Highly durable Pt-supported niobia-silica aerogel catalysts in the aqueous-phase hydrodeoxygenation of 1-propanol

The aqueous-phase hydrodeoxygenation (APHDO) of 1-propanol at 230 degrees C and 35 bar was studied over 1 wt.% Pt catalysts supported on several metal oxides. Pt catalysts supported on amorphous silica, alumina and niobia aerogels, and crystalline niobic acid calcined at 500 degrees C showed low activities or deactivation. Under the APHDO condition, these supports experienced a structure transformation to crystalline quartz, boehmite and niobia TT phase. Pt/Nb2O5-Al2O3 aerogel also suffered from the same crystallization behavior. In contrast, Pt/Nb2O5-SiO2 aerogels with different Nb/(Nb + Si) ratios maintained a good catalytic performance for prolonged reaction periods. Through characterizations of spent catalysts, Nb2O5-SiO2 aerogels were found to retain X-ray amorphous and porous structure. Also, their acid site densities were negligibly changed during the reaction. The catalysts with the Nb/(Nb + Si) ratio of 0.500 and 0.575 reached the molar propane/ethane ratio of about 1.0, indicating that Pt/Nb2O5-SiO2 aerogel catalysts are highly active in the presence of water. (C) 2012 Elsevier B.V. All rights reserved.