Research On The Use Of Composite Hydrogen Donors For Catalytic Hydrogenation Of Carbon Dioxide In Flue Gas

The large amount of carbon dioxide(CO2)produced by coal-fired power plants has caused a series of environmental problems,and human survival has been seriously harmed,so the CO2 control and emission reduction are urgent problems to be solved.In many ways,resource utilization technology can convert CO2 into higher added value chemcial product,which has the dual significance of emission reduction and resource utilization.Among them,the catalytic transfer hydrogenation method is a cutting-edge topic that has been widely concerned by scholars at home and abroad.This paper is based on the principle of catalytic hydrogenation and proposes a new means to convert CO2 into organic acids using a composite hydrogen donor,providing a theoretical reference for the utilization of CO2 resources.Using potassium borohydride(KBH4)and isopropanol as hydrogen donor,a composite hydrogen donor system was set up to hydrogenate and reduce CO2 so that explore the effect of multiple factors on the CO2 absorption and conversion.The experimental results show that under the optimal conditions of isopropanol volume concentration 80%,potassium borohydride concentration of 0.25mol/L,reaction temperature of 45℃,gas flow rate of 0.5L/min,and the solution pH of 6.83 before the reaction,CO2 absorption efficiency and the selectivity of formate were 47.99%and 61.08%,respectively.Comparing with the single KBH4 system,the increase is about 20%and 35%,indicating that the composite hydrogen donor system has a good synergy effect.Meanwhile,the experiment on the effects of coexisting gas was performed,and the result showed that the coexisting gas had little effect on the reaction system.Nano-scale zero-valent nickel material was prepared as catalyst to catalyze the hydrogenation of CO2 in the composite hydrogen donor system.According to the result of multiple factor experiment,the optimal experimental condition was determined as isopropanol volume concentration 80%,potassium borohydride concentration of 0.3mol/L,catalyst of 0.5g/L,reaction temperature of 35℃,gas flow rate of 0.35L/min,and the solution pH of 7 before the reaction,CO2 absorption efficiency and the selectivity of formate were 48.54%and 60.76%,respectively,which were 4%and 7%higher than those without catalyst.The SEM,EDS and XPS were used to characterize the catalyst and explored its morphological structure and elemental composition.It was confirmed that the prepared catalyst was nano-scale zero-valent nickel,which was relatively stable and reusable.Based on the result of ion chromatography for the detection of product and references,a preliminary study and analysis of the reaction mechanism was conducted.