Effect of Chelating Agents on the Catalytic Performance of Ni/SiO₂ Catalysts Prepared by Ammonia Evaporation for 2-Methylfuran Hydrogenation

A series of Ni/SiO2 catalysts were prepared by the ammonia evaporation method (AE), the citric acid-complexation ammonia evaporation method (CAE), and the glycine-complexation ammonia evaporation method (GAE), respectively, with NiO loading of 5%. The catalytic performances for hydrogenation of 2-methylfuran (2-MF) to 2-methyltetrahydrofuran (2-MTHF) in vapor-phase were investigated in a fixed-bed reactor. N2 adsorption-desorption, XRD, TEM, H2-TPR, NH3-TPD, XPS, and ICP-OES were carried out to characterize the structure and properties of catalysts. The investigation revealed effect of chelating agents in the ammonia evaporation method on the structure and performance of Ni/SiO2 catalysts. The results showed that the addition of chelating agents modulated the dispersion of Ni species, metal-support interaction, and surface acidity of catalysts. The GAE Ni/SiO2 catalysts exhibited highly dispersed Ni active species, moderate acidity, and strong metal-support interactions, effectively preventing the aggregation of Ni particles. The addition of glycine also introduced N species, which modified the electronic structure of Ni. Under certain reaction conditions (90 °C, 2 MPa, n(H2)/n(2-MF)=6.4, and WHSV = 2.7 h−1), a 2-MF conversion of 99.5% and a 2-MTHF selectivity of 89.5% were achieved. The rapid deactivation occurred on CAE Ni/SiO2 catalyst due to the effective Ni loading decreased and weak metal-support interaction. The AE catalyst possessed more Ni active sites and exhibited high activity, but its highest total acid amount and elevated fraction of moderate acid sites promoted C-O bond cleavage of 2-MF, increasing byproducts and reducing 2-MTHF selectivity.