The coupling reactions of methanol and long-chain alkanes(n-dodecane,n-tetradecane and n-hexadecane)over CHA-type molecular sieves were studied in a fixed bed reactor.Over SAPO-34 and SSZ-13,it was found that the indu...The coupling reactions of methanol and long-chain alkanes(n-dodecane,n-tetradecane and n-hexadecane)over CHA-type molecular sieves were studied in a fixed bed reactor.Over SAPO-34 and SSZ-13,it was found that the induction period of methanol conversion was shortened by the introduction of long-chain alkanes.However,the addition of long-chain alkanes had little influence on the product distribution.Polymethylbenzenes and the derivatives were the main retained species on spent SSZ-13 catalyst,while adamantanes were the main retained species on SAPO-34.This indicates that coking species formation was mainly related to the further transformation of long-chain alkane/methanol coupling products at acid sites of the molecular sieve.These findings provide valuable information of long chain alkanes conversion and methanol reaction behavior of induction period over small pore CHA molecular sieves.展开更多
To address the challenges of high energy consumption and prominent costs in the traditional three-columns distillation process for cellulosic fuel ethanol,a distillation–molecular sieve coupling separation process is...To address the challenges of high energy consumption and prominent costs in the traditional three-columns distillation process for cellulosic fuel ethanol,a distillation–molecular sieve coupling separation process is proposed.This process integrates a three-column(crude distillation column,first distillation column,second distillation column)system with a 3A molecular sieve adsorption deep dehydration unit.A thermal coupling network is constructed via differential pressure design(steam from medium/high-pressure columns as mutual heat sources,reboiler liquid waste heat for feed preheating),and molecular sieve adsorption conditions are optimized.The study first performs a thermodynamic consistency test on the ethanol–water system,determines optimal non-random two-liquid(NRTL)model binary interaction parameters via experimental data regression for Aspen Plus simulation.Aiming at minimum total annual cost(TAC),Aspen Plus is used to optimize process parameters(theoretical tray number,feed location,reflux ratio,side-draw position,etc.).Economic analysis shows this process reduces CO_(2) emission costs by 27.56%,TAC by 15.58%(to 5.123×10^(6) USD·a^(−1)),and increases ethanol purity to>99.6%,providing an effective solution for green,efficient separation.展开更多
In order to address challenges posed by the reduction in transistor size,researchers are concentrating on two-dimensional(2D)materials with high dielectric constants and large band gaps.Monoclinic ZrO_(2)(m-ZrO_(2))ha...In order to address challenges posed by the reduction in transistor size,researchers are concentrating on two-dimensional(2D)materials with high dielectric constants and large band gaps.Monoclinic ZrO_(2)(m-ZrO_(2))has emerged as a promising gate dielectric material due to its suitable dielectric constant,wide band gap,ideal valence-band offset,and good thermodynamic stability.However,current deposition methods face compatibility issues with 2D semiconductors,highlighting the need for high-quality dielectrics and interfaces.Here,high-quality 2D m-ZrO_(2)single crystals are successfully prepared using a onestep chemical vapor deposition(CVD)method,aided by 5A molecular sieves for oxygen supply.The prepared ZrO_(2)is utilized as a gate dielectric in the construction of MoS2 field-effect transistors(FETs)to investigate its electrical property.The FETs exhibit a high carrier mobility of up to 5.50 cm^(2)·V^(−1)·s^(−1),and a current switching ratio(Ion/off)of approximately 10^(4),which aligns with the current standards of logic circuits,indicating that ZrO_(2)has application value as a gate dielectric.The successful onestep preparation of single-crystal ZrO_(2)paves the way for the utilization of high-κgate dielectrics and creates favorable conditions for the development of high-performance semiconductor devices,offering new possibilities for transistor miniaturization.展开更多
Samples of methane molecules grade diameter channel CHA-type molecular sieves(Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N...Samples of methane molecules grade diameter channel CHA-type molecular sieves(Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N2 follow a typical type-Ι behavior, which were fitted well with the Sips model(R2>0.999) and the selectivity was calculated using IAST theory. The results reveal that Chabazite-K has the highest selectivity(SCH4/N= 5.5).2 SSZ-13 has the largest capacity, which can adsorb up to a maximum of 30.957 cm3·g-1(STP) of CH4, due to it having the largest pore volume and surface area, but the lowest selectivity(SCH4/N2= 2.5). From the breakthrough test, we can conclude that SSZ-13 may be a suitable candidate for the recovery of CH4 from low concentration methane(CH4<20%) based on its larger pore volume and higher CH4 capacity. Chabazite-K is more suited to the separation of high concentration methane(CH4>50%) due to its higher selectivity.展开更多
Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference f...Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure. A 500 W high-pressure mercury lamp （main wave length 365 nm, 0.22 kW/m） was used as light source for irradiation, and air was introduced by a gas pump to supply O2. Thiophene can be photo-oxidized to sulfone, oxalic acid, SO4^2-, and CO2. The desulfurization yield of thiophene in n-octane is 58.9% under photo-irradiation for 5 h under the conditions of air flow at 150 mL/min and V（water）：V（n-octane）=1：1. It can be improved to 92.3% by adding 0.15 g zeoliteartificial into 100 mL reaction system, which is the adsorbent for O2 and thiophene. And under such conditions, the photo-oxidation kinetics of thiophene with O2/zeoliteartificial is first-order with an apparent rate constant of 0.5047 h^-1 and a half-time of 1.37 h. The sulfur content can be depressed from 800 μL/L to less than 62 μL/L.展开更多
Carbon capture is an important strategy and is implemented to achieve the goals of CO_(2)reduction and carbon neutrality.As a high energy-efficient technology,membrane-based separation plays a crucial role in CO_(2)ca...Carbon capture is an important strategy and is implemented to achieve the goals of CO_(2)reduction and carbon neutrality.As a high energy-efficient technology,membrane-based separation plays a crucial role in CO_(2)capture.It is urgently needed for membrane-based CO_(2)capture to develop the high-performance membrane materials with high permeability,selectivity,and stability.Herein,ultrapermeable carbon molecular sieve(CMS)membranes are fabricated by py roly zing a finely-engineered benzoxazole-containing copolyimide precursor for efficient CO_(2)capture.The microstructure of CMS membrane has been optimized by initially engineering the precursor-chemistry and subsequently tuning the pyrolysis process.Deep insights into the structure-property relationship of CMSs are provided in detail by a combination of experimental characterization and molecular simulations.We demonstrate that the intrinsically high free volume environment of the precursor,coupled with the steric hindrance of thermostable contorted fragments,promotes the formation of loosely packed and ultramicroporous carbon structures within the resultant CMS membrane,thereby enabling efficient CO_(2)discrimination via size sieving and affinity.The membrane achieves an ultrahigh CO_(2)permeability,good selectivity,and excellent stability.After one month of long-term operation,the CO_(2)permeability in the mixed gas is maintained at 11,800 Barrer,with a CO_(2)/N_(2)selectivity exceeding 60.This study provides insights into the relationship between precursor-chemistry and CMS performance,and our ultrapermeable CMS membrane,which is scalable using thin film manufacturing,holds great potential for industrial CO_(2)capture.展开更多
A series of Cr-containing MCM-41 molecular sieves crystallized at room temperature with a hexagonal and well-ordered structure were synthesized. XRD, FT-IR and DRS UV-Vis techniques were used to characterize the sampl...A series of Cr-containing MCM-41 molecular sieves crystallized at room temperature with a hexagonal and well-ordered structure were synthesized. XRD, FT-IR and DRS UV-Vis techniques were used to characterize the samples. The results indicate incorporation of Cr into the MCM-41 framework, and dispersion of some CrsO3 on the surface or/and in the bulk of the MCM-41. Test of catalytic properties of the series of samples for the topic reaction was carried out using a continuous-flow fixed-bed quartz reactor. Factors influencing the catalytic performance for this title reaction, such as Cr/Si ratio in MCM- 41 and reaction temperature were investigated. The experimental results indicate that over the 5%CrMCM-41 a 43.27% conversion of ethane and a 86.70% selectivity for ethylene were achieved in the ethane dehydrogenation with COs to ethylene at 973 K. It is suggested that both Cr^6＋ and Cr^3＋ are the catalytic activity center.展开更多
Lead, a heavy metal, is a well known contaminant in water and has been reported to cause serious health implications to humans, animals, and plants. One of the processes for heavy metal remediation of contaminated wat...Lead, a heavy metal, is a well known contaminant in water and has been reported to cause serious health implications to humans, animals, and plants. One of the processes for heavy metal remediation of contaminated water is chemical precipitation. In this present work, chemical precipitation of lead from a contaminated aqueous matrix by chlorides, carbonates, and sulfates of sodium and calcium was compared to lead removal by molecular sieves and biomaterials (fishbone, grape and spinach). The order of lead removal from 1400 ppm of lead solution is sodium chloride (31%) < calcium chloride (62%) burnt grape (83%) < charred spinach (92.3%) < sodium phosphate (95.8%) < sodium carbonate (97%) < molecular sieve sphere (98.7%) < sodium sulfate (99.3%) s ground (99.71%) < fishbone (99.87%)展开更多
