Synthesis and Characterization of ZSM-5/β Co-Crystalline Zeolite

ZSM-5/β co-crystalline zeolites with different content of ZSM-5 have been synthesized by adding different amount of ZSM-5 to the synthetic system ofβ zeolite with NaAlO2, silica sol as the source of aluminum and silica, respectively, and TEA as the template under controlled condition of the synthesis. The ZSM-5/β co-crystalline zeolite was studied by XRD, SEM, BET and NH3-TPD. The reaction activity of toluene alkylation was investigated with a mixture of toluene-methanol as the feedstock in a pulse micro-reactor over the ZSM-5/β co-crystalline zeolite. It is found that ZSM-5/β co-crystalline zeolite has two kinds of zeolite structure including ZSM-5 and β zeolite, not in the form of a physical mixture. The pore structure of ZSM-5/β co-crystalline zeolites is different from that forβ zeolite, ZSM-5and their physical mixture. In addition, the peaks of both high and low temperature desorption of ammonia over the ZSM-5/β co-crystalline zeolite shift 23 ℃ to lower temperatures and the acid amount of its strong acid is 3% more than the physical mixture. So the ZSM-5/β co-crystalline zeolite produces the highest content of xylene, which is 10.4% higher than the physical mixture. And the ZSM-5/β co-crystalline zeolite has better selectivity for toluene alkylation and weaker de-methylation than β zeolite, ZSM-5 and their physical mixture.     

Synthesis and Characterization of ZSM-5/β Co-Crystalline Zeolite

ZSM-5/β co-crystalline zeolites with different content of ZSM-5 have been synthesized by adding different amount of ZSM-5 to the synthetic system of β zeolite with NaAlO2, silica sol as the source of aluminum and silica, respectively, and TEA as the template under controlled condition of the synthesis. The ZSM-5/β co-crystalline zeolite was studied by XRD, SEM, BET and NH3-TPD. The reaction activity of toluene alkylation was investigated with a mixture of toluene-methanol as the feedstock in a pulse micro-reactor over the ZSM-5/β co-crystalline zeolite. It is found that ZSM-5/β co-crystalline zeolite has two kinds of zeolite structure including ZSM-5 and β zeolite, not in the form of a physical mixture. The pore structure of ZSM-5/β co-crystalline zeolites is different from that for β zeolite, ZSM-5 and their physical mixture. In addition, the peaks of both high and low temperature desorption of ammonia over the ZSM-5/β co-crystalline zeolite shift 23 ℃ to lower temperatures and the acid amount of its strong acid is 3% more than the physical mixture. So the ZSM-5/β co-crystalline zeolite produces the highest content of xylene, which is 10.4% higher than the physical mixture. And the ZSM-5/β co-crystalline zeolite has better selectivity for toluene alkylation and weaker de-methylation than β zeolite, ZSM-5 and their physical mixture.     

Toluene Alkylation to Selective Formation of p-Xylene over Co-Crystalline ZSM-12/ZSM-5 Catalyst

The alkylation of toluene with methanol to selective formation of p-xylene has been systematically studied. ZSM-12 (MTW)/ZSM-5 co-crystalline zeolite in 40:60 proportions have been synthesized by the same molar gel composition, but at different temperatures and periods than that of ZSM-12 and ZSM-5, separately. All the prepared samples are characterized by XRD, SEM, BET, and XRF. The activity of toluene alkylation was investigated with a mixture of toluene and methanol as a feed over the ZSM-12, ZSM-12/ZSM-5 co-crystalline, ZSM-5, and physical mixture of ZSM-12/ZSM-5. Prom characterization, it is observed that the ZSM-12/ZSM-5 co-crystalline material is different from that of ZSM-12, ZSM-5, and their physical mixture. Further, the ZSM-12/ZSM-5 co-crystalline zeolite produces the highest content of xylene and has better selectivity for p-xylene than ZSM-12, ZSM-5, and their physical mixture.     

