1%) were prepared by a direct sol-gel-hydrothermal technique in the presence of triblock poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide) copolymer. Powder X-ray diffraction (XRD) patterns and nitrogen sorption analysis indicate the formation of well-defined mesoporous materials. With H3PW12O40 loading lower than 20%, the materials exhibit larger BET surface area (604.5-753.0 m(2) g(-1)), larger and well-distributed pore size (6.1-8.6 nm), larger pore volume (0.75-1.2 cm(3) g(-1)), and highly dispersed Keggin unit throughout the materials. Raman scattering spectroscopy studies confirm that the primary Keggin structure remained intact after formation of the composites. As a novel kind of reusable solid acid catalyst, as-prepared H3PW12O40-Silica composite was applied for the synthesis of diphenolic acid (DPA) from biomass platform molecule, levulinic acid (LA), under solvent-free condition, and remarkably high catalytic activity and stability were observed. (C) 2008 Elsevier B.V. All rights reserved.