Effects of indium on Ni/SiO2 catalytic performance in hydrodeoxygenation of anisole as model bio-oil compound: Suppression of benzene ring hydrogenation and C–C bond hydrogenolysis

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SiO2-supported monometallic Ni and bimetallic Ni-In catalysts were prepared and used for hydrodeoxygenation of anisole, which was used as a model bio-oil compound, for BTX (benzene, toluene, and xylene) production. The effects of the Ni/In ratio and Ni content on the structures and performances of the catalysts were investigated. The results show that In atoms were incorporated into the Ni metal lattice. Although the Ni-In bimetallic crystallites were similar in size to those of monometallic Ni at the same Ni content, H2 uptake by the bimetallic Ni-In catalyst was much lower than that by monometallic Ni because of dilution of Ni atoms by In atoms. Charge transfer from In to Ni was observed for the bimetallic Ni-In catalysts. All the results indicate intimate contact between Ni and In atoms, and the In atoms geometrically and electronically modified the Ni atoms. In the hydrodeoxygenation of anisole, although the activities of the Ni-In bimetallic catalysts in the conversion of anisole were lower than that of the monometallic Ni catalyst, they gave higher selectivities for BTX and cyclohexane as a result of suppression of benzene ring hydrogenation and C–C bond hydrogenolysis. They also showed lower methanation activity. These results will be useful for enhancing carbon yields and reducing H2 consumption. In addition, the lower the Ni/In ratio was, the greater was the effect of In on the catalytic performance. The selectivity for BTX was primarily determined by the Ni/In ratio and was little affected by the Ni content. We suggest that the performance of the Ni-In bimetallic catalyst can be ascribed to the geometric and electronic effects of In.