Hydrogenation And Dehydrogenation Of Organic Liquid Hydrogen Carriers By Unsupported NiMo Solid-Solution Catalysts

As a clean energy source,hydrogen is abundant in resources and it gives off about three times as much heat as gasoline of the same mass when burning.But the problem of hydrogen storage has always been a huge challenge.Organic liquid hydrogen storage（LOHCs）is a new type of hydrogen storage technology,which can transfer hydrogen by means of hydrogenation/dehydrogenation reaction of organic liquid unsaturated compounds.In this paper,in order to reveal the relationship between the physicochemical properties and the catalytic reaction performance.The unsupported catalysts and hydrogenation/dehydrogenation performance of different organic liquid hydrides was studied.In this paper,Ni and Mo Ox nanocrystals unsupported catalyst were prepared,and the effects of mole ratios of Ni and Mo on the physicochemical properties of catalysts were investigated.Catalyst with high specific surface area（224 m²/g）was obtained.And the 9-ethylcarbazole hydrogenation/dehydrogenation reaction was studied.Under the condition of120℃,3 MPa and 2 h^-1（LHSV）,the conversion rate of NECZ（9-ethylcarbazole）hydrogenation and selectivity of 12H-ethylcarbazole（12H-NECZ）of Ni₃Mo₁ catalyst reached 100%and99.6%.Respectively,when the conditions is 220℃,0.5 MPa,2 h^-1,the dehydrogenation conversion rate of 12H-NECZ reached 100%,and the selectivity of 9-ethylcarbazole reached95%.The influence of temperature,pressure,LHSV and other reaction conditions was also investigated on the catalyst activity.And the process conditions were optimized.Based on the calculation of hydrogenation kinetics,the apparent activation energy of the catalyst is 17.61k J/mol,which provides a new idea for the design of an inexpensive and highly active hydrogenation catalyst.The hydrogenation and dehydrogenation of toluene/methylcyclohexane were also investigated.The experiment found that the unsupported catalyst has a high low-temperature hydrogenation capability for toluene,and can completely hydrogenate toluene at 60℃.In experiment,the dehydrogenation of methylcyclohexane was evaluated over 20 wt%Ni/Al₂O₃catalyst.It was found that the dehydrogenation conversion rate of methylcyclohexane and the selectivity of toluene can reach 94%and 96%respectively,when the space velocity is 2 h^-1,the temperature is 380℃,the pressure is 0.5 MPa,and the hydrogen-oil ratio is 50.The hydrogenation of the eutectic mixture system of biphenyl and diphenylmethane was also investigated.The eutectic melting point was about 8℃.When the mass ratio of biphenyl to diphenylmethane is 35:65,it is liquid at room temperature,and the maximum hydrogen storage capacity is 6.9 wt%.100%hydrogenation conversion rate of biphenyl and diphenylmethane and 100%selectivity of perhydrogen products over Ni Mo solid solution catalyst.When the temperature is 360℃,the dicyclohexane and dicyclohexylmethane can achieve 96%and 98%hydrogenation conversion rate and 95%（Biphenyl）and 92%（Diphenylmethane）selectivity over Ni/Al₂O₃ catalyst.The system also provides new ideas for the industrial application of organic liquid hydrogen storage.