Due to the low transport resistance,mullite hollow fiber(HF)could be regarded as a promising support for preparation of NaA zeolite membranes.However,insufficient coverage and undesired seed penetration often occur in...Due to the low transport resistance,mullite hollow fiber(HF)could be regarded as a promising support for preparation of NaA zeolite membranes.However,insufficient coverage and undesired seed penetration often occur in the seeding step of the mullite support due to the rough surfaces with ultra-large macropores(2-4 μm).This leads to poor intergrowth of the membrane layer.To solve this issue,cationic polyacrylamide(CPAM)was employed to modify the chemical and electrostatic properties of the mullite HF surface,where the electrostatic attraction between the surface and seed crystals could significantly promote the coating effect.In the seeding,the original seeds(3.2 μm)were mixed with the ball-milled seeds(0.3 μm)to improve the seed coverage,i.e.,the original seed was used to block the macropores on the support surface to prevent the penetration of small seeds,while the decked ball-milled seed was used to provide sufficient active sites to induce the intergrowth of the zeolite crystals.The effects of the concentration of CPAM,mixed mass ratio of seeds,and seed concentration on the preparation of NaA zeolite membranes were systematically examined,where the separation performances were characterized by pervaporation(PV)dehydration of 90%(mass)ethanol/water mixtures at 75℃.The results indicated that under a CPAM concentration of 0.7%(mass),an equivalent mass ratio of mixed seeds in a seed concentration of 1.0%(mass),the prepared mullite HF supported NaA zeolite membrane yielded the best PV performance,where the permeation flux and separation factor corresponded to 5.45 kg·m^(-2)·h^(-1)and 10000,respectively,being sufficient for industrial applications.展开更多
NaA zeolite membranes with 80 cm in length and 12.8 mm in outer diameter were prepared by our research group cooperating with Nanjing Jiusi Hi-Tech Co., China. The influence of dissolved inorganic salts and pH value i...NaA zeolite membranes with 80 cm in length and 12.8 mm in outer diameter were prepared by our research group cooperating with Nanjing Jiusi Hi-Tech Co., China. The influence of dissolved inorganic salts and pH value in the feed of isopropanol （IPA） solution on NaA zeolite membranes was investigated. It was found that both factors exhibited strong influence on the stability of NaA zeolite membranes. A set of pretreatment steps such as pH adjustment and distillation of the IPA solution were proposed to improve stability for pervaporation dehydration. An industrial-scale pervaporation facility with 52 m2 membrane area was built to dehydrate IPA solution from industrial cephalosporin production. The facility was continuously operated at 368-378 K to dehydrate IPA solution from water mass content of 15%-20% to less than 2% with a feed flow rate of 400-500 L·h^-1 and an average water flux of 1-1.5 kg·m^-2·h-1. The successful application of this facility suggested a promising application of NaA zeolite mem-brane for IPA recovery from pharmaceutical production.展开更多
A mass transfer model in consideration of multi-layer resistances through NaA zeolite membrane and lumen pressure drop in the permeate side was developed to describe pervaporation dehydration through scaled-up hollow ...A mass transfer model in consideration of multi-layer resistances through NaA zeolite membrane and lumen pressure drop in the permeate side was developed to describe pervaporation dehydration through scaled-up hollow fiber supported NaA zeolite membrane. It was found that the transfer resistance in the lumen of the permeate side is strongly related with geometric size of hollow fiber zeolite membrane, which could not he neglected. The effect of geometric size on pervaporation dehydration could be more significant under higher vacuum pressure in the permeate side. The transfer resistance in the lumen increases with the hollow fiber length but decreases with lumen diameter. The geometric structure could be optimized in terms of the ratio of lumen diameter to membrane length. A critical value of d1/L （Rc） to achieve high permeation flux was empirically correlated with extraction pressure in the permeate side. Typically, for a hollow fiber supported NaA zeolite membrane with length of 0.40 m, the lumen diameter should be larger than 2.0 mm under the extraction pressure of 1500 Pa.展开更多
A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 nm. The gas H2/N2 mixture separating results indic...A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 nm. The gas H2/N2 mixture separating results indicated that the mixture selectivity increased with increasing of synthesis times. In addition, selectivity of the three-step synthesis was higher than the value(3.74) expected from Kundsen diffusion.展开更多
