Two new polyoxygenated cyclohexenes, kweichowenol A and B were isolated from the leaves of Uvaria kweichowensis and their structures were established on the basis of their spectral data.
Two new polyoxygenated cyclohexenes,named uvacalolA(1),and B(2)were isolated from the rhizomes of Uvaria calamistrata.On the basis of spectral analysis and chemical derivatization,including preparation of Mosher ester...Two new polyoxygenated cyclohexenes,named uvacalolA(1),and B(2)were isolated from the rhizomes of Uvaria calamistrata.On the basis of spectral analysis and chemical derivatization,including preparation of Mosher esters,the structure of 1 to 2 were established.展开更多
In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified ...In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified with 4 mol·L^(-1) nitric acid was selected as an efficient catalyst for improving the hydration efficiency of cyclohexene.Furthermore,the microstructures and properties of fresh,used and regenerated acid-modified catalysts have been characterized by X-ray diffraction,scanning electron microscopy,nitrogen adsorption/desorption isotherm,Fourier transform infrared,thermal gravimetric analyzer,ammonia temperature programmed desorption and pyridine adsorbs Fourier transform infrared.The characterization results indicated that the total surface areas and pore volume of HZSM-5 zeolite increased after nitric acid treatment due to the formation of mesoporous structure.This benefits the diffusion rate of reactants and products,which improves the hydration efficiency and stability of the catalyst.Under the catalysis of HZSM-5,the conversion of cyclohexene was found to be 9.0%.However,treatment of HZSM-5 with nitric acid enhanced the conversion of cyclohexene to 12.2%,achieving a selectivity of 99.7%for cyclohexanol under optimal reaction conditions.This work affords a mild and efficient approach for improving the hydration efficiency and has potential industrial application value.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
A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4.The structure and acidity of the catalyst were characterized by Fourier transform infrared spec...A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4.The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy,scanning electron microscopy,X‐ray diffraction,thermogravimetric analysis,X‐ray photoelectron spectroscopy,and elemental analysis,which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations.Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g.The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid.At a3:1 molar ratio of formic acid to cyclohexene,catalyst loading of 0.07 g/mL of cyclohexene,and reaction time of 1 h at 413 K,the cyclohexene conversion was 88.4%with 97.3%selectivity to cyclohexyl formate.The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene,which deactivated HZSM‐5.The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing–SO3H groups and then it remained constant in the following reuse.展开更多
Oxidation of cyclohexene under 1 atmospheric pressure of molecular oxygen at 70C in the absence of solvent catalyzed by PAMAM-SA-M (Where PAMAM = polyamidoamine; SA = salicyaldehyde; M = metal ions Fe3+, Co2+, Ni2+, M...Oxidation of cyclohexene under 1 atmospheric pressure of molecular oxygen at 70C in the absence of solvent catalyzed by PAMAM-SA-M (Where PAMAM = polyamidoamine; SA = salicyaldehyde; M = metal ions Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Zn2+, respectively) dendrimers, afforded 2-cyclohexen-1-ol 1, 2-cyclohexen-1-one 2, 7-oxabicyclo [4,1,0] heptane 3 and 7-oxabicyl [4,1,0] heptan-2-one 4 as the major products. The factors that affect this reaction are also discussed.展开更多
A novel nanosized amorphous Ru-Fe-B/ZrO2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize ...A novel nanosized amorphous Ru-Fe-B/ZrO2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize and the amorphous character as well as to its textural character. In addition, the concentration of zinc ions, the content of ZrO2 in the slurry, and the pretreatment of the catalyst were found to be effective in improving the activity and the selectivity of the catalyst.展开更多
Ru-Ce catalysts were prepared by a co-precipitation method.The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO...Ru-Ce catalysts were prepared by a co-precipitation method.The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO4.The Ce species in the catalysts prepared with different valences of the Ce precursors all exist as CeO2 on the Ru surface.The promoter CeO2alone could not improve the selectivity to cyclohexene of Ru catalysts.However,almost all the CeO2 in the catalysts could react with the reaction modifier ZnSO4 to form(Zn(OH)2)3(ZnSO4)(H2O)3 salt.The amount of the chemisorbed salt increased with the CeO2 loading,resulting in the decrease of the activity and the increase of the selectivity to cyclohexene of Ru catalyst.The Ru-Ce catalyst with the optimum Ce/Ru molar ratio of 0.19 gave a maximum cyclohexene yield of 57.4%.Moreover,this catalyst had good stability and excellent reusability.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