Thermally stable mesoporous silica and Ti-containing molecular sieves have been synthesized at mild temperature using low-cost and biodegradable --- amphoteric tetradecyl betaine as template. The physicochemical chara...Thermally stable mesoporous silica and Ti-containing molecular sieves have been synthesized at mild temperature using low-cost and biodegradable --- amphoteric tetradecyl betaine as template. The physicochemical characterizations proved that Ti(IV) could be incorporated in the mesoporous struture.展开更多
A series of Ag,Cu and Co-doped manganese oxide octahedral molecular sieves(OMS-2) were synthesized and evaluated to remove nitrogen oxides(NOx) from cigarette mainstream smoke.The three kinds of catalysts were added t...A series of Ag,Cu and Co-doped manganese oxide octahedral molecular sieves(OMS-2) were synthesized and evaluated to remove nitrogen oxides(NOx) from cigarette mainstream smoke.The three kinds of catalysts were added to cigarettes for studying the capabilities of reducing NOx from cigarette mainstream smoke.The catalysis and reduction of NO in laboratory were studied.A mechanism for NOx catalytic reduction from burning cigarettes with the catalysts adding to cigarettes was described.The catalysts show excellent catalytic activity for NOx removal,especially the Ag-doped OMS-2 catalyst.0.5%(mass fraction) Ag-doped OMS-2 catalyst has the best ability to remove NOx from cigarette mainstream smoke.The use of Ag-doped OMS-2 as catalyst for removing carcinogenic compounds from cigarette smoke will be an effective strategy to protect the environment and public health.展开更多
In view of the problems associated with large amount of discharged wastewater and serious pollution in the existing technology for removing sodium species from molecular sieves,this research work introduces the bipola...In view of the problems associated with large amount of discharged wastewater and serious pollution in the existing technology for removing sodium species from molecular sieves,this research work introduces the bipolar membrane electrodialysis into the process of removing sodium species from molecular sieves,and proposes a novel method of cleanly removing sodium from molecular sieves.The results show that the technology for removing sodium ions from the molecular sieves with an indirect electrodialysis process is feasible,and can recover Na OH solution.The bipolar membrane electrodialysis is especially suitable for treating the USY,ZSM-5 and Beta molecular sieves with high acid-resistance,and the physicochemical properties and catalytic performance of the prepared molecular sieves are roughly equivalent to those of the ammonium ion-exchange method.In comparison with the ammonium ion-exchange method,the process is clean and environmentally friendly,which consumes less water,and does not discharge wastewater to exhibit a rosy prospect of industrial application.展开更多
Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancin...Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancing carbon neutrality and sustainable development.Given the ubiquitous presence of water during catalyst synthesis,storage,and application,the interactions between water and molecular sieves as well as their consequent effects on frameworks and catalytic reactions have attracted considerable attention.These effects are inherently complex and highly dependent on various factors such as temperature,water phase,and partial pressure.In this review,we provide a comprehensive overview of the current understanding of water-molecular sieve interactions and their roles in catalysis,based on both experimental and theoretical calculation results.Special attention is paid to water-induced reversible and irreversible structural changes in aluminosilicate and SAPO frameworks at the atomic level,underscoring the dynamic and labile nature of these frameworks in water environments.The influence of water on catalytic performance and reaction kinetics in molecular sieve-catalyzed reactions is discussed from two perspectives:(1)its participation in reaction through hydrogen bonding interactions,such as competitive adsorption at active sites,stabilization of ground and transition states,and proton transfer bridge;(2)its role as a direct reactant forming new species via reactions with other vip molecules.Recent advancements in this area provide valuable insights for the rational design and optimization of catalysts for water-involved reactions.展开更多
