Novel mono-and bi-functional phosphonium salts deriving from toxic phosphine off-gas as efficient catalysts for chemical fixation of CO2

Abstract

Utilizing phosphine (PH3) tail gas as starting feedstock, a series of novel mono-and bifucntional phosphonium compounds (P+(CH2CH2CN)3RX−, X= Br, I) was prepaed by a sustainable preparation route. The newly prepared phosphonium halides show high thermal stability and their degradation temperature are far higher than that of CO2 chemical fixation. The mono-fucntional phosphonium salts combinate with ZnBr2 to form an efficient Lewis acid/base type catalytic system for CO2 chemical fixation and the bifucntional phosphonium salts alone shows same catalytic effects. The effects of temperature, CO2 pressure, composition of the catalytic system on coupling reaction of CO2 with epoxides are investigated to evaluate the catalytic performance. The results illustrate that 96.7% cyclic Carbonate yield can be obtained in presence of ZnBr2/P+(CH2CH2CN)3C4H9Br− (molar ratio = 1:10) under 120 °C, 1.5MPa of CO2 pressure in solvent-free condition, menawhile bifuntional phiospohonium salt Br-P+(CH2CH2CN)3C2H4COOH alone shows better catalytic perofromance.