Promising Ni/Al-SBA-15 catalysts for hydrodeoxygenation of dibenzofuran into fuel grade hydrocarbons: synergetic effect of Ni and Al-SBA-15 support

Abstract

This work has been undertaken with the aim of designing promising noble-metal-free catalysts for efficient hydrodeoxygenation (HDO) of dibenzofuran (DBF) into fuel grade hydrocarbons. For this, various Ni/Al-SBA-15 catalysts with different Si/Al (50, 60, 70 and 80) mole ratios were synthesized and their catalytic performance was tested for HDO of DBF in a batch reactor. The catalysts were systematically characterized using XRD, N₂-adsorption–desorption, Raman, H₂-TPR, NH₃-TPD, XRF, and FESEM techniques. The activity results showed that the HDO of DBF proceeds via hydrogenation of benzene on the Ni sites followed by cleavage of C–O bonds on the acidic sites of the catalyst to yield unsaturated hydrocarbons. Further hydrogenation of unsaturated hydrocarbons on the Ni sites gives bicyclohexane as the major product. Remarkably, a 100% DBF conversion was found for all the catalysts except for Ni/SBA-15 and Ni/Al-SBA-15(80) (Si/Al mole ratio = 80) catalysts, which showed 97.97 and 99.31%, respectively. A significant observation noticed in this study is that the incorporation of Al into Ni/SBA-15 results in an outstanding improvement in the selectivity of the bicyclohexane product. Among the catalysts tested, the Ni/Al-SBA-15(50) (Si/Al mole ratio = 50) catalyst showed the highest efficiency, with superior selectivity of ∼87% for bicyclohexane and ∼96% degree of deoxygenation at 10 MPa, 260 °C and 5 h. The obtained structure–activity results reveal the synergetic effect of Ni and support in HDO of DBF reaction: the concentration of acidic sites has a significant effect on the selectivity of the desired products.