Silicoaluminophosphate(SAPO)molecular sieves possess diverse architectures and exceptional high-temperature hydrothermal stability,rendering them important acid catalysts.However,enhancing acid concentration of certai...Silicoaluminophosphate(SAPO)molecular sieves possess diverse architectures and exceptional high-temperature hydrothermal stability,rendering them important acid catalysts.However,enhancing acid concentration of certain SAPO materials remains challenging,which limits their catalytic applications.Here,we report the synthesis of a series of SAPO materials using a developed SAPO precursor plus dual template(SPDT)strategy.A variety of SAPO materials characterized by high silica content and enhanced acidity,such as SAPO-34/56 intergrowths,SAPO-56,and SAPO-17,have been synthesized and thoroughly characterized using various techniques including integrated differential phase-contrast scanning transmission electron microscopy,two-dimensional solid-state nuclear magnetic resonance spectroscopy,and continuous rotation electron diffraction.The use of silica-enriched SAPO precursor combined with the flexible selection of the second template enables the crystalline phase regulation and improves the Si atoms incorporation into the framework.Notably,the synthesized SAPO-17 with abundant Si(4Al)species and unprecedentedly high acid density exhibits exceptional DeNO_(x)activity after Cu loading,with NO_(x)conversion exceeding 90%at 175–700℃.This outstanding performance can be attributed to the unique ERI structure and the increased acidity of SAPO-17.This work not only presents an effective method for synthesizing SAPO molecular sieves with enhanced acidity but also offers a new perspective for expanding the active temperature range of the ammonia selective catalytic reduction reaction.展开更多
In order to study the donor ability of ferrocenylimines as directing ortho metalation group（DMG） to lithium alkylide to prepare planar chiral ferrocene, a series of ferrocenyl schiff bases were synthesized by new me...In order to study the donor ability of ferrocenylimines as directing ortho metalation group（DMG） to lithium alkylide to prepare planar chiral ferrocene, a series of ferrocenyl schiff bases were synthesized by new methods using molecular sieves（0.4nm） and AlCl3 as catalysts. The reaction periods were reduced using these two catalysts in contrast with Al2O3, which was a traditional method used in the literature. In addition, as an important feature of these schiff bases, we found that they were unstable as oils in air or when filtrated through silica gel, but were stable as solids. The structures of the new compounds were confirmed by IR, ^1H NMR and HRMS.展开更多
The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnopho...The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnophosphate molecular sieves, the synthesis of the molecular sieves of VPI-5 type ls of many unique features. Both VPI-5 and Si-VPI-5 were characterized by XRD, IR, TG-DTA, and MAS-NMR.展开更多
In this paper,the bi-functional catalyst system composed of molecular sieve（MCM-41） immobilized oligomerization catalyst（C25H17Cl2N3·FeCl2） and copolymerization catalyst（Et（Ind）2ZrCl2） was employed in the...In this paper,the bi-functional catalyst system composed of molecular sieve（MCM-41） immobilized oligomerization catalyst（C25H17Cl2N3·FeCl2） and copolymerization catalyst（Et（Ind）2ZrCl2） was employed in the in situ copolymerization of ethylene aiming to prepare the Linear low density polyethylene（LLDPE）.In this paper,we mainly argued the regular pattern of the in situ copolymerization of ethylene in limited nano-space and compared it with that happening in free space.The impact of variance of the reaction temperature,Fe/Zr value and the A1/（Fe＋Zr） value on the activity of the in situ copolymerization of ethylene has also been introduced.Furthermore,the degree of branching,thermal properties and crystalline changes of the obtained polymerization products prepared from different reactivity were investigated.展开更多
The nanostrutured mesoporous silica materials MCM-41 with different pore sizes were synthesized by adding 1,3,5-trimethylbenzene (TMB) as assistant agent in the reactant mixture. The obtained samples were investigated...The nanostrutured mesoporous silica materials MCM-41 with different pore sizes were synthesized by adding 1,3,5-trimethylbenzene (TMB) as assistant agent in the reactant mixture. The obtained samples were investigated by XRD, HRTEM, FTIR and N_2 adsorptions. It is shown that the pore sizes, ordered degree and specific surface area increase effectively with the incremental addition of TMB in an appropriate range, but the (100) peak intensity of XRD pattern becomes weakened and the ordered degree decreases when the additive quantity continued to increase. With the addition of TMB in an appropriate range, the effective surfactant ion pair packing parameter, g=V/a_0l, is mediated in the range of 1/3-1/2 with the increment of V and l, indicating that mesoporous silica is a well-ordered hexagonal structure. However, when the addition of TMB increases, g value becomes larger, which leads to a less long-range ordered structure for the uneven condissolution of TMB.展开更多