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
Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N_2 adsorption isotherm.The results show that the hierarchical TS-1 aggregates cons...Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N_2 adsorption isotherm.The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20-30 nm.The BET surface area increases from 420 to 513 m^2/g compared to conventional TS-1 zeolite.The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.展开更多
Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promote...Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promoted with Zn or Mn alone. The optimum Mn/Zn molar ratio was determined to be 0.3. With the addition of 0.5 g NaOH, the Ru-Mn-Zn-0.3 catalyst, which was reduced at 150 ？ C, afforded a cyclohexene selectivity of 81.1% at a benzene conversion of 60.2% at 5 min and a maximum cyclohexene yield of 59.9% at 20 min. Based on characterizations, the excellent performance of Ru-Mn-Zn catalyst was ascribed to the suitable pore structure, the appropriate reducibility and the homogenous chemical environment of the catalyst.展开更多
Acidic poly(ionic liquid)s(PILs)with swelling ability were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids,divinylbenzene(DVB)and sodium acrylate(NaAA),and further acidification by sul...Acidic poly(ionic liquid)s(PILs)with swelling ability were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids,divinylbenzene(DVB)and sodium acrylate(NaAA),and further acidification by sulfuric acid.The swelling ability of acidic PILs was greatly affected by cross-linker content and chain length of 3-alkyl-substituents on imidazolium.Cross-linked network structures could be observed from the cryogenic scanning electron microscopy(cryo-SEM)images of the swollen acidic PILs in formic acid.Acidic PILs with network structures in swollen state exhibited excellent activities in the esterification of cyclohexene and formic acid,and the catalytic activities were in positive correlation with their swelling abilities.Acidic PIL with 3-octyl-substituent and 2.5 mol%DVB(PIL-C8-2.5DVB-HSO4)had the highest swelling ability in formic acid and exhibited comparable catalytic activities with homogeneous catalysts such as sulfuric acid and p-toluenesulfonic acid.展开更多
Molybdenum (VI) complex, namely molybdenum dioxobis(2,4-pentanedione) [MoO2(acac)2] used as epoxidation catalyst species, was synthesized and characterized by elemental analysis and infrared spectrum. Polystyrene-supp...Molybdenum (VI) complex, namely molybdenum dioxobis(2,4-pentanedione) [MoO2(acac)2] used as epoxidation catalyst species, was synthesized and characterized by elemental analysis and infrared spectrum. Polystyrene-supported molybdenum dioxobis(2,4-pentanedione) [MoO2(acac)2] for synthesis of epoxycyclohexane was prepared by phase transfer catalysis method. Effects of various factors in synthesis of epoxycyclohexane by reaction of cyclohexene and t-BuOOH in the atmosphere of nitrogen catalyzed by polystyrene-supported MoO2(acac)2 were also investigated. Under the following conditions, n(cyclohexene):n(t-BuOOH)=3.5:l (based on 0.1 mol of t-BuOOH), volume of solvent -10ml, reaction temperature -80℃, reaction time -60min, and mass of molybdenum in the catalyst -2.30×0^(-3)g, the yield of epoxycyclohexane on the basis of t-BuOOH is over 99.5%, and the purity of epoxycyclohexane is about 99.9% by gas chromatogram(GC) analysis.展开更多
A new compound, subglain B, was isolated from the stems of Uvaria tonkinensis var. subglabra and its structure was identified as 1S, 2R, 3S, 6R-1-benzoyloxymethylene-1,2- dihydroxy-3-benzoyloxy-6-chlorocyclohex-4-ene ...A new compound, subglain B, was isolated from the stems of Uvaria tonkinensis var. subglabra and its structure was identified as 1S, 2R, 3S, 6R-1-benzoyloxymethylene-1,2- dihydroxy-3-benzoyloxy-6-chlorocyclohex-4-ene (1), by spectral evidences.展开更多
Oxygenation constants and thermodynamic parameters DeltaH degrees and DeltaS degrees of cobalt (II) complexes with bis-(furaldehyde) Schiff bases (1, 2, 3, 4)were obtained by mearsuring saturated dioxygen uptake of th...Oxygenation constants and thermodynamic parameters DeltaH degrees and DeltaS degrees of cobalt (II) complexes with bis-(furaldehyde) Schiff bases (1, 2, 3, 4)were obtained by mearsuring saturated dioxygen uptake of these complexes in pyridine at different temperature. These complexes could activate molecular oxygen and were used as catalysts in cyclohexene oxidation. The influence of ligand structure on the dioxygen affinity and catalytic activity of the complexes were discussed.展开更多
