N-doped carbons were fabricated from zeolite-templated carbon via modification with melamine and mild KOH activation. The N-doping treatment and KOH activation slightly lowered the surface areas of pristine zeolite-te...N-doped carbons were fabricated from zeolite-templated carbon via modification with melamine and mild KOH activation. The N-doping treatment and KOH activation slightly lowered the surface areas of pristine zeolite-templated carbon; nonetheless, N-doped carbons with a lower surface area exhibited much higher capacitance and cycling stability as fabricated into symmetric supercapacitor. Significantly, N-doped carbon obtained at 700°C showed a capacitance of 45.7 F/g at 0.1 A/g and 42.0 F/g at 10 A/g for the fabricated supercapacitor with 6 M KOH electrolyte, with 92% retention of initial capacitance as current density increased up to 100-fold. This performance was attributed to the dual contribution of electric double-layer capacitance and pseudo-capacitance. The assembled supercapacitor also exhibited excellent cycling stability, with 91% capacitance retention at 10 A/g after 10000 cycles.展开更多
The present paper covers the synthesis of ZSM-35 molecular sieve with 1,6-hexanediamine as templating agent,the influence of the synthesis conditions, and a discussion concerning the crystal structures of the products.
Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to ...Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.展开更多
A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites...A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites, ZSM-35 (FER-type), Silicalite-1(MFI-type) and Mordenite(MOR-type), are successfully synthesized in the solid system. In terms of commercial production, the technology-could simplify synthesis procedure and make the continuous production of zeolites possible, so as to improve the productivity. Additionally, it is environmentally friendly because the crystallization occurs in solid phase where there exists no pollution caused by waste liquid. Therefore, this technique provides us with a new industrial process for the clean and continuous production of zeolites. The characteristics in synthesis chemistry and the crystallization mechanism involved in the technology are also discussed.展开更多
A β-zeolite/polystyrene composite material was synthesized by co-deposition of mono-disperse polystyrene spheres and nano β-zeolite particles in aqueous suspension on a vertical substrate. Macro-porous β-zeolite wa...A β-zeolite/polystyrene composite material was synthesized by co-deposition of mono-disperse polystyrene spheres and nano β-zeolite particles in aqueous suspension on a vertical substrate. Macro-porous β-zeolite was obtained after the polystyrene template was removed by calcination. The micro/macro-pore structure of the prepared β-zeolite was highly ordered. In comparison with other assembly methods, the co-deposition method could obtain a highly ordered macro-porous material with relatively large zeolite filling particles, and therefore the co-deposition of particles with different size is a promising method for the fabrication of macro-porous materials.展开更多
ZSM-5 zeolites with similar St/Al ratio were synthesized successfully using various templates [n- butylamine （BTA）, tetrapropylammonium bromide （TPABr） and no template （NT）] under hydrothermal conditions, The sa...ZSM-5 zeolites with similar St/Al ratio were synthesized successfully using various templates [n- butylamine （BTA）, tetrapropylammonium bromide （TPABr） and no template （NT）] under hydrothermal conditions, The samples were characterized by XRD, SEM, Py-IR and BET surface area measurements in order to understand the template eiTects and the differences between the ZSM-5 santples. The synthesis of ZSM-5 with organic templates was relatively easier than those with inorganic templates and withnut template. SEM results revealed that ZSM-5 synthesized with different templates had different morphologies in similar particle size. Toluene disproportiortation reaction was carried out over the catalyst samples to evaluate the catalytic properties. The results have shown that large crystals which have a correspondingly small external surface showed a high para-xylene selectivity, and the amount of C9^＋ and C5^＋ was much less than that obtained from zeolite with small crystals.展开更多
The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate （DMC） via oxidative carbonylation of methanol was studied. A Cu/Y-zeolite catalyst was prepared by the ion exchange method from...The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate （DMC） via oxidative carbonylation of methanol was studied. A Cu/Y-zeolite catalyst was prepared by the ion exchange method from CuCl2.2H2O and the commercial NH4-form of the Y type zeolite, The catalyst was characterized by X-ray fluorescence （XRF）, N2 adsorption （BET method）, X-ray diffraction （XRD）, and temperature-programmed de- sorption of ammonia （NH3-TPD） to evaluate its Cu and Cl content, surface area, structure, and acidity. Reaction tests were carried out using an autoclave （batch reactor） for 18 h at 403 K and 5.5 MPa （2CH3OH ＋ 1/2O2 ＋ CO （CH3O）2CO ＋ H2O）. The influence of various dehydrating agents （ZnO, MgO, and CaO） was examined with the aim of increasing the methanol conversion （XMeOH, MeOH conversion）. The MeOH conversion increased upon addition of metal oxides in the order CaO 〉〉 MgO 〉 ZnO, with the DMC selectivity （SDMC） following the order MgO 〉 CaO 〉 ZnO. The catalysts and dehydrating agents were characterized before and after the oxidative carbonylation of methanol by thermogravimetric and differential thermogravimetric （TG/DTG）, and XRD to con- firm that the dehydration reaction occurred via the metal oxide （MO ＋ H2O →M（OH）2）. The MeOH conversion increased from 8.7% to 14.6% and DMC selectivity increased from 39.0% to 53.1%, when using the dehydrating azent CaO.展开更多
Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes ...Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was 12Na2O∶100SiO2∶2Al2O3∶5000H2O at 180 ℃ for 10 h, respectively. XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94×10-7, 3.27×10-7, 3.9×10-7, 3.14×10-7 and 0.874×10-7 mol·m2·s-1·Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2/CO2, H2/N2, H2/CH4 are 2.84, 2.73 and 2.29, respectively.展开更多
IM-5 zeolite was synthesized by hydrothermal crystallization method with 1,5-bis(N-methylpyrrolidinium)pentane bromide using the precursors N-methylpyrrolidine and 1,5-dibromopentane as raw materials of template after...IM-5 zeolite was synthesized by hydrothermal crystallization method with 1,5-bis(N-methylpyrrolidinium)pentane bromide using the precursors N-methylpyrrolidine and 1,5-dibromopentane as raw materials of template after pre-reaction,and then aluminum,alkali,water and silicon sources were added into the reaction system.The effects of the proportion of precursors and other materials and the reaction conditions on the crystallinity,crystal morphology and pore structure of the synthesized zeolites were systematically investigated,which provided the basic data for industrial production.The physical properties of the synthesized samples were analyzed by XRD,SEM,and N2 adsorptiondesorption techniques,and the catalytic performance of the samples was evaluated.The results show that IM-5 zeolite can be synthesized effectively by using the template pre-reaction method,and its physical properties and catalytic activity in catalytic alkylation of benzene and methanol are comparable to those of industrial samples synthesized by traditional method.展开更多
Though zeolites have been successfully synthesized for several decades,the roles of templates for zeolite synthesis are still not fully understood yet.Currently,many types of templates have been employed such as inorg...Though zeolites have been successfully synthesized for several decades,the roles of templates for zeolite synthesis are still not fully understood yet.Currently,many types of templates have been employed such as inorganic alkali metal ions,organic quaternary ammonium cations,organic amines,organic quaternary phosphonium cations,metal complexes and zeolite seeds,and the roles are mainly summarized into three aspects:structure-directing,space-filling and charge-balancing.In order to synthesize zeolites efficiently,the proposed principles to guide zeolite synthesis are the stabilization of energy between templates and zeolite framework,charge density mis-matching(CDM)and structure matching between zeolite frameworks and templates.The purpose of this review is to briefly summarize the progresses in recent years,clearly showing the roles of the templates for zeolite synthesis.展开更多
A zeolite designated as ZK-4 was synthesized hydrothermally in the system (TMA)2ONa2O-Al2O3- SiO2- H2O at 80 - 100℃ with tetramethylammonium hydroxide as an organic templating agent. The pure zeolite ZK-4 could be ...A zeolite designated as ZK-4 was synthesized hydrothermally in the system (TMA)2ONa2O-Al2O3- SiO2- H2O at 80 - 100℃ with tetramethylammonium hydroxide as an organic templating agent. The pure zeolite ZK-4 could be prepared by using the mother liquor obtained after filtration as the source of templating agent. The effect of some synthetic conditions such as the amount of tetramethylammonium hydroxide used, n [ (TMA)2O + Na2O] /n (Al2O3) ratio, n (SiO2)/n(Al2O3) ratio and crystallization time, etc. on the crystalline phase of the product was investigated. When the following molar ratios of the reaction mixture, n (SiO2)/n (Al2O3) 4-10, n[(TMA)2O+Na2O]/ n (Al2O3 ) > 7, n (Na2O)/n (Al2O3)=0. 5-2. 0, n (H2O)/ n(A12O3)=80-450, were used, pure zeolite ZK-4 could be obtained. The synthetic products were characterized by X-ray powder diffraction, atomic absorption spectrophotometry (AAS), adsorption measurement, thermogravimetric analysis(TGA), and 29Si magic angle spinning nuclear magnetic resonance technique. Zeolite ZK-4 has a higher thermal stability than sodium zeolite A due to higher n(Si)/n(Al) ratio of zeolite ZK-4.展开更多
Hierarchical ZSM-5 zeolite was hydrothermally synthesized by a novel silicone quaternary ammonium salt surfactant as a mesopore director.The crystallinity and the morphology of sample were characterized by X-ray diffr...Hierarchical ZSM-5 zeolite was hydrothermally synthesized by a novel silicone quaternary ammonium salt surfactant as a mesopore director.The crystallinity and the morphology of sample were characterized by X-ray diffraction(XRD),field-emission scanning electron microscope(FE-SEM),and transmission electronic microscope(TEM).Results indicated that the prepared ZSM-5 zeolites had good crystallinity,ellipsoid structure morphology and rough surface.Moreover,the pore size was enlarged to about 4 nm measured by nitrogen sorption,which indicated positive function of the synthesized template.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 21506184)Hunan 2011 Collaborative Center of Chemical Technologies for Environmental Benignity & Efficient Resource Utilization, and State Key Laboratory of Powder Metallurgy of Central South University
文摘N-doped carbons were fabricated from zeolite-templated carbon via modification with melamine and mild KOH activation. The N-doping treatment and KOH activation slightly lowered the surface areas of pristine zeolite-templated carbon; nonetheless, N-doped carbons with a lower surface area exhibited much higher capacitance and cycling stability as fabricated into symmetric supercapacitor. Significantly, N-doped carbon obtained at 700°C showed a capacitance of 45.7 F/g at 0.1 A/g and 42.0 F/g at 10 A/g for the fabricated supercapacitor with 6 M KOH electrolyte, with 92% retention of initial capacitance as current density increased up to 100-fold. This performance was attributed to the dual contribution of electric double-layer capacitance and pseudo-capacitance. The assembled supercapacitor also exhibited excellent cycling stability, with 91% capacitance retention at 10 A/g after 10000 cycles.
