In this work, ZSM-5 type chromosilicate samples as K[Cr]ZSM-5(KCS) and Na[Cr]ZSM-5(NCS) were prepared by hydrothermal method and their catalytic properties were investigated for the oxidative dehydrogenation of ethylb...In this work, ZSM-5 type chromosilicate samples as K[Cr]ZSM-5(KCS) and Na[Cr]ZSM-5(NCS) were prepared by hydrothermal method and their catalytic properties were investigated for the oxidative dehydrogenation of ethylbenzene in the presence of CO<sub>2</sub> as an oxidant using a fixed-bed stainless steel reactor. The prepared samples were characterized by their morphology (SEM), structural parameters (XRD), and textural parameters (BET). The performance of these catalysts was evaluated in terms of conversion, styrene yield, and selectivity. The KCS<sub>BW</sub> catalyst (potassium chromosilicate before washing with distilled water) afforded the highest styrene yield, 56.19%, with the selectivity of 96.05% in the presence of CO<sub>2</sub> because of the coexistence of potassium ion and Cr<sub>2</sub>O<sub>3</sub> in its structure and their synergistic effect. The influence of the presence of Cr<sub>2</sub>O<sub>3</sub> and sodium or potassium ion on the catalytic activity of the chromosilicate samples in the catalytic EB dehydrogenation process was discussed in detail. Moreover, according to the results, the catalytic activity of the chromosilicate samples (CS) in EB dehydrogenation was increased by decreasing the surface area.展开更多
The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,...The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.展开更多
Sulfur-containing monomers have received special interest from researchers because of their outstanding opticalperformance. Using the reaction between 2-phenylthioethyl-1-mercaptan and p-chloromethylstyrene, a new vin...Sulfur-containing monomers have received special interest from researchers because of their outstanding opticalperformance. Using the reaction between 2-phenylthioethyl-1-mercaptan and p-chloromethylstyrene, a new vinyl monomer4-(2-phenylthioethylthiomethyl)styrene (PTETMSt) was synthesized. Its structure was characterized by FT-IR and NMR.Copolymerization of styrene and PTETMSt was investigated. The data show that poly(styrene-co-PTETMSt) has higher refractive index, lower density and percentage of water absorption. The copolymer can be used on optical materials.展开更多
Well - defined diblock copolymers Of styrene (St ) and ethylene oxide (EO )have been prepared by sequential living anionic polymerization of the twocomonomers in THF. Diphenyl methyl potassium has been used as initiat...Well - defined diblock copolymers Of styrene (St ) and ethylene oxide (EO )have been prepared by sequential living anionic polymerization of the twocomonomers in THF. Diphenyl methyl potassium has been used as initiator. Theblock copolymers were characterized in detail by methods Of size exclusion chromatography (SEC ) , 1H - Nab, FT - IR, dynamic mechanical analysis(Daal ) and WAXD.展开更多
Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial applica...Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process.In this work,we report a facile hexamethylenetetramine nitrate(HN)-assisted thermal impregnation(HNTI)strategy for fabricating a novel nanodiamondbased monolithic foam(ND/CNT-SiC-ms-HN)catalyst through a two-step approach:One is to soak the carbon nanotube-modified Si C foam(CNT-SiC)with the slurry composed of HN,KCl,Li Cl,and dispersed ND,and the other is to heat the slurry-soaked CNT-SiC(ND-HN-KCl-Li Cl/CNT-SiC)in N_(2) atmosphere at750℃.The as-synthesized ND/CNT-SiC-ms-HN monolithic foam features the enriched surface kenotic C=O by promoted ND dispersion and O-doping,abundant stuctural defects,and improved nucleophilicity by N-doping,originating from the promoted ND dispersion by thermal impregnation(TI)in KCl-LiCl molten salt(MS)and the presence of HN in the annealing process.As a result,the ND/CNT-Si C-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate(5.49 mmol g^(-1)h^(-1))associated with 98.4%of styrene selectivity compared to the ND-based monolithic foam catalyst(ND/CNT-SiC).Moreover,the ND/CNT-Si C-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene.This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.展开更多
Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical ...Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.展开更多
The Cr2O3-SiO ? catalyst was prepared by a sol-gel method. It displays two times higher catalytic activity for the dehydrogenation of ethylbenzene in the presence of CO2 than the regular SiO2-supported chromia catalys...The Cr2O3-SiO ? catalyst was prepared by a sol-gel method. It displays two times higher catalytic activity for the dehydrogenation of ethylbenzene in the presence of CO2 than the regular SiO2-supported chromia catalyst.The higher amount of Cr 6+ present in the former catalyst accounts for its superior catalytic performance in the dehydrogenation reaction.展开更多
