Study On The Safe Reaction Of CO₂ Hydrogenation To CO And CH₄ Catalyzed By Methylcyclohexane As Hydrogen Source

Carbon dioxide（CO₂）is one of the main components of the greenhouse effect,but it is also a non-toxic and cheap carbon source.The reverse water gas shift reaction（RWGS）is one of the effective means to convert CO₂,but it has the defects of low CO₂ conversion rate at low temperature,poor catalyst thermal stability and low selectivity at high temperature.Methyl cyclohexane（MCH）is a commonly used hydrogen storage medium,which can provide raw materials for the RWGS reaction and avoid the use of dangerous gas hydrogen;at the same time,the reaction conditions of the coupling reaction are more mild.The RWGS coupled methylcyclohexane dehydrogenation reaction process was proposed for the first time,and the reaction system was analyzed thermodynamically.The results show that the coupling process of reverse water gas change reaction and methylcyclohexane dehydrogenation reaction is thermodynamically feasible.The feasibility of coupling RWGS reaction thermodynamics of existing low-carbon alkanes（ethane,propane,etc.）and ethylbenzene was calculated,and the difference between the existing results and the equilibrium conversion rate was sorted out.The thermodynamic feasibility of coupling the RWGS reaction of the dehydrogenation of n-butene,cyclohexane,methanol and 5-hydroxymethylfurfural with little or no research was further investigated.The performance evaluation of RWGS coupled methylcyclohexane dehydrogenation reaction was further carried out in a fixed bed reactor.The effects of preparation conditions and reaction conditions of Pt/γ-Al₂O₃ catalyst on coupling reaction performance were investigated.At 350℃,0.1MPa,MCH/CO₂=3,LHSV=6h^-1,the conversion rates of MCH and CO₂ can reach up to 72.2%and 24.7%,the selectivity of toluene and CO is higher than95%,and the energy within 40h maintain high stability.Compared with the RWGS and MCH dehydrogenation reactions alone,the CO₂conversion rate of the coupling reaction is increased by 11.4%,but the MCH conversion rate is lower than the MCH dehydrogenation reaction where the carrier gas is N₂.The dehydrogenation reaction and conversion rate alone are 85.6%.A CO₂ methanation coupled methylcyclohexane dehydrogenation reaction is proposed.Under the conditions of Ni/γ-Al₂O₃ catalyst loading of 10wt.%,400℃,0.1MPa and MCH feed rate of 0.1m L/min,the MCH conversion rate was 75.9%,the CO₂ conversion rate was65.5%,toluene selectivity is 99.0%and the CH₄ selectivity is 94.6%.The catalytic performance of Ce-Ni/γ-Al₂O₃ catalyst was investigated.It was found that the catalyst added Ce significantly enhanced the activity of CO₂ methanation coupling methylcyclohexane dehydrogenation reaction.MCH conversion rate was 85.4%,CO₂conversion rate was 76.8%,TOL selectivity was 99.5%,CH₄ selectivity was 95.1%.