A series of Mo-containing MFI zeolites with different Mo loadings(Mo-MFI-n,n represent the initial Si/Mo molar ratio)was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA co...A series of Mo-containing MFI zeolites with different Mo loadings(Mo-MFI-n,n represent the initial Si/Mo molar ratio)was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA complex as the Mo source.Various characterization results demonstrated that the use of the Mo-EDTA complex is beneficial for the incorporation of more Mo species into the MFI-type zeolites.The special complexing capability of EDTA^(2–)plays a critical role in adjusting the release rate of the Mo species to combine with the Si tetrahedron species during the zeolite growth process,thus leading to a uniform distribution of Mo in the MFI framework.In addition,a small portion of extra-framework Mo clusters may be distributed inside the channels or near the pore window of the zeolites.The catalytic properties of these Mo-containing MFI zeolites were evaluated for the epoxidation of cyclohexene with H_(2)O_(2)as the oxidant.The composition-optimized catalyst,Mo-MFI-50,efficiently converted cyclohexene to the corresponding epoxide with a relatively high conversion(93%)and epoxide selectivity(82%)at 75℃after 9 h of reaction.Moreover,the resultant Mo-containing MFI catalyst exhibited excellent structural stability and recoverability and was easily recycled by simple filtration without the need for calcination treatment.展开更多
Ti/BMMs （Ti supported bimodal mesoporous silica） catalysts have been prepared via self-assembly route com- bined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were investigated in ...Ti/BMMs （Ti supported bimodal mesoporous silica） catalysts have been prepared via self-assembly route com- bined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were investigated in the epoxidation of cyclohexene. In order to the evaluate the regeneration methods and to examine the deactivation behaviors, the deactivated Ti/BMMs catalysts were washed in chloroform or calcinated at 450 ℃ for 6 h and then activity of the recovery catalysts were examined. Meanwhile, the structure features and surface properties of the regenerated catalysts were characterized by X-ray diffraction, N2-sorption analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravi- metric analysis, UV visible spectroscopy and X-ray photoelectron spectroscopy. The results showed that the typical bimodal mesoporous structure of recycled Ti/BMMs catalysts was still maintained, and the phenomenon of Ti leaching during the catalytic process and recovery was negligible. In particular, spectroscopic observations indicated that the effects of the regeneration methods on the tetrahedrally-coordinated Ti species and catalytic deactivation were remarkable. The main reasons were related to the polarities of used solvents during recovery tests, the environment medium of adsorbed water inside mesopore channels and the deposition of bulky mole- cules of by-products on the mesoporous surface.展开更多
Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-ge...Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-gen gas flow rate on the conversion of cyclohexene and selectivity of cyclohexene oxide were investigated and dis-cussed, and the optimal operation condition was found, under which 95.2% conversion of cyclohexene and 90.7% selectivity of cyclohexene oxide were achieved. The ultrasonic airlift loop reactor utilizes the synergistic effect of sonochemsitry and higher oxygen transfer rate. Possible reaction mechanisms were outlined and the reason of ul-trasound promotion of epoxidation reactionwas analyzed.展开更多
Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}wit...Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}with long carbon chain and biquaternary ammonium cation.Cyclohexene could be epoxidized to cyclohexene oxide in 96.3%conversion and 98.2%selectivity.The catalyst type,solvent type,catalyst loading,initial molar ratio,temperature,cycle performance and substrate extensibility were studied and optimized,the kinetic parameters about overall reaction and unit reaction were also calculated.Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length.This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H_(2)O_(2).展开更多
Three new cyclohexene epoxides,polysyphoside A,B and C,along with a known compound crotepoxide(4),were isolated from Piper polysyphorum C.DC.Based on spectroscopic analysis,their structures were established as 1-benzo...Three new cyclohexene epoxides,polysyphoside A,B and C,along with a known compound crotepoxide(4),were isolated from Piper polysyphorum C.DC.Based on spectroscopic analysis,their structures were established as 1-benzoyloxymethylene-2-hydroxy-3-benzoyloxy-1,6- epoxycyclohex-4-ene(1),1-benzoyloxymethylene-2-hydroxy-5-benzoyloxy-1,6-epoxycyclohex-3-ene (2)and 2-hydroxy-3-benzoyloxymethylene-5-benzoyloxy-1,6-epoxycyclohex-3-ene(3),respectively.It was the first time that(1),(2)and(3)had been isolated from a natural source.展开更多
文摘A series of Mo-containing MFI zeolites with different Mo loadings(Mo-MFI-n,n represent the initial Si/Mo molar ratio)was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA complex as the Mo source.Various characterization results demonstrated that the use of the Mo-EDTA complex is beneficial for the incorporation of more Mo species into the MFI-type zeolites.The special complexing capability of EDTA^(2–)plays a critical role in adjusting the release rate of the Mo species to combine with the Si tetrahedron species during the zeolite growth process,thus leading to a uniform distribution of Mo in the MFI framework.In addition,a small portion of extra-framework Mo clusters may be distributed inside the channels or near the pore window of the zeolites.The catalytic properties of these Mo-containing MFI zeolites were evaluated for the epoxidation of cyclohexene with H_(2)O_(2)as the oxidant.The composition-optimized catalyst,Mo-MFI-50,efficiently converted cyclohexene to the corresponding epoxide with a relatively high conversion(93%)and epoxide selectivity(82%)at 75℃after 9 h of reaction.Moreover,the resultant Mo-containing MFI catalyst exhibited excellent structural stability and recoverability and was easily recycled by simple filtration without the need for calcination treatment.
