Offretite Zeolite Single Crystals Synthesized by Amphiphile-Templating Approach

Offretite zeolite synthesis in the presence of cetyltrimethylammonium bromide (CTABr) is reported. The offretite crystals were synthesized with a high crystallinity and hexagonal prismatic shape after only 72 h of hydrothermal treatment at 180 °C. The CTABr has dual-functions during the crystallization of offretite, viz. as structure-directing agent and as mesoporogen. The resulting offretite crystals, with a Si/Al ratio of 4.1, possess more acid sites than the conventional offretite due to their high crystallinity and hierarchical structure. The synthesized offretite is also more reactive than its conventional counterpart in the acylation of 2-methylfuran for biofuel production under non-microwave instant heating condition, giving 83.5% conversion with 100% selectivity to the desired product 2-acetyl-5-methylfuran. Hence, this amphiphile synthesis approach offers another cost-effective and alternative route for crystallizing zeolite materials that require expensive organic templates.     

多级孔Beta沸石合成研究进展

沸石分子筛是许多工业过程中不可缺少的催化剂。其中,Beta沸石因其具有三维大微孔结构而成为生产广泛并且具有重要工业意义的沸石材料之一。与传统微孔Beta沸石相比,多级孔Beta沸石具有更小的空间位阻,更高的传质效率等诸多优点,从而能减少其在作为催化剂时积碳的形成,从而延长催化剂的使用寿命,提高催化剂利用效率。本文以Beta沸石为代表,从“自下而上”（直接合成）和“自上而下”（后期修饰）两种策略详细地介绍了多级孔沸石合成的研究进展,对硬模板剂法、软模板剂法、无介孔模板剂法、脱铝法和脱硅法进行了全面的介绍,并简要介绍了多级孔Beta沸石的特点,最后总结了各种合成方法的优点及存在的问题并对其未来发展前景进行了展望。     

利用双模板剂的多级孔ZSM-11分子筛的合成、表征和催化性能

ZSM-11与ZSM-5分子筛具有相似的孔道结构,通常表现出相似的催化性能,但近年来的研究发现,ZSM-11分子筛在某些反应过程具有明显优于ZSM-5的催化性能,因而逐渐引起科研界和工业界的广泛重视.但受其微孔尺寸的限制,在使用过程中往往容易积碳,并导致快速失活.为此,向微孔体系引入介孔制备多级孔ZSM-11分子筛是一种规避上述问题的有效方式.我们研究组前期已对分子筛进行碱处理脱硅及在该体系中加入CTAB制备多级孔分子筛进行了系统研究.在此基础上本文通过改变介孔模板剂十六烷基三甲基溴化铵(CTAB)和微孔模板剂四丁基溴化铵(TBABr)的摩尔比(R),采用一步法制备了一系列多级孔ZSM-11分子筛材料,并通过多种表征手段对材料的性质进行了系统研究.随着R值的增加,广角XRD测试结果表明,产物的结晶度逐渐下降,同时小角XRD测试结果表明产物中逐渐产生有序介孔相; XRF测试结果表明,产物的总包硅铝比呈上升趋势; SEM表征结果表明,首先棒状纳米晶团聚体形貌的ZSM-11分子筛的晶粒尺寸逐渐降低,随后晶粒之间插入无定形样品,直至最终产物几乎完全为无定形材料构成; TEM图片与上述表征结果一致,样品初始晶格条纹清晰且晶粒边缘规整,随后晶粒边缘开始弯曲不平,接着晶体样品中开始产生有序介孔材料,最终几乎完全变为有序介孔材料.综合上述表征结果和相关文献可推测,该有序介孔材料为类MCM-41材料.另外,我们采用N2物理吸附对材料的织构性质进行了考察,发现随着R值增大,产物的微孔减少,介孔增多.然而TEM结果表明,在类MCM-41产生之前,样品中介孔的增多并非来源于晶内孔,而是来源于晶粒之间的堆积孔,这是由于在合成过程中CTAB胶束嵌入ZSM-11的晶粒之间所导致.合成体系的碱度对产物的物化性质和织构性质也起了非常重要的作用.我们将这个体系与NaOH+CTAB对分子筛进行脱硅后处理体系进行了对比,发现虽然前者只能产生晶间孔而后者可产生晶内孔,但碱度对两者的作用相似,即降低碱度均可导致类MCM-41有序介孔相的产生.此外,还通过NH3-TPD和Py-IR技术对材料的酸性进行了考察.基于上述研究结果,提出了多级孔ZSM-11分子筛的形成机理.随着R值的变化,CTAB分别起了覆盖效应、胶束效应和模板效应.这些效应在合成多级孔ZSM-11分子筛过程中相互协同,同时又与TBABr的结构导向效应相互竞争,进而影响合成产物的孔结构、形貌、酸性以及用于二甲醚和苯烷基化的催化性能.     