MAPO-11 molecular sieves were synthesized by hydrothermal methods. The influence of precursor of magnesium, Mg/Al ratio, synthesis temperature, synthesis time and the type of template on the formation and properties o...MAPO-11 molecular sieves were synthesized by hydrothermal methods. The influence of precursor of magnesium, Mg/Al ratio, synthesis temperature, synthesis time and the type of template on the formation and properties of MAPO-11 molecular sieves was examined. The samples were characterized by the techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric/differential thermogravimetric analysis (TG-DGA), etc. The results show that the shape and size of crystal were influenced by the precursor of Mg, the Mg/Al ratio and the type of template, and the TG-DGA analysis shows that MAPO-11 molecular sieves as-synthesized have poor thermal stability.展开更多
基金Supported by National Natural Science Foundation of China(21991093)。
文摘The coupling reactions of methanol and long-chain alkanes(n-dodecane,n-tetradecane and n-hexadecane)over CHA-type molecular sieves were studied in a fixed bed reactor.Over SAPO-34 and SSZ-13,it was found that the induction period of methanol conversion was shortened by the introduction of long-chain alkanes.However,the addition of long-chain alkanes had little influence on the product distribution.Polymethylbenzenes and the derivatives were the main retained species on spent SSZ-13 catalyst,while adamantanes were the main retained species on SAPO-34.This indicates that coking species formation was mainly related to the further transformation of long-chain alkane/methanol coupling products at acid sites of the molecular sieve.These findings provide valuable information of long chain alkanes conversion and methanol reaction behavior of induction period over small pore CHA molecular sieves.
基金support from the National Key Research and Development Program of China(2022YFC2106300)the National Natural Science Foundation of China(42177400).
文摘To address the challenges of high energy consumption and prominent costs in the traditional three-columns distillation process for cellulosic fuel ethanol,a distillation–molecular sieve coupling separation process is proposed.This process integrates a three-column(crude distillation column,first distillation column,second distillation column)system with a 3A molecular sieve adsorption deep dehydration unit.A thermal coupling network is constructed via differential pressure design(steam from medium/high-pressure columns as mutual heat sources,reboiler liquid waste heat for feed preheating),and molecular sieve adsorption conditions are optimized.The study first performs a thermodynamic consistency test on the ethanol–water system,determines optimal non-random two-liquid(NRTL)model binary interaction parameters via experimental data regression for Aspen Plus simulation.Aiming at minimum total annual cost(TAC),Aspen Plus is used to optimize process parameters(theoretical tray number,feed location,reflux ratio,side-draw position,etc.).Economic analysis shows this process reduces CO_(2) emission costs by 27.56%,TAC by 15.58%(to 5.123×10^(6) USD·a^(−1)),and increases ethanol purity to>99.6%,providing an effective solution for green,efficient separation.
基金support from the National Natural Science Foundation of China(No.21975067)Shenzhen Science and Technology Program(No.JCYJ20220530160407016).
文摘In order to address challenges posed by the reduction in transistor size,researchers are concentrating on two-dimensional(2D)materials with high dielectric constants and large band gaps.Monoclinic ZrO_(2)(m-ZrO_(2))has emerged as a promising gate dielectric material due to its suitable dielectric constant,wide band gap,ideal valence-band offset,and good thermodynamic stability.However,current deposition methods face compatibility issues with 2D semiconductors,highlighting the need for high-quality dielectrics and interfaces.Here,high-quality 2D m-ZrO_(2)single crystals are successfully prepared using a onestep chemical vapor deposition(CVD)method,aided by 5A molecular sieves for oxygen supply.The prepared ZrO_(2)is utilized as a gate dielectric in the construction of MoS2 field-effect transistors(FETs)to investigate its electrical property.The FETs exhibit a high carrier mobility of up to 5.50 cm^(2)·V^(−1)·s^(−1),and a current switching ratio(Ion/off)of approximately 10^(4),which aligns with the current standards of logic circuits,indicating that ZrO_(2)has application value as a gate dielectric.The successful onestep preparation of single-crystal ZrO_(2)paves the way for the utilization of high-κgate dielectrics and creates favorable conditions for the development of high-performance semiconductor devices,offering new possibilities for transistor miniaturization.
