Product distribution-tuned and excessive hydrocracking inhibiting in fatty acid deoxygenation over amorphous Co@SiO2 porous nanorattles

Abstract

A type of amorphous Co-based catalyst (Co@SiO2 nanorattles) with porous structure and large surface area was synthesized by chemical grafting, and the performance in deoxygenation of palmitic acid (a model compound of bio-oil) was investigated. Detailed characterization (XRD, TG, BET, SEM, TEM and NH3-TPD) indicated that Co@SiO2 existed in amorphous form and had large specific surface area, rich pore structure and surface acidity. Result showed that amorphous Co immensely inhibited the hydrocracking of the alkane products with higher carbon atom economy than Co/SiO2, Co-n, and Co@γ-Al2O3. It also promoted hydrodeoxygenation (HDO) selectivity and a high ratio of C16/C15 (5.8) at 280 °C. The results also showed that the insufficient hydrogenation would lead to the production of by-products (alcohols and esters), but the excessive hydrogenation would lead to hydrocracking (produce short alkanes and CH4). Therefore, the trade-off between insufficient hydrogenation and excessive hydrogenation over Co@SiO2 is extremely important. Five-cycle test showed that the exposure of Co crystal surface decreased the C16/C15 ratio.