In order to investigate the rules on preparation of titanium silicalite （TS-1） the ^1H →^13C CP/ MAS NMR spectrometers were applied to track the function of template TPAOH in the process of crystallization of titan...In order to investigate the rules on preparation of titanium silicalite （TS-1） the ^1H →^13C CP/ MAS NMR spectrometers were applied to track the function of template TPAOH in the process of crystallization of titanium silicalite. The research results revealed that at the initial stage of crystallization the TPA＋ ions acting as the template could predominantly absorb the polymers of negatively charged silicatitania sol and the interactions between silica sol and titania sol could gradually lead to the formation of tiny crystal nuclei that could slowly grow up to form molecular sieves. Upon investigating the course of crystallization of titanium silicalite the ^1H →^13C CP/MAS NMR spectrometers were applied to effectively enhance the resolution of 29Si signals in the titanium silicalite. Study results have shown that during the formation of tiny crystal nuclei upon interaction between titania sol and silica sol the influence of titania sol on the silica sol was insignificant. However, when tiny crystal nuclei broke out into molecular sieves the titania sol could enter the zeolite framework that could apparently impose an enhanced effect on the silica sol.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
A simple, quick, sensitive, accurate and precise method has been developed for evaluating the catalytic active sites of titanium silicalite-1 (TS-1). The catalytic active sites of titanium silicalite zeolite depend on...A simple, quick, sensitive, accurate and precise method has been developed for evaluating the catalytic active sites of titanium silicalite-1 (TS-1). The catalytic active sites of titanium silicalite zeolite depend on the effectively active species (EAS) in TS-1 which react with specific substrates quickly. However, the EAS was hard to be evaluated with conventional instruments and techniques in the past. In this paper, the EAS was formed in TS-1 upon interaction with H2O2, and its presence could be confirmed by UV-vis spectroscopy which has an absorption peak at 385 nm. The absorbance at 385 nm was found to be linearly related to time, and when the absorbance and the increasing rate of absorbance (k) increased, the catalytic performance of TS-1 enhanced.展开更多
THE Dajiangping pyrite ore deposit located in the Yunfu County of Guangdong Province is asuper-large pyrite ore deposit. Its age has not been defined so far because of the absence of fos-sil. This note is to use Rb-Sr...THE Dajiangping pyrite ore deposit located in the Yunfu County of Guangdong Province is asuper-large pyrite ore deposit. Its age has not been defined so far because of the absence of fos-sil. This note is to use Rb-Sr isotope dating of silicalite to constrain the age of the ore depositand place special emphasis on its geological significance.展开更多
Two kinds of radiolarian silicalites at the bottom and top of the ophiolite in the Mount (Mt.) Ailao belt, Yunnan Province, are dealt with in this work in terms of geology, micro-paleontology, isotope and REE. The fir...Two kinds of radiolarian silicalites at the bottom and top of the ophiolite in the Mount (Mt.) Ailao belt, Yunnan Province, are dealt with in this work in terms of geology, micro-paleontology, isotope and REE. The first kind of silicalite was defined as the turbidite formation. In this category, the radiolarian species lived in the Late Devonian (D3). The corresponding ecologic assemblage, composed of δ30Si (0.4‰-0.5‰, average 0.03‰), δCe (0.77-0.97, average 0.85) and LaN/YbN (0.77-1.06, average 0.96) of silicalite, shows that it occurred in the abyssal environment. The second kind of silicalite was defined as the mud-siliceous formation. Contacting conformably with the basalt of the ophiolite suit, the radiolarian silicalite at the top of ophiolite was in the category of the component units of the ophiolite in the Mt. Ailao belt. In this category, the radiolarian species lived in the Early Carboniferous (C1). The corresponding ecologic assemblage, composed of δ30Si (0.2‰-1.3‰averaging 0.7‰), ?展开更多
