Tong Chen

Core-shell TiO2@SiO2 catalyst for transesterification of dimethyl carbonate and phenol to diphenyl carbonate

Abstract Core-shell TiO 2 @SiO 2 was prepared using a combination of reverse microemulsion and precipitation methods and used as a heterogeneous catalyst for the transesterification of dimethyl carbonate and phenol. TiO 2 @SiO 2 calcined at 200 °C gave the best catalytic performance. When the amount of catalyst was 0.20 g, the phenol conversion and transesterification selectivity were 41.8% and 100%, respectively. Transmission electron microscopy was used to characterize the core-shell TiO 2 @SiO 2 structure, and the results showed that TiO 2 @SiO 2 is bilayer with a TiO 2 core of diameter 220–300 nm and SiO 2 shell of thickness 40–60 nm. The TiO 2 @SiO 2 was reusable, and phenol conversion remained above 40% when the TiO 2 @SiO 2 was used four times. The catalytic performance of TiO 2 @SiO 2 in the transesterification of dimethyl carbonate and phenol was promoted by the formation of Ti–O–Si bonds.

Synthesis of Propylene Carbonate from Carbon Dioxide and o-Chloropropanol

Abstract A new route of synthesis of propylene carbonate from carbon dioxide and o -chloropropanol was studied. Catalytic activity of several inorganic solid bases and an organic amine was compared for the reaction. The results show that potassium carbonate and triethylamine both exhibit high activity. The catalytic system of K 2 CO 3 -N(Et) 3 has higher propylene carbonate yield than that of either K 2 CO 3 or N(Et) 3 itself. Under the optimal reaction conditions, 98% o -chloropropanol conversion and 95% propylene carbonate selectivity were obtained on K 2 CO 3 -N(Et) 3 .

Preparation and catalytic property of modified multi-walled carbon nanotube-supported TiO2 for the transesterification of dimethyl carbonate with phenol

Abstract Modified multi-walled carbon nanotube-supported TiO2 samples were prepared and used as an efficient heterogeneous catalyst for the transesterification of dimethyl carbonate with phenol. The catalysts were characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption-desorption, and X-ray powder diffraction. The results showed that the catalyst, which was prepared using a low concentration (0.4%) of ammonium hydroxide as the precipitant instead of ionized water, had better catalytic activity, separability, and reusability properties. The effects of the TiO2 loading, amount of catalyst and reaction time on the performance of the transesterification reaction were also studied. Under the optimum reaction conditions, the conversion of phenol reached 42.5% with over 99.9% selectivity for methyl phenyl carbonate and diphenyl carbonate. The catalyst could be reused for the transesterification in four runs with only slight loss of its catalytic activity.

Synthesis of Diphenyl Carbonate via Transesterification Catalyzed by HMS Mesoporous Molecular Sieves Containing Heteroelements

Abstract Heteroelements-containing mesoporous molecular sieves Me-HMS (Me = the incorporated metal) were prepared by the hydrothermal synthesis method and used for the synthesis of diphenyl carbonate (DPC) by transesterification between dimethyl carbonate (DMC) and phenol. Low angle X-ray diffraction patterns showed that all samples have typical of hexagonal phase structure. Among all tested Me-HMS samples, Ti-HMS exhibited the best catalytic performance, and the activity was closely related to the intra-framework Ti species content. When the molar ratio of Ti/Si in sol–gel reached 1/30, the amount of intra-framework Ti species in Ti-HMS was closed to saturation, and the maximum phenol conversion of 31.4% and the transesterification selectivity of 99.9% were obtained.

Transesterification of Phenol and Dimethyl Carbonate Catalyzed by Titanium Oxide Acetylacetonate Catalyst

Titanium oxide acetylacetonate (TiO(acac)2) was found to be a novel and efficient heterogeneous catalyst for the transesterification of phenol and dimethyl carbonate (DMC) to diphenyl carbonate (DPC). The conversion of phenol was 45.8% on the TiO(acac)2 pretreated at 180 °C, and the turnover number reached 96, which was better than the more common organic titanium catalyst. The effect of the amount of catalyst on the catalytic performance was investigated. The transesterification selectivity decreased with catalyst loadings over 0.2 g per 100 ml reactants. At the optimized amount of catalyst the conversion of phenol was 42.4%, and no anisole was detected. In particular, the TiO(acac)2 catalyst proved reusable, and catalytic activity of the recovered TiO(acac)2 was almost the same as that of the fresh catalyst. The conversion of phenol 40.0% was attained from TiO(acac)2 recovered for the fifth time.

