Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Le...Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.展开更多
The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product...The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product was studied,which include reaction temperature,reaction time,molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde.The influence of the amount of catalyst on the reaction results was also investigated.The maximum 5-isooctyl salicylaldoxime yield of 98.76%was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6,the reaction temperature of 70℃,the amount of TS-1 of 17.5 g·mol^(-1)(5-isooctyl salicylaldehyde),and the feeding time of 2 h.This method has the mild reaction conditions and avoids the shortcomings of traditional methods.Moreover,useless inorganic salts by-products are avoided,and there is no environmental pollution.展开更多
In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the pr...In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the process of crystallization of titanium silicalite zeolite. The research results revealed that at the initial stage of crystallization the interactions between silica gel and titania gel in the polymer blend could gradually lead to the formation of tiny crystal nuclei with complicated structure that could slowly grow up to form molecular sieves. Quite different from the conventional zeolites that use the acid sites as the catalytically active centers, the oxidative reactivity of the titanium silicalite zeolite was not proportional to its crystallinity and is associated with the oxidative centers of titanium contained in the zeolite.展开更多
The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introduc...The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introducing urea into zeolite synthesis is a simple and convenient method to modify these properties of titanosilicate zeolite.Uncalcined pore-blocked titanium silicalite-1(TS-1,i.e.,TS-1-B)with the lower urea dosage possesses more defective structure and unsaturated coordinated Ti sites verified by 29Si nuclear magnetic resonance(NMR)and X-ray photoelectron spectroscopy(XPS)analysis,which results in a high initial activity and hydrogen efficiency;while the high surface acidity generated by these Ti species leads to a continuous decrease in the activity and the propylene oxide(PO)selectivity during the reaction.As the amount of urea gradually increases,the TS-1-B samples present the reduced surface defects and defective and unsaturated Ti species.Specially,TS-1-B-0.30U presents the weaker PO adsorption on PO-diffusion reflectance infrared Fourier transform spectra(DRIFTS),thus results in the high stable PO formation rate and selectivity over its Au catalyst.Furthermore,a flat-plate-like shape with a shorter thickness of 100 nm along the b-axis direction is observed on the urea-modified TS-1.Compared with the conventional ellipsoidal TS-1 with crystal sizes of 200 and 500 nm,the flat-plate-like TS-1-0.30U displays the less surface defects,unsaturated Ti species,the weaker Lewis acid,which is favorable for the desorption and intracrystalline diffusion of PO,thus reduces the occurrence of side reactions for the improved selectivity and stability.This work may provide a reference for developing titanium-containing materials with high activity and stability over HOPO reaction.展开更多
Hierarchical silicalite-1 zeolites were obtained from the direct conversion of a mixture of ground solid raw materials via a steam-assisted crystallization（SAC） method without involvement of any mesoscale template. ...Hierarchical silicalite-1 zeolites were obtained from the direct conversion of a mixture of ground solid raw materials via a steam-assisted crystallization（SAC） method without involvement of any mesoscale template. Only a trace amount of water was necessary during the crystallization, implying that the amount of water can be dramatically reduced, which still offers easy separation and high yields. The simple procedure involved only grinding and heating, which not only saves resources and energy, but also significantly reduces the discharge of eco-friendly synthesis of zeolites for practical applications. Compared to conventional bulk silicalite-1, the nanosized hierarchical zeolites with MFI structure show enhanced removal capabilities for methylene blue owing to their hierarchical porosity.展开更多
