Bread-template synthesis of hierarchical mesoporous ZSM-5 zeolite with hydrothermally stable mesoporosity

A hierarchical mesoporous ZSM-5 zeolite has been synthesized by using starch-derived bread as a meso-template. The obtained mesoporous ZSM-5 was characterized with X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric (TG)/differential thermal analysis (DTA) techniques. Hydrothermal treatments revealed that the mesoporosity in hierarchical mesoporous ZSM-5 exhibited excellent hydrothermal stability. Catalytic tests showed that hierarchical mesoporous ZSM-5 was more active than conventional zeolite of ZSM-5 in catalytic cracking of 1,3,5-tri-isopropylbenzene. Hydrogen adsorption measurements showed hierarchical mesoporous ZSM-5 had a higher storage capacity than the conventional ZSM-5.     

多级孔ZSM-5负载的钴催化剂的费-托合成催化性能

采用水蒸气辅助转晶(SAC)法合成了粒径均一(180 nm)的纳米ZSM-5颗粒,颗粒间堆积形成大量的开放介孔,与ZSM-5的微孔共同形成多级孔结构。以该材料为载体采用满孔浸渍法制备了负载量为15%(质量分数)的钴催化剂。采用XRD、SEM、TEM、N_2物理吸附-脱附等表征技术对多级孔ZSM-5载体及其负载催化剂的形貌和结构进行了表征,并对催化剂的费-托合成催化性能进行了测试。结果表明,相比于大颗粒的ZSM-5和商业ZSM-5,多级孔ZSM-5负载的钴催化剂的费-托合成活性最高,CH_4选择性最低,C_(5-20)产物的选择性高达68.9%,这归因于多级孔ZSM-5的介孔孔道有效地促进反应过程中产物的传质扩散以及ZSM-5微孔骨架上的酸中心促进了长链烃产物的二次加氢裂解。     

单一微孔模板剂一锅法制备多级结构ZSM-5沸石

以微孔模板剂四丙基氢氧化铵为单一模板剂,采用一种温和的低温水热一锅法工艺,成功制备出多级结构ZSM-5沸石(HSZs)。与传统的双模板法和后处理法相比,这种结合了沸石生长与后刻蚀于一体的新方法,不仅减少了模板剂的用量及二次酸/碱刻蚀、煅烧造成的环境污染,同时也极大地简化了合成工艺。利用XRD, N2吸附, SEM, TEM, XRF,27Al NMR与NH3-TPD等测试手段对合成的HSZs进行了全面表征,并提出了一种“成核/生长-刻蚀/再晶化”的形成机理。与传统ZSM-5沸石相比,这种具有均一梭型形貌的HSZs具有高的水热稳定性,并在三异丙苯催化裂解的探针反应中表现出优异催化性能和较长使用寿命。     

一步法合成多级孔结构ZSM-5分子筛

多级孔结构ZSM-5分子筛的合成过程复杂。利用双模板剂,通过优化晶化条件(如晶化时间与晶化温度)和Si/Al物质的量比等一步水热晶化合成了具有多级孔结构的ZSM-5分子筛,并采用XRD、N₂吸附-脱附、吡啶红外吸脱附、SEM和TEM等方法对样品的晶体结构、孔道结构、表面酸性和形貌等进行了表征。结果表明,一步法合成多级孔结构ZSM-5分子筛的适宜条件是:晶化温度160-180℃,晶化时间24-96 h,反应物组成为SiO₂/Al₂O₃/Na₂O/CTAB/TPABr/H₂O=1/x/0.4/0.05/0.12/280,(x:50-240)。其中,晶化温度160℃、晶化时间48 h和以Si/Al物质的量比50的凝胶合成的样品具有有序的介孔(平均尺寸3.60 nm)结构、较高的结晶度和较强的酸性。     

Fabricating hierarchical ZSM-5 to induct long chain antioxidant coenzyme Q10 for biomedical application

