Preparation Of Renewable Alkaline Ionic Liquids And Their Efficient Catalytic Hydrogen Production Under Mild Condition

The excessive consumption of non-renewable fossil energy will bring a series of environmental problems and energy crises.Among renewable alternative energy sources such as wind,water and biomass,hydrogen has shown great potential to replace fossil energy.Hydrogen can be widely used in metal purification,organic synthesis,food processing,semiconductor production and other fields,and the demand for hydrogen is expected to continue to increase in the future.At present,more than 80%of the technology of industrial hydrogen production is concentrated in the steam conversion of fossil fuels,which is harsh,excessive energy consumption,low energy conversion and emitting greenhouse gases.The use of hydrogen production methods such as electrolysis of water and biomass still has limitations in technology,output and resources.Therefore,it is of great significance to study the green and efficient hydrogen production system under mild conditions.The Si-H bond of hydrosilane is relatively weak,easy to crack to produce hydrogen,and it is a liquid that is convenient for storage under environmental conditions,eliminating the safety of transportation,making hydrogen production with hydrosilane a hot spot for the development of green and sustainable hydrogen economy in recent years,and related research is gradually concentrated.The common alcohol dehydrogenation coupling system has favorable thermodynamics,slow kinetic reaction,and often requires the participation of metal-based catalysts,which has high requirements for catalysts and reaction conditions.Based on this,this project uses ionic liquids with good stability,low toxicity and simple preparation as catalysts to participate in the hydrogen production reaction of industrial waste Polymethyl hydrosiloxane（PMHS）and water,and develop research on efficient catalytic hydrogen production under mild conditions.In this study,the catalyst preparation process was improved,and ordinary commercially available ionic liquids were modified by ion exchange to prepare a renewable basic ionic liquid catalyst,which was oriented based on the reactive site.Finally,efficient catalysts were screened out,related conditions were optimized,solvent and substrate were expanded,and the mechanism and environmental impact assessment were speculated.These include:（1）[Bmim]OH catalyst was prepared,and the presence of hydroxyl and imidazole rings was verified by Fourier Infrared（FT-IR）and Nuclear Magnetic（¹H-NMR）.The gas produced by gas phase verification is hydrogen and quantified.Polymethyl hydrosiloxane is used as a substrate to react with water,and a hydrogen yield of 99.3%can be obtained under optimal conditions.For substrate expansion using multiple types of hydrosilanes,hydrogen yields of 82-99.9%were also obtained.Kinetic calculations show that the reaction rate can reach 276μmol m L^-1 min^-1 at 5min.The yield of the catalyst was still more than 96%after repeated use for 4 times,and it still had high activity when placed closed at room temperature for one year.The activation of Si-H bonds under the action of catalyst is the key for PMHS to participate in the reaction.Hydrogen is formed by providing a hydrogen atom each from organosilane and water,and silanols are produced at the same time,which brings a new idea for the synthesis and development of silanols.Life Cycle Assessment（LCA）shows that the system has outstanding advantages in reducing pollutant emissions and environmental impact.（2）Compared with a series of carboxylate choline catalysts with variable carbon chain length,the prepared ACH-OH is more basic and has a higher yield of up to100%.FT-IR and ¹H-NMR characteristics were used to verify the existence of hydroxyl groups and carboxylic acid groups in the catalyst,and the gas produced by gas phase verification was hydrogen.Compared with the first system imidazolyl ionic liquid catalyst,its slightly higher reactivity is mainly attributed to the higher water solubility of acetylcholine ionic liquids.Using hydrosilane as a substrate,84-100%hydrogen yield can be obtained under this body reaction.Kinetic calculations show that the reaction rate can reach 266μmol m L^-1 min^-1 at 5 min.The catalyst has been recovered and recycled 4 times to maintain a yield of more than 96%.PMHS molecules contain active Si-H bonds,which in the presence of a basic catalyst,can react with water to release hydrogen and produce corresponding silanols.Compared with the imidazolyl ionic liquid catalytic system,the four indicators of global warming,eutrophication,acidification and non-renewable resource depletion in LAC have decreased.In particular,the decline in the eutrophication index indicates that the catalyst has less biological toxicity.