Dual template synthesis of a highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction

The dual template synthesis of zeolite SSZ-13 by use of trimethyl-adamantanammonium hydroxide and a diquaternary-ammonium mesoporogen induces considerable mesoporosity without impeding zeolite microporosity. The strongly improved accessibility of Br?nsted sites in mesoporous SSZ-13 increases its stability during application as an acid catalyst in the methanol-to-olefins reaction.     

具有多级孔结构的NH4-β沸石的直接合成及其性能

以非离子表面活性剂壬基酚聚氧乙烯醚(TX-15)为模板, 设计氟化铵作为矿化剂, 在近中性条件下直接合成了具有微孔-介孔复合孔道的铵型β沸石. 合成样品采用粉末X射线衍射(PXRD), 高分辨扫描电子显微镜(SEM), 微分热重(DTG)以及氨程序升温脱附(NH3-TPD)等手段进行了表征. 结果表明, 氟离子及非离子表面活性剂的加入对沸石的孔结构、酸性质均起到了一定的调变作用.该沸石具有发达的呈梯级分布的多级孔结构, 孔容高达0.67 cm3·g-1, 且具有较强的Bronsted酸和适度分布的Lewis酸, 大大改善了反应物和产物分子的扩散和反应性能. 在混合C4烃的催化裂解反应中, 该沸石与传统方法合成的β沸石相比, 其转化率提高了约15%, 烯烃(乙烯和丙烯)产率提高了近10%, 芳烃(苯和甲苯)产率提高了3%.     

Micron-Sized Zeolite Beta Single Crystals Featuring Intracrystal Interconnected Ordered Macro-Meso-Microporosity Displaying Superior Catalytic Performance

Zeolite Beta single crystals with intracrystalline hierarchical porosity at macro-, meso-, and micro-length scales can effectively overcome the diffusion limitations in the conversion of bulky molecules. However, the construction of large zeolite Beta single crystals with such porosity is a challenge. We report herein the synthesis of hierarchically ordered macro-mesoporous single-crystalline zeolite Beta (OMMS-Beta) with a rare micron-scale crystal size by an in situ bottom-up confined zeolite crystallization strategy. The fully interconnected intracrystalline macro-meso-microporous hierarchy and the micron-sized single-crystalline nature of OMMS-Beta lead to improved accessibility to active sites and outstanding (hydro)thermal stability. Higher catalytic performances in gas-phase and liquid-phase acid-catalyzed reactions involving bulky molecules are obtained compared to commercial Beta and nanosized Beta zeolites. The strategy has been extended to the synthesis of other zeolitic materials, including ZSM-5, TS-1, and SAPO-34.     

Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design

The introduction of synthetic zeolites has led to a paradigm shift in catalysis, separations, and adsorption processes, due to their unique properties such as crystallinity, high-surface area, acidity, ion-exchange capacity, and shape-selective character. However, the sole presence of micropores in these materials often imposes intracrystalline diffusion limitations, rendering low utilisation of the zeolite active volume in catalysed reactions. This critical review examines recent advances in the rapidly evolving area of zeolites with improved accessibility and molecular transport. Strategies to enhance catalyst effectiveness essentially comprise the synthesis of zeolites with wide pores and/or with short diffusion length. Available approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality for practical implementation, establishing a firm link between the properties of the resulting materials and the catalytic function. We particularly dwell on the exciting field of hierarchical zeolites, which couple in a single material the catalytic power of micropores and the facilitated access and improved transport consequence of a complementary mesopore network. The carbon templating and desilication routes as examples of bottom-up and top-down methods, respectively, are reviewed in more detail to illustrate the benefits of hierarchical zeolites. Despite encircling the zeolite field, this review stimulates intuition into the design of related porous solids (116 references).     