基金Supported by the National Natural Science Foundation of China(21076003,21272005)the Funding Project for the Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of the Beijing Municipality(PHR201107104,005000541211019/20,005000543111517)
文摘Ti/BMMs （Ti supported bimodal mesoporous silica） catalysts have been prepared via self-assembly route com- bined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were investigated in the epoxidation of cyclohexene. In order to the evaluate the regeneration methods and to examine the deactivation behaviors, the deactivated Ti/BMMs catalysts were washed in chloroform or calcinated at 450 ℃ for 6 h and then activity of the recovery catalysts were examined. Meanwhile, the structure features and surface properties of the regenerated catalysts were characterized by X-ray diffraction, N2-sorption analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravi- metric analysis, UV visible spectroscopy and X-ray photoelectron spectroscopy. The results showed that the typical bimodal mesoporous structure of recycled Ti/BMMs catalysts was still maintained, and the phenomenon of Ti leaching during the catalytic process and recovery was negligible. In particular, spectroscopic observations indicated that the effects of the regeneration methods on the tetrahedrally-coordinated Ti species and catalytic deactivation were remarkable. The main reasons were related to the polarities of used solvents during recovery tests, the environment medium of adsorbed water inside mesopore channels and the deposition of bulky mole- cules of by-products on the mesoporous surface.
基金Supported by Qinglan Project Foundation of Jiangsu Province and Doctoral Dissertation Innovate Foundation of Nanjing Uni-versity of Technology (No.BSCS200508).
文摘Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-gen gas flow rate on the conversion of cyclohexene and selectivity of cyclohexene oxide were investigated and dis-cussed, and the optimal operation condition was found, under which 95.2% conversion of cyclohexene and 90.7% selectivity of cyclohexene oxide were achieved. The ultrasonic airlift loop reactor utilizes the synergistic effect of sonochemsitry and higher oxygen transfer rate. Possible reaction mechanisms were outlined and the reason of ul-trasound promotion of epoxidation reactionwas analyzed.
基金supported by Natural Science Foundation of Jiangsu Province(BK20210185)National Natural Science Foundation of China(21776122)。
文摘Selective epoxidation of olefins is an important field in chemical industry.In this work,we developed a new phosphotungstic acid catalyst{[(C_8H_(17))(CH_(3))_(2)N]_(2)(CH_(2))_(3)}_(1.5){PO_(4)[WO(O_(2))_(2)]_(4)}with long carbon chain and biquaternary ammonium cation.Cyclohexene could be epoxidized to cyclohexene oxide in 96.3%conversion and 98.2%selectivity.The catalyst type,solvent type,catalyst loading,initial molar ratio,temperature,cycle performance and substrate extensibility were studied and optimized,the kinetic parameters about overall reaction and unit reaction were also calculated.Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length.This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H_(2)O_(2).
文摘Three new cyclohexene epoxides,polysyphoside A,B and C,along with a known compound crotepoxide(4),were isolated from Piper polysyphorum C.DC.Based on spectroscopic analysis,their structures were established as 1-benzoyloxymethylene-2-hydroxy-3-benzoyloxy-1,6- epoxycyclohex-4-ene(1),1-benzoyloxymethylene-2-hydroxy-5-benzoyloxy-1,6-epoxycyclohex-3-ene (2)and 2-hydroxy-3-benzoyloxymethylene-5-benzoyloxy-1,6-epoxycyclohex-3-ene(3),respectively.It was the first time that(1),(2)and(3)had been isolated from a natural source.