The monometallic Ru catalysts with the CeO2 without calcination and ZnSO4 as co-modifiers gave a cyclohexene yield of 58.5% at the optimum nominal CeO2/Ru molar ratio of 0.15. Moreover, this catalyst had a good stabil...The monometallic Ru catalysts with the CeO2 without calcination and ZnSO4 as co-modifiers gave a cyclohexene yield of 58.5% at the optimum nominal CeO2/Ru molar ratio of 0.15. Moreover, this catalyst had a good stability. The chemisorbed （Zn（OH）2）3（ZnSOa）（H20）3 salt on Ru surface, which was formed by the CeO2 reacting with ZnSO4, created the new Ru active sites suitable for the formation of cyclohexene and improved the selectivity to cyclohexene. In addition, the Zn2＋ in the aqueous phase could form a stable complex with cyclohexene, stabilizing the cyclohexene in the liquid phase and improving the selectivity to cyclo- hexene. The calcination treatment of CeO2 was not beneficial for the enhancement of the selectivity to cyclohexene since it is difficult for the CeO2 calcinated to react with ZnSO4 to form the （Zn（OH）2）3（ZnSO4）（H20）3 salt.展开更多
Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO）...Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO） and cyclohexene oxide （CHO）. The conversion of epoxides dramatically increased up to 89.7% （yield： 384.2 g of polymer per g of Zn） with increasing reaction temperature from 60℃ to 80℃. The optimized reaction temperature is 80℃. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content （mol%） is lower than 10%, the PPCHC terpolymers have number average molecular weight （Ma） ranging from 102 × 10^3 to 202 × 10^3 and molecular weight distribution （MWD） values ranging from 2.8 to 3.5. In contrast to poly（propylene carbonate） （PPC）, the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0℃ to 42.6℃. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.展开更多
Cerium incorporated KIT-6 mesoporous materials were synthesized through direct hydrothermal method and characterized by using X-ray diffraction （XRD）, nitrogen sorption isotherm （BET）, Fourier transform infrared s...Cerium incorporated KIT-6 mesoporous materials were synthesized through direct hydrothermal method and characterized by using X-ray diffraction （XRD）, nitrogen sorption isotherm （BET）, Fourier transform infrared spectroscopy （FT-IR）, inductively coupled plasma - atomic emission spectroscopy （ICP-AES）, diffuse reflectance ultraviolet visible spectroscopy （DRS-UV-Vis）, ther- mogravimetric analysis （TGA）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） methods. It ap- peared that stable cerium ions were inserted into the silica framework of KIT-6, thus generating acid properties in their host materials. The catalytic activity of Ce-KIT-6 materials was evaluated in the vapor phase dehydration of cyclohexanol to cyclohexene and dicy- clohexyl ether at different temperatures with various Si/Ce molar ratios. Ce-KIT-6 （25） showed higher activity with 54% cyclohexa- nol conversion and 64% selectivity to cyclohexene. The catalytic results indicated that Ce-KIT-6 mesoporous materials could be used as versatile and stable acid catalysts.展开更多
Because of multiple potential reaction sites and variable oxidation depths,oxidation of cyclohexene can lead to a mixture of products with different oxidation states and functional groups,such as 7-oxabicyclo[4.1.0]he...Because of multiple potential reaction sites and variable oxidation depths,oxidation of cyclohexene can lead to a mixture of products with different oxidation states and functional groups,such as 7-oxabicyclo[4.1.0]heptane,trans/cis-cyclohexane-1,2-diol,cyclohex-2-en-1-ol,cyclohex-2-en-1-one,and even adipic acid.These products are broadly and abundantly used intermediates in the chemical industry;therefore,controllable oxidation reactions for cyclohexene that can selectively afford the targeted products are synthetically valuable for applications in both the academy and industry,thus becoming the aim of synthetic and catalytic chemists in the field.Many reports on selective oxidation of cyclohexene have recently appeared in the literature because of its significance.This short review summarizes the recent advances on this subject,and the contents are mainly classified based on the chosen oxidants.We hope that this review can provide a useful guide for controllable and selective catalytic oxidation of cyclohexene for interested readers from both the academy and industry.展开更多
基金This project was supposed by the National Natural Sciences Foundation of China(No.30472077)the Natural Sciences Foundation of Beijing City(No.7052049).
