Preparation Of Ru-based Catalyst Supported On Graphitic Carbon By Carbothermal Reduction And Its Catalytic Hydrogenation Performance

As a liquid organic hydrogen storage(LOHC)material,N-ethylcarbazole(NEC)has a relatively high mass hydrogen storage density of 5.79 wt%and has good application prospects in the field of hydrogen storage.Hydrogenation reaction is one of the important links of NEC hydrogen storage,and the development of efficient hydrogenation catalysts is the key to improve NEC hydrogenation.The supported Ru NPs catalysts showed high catalytic activity in the hydrogenation of aromatic compounds.It has a wide range of applications in the fields of chemical materials,pharmaceuticals,and LOHC.In this paper,a series of Ru-based catalysts were prepared by wet impregnation-carbothermic reduction method with biochar(BC)as the support and reducing agent without any other chemical reducing agents and stabilizers.The structure,morphology and surface properties of the catalysts were characterized by N₂ physical adsorption,XRD,Raman,H₂-TPR,XPS,TG and TEM.Using NEC hydrogenation reaction as probe reaction,the effects of catalyst preparation and hydrogenation reaction conditions on the catalytic performance were investigated.The hydrogenation of benzyltoluene(MBT)was used as the model reaction to investigate the adaptability of the catalysts.A highly active and ultra-stable partially graphitized bio-carbon supported Ru nanocatalysts(Ru/pg-BC)were prepared by wet-impregnation carbothermal reduction method using Ru Cl₃·3H₂O as the ruthenium source,and biomass charcoal as the carrier and reducing agent.When the reduction temperature is 550?and the reduction time is2 h,the average particle size of Ru NPs in Ru/pg-BC catalyst is only 2.97.In the NEC hydrogenation reaction,the interaction between Ru NPs and pg-BC significantly improve the catalytic performance of Ru/pg-BC.Under the reaction conditions of 130?and 6Mpa,the NEC conversion was 100%and the 12H-NEC selectivity was 99.41%at 70 min.After the catalyst is recycled 9 times,it can still maintain 100%NEC conversion rate and92.54%12H-NEC selectivity.Partially graphitized bio-carbon supported Ni-Ru alloy catalysts(Ni-Ru/pg-BC)were prepared by wet-impregnation carbothermic reduction method using Ru Cl₃·3H₂O and Ni(NO₃)₂·6H₂O as precursors.The average particle size of Ni-Ru alloy in Ni-Ru/pg-BC is only 2.80 nm.The introduction of Ni can make H₂ more easily activated,resulting in a hydrogen overflow effect,which is beneficial to the continuous conversion of adsorbed NEC molecules into 12H-NEC.The electron transfer between Ru and Ni makes the alloy catalysts exhibit higher catalytic performance than that of pure Ru in NEC hydrogenation.The Ni-Ru/pg-BC catalyst can still maintain 100%NEC conversion and93.47%12H-NEC selectivity after 10 cycles.N-doped partially graphitized bio-carbon supported Co@Ru core-shell structure bimetallic catalyst(Co@Ru/NGC)was prepared by wet-impregnation carbothermal reduction method using Ru Cl₃·3H₂O and Co(NO₃)₂·6H₂O as precursors,and urea as nitrogen source.The average particle size is about 8.69 nm and the thickness of the core layer is about 5.0 nm.Co@Ru retains the catalytic ability of Ru to a large extent and the formation of NGC further improves various properties of the material.At 130?,6 MPa and 60 min,NEC can be completely converted,the 12H-NEC selectivity is 99.1%and the apparent activation energy of NEC hydrogenation is only 43.05 k J/mol.The results showed that the carbothermic reduction method was a simple and green technology used to prepare a partially graphitized biomass carbon-supported Ru-based catalysts.The graphitization of BC is carried out simultaneously with the reduction of the metal,which enhances the interaction between the support and the metal.The intermetallic synergy in Ni-Ru alloys and Co@Ru core-shell catalysts can lead to the hydrogen spillover effect,making the catalysts exhibit higher catalytic performance than that of monometal.Carbothermic reduction can make the generated metal nanoparticles embedded in the depressions formed by the loss of carbon on the surface of the carrier,which greatly enhances the stability of the catalysts.This method provides a useful reference for the preparation of catalysts with higher stability.