Silicalite-1 membranes supported on macroporous Al2O3 tubes were prepared by in-situ crystallization and secondary growth method under microwave-assisted closed system. The influences of crystallization time and tempe...Silicalite-1 membranes supported on macroporous Al2O3 tubes were prepared by in-situ crystallization and secondary growth method under microwave-assisted closed system. The influences of crystallization time and temperature on properties of the as-prepared membranes were investigated. Results show that by in-situ crystallization at different temperatures it's hardly to obtain uniform membranes on the poor supports, while by secondary growth method dense and well-intergrown silicalite-1 membranes with thickness of 2 μm on seeded supports can be obtained even at 393 K for 60 min. At 423 K, 30 min was enough to synthesize well-intergrown and uniform zeolite membrane under microwave heating. These silicalite-1 membranes also exhibit well hydrogen permeation performance. The effect of temperature was more remarkable than that of time evaluated from the morphology difference of these membranes.展开更多
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 growth and orientation of zeolite crystals on a glass substrate was investigated by changing the roughness and setting of the substrate surface.The orientation control of crystals on the glass substrate was achiev...The growth and orientation of zeolite crystals on a glass substrate was investigated by changing the roughness and setting of the substrate surface.The orientation control of crystals on the glass substrate was achieved.It was found that the setting and treatment of the glass substrate had a substantial effect on crystal orientation.When the substrate surface was upward, the preferential growth of crystal was along the a-axis.However, the preferential growth of crystal was along b-axis when the substrate surface was downward.According to experimental results, a film formation mechanism was proposed to account for the growth and orientation of crystals on the glass substrate.展开更多
Synthesis of high performance Silicalite-1 zeolite membranes on silica tubes was first reported in this paper.After two-step in-situ hydrothermal synthesis,well intergrown Silicalite-1 zeolite membranes were synthesiz...Synthesis of high performance Silicalite-1 zeolite membranes on silica tubes was first reported in this paper.After two-step in-situ hydrothermal synthesis,well intergrown Silicalite-1 zeolite membranes were synthesized on silica tubes after aging at 75 ℃ for 12 h.The Silicalite-1 zeolite membranes were characterized by SEM.The separation performance towards ethanol/water mixtures was evaluated by pervaporation.With temperature increasing,the flux of S-1 membrane,increased from 0.2 kg·m-2·h-1 at 30 ℃ to ca. 1.0 kg·m-2·h-1 at 80 ℃, while the separation factor decreased from 110 to 89.These results showed that silica supports may be more suitable for preparing high performance Silicalite-1 membranes.展开更多
A silicalite 1 zeolite membrane was in situ crystallized from a layer of silica species prepared by a novel method of low temperature chemical vapor deposition (LTCVD) on a porous cordierite substrate. XRD patterns sh...A silicalite 1 zeolite membrane was in situ crystallized from a layer of silica species prepared by a novel method of low temperature chemical vapor deposition (LTCVD) on a porous cordierite substrate. XRD patterns show that the membrane consists of MFI type zeolite crystals. The investigation with SEM indicats that the membrane is about 50 μm thick, and covered with well intergrowth MFI zeolite crystals of about 10 μm in size. The EDX analysis confirms that the membrane is composed of silica in the absence of Al, indicating high silica MFI(Silicalite 1) zeolite grown on the support. The ratio of pure gas permeation is 296 for H 2/ iso butane and 13.7 for n / iso butane at room temperature respectively, confirming that the membrane synthesized on the support of cordierite is high quality without pinhole.展开更多
Hydrophilic acid-resistant Ge-ZSM-5 membranes were synthesized via secondary growth method on porous a-A1203 substrates with Silicalite-1 zeolite as seeds. The membranes were characterized by means of scanning electro...Hydrophilic acid-resistant Ge-ZSM-5 membranes were synthesized via secondary growth method on porous a-A1203 substrates with Silicalite-1 zeolite as seeds. The membranes were characterized by means of scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectrometer to look into the microstructures and element contents of the membranes. The separation performance of the membranes was investigated for separating water from acetic acid solution by pervaporation. The results show that membranes fabricated by the conventional secondary growth method have a high flux, but the selectivity of them is rather limited. Preheating the secondary synthesis sol and using the supernatant as the secondary synthesis sol for membrane fabrication were found to be ef- fective to lower the concentration of the nutrient to constrain re-nucleation, at the same time, lower the A1 content in the membranes. The membrane obtained exhibited improved separation performance with a separation factor of 83 at a flux of 0.67 kg.rn-2.h-1 at 353 K for a feed concentration of 98% acetic acid solution.展开更多
Silicalite 1/ceramic composite membrane was prepared on the outer surface of the α Al 2O 3 tubular support by in situ hydrothermal synthesis. The membrane was characterized by X ray diffraction (XRD) and scanning ele...Silicalite 1/ceramic composite membrane was prepared on the outer surface of the α Al 2O 3 tubular support by in situ hydrothermal synthesis. The membrane was characterized by X ray diffraction (XRD) and scanning electron microscope (SEM). The pure gas permeances of H 2, N 2, Ar, CH 4, C 2H 4, C 2H 6, C 3H 8, n C 4H 10 and i C 4H 10 were measured as a function of the pressure difference at 298 and 473 K. The permeances of H 2, N 2 and Ar showed little dependence on the pressure differences; the permselectivities of H 2/ i C 4H 10 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: CH 4>C 2H 6>C 3H 8> n C 4H 10 > i C 4H 10 . The permselectivity of n C 4H 10 / i C 4H 10 was above 15 at 298 K. As the temperature increased, the permeances of all gases increased except those of N 2 and Ar, and a significant increment was found for alkanes. The permselectivity of n C 4H 10 / i C 4H 10 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
基金supported by the National Natural Science Foundation of China (NSFC Grant No: 21306213)
文摘Silicalite-1 membranes supported on macroporous Al2O3 tubes were prepared by in-situ crystallization and secondary growth method under microwave-assisted closed system. The influences of crystallization time and temperature on properties of the as-prepared membranes were investigated. Results show that by in-situ crystallization at different temperatures it's hardly to obtain uniform membranes on the poor supports, while by secondary growth method dense and well-intergrown silicalite-1 membranes with thickness of 2 μm on seeded supports can be obtained even at 393 K for 60 min. At 423 K, 30 min was enough to synthesize well-intergrown and uniform zeolite membrane under microwave heating. These silicalite-1 membranes also exhibit well hydrogen permeation performance. The effect of temperature was more remarkable than that of time evaluated from the morphology difference of these membranes.
