Gongying Wang

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.

Hydrated Alkali Metal Halides as Efficient Catalysts for the Synthesis of Cyclic Carbonates from CO2 and Epoxides

The synthesis of propylene carbonate from carbon dioxide and propylene oxide using hydrated alkali metal halides as catalysts in the absence of a co-catalyst and a solvent was investigated. The hydrated alkali metal halides showed much higher catalytic activity than the anhydrous alkali metal halides. Sodium iodide dihydrate was found to be the most efficient among them and it gave a 97% yield of propylene carbonate at 120 °C under 1 MPa within 1.5 h. The corresponding cyclic carbonates from CO2 and other epoxides using sodium iodide dihydrate as catalyst were also successfully synthesized.

A highly efficient catalyst for direct synthesis of methyl acrylate via methoxycarbonylation of acetylene

A non-petroleum approach for the catalytic synthesis of methyl acrylate via methoxycarbonylation of acetylene with carbon monoxide and methanol as nucleophilic reagent has been studied under various conditions. Pd(OAc)2/2-PyPPh2/p-tsa was found to be a highly efficient catalytic system. The types of phosphorus ligands and their concentration was a determinative factor for catalytic activity. Mono-dentate phosphorus ligand such as triphenylphosphine has no activity while 2-(diphenylphosphino)pyridine with a mixed N-P bidentate structure has an excellent activity. Catalytic performance of acids depends on their acidic strength and coordinative property. Among all acidic promoters, p-toluenesulfonic acid displayed an excellent performance. Other parameters such as solvent polarity and initial pressure of carbon monoxide have also important influences on the hydroesterification of acetylene. It is beneficial for the reaction that the solvents have a high polarity. At low pressure of carbon monoxide, to high active palladium catalyst, the reaction easily proceeded. However, at high pressure of carbon monoxide, acetylene will transfer from solution to gas phase, resulting in lower conversion of acetylene. In addition, due to steric hindrance of alcohols, methanol has a highest activity in hydroesterification of acetylene in low carbon alcohols. Under the optimal reaction conditions, 99.5% of acetylene conversion and 99.7% of selectivity toward methyl acrylate as well as 2,502 h−1 TOF were achieved.

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.

One-pot synthesis of high-molecular-weight aliphatic polycarbonates via melt transesterification of diphenyl carbonate and diols using Zn(OAc)2 as a catalyst

A simple and efficient route for one-pot synthesis of high-molecular-weight aliphatic polycarbonates (APCs) by direct melt transesterification of diphenyl carbonate (DPC) with aliphatic diols at equimolar amounts was developed. Zn(OAc)2 was found to be the best catalyst for this reaction among the screened transition metal acetates. The effects of reaction conditions on Mw and yield of the poly(1,4-butylene carbonate) (PBC) were investigated, where the highest Mw of 156200 g mol−1 with a yield of 83% was obtained under suitable reaction conditions. In addition, based on the results of thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), a plausible reaction mechanism over Zn(OAc)2 was proposed for APC synthesis.

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.

Preparation of Nano-TiO2 by Ethanol-Thermal Method and Its Catalytic Performance for Synthesis of Dibutyl Carbonate by Transesterification

Abstract The preparation of nano-TiO2 powder by the ethanol-thermal method at atmospheric pressure using ethanol as the solvent, H2TiO3 as the precursor, and NH3·H2O, NaOH or KOH as the mineralizer was studied. The X-ray diffraction result shows that the structure of TiO2 is anatase, and with the increase in mineralizer alkalinity, the average diameter of TiO2 becomes smaller, and the crystallinity of TiO2 becomes higher. The diameter and crystallinity of TiO2 affect its catalytic activity for the synthesis of dibutyl carbonate (DBC) from dimethyl carbonate (DMC) and n-butyl alcohol. The anatase TiO2 obtained from KOH exhibits the highest catalytic activity, giving 61.9% conversion of DMC, 100% selectivity for DBC, and 61.9% yield of DBC. The catalyst activity remains almost unchanged through four reuses.

Synthesis of metal organic framework (MOF-5) with high selectivity for CO2/N2 separation in flue gas by maximum water concentration approach

Water plays a crucial role in the synthesis mechanism of metal organic framework-5 (MOF-5). Synthesized MOF-5 with good phase structure and large specific surface area is largely determined by an important synthesis factor: the total water concentration of the initial synthesis solution (Ctw). An understanding of the effects of different and high Ctw on the synthesis of MOF-5 and the investigation of the maximum Ctw suitable for the synthesis of MOF-5 are important to guide the synthesis of MOF-5. Through the research of the maximum Ctw, a favorable synthetic approach was established which could realize the synthesis of MOF-5 with fine performance on CO2 adsorption and separation. The research results show that the maximum Ctw could be as high as 1,440mmol/L, and synthesized MOF-5 still has a good phase structure and a large specific surface area of 2,136m2/g (BET). Synthesized MOF-5 by the maximum Ctw exhibits a high CO2 adsorption capacity of 2.5mmol/g and a low N2 adsorption capacity of 0.2mmol/g at 298 K and 100 kPa. More importantly, synthesized MOF-5 by the maximum Ctw exhibits a high selectivity for CO2/N2 of 18-22 at 298 K and 20-130 kPa in simulated flue gas.

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.