Showing papers by "Gongying Wang published in 2017"

Influence of coordination groups on the catalytic performances of organo-titanium compounds for disproportionation of methyl phenyl carbonate to synthesize diphenyl carbonate

Abstract: The disproportionation of methyl phenyl carbonate (MPC) to synthesize diphenyl carbonate (DPC) catalyzed by organo-titanium compounds with different coordination groups was systematically investigated. The results of the molecular structure analysis, the catalytic performance evaluation and the chemical computational studies revealed that both the electron effect and steric hindrance of the coordination groups together affected the active Ti center and therefore influenced the catalytic performance of the catalysts. The influence of the electron effect was more important than the steric hindrance. The catalytic activity is in the order of Ti(O- i C 3 H 7 ) 4 > Ti(OC 6 H 5 ) 4 > Ti(OC 4 H 9 ) 4 > TiO(OOCCH 3 ) 2 > TiO(acac) 2 > Cp 2 TiCl 2 , and Ti(O- i C 3 H 7 ) 4 exhibited the best catalytic performance, due to its appropriate steric hindrance and electron effect for the coordination group. Under the optimum condition (n(Cat.)/n(MPC) = 0.04, reacted at 180 °C for 3 h), the MPC conversion of 90.4% and DPC selectivity of 99.6% were attained, respectively, which are comparable to those of other catalysts reported. Moreover, the catalyst is low cost, non-toxic and easily obtained by readily commercial-available purchase, and this catalytic system is also easy operation and convenient-controllable, indicating that it is conducive to future industrial application. In addition, a possible reaction mechanism catalyzed by the organo-titanium compounds with Lewis acid was also proposed for the process.

Investigation of Active Center of Cu‐Based Catalyst for Low Temperature Methanol Synthesis from Syngas in Liquid Phase: The Contribution of Cu+ and Cu0

Abstract: LaCuMn catalyst was prepared under different reduction temperature and passivation time, and used to catalyze CO hydrogenation to methanol in liquid phase. The effect of reductive copper species on the catalytic activity and the product distribution was studied. The results showed that the surface content of reductive copper species greatly affect the catalytic activity and the approximate molar ratio of Cu+ to Cu0 was important. The mixture of CuZn/AC-N2 with only Cu+ and CuZn/AC-H2 with only Cu0 was utilized for the low temperature methanol synthesis from syngas in liquid phase. It was confirmed that both of the reductive copper species of Cu+ and Cu0 were active species and Cu+ was superior to Cu0. Moreover, the synergic function of Cu+ and Cu0 led to the enhancement of the catalytic activity of Cu based catalyst, and the optimum molar ratio of surface Cu+ to Cu0 was in the range of 3.5 to 4.0.

Zn-promoted synthesis of diphenyl carbonate via transesterification over Ti–Zn double oxide catalyst

Abstract: An environmentally friendly heterogeneous catalyst, Ti–Zn double oxide, was prepared using a sol–gel method and firstly used for the synthesis of diphenyl carbonate (DPC) via the transesterification of phenol and dimethyl carbonate. The catalyst exhibited excellent catalytic activity. Moreover, the effects of Ti to Zn molar ratio, calcination temperature and catalyst amount on the catalytic performances of Ti–Zn double oxide have been investigated. The characterization results of XRD, TGA–DSC, ICP-AES and NH3-TPD showed that amorphous TiO2 was the active sites, and amorphous ZnO was the promoter. Also the amount of Zn remarkably affected the acid amounts of the catalysts, and the calcination temperature not only influenced the acid amount, but also affected the acid strength. Besides, the weak surface acid sites were responsible for the synthesis of MPC and DPC, whereas the strong acid sites favored the formation of a by-product, anisole. The phenol conversion and the transesterification selectivity reached 41.2 and 98.2% over 0.3 g 5TiZn-250 for 8 h, respectively. Furthermore, the prepared catalyst could be reused for three runs without drastic decrease in activity. The slight decreased activity was attributed to the phase change of Ti–Zn double oxide and the leaching of Ti.

Structure-activity correlations of calcined Mg-Al hydrocalcites for aliphatic polycarbonate synthesis via transesterification process

Abstract: Mg-Al mixed oxides with different Mg/Al molar ratio were prepared by thermal decomposition of hydrotalcitelike precursors at 500 °C for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with 1,4-butanediol to synthesize high-molecular-weight poly(butylene carbonate) (PBC). The structure-activity correlations of these catalysts in this transesterification process were discussed by means of various characterization techniques. It was found that the chain growth for the formation of PBC can only be obtained through connecting ―OH and ―OC(C)OC6H5 end-group upon removing the generated phenol, and the sample with Mg/Al molar ratio of 4.0 exhibited the best catalytic performance, giving PBC with Mw of 1.64 × 105 g/mol at 210 °C for 3.0 h. This excellent activity depended mainly on the specific surface area and basicity rather than pore structure or crystallite size of MgO.

Improvement of thermal stability, crystallinity and degradation of poly(butylene carbonate) by incorporation of bio‐based poly(ethylene sebacate) segment

Abstract: Multiblock poly(carbonate-co-esters) (PBC-PESe) containing poly(butylene carbonates) (PBC) and bio-based poly(ethylene sebacate) (PESe) had been synthesized successfully by chain-extension of dihydroxyl terminated PBC (PBC-OH) and PESe (PESe-OH) using 1,6-hexmethylene diisocyanate as chain extender. The chemical structures, molecular weights, crystallization behaviors, and thermal and degradation properties of the copolymers were all characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, polarized optical microscope, thermogravimetry analysis, water contact angle, and hydrolytic degradation. The resulting copolymers PBC-PESe all had a sole glass transition temperature (Tg), indicating the two segments, PBC and PESe, were well compatible in the amorphous phase. PESe segment acted a significant role on enhancing the thermal degradation temperature and hydrolytic degradation rate of multiblock copolymers. And the crystallization rate of PBC got dramatically accelerated after PESe segment was incorporated. However, the crystallization mechanism did not change. Furthermore, the mechanical properties of multiblock copolymers could be adjusted by changing the feed composition. Copyright © 2017 John Wiley & Sons, Ltd.