Study On The Synthesis Of Diphenyl Carbonate By The Oxidative Carbonylation Of Phenol Over Pd/AC

Diphenyl carbonate (DPC), as an important carbonate, is an important precursor for producing polycarbonates by a melt-polymerization process. Oxidative carbonylation of phenol to produce DPC is a direct environmental synthetic method. This paper focuses on the synthesis of diphenyl carbonate by the oxidative carbonylation of phenol over Pd/AC.The optimum reaction condition was 80℃, 5MPa, molar ratio of CO:O2=10:1 and 4h. The phenol conversion and DPC yield could be 12.37% and 9.89%. The reaction activity could be enhanced by adding cocatalyst such as TBAB,BQ,Ce(OAc). The most efficient hygroscopic agent was 20~40mesh 3A molecular sieve. The conversion of phenol could be increased by adding MS-3A. 1,2-Dichloroethane and dichloromethane as solvent performed favorable effects on phenol conversion and DPC yield because of high polarity and strong permanent dipole moment.The existence of water had a significant influence on the synthesis of diphenyl carbonate by the oxidative carbonylation of phenol. It could be proved that the real critical concentration of water was 1.1wt% by experiments connected with VLE calculation.When the concentration of water was higher than 1.1wt%, the catalytic activities descended rapidly.According to XRD results, the growth of crystal particles and the accumulation of Pd activity component may be caused by the existence of water. Catalyst service life could be extended because of the better dispersion of Pd by adding MS as the hygroscopic agent. According to XPS results, the redox recycle of Pd(0) to Pd(Ⅱ) was interrupted and Pd(0) was accumulated by water, which caused decline of catalyst activity.