The study investigates the hydrophobic antioxidant Coenzyme Q10 (CoQ10) adsorption over industrially relevant hierarchical ZSM-5 for potential therapeutic applications. The designing of hierarchical nanocomposites was optimized with two different NaOH/CTAB ratios (0.18 and 0.62) over ZSM-5 (SiO₂/Al₂O₃ = 22–27) of different crystal sizes (0.5 µm, 2.0 µm and 3.0 µm) and different SiO₂/Al₂O₃ ratios (23, 80, 280 and 1500) through top-down approach. Hydrothermal stability of samples was studied using 100% water steam at 700 °C and 750 °C for 2 h, respectively. Reassembling nano ZSM-5 into hierarchical composite was found to exhibit ordered/disordered hexagonal mesophase depending on alkaline treated ZSM-5 crystal sizes and silica to alumina ratios. The phase changes were analyzed using different textural characterizations such as X-ray diffraction, BET surface area, ammonia desorption technique, ²⁷Al MAS NMR, thermogravimetric analysis and transmission electron microscope. 21 different nanoformulations were screened for CoQ10 adsorption and subsequently selected samples were applied for curcumin and ascorbic acid adsorption. Hierarchical ZSM-5 with SiO₂/Al₂O₃ ratio 80 (ZSM-5-80 (0.62)) was found to be steam stable and optimum with highest Q10 adsorption (55%). The adsorption influence over different crystal size and silica to alumina ratios, clearly showed the dependency over synergistic action of textural characteristics such as external surface area, pore volume, and weak acidity. The structured nanosupports with pore sizes between 3 and 4.0 nm were found to exhibit highest CoQ10 adsorption.     

纳米 ZSM-22分子筛的水热合成及在甲醇转化反应中的性能

分子筛结构的独特性和多样性使其在催化、吸附分离和离子交换等领域有着广泛应用.近年来,纳米分子筛制备和应用受到极大关注.与传统微米分子筛相比,纳米分子筛具有较小的晶粒尺寸、较大的外表面积和较高的表面活性,能显著提高其分离和催化性能.制备纳米晶体的常用方法有过量模板法、空间限定法、晶种法、离子热合成法及微反应器合成法等.目前,已合成出多种拓扑结构的纳米分子筛,包括 FAU, MFI, MEL和CHA等. ZSM-22是一种具有 TON拓扑结构的一维十元环直孔道分子筛(孔口尺寸为0.45 nm ×0.55 nm),在长链烷烃异构化和烯烃异构化等反应中表现出优异的催化活性.水热合成法是制备 ZSM-22分子筛最常用的方法,所得样品晶粒尺寸为2–15μm,但由于 ZSM-22分子筛是一种亚稳态结构,为了防止杂晶生成,合成通常是在剧烈搅拌(通常大于400 r/min)下进行.目前已有报道在较低转速下合成 ZSM-22分子筛,但产物仍为微米晶体;或在微波辅助水热合成条件下合成亚微米 ZSM-22分子筛,但晶体尺寸不可调且合成过程需要较高功率的微波反应器.因此,在水热条件下合成纯纳米 ZSM-22分子筛仍然是一个巨大挑战.本文在上述研究基础上采用改进的水热合成法成功合成出纳米 ZSM-22分子筛,考察了转速﹑硅铝比及乙醇共溶剂对晶粒尺寸的影响,比较了纳米和常规微米 ZSM-22分子筛的甲醇转化反应性能.结果表明,采用改进的水热合成法能够在较低转速下合成出纳米 ZSM-22分子筛,晶体尺寸在150–800 nm范围可调.通过考察转速对晶粒尺寸的影响,发现静态合成条件下无法形成 ZSM-22分子筛,表明 ZSM-22分子筛合成需要一定的转速.转速在10–50 r/min变化时,可以合成出不同晶体尺寸的 ZSM-22分子筛,且随转速提高, ZSM-22分子筛晶体尺寸先减小后增大,表明纳米 ZSM-22分子筛合成存在最佳转速.另外,配料硅铝比能显著影响 ZSM-22分子筛晶体尺寸,随配料硅铝比增加, ZSM-22分子筛晶体尺寸先减小后增大.通过在合成体系中添加乙醇作为共溶剂,考察了有机溶剂对 ZSM-22分子筛晶粒尺寸的影响,发现有机溶剂能显著增大 ZSM-22的晶体尺寸.将本文合成的纳米和常规微米 ZSM-22分子筛用于甲醇转化反应,考察了晶体尺寸对 ZSM-22分子筛甲醇转化反应性能的影响.发现与常规微米 ZSM-22分子筛相比,纳米 ZSM-22分子筛催化剂寿命显著提高,说明晶粒尺寸减小能有效减缓积碳导致的分子筛失活;同时,反应产物中乙烯和芳烃选择性有所提高,这是由于外表面积增大所致.此外,还考察了不同硅铝比 ZSM-22分子筛的甲醇转化反应性能.结果表明,分子筛硅铝比会影响催化剂寿命,但晶体尺寸对催化剂寿命影响更大. ZSM-22分子筛硅铝比增大有助于提高低碳烯烃选择性,减少芳烃生成.     

