Synthesis of Propylene Carbonate from Urea and 1,2-Propylene Glycol in a Monolithic Stirrer Reactor

Abstract

A monolithic stirrer reactor, in which the cordierite monolith-supported metal oxide and mixed-metal oxide catalysts are used as stirrer blades, is applied for the alcoholysis of urea with 1,2-propylene glycol to synthesize propylene carbonate. It is shown that the mixed-metal oxides give much higher urea alcoholysis performances than the metal oxides, arising from the existence of a strong synergetic effect in the mixed-metal oxides. The zinc–chromium mixed oxide not only shows an excellent catalytic performance but also has extremely strong adhesion strength on the monolithic substrate. For the monolith-supported zinc–chromium mixed oxide catalyst, the monolithic stirrer reactor performs very well, and the highest yield of propylene carbonate reaches 97.8%. The performance is comparable to that of a conventional mechanically agitated slurry reactor, revealing the monolithic stirrer reactor can be an attractive alternative to the slurry reactor for heterogeneously catalyzed liquid–liquid reactions.