Dealuminated ZSM-5 Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Bronsted acid sites in the formation of higher hydrocarbons. The oligomerization of olefins, dependent on the acidity of ZSM-5 zeolite, is an important step in the conversion of natural gas to liquid fuels. The framework Si/Al ratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst. ZSM-5 with the mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to the acidic ion-exchange method to produce ZSM-5 with various Si/Al ratios. The FT-IR analysis revealed that the integrated framework aluminum band, non-framework aluminum band, and silanol groups areas of the ZSM-5 zeolites decreased after being dealuminated. The performance of the dealuminated zeolite was tested for ethylene oligomerization. The results demonstrated that the dealumination of ZSM-5 led to higher ethylene conversion, but the gasoline selectivity was reduced compared to the performance     

Effect of Alkali Treatment on the Structure and Catalytic Properties of ZSM-5 Zeolite

Catalytic properties of ZSM-5 zeolite samples pretreated with NaOH solution have been investigated. The samples are characterized by XRD, SEM, chemical analysis, and N2 adsorption.The results indicate that mesopores are created in ZSM-5 crystals under alkali treatment without change the microporous structure and acidic strength of the zeolite, but the crystallinity is greatly decreased under severe treatment. IR indicates that the concentration of silanol is greatly enriched by alkali treatment. The etherification activities of ZSM-5 zeolites are greatly increased byalkali-treatment. The noticeably improved catalytic activity of treated samples is ascribed to the formation of mesopores and greatly enriched silanol group.     

PERVAPORATION OF ETHANOL/WATER MIXTURES WITH HIGH FLUX BY ZEOLITE-FILLED PDMS/PVDF COMPOSITE MEMBRANES

Thin-film zeolite-filled silicone/PVDF composite membranes were fabricated by incorporating zeolite particles into PDMS(poly(dimethylsiloxane)) membranes.The morphology of zeolite particles and zeolite filled silicone composite membranes were characterized by SEM.The zeolite-filled PDMS/PVDF composite membranes were applied for the pervaporation of ethanol/water mixtures and showed higher flux compared with that reported in literatures.The effect of zeolite loading and Si/Al ratio of zeolite particles on...     

Dealuminated ZSM—5 Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Broensted acid sites in the formation of higher hydrocarbons,The oligomeriztion of olefins,dependent on the acidity of ZSM-5 zeolite ,is an important step in the conversion of natural gas to liquied fuels,The framework Si/Al ratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst,ZSM-5 with the mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to the acidic ion-exchange method to produce ZSM-5 with various Si/Al ratios,The FT-IR analysis revealed that the integrated framework aluminum band,non-framework aluminum band,and silanol groups areas of the ZSM-5 zeolites decreased after being dealuminated,The performanc of the dealuminated zeolite was tested for ethylene oligomerization.The results demonstrated that the dealumination of ZSM-5 led to higher ethylene conversion,but the gasoline selectivity was reduced compared to the performance of a ZSM-5 zeolite ,The characterization results revealed the amount of aluminum in the zeolitic framework,the crystallinity of the ZSM-5 zeolite,and the Si/Al ration affected the formation of Broensted acid sites,The number of the Broensted acid sites on the catalyst active sites is important in the olefin conversion to liquied hydrocarbons.     

微波场中A型分子筛及分子筛膜合成的研究

Effects of aging time and alkalinity as well as cation concentration(Na⁺) on the synthesis of A type zeolite and zeolite membrane were investigated in this paper. The results showed that aging time for synthesis of A type zeolite and zeolite membrane had remarkable influence and alkalinity could accelerate the formation of zeolite but was disadvantage to zeolite membrane synthesis. Cation concentration(Na⁺) also couldn′t accelerate the synthesis of zeolite and zeolite membrane but it was probable an important factor to accelerate crystal growth .Moreover, more compact zeolite membranes could be synthesized by this method while the thickness of membrane was thinner than that of convention. Zeolites and zeolite membranes were characterized by XRD, TEM as well as IR characterization techniques.     