文摘The present paper covers the synthesis of ZSM-35 molecular sieve with 1,6-hexanediamine as templating agent,the influence of the synthesis conditions, and a discussion concerning the crystal structures of the products.
基金supported by the National Natural Science Foundation of China(Grant No.21802136)~~
文摘Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.
基金Supported by the National Natural Science Foundation of China (No.20173039) and by China National Petroleum Corporation (No.2002B50501)
文摘A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites, ZSM-35 (FER-type), Silicalite-1(MFI-type) and Mordenite(MOR-type), are successfully synthesized in the solid system. In terms of commercial production, the technology-could simplify synthesis procedure and make the continuous production of zeolites possible, so as to improve the productivity. Additionally, it is environmentally friendly because the crystallization occurs in solid phase where there exists no pollution caused by waste liquid. Therefore, this technique provides us with a new industrial process for the clean and continuous production of zeolites. The characteristics in synthesis chemistry and the crystallization mechanism involved in the technology are also discussed.
基金the National Basic Research Program of China （No. 2004CB217808） the National Natural Science Foundation of China （No. 20376046）.
文摘A β-zeolite/polystyrene composite material was synthesized by co-deposition of mono-disperse polystyrene spheres and nano β-zeolite particles in aqueous suspension on a vertical substrate. Macro-porous β-zeolite was obtained after the polystyrene template was removed by calcination. The micro/macro-pore structure of the prepared β-zeolite was highly ordered. In comparison with other assembly methods, the co-deposition method could obtain a highly ordered macro-porous material with relatively large zeolite filling particles, and therefore the co-deposition of particles with different size is a promising method for the fabrication of macro-porous materials.
文摘ZSM-5 zeolites with similar St/Al ratio were synthesized successfully using various templates [n- butylamine （BTA）, tetrapropylammonium bromide （TPABr） and no template （NT）] under hydrothermal conditions, The samples were characterized by XRD, SEM, Py-IR and BET surface area measurements in order to understand the template eiTects and the differences between the ZSM-5 santples. The synthesis of ZSM-5 with organic templates was relatively easier than those with inorganic templates and withnut template. SEM results revealed that ZSM-5 synthesized with different templates had different morphologies in similar particle size. Toluene disproportiortation reaction was carried out over the catalyst samples to evaluate the catalytic properties. The results have shown that large crystals which have a correspondingly small external surface showed a high para-xylene selectivity, and the amount of C9^＋ and C5^＋ was much less than that obtained from zeolite with small crystals.
文摘The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate （DMC） via oxidative carbonylation of methanol was studied. A Cu/Y-zeolite catalyst was prepared by the ion exchange method from CuCl2.2H2O and the commercial NH4-form of the Y type zeolite, The catalyst was characterized by X-ray fluorescence （XRF）, N2 adsorption （BET method）, X-ray diffraction （XRD）, and temperature-programmed de- sorption of ammonia （NH3-TPD） to evaluate its Cu and Cl content, surface area, structure, and acidity. Reaction tests were carried out using an autoclave （batch reactor） for 18 h at 403 K and 5.5 MPa （2CH3OH ＋ 1/2O2 ＋ CO （CH3O）2CO ＋ H2O）. The influence of various dehydrating agents （ZnO, MgO, and CaO） was examined with the aim of increasing the methanol conversion （XMeOH, MeOH conversion）. The MeOH conversion increased upon addition of metal oxides in the order CaO 〉〉 MgO 〉 ZnO, with the DMC selectivity （SDMC） following the order MgO 〉 CaO 〉 ZnO. The catalysts and dehydrating agents were characterized before and after the oxidative carbonylation of methanol by thermogravimetric and differential thermogravimetric （TG/DTG）, and XRD to con- firm that the dehydration reaction occurred via the metal oxide （MO ＋ H2O →M（OH）2）. The MeOH conversion increased from 8.7% to 14.6% and DMC selectivity increased from 39.0% to 53.1%, when using the dehydrating azent CaO.