基金financial support from the National Natural Science Foundation of China (Nos. 51672186, 21676175)
文摘Samples of methane molecules grade diameter channel CHA-type molecular sieves(Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N2 follow a typical type-Ι behavior, which were fitted well with the Sips model(R2>0.999) and the selectivity was calculated using IAST theory. The results reveal that Chabazite-K has the highest selectivity(SCH4/N= 5.5).2 SSZ-13 has the largest capacity, which can adsorb up to a maximum of 30.957 cm3·g-1(STP) of CH4, due to it having the largest pore volume and surface area, but the lowest selectivity(SCH4/N2= 2.5). From the breakthrough test, we can conclude that SSZ-13 may be a suitable candidate for the recovery of CH4 from low concentration methane(CH4<20%) based on its larger pore volume and higher CH4 capacity. Chabazite-K is more suited to the separation of high concentration methane(CH4>50%) due to its higher selectivity.
基金Science and Technology Development Planning Foundation of Jilin Province, China(No.20030405)
文摘Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure. A 500 W high-pressure mercury lamp （main wave length 365 nm, 0.22 kW/m） was used as light source for irradiation, and air was introduced by a gas pump to supply O2. Thiophene can be photo-oxidized to sulfone, oxalic acid, SO4^2-, and CO2. The desulfurization yield of thiophene in n-octane is 58.9% under photo-irradiation for 5 h under the conditions of air flow at 150 mL/min and V（water）：V（n-octane）=1：1. It can be improved to 92.3% by adding 0.15 g zeoliteartificial into 100 mL reaction system, which is the adsorbent for O2 and thiophene. And under such conditions, the photo-oxidation kinetics of thiophene with O2/zeoliteartificial is first-order with an apparent rate constant of 0.5047 h^-1 and a half-time of 1.37 h. The sulfur content can be depressed from 800 μL/L to less than 62 μL/L.
基金financial support from the National Key R&D Program of China(2021YFB3801200)the National Natural Science Foundation of China(22278051,22178044,22308043)CNPC Innovation Found(2022DQ02-0608)。
文摘Carbon capture is an important strategy and is implemented to achieve the goals of CO_(2)reduction and carbon neutrality.As a high energy-efficient technology,membrane-based separation plays a crucial role in CO_(2)capture.It is urgently needed for membrane-based CO_(2)capture to develop the high-performance membrane materials with high permeability,selectivity,and stability.Herein,ultrapermeable carbon molecular sieve(CMS)membranes are fabricated by py roly zing a finely-engineered benzoxazole-containing copolyimide precursor for efficient CO_(2)capture.The microstructure of CMS membrane has been optimized by initially engineering the precursor-chemistry and subsequently tuning the pyrolysis process.Deep insights into the structure-property relationship of CMSs are provided in detail by a combination of experimental characterization and molecular simulations.We demonstrate that the intrinsically high free volume environment of the precursor,coupled with the steric hindrance of thermostable contorted fragments,promotes the formation of loosely packed and ultramicroporous carbon structures within the resultant CMS membrane,thereby enabling efficient CO_(2)discrimination via size sieving and affinity.The membrane achieves an ultrahigh CO_(2)permeability,good selectivity,and excellent stability.After one month of long-term operation,the CO_(2)permeability in the mixed gas is maintained at 11,800 Barrer,with a CO_(2)/N_(2)selectivity exceeding 60.This study provides insights into the relationship between precursor-chemistry and CMS performance,and our ultrapermeable CMS membrane,which is scalable using thin film manufacturing,holds great potential for industrial CO_(2)capture.
基金This work was financially supported by the Sci—ence and Technology Department of Jilin Province，China(20040703—2)and the sub·Program of the Sci—ence and Technology Cooperation Project between China and Spain．
文摘A series of Cr-containing MCM-41 molecular sieves crystallized at room temperature with a hexagonal and well-ordered structure were synthesized. XRD, FT-IR and DRS UV-Vis techniques were used to characterize the samples. The results indicate incorporation of Cr into the MCM-41 framework, and dispersion of some CrsO3 on the surface or/and in the bulk of the MCM-41. Test of catalytic properties of the series of samples for the topic reaction was carried out using a continuous-flow fixed-bed quartz reactor. Factors influencing the catalytic performance for this title reaction, such as Cr/Si ratio in MCM- 41 and reaction temperature were investigated. The experimental results indicate that over the 5%CrMCM-41 a 43.27% conversion of ethane and a 86.70% selectivity for ethylene were achieved in the ethane dehydrogenation with COs to ethylene at 973 K. It is suggested that both Cr^6＋ and Cr^3＋ are the catalytic activity center.
