In this paper, the effect of catalyst preparation on the activity of supported Cu catalyst for oxidative carbonylation of methanol to dimethyl carbonate was investigated. The results showed that after addING metal hydroxide, the supported Cu catalyst enhanced the conversion of methanol and the selectivity TO of DMC and the suitable mole ratio of OH/Cu is 1.0. The optimum Cu content lies in 6 10wt.% and varies with reaction temperature. The suitable calcination temperature range is 200～300℃ considering both factors of methanol conversion and DMC selectivity. The effect of particle size of the catalysts on the activity is negligible.

Diphenyl oxalate was synthesized from transesterification of dimethyl oxalate with phenol over TS-1 (2.5 wt% Ti) catalyst. TS-1 catalyst, as a heterogeneous catalyst, showed excellent selectivity of diphenyl oxalate and methylphenyl oxalate compared with other homogeneous catalysts. Lewis acid sites on TS-1 catalyst were the active sites for transesterification of dimethyl oxalate with phenol. The high selectivity was closely related to the weak acid sites over TS-1.

The transesterification of dimethyl oxalate with phenol to produce methyphenyl oxalate and diphenyl oxalate was carried out in liquid phase using a heterogeneous catalyst. The evaluation results showed that TS-1 had better activity and excellent selectivity to target products compared with many conventional ester exchange catalysts tested. Two hours as the duration of the reaction was appropriate. Under the catalytic reaction conditions, framework IR and the reaction results jointly proved that the best calcination temperature was 823 K at which the amount of acid sites measured by IR of adsorbed pyridine reached a maximum. X-ray diffraction of TS-1 did not show much variation with changing calcination temperatures from 723 to 923 K. The characterization of the catalyst, by means of IR of adsorbed pyridine and NH3-TPD indicated that the desired catalytic activity of TS-1 could be ascribed to its weak Lewis acidity. Tin modified TS-1 showed a better performance in activity and selectivity. The conversion of dimethyl oxalate was improved up to 50.3% when Sn loading was 2, while the selectivity was above 99% over all Tin modified TS-1 molecular sieves.

The transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out in liquid phase using a variety of solid catalysts. The evaluation results showed that MoO3/SiO2 had a better activity and excellent selectivity to target products compared with many conventional ester exchange catalysts. The effects of supports, loading amount of Mo, catalyst amount and reaction time were investigated. Under catalytic reaction conditions, the total selectivities to methyl phenyl oxalate and diphenyl oxalate were up to 98%. And 49.3% yield of methyl phenyl oxalate and 17.3% yield of diphenyl oxalate were obtained at 453K in the presence of MoO3/SiO2. A plausible mechanism for the transesterification of dimethyl oxalate with phenol to methyl phenyl oxalate over MoO3/SiO2 was proposed.

A series of MoO3/SiO2 catalysts were prepared with Mo loadings ranging from 1 to 16 wt% and applied to the transesterification of dimethyl oxalate (DMO) with phenol. The results showed that the catalyst of MoO3/SiO2 with 1 wt% Mo content performed best, giving 54.6% conversion of DMO and 99.6% selectivity to target products, methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO). The surface properties were investigated by means of X-ray diffraction (XRD), X-ray photoelectron (XPS), BET specific surface area, temperature-programmed desorption (TPD) of ammonia, and FTIR analysis of adsorbed pyridine. XPS and XRD analyses indicated that Mo(VI) species was highly dispersed at low Mo loading and MoO3 of the crystal structure appeared at higher loading. NH3-TPD characterization and FTIR analysis of adsorbed pyridine demonstrated that only Lewis weak acids were present on catalyst surface and the amount of Mo loading has little effect on the strength of the surface acid on MoO3/SiO2. The catalytic results exhibited that the synergetic effect of Mo active centers with weak Lewis acid sites catalyzed transesterification of DMO with phenol.

The transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out in liquid phase under facile catalytic conditions. A series of bimetallic, MoO3-SnO2/SiO2, catalysts with various Mo and Sn content were prepared by sequential impregnation of cationic Mo species and cationic Sn complexes using impregnation method. The effects of mass ratio of Mo:Sn, amount of Sn additive, and Mo(Sn) laoding amount on activities of transesterification of dimethyl oxalate with phenol were investigated. The evaluation results showed that MoO3-SnO2/SiO2 catalyst with 14 wt% Mo(Sn) content performed best, giving 74.6% DMO conversion and 99.5% selectivity to MPO and DPO. This new heterogeneous catalyst provided not only an excellent selectivity (99% to MPO and DPO) and high yield of MPO and DPO but also a simple and practical protocol for DPC synthesis.

The transesterification of dimethyl oxalate (DMO) with phenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out over TiO2/SiO2 catalyst. The evaluation results showed that TiO2/SiO2 had better activity and excellent selectivity to target products compared with many conventional ester exchange catalysts. The total selectivity to MPO and DPO kept about 99.0% over TiO2/SiO2 and the conversion of DMO was 66.7% at 10% Ti loading, which was the maximum at different Ti loading. The structure and the chemical state of titanium species in TiO2/SiO2 had been investigated by XRD and XPS. The surface Ti(Ⅳ) species in the form of a monolayer was dominant until 6% Ti loading, while crystalline TiO2 was detected at 8% Ti loading. IR of adsorbed pyridine and NH3-TPD characterization indicated that the desirable catalytic activity of TiO2/SiO2 could be ascribed to its weak Lewis acid. Lewis acid sites cooperated with TiO2 to catalyze the synthesis of MPO and DPO.

The influence of molybdenum content on the catalytic performance in the transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was investigated. The results indicated that the MoO3/Al2O3 catalyst with 14wt% Mo content gave maximal DPO yield with 6.1% and 75.1% DMO conversion. The component, structure and phase of MoO3/Al2O3 catalysts were characterized by means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH3-TPD), and FTIR analysis of adsorbed pyridine.

The transesterification of dimethyl oxalate (DMO) with phenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out over a SnO2/SiO2 catalyst. The evaluation results showed that SnO2/SiO2 had better activity and total selectivity to MPO and DPO than many conventional ester exchange catalysts. Especially, SnO2/SiO2 was in favor of the disproportionation of MPO into DPO compared with TS-1, MoO3/SiO2, and MoO3-SnO2/SiO2 catalysts. The conversion of DMO was 46.7% and the selectivity to DPO was 22.5% at 8% Sn loadings, which was the maximum at different Sn loadings. IR of adsorbed pyridine and NH3-TPD characterization indicated that the desirable catalytic activity of SnO2/SiO2 could be ascribed to its weak Lewis acidity. The structure and chemical state of tin species in SnO2/SiO2 had been investigated by X-ray diffraction. SnO2 active centers dispersed on a SiO2 carrier with a high specific surface area were of benefit to the transesterification.

The transesterification of dimethyl oxalate (DMO) with phenol over stannum modifiedH was conducted to prepare diphenyl oxalate (DPO) used to produce diphenyl carbonate (DPC). The component, structure and phase of Hβ catalysts with various Sn loadings were investigated. The relationship between the catalytic properties and the amount of Sn loadings was discussed. The catalyst of H with 2wt.% Sn loading based on metal performed best, giving 75.3% conversion of DMO and 24.0% selectivity to DPO. At Sn loadings below 2wt.%, Sn was highly dispersed as monolayer, but at higher loadings it was crystallized into bulk tin dioxide, and the catalytic activity decreased. The curve of XPS peak intensity ratio of Sn 3d/Si 2p versus Sn loadings estimated the dispersed capacity of Sn on Hβ to be 2.1% Sn loading, which was in good agreement with the value obtained from XRD analysis. NH3-TPD results showed that the amount of Sn loading had effect only on the strength of the weak surface acid sites on Hβ. And the decrease of selectivity to anisole was not due to the change of the weak acid sites. Maybe, SnO2 accelerated to the formation of MPO and DPO. FTIR analysis of adsorbed pyridine showed that many Lewis acid sites and few Brönsted acid sites were present on Hβ catalysts with or without Sn modified. The acid sites together with SnO2 active centers catalyzed the transesterification of DMO with phenol. Especially, SnO2 active centers were in favor of the disproportionation of MPO into DPO.