文摘Two new polyoxygenated cyclohexenes, kweichowenol A and B were isolated from the leaves of Uvaria kweichowensis and their structures were established on the basis of their spectral data.
文摘Two new polyoxygenated cyclohexenes,named uvacalolA(1),and B(2)were isolated from the rhizomes of Uvaria calamistrata.On the basis of spectral analysis and chemical derivatization,including preparation of Mosher esters,the structure of 1 to 2 were established.
基金financial support by the National Natural Science Foundation of China(22378339)Collaborative Innovation Center of New Chemical Technologies for Environmental Benignity and Efficient Resource Utilization.
文摘In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified with 4 mol·L^(-1) nitric acid was selected as an efficient catalyst for improving the hydration efficiency of cyclohexene.Furthermore,the microstructures and properties of fresh,used and regenerated acid-modified catalysts have been characterized by X-ray diffraction,scanning electron microscopy,nitrogen adsorption/desorption isotherm,Fourier transform infrared,thermal gravimetric analyzer,ammonia temperature programmed desorption and pyridine adsorbs Fourier transform infrared.The characterization results indicated that the total surface areas and pore volume of HZSM-5 zeolite increased after nitric acid treatment due to the formation of mesoporous structure.This benefits the diffusion rate of reactants and products,which improves the hydration efficiency and stability of the catalyst.Under the catalysis of HZSM-5,the conversion of cyclohexene was found to be 9.0%.However,treatment of HZSM-5 with nitric acid enhanced the conversion of cyclohexene to 12.2%,achieving a selectivity of 99.7%for cyclohexanol under optimal reaction conditions.This work affords a mild and efficient approach for improving the hydration efficiency and has potential industrial application value.
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.
基金supported by the National Natural Science Foundation of China(2123600121176056)+1 种基金the Programme for 100 Excellent Talents in Universities of Hebei Province(II)(BR2-208)the Natural Science Foundation of Hebei Province(B2015202228)
文摘A carbon solid acid catalyst was prepared by the sulfonation of partially carbonized peanut shell with concentrated H2SO4.The structure and acidity of the catalyst were characterized by Fourier transform infrared spectroscopy,scanning electron microscopy,X‐ray diffraction,thermogravimetric analysis,X‐ray photoelectron spectroscopy,and elemental analysis,which showed that it was an amorphous carbon material composed of aromatic carbon sheets in random orientations.Sulfonic acid groups were present on the surface at a density of 0.81 mmol/g.The carbon solid acid catalyst showed better performance than HZSM‐5 for the esterification of cyclohexene with formic acid.At a3:1 molar ratio of formic acid to cyclohexene,catalyst loading of 0.07 g/mL of cyclohexene,and reaction time of 1 h at 413 K,the cyclohexene conversion was 88.4%with 97.3%selectivity to cyclohexyl formate.The carbon solid acid catalyst showed better reusability than HZSM‐5 because its large pores were minimally affected by the accumulation of oligomerized cyclohexene,which deactivated HZSM‐5.The activity of the carbon solid acid catalyst decreased somewhat in the first two recycles due to the leaching of polycyclic aromatic hydrocarbon containing–SO3H groups and then it remained constant in the following reuse.
文摘Oxidation of cyclohexene under 1 atmospheric pressure of molecular oxygen at 70C in the absence of solvent catalyzed by PAMAM-SA-M (Where PAMAM = polyamidoamine; SA = salicyaldehyde; M = metal ions Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Zn2+, respectively) dendrimers, afforded 2-cyclohexen-1-ol 1, 2-cyclohexen-1-one 2, 7-oxabicyclo [4,1,0] heptane 3 and 7-oxabicyl [4,1,0] heptan-2-one 4 as the major products. The factors that affect this reaction are also discussed.
文摘A novel nanosized amorphous Ru-Fe-B/ZrO2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize and the amorphous character as well as to its textural character. In addition, the concentration of zinc ions, the content of ZrO2 in the slurry, and the pretreatment of the catalyst were found to be effective in improving the activity and the selectivity of the catalyst.
