Study On SBA-15 Supported Palladium-based And Ruthenium-based Catalysts And Their Catalytic Performanc

Liquid organic hydrogen carrier（LOHC）is regarded as one of the most promising hydrogen storage technologies due to its large hydrogen capacity,high safety and reversible hydrogen storage process.The LOHC system completes hydrogen storage and transportation through hydrogenation and dehydrogenation of unsaturated double bond with aromatic compounds.The system is quite stable during transportation and can take full advantage of existing petroleum facilities.However,due to the limitations of kinetics and thermodynamics,LOHC system has the problems of slow hydrogen storage process and high reaction temperature.Therefore,the development of high performance catalysts is the key to the practical application of LOHC.In this thesis,Pd-based catalysts and Ru-based catalysts were prepared by electrostatic adsorption method with SBA-15 as the carrier.The performance of the catalyst was evaluated by dehydrogenation of dodecahydro-N-ethylcarbazole（12H-NEC）and hydrogenation of N-ethylcarbazole（NEC）as the probe reaction.The effects of metal and support interaction,metal dispersion and bimetal electronic interaction on catalyst performance were systematically studied.Pd/SBA-15 catalyst was prepared by electrostatic adsorption-chemical reduction method using SBA-15 as support.The electrostatic adsorption process between the negatively charged surface hydroxyl groups and Pdcations on the surface of SBA-15 not only anchored Pdcations,but also prevented the agglomeration of Pdnanoparticles（PdNPs）,with an excellent PdNPs dispersion of 57%.Pd/SBA-15 showed excellent catalytic performances in 12H-NEC dehydrogenation.The conversion rate of 12H-NEC was 100%and the dehydrogenation efficiency reached 98.3%at 180℃for 1 h,and the dehydrogenation efficiency reached 96.2%at 165℃for 3 h.The complexation between PdNPs and the hydroxyl groups enhanced the stability of the nanoparticles.The dehydrogenation efficiency of Pd/SBA-15 was 98.8%after five consecutive dehydrogenation cycles at 180℃for 6 h.To decrease the amount of noble metal,reduce the cost of catalysts preparation.RuNi/SBA-15 catalyst was prepared by electrostatic adsorption-chemical reduction method using SBA-15 as carrier.RuNi NPs possessed alloy structure,with an average particle size of 3.08 nm.The addition of the non-noble metal Ni increased the binding energy of Ru,and the electron interaction of RuNi alloy promoted the hydrogenation performances of the catalyst.RuNi/SBA-15 catalyzed NEC hydrogenation better than Ru/SBA-15 and commercial Ru/Al₂O₃.The hydrogenation efficiency can reach 99.8%at100℃and 5 MPa H₂ pressure for 80 min.The catalytic performances of RuNi/SBA-15did not decrease significantly for four consecutive hydrogenation cycles,and the hydrogenation efficiency still reached 98.2%.In order to achieve a catalyst suitable for hydrogenation and dehydrogenation reactions simultaneously.Bimetallic complex salt structure was designed and constructed,and PdRu/SBA-15 catalyst was prepared by phase transfer assisted electrostatic adsorption-glow discharge plasma reduction method.The structure of Si-O-Ru-Pdobtained by CH₂Cl₂ phase transfer is very stable.Glow discharge plasma reduction in situ can prevent the agglomeration of nanoparticles.The average particle size of PdRuNPs was only 3.88 nm.The introduction of Pdspecies leaded to the easier reduction of Ruspecies which was adsorbed on negatively charged hydroxyl groups.PdRuNPs showed obvious electronics interaction,and the electrons transfered from Pdto Ruafter formation of alloy.PdRu/SBA-15 exhibited excellent catalytic performances in NEC hydrogenation and 12H-NEC dehydrogenation.The hydrogenation efficiency reached 99.8%at 100℃and 5 MPa H₂ pressure for 80 min,and the dehydrogenation efficiency reached 100%at180℃for 6 h.The PdRu/SBA-15 bifunctional catalyst showed excellent stability,the catalytic performances of PdRu/SBA-15 did not decrease significantly for seven consecutive cycles,and the hydrogenation and dehydrogenation efficiency were 97.1%and 95.2%,respectively.