High-molecular-weight aliphatic polycarbonates（APCs） were synthesized through a two-step transesterification process under solvent-free conditions. Oligomers with equal numbers of hydroxyl and phenyl carbonate termi...High-molecular-weight aliphatic polycarbonates（APCs） were synthesized through a two-step transesterification process under solvent-free conditions. Oligomers with equal numbers of hydroxyl and phenyl carbonate terminal groups could be easily controlled by using equimolar amounts of diphenyl carbonate（DPC） and aliphatic diols as feedstocks in the first step. In the second step, the high-molecular-weight APCs can be obtained by connecting -OH with -OC（O）OC6H5 end-group upon removing the generated phenol at reduced pressure. Mg（OAc）2 was found to be the best catalyst for this process among the screened catalysts, which gave the poly（l,4-butylene carbonate）（PBC） a weight-average molecular weight（Mw） of 148600 and a yield of 84.8% under its suitable reaction conditions. In addition, based on the results of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fourier transform infrared spectroscopy（FTIR）, a possible reaction mechanism over Mg（OAe）2 was proposed for APCs synthesis.展开更多
MgO loaded with KF was prepared by using tlie impregnation method and was employed as the catalyst for tlie direct traiisesterification of diphenyl carbonate(DPC) witli isosorbide to synthesize high-molecular-weight p...MgO loaded with KF was prepared by using tlie impregnation method and was employed as the catalyst for tlie direct traiisesterification of diphenyl carbonate(DPC) witli isosorbide to synthesize high-molecular-weight poly(isosorbide carbonate)(PIC). The relationship between physical-chemical properties and catalytic performance for KF/MgO in this melt process was investigated by various characterization techniques. The basic site amount and strength were found to be responsible for this transesterification process, and the medium and strong basic sites tended to promote the polycondensation reaction. 20-KF/Mg0-500 exhibited the best catalytic performance, giving PIC with Mw of 84200 and glass transition temperature(rg) of 173℃ under optimal conditions. Additionally, 20-KF/MgO-500 was found to catalyze the transerification of DPC with isosorbide and other diols to syntliesize the corresponding poly(aliphatic diol-co-isosorbide carbonate)s(PAICs). This excellent activity can be ascribed to the presence of an abundance of basic sites and their specific basic strength on the surface of KF/MgO.展开更多
The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fo...The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield of phenol,and its catalytic activity in the polycondensation process is determined by the number-average molecular weight(Mn) and the hydroxyl value.Compared to the triethylenediamine(C6H12N2),Mg-Al layered double hydroxide(Mg-Al LDH),sodium ethoxide(C2H5ONa) and sodium methoxide(CH3ONa),MOF-5 exhibits highest catalytic activity for the preparation of PCDL.Under reaction conditions(n(1,6-HD)/n(DPC) = 1.2,w(catalyst) = 0.03%,198 ℃),the yield of phenol is up to 90.1% and the PCDL shows highest Mn and lowest hydroxyl value.展开更多
A complete study on the catalytic activity of stannous oxalate for poly(trimethylene terephthalate) (PTT) synthesis via esterification method is carried out by comparison to the well known catalysts (tetrabutyl titana...A complete study on the catalytic activity of stannous oxalate for poly(trimethylene terephthalate) (PTT) synthesis via esterification method is carried out by comparison to the well known catalysts (tetrabutyl titanate (TBT), dibutyltin oxide (Bu2SnO), and stannous octoate (SOC)). Their catalytic activity in the esterification process is monitored by measuring the amount of water generated, while intrinsic viscosity (IV) and content of terminal carboxyl groups (CTCG) are used as the index in the polycondensation process. Stannous oxalate shows higher activity than the other catalysts. Decrease in reaction time and improvements in PTT property are observed. The higher catalytic activity of stannous oxalate is attributed to its chelate molecular structure.展开更多