碱金属盐对ZSM-5分子筛晶化的影响

Effect of different alkali metal salts on the crystal size and the crystallization rate of ZSM-5 zeolite was de-tailedly investigated in this paper. The samples prepared by adding the different alkali metal salts were character-ized by using XRD， TEM， TG-DSC， BET and IR techniques. The XRD results showed that， for the nanosized ZSM-5 zeolite， the characteristic peaks broadened on the XRD patterns in comparison with the microsized ZSM-5 zeolite. The SEM results verified that the crystal size of zeolites prepared by adding different alkali metal salts had different results， and adding NaCl， NaC₂H₃O₂ and KCl showed the better effect of reducing crystal size， which are about of 40～60nm size. The crystallization curve of adding the different alkali metal salts suggested that the crystallization rate was significantly affected by the anions in the alkali metal salt besides the cations. Moreover， the crystal size likewise depended on the anion in the alkali metal salt. In addition， the BET results suggested that the nanosized ZSM-5 zeolite possessed a larger outer surface area in comparison with the microsized ZSM-5 zeolite. The thermostability of the samples was determined by TG-DSC technique， indicating that the nanosized ZSM-5 zeolite had a poor thermostability as compared with the microsized ZSM-5 zeolite. The possible difference of the samples with different crystal sizes on IR spectra was also given.     

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nanosized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. These catalyst samples were characterized by XRD, BET, NH3-TPD, TEM, Py-IR and TG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at T = 405 °C, WHSV = 4.74 h-1and P = 1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m2/g, larger than that of mesoporous ZSM-5(66 m2/g) and nanosized ZSM-5(76 m2/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5(86 h), but shorter than that of nanosized ZSM-5(104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. The special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. This special structural zeolite is a potential catalyst for methanol to gasoline reaction.     

ZSM-5分子筛膜的研究进展

本文分析了ZSM-5分子筛膜的主要合成方法和研究现状,总结了ZSM-5分子筛膜的缺陷与修饰方法,指出了ZSM-5分子筛膜的表征手段是以XRD、SEM、TEM和单组分气体渗透等为主,对ZSM-5分子筛膜的应用和前景进行了展望。     

MFI型分子膜的制备与H2S/CH4分离性能

采用二次生长法在多孔α-Al₂O₃载体上制备MFI型（ZSM-5和silicate-1）分子筛膜;通过XRD和SEM检测,证明所合成的分子筛膜为致密、交联和无取向的MFI型分子筛膜,厚度为5 μm;单组分气体渗透实验检测中,所制备样品膜的N₂渗透量均小于10^-11 mol/（m²·s·Pa）,可认为其无缺陷;同时,考察了样品分子筛膜对H₂S/CH₄混合气的分离效果,在渗透压分别为0.3和0.5 MPa时,silicate-1分子筛膜的H₂S/CH₄的分离因子分别为1.99和4.44,而ZSM-5分子筛膜的CH₄/H₂S的分离因子分别为6.71和12.85。     

高硅ZSM—5沸石填充硅橡胶膜的醇—水渗透蒸发分离性质

高硅ZSM－5沸石填充疏水性硅橡胶蓦地低浓度醇－水体度醇－水体的渗透蒸发性质的研究有明，提高沸石硅铝比，增加填充量以及进行酸处理皆有利于改善膜对醇－水的分离系数和通量。料液的成，浓度以及温度对膜的分离性质也有显著影响。     

低温加氢裂解脱除高硅ZSM-5分子筛内TPAOH模板剂

分子筛膜的合成和应用是近年来的研究热点, 特别是具有独特孔道结构的MFI 型分子筛膜. 但由于膜内有机模板剂在高温脱除时会导致膜产生缺陷, 进而影响分子筛膜的应用. 所以分子筛膜及分子筛晶体中有机模板剂的低温脱除工艺一直是研究者们致力解决的问题之一. 本文系统考察了高硅ZSM-5分子筛晶体内有机模板剂(四丙基氢氧化铵, TPAOH)在H₂/N₂气氛下的低温裂解脱除规律, 采用低温加氢裂解工艺, 在350 ℃以下可有效脱除分子筛晶体孔道内的有机模板剂. 通过对裂解后分子筛晶体的比表面积(BET)、热失重(TG)、傅里叶变换红外(FTIR)光谱和拉曼光谱表征证实, 相比于空气和氮气气氛, 含氢还原性气氛更有利于模板剂的低温脱除, 脱除率随温度的升高而增加; 280 ℃时, 加氢裂解后晶体的BET比表面积已达到252 m²·g^-1, 仍有少量有机残余物; 350 ℃时, 加氢裂解后晶体的BET比表面积可达到399 m²·g^-1, 仅有微量无机碳残余物. 此外, 低温加氢裂解后的分子筛表面相对洁净, 且氨气程序升温脱附(NH₃-TPD)结果表明低温加氢裂解后的ZSM-5 分子筛晶体具有相对较多的酸性位.     