ZSM-5、ZSM-57分子筛和丝光沸石间的转晶规律

考察了硅铝比、碱度、有机胺模板剂、晶化时间及温度等合成条件对ZSM-5、ZSM-57 分子筛和丝光沸石之间相互转晶的影响. 发现较高的碱度、较长的晶化时间有利于合成丝光沸石；较低的碱度、较高的诱导晶化温度、较长的晶化时间有利于合成低硅铝比的ZSM-57 分子筛；合成低硅铝比的ZSM-5分子筛则需要在能合成丝光沸石和ZSM-57 分子筛的碱度区间内精确调节碱度, 缩短晶化时间、降低诱导晶化温度、加入适当晶种, 有利于合成低硅铝比的ZSM-5 分子筛. 合成条件稍微改变, 会导致各种沸石之间发生转晶, 晶化产物出现两种或两种以上的晶型.     

Nitridation: A simple way to improve the catalytic performance of hierarchical porous ZSM-5 in benzene alkylation with methanol

Nitrided hierarchical porous ZSM-5 was synthesized by nitridation of hierarchical porous ZSM-5 with flowing ammonia at elevated temperature. The samples were characterized by XRD, SEM, Nitrogen sorption isotherms, NH₃-TPD and Py-IR, and evaluated in alkylation of benzene and methanol. The result indicated that the high specific surface area of parent ZSM-5 was maintained, while the Brönsted acidity was effectively adjusted by nitridation. Moreover, the high suppression of ethylbenzene was observed on nitrided catalyst and this could be attributed to the decrease of Brönsted acidity which suppressed the methanol to olefins reactions.     

Syntheses and Characterization of ZSM-5 Zeolites Containing Diethylamine and Ethylenediamine

Syntheses of ZSM-5 zeolites from R-SiO2-Al2O3-H2O-HF(R = diethylamine and ethylenediamine, respectively) were investigated by using the hydrothermal crystallization. The large single crystals of ZSM-5 containing diethylamine and ethylenediamine were synthesized. The ZSM-5 precursors were characterized by means of X-ray powder diffraction, scanning electron microscopy, thermal analysis and electron microprobe analysis. The analysis result of aluminium distribution shows that the interior aluminium content of large crystals of ZSM-5 zeolites is rather low.     

ZSM-5 catalyzed one pot three-component synthesis of 5-substituted-1H-tetrazoles from aldehyde

Abstract

In this paper, we report one-pot three-component synthesis of 5-substituted-1H-tetrazoles from aldehyde using zeolite-based heterogeneous catalyst (ZSM-5). Wide functional group tolerance with high chemical yield has been achieved. Moreover, heterogeneous catalyst (ZSM-5) was recovered and reused several times without significant loss of its catalytic activity     

Influence of template on crystallization of ZSM-5 zeolites

Pentasil zeolites of ZSM-5 type are synthesised hydrothermally using triethyl-n-proplyammonium bromide (TEPA-Br) and triethyl-n-butylammonium bromide (TEBA-Br). The crystallization kinetics, followed by XRD, SEM and thermal analysis, clearly demonstrate the influence of size and molecular weight of the templating quaternary ammonium cation (QAC) species on the rates of nucleation and crystallization. The values of the apparent activation energies for nucleation and crystal growth indicate that both nucleation and crystal growth are faster when TEPA-Br rather than TEBA-Br is used as a template. The quantitative identification of intergrown phases characterizes both the phases to be ZSM-5 zeolite. Thermoanalytical curves for both these zeolites in as-synthesised forms exhibit two-step oxidative decomposition of the occluded organic species. This suggests that the quaternary ammonium cation may be located at two energetically different sites within the zeolite channels. The equilibrium sorption capacity, however, is found to increase in the order of size and molecular weight of the templating species in both the zeolites. The nature of acid site distribution, obtained from the temperature programmed desorption of ammonia is found to be independent of the templating species used during the synthesis.     

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。     

In-situ Synthesis of Binderless ZSM-5 Zeolitic Coatings on Aluminum

ZSM-5 zeolitic coatings on aluminum have been prepared successfully by in-situ hydrothermal synthesis method and ZSM-5/Al monolith was formed. The effects of pH value and crystallization time on the in-situ synthesis were discussed.     

