Zhang F.,CAS Chengdu Institute of Organic Chemistry |
Zhang F.,University of Chinese Academy of Sciences |
Yu X.,University of Sichuan |
Ma F.,CAS Chengdu Institute of Organic Chemistry |
And 9 more authors.
Cuihua Xuebao/Chinese Journal of Catalysis | Year: 2014
MoO3/SiO2 catalysts for the transesterification of dimethyl oxalate (DMO) with phenol were prepared by both the thermal spreading (TS) and incipient wetness impregnation methods. The results showed that the 10%MoO3/SiO2 catalyst prepared by TS (10%MoO3/SiO2-TS) exhibited higher catalytic performance compared with the 10%MoO3/SiO2 catalyst prepared by incipient wetness impregnation (10%MoO3/SiO2-C). The catalysts were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, pyridine-IR spectroscopy, and NH3 temperature- programmed desorption. These analyses indicated that weak Lewis acid sites were formed on the catalyst surfaces and that the Mo species were present as monomeric MoO3 rather than as isolated molybdenum oxide or polymolybdate species on both catalysts, although the 10%MoO3/SiO2-TS exhibited better dispersion of MoO3 and a higher surface Mo content than the 10%MoO3/SiO2-C. Under the optimal transesterification reaction conditions (1.2 g 10%MoO3/SiO2-TS, T = 180°C, n(DMO)/n(phenol) = 2, t = 4 h), the conversion of phenol was 70.9%, and the yields of methyl phenyl oxalate and diphenyl oxalate were 63.1% and 7.7%, respectively. © 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Liu F.,CAS Chengdu Institute of Organic Chemistry |
Liu F.,University of Chinese Academy of Sciences |
Yang X.-G.,CAS Chengdu Institute of Organic Chemistry |
Yang X.-G.,Chengdu Organic Chemicals Co. |
And 9 more authors.
Acta Polymerica Sinica | Year: 2014
The synthesis of poly ( 1 ,4-hutylene carbonate) ( PBC ) catalyzed by TiO2-SiO2 ( PVP-gel) was studied via a two-step melt transesterification of diphenyl carbonate and 1 ,4-butanediol. After pre- polymerization of diphenyl carbonate and 1 ,4-butanediol in the standard atmosphere, the vacuum condensation reaction was operated. The PBC was characterized by IR,NMR,GPC and DSC. The experimental results showed that the optimum conditions of the reaction were as follows; the reaction time and reaction temperature were 2 h and 220 ∼ 230 ° C, ( N2 protection) Respectively, in the standard atmosphere pre-polymerization step. The reaction time, reaction pressure and the catalyst dosage were 2 h,≤ 300 Pa and 0. 15 wt% , respectively, in the vacuum condensation step. The properties of the PBC prepared in optimum conditions ,were as follows; [η] was 1. 12 dL/g, the Mn was 49000, the Mw was 101000, the poiydispersity index was 2. 07, the Tg was -32.32°C ,the terminal hydroxyl content was 6. 2 × 10 -4 mol/g and the residue of the phenol was 5. 26 wt% . The polymerization degree of PBC can be controlled by the evaporation rate and yield of phenol under the technological conditions. And the phenol by-product was recycled almost completely.
Zhang F.-B.,CAS Chengdu Institute of Organic Chemistry |
Zhang F.-B.,University of Chinese Academy of Sciences |
Wang Q.-Y.,CAS Chengdu Institute of Organic Chemistry |
Wang Q.-Y.,Chengdu Organic Chemicals Co. |
And 6 more authors.
Journal of Molecular Catalysis | Year: 2014
The catalytic performance of several organotitanium compounds for transesterfication of dimethyl oxalate with phenol was investigated. The results showed that the catalytic activities and selectivities were in the order: Cp2TiCl2>Ti(OPh)4 >Ti(OBu)4>TiO(acac)2 >Ti(OEt)4>Ti(OEt)4. This means that Cp2TiCl2 was an efficient transesterfication catalyst compared to the others. Under the optimal conditions (n(Cp2TiCl2)=0.001 mol, n(DMO)=0.3 mol, n(Phenol)=0.2 mol, T=180°C, t=2 h ), the conversion of phenol reached 44.0%, and the yield of MPO and DPO were 37.8% and 6.1%, respectively, while the total transesterfication selectivity was 99.8%.