Ion exchanging is one of the characteristics of the zeolites. Zeolites have octahedral and tetrahedral holes to trap ions and molecules. They also can exchange many ions in solution because of the size of the attendan...Ion exchanging is one of the characteristics of the zeolites. Zeolites have octahedral and tetrahedral holes to trap ions and molecules. They also can exchange many ions in solution because of the size of the attendant ions. As a matter of fact, the property of the ion-exchanged zeolites depends on the ligands involved in the ion exchanging solutions. Ion exchanged zeolites are used as catalyst for studying the anodic oxidation of methanol in an acidic medium to investigate their suitability for use in direct methanol fuel cells (DMFCs). Some of the zeolites that have exchanged ions are shown to have redox and catalytic properties [1-3]. As an example A. Itadani et al., have reported the preparation of copper ion exchanged ZSM-5 for calorimetric study of N2 adsorption on Cu-ZSM-5 zeolite [4]. In another study, A. Ribera et al. have reported the characterization of redox properties and application of Fe-ZSM-5 catalysts [5]. In this research we prepared silicate solutions by dissolving silica in sodium hydroxide. Aluminosilicate solutions with different Al/Si ratios were prepared by mixing appropriate quantities of sodium silicate solutions with freshly prepared sodium aluminate solutions and the NaA zeolites were made by hydrothermal method. Then, their XRD patterns and IR spectra were also considered. Obviously, those zeolites which have Al-OH and Si-OH groups can lose their protons in basic solutions. In this way zeolites can adsorb many ions with positive charge. We investigated ion exchange property of Fe3+, Cu2+, Ni2+ and Hg2+ in systems with pH equals to 2, 4, 6 and 8. We found that the aluminosilicate with Si/Al = 1, has greatest exchange capacity for all of the ions studied in this work.展开更多
系统研究了中空纤维Na A分子膜在蒸汽渗透中结合真空抽吸和N2吹扫操作对乙醇深度脱水的过程。研究发现吹扫作用在乙醇深度脱水中占主导作用,与未加吹扫气的对照工况(操作温度100℃、原料液进料流量为30 m L·min^(-1))相比,N_(2)吹...系统研究了中空纤维Na A分子膜在蒸汽渗透中结合真空抽吸和N2吹扫操作对乙醇深度脱水的过程。研究发现吹扫作用在乙醇深度脱水中占主导作用,与未加吹扫气的对照工况(操作温度100℃、原料液进料流量为30 m L·min^(-1))相比,N_(2)吹扫(吹扫气流量为60 m L·min^(-1))可加倍提升脱水速率,快速得到超低含水量乙醇(水的质量分数约0.5%),效率提升约43%;升高温度至120℃时,增大原料液进料流量为50 m L·min^(-1)时乙醇产品中水的质量分数可进一步降至0.068‰,收率达99.86%。展开更多
In this paper,we report a novel application of microwave radiation for the synthesis of zeolite NaA in a fraction of the time required for conventional synthetic method under very mild condition.The pure product was o...In this paper,we report a novel application of microwave radiation for the synthesis of zeolite NaA in a fraction of the time required for conventional synthetic method under very mild condition.The pure product was obtained under the condition of microwave radiation in 10-20 minutes.展开更多
A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals ...A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals was about 5 ~ 6 mm.展开更多
基金supported by the National Natural Science Foundation of China(22178166)Jiangsu Provincial Special Funds of Scientific and Technological Innovation for Carbon Peak and Carbon Neutrality(BE2022033-1,BE2022033-4)Chongqing Municipal Bureau of Science and Technology(cstc2021jcyj-msxmX0748).
文摘Due to the low transport resistance,mullite hollow fiber(HF)could be regarded as a promising support for preparation of NaA zeolite membranes.However,insufficient coverage and undesired seed penetration often occur in the seeding step of the mullite support due to the rough surfaces with ultra-large macropores(2-4 μm).This leads to poor intergrowth of the membrane layer.To solve this issue,cationic polyacrylamide(CPAM)was employed to modify the chemical and electrostatic properties of the mullite HF surface,where the electrostatic attraction between the surface and seed crystals could significantly promote the coating effect.In the seeding,the original seeds(3.2 μm)were mixed with the ball-milled seeds(0.3 μm)to improve the seed coverage,i.e.,the original seed was used to block the macropores on the support surface to prevent the penetration of small seeds,while the decked ball-milled seed was used to provide sufficient active sites to induce the intergrowth of the zeolite crystals.The effects of the concentration of CPAM,mixed mass ratio of seeds,and seed concentration on the preparation of NaA zeolite membranes were systematically examined,where the separation performances were characterized by pervaporation(PV)dehydration of 90%(mass)ethanol/water mixtures at 75℃.The results indicated that under a CPAM concentration of 0.7%(mass),an equivalent mass ratio of mixed seeds in a seed concentration of 1.0%(mass),the prepared mullite HF supported NaA zeolite membrane yielded the best PV performance,where the permeation flux and separation factor corresponded to 5.45 kg·m^(-2)·h^(-1)and 10000,respectively,being sufficient for industrial applications.
基金Supported by the National t）asic Research Program of China （2009CB623403）, the National High Technology Research and De velopment Program of China （2009AA034802）, the National Natural Science Foundation of China （20706030, U0834004）, the Science ＆ Technology Support Program （Industry） of Jiangsu Province of China （BE2008141）, the Natural Science Foundation of the Jiangsu Higher Education Institutions （09KJA530002） and 333 High-Level Personnel Training Project in Jiangsu Province. ＊＊ To whom correspondence should be addressed. E-mail： Xuehonggu@yahoo.com
文摘NaA zeolite membranes with 80 cm in length and 12.8 mm in outer diameter were prepared by our research group cooperating with Nanjing Jiusi Hi-Tech Co., China. The influence of dissolved inorganic salts and pH value in the feed of isopropanol （IPA） solution on NaA zeolite membranes was investigated. It was found that both factors exhibited strong influence on the stability of NaA zeolite membranes. A set of pretreatment steps such as pH adjustment and distillation of the IPA solution were proposed to improve stability for pervaporation dehydration. An industrial-scale pervaporation facility with 52 m2 membrane area was built to dehydrate IPA solution from industrial cephalosporin production. The facility was continuously operated at 368-378 K to dehydrate IPA solution from water mass content of 15%-20% to less than 2% with a feed flow rate of 400-500 L·h^-1 and an average water flux of 1-1.5 kg·m^-2·h-1. The successful application of this facility suggested a promising application of NaA zeolite mem-brane for IPA recovery from pharmaceutical production.