E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly...E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly alternative be developed. The approach that involves preparing p -benzoquinone by the catalytic oxidation of benzene with hydrogen peroxide (H 2 O 2 ) over copper-modi ed titanium silicalite-1 (Cu/TS-1) has a certain superiority due to its green synthesis and mild reaction condi- tions. In this study, Cu/TS-1 catalyst was prepared by the wet impregnation of TS-1 with an aqueous solution of Cu(NO 3 ) 2 and then characterized by X-ray di raction, Fourier transform infrared spectroscopy, di use re ectance UV Vis spectros- copy, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray uorescence, and analysis of the N 2 adsorption desorption isotherms. The results reveal that Cu species exist mainly in the form of amorphous CuO that is well dispersed on the surface of catalysts, with no major change in the molecular sieve framework. After optimizing the reaction conditions, a desirable p -benzoquinone selectivity (88.4%) and benzene conversion (18.3%) were obtained when the doping of Cu in Cu/TS-1 is 1.95 wt%. In addition, Cu/TS-1 can be conveniently regenerated, showing a slight decrease in catalytic capability after initial use, which then stabilizes in subsequent circulations. The satisfactory stability and low cost of synthesizing Cu/TS-1 give this method considerable potential for further industrialization.展开更多
In this article, phenyl acetate was synthesized from phenol and acetic anhydride over titanium silicalite-1, in which the organic structure-directing agents were immobilized(TS-1-U). The reaction conditions were speci...In this article, phenyl acetate was synthesized from phenol and acetic anhydride over titanium silicalite-1, in which the organic structure-directing agents were immobilized(TS-1-U). The reaction conditions were specified at a phenol to acetic anhydride molar ratio of 1:1.2, a catalyst dosage of 6 m%, and a reaction temperature of 70 ℃. A total of 96.5% of phenol was converted to phenyl acetate without producing any byproducts after 2.5 h of reaction. Besides, although the catalyst deactivation is inevitable, TS-1-U could be recycled for at least four times.展开更多
基金financially supported by the National Natural Science Foundation of China (21603023)
文摘Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.
基金the National Natural Science Foundation of China(21376269)the Hunan Provincial Science and Technology Plan,China (2016TP1007)the independent exploration and innovation project for graduate students of Central South University(2020zzts403)
文摘The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product was studied,which include reaction temperature,reaction time,molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde.The influence of the amount of catalyst on the reaction results was also investigated.The maximum 5-isooctyl salicylaldoxime yield of 98.76%was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6,the reaction temperature of 70℃,the amount of TS-1 of 17.5 g·mol^(-1)(5-isooctyl salicylaldehyde),and the feeding time of 2 h.This method has the mild reaction conditions and avoids the shortcomings of traditional methods.Moreover,useless inorganic salts by-products are avoided,and there is no environmental pollution.
基金supported by the NationalScience Foundation of China(2006CB202508)wewould like to extend our heartfelt thanks to the RIPP’s labo-ratories engaging in XRD and FT-IR analyses for theirenergetical support and warm assistance provided to thisresearch work.
文摘In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the process of crystallization of titanium silicalite zeolite. The research results revealed that at the initial stage of crystallization the interactions between silica gel and titania gel in the polymer blend could gradually lead to the formation of tiny crystal nuclei with complicated structure that could slowly grow up to form molecular sieves. Quite different from the conventional zeolites that use the acid sites as the catalytically active centers, the oxidative reactivity of the titanium silicalite zeolite was not proportional to its crystallinity and is associated with the oxidative centers of titanium contained in the zeolite.
基金the funds from the Research Fund for National Key Research and Development Program of China(No.2021YFA1501403)the National Natural Science Foundation of China(Nos.21922803 and 22038003)+1 种基金Shanghai Rising-Star Program(No.17QA1401200)the Innovation Program of the Shanghai Municipal Education Commission(No.17ZR1407300).