文摘Lead, a heavy metal, is a well known contaminant in water and has been reported to cause serious health implications to humans, animals, and plants. One of the processes for heavy metal remediation of contaminated water is chemical precipitation. In this present work, chemical precipitation of lead from a contaminated aqueous matrix by chlorides, carbonates, and sulfates of sodium and calcium was compared to lead removal by molecular sieves and biomaterials (fishbone, grape and spinach). The order of lead removal from 1400 ppm of lead solution is sodium chloride (31%) < calcium chloride (62%) burnt grape (83%) < charred spinach (92.3%) < sodium phosphate (95.8%) < sodium carbonate (97%) < molecular sieve sphere (98.7%) < sodium sulfate (99.3%) s ground (99.71%) < fishbone (99.87%)
文摘Thermally stable mesoporous silica and Ti-containing molecular sieves have been synthesized at mild temperature using low-cost and biodegradable --- amphoteric tetradecyl betaine as template. The physicochemical characterizations proved that Ti(IV) could be incorporated in the mesoporous struture.
文摘A series of Ag,Cu and Co-doped manganese oxide octahedral molecular sieves(OMS-2) were synthesized and evaluated to remove nitrogen oxides(NOx) from cigarette mainstream smoke.The three kinds of catalysts were added to cigarettes for studying the capabilities of reducing NOx from cigarette mainstream smoke.The catalysis and reduction of NO in laboratory were studied.A mechanism for NOx catalytic reduction from burning cigarettes with the catalysts adding to cigarettes was described.The catalysts show excellent catalytic activity for NOx removal,especially the Ag-doped OMS-2 catalyst.0.5%(mass fraction) Ag-doped OMS-2 catalyst has the best ability to remove NOx from cigarette mainstream smoke.The use of Ag-doped OMS-2 as catalyst for removing carcinogenic compounds from cigarette smoke will be an effective strategy to protect the environment and public health.
基金financially supported by the National Basic Research Program of China(973 Program)under the Grant No.2015AA03A061
文摘In view of the problems associated with large amount of discharged wastewater and serious pollution in the existing technology for removing sodium species from molecular sieves,this research work introduces the bipolar membrane electrodialysis into the process of removing sodium species from molecular sieves,and proposes a novel method of cleanly removing sodium from molecular sieves.The results show that the technology for removing sodium ions from the molecular sieves with an indirect electrodialysis process is feasible,and can recover Na OH solution.The bipolar membrane electrodialysis is especially suitable for treating the USY,ZSM-5 and Beta molecular sieves with high acid-resistance,and the physicochemical properties and catalytic performance of the prepared molecular sieves are roughly equivalent to those of the ammonium ion-exchange method.In comparison with the ammonium ion-exchange method,the process is clean and environmentally friendly,which consumes less water,and does not discharge wastewater to exhibit a rosy prospect of industrial application.
文摘Porous molecular sieve catalysts,including aluminosilicate zeolites and silicoaluminophosphate(SAPO)molecular sieves,have found widespread use in heterogeneous catalysis and are expected to play a key role in advancing carbon neutrality and sustainable development.Given the ubiquitous presence of water during catalyst synthesis,storage,and application,the interactions between water and molecular sieves as well as their consequent effects on frameworks and catalytic reactions have attracted considerable attention.These effects are inherently complex and highly dependent on various factors such as temperature,water phase,and partial pressure.In this review,we provide a comprehensive overview of the current understanding of water-molecular sieve interactions and their roles in catalysis,based on both experimental and theoretical calculation results.Special attention is paid to water-induced reversible and irreversible structural changes in aluminosilicate and SAPO frameworks at the atomic level,underscoring the dynamic and labile nature of these frameworks in water environments.The influence of water on catalytic performance and reaction kinetics in molecular sieve-catalyzed reactions is discussed from two perspectives:(1)its participation in reaction through hydrogen bonding interactions,such as competitive adsorption at active sites,stabilization of ground and transition states,and proton transfer bridge;(2)its role as a direct reactant forming new species via reactions with other vip molecules.Recent advancements in this area provide valuable insights for the rational design and optimization of catalysts for water-involved reactions.