Inorganic molecular sieves: Preparation,modification and industrial application in catalytic processes

The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shape selectivity, but also on the flexibility of their chemical composition. Modification of the zeolite framework composition results in materials with acidic, basic or redox properties, whereas multifunctional catalysts can be obtained by introducing metals by ion exchange or impregnation procedures, that can catalyze hydrogenation–dehydrogenation reactions, and the number of commercial applications of zeolite based catalysts is continuously expanding.In this review we discuss determinant issues for the development of zeolite based catalysts, going from zeolite catalyst preparation up to their industrial application. Concerning the synthesis of microporous materials we present some of the new trends moving into larger pore structures or into organic free synthesis media procedures, thanks to the incorporation of novel organic templates or alternative framework elements, and to the use of high-throughput synthesis methods. Post-synthesis zeolite modification and final catalyst conformation for industrial use are briefly discussed.In a last section we give a thorough overview on the application of zeolites in industrial processes. Some of them are well established mature technologies, such as fluid catalytic cracking, hydrocracking or aromatics alkylation. Although the number of zeolite structures commercially used as heterogeneous catalysts in these fields is limited, the development of new catalysts is a continuous challenge due to the need for processing heavier feeds or for increasing the quality of the products. The application of zeolite based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties. Finally, biomass conversion and selective catalytic reduction for conversion of NOx are two active research fields, highlighting the interest in these potential industrial applications.     

多级孔钛硅分子筛的制备及应用进展

以钛硅分子筛(TS-1)为催化剂的选择性催化氧化工艺具有反应条件温和、产物选择性高及环境污染小等特点,促进了烃类催化氧化反应的绿色化发展.但常规TS-1分子筛狭窄的孔道限制了其在大分子催化氧化反应中的应用.多级孔TS-1分子筛为包含不同尺度的孔道结构的晶体沸石,兼具微孔分子筛晶体优异的水热稳定性和介孔材料优异的扩散传输性能,因此其受到国内外众多专家学者的广泛关注.多级孔TS-1分子筛的制备方法很多,主要有直接合成法和后处理法,其中直接合成法包括硬模板法、软模板法和自组装法,而后处理制备主要为碱处理法.我们在对多级孔TS-1分子筛制备方法进行归纳总结的基础上,探讨不同制备方法对分子筛中钛硅物种分布、孔道结构及催化烃类选择性氧化反应性能的影响.结合目前TS-1分子筛应用现状,对其未来发展进行展望.     

Microwave‐Assisted Solvent‐Free Synthesis of Ipsapirone

The currently applied synthetic methods of serotonin receptor ligands belonging to the group of long‐chain arylpiperazines, including ipsapirone, require the use of toxic solvents and comprise numerous synthetic steps. Moreover, the reaction yield does not exceed 60% in the majority of cases. These factors lead to an increased energy consumption and negatively impact the environment. This paper describes a more environmentally friendly method of ipsapirone synthesis that we decided to use. Ipsapirone was obtained in two different methods. The first method involved N‐alkylation of bromobutyl saccharin with 1‐(2‐pyrimidyl)piperazine dihydrochloride, while the second was a one‐pot method. Neither of these requires the use of toxic and expensive solvents. A shortened synthesis time, not exceeding 10 min due to the use of microwave radiation, is also another advantage of these methods. The yield of the final product, ipsapirone, was 85% and 67% in the first and the second method, respectively. We also attempted to obtain ipsapirone using saccharin and arylpiperazine salt (method III) as starting materials, but to no avail in the tested conditions. As described herein, the green chemistry method for ipsapirone synthesis is rapid, cost‐effective, and environment friendly.     

Facile Synthesis of Hierarchical Nanosized Single-Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single-crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8-rings), AEL (10-rings), AFI (12-rings), and -CLO (20-rings) topologies, ranging from small to extra-large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time-dependent study revealed a non-classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

干胶法合成分子筛

相对于传统的水热合成法,干胶法(dry gel conversion,DGC)合成分子筛具有产量高、废液量少等优势。本文综述了近十年来DGC合成分子筛的研究进展。以水为线索,总结了外加水和固有水(指原料干胶所含的水)在DGC中对分子筛的生长、晶相的转换与物化性质的影响,论述了在DGC条件下分子筛的生长过程和晶化机理,介绍了DGC在介孔-微孔复合分子筛、分子筛膜、单块材料等新型分子筛材料合成中的一些实例。     

One-step synthesis of hierarchical zeolite beta via network formation of uniform nanocrystals

A hierarchical mesoporous network of zeolite beta with very high micropore as well as mesopore volume was synthesized without the need of a porogen at near 100% yield in the form of easily retrievable micrometer-sized particles. This was achieved by a dense-gel synthesis utilizing steam-assisted conversion (SAC) to induce a burst of nucleation. During the first phase of the synthesis, individual, evenly sized zeolite beta nanoparticles are formed that subsequently condense into a porous network displaying uniform mesopores. The final product consists of hierarchical self-sustaining macroscopic zeolite aggregates assembled from 20 nm crystalline domains of zeolite beta. The small size of the zeolite crystals in the resulting materials gives rise to mesopores with dominant pore sizes of about 13 nm. Large surface areas between 630 and 750 m(2)/g and total pore volumes up to 0.9 mL/g were obtained without sacrificing the microporosity (usually larger than 0.20 mL/g). Crystallization conditions were optimized for different Si/Al ratios between 10 and 33. A complete conversion into hierarchical zeolite beta was achieved in only a few hours at 170-180 °C if the amount of water present during the steam-assisted conversion was adequately adjusted. This dense gel steam conversion process proves to be a highly efficient strategy for fabricating hierarchical zeolite beta networks in a single step.     