文摘The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introducing urea into zeolite synthesis is a simple and convenient method to modify these properties of titanosilicate zeolite.Uncalcined pore-blocked titanium silicalite-1(TS-1,i.e.,TS-1-B)with the lower urea dosage possesses more defective structure and unsaturated coordinated Ti sites verified by 29Si nuclear magnetic resonance(NMR)and X-ray photoelectron spectroscopy(XPS)analysis,which results in a high initial activity and hydrogen efficiency;while the high surface acidity generated by these Ti species leads to a continuous decrease in the activity and the propylene oxide(PO)selectivity during the reaction.As the amount of urea gradually increases,the TS-1-B samples present the reduced surface defects and defective and unsaturated Ti species.Specially,TS-1-B-0.30U presents the weaker PO adsorption on PO-diffusion reflectance infrared Fourier transform spectra(DRIFTS),thus results in the high stable PO formation rate and selectivity over its Au catalyst.Furthermore,a flat-plate-like shape with a shorter thickness of 100 nm along the b-axis direction is observed on the urea-modified TS-1.Compared with the conventional ellipsoidal TS-1 with crystal sizes of 200 and 500 nm,the flat-plate-like TS-1-0.30U displays the less surface defects,unsaturated Ti species,the weaker Lewis acid,which is favorable for the desorption and intracrystalline diffusion of PO,thus reduces the occurrence of side reactions for the improved selectivity and stability.This work may provide a reference for developing titanium-containing materials with high activity and stability over HOPO reaction.
基金Supported by the National Natural Science Foundation of China（Nos.21390394, 21261130584, 91022030, 21771082）, the National Basic Research Program of China（Nos.2012CB821700, 2011CB808703）, the ＂111＂ Project of China（No.B07016）, the Award Project of King Abdullah University of Science ＆ Technology（No.CRG-1-2012-LAI-009）, the Science and Technology Development Center Project of the Ministry of Education of China（No.20120061130012） and the Science and Technology Research Program of the 13th Five Year Plan of China（No.20120061130012） and the Fund of Education Department of Jilin Province, China（No.2016405）.
文摘Hierarchical silicalite-1 zeolites were obtained from the direct conversion of a mixture of ground solid raw materials via a steam-assisted crystallization（SAC） method without involvement of any mesoscale template. Only a trace amount of water was necessary during the crystallization, implying that the amount of water can be dramatically reduced, which still offers easy separation and high yields. The simple procedure involved only grinding and heating, which not only saves resources and energy, but also significantly reduces the discharge of eco-friendly synthesis of zeolites for practical applications. Compared to conventional bulk silicalite-1, the nanosized hierarchical zeolites with MFI structure show enhanced removal capabilities for methylene blue owing to their hierarchical porosity.
基金supported by the National Natural Science Foundation of China (No. 21376163)
文摘E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly alternative be developed. The approach that involves preparing p -benzoquinone by the catalytic oxidation of benzene with hydrogen peroxide (H 2 O 2 ) over copper-modi ed titanium silicalite-1 (Cu/TS-1) has a certain superiority due to its green synthesis and mild reaction condi- tions. In this study, Cu/TS-1 catalyst was prepared by the wet impregnation of TS-1 with an aqueous solution of Cu(NO 3 ) 2 and then characterized by X-ray di raction, Fourier transform infrared spectroscopy, di use re ectance UV Vis spectros- copy, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray uorescence, and analysis of the N 2 adsorption desorption isotherms. The results reveal that Cu species exist mainly in the form of amorphous CuO that is well dispersed on the surface of catalysts, with no major change in the molecular sieve framework. After optimizing the reaction conditions, a desirable p -benzoquinone selectivity (88.4%) and benzene conversion (18.3%) were obtained when the doping of Cu in Cu/TS-1 is 1.95 wt%. In addition, Cu/TS-1 can be conveniently regenerated, showing a slight decrease in catalytic capability after initial use, which then stabilizes in subsequent circulations. The satisfactory stability and low cost of synthesizing Cu/TS-1 give this method considerable potential for further industrialization.
基金financially supported by the SINOPEC(Contact No.S413025)
文摘In this article, phenyl acetate was synthesized from phenol and acetic anhydride over titanium silicalite-1, in which the organic structure-directing agents were immobilized(TS-1-U). The reaction conditions were specified at a phenol to acetic anhydride molar ratio of 1:1.2, a catalyst dosage of 6 m%, and a reaction temperature of 70 ℃. A total of 96.5% of phenol was converted to phenyl acetate without producing any byproducts after 2.5 h of reaction. Besides, although the catalyst deactivation is inevitable, TS-1-U could be recycled for at least four times.
