Catalytic Synthesis Of Diphenyl Carbonate By Transesterification Ove Supported Sn On TiO₂ And Inorganic Sn

In this paper,the reaction for preparing diphenyl carbonate(DPC),the key intermediate of the non-phosgene polycarbonate manufacturing process,by transesterification of dimethyl carbonate(DMC)with phenol in the presence of heterogeneous catalysts including SnCl₂/TiO₂ and SnO catalysts has been studied.1)TiO₂ support was synthesized using TiCl₄ and Ti(OC4H₉)₄ as the titanium source by means of hydrolysis method and sol-gel method.The supported SnCl₂ catalysts by TiO₂-AS prepared using TiCl₄ as the titanium source showed excellent catalytic activity and selectivity to the transesterification of DMC with phenol:at 170-180℃for 10h with DMC:PhOH =1.5:1(mol),39.15%phenol conversion,62.32%DPC selectivity respectively.2)By means analysis of XRD and BET,it could be concluded that supported catalysts with big pore diameter and high specific surface area were favorable for formation of DPC,while microporous catalysts promoted formations of anisole and methylphenyl carbonat.Mesoporou TiO₂-AS was the best support among the tested supports.Tin Compounds were well dispersed because not observed X-ray peaks.3)XPS analysis proved that crystal SnO₂ was found on the surface of TiO₂-AS and formed Sn-Ti solid-solution.Content of SnO₂ was enhance after reaction.It was the major factor that form Sn²⁺to Sn⁴⁺affected activity in the transesterification reaction.4)FT-IR analysis proved that the structure of mesoporous TiO₂-AS is weakened and crystal SnO₂ was found on the support surface after reaction.5)In the researched tin compounds,SnO oxide exhibited excellent catalytic activity and selectivity:48.30%phenol conversion,32.76%DPC yield and 68.21%DPC selectivity respectively.6)Most of the researched tin compounds were unstable and changed during the transesterification except Sn₂P₂O₇ and SnSO₄.By XRD analysis.When SnO was used as the catalyst,water perhaps promoted the formation of Sn₆O₄(OH)₄ during the reaction.7)The acid strength of catalyst had a significant influence on the selectivity of the product.The weak acid sites were in favor of the production of DPC through the transesterification of DMC with phenol,while the strong acid sites took advantage of formation of by-product anisole through the cracking of alkoxide bond.