An environmentally friendly heterogeneous catalyst, C60-doped TiO2（denoted as C60-TiO2）, was prepared and firstly used to catalyze the synthesis of diphenyl carbonate（DPC） via the transesterification of phenol and...An environmentally friendly heterogeneous catalyst, C60-doped TiO2（denoted as C60-TiO2）, was prepared and firstly used to catalyze the synthesis of diphenyl carbonate（DPC） via the transesterification of phenol and dime- thyl carbonate（DMC）. The characterization results of FTIR, XRD, XPS, SEM, TEM and digital optical micro- scope（MIC） show that C60 promotes the dispersion of TiO2 and the prepared conditions affect the dispersion and the electron density of Ti species. The C60-TiO2-8[n（Ti）：n（C60）=8：1] prepared with toluene and calcined at 200 ℃ exhi- bits the best catalytic performance. The DPC selectivity of 86.5% attained over C60-TiO2-8 was much higher than that（about 50%） attained over Ti-based catalysts reported, which was originated from the electronic effect of C60 and the efficient dispersion of Ti species by C60. The phenol conversion slowly decreased from 34.4% to 26.7% after four consecutive runs due to the leach of Ti species. It also suggested that the C60 could relieve the leach of Ti species compared with other Ti-based catalysts reported. Moreover, C60-TiO：-8 exhibited excellent catalytic behavior for disproportionation of methyl phenyl carbonate（MPC） with high DPC selectivity.展开更多
Polycarbonate diols（PCDLs） with a number average molecular weight（M,） of 2800 and a narrow polydispersity index（PDI=1.33） were synthesized from dimethyl carbonate（DMC） and 1,4-butarlediol（BD） via a two-step ...Polycarbonate diols（PCDLs） with a number average molecular weight（M,） of 2800 and a narrow polydispersity index（PDI=1.33） were synthesized from dimethyl carbonate（DMC） and 1,4-butarlediol（BD） via a two-step process. The influences of the molar ratios of DMC to BD in the feedstock, polycondensation temperature and polycondensation time on the PCDLs preparation were studied. CH3COONa showed the best catalytic performance among the catalysts studied. The highest BD conversion of 73.8% and PCDLs yield of 64.7% were achieved under its optimum reaction conditions. Furthennore, based on the results of 1^H NMR, the relationships between the ratio of end groups （--OCH3/-OH） of oligomers, the Mn and chain-end constitute of resultant polycarbonates were also investigated. The results indicate that PCDLs can be synthesized when the oligomers mostly bear hydroxyl end groups. In contrast, it was impossible to prepare PCDLs when the oligomers were enriched with methyl carbonate end groups,展开更多
文摘High-molecular-weight aliphatic polycarbonates（APCs） were synthesized through a two-step transesterification process under solvent-free conditions. Oligomers with equal numbers of hydroxyl and phenyl carbonate terminal groups could be easily controlled by using equimolar amounts of diphenyl carbonate（DPC） and aliphatic diols as feedstocks in the first step. In the second step, the high-molecular-weight APCs can be obtained by connecting -OH with -OC（O）OC6H5 end-group upon removing the generated phenol at reduced pressure. Mg（OAc）2 was found to be the best catalyst for this process among the screened catalysts, which gave the poly（l,4-butylene carbonate）（PBC） a weight-average molecular weight（Mw） of 148600 and a yield of 84.8% under its suitable reaction conditions. In addition, based on the results of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fourier transform infrared spectroscopy（FTIR）, a possible reaction mechanism over Mg（OAe）2 was proposed for APCs synthesis.
文摘MgO loaded with KF was prepared by using tlie impregnation method and was employed as the catalyst for tlie direct traiisesterification of diphenyl carbonate(DPC) witli isosorbide to synthesize high-molecular-weight poly(isosorbide carbonate)(PIC). The relationship between physical-chemical properties and catalytic performance for KF/MgO in this melt process was investigated by various characterization techniques. The basic site amount and strength were found to be responsible for this transesterification process, and the medium and strong basic sites tended to promote the polycondensation reaction. 20-KF/Mg0-500 exhibited the best catalytic performance, giving PIC with Mw of 84200 and glass transition temperature(rg) of 173℃ under optimal conditions. Additionally, 20-KF/MgO-500 was found to catalyze the transerification of DPC with isosorbide and other diols to syntliesize the corresponding poly(aliphatic diol-co-isosorbide carbonate)s(PAICs). This excellent activity can be ascribed to the presence of an abundance of basic sites and their specific basic strength on the surface of KF/MgO.
