Synthesis Of Propylene Glycol Methyl Ether From Etherification Catalyzed By Basic Ionic Liquids

Ionic liquids,as a novel green media,have been widely discussed and become the most potentialliquids material for application,due to their widely tunable and diversiform properties.Ionic liquids have been applied to organic synthesis,gas separation,catalysis,electrochemistry and so on.However,the synthesis of new kinds of ILs and the catalytic mechanism investigation of ILs are always the guiding direction of ILs catalysis field.In order to have a deep understanding of mechanism of ILs catalysis and the influence of chemical-physical properties of ILs on reactivity for the synthesis of propylene glycol methyl ether?PGME?,various IL catalysts have been prepared and the relationship of their structure with catalytic performance systematically investigated by experiment and theoretical calculation approaches.The major work and innovative results of this dissertation are summarized as follows:?1?An efficient ionic liquids catalytic system has been established.Result shows that the acetate-based ionic liquid exhibits a high catalytic activity.The selectivity of main products is above 90%while the yield is about 19%higher than conventional catalysts?NaOH?.The influences of basicity and hydrogen bond properties on catalytic performance have been discovered.According to the result,the basic strength and hydrogen bond donating ability are the key factors in the reaction cycle.With the increase of basicity and hydrogen bond donating ability,the catalytic performance of ILs would be enhanced extraordinarily.Due to the fact that the nucleophilic attack of charge is stronger than hydrogen bond,there is less relationship between hydrogen bond donating ability and catalytic performance.The polarizability of ILs showed a weak contribution to activity that ionic liquids is too little resulting that polarity doesn't work.?2?The catalytic mechanism of designed methylcarbonate-based ionic liquids as catalyst has been studied by ESI-QTOF-MS.The methylcarbonate-based ILs displayed an extraordinary catalytic performance compared with acetate-based ILs and conventional base catalysts NaOH.The yield of methylcarbonate-based ILs as catalyst is about 10%and 20%higher,respectively.Further experimental results verified the catalytic mechanism of methylcarbonate-based ILs is different from traditional base catalytic mechanism.Transesterification was assumed to occur between anion of[N₂₂₂₁][MC]with CH₃OH to generate methoxy group?CH₃O-?,which catalysts don't changed in formula but changed in mature.Owing to experimental methods,it was found that methylcarbonate-based ILs as catalyst would interesterificate with methanol,thus changed the reaction pathway and activation energy.A process for the synthesis of PGME in the presence of methylcarbonate-based ILs was studied.It was found that the catalyst could be reused without loss of catalytic activity after ten times,and the conversion is above 98%while the selectivity is above 90%.?3?The catalytic reaction kinetics of NaOH and methylcarbonate-based ILs was studied to find out their difference in catalytic mechanism.It was found that the reaction order of ILs is not consistent with NaOH.The reaction catalyzed by methylcarbonate-based ILs is 1.5-order reaction as 2-order reaction for Na/OH as catalyst.It suggested that the catalytic mechanism of methylcarbonate-based ILs and NaOH is different.The activation energy is obtained by fitting the Arrhenius equation.The results of the reaction activation energy catalyzed by methylcarbonate-based ILs and NaOH are 32.8 kJ/mol and 54.8 kJ/mol,respectively.