多级孔ZSM-5分子筛的制备及其在炼油领域中的应用

多级孔ZSM-5分子筛结合了微孔分子筛可调变的酸性、良好的水热稳定性以及介孔材料优异的传质扩散性能,在催化领域有着广阔的应用前景.我们综述了近年来多级孔ZSM-5分子筛的研究进展,重点概述了多级孔ZSM-5分子筛的不同制备方法,包括后处理法、硬模板法和软模板法等,同时介绍了多级孔ZSM-5分子筛在炼油领域的应用研究,并在上述基础上对多级孔ZSM-5分子筛的研究趋势进行了展望.     

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L⁻¹, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.     

Facile Synthesis of Hierarchical Nanosized Single‐Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single‐crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8‐rings), AEL (10‐rings), AFI (12‐rings), and ‐CLO (20‐rings) topologies, ranging from small to extra‐large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time‐dependent study revealed a non‐classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

使用四乙基氢氧化铵作为有机模板剂和常规硅铝源直接合成SSZ-13沸石分子筛

使用四乙基氢氧化铵作为有机模板剂,利用常规铝源和硅源而不需要高硅Y沸石作为起始原料,同时加入适量的沸石晶种直接合成了SSZ-13沸石分子筛.所合成的沸石产物结晶度好,具有良好的水热稳定性,并在氨选择性催化还原(NH₃-SCR)反应中显示出优异的催化性能,为其在工业上广泛应用提供了可能.     

单一模板线性多胺一步合成多级孔ZSM-5沸石微球

线性多胺模板剂(二乙烯三胺(DETA)、三乙烯四胺(TETA)、四乙烯五胺(TEPA))作为单一模板合成了均匀的10-15 μm的多级孔沸石ZSM-5微球. 实验发现, 在水热过程中, 50 nm纳米的沸石晶体粒子自发地堆积成微球, 并且这些微球具有较大的介孔体积, 在傅-克烷基化反应中具有高的催化活性. 同时,我们发现线性多胺起到了模板剂和空隙填充剂的多重功能,这点明显不同于以前我们报道的线性二胺作为模板剂在合成ZSM-5沸石时,主要是起模板剂的作用.     

基于柠檬酸的石墨烯量子点的制备及其应用

石墨烯量子点（GQDs）是一种新型碳基准零维材料,不但具有石墨烯的独特平面结构,同时具备碳点的量子限制效应和边界效应。GQDs具有独特的光学性质、低毒性、高荧光稳定性和高生物相容性,被广泛应用于检测、传感、催化、细胞成像、药物递送和污染治理等领域。GQDs的合成分为自上而下法和自下而上法,前者将大尺寸的石墨烯、石墨、碳材料切割成纳米级的量子点,后者使用不同的前驱体,通过水热法、热裂解法等方法合成石墨烯量子点。柠檬酸（CA）是一种重要的有机酸,室温下是白色结晶状粉末,是自下而上法合成GQDs的一种常用前驱体,近年来有许多关于以CA为前驱体合成不同GQDs的研究,以CA为前驱体合成的GQDs（CA-GQDs）在生物医药、荧光检测、成像等领域均有应用,具有较好的应用前景。对近年来基于CA的合成方法和具体应用进行了总结和回顾,旨在将现有CA-GQDs的相关成果尽可能汇总和展现,以对相关领域研究工作者提供一定参考,并对未来CA-GQDs较有前景的研究方向进行了展望。     

Green polymer chemistry: new methods of polymer synthesis using renewable starting materials

The present article reviews the recent results reported mainly from our group on “green polymer chemistry”. Characteristic important aspects of green polymer chemistry include herein, typically (1) using renewable resources as starting materials for polymer production, and (2) employing green method for the polymer synthesis. As renewable starting materials, the following materials were employed; lactic acid, itaconic anhydride, renewable plant oils, and cardanol. Polymer production using these materials contributes to mitigate the carbon dioxide emission because of their “carbon neutral” nature. As green method, lipase enzyme was mainly used for polymerization catalyst, since lipase is a natural benign catalyst, showing a specific catalysis as well as recyclable character. Polymer synthesis from these materials and the catalyst provided various value-added functional polymers, demonstrating good examples of green polymer chemistry.