二次生长法合成ZSM-5分子筛膜的影响因素

具有均匀孔径的分子筛膜在催化反应器、膜分离等领域显示其巨大潜力.通过适宜路线制备高质量分子筛膜成为膜研究的热点.负载晶种的二次生长法在高性能ZSM-5分子筛膜的制备中表现出巨大的优势.从膜层的连续性、渗透性、选择性这3个分子筛膜最重要的性能指标出发,重点分析了晶种尺寸、用量、分散介质、载体内部生长、反应温度、有机模板剂的去除等因素对于分子筛膜性能的影响,阐述了其作用机理以及已经应用的改良手段.综述了ZSM-5分子筛膜的研究现状和亟待解决的技术难题,并展望了ZSM-5分子筛膜的应用.     

醇盐水解法合成ZSM-5沸石

用正硅酸乙酯（ＴＥＯＳ）冰解作硅源、三氯化铝作铝源合成了ＺＳＭ－５沸石,并和传统的水玻璃作硅源合成ＺＳＭ－５法进行了比较。用ＸＲＤ、热重／差热分析、红外光谱和正己烷吸附等对实验产品进行了表征。醇盐水解法比传统方法结晶速度快,可缩短合成时间。新法合成的ＺＳＭ－５沸石结晶度高、憎水性强、晶粒易于取向生长,对合成沸石膜非常有利。     

PREPARATION OF SILICALITE-1 AND ZSM-5 ZEOLITE/ CERAMIC COMPOSITE MEMBRANES

ＰＲＥＰＡＲＡＴＩＯＮＯＦＳＩＬＩＣＡＬＩＴＥ┐１ＡＮＤＺＳＭ┐５ＺＥＯＬＩＴＥ／ＣＥＲＡＭＩＣＣＯＭＰＯＳＩＴＥＭＥＭＢＲＡＮＥＳＺｈａｎｇＬｉｘｉｏｎｇ，ＪｉａＭｅｎｇｄｏｎｇ，ＭｉｎＥｎｚｅ（ＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＰｅｔｒｏｌｅ...     

变温晶化合成高渗透率ZSM-5沸石膜

沸石分子筛膜的分离性能优异 ,在膜反应器方面具有巨大的应用前景 ,使得在十多年的时间里 ,对其的研究取得了长足进展 .渗透率与选择性是沸石膜发展过程中一对相互制约的矛盾 ,只有当其具有较高渗透率和良好的选择性时 ,才能体现出优势 .因此 ,在不降低选择性的前提下 ,提高膜的渗透率便成为研究的重点 .迄今为止 ,国内外研究者们分别采取不同措施以合成高渗透率的 ZSM- 5沸石膜 ,如合成小晶粒分子筛以减小膜厚 [1] ,在载体孔内预设置扩散栏以阻碍沸石晶粒在孔内生成 [2 ] ;在中孔载体表面合成沸石膜 [3～ 5]等 ,但渗透结果表明 ,气体的渗…     

The preparation and analysis of zeolite ZSM-5 membranes on porous alumina supports

Zeolite ZSM-5 particles formed in the synthesis solution assume a negative charge due to electrical double layer effects. Therefore, we investigated the use of electrophoretic techniques in addition to the hydrothermal synthesis method to attract the zeolite particles to the substrate surface before they precipitate out of the solution. This electrophoretic driving force produces a thin, continuous zeolite ZSM-5 membrane on the porous substrate. This research was conducted in order to produce zeolite membranes on a tubular support that could effect continuous gas phase separations. The thickness of membranes can be controlled by varying the precursor concentration, applied potential, and synthesis time. The selectivity of n-butane over iso-butane is observed on every membrane. The membranes were characterized by using scanning electron microscopy (SEM), X-ray diffractometry (XRD), and energy dispersive X-ray spectrometry (EDX).