h-BN载体对Cs-Ru/h-BN催化合成氨性能的影响OA

NH3 is a crucial inorganic chemical raw material and an ideal hydrogen energy carrier.Ru-based catalysts have attracted significant attention due to their superior catalytic performances under low-temperature and low-pressure conditions compared to traditional iron-based catalysts.xCs-Ru/h-BN(x=n(Cs)/n(Ru))catalysts were synthesized by supporting Ru and the promoter CsNO3 onto four commercial hexagonal boron nitride(h-BN)substrates.The physicochemical properties of the support and catalysts were characterized by XRD,SEM,N2 adsorption/desorption,H2-TPR,and XPS.The catalytic performances for ammonia synthesis of four catalysts under mild conditions were evaluated,and the reaction orders of N2,H2 and NH3 were analyzed through kinetics.The results show that the Ru species on the surface of 2Cs-Ru/h-BN-1 exhibits higher activity,effectively lowering the decomposition and reduction temperatures of CsNO3 and thereby facilitating N2 dissociation on the Ru active sites.Kinetic analysis reveals that the hydrogen reaction order of 2Cs-Ru/h-BN-1 is positive,indicating that the dissociated hydrogen atoms on the catalyst surface are more prone to migration and transformation.This not only suppresses hydrogen poisoning of the catalyst to stabilize ammonia synthesis but also releases more active sites for the dissociation of N2 molecules.Under the reaction conditions of 400℃,0.1 MPa and syngas flow rate of 60 mL/min(V(H2):V(N2)=3:1),2Cs-Ru/h-BN-1 achieves an ammonia synthesis rate(calculated by per gram of catalyst)of 3902 μmol/(g·h)after 1 h of reaction and can operate stably for 48 h.