基金This work was financially supported by the Specialized Research Fund for the Doctoral Program of High Education (SRFDP)(No.B20020288015).
文摘Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was 12Na2O∶100SiO2∶2Al2O3∶5000H2O at 180 ℃ for 10 h, respectively. XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94×10-7, 3.27×10-7, 3.9×10-7, 3.14×10-7 and 0.874×10-7 mol·m2·s-1·Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2/CO2, H2/N2, H2/CH4 are 2.84, 2.73 and 2.29, respectively.
文摘IM-5 zeolite was synthesized by hydrothermal crystallization method with 1,5-bis(N-methylpyrrolidinium)pentane bromide using the precursors N-methylpyrrolidine and 1,5-dibromopentane as raw materials of template after pre-reaction,and then aluminum,alkali,water and silicon sources were added into the reaction system.The effects of the proportion of precursors and other materials and the reaction conditions on the crystallinity,crystal morphology and pore structure of the synthesized zeolites were systematically investigated,which provided the basic data for industrial production.The physical properties of the synthesized samples were analyzed by XRD,SEM,and N2 adsorptiondesorption techniques,and the catalytic performance of the samples was evaluated.The results show that IM-5 zeolite can be synthesized effectively by using the template pre-reaction method,and its physical properties and catalytic activity in catalytic alkylation of benzene and methanol are comparable to those of industrial samples synthesized by traditional method.
基金supported by National Key Research and Development Program of China(2022YFA1503602)Key Research and Development Program of Zhejiang Province(2021C01080)National Natural Science Foundation of China(22125204).
文摘Though zeolites have been successfully synthesized for several decades,the roles of templates for zeolite synthesis are still not fully understood yet.Currently,many types of templates have been employed such as inorganic alkali metal ions,organic quaternary ammonium cations,organic amines,organic quaternary phosphonium cations,metal complexes and zeolite seeds,and the roles are mainly summarized into three aspects:structure-directing,space-filling and charge-balancing.In order to synthesize zeolites efficiently,the proposed principles to guide zeolite synthesis are the stabilization of energy between templates and zeolite framework,charge density mis-matching(CDM)and structure matching between zeolite frameworks and templates.The purpose of this review is to briefly summarize the progresses in recent years,clearly showing the roles of the templates for zeolite synthesis.
文摘A zeolite designated as ZK-4 was synthesized hydrothermally in the system (TMA)2ONa2O-Al2O3- SiO2- H2O at 80 - 100℃ with tetramethylammonium hydroxide as an organic templating agent. The pure zeolite ZK-4 could be prepared by using the mother liquor obtained after filtration as the source of templating agent. The effect of some synthetic conditions such as the amount of tetramethylammonium hydroxide used, n [ (TMA)2O + Na2O] /n (Al2O3) ratio, n (SiO2)/n(Al2O3) ratio and crystallization time, etc. on the crystalline phase of the product was investigated. When the following molar ratios of the reaction mixture, n (SiO2)/n (Al2O3) 4-10, n[(TMA)2O+Na2O]/ n (Al2O3 ) > 7, n (Na2O)/n (Al2O3)=0. 5-2. 0, n (H2O)/ n(A12O3)=80-450, were used, pure zeolite ZK-4 could be obtained. The synthetic products were characterized by X-ray powder diffraction, atomic absorption spectrophotometry (AAS), adsorption measurement, thermogravimetric analysis(TGA), and 29Si magic angle spinning nuclear magnetic resonance technique. Zeolite ZK-4 has a higher thermal stability than sodium zeolite A due to higher n(Si)/n(Al) ratio of zeolite ZK-4.
基金National Natural Science Foundation of China(No.21676053)
文摘Hierarchical ZSM-5 zeolite was hydrothermally synthesized by a novel silicone quaternary ammonium salt surfactant as a mesopore director.The crystallinity and the morphology of sample were characterized by X-ray diffraction(XRD),field-emission scanning electron microscope(FE-SEM),and transmission electronic microscope(TEM).Results indicated that the prepared ZSM-5 zeolites had good crystallinity,ellipsoid structure morphology and rough surface.Moreover,the pore size was enlarged to about 4 nm measured by nitrogen sorption,which indicated positive function of the synthesized template.