基金supported by the Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (2006BAE02B03)Jiangsu Provincial Science & Technology Pillar Program (BE2010065)
文摘The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield of phenol,and its catalytic activity in the polycondensation process is determined by the number-average molecular weight(Mn) and the hydroxyl value.Compared to the triethylenediamine(C6H12N2),Mg-Al layered double hydroxide(Mg-Al LDH),sodium ethoxide(C2H5ONa) and sodium methoxide(CH3ONa),MOF-5 exhibits highest catalytic activity for the preparation of PCDL.Under reaction conditions(n(1,6-HD)/n(DPC) = 1.2,w(catalyst) = 0.03%,198 ℃),the yield of phenol is up to 90.1% and the PCDL shows highest Mn and lowest hydroxyl value.
基金Supported by the National High Technology Research and Development Program of China 863 Plan (Grant No. 2003AA321010) the Innovation Research Fund of Graduate University, Chinese Academy of Sciences (2006)
文摘A complete study on the catalytic activity of stannous oxalate for poly(trimethylene terephthalate) (PTT) synthesis via esterification method is carried out by comparison to the well known catalysts (tetrabutyl titanate (TBT), dibutyltin oxide (Bu2SnO), and stannous octoate (SOC)). Their catalytic activity in the esterification process is monitored by measuring the amount of water generated, while intrinsic viscosity (IV) and content of terminal carboxyl groups (CTCG) are used as the index in the polycondensation process. Stannous oxalate shows higher activity than the other catalysts. Decrease in reaction time and improvements in PTT property are observed. The higher catalytic activity of stannous oxalate is attributed to its chelate molecular structure.
文摘An environmentally friendly heterogeneous catalyst, C60-doped TiO2（denoted as C60-TiO2）, was prepared and firstly used to catalyze the synthesis of diphenyl carbonate（DPC） via the transesterification of phenol and dime- thyl carbonate（DMC）. The characterization results of FTIR, XRD, XPS, SEM, TEM and digital optical micro- scope（MIC） show that C60 promotes the dispersion of TiO2 and the prepared conditions affect the dispersion and the electron density of Ti species. The C60-TiO2-8[n（Ti）：n（C60）=8：1] prepared with toluene and calcined at 200 ℃ exhi- bits the best catalytic performance. The DPC selectivity of 86.5% attained over C60-TiO2-8 was much higher than that（about 50%） attained over Ti-based catalysts reported, which was originated from the electronic effect of C60 and the efficient dispersion of Ti species by C60. The phenol conversion slowly decreased from 34.4% to 26.7% after four consecutive runs due to the leach of Ti species. It also suggested that the C60 could relieve the leach of Ti species compared with other Ti-based catalysts reported. Moreover, C60-TiO：-8 exhibited excellent catalytic behavior for disproportionation of methyl phenyl carbonate（MPC） with high DPC selectivity.
文摘Polycarbonate diols（PCDLs） with a number average molecular weight（M,） of 2800 and a narrow polydispersity index（PDI=1.33） were synthesized from dimethyl carbonate（DMC） and 1,4-butarlediol（BD） via a two-step process. The influences of the molar ratios of DMC to BD in the feedstock, polycondensation temperature and polycondensation time on the PCDLs preparation were studied. CH3COONa showed the best catalytic performance among the catalysts studied. The highest BD conversion of 73.8% and PCDLs yield of 64.7% were achieved under its optimum reaction conditions. Furthennore, based on the results of 1^H NMR, the relationships between the ratio of end groups （--OCH3/-OH） of oligomers, the Mn and chain-end constitute of resultant polycarbonates were also investigated. The results indicate that PCDLs can be synthesized when the oligomers mostly bear hydroxyl end groups. In contrast, it was impossible to prepare PCDLs when the oligomers were enriched with methyl carbonate end groups,