文摘In this work, ZSM-5 type chromosilicate samples as K[Cr]ZSM-5(KCS) and Na[Cr]ZSM-5(NCS) were prepared by hydrothermal method and their catalytic properties were investigated for the oxidative dehydrogenation of ethylbenzene in the presence of CO<sub>2</sub> as an oxidant using a fixed-bed stainless steel reactor. The prepared samples were characterized by their morphology (SEM), structural parameters (XRD), and textural parameters (BET). The performance of these catalysts was evaluated in terms of conversion, styrene yield, and selectivity. The KCS<sub>BW</sub> catalyst (potassium chromosilicate before washing with distilled water) afforded the highest styrene yield, 56.19%, with the selectivity of 96.05% in the presence of CO<sub>2</sub> because of the coexistence of potassium ion and Cr<sub>2</sub>O<sub>3</sub> in its structure and their synergistic effect. The influence of the presence of Cr<sub>2</sub>O<sub>3</sub> and sodium or potassium ion on the catalytic activity of the chromosilicate samples in the catalytic EB dehydrogenation process was discussed in detail. Moreover, according to the results, the catalytic activity of the chromosilicate samples (CS) in EB dehydrogenation was increased by decreasing the surface area.
基金supported by the Beijing Municipal Project for Developing Advanced Human Resources for Higher Education(Elastomers and Biomaterials).
文摘The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.
基金This work was supported by the Education Department of Hubei Province (2000Z24002).
文摘Sulfur-containing monomers have received special interest from researchers because of their outstanding opticalperformance. Using the reaction between 2-phenylthioethyl-1-mercaptan and p-chloromethylstyrene, a new vinyl monomer4-(2-phenylthioethylthiomethyl)styrene (PTETMSt) was synthesized. Its structure was characterized by FT-IR and NMR.Copolymerization of styrene and PTETMSt was investigated. The data show that poly(styrene-co-PTETMSt) has higher refractive index, lower density and percentage of water absorption. The copolymer can be used on optical materials.
文摘Well - defined diblock copolymers Of styrene (St ) and ethylene oxide (EO )have been prepared by sequential living anionic polymerization of the twocomonomers in THF. Diphenyl methyl potassium has been used as initiator. Theblock copolymers were characterized in detail by methods Of size exclusion chromatography (SEC ) , 1H - Nab, FT - IR, dynamic mechanical analysis(Daal ) and WAXD.
基金financially supported by the National Natural Science Foundation of China(No.21676046)the Chinese Ministry of Education via the Program for New Century Excellent Talents in Universities(No.NCET-12-0079)。
文摘Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process.In this work,we report a facile hexamethylenetetramine nitrate(HN)-assisted thermal impregnation(HNTI)strategy for fabricating a novel nanodiamondbased monolithic foam(ND/CNT-SiC-ms-HN)catalyst through a two-step approach:One is to soak the carbon nanotube-modified Si C foam(CNT-SiC)with the slurry composed of HN,KCl,Li Cl,and dispersed ND,and the other is to heat the slurry-soaked CNT-SiC(ND-HN-KCl-Li Cl/CNT-SiC)in N_(2) atmosphere at750℃.The as-synthesized ND/CNT-SiC-ms-HN monolithic foam features the enriched surface kenotic C=O by promoted ND dispersion and O-doping,abundant stuctural defects,and improved nucleophilicity by N-doping,originating from the promoted ND dispersion by thermal impregnation(TI)in KCl-LiCl molten salt(MS)and the presence of HN in the annealing process.As a result,the ND/CNT-Si C-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate(5.49 mmol g^(-1)h^(-1))associated with 98.4%of styrene selectivity compared to the ND-based monolithic foam catalyst(ND/CNT-SiC).Moreover,the ND/CNT-Si C-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene.This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.
基金The authors are grateful for the financial support of The Sate Key Fundamental Research Project and the Natural Science Foundation of China.
文摘Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.
文摘The Cr2O3-SiO ? catalyst was prepared by a sol-gel method. It displays two times higher catalytic activity for the dehydrogenation of ethylbenzene in the presence of CO2 than the regular SiO2-supported chromia catalyst.The higher amount of Cr 6+ present in the former catalyst accounts for its superior catalytic performance in the dehydrogenation reaction.
