共查询到19条相似文献,搜索用时 176 毫秒
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用水热合成和铵交换法制备系列氢型丝光沸石(H-MOR),通过水热碱蚀与碱溶滤联合处理对H-MOR样品进行选择性脱硅和介孔改性.研究H-MOR骨架Si/Al比对改性沸石的介孔结构、酸性和水热稳定性的影响.N2吸附结果表明,碱处理沸石的介孔率随H-MOR硅铝比减少而增加;典型样品(n(Si) /n(Al) 9.43)具有附加介孔结构,介孔体积可达0.082 cm3/g,最可几孔径为4.6 nm;SEM观察显示,改性沸石的介孔结构源于脱硅产生的结构缺陷,晶内介孔呈无序分布;ICP和EDX分析证实,联合碱处理促进H-MOR晶体选择性脱硅(脱硅率均大于93.1%);水热稳定性和NH3-TPD数据表明,介孔改性丝光沸石较好地保持了前体的结晶性和水热稳定性,其酸性与对应H-MOR沸石相匹配.骨架硅铝比影响改性MOR沸石的介孔率,但与沸石脱硅率无相关性. 相似文献
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以丝光沸石分子筛为硅铝源,通过碱液处理和表面活性剂的自组装作用,水热条件下合成了MOR/MCM-41复合分子筛。通过XRD、SEM、TEM、N2吸附/脱附和水热稳定性处理等手段对合成的复合材料进行了表征。结果表明,复合材料不仅保留了原丝光沸石晶体的规则形貌,同时兼具微孔分子筛MOR和介孔分子筛MCM-41的特征,且介孔(20~30 nm)在微孔分子筛中较均匀地分布。水热处理测试结果表明,MOR/MCM-41复合分子筛具有较高的水热稳定性,水热处理100 h后介孔结构依然存在。 相似文献
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以硅酸钠溶胶和铝酸钠为硅、铝源,采用水热合成和离子交换法制备了质子型丝光沸石(H-MOR)。研究水热碱蚀与碱溶滤联合处理对H-MOR改性样品的介孔结构、晶体形貌、组成及酸性质的影响。结果表明:用初始浸渍液对H-MOR进行水热碱蚀,H-MOR骨架脱硅选择性高,晶体含有均一的筛状介孔;水热碱蚀与一次碱溶滤处理的样品具有尺度分布较窄的槽形介孔,沸石骨架硅铝比降低而介孔率增加;再度进行碱溶滤处理,沸石的最可几介孔尺寸和累计介孔体积进一步增大,而残留抽出物(无定形SiO2–Al2O3)的硅铝比