文摘Silicoaluminophosphate(SAPO)molecular sieves possess diverse architectures and exceptional high-temperature hydrothermal stability,rendering them important acid catalysts.However,enhancing acid concentration of certain SAPO materials remains challenging,which limits their catalytic applications.Here,we report the synthesis of a series of SAPO materials using a developed SAPO precursor plus dual template(SPDT)strategy.A variety of SAPO materials characterized by high silica content and enhanced acidity,such as SAPO-34/56 intergrowths,SAPO-56,and SAPO-17,have been synthesized and thoroughly characterized using various techniques including integrated differential phase-contrast scanning transmission electron microscopy,two-dimensional solid-state nuclear magnetic resonance spectroscopy,and continuous rotation electron diffraction.The use of silica-enriched SAPO precursor combined with the flexible selection of the second template enables the crystalline phase regulation and improves the Si atoms incorporation into the framework.Notably,the synthesized SAPO-17 with abundant Si(4Al)species and unprecedentedly high acid density exhibits exceptional DeNO_(x)activity after Cu loading,with NO_(x)conversion exceeding 90%at 175–700℃.This outstanding performance can be attributed to the unique ERI structure and the increased acidity of SAPO-17.This work not only presents an effective method for synthesizing SAPO molecular sieves with enhanced acidity but also offers a new perspective for expanding the active temperature range of the ammonia selective catalytic reduction reaction.
文摘In order to study the donor ability of ferrocenylimines as directing ortho metalation group（DMG） to lithium alkylide to prepare planar chiral ferrocene, a series of ferrocenyl schiff bases were synthesized by new methods using molecular sieves（0.4nm） and AlCl3 as catalysts. The reaction periods were reduced using these two catalysts in contrast with Al2O3, which was a traditional method used in the literature. In addition, as an important feature of these schiff bases, we found that they were unstable as oils in air or when filtrated through silica gel, but were stable as solids. The structures of the new compounds were confirmed by IR, ^1H NMR and HRMS.
基金Supported by the National Natural Science Foundation of China
文摘The large pore molecular sieves VPI-5 and Si VPI-5 were synthesized by using three organic amines (dipropylamine, diisopropylamine and dipentylamine) as the structure-directing agents. Compared with general alumlnophosphate molecular sieves, the synthesis of the molecular sieves of VPI-5 type ls of many unique features. Both VPI-5 and Si-VPI-5 were characterized by XRD, IR, TG-DTA, and MAS-NMR.
基金Supported by the National "Eleventh Five-Year" Technology Support Program Project (2006BAD10B08)Natural Science Foundation of Hebei Province (E2009000448)
文摘In this paper,the bi-functional catalyst system composed of molecular sieve（MCM-41） immobilized oligomerization catalyst（C25H17Cl2N3·FeCl2） and copolymerization catalyst（Et（Ind）2ZrCl2） was employed in the in situ copolymerization of ethylene aiming to prepare the Linear low density polyethylene（LLDPE）.In this paper,we mainly argued the regular pattern of the in situ copolymerization of ethylene in limited nano-space and compared it with that happening in free space.The impact of variance of the reaction temperature,Fe/Zr value and the A1/（Fe＋Zr） value on the activity of the in situ copolymerization of ethylene has also been introduced.Furthermore,the degree of branching,thermal properties and crystalline changes of the obtained polymerization products prepared from different reactivity were investigated.
文摘The nanostrutured mesoporous silica materials MCM-41 with different pore sizes were synthesized by adding 1,3,5-trimethylbenzene (TMB) as assistant agent in the reactant mixture. The obtained samples were investigated by XRD, HRTEM, FTIR and N_2 adsorptions. It is shown that the pore sizes, ordered degree and specific surface area increase effectively with the incremental addition of TMB in an appropriate range, but the (100) peak intensity of XRD pattern becomes weakened and the ordered degree decreases when the additive quantity continued to increase. With the addition of TMB in an appropriate range, the effective surfactant ion pair packing parameter, g=V/a_0l, is mediated in the range of 1/3-1/2 with the increment of V and l, indicating that mesoporous silica is a well-ordered hexagonal structure. However, when the addition of TMB increases, g value becomes larger, which leads to a less long-range ordered structure for the uneven condissolution of TMB.
文摘MAPO-11 molecular sieves were synthesized by hydrothermal methods. The influence of precursor of magnesium, Mg/Al ratio, synthesis temperature, synthesis time and the type of template on the formation and properties of MAPO-11 molecular sieves was examined. The samples were characterized by the techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric/differential thermogravimetric analysis (TG-DGA), etc. The results show that the shape and size of crystal were influenced by the precursor of Mg, the Mg/Al ratio and the type of template, and the TG-DGA analysis shows that MAPO-11 molecular sieves as-synthesized have poor thermal stability.