Silicalite-1/ceramic composite membrane was prepared on the outer surface of the α-Al2O3 tubular support byin-situ hydrothermal synthesis. The membrane was characterized by X-ray diffraction (XRD) and scanning electr...Silicalite-1/ceramic composite membrane was prepared on the outer surface of the α-Al2O3 tubular support byin-situ hydrothermal synthesis. The membrane was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The pure gas permeances of H2, N2, Ar, CH4, C2H4, C2H6, C3H8, n-C4H10 and i-C4H10 were measured as a function of the pressure difference at 298 and 473 K. The permeances of H2, N2 and Ar showed little dependence on the pressure differences; the permselectivities of H2/i-C4H10 were 249 and 36.2 at 298 and 473 K respectively, which is a characteristic of molecular transport in silicalite-1 channels. The permeances of light alkanes decreased in the following order: CH4】C2H6】C3H8】n-C4H10】i-C4H10. The permselectivity of n-C4H10/i-C4H10 was above 15 at 298 K. As the temperature increased, the permeances of all gases increased except those of N2 and Ar, and a significant increment was found for alkanes. The permselectivity ofn-C4H10/i-C4H10 decreased to about 9 at 473 K. The gas permeation results showed that the silicalite-1/ceramic composite membrane was defect-free.展开更多
Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this ...Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this system, TPA+ cations (come from TPABr or TPAOH) served as templating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, IR spectroscopies, SEM, 29Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.展开更多
Au-Ag bimetallic nanoparticle‐supported microporous titanium silicalite‐1catalysts were prepared via a hydrothermal‐immersion method,and their structures were examined.These materials serve as efficient catalysts f...Au-Ag bimetallic nanoparticle‐supported microporous titanium silicalite‐1catalysts were prepared via a hydrothermal‐immersion method,and their structures were examined.These materials serve as efficient catalysts for the photosynthesis of propylene oxide via the epoxidation of propene.The Au/Ag mass ratio and reaction temperature were demonstrated to have significant effects on the catalytic activity and selectivity of propylene oxide.The optimal formation rate(68.3μmol/g·h)and selectivity(52.3%)toward propylene oxide were achieved with an Au:Ag mass ratio of4:1.Notably,the strong synergistic effect between Au and Ag resulted in superior photocatalysis of the bimetallic systems compared with those of the individual systems.A probable reaction mechanism was proposed based on the theoretical and experimental results.展开更多
An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst lo...An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading, and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.展开更多
The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A ...The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.展开更多
文摘In order to investigate the rules on preparation of titanium silicalite （TS-1） the ^1H →^13C CP/ MAS NMR spectrometers were applied to track the function of template TPAOH in the process of crystallization of titanium silicalite. The research results revealed that at the initial stage of crystallization the TPA＋ ions acting as the template could predominantly absorb the polymers of negatively charged silicatitania sol and the interactions between silica sol and titania sol could gradually lead to the formation of tiny crystal nuclei that could slowly grow up to form molecular sieves. Upon investigating the course of crystallization of titanium silicalite the ^1H →^13C CP/MAS NMR spectrometers were applied to effectively enhance the resolution of 29Si signals in the titanium silicalite. Study results have shown that during the formation of tiny crystal nuclei upon interaction between titania sol and silica sol the influence of titania sol on the silica sol was insignificant. However, when tiny crystal nuclei broke out into molecular sieves the titania sol could enter the zeolite framework that could apparently impose an enhanced effect on the silica sol.
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.
文摘A simple, quick, sensitive, accurate and precise method has been developed for evaluating the catalytic active sites of titanium silicalite-1 (TS-1). The catalytic active sites of titanium silicalite zeolite depend on the effectively active species (EAS) in TS-1 which react with specific substrates quickly. However, the EAS was hard to be evaluated with conventional instruments and techniques in the past. In this paper, the EAS was formed in TS-1 upon interaction with H2O2, and its presence could be confirmed by UV-vis spectroscopy which has an absorption peak at 385 nm. The absorbance at 385 nm was found to be linearly related to time, and when the absorbance and the increasing rate of absorbance (k) increased, the catalytic performance of TS-1 enhanced.
文摘THE Dajiangping pyrite ore deposit located in the Yunfu County of Guangdong Province is asuper-large pyrite ore deposit. Its age has not been defined so far because of the absence of fos-sil. This note is to use Rb-Sr isotope dating of silicalite to constrain the age of the ore depositand place special emphasis on its geological significance.
