Study On Synthesis Of Propylene Carbonate And Dimethyl Carbonate In Supercritical Carbon Dioxide

Propylene carbonate (PC) is widely used in industry as organic solvent. It is also used as an intermediate product to manufacture other products, for example dimethyl carbonate (DMC). As an environmentally benign building block, DMC can be used in chemical synthesis instead of COC12, CH3OCOCH2C1. Therefore the study on synthesis of both PC and DMC is of theoretical importance and practical value. In this paper both the synthesis of PC from PO and CO2 and the synthesis of DMC from PO, CO2 and methanol have been studied systematically.KI/y - Al2O3 has been found to be a good catalyst with higher activity for the reaction of PO with CO2 .The suitable reaction conditions have been found out. In addition, higher PC yield can be obtained when the reaction is carried out in supercritical CO2.However, the stability of this catalyst is not satisfactory. XRD and XPS analysis of the catalyst have proved that the deactivation of the catalyst is due to the loss and oxidation of I". In addition, the blocking of the catalyst pore by the solid particle and some organic macromoleculars which are formed in the process of reaction is another reason for the deactivation. The activity of the deactivated catalyst is improved when it is dealt with ethanol, for the solid particle and organic macromoleculars can be washed away when the catalyst is dealt with ethanol.In addition, the kinetic study of PC synthesis has be performed over KI/y -Al2O3 in a tubular fixed-bed reactor. The reaction rate equation is:r=0. 699exp(-5. 083 X 104/RT) P.The significance test proves that the kinetic model is significant .KL.0/4A molecular sieve catalyst has been developed for the synthesis of DMC from PO, CO2 and methanol, and its activity is higher than others reported. PO can be converted completely over this catalyst, and PC and DMC yield reache 18.24% andin54.70% respectively.Experiments have proved that PC is formed from PO and CO2, and DMC is formed from PC and methanol. Methanol is not only a raw material to DMC but also a auxiliary catalyst for DMC synthesis.