Functionalized Hierarchical ZSM-5 Zeolites for the Viscosity Reduction of Heavy Oil at Low Temperature

Herein, we propose a novel approach to reduce the viscosity of heavy oil by functional hierarchical CTMS-ZSM-5-PTMS zeolites. CTMS-ZSM-5-PTMS zeolites synthesized by asymmetric modification and selective alkali etching can reduce the viscosity of heavy oil through adsorbing asphaltenes. This method can reduce the viscosity of heavy oil from hundreds of thousands mPa·s to about ten thousand mPa·s. The work provides an economical and environmentally friendly candidate for heavy oil viscosity reduction under low-temperature conditions.     

Hierarchical ZSM-5 catalyst synthesized by a Triton X-100 assisted hydrothermal method

ZSM-5 zeolite with a hexagonal cubic morphology was synthesized by a hydrothermal method using Triton X-100, a nonionic surfactant. The samples prepared with and without the surfactant were characteriz...     

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.     

硅胶原位合成ZSM-5分子筛及其催化性能的研究

以正丁胺为模板剂,采用水热晶化法在固体硅胶小球上原位合成了ZSM-5分子筛。考察了晶化温度、晶化时间、初始凝胶硅铝比及H2O/ SiO2、BuNH2/ SiO2、OH-/SiO2对ZSM-5相对结晶度的影响,得到了ZSM 5的合成化学规律。采用XRD、SEM、FT IR及N2吸附手段对固体硅胶小球上原位合成的复合结构分子筛进行了表征。结果表明,这种材料具有介孔和微孔的复合结构特征,而且很好地保持了硅胶小球的形貌。以大庆VGO为原料,在重油微反装置上对该复合结构分子筛进行催化性能评价。结果表明,使用硅胶原位合成的ZSM-5分子筛可显著提高低碳烯烃选择性和收率。     

高岭土微球上无胺法ZSM-5的原位合成

无胺体系中,采用水热法在焙烧高岭土微球上原位晶化合成了ZSM-5分子筛。考察了晶化温度、晶化时间、晶种加入量以及合成体系硅铝比等主要因素对分子筛合成的影响,得出了较佳的原位晶化合成条件。采用XRD、SEM、N₂吸附脱附等手段对合成样品进行了表征。结果表明：在高岭土微球上合成出了颗粒尺寸小于1 μm的小晶粒原位ZSM-5分子筛;晶化产物的比表面积、总孔容、微孔表面积和微孔孔容均明显增大,微孔分布集中于0.54 nm。     

无有机胺体系中高硅ZSM-5沸石的一步合成

在无有机胺模板剂和不加晶种体系中,采用较低晶化温度(130℃),在水热体系中一步合成了形貌均一的板块状高硅ZSM-5沸石(n_(SiO_2)/n_(Al_2O_390)。系统地考察了合成体系中原料的物质的量之比对合成ZSM-5沸石的影响。通过X射线衍射(XRD),傅里叶红外光谱(FT-IR),扫描电镜(SEM),低温氮气吸附/脱附和固体核磁共振(~(29)Si MAS NMR)等技术手段对合成的ZSM-5沸石进行了物化表征。结果表明,当原料的物质的量之比n_(C_2H_5OH)/n_(SiO_2)=2.8、n_(Na_2O)/n_(SiO_2)=0.14和n_(SiO_2)/n_(Al_2O_3)=150时,可合成具有高结晶度的ZSM-5纯相沸石。比表面积和微孔孔容分别为409 m~2·g~(-1)和0.14 cm~3·g~(-1),其骨架n_(SiO_2)/n_(Al_2O_3)达到96.4。     

Synthesis of novel hierarchical ZSM-5 monoliths and their application in trichloroethylene removal

A self-supporting ZSM-5 monolith with a hierarchical porosity was prepared using polyurethane foam (PUF) as a structural template and a hydrothermal synthesis procedure. The synthesized monolith was characterized and investigated towards the adsorption and catalytic oxidation of trichloroethylene (TCE). Adsorption of TCE was studied gravimetrically and oxidation of TCE was studied using a vapor-phase down-flow reactor. Monolithic ZSM-5 displayed good sorption properties and completely oxidized TCE. Conversion levels of 50% and 90% were achieved at reduced temperatures (by ~50 ℃) when compared with the conversion temperatures obtained from the powder counterparts. Besides the activity of the monolith towards TCE adsorption and oxidation, it was stable and enhanced diffusion, thereby reducing pressure drops to a great extent owing to its hierarchical porous nature.