Performance, Preparation And Shaping Of Manganese Oxide Octahedral Molecular Sieves For Synthesis Of Diphenyl Carbonate

Heterogeneous palladium catalysts supported on mixed oxides demonstrate theoretical as well as practical values in oxidative carbonylation of phenol to diphenyl carbonate (DPC) for the green chemical engineering. This catalytic system is easily separated and the function of reoxidation of Pd0 is performed simultaneously.The performance of manganese oxide octahedral molecular sieves was studied for direct synthesis of DPC. It was determined that the catalytic activity was related to the average oxidation state of manganese and oxygen species. Compared with acid-base treatment and calcination in oxygen atmosphere, metal doping is an effective method to improve the catalytic activities. The best DPC yield reached 18.1% when a new phase Pb2-xMn8O16 was formed after Pb doped, which is twice than that when undopped catalysts were used. XPS characterization showed that the reason for deactivation of catalysts is that redox cycle could not remain and active Pd2+ site was reduced to Pd0.The K-OMS-2 materials were prepared in high gravity reactor. The optimal condition is as follows: speed of rotation 1200r/min, temperature 100℃, the amount of concerned HNO3 340ml and reaction time 2h. K-OMS-2 powder obtained in high gravity reactor had a better distribution than that synthesized by the traditional reflux method. The KAC-HAC buffer solutions are not suitable for the preparation of K-OMS-2 due to the lack of inducer HNO3.Shaping process of K-OMS-2 powder was investigated. Among auxiliaries selected,sodium carboxymethyl cellulose, bentonite, starch and urea are added to make shaping relatively easy. The shaped support containing bentonite, silica sol and kalion were capable of withstanding temperature as high as 600℃without collapse. The order of strength after auxiliaries used is sodium carboxymethyl cellulose > bentonite > silica sol > polyvinylpyrrolidone > active carbon > urea > kalion. Based on these results,bentonite was considered to be the best auxiliaries to shape. Moreover, the synergistic effect of compound auxiliaries was observed when active carbon and urea was introduced with bentonite,and the properties of shaped supports with active carbon as the second auxiliaries are better than that with urea as the second auxiliaries in the respect of the appearance, tolerance to temperature and compressive strength.