基金Supported by the National Natural Science Foundation of China(21490585 and21776128)the National High-tech R&D Program of China(2015AA03A602)+1 种基金the"Six Top Talents"and"333 Talent Project"of Jiangsu Provincethe Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘A mass transfer model in consideration of multi-layer resistances through NaA zeolite membrane and lumen pressure drop in the permeate side was developed to describe pervaporation dehydration through scaled-up hollow fiber supported NaA zeolite membrane. It was found that the transfer resistance in the lumen of the permeate side is strongly related with geometric size of hollow fiber zeolite membrane, which could not he neglected. The effect of geometric size on pervaporation dehydration could be more significant under higher vacuum pressure in the permeate side. The transfer resistance in the lumen increases with the hollow fiber length but decreases with lumen diameter. The geometric structure could be optimized in terms of the ratio of lumen diameter to membrane length. A critical value of d1/L （Rc） to achieve high permeation flux was empirically correlated with extraction pressure in the permeate side. Typically, for a hollow fiber supported NaA zeolite membrane with length of 0.40 m, the lumen diameter should be larger than 2.0 mm under the extraction pressure of 1500 Pa.
文摘A continuous and dense NaA zeolite membrane was synthesized by microwave heating method while employing a multi-step seeding LTA zeolite with the average size of 120 nm. The gas H2/N2 mixture separating results indicated that the mixture selectivity increased with increasing of synthesis times. In addition, selectivity of the three-step synthesis was higher than the value(3.74) expected from Kundsen diffusion.
文摘Ion exchanging is one of the characteristics of the zeolites. Zeolites have octahedral and tetrahedral holes to trap ions and molecules. They also can exchange many ions in solution because of the size of the attendant ions. As a matter of fact, the property of the ion-exchanged zeolites depends on the ligands involved in the ion exchanging solutions. Ion exchanged zeolites are used as catalyst for studying the anodic oxidation of methanol in an acidic medium to investigate their suitability for use in direct methanol fuel cells (DMFCs). Some of the zeolites that have exchanged ions are shown to have redox and catalytic properties [1-3]. As an example A. Itadani et al., have reported the preparation of copper ion exchanged ZSM-5 for calorimetric study of N2 adsorption on Cu-ZSM-5 zeolite [4]. In another study, A. Ribera et al. have reported the characterization of redox properties and application of Fe-ZSM-5 catalysts [5]. In this research we prepared silicate solutions by dissolving silica in sodium hydroxide. Aluminosilicate solutions with different Al/Si ratios were prepared by mixing appropriate quantities of sodium silicate solutions with freshly prepared sodium aluminate solutions and the NaA zeolites were made by hydrothermal method. Then, their XRD patterns and IR spectra were also considered. Obviously, those zeolites which have Al-OH and Si-OH groups can lose their protons in basic solutions. In this way zeolites can adsorb many ions with positive charge. We investigated ion exchange property of Fe3+, Cu2+, Ni2+ and Hg2+ in systems with pH equals to 2, 4, 6 and 8. We found that the aluminosilicate with Si/Al = 1, has greatest exchange capacity for all of the ions studied in this work.
文摘系统研究了中空纤维Na A分子膜在蒸汽渗透中结合真空抽吸和N2吹扫操作对乙醇深度脱水的过程。研究发现吹扫作用在乙醇深度脱水中占主导作用,与未加吹扫气的对照工况(操作温度100℃、原料液进料流量为30 m L·min^(-1))相比,N_(2)吹扫(吹扫气流量为60 m L·min^(-1))可加倍提升脱水速率,快速得到超低含水量乙醇(水的质量分数约0.5%),效率提升约43%;升高温度至120℃时,增大原料液进料流量为50 m L·min^(-1)时乙醇产品中水的质量分数可进一步降至0.068‰,收率达99.86%。
文摘In this paper,we report a novel application of microwave radiation for the synthesis of zeolite NaA in a fraction of the time required for conventional synthetic method under very mild condition.The pure product was obtained under the condition of microwave radiation in 10-20 minutes.
基金We are grateful to the financial support from the National Natural Science Foundation of China (59789201) and the National Advanced Materials Committee of China (715-006-0122).
文摘A NaA zeolite membrane was synthesized on the surface of the stainless steel slab. The membrane was characterized by XRD and SEM. The membrane was continuous and highly intergrown. The size of NaA zeolite crystals was about 5 ~ 6 mm.
