Preparation and application in the hydrogenation of dimethyl terephthalate of Ru@G-CS catalyst

A series of nitrogen-doped graphene-coated Ru-based catalysts (Ru@G-CS) were prepared using glucose, melamine, and RuCl3 as raw materials in a facile one-step pyrolysis method at 700 degrees C with a varied mass ratio of glucose/melamine in feed. The composition, structure, and surface morphology of these catalysts were characterized with powder X-ray diffraction, Raman spectroscopy, N-2 adsorption-desorption, X-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscope. Characterization results showed that nitrogen in the graphene skeleton can promote the dispersion of Ru, and there was also a strong interaction between nitrogen and loaded Ru. Ru@G-CS(1:4) catalyst (with the mass ratio of glucose/melamine in feed was 1:4) possesses the highest surface area (429 m(2)center dot g(-1)), biggest pore volume (0.45 cm(3)center dot g(-1)) and highly dispersed Ru particles (about 1 nm) that encapsulated in 1-2 layered graphene film. At the same time, the detected w(Ru0)/w(Ru4+) (73.6/26.4), I-D/I-G (1.30) and I-2D/I-G (0.32) reached their maximum in Ru@G-CS(1:4). These catalysts were tested in dimethyl terephthalate (DMT) hydrogenation to 1,4-cyclohexane dimethyl dicarboxylate (DMCD) under mild conditions and compared with those traditional carriers (HZSM-5, Al2O3, MgO, ZnO) supported Ru catalysts. Ru@G-CS(1:4) exhibited high activity and stability at 160 degrees C, 2.5 MPa H-2, m(DMT)/m(Ru)=833, the detected conversion of DMT reached 100% and the selectivity of DMCD remained higher than 98.5% within 4 h. The calculated turnover frequency of each Ru was 233.4 h(-1). More importantly, Ru@G-CS(1:4) could maintain its performance at least in 10 cycles. It was concluded that the electronstructure synergistic effect might be the main reason for the excellent activity and stability of Ru@G-CS(1:4).