V–Cu Composite Oxide Catalyst for Transesterification of Dimethyl Carbonate with Phenol to Diphenyl Carbonate

Abstract The V–Cu composite oxide catalyst was prepared by coprecipitation and used for the synthesis of diphenyl carbonate (DPC) by transesterification of dimethyl carbonate (DMC) with phenol. The effect of the molar ratio of V:Cu and the reusability of the catalyst were investigated. The catalyst showed the highest activity at a V:Cu molar ratio of 4:1. Under the conditions of 150–180°C and 9 h, the conversion of phenol and the transesterification selectivity over the V–Cu catalyst were 37.0% and 96.8%, respectively. According to the X-ray diffraction results, the V–Cu composite oxide was composed of crystalline V 2 O 5 and CuV 2 O 6 at V:Cu = 4:1. Both crystalline V 2 O 5 and CuV 2 O 6 were the active phase. In addition, the catalyst activity was reduced from 37.0% to 23.7% after the catalyst was reused three times. However, the used catalyst could be easily regenerated by calcination at 550°C in air for 5 h, and the catalytic activity of the regenerated catalyst was almost as high as that of the fresh sample.

Mesoporous silica-anchored organotin as heterogeneous catalyst for the transesterification of dimethyl carbonate with phenol

A simple scheme for a mesoporous silica-anchored organotin catalyst was developed for the transesterification of dimethyl carbonate with phenol to diphenyl carbonate. N2-sorption, TEM, UV–Vis, and elemental analysis combined with 29Si and 13C NMR measurements evidenced the formation of mesoporous organic–inorganic hybrid silica with a highly dispersed tetrahedral Sn species. The catalyst exhibited excellent activity and reusability in the transesterification. With a catalyst of 1.0xa0g, a reaction temperature of 150–180xa0°C, and a reaction time of 9xa0h, the phenol conversion and transesterification selectivity reached 51.1 and 99.9xa0%, respectively. The phenol conversion just decreased from 41.2 to 35.0xa0% after five runs with 0.5xa0g of catalyst. The improved stability was attributed to the strong covalent bonding between the organotin and mesoporous silica.

Solvent-free thermal decomposition of methylenediphenyl di(phenylcarbamate) catalyzed by nano-Cu2O

Methylene di(phenylisocyanate) (MDI) was prepared by thermal decomposition of methylenediphenyl di(phenylcarbamate) (MDPC) under solvent-free conditions with a nano-Cu2O catalyst. The preparation of nano-Cu2O was investigated in detail to obtain the optimal catalytic performance. The thermal decomposition reaction conditions, including reaction temperature, reaction pressure, and reaction time, were studied in the presence of nano-Cu2O. The results show that Cu2O prepared using a hydrolysis method and then calcined at 300 °C in Ar atmosphere for 2 h exhibited the optimal catalytic activity. The optimal reaction conditions were as follows: mass ratio of catalyst to MDPC 6.0 × 10−4, reaction temperature 220°C, reaction time 12 min, and reaction pressure 0.6 kPa. Under these conditions, the conversion of MDPC reached 99.8% and 86.2% MDI selectivity was achieved.

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

Abstract The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO22 with the weight ratio of MPA to TiO2 as 5:1.

The role of RGO in TiO 2 –RGO composites for the transesterification of dimethyl carbonate with phenol to diphenyl carbonate

TiO2–RGO composites were prepared and used as efficient heterogeneous catalysts for the transesterification of dimethyl carbonate with phenol. Transmission electron microscopy images demonstrated that the RGO could remarkablely improve the dispersion of TiO2. X‐ray photoelectron spectroscopy showed that RGO could change the chemical states of Ti species. Py-IR and Py-TPD results indicated the addition of RGO led to the increase of medium Lewis acid sites of TiO2, which are positive for the transesterification reaction. The TiO2–RGO composite with 50xa0wt% RGO exhibited a remarkable catalytic performance for the transesterification of dimethyl carbonate with phenol to diphenyl carbonate. Under the optimized conditions, the 53.5% phenol conversion and 99.9% transesterification selectivity were achieved. This phonel conversion of 53.5% could be compared with the result of homogeneous catalysts. RGO has been an excellent structural and electronic promoter in TiO2–RGO composites.