(15b) Effect of Pt Loading On Enhancing Aldehyde Hydrogenation for One-Step Hydrogenation/Esterification: Model Reaction for Bio-Oil Upgrading

ABSTRACT: Bio-oil is acknowledged as a renewable, sustainable and promising energy alternative for fossil fuels, but there are some issues to deal with before its subsequent use. One is its corrosive nature due to its high content of organic acid and another is its reactive nature due to many unsaturated components such as aldehydes. Combined one-step hydrogenation/esterification (OHE) has been demonstrated a possible approach for bio-oil upgrading, by directly converting the two main reactive components, aldehydes and organic acids, to stable and combustible esters. Bifunctional mesoporous organic-inorganic hybrid silica involving platinum and propylsulfonic acid group (Pt/SBA15-PrSO3H) has been revealed feasible and superior in catalyzing OHE of acetaldehyde and acetic acid, which was employed as a model reaction for catalytic upgrading of bio-oil. But there are still potential and necessity to enhance the catalytic performance of this bifunctional catalyst. In this work, the enhancements of hydrogenation activity over metal sites of the mesoporous hybrid silicas were focused on. It is found that aqueous reduction-deposition by the relatively less efficient reducing agent (HCHO) is promising to prepare Pt nanoparticles into the pores of SBA15 with high dispersion. And further modifications, herein, high temperature treatments with air or H2 were tested. Results showed that both air and H2 treatments enhanced acetaldehyde hydrogenation activity over Pt/SBA15, especially for H2 treatment. Characterization results demonstrated that these treatments lead to more metallic Pt sites and activate hydrogen more efficiently, which were deemed as the main reasons for acetaldehyde hydrogenation activity enhancement. Consequently, it provided guideline for the further enhancement of the bifunctional catalysts (SBA15 functionalized with platinum and sulfonic acid groups). Finally, a new bifunctionalization procedure for this catalyst was proposed for future work aiming at improving the catalytic activity of one-step hydrogenation/esterification.