Fundamental Research Of Capture,Storage And Conversion Of Carbon Monoxide Using Protic Chlorocuprate Ionic Liquids

With the unremitting pursuit of atom economy and energy efficiency,C1 chemistry has received a great attention in industry.CO,as an important gaseous C1 building block,has been growing rapidly in its demand on the chemical synthesis industry.It was reported that CO emission by industrial exhaust is as high as 17 million tons in our country.The emission of CO is not only a loss of energy,but also can cause environmental pollution.The main industrial recovery technologies currently available still have some shortcomings,such as high energy consumption,high pollution and low recovery rate.From the viwpoint of green chemistry,the comprehensive utilization of CO resources are becoming of great concern,to meet the requirements for environmental protection,control of CO emission and resource reuse.Ionic liquids(ILs)are organic molten salts composed of ions,and most of them are liquids at room temperature.They can be functionally designed and have been proposed as promising green materials owing to their unique properties,such as wide liquid range,no measurable vapor pressure,tunable structure and high thermal stability.It has been known that many acid gases(such as CO2,SO2,H2S,and NO)have remarkable solubilities in various ILs.Herein,we present a series of novel copper(?)based PCILs with significantly enchanced CO absorption capacities and explore their potential application in CO conversion.Our research provides a new method in the field of capture,storage and conversion of carbon monoxide.First,in this work,we designed and synthesized six new protic ionic liquids:[TMA][CuCl2],[TEA][CuCl2],[TPA][CuCl2],[EIM][CuCl2],[EIM][CuBr2]and[DMA][CuCl2].The synthetic method was explored and the physical properties of PCILs such as density,viscosity and CO absorption capacity were investigated.The equilibrium data were calculated by developing a reaction equilibrium thermodynamic model,to obtain some useful parameters such as the Henry's constant H for physical absorption,the reaction equilibrium constant Ko and the molar reaction enthalpy ?H.It was concluded from the experiments and calculations that these protic ionic liquids showed a higher absorption capacity for CO(ranging from 0.02 to 0.1 molco/molIL at 30? and 1 bar)compared with other ILs or traditional organic solvents.In particular,an unexpecd phase change of[TEA][CuCl2]and[TPA][CuCl2]from liquid to solid was observed during CO absorption and the phase transition can drastically enhance the CO absorption capacity.The formation of copper(?)carbonyl complexs verified through spectrum analysis and DFT calculation should account for this phenomenon.We can even get a solid material with CO mass of as high as 13%of ionic liquid at 30 bar CO pressure.PCILs have the potentials to be developed into a kind of green CO storage materials differing from highly toxic carbonyl iron and carbonyl cobalt.In addition,a series of experiments were designed to test the CO absorption/release rate and the cyclic utilization of[TEA][CuCl2],and the possibility of using PCILs as separation materials for CO/N2 were also analyzed with significant progress.The remarkable solubility of CO in[TEA][CuCl2]and[TPA][CuCl2]offers us an additional opportunity to improve the efficiency of reactions in CO-PCIL systems.Herein,the carbonylation of styrene with CO was tested as an example.60%acid yield was achieved under conditions of 25? of reaction temperature,30 bar of CO partial pressure,8 h of reaction time and a 80:80:40:8:1 molar ratio of[TPA][CuCl2]/water/styrene/TsOH/Pd(OAc2).In fact.this reaction usually requires noble metal catalyst and high reaction temperature(above 100?).The successful realization of carbonylation of styrene in the CO-PCIL system at room temperature provides an important basis for the mild and green carbonylation using PCILs as cheap cocatalysts.Green absorbents are required to capture CO from industrial exhaust gas whereas the fixed CO can be used as raw material in the carbonyl synthesis that requires low-cost cocatalyst or solvent.Our research work here tried to combine these two aspects by using a kind of protic chlorocuprate ionic liquids.Significant progress has been achieved to provide important basis for further development of CO capture-utilization integration process.