文摘Two kinds of radiolarian silicalites at the bottom and top of the ophiolite in the Mount (Mt.) Ailao belt, Yunnan Province, are dealt with in this work in terms of geology, micro-paleontology, isotope and REE. The first kind of silicalite was defined as the turbidite formation. In this category, the radiolarian species lived in the Late Devonian (D3). The corresponding ecologic assemblage, composed of δ30Si (0.4‰-0.5‰, average 0.03‰), δCe (0.77-0.97, average 0.85) and LaN/YbN (0.77-1.06, average 0.96) of silicalite, shows that it occurred in the abyssal environment. The second kind of silicalite was defined as the mud-siliceous formation. Contacting conformably with the basalt of the ophiolite suit, the radiolarian silicalite at the top of ophiolite was in the category of the component units of the ophiolite in the Mt. Ailao belt. In this category, the radiolarian species lived in the Early Carboniferous (C1). The corresponding ecologic assemblage, composed of δ30Si (0.2‰-1.3‰averaging 0.7‰), ?
文摘Silicalite-1/ceramic composite membrane was prepared on the outer surface of the α-Al2O3 tubular support byin-situ hydrothermal synthesis. The membrane was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The pure gas permeances of H2, N2, Ar, CH4, C2H4, C2H6, C3H8, n-C4H10 and i-C4H10 were measured as a function of the pressure difference at 298 and 473 K. The permeances of H2, N2 and Ar showed little dependence on the pressure differences; the permselectivities of H2/i-C4H10 were 249 and 36.2 at 298 and 473 K respectively, which is a characteristic of molecular transport in silicalite-1 channels. The permeances of light alkanes decreased in the following order: CH4】C2H6】C3H8】n-C4H10】i-C4H10. The permselectivity of n-C4H10/i-C4H10 was above 15 at 298 K. As the temperature increased, the permeances of all gases increased except those of N2 and Ar, and a significant increment was found for alkanes. The permselectivity ofn-C4H10/i-C4H10 decreased to about 9 at 473 K. The gas permeation results showed that the silicalite-1/ceramic composite membrane was defect-free.
基金Project (No. 29792070) supported by the National Natural Science Foundation of China.Present address: Department of Chemical Engineering,Xiangtan University, Xiangtan, Hunan 411105, China.
文摘Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this system, TPA+ cations (come from TPABr or TPAOH) served as templating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, IR spectroscopies, SEM, 29Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.
基金supported by the National Natural Science Foundation of China(21576050)the Natural Science Foundation of Jiangsu Province(BK20150604)~~
文摘Au-Ag bimetallic nanoparticle‐supported microporous titanium silicalite‐1catalysts were prepared via a hydrothermal‐immersion method,and their structures were examined.These materials serve as efficient catalysts for the photosynthesis of propylene oxide via the epoxidation of propene.The Au/Ag mass ratio and reaction temperature were demonstrated to have significant effects on the catalytic activity and selectivity of propylene oxide.The optimal formation rate(68.3μmol/g·h)and selectivity(52.3%)toward propylene oxide were achieved with an Au:Ag mass ratio of4:1.Notably,the strong synergistic effect between Au and Ag resulted in superior photocatalysis of the bimetallic systems compared with those of the individual systems.A probable reaction mechanism was proposed based on the theoretical and experimental results.
文摘An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading, and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.
基金The author thanks for the financial support of SINOPEC Corporation(S413108).
文摘The toluene oxidative bromination reaction catalyzed by hollow titanium silicalite(HTS)zeolite in aqueous medium was investigated by employing H2O2 and HBr under mild conditions without the need for organic solvent.A high toluene conversion(90.7%)and high selectivity of mono-bromotoluene(99.0%)was achieved under the optimal reaction conditions.The UV-Raman spectroscopy was applied for the mechanism study and the result reveals that HTS is efficient for catalyzing the oxidation reaction of HBr with H2O2 to produce abundant active bromine species,which can further facilitate the toluene electrophilic bromination reaction.A two-step toluene bromination reaction mechanism involving the HTS catalyzed active bromine species“generation-conversion-utilization”process is proposed based on the UV-Raman spectroscopy analysis.