基金supported by the National Nature Science Foundation of China(21273205)the Innovation Found for Technology Based Firms of China(10C26214104505)+1 种基金the Chinese Post-doctorate Science Fund 51th batch of surface subsidizes(2012M511125)the Scientific Research Foundation of Graduate School of Zhengzhou University
文摘Ru-Ce catalysts were prepared by a co-precipitation method.The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO4.The Ce species in the catalysts prepared with different valences of the Ce precursors all exist as CeO2 on the Ru surface.The promoter CeO2alone could not improve the selectivity to cyclohexene of Ru catalysts.However,almost all the CeO2 in the catalysts could react with the reaction modifier ZnSO4 to form(Zn(OH)2)3(ZnSO4)(H2O)3 salt.The amount of the chemisorbed salt increased with the CeO2 loading,resulting in the decrease of the activity and the increase of the selectivity to cyclohexene of Ru catalyst.The Ru-Ce catalyst with the optimum Ce/Ru molar ratio of 0.19 gave a maximum cyclohexene yield of 57.4%.Moreover,this catalyst had good stability and excellent reusability.
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.
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sponsored by program for new century excellent talents in university(NoNCET-04-0268)"111"project
文摘Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant.The material is characterized with XRD,TEM,N_2 adsorption isotherm.The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20-30 nm.The BET surface area increases from 420 to 513 m^2/g compared to conventional TS-1 zeolite.The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.
文摘Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promoted with Zn or Mn alone. The optimum Mn/Zn molar ratio was determined to be 0.3. With the addition of 0.5 g NaOH, the Ru-Mn-Zn-0.3 catalyst, which was reduced at 150 ？ C, afforded a cyclohexene selectivity of 81.1% at a benzene conversion of 60.2% at 5 min and a maximum cyclohexene yield of 59.9% at 20 min. Based on characterizations, the excellent performance of Ru-Mn-Zn catalyst was ascribed to the suitable pore structure, the appropriate reducibility and the homogenous chemical environment of the catalyst.
基金This work was supported by the National Natural Science Foundation of China(21773068,21811530273,21573072)the National Key Research and Development Program of China(2017YFA0403102)Shanghai Leading Academic Discipline Project(B409).
文摘Acidic poly(ionic liquid)s(PILs)with swelling ability were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids,divinylbenzene(DVB)and sodium acrylate(NaAA),and further acidification by sulfuric acid.The swelling ability of acidic PILs was greatly affected by cross-linker content and chain length of 3-alkyl-substituents on imidazolium.Cross-linked network structures could be observed from the cryogenic scanning electron microscopy(cryo-SEM)images of the swollen acidic PILs in formic acid.Acidic PILs with network structures in swollen state exhibited excellent activities in the esterification of cyclohexene and formic acid,and the catalytic activities were in positive correlation with their swelling abilities.Acidic PIL with 3-octyl-substituent and 2.5 mol%DVB(PIL-C8-2.5DVB-HSO4)had the highest swelling ability in formic acid and exhibited comparable catalytic activities with homogeneous catalysts such as sulfuric acid and p-toluenesulfonic acid.
基金Supported by the Outstanding Personality Innovation Funds of Henan Province(No.0121001900).
文摘Molybdenum (VI) complex, namely molybdenum dioxobis(2,4-pentanedione) [MoO2(acac)2] used as epoxidation catalyst species, was synthesized and characterized by elemental analysis and infrared spectrum. Polystyrene-supported molybdenum dioxobis(2,4-pentanedione) [MoO2(acac)2] for synthesis of epoxycyclohexane was prepared by phase transfer catalysis method. Effects of various factors in synthesis of epoxycyclohexane by reaction of cyclohexene and t-BuOOH in the atmosphere of nitrogen catalyzed by polystyrene-supported MoO2(acac)2 were also investigated. Under the following conditions, n(cyclohexene):n(t-BuOOH)=3.5:l (based on 0.1 mol of t-BuOOH), volume of solvent -10ml, reaction temperature -80℃, reaction time -60min, and mass of molybdenum in the catalyst -2.30×0^(-3)g, the yield of epoxycyclohexane on the basis of t-BuOOH is over 99.5%, and the purity of epoxycyclohexane is about 99.9% by gas chromatogram(GC) analysis.
基金the National Natural Science Foundation of China(No.39970084)the Chinese Doctoral Grants of the Ministry of Science and Technology of China(No.96-901-96-54)for financial support
文摘A new compound, subglain B, was isolated from the stems of Uvaria tonkinensis var. subglabra and its structure was identified as 1S, 2R, 3S, 6R-1-benzoyloxymethylene-1,2- dihydroxy-3-benzoyloxy-6-chlorocyclohex-4-ene (1), by spectral evidences.
