Synergistic effects between Cu and Ni species in NiCu/γ-Al2O3 catalysts for hydrodeoxygenation of methyl laurate

Abstract

Cu was introduced into Ni/γ-Al2O3 to prepare mesoporous NixCuy/γ-Al2O3 catalysts with different Ni and Cu contents. H2-TPR, XRD, BET, H2-TPD, and in-situ XPS were used to study the physicochemical properties of the prepared NixCuy/γ-Al2O3 catalysts. The catalytic performances of NixCuy/γ-Al2O3 catalysts were evaluated by methyl laurate catalytic hydrodeoxygenation (HDO) reaction. The NixCuyO/γ-Al2O3 precursors can be reduced to Ni0, Cu0, and NiCu alloy active species by H2 at 420°C. Formed NiCu alloy can effectively promote the electronic effect between Ni and Cu, and enhance the adsorption and activation abilities of the corresponding catalyst for the reactant molecules. The Ni active sites preferentially catalyzes the decarbonylation/carboxyl (DCO) reaction in the deoxygenation of methyl laurate, while the HDO pathway is predominant on the Cu active sites. The deoxygenation pathway obviously changes from DCO to HDO at the mole ratio of Ni/Cu lower than 3/7, and the main deoxygenation products change from C11 to C12 alkane. At the H2/Oil ratio of 500N, the space velocity (SV) of 1.5 h−1, H2 pressure(P) of 2 MPa, and the reaction temperature of 380°C, the Ni3Cu7/γ-Al2O3 catalyst shows the best methyl laurate DCO properties. And methyl laurate conversion and the main deoxygenation products C11 alkane selectivity can reach 98.3 and 87.4%, respectively. Moreover, Ni3Cu7/γ-Al2O3 catalyst also exhibits good stability.