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利用浸渍提拉方法,在平均孔径500 nm的管状a-Al2O3陶瓷管载体上成功制备了无缺陷的Beta/碳纳米复合分子筛膜. 通过室温下单组分气体渗透实验,发现当Beta分子筛在聚糠醇/丙酮溶液中的含量逐渐加大时,复合膜的气体分离因数略有增加,同时气体渗透通量明显加大. 经优化后氢气渗透通量比纯碳膜增加了一个数量级,说明Beta分子筛起到了加快气体渗透通量的作用. 由SEM照片可以发现,随着Beta分子筛含量的增加,制备的纳米复合膜的厚度由平均14 mm减少到7 mm左右,从而减少了气体渗透的阻力.结合实验数据,探讨了沸石分子筛/碳复合膜气体渗透路径. 相似文献
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Beta沸石分子筛是一种在化工领域应用较为广泛的催化材料。目前制备出的Beta沸石分子筛的粒径大多数是微米级,纳米级的制备研究相对薄弱。针对于此,采用单模板剂(TEAOH)或添加第二模板剂,主要有聚乙烯醇(PVA)、羧甲基纤维素钠(CMC)以及三乙醇胺(TEOA)来制备纳米级Beta沸石分子筛,探索一条适合工业大规模生产的简单可行的制备路径。 相似文献
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合成了纳米Beta沸石,并采用X射线衍射(XRD)、透射电镜(TEM)、比表面(BET)、程序升温脱附(NH3-TPD)以及吡啶-红外光谱(Py-IR)等方法对其结构和酸性进行了表征。比较了纳米Beta和常规大晶粒Beta沸石的催化性能,对纳米Beta沸石催化烷基化的关键参数进行了优化。结果表明:在硅铝物质的量比为25~30时,所合成的纳米Beta沸石具有较高的结晶度,晶粒尺寸在20 nm左右。同常规Beta沸石相比,纳米Beta沸石具有更大的BET比表面积和孔容,其比表面积可达600 m2/g,总孔容达0.42 cm3/g,介孔和大孔贡献超过50%。纳米Beta沸石具有较高的总酸量和B酸含量。作为苯和丙烯的烷基化催化剂,纳米Beta沸石具有更好的反应稳定性和选择性。在苯烯比3.0,反应温度150~160℃的条件下,异丙苯选择性可达89%,杂质正丙苯含量可降到极低水平。在工业试验中,纳米Beta沸石也表现出良好的综合性能,催化剂的稳定性和选择性优于同类Beta沸石催化剂。 相似文献
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纳米催化技术的应用进展 总被引:6,自引:0,他引:6
概述了纳米微粒的制备技术;介绍了纳米催化技术,包括碳纳米管催化、纳米金属(簇)催化、纳米金属氧化物催化、纳米沸石组装与催化以及金属配合物/分子筛复合催化材料催化、纳米粒子/聚合物复合材料催化、无机/有机纳米复合膜材料催化等;对未来纳米催化技术发展提出建议:改进现有的制备方法,探索开发纳米材料制备新技术,研究纳米材料的评价与表征方法,深入开展基础理论研究,以及扩大各研究院校与产业部门间的科技合作。 相似文献
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高分子气体分离膜具有价格低和易加工等优点,但存在气体分离性能难以满足工业要求,以及耐老化性能和结构稳定性差等问题。炭分子筛膜不仅具有高力学性能,高耐热、耐化学腐蚀性能,而且存在适合气体传递的路径、对气体分子亲和性好的杂原子结构,以及分子辨识能力强的孔尺寸,表现出优异的气体分离性能,因而受到广泛的关注,被认为是最具应用前景的气体分离膜。6FDA型聚酰亚胺不仅具有较大的刚性和受限制的构象,且自由体积较大、分子结构可调、成孔性好和残炭量高,制备的炭分子筛膜的气体分离性能优于其他前体,受到学术界和工业部门的青睐。本文主要介绍了炭分子筛膜前体的结构设计原理,在热解过程中的炭化机理和微观结构的控制,炭结构对气体分离性能的影响,气体在膜中的传递机理,以及由6FDA型聚酰亚胺制备的炭分子筛膜在气体分离中的应用。结合科研实际,提出了6FDA型聚酰亚胺炭分子筛膜结构设计和制备的想法,为未来炭分子筛膜在气体分离中应用提供新的思路。 相似文献
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分子筛膜不但具有分子筛单体独特均一的孔道结构及可调变等性质,并且具有机械强度大、热稳定性高、耐化学药剂能力强等特点,在气体分离、催化反应及溶剂提纯领域具有很好的应用前景,成为近年来研究的热点之一。在合成分子筛膜的过程中,氟离子可以代替氢氧根离子作为矿化剂,在近中性体系下合成出分子筛膜;并且,氟离子在某些合成反应中可以起到结构导向剂的作用,代替价格昂贵的有机模板剂;对于特定类型的分子筛膜,在含氟体系下合成具有更优异的性能。总结了含氟体系下合成的不同类型的分子筛膜的研究现状和最新进展,在此基础上对氟离子在分子筛膜的合成中的作用机理进行了探讨。 相似文献
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采用二次生长法,通过在晶种涂覆液中添加硅溶胶,在不锈钢丝网载体上制备牢固的Beta分子筛膜,系统考察晶种层中硅溶胶含量、晶种涂覆量、结晶温度和结晶时间对分子筛膜生长的影响。实验中发现,硅溶胶的存在可以增加涂覆层的牢固度,促进Beta分子筛膜的生长;硅溶胶既具有黏合剂的作用又可以补充硅源。当涂覆量较低时,无法得到一个完整的分子筛膜,分子筛膜负载量随着涂覆量的增加而增加;当结晶温度升至一定程度,分子筛膜组成不再单一。晶化过程中伴随着晶种的脱落和溶解。制备的Beta分子筛膜对N2O催化分解具有良好的催化活性。 相似文献
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实现CH4-N2高效分离能够极大地推动常规天然气和非常规天然气这一类绿色低碳能源的利用,分子筛基吸附剂和膜材料具有优良的气体分离特性,而且对CH4-N2的分离颇具应用潜力。本文从对N2具有优先选择性吸附的N2/CH4分离(高浓度CH4纯化脱氮)和对CH4具有优先选择性吸附的CH4/N2分离(低浓度CH4富集脱氮)两方面综述了国内外分子筛吸附剂及分子筛膜的研究进展。详细地分析了分子筛骨架和平衡阳离子与其CH4-N2吸附分离性能之间的构效关系,并结合本文作者课题组的工作,提出了电中性(近中性)骨架分子筛对CH4-N2分离具有较好的分离效果。最后总结和展望了CH4-N2分离用分子筛吸附剂及分子筛膜的未来发展趋势。 相似文献
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Weimin Zhang Bo Qin Wenxi Li Kaige Hou Yanze Du Jinghong Ma Ruifeng Li 《化学工程与技术》2020,43(11):2224-2232
A hierarchical Beta zeolite has been successfully mass-prepared hydrothermally and dynamically in a pilot-scale autoclave by an economical and simple process with low-cost raw materials. The characterization results indicated that the pilot-scale hierarchical Beta zeolite has the same textural, structural, and acidic properties like the bench-scale sample. Moreover, the catalyst composed of the pilot-scale hierarchical H-Beta zeolite showed higher activity and selectivity to the middle distillate than that containing microporous Beta zeolite in catalytic hydrocracking of vacuum gas oil (VGO) evaluated by an industrial pilot installation in running of 3000 h, due to the increased accessibility and the reduction of diffusion constraint of large molecules to acid sites in the Beta zeolite framework. 相似文献