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.
文摘The growth and orientation of zeolite crystals on a glass substrate was investigated by changing the roughness and setting of the substrate surface.The orientation control of crystals on the glass substrate was achieved.It was found that the setting and treatment of the glass substrate had a substantial effect on crystal orientation.When the substrate surface was upward, the preferential growth of crystal was along the a-axis.However, the preferential growth of crystal was along b-axis when the substrate surface was downward.According to experimental results, a film formation mechanism was proposed to account for the growth and orientation of crystals on the glass substrate.
文摘Synthesis of high performance Silicalite-1 zeolite membranes on silica tubes was first reported in this paper.After two-step in-situ hydrothermal synthesis,well intergrown Silicalite-1 zeolite membranes were synthesized on silica tubes after aging at 75 ℃ for 12 h.The Silicalite-1 zeolite membranes were characterized by SEM.The separation performance towards ethanol/water mixtures was evaluated by pervaporation.With temperature increasing,the flux of S-1 membrane,increased from 0.2 kg·m-2·h-1 at 30 ℃ to ca. 1.0 kg·m-2·h-1 at 80 ℃, while the separation factor decreased from 110 to 89.These results showed that silica supports may be more suitable for preparing high performance Silicalite-1 membranes.
文摘A silicalite 1 zeolite membrane was in situ crystallized from a layer of silica species prepared by a novel method of low temperature chemical vapor deposition (LTCVD) on a porous cordierite substrate. XRD patterns show that the membrane consists of MFI type zeolite crystals. The investigation with SEM indicats that the membrane is about 50 μm thick, and covered with well intergrowth MFI zeolite crystals of about 10 μm in size. The EDX analysis confirms that the membrane is composed of silica in the absence of Al, indicating high silica MFI(Silicalite 1) zeolite grown on the support. The ratio of pure gas permeation is 296 for H 2/ iso butane and 13.7 for n / iso butane at room temperature respectively, confirming that the membrane synthesized on the support of cordierite is high quality without pinhole.
基金Supported by the National Natural Science Foundation of China（No.21201130） and the Foundation of the State Key Labora- tory of Coal Conversion, China（No.J14-15-603）.
文摘Hydrophilic acid-resistant Ge-ZSM-5 membranes were synthesized via secondary growth method on porous a-A1203 substrates with Silicalite-1 zeolite as seeds. The membranes were characterized by means of scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectrometer to look into the microstructures and element contents of the membranes. The separation performance of the membranes was investigated for separating water from acetic acid solution by pervaporation. The results show that membranes fabricated by the conventional secondary growth method have a high flux, but the selectivity of them is rather limited. Preheating the secondary synthesis sol and using the supernatant as the secondary synthesis sol for membrane fabrication were found to be ef- fective to lower the concentration of the nutrient to constrain re-nucleation, at the same time, lower the A1 content in the membranes. The membrane obtained exhibited improved separation performance with a separation factor of 83 at a flux of 0.67 kg.rn-2.h-1 at 353 K for a feed concentration of 98% acetic acid solution.
文摘Silicalite 1/ceramic composite membrane was prepared on the outer surface of the α Al 2O 3 tubular support by in situ hydrothermal synthesis. The membrane was characterized by X ray diffraction (XRD) and scanning electron microscope (SEM). The pure gas permeances of H 2, N 2, Ar, CH 4, C 2H 4, C 2H 6, C 3H 8, n C 4H 10 and i C 4H 10 were measured as a function of the pressure difference at 298 and 473 K. The permeances of H 2, N 2 and Ar showed little dependence on the pressure differences; the permselectivities of H 2/ i C 4H 10 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: CH 4>C 2H 6>C 3H 8> n C 4H 10 > i C 4H 10 . The permselectivity of n C 4H 10 / i C 4H 10 was above 15 at 298 K. As the temperature increased, the permeances of all gases increased except those of N 2 and Ar, and a significant increment was found for alkanes. The permselectivity of n C 4H 10 / i C 4H 10 decreased to about 9 at 473 K. The gas permeation results showed that the silicalite 1/ceramic composite membrane was defect free.
