(191b) Combined One-Step Hydrogenation/Esterification Over Bifunctional Mesoporous Organic–Inorganic Hybrid Silica: Model Reaction for Bio-Oil Upgrading

Bio-oil is a promising energy alternative for fossil fuels, but its corrosive(high content of organic acid) and reactive nature (many unsaturated components such as aldehydes) necessitates upgrading for its subsequent use. Combined one-step hydrogenation/esterification (OHE) has been demonstrated to be a possible approach for bio-oil upgrading, by stabilizing the two main reactive components, aldehydes and organic acids simultaneously. Supported metallic platinum catalyst and organosulfonic acid functionalized mesoporous silicas are reported to exhibit combined activity for hydrogenation and esterification. In this work, the supported metallic platinum and organosulfonic acid groups were combined to catalyze the OHE reaction of acetic acid and acetaldehyde, which are model compounds for bio-oil.

Different catalyst synthesis procedures were investigated and the textural properties, platinum loading, reducing agent were considered as the factors affecting catalytic performance. A strong thiol-platinum bonding effect was determined to inhibit both the oxidation of thiol groups and the reduction of platinum ions, leading to a reduction in the number of sulfonic acid sites and metallic platinum sites on the catalysts. The characterization and catalytic test results showed that the propyl-thiol groups should be tethered and oxidized to propylsulfonic acid groups before platinum loading to avoid the apparent strong thiol-bonding effect. An aqueous reduction and deposition of platinum with sodium borohydride and ethylene glycol as the reducing agents was the suitable method for bifunctionalization. It was found that the presence of propylsulfonic acid groups did not affect the hydrogenation ability of the platinum sites, while platinum appeared to promote the acidic strength of the propylsulfonic acid groups thereby improving esterification ability. The catalytic test results showed that the conversion of acetaldehyde and acetic acid through the OHE can reach high levels with negligible amount of byproducts, suggesting that this bifunctional hybrid catalyst has potential for improving OHE activity.