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Dariush Bastani Nazila Esmaeili Mahdieh Asadollahi 《Journal of Industrial and Engineering Chemistry》2013,19(2):375-393
Polymeric membrane technology has received extensive attention in the field of gas separation, recently. However, the tradeoff between permeability and selectivity is one of the biggest problems faced by pure polymer membranes, which greatly limits their further application in the chemical and petrochemical industries. To enhance gas separation performances, recent works have focused on improving polymeric membranes selectivity and permeability by fabricating mixed matrix membranes (MMMs). Inorganic zeolite materials distributed in the organic polymer matrix enhance the separation performance of the membranes well beyond the intrinsic properties of the polymer matrix. This concept combines the advantages of both components: high selectivity of zeolite molecular sieve, and mechanical integrity as well as economical processability of the polymeric materials. In this paper gas permeation mechanism through polymeric and zeolitic membranes, material selection for MMMs and their interaction with each other were reviewed. Also, interfacial morphology between zeolite and polymer in MMMs and modification methods of this interfacial region were discussed. In addition, the effect of different parameters such as zeolite loading, zeolite pore size, zeolite particle size, etc. on gas permeation tests through MMMs was critically reviewed. 相似文献
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Yuping Li Wei Zhang Xiaoli Wang Ying Zhang Tao Dou Kechang Xie 《Journal of Porous Materials》2008,15(2):133-138
A Beta/MCM-41 composite has been synthesized with a new method by using well-crystallized zeolite Beta as silica and aluminum
source. The prepared composite was characterized by XRD, FTIR, N2 adsorption/desorption at 77 K, FE-SEM, DTG, 29Si MAS NMR spectral techniques. It was shown that the composite consisted of a highly ordered mesoporous MCM-41 phase and
a zeolite Beta phase. Its hexagonal mesoporous structure was still retained after statically treated for 120 h in boiling
water. In contrast, the structure of generally synthesized Al-MCM-41 nearly completely collapsed. This might be attributed
to the assembly of the dissolved fragments such as the first and/or secondary structural units of zeolite Beta into the mesoporous
structure around surfactant micelles. This is supported by the catalytic result that the prepared composite showed higher
activity and selectivity for medium fraction in hydrocracking of Daqing vacuum residue than the parent zeolite Beta, the Al-MCM-41
as well as the mechanical mixture of these two materials. 相似文献
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为了实现石脑油的高效资源化利用,需开发石脑油高效分离技术。简述了石脑油正/异构烷烃吸附分离原理及分离技术现状,介绍了新型吸附剂材料的研发进展,包括金属有机框架材料(MOFs)、沸石咪唑框架材料(ZIFs)、碳分子筛(CMS)、中空沸石分子筛等,阐述了新型吸附材料对正构烷烃的分离效果和分离机理,探讨了新型吸附剂、膜分离技术和吸附-膜分离耦合技术用于分离石脑油中正/异构烷烃的可行性,展望了新型正/异构烷烃分离技术,以期为石脑油高效资源化利用提供新途径。 相似文献
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A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation. 相似文献
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