Synthesis Of Polyimidazoline Ionic Salts And Their Application In CO₂ Cycloaddition

The cycloaddition reaction between CO₂ and epoxide to form cyclic carbonate is one of the most effective ways to immobilize CO₂,which accords with the green chemical standard.Because of the chemical stability of CO₂,catalysts must be used to convert CO₂ to cyclic carbonates.Homogeneous catalyst has some disadvantages,such as unstable catalyst,difficult catalyst separation and so on,which limits their application.On the other hand,the heterogeneous catalyst is easy to separate and can be recycled,so it has a better research prospect.Ionic polymers are widely used to catalyze the CO₂ cycloaddition reaction due to their adjustable pore size,designed active sites and excellent physical and chemical stability.In this paper,four kinds of poly Imidazoline ionic salts were synthesized by post-modification and used to catalyze CO₂ cycloaddition reaction.The main research contents are as follows:1.Using p-aminobenzyl alcohol as raw material,monomer TBA was synthesized by two-step reaction,and then terephthalaldehyde and monomer TBA reacted with ammonium chloride to form two Imidazoline-linked polymers COP-222 and PTBA,which were reacted with methyl iodide to form Imidazolinium ionic polymers COP-222-I and PTBA-I,which had 61.5%and 67.8%I^-content,respectively.From the N₂ adsorption-desorption test results,the specific surface areas(S_BET)of COP-222-I and PTBA-I are 2.49 m² g^-1 and 7.03 m² g^-1,respectively.From the CO₂adsorption curve,the CO₂ adsorption values of COP-222-I and PTBA-I are 0.65mmol g^-1 and 0.67 mmol g^-1,respectively.Using these two ionic polymers as heterogeneous catalysts for CO₂cycloaddition reaction,PTBA-I has better catalytic activity than COP-222-I under the same reaction conditions.The two catalysts had high stability and the catalytic activity did not decrease significantly after being recycled for 5 times.2.N-heterocyclic monomers PZ and TP were synthesized from piperazine by nucleophilic substitution reaction and polymerized with ammonium chloride to form N-rich polymers PPZ and PTP.The two polymers were modified with methyl iodide respectively to form ionic polymers PPZ-I and PTP-I,whose I^-contents were 72.6%and 73.4%,respectively.The specific surface areas(S_BET)of PPZ-I and PTP-I were1.78 m² g^-1 and 0.45 m² g^-1,respectively.The CO₂ adsorption values of PPZ-I and PTP-I were 0.54 mmol g^-1 and 0.51 mmol g^-1,respectively.When PPZ-I and PTP-I were used to catalyze the cycloaddition reaction of CO₂,both showed good catalytic activity and good cycling performance.