文摘Oxygenation constants and thermodynamic parameters DeltaH degrees and DeltaS degrees of cobalt (II) complexes with bis-(furaldehyde) Schiff bases (1, 2, 3, 4)were obtained by mearsuring saturated dioxygen uptake of these complexes in pyridine at different temperature. These complexes could activate molecular oxygen and were used as catalysts in cyclohexene oxidation. The influence of ligand structure on the dioxygen affinity and catalytic activity of the complexes were discussed.
基金Project supported by National Natural Science Foundation of China （21273205）, and the Innovation Fund for Technology Based Firms of China （10C26214104505）
文摘The monometallic Ru catalysts with the CeO2 without calcination and ZnSO4 as co-modifiers gave a cyclohexene yield of 58.5% at the optimum nominal CeO2/Ru molar ratio of 0.15. Moreover, this catalyst had a good stability. The chemisorbed （Zn（OH）2）3（ZnSOa）（H20）3 salt on Ru surface, which was formed by the CeO2 reacting with ZnSO4, created the new Ru active sites suitable for the formation of cyclohexene and improved the selectivity to cyclohexene. In addition, the Zn2＋ in the aqueous phase could form a stable complex with cyclohexene, stabilizing the cyclohexene in the liquid phase and improving the selectivity to cyclo- hexene. The calcination treatment of CeO2 was not beneficial for the enhancement of the selectivity to cyclohexene since it is difficult for the CeO2 calcinated to react with ZnSO4 to form the （Zn（OH）2）3（ZnSO4）（H20）3 salt.
基金financially supported by the China High-Tech Development 863 Key Program(No.2010AA0349)Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2010)+1 种基金Guangdong Province Sci.&Tech.Bureau(Key Strategic Project Grant No.2008A080800024)Guangdong Education Bureau(Key Project) and Chinese Universities Basic Research Founding
文摘Using supported multi-componem zinc dicarboxylate catalyst, poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate） （PPCHC） was successfully synthesized from carbon dioxide （CO2） with propylene oxide （PO） and cyclohexene oxide （CHO）. The conversion of epoxides dramatically increased up to 89.7% （yield： 384.2 g of polymer per g of Zn） with increasing reaction temperature from 60℃ to 80℃. The optimized reaction temperature is 80℃. The chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content （mol%） is lower than 10%, the PPCHC terpolymers have number average molecular weight （Ma） ranging from 102 × 10^3 to 202 × 10^3 and molecular weight distribution （MWD） values ranging from 2.8 to 3.5. In contrast to poly（propylene carbonate） （PPC）, the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0℃ to 42.6℃. Similarly, the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO. These improvements in mechanical and thermal properties are of importance for the practical application of PPC.
文摘Cerium incorporated KIT-6 mesoporous materials were synthesized through direct hydrothermal method and characterized by using X-ray diffraction （XRD）, nitrogen sorption isotherm （BET）, Fourier transform infrared spectroscopy （FT-IR）, inductively coupled plasma - atomic emission spectroscopy （ICP-AES）, diffuse reflectance ultraviolet visible spectroscopy （DRS-UV-Vis）, ther- mogravimetric analysis （TGA）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） methods. It ap- peared that stable cerium ions were inserted into the silica framework of KIT-6, thus generating acid properties in their host materials. The catalytic activity of Ce-KIT-6 materials was evaluated in the vapor phase dehydration of cyclohexanol to cyclohexene and dicy- clohexyl ether at different temperatures with various Si/Ce molar ratios. Ce-KIT-6 （25） showed higher activity with 54% cyclohexa- nol conversion and 64% selectivity to cyclohexene. The catalytic results indicated that Ce-KIT-6 mesoporous materials could be used as versatile and stable acid catalysts.
文摘Because of multiple potential reaction sites and variable oxidation depths,oxidation of cyclohexene can lead to a mixture of products with different oxidation states and functional groups,such as 7-oxabicyclo[4.1.0]heptane,trans/cis-cyclohexane-1,2-diol,cyclohex-2-en-1-ol,cyclohex-2-en-1-one,and even adipic acid.These products are broadly and abundantly used intermediates in the chemical industry;therefore,controllable oxidation reactions for cyclohexene that can selectively afford the targeted products are synthetically valuable for applications in both the academy and industry,thus becoming the aim of synthetic and catalytic chemists in the field.Many reports on selective oxidation of cyclohexene have recently appeared in the literature because of its significance.This short review summarizes the recent advances on this subject,and the contents are mainly classified based on the chosen oxidants.We hope that this review can provide a useful guide for controllable and selective catalytic oxidation of cyclohexene for interested readers from both the academy and industry.
