Synthesis Of Organic Carbonates By The Alcoholysis Of Urea Over Hydrotalcite-Like Compounds

Propylene carbonate and diphenyl carbonate are two kinds of important organic compounds. Alcoholysis of urea is considered to be a novel and promising process in synthesis propylene carbonate, and the transesterification process to synthesize diphenyl carbonate is also payed much attention.Both of alcoholysis and transesterification reactions can be catalysed by alkali and acid. HTLcs and their calcined products were selected as the catalysts for the alcoholysis reaction as they have both alkali and acid sites.The catalytic activity of different HTLcs and their calcined products has been investigated and the reaction conditions has been optimized. All kinds of HTLcs have obvious catalytic activity in the alcoholysis reaction while calcined HTLcs changed their catalytic activity due to the change of structures. The species of divalent and trivalent cations of HTLcs have the same important influence on the catalytic performance.The acidity and basicity of catalysts may be the key factor that influence the catalytic activity.Under optimal reaction condition: n(PG)/n(Urea)=4,T=170 oC, t = 5 h, the mass fraction =0.25%, the calcined Zn-Al HTLcs has the highest catalytic activity and the yield of PC is 98.7%.Furthermore, the catalytic activity of different catalysts in the transesterification reaction of diethyl carbonate with phenol has also been investigated and diethyl carbonate and dimethyl carbonate have been contrasted as transesterification reagents. Under follow condition: n(PhOH)/n(DEC)=2,T=170~190oC,t=8 h, the mass fraction of PbTiO3 precursor=1.1%, the convertion of phenol is 31.3%,the yield of DPC is 12.5%. and the selectivity for transesterificated products was 97.7%.When diethyl carbonate was used as transesterification reagent,the convertion of phenol and the yield of DPC had improved,but the extant was small.