Synergism Study Between Halides And Dehydrating Agents In Ru-catalyzed Hydroesterification

In this paper,the hydroesterification reaction of ethylene was catalyzed by Ru₃（CO）₁₂with ionic liquid as the co-catalyst and the abundant,cheap,green and non-toxic carbon dioxide as the carbonyl source.The synergistic promoting effect of dehydrating agent and halides in the reaction was investigated.The main research work is summed as the follows:1.The promoting effect of Ti（OCH₃）₄ and Mg Cl₂ on the hydroesterification reaction was investigated respectively and the synergism between them was researched.Then the reaction conditions were optimized.It was found that Ti（OCH₃）₄ played a role in promoting the shift of chemical equilibrium to the positive direction in the reaction.The addition of Ti（OCH₃）₄could greatly reduce the amount of catalyst and increased the TOF value from 5.4 h^-1 to 120.6h^-1.In the Ru₃（CO）₁₂/Ti（OCH₃）₄ reaction system,adding trace amount of Mg Cl₂ can further increase the yield and TOF value,which improved with the increase of Mg Cl₂ addition.In addition,temperature,pressure,the amount of catalyst and dehydrating agent are also beneficial to the reaction.By the optimization of experimental conditions,TOF values reached up to 178.9 h^-1 with the cooperation of Ti（OCH₃）₄ and Mg Cl₂.However,the cyclic performance of the catalytic system is poor,which may be due to the limited hydrolysis degree of Ti（OCH₃）₄ and the decarbonylation of Ru₃（CO）₁₂.In addition,the promotion effect of 1-（3-trimethoxypropyl）-3-methyl imidazolium chloride salt（[Tms Pmim]Cl）and the synergism between[Tms Pmim]Cl and halides were studied.It was found that compared with1-methyl-3-butylimidazolium chloride salt[Bmim]Cl,[Tms Pmim]Cl had an additional dehydrating effect.Under the conditions of 0.010 mmol Ru₃（CO）₁₂,200℃,4 MPa and 4 h,the yield of methyl propionate increased from 40.5%to 61.1%by using[Tms Pmim]Cl instead of[Bmim]Cl.The addition of halides could further promote the reaction and the maximum of TOF value can reach 50.8 h^-1 by optimizing the reaction conditions.Finally,the possible active species in the hydroesterification catalyzed by Ru₃（CO）₁₂/[Bmim]Cl and the promotion mechanism of halides in the reaction were discussed.The results preliminarily confirmed that the ruthenium-hydride-carbene complexes is the possible active species and halides can promote the dissociation of CO ligand from ruthenium-carbonyl complexes to produce active species and stabilize the active species.2.Polyionic liquid P[DVIm]Br was prepared with 1-vinyl-3-butyl imidazolium bromide as monomer and divinylbenzene as crosslinking agent.The results of TGA and SEM showed that the polyionic liquid had high decomposition temperature and porous microstructure.The catalytic activity of Ru₃（CO）₁₂/P[DVIm]Br was investigated by heterogeneous hydroesterification of ethylene.The results showed that the yield of 74.3%was obtained in the Ru₃（CO）₁₂/P[DVIm]Br catalyst system,but its cycle performance was poor.