Studies On Modified Pillared Interlayered Clay Catalyst And Its Catalytic Performance For The Synthesis Of Diphenyl Carbonate

Preparation, characterization of modified pillared interlayered clay and its catalytic performance in the synthesis of diphenyl carbonate(DPC) by transesterification have been studied.The titanium pillared interlayered clay(Ti-PILC) was synthesized using TiCl4 as the titanium source by means of hydrolysis method. The effect of calcination temperature, initial concentration of hydrochloride, initial Na-Bentonite suspension concentration, aging time of the pillaring agent, intercalation temperature, the concentration of both hydrochloride and Ti(IV) in the mixed solution and Ti/Clay on the composition, structure and the catalytic activity of Ti-PILC was investigated. The Ti-PILC catalyst with large pore volume, high interlayer spacing, high BET surface area and stable structure was obtained under the optimized preparation conditions. The Ti-PILC catalyst showed high catalytic activity to the transesterification of DMC with phenol and DPC yield could reach up to 29.1%. By means of FT-IR analysis of adsorbed pyridine and analysis of XRD, it could be concluded that synergism of interlayer structure with acid sites of Ti-PILC is the dominated factor for the synthesis of DPC by transesterification of DMC with phenol. Moreover, Ti-PILC was also prepared using Ti(OC4H9)4 as the titanium source by sol-gel method. With suitable Ti(OC4H9)4/H2O and Ti/Clay, the Ti-PILC with large crystal plane distance and high specific surface area was attainable and DPC yield over the catalyst could reach up to 24.8%.BET measurement indicate that N2 adsorption-desorption isotherm curves of the Ti-PILCs are II isotherms overlapping with B adsorption loop-line, which suggests that the pore structure of the Ti-PILCs mainly consists of uniform parallel plates and plate-typed capillary pores with one closed end and wide pore distribution. That is the typical characteristic of pillared interlayered catalyst. The characteristic of BJH curves shows that the pore structure of the Ti-PILCs prepared by sol-gel process is more uniform than that of the Ti-PILCs prepared by hydrolysis method. This suggests that sol-gel method can obtain porous structure with uniform pore size.Double-metal oxides(PbO-ZnO) pillared clays was prepared. The effect of calcination temperature, Pb/Clay, adding order of Pb(OAc)2 and Zn(0Ac)2, initial Na-Bentonite suspensionconcentration, OH-/Pb2+ and intercalation temperature on the catalytic activity was investigated. The highest yield of DPC is 12.0% over the catalyst from the suitable preparation conditions under the proper reaction conditions.Different methods were used in the preparation of lead-zinc modified Ti-PILC catalyst. The catalytic properties of catalyst prepared by initial wetting penetration process decreased to a half compared with Ti-PILC. XRD and BET analysis prove that PbO-ZnO/Ti-PILC prepared by impregnation process still keeps some interlayer structure. Crystal Pb3O4 and ZnO were found on the surface of Ti-PILC which congregated to block the pore canals and resulted in diminishing of the BET area. Lead and zinc loading was the major factor affecting the PbO-ZnO/Ti-PILC catalytic activity in the transesterification reaction. The highest yield of DPC is 21.8% (over 15wt% PbO-ZnO/Ti-PILC catalyst).Composite-metal-oxide pillared interlayered clay -PbTiO3-PILC and (Pbo.67Zno.33)-TiO3-PILC were prepared by sol-gel method. There existed Pb3O4, PbO, PbO2 and Zn2TiO4 crystal phase in both PbTiO3-PILC and (Pb0.67Zn0.33)TiO3-PILC. BET surface area and pore volume increased a lot compared with Na-bentonite because PbTiO3 and (Pb0.67Zn0.33)TiO3 were inserted into Na-bentonite's layers. However, the number of metal-oxide pillars were a few and its degree of order in PILC's interlayer was not perfect. (Pbo.67Zno.33)TiO3-PILC showed higher catalytic performance for the transesterification of DMC with phenol than that of Ti-PILC, the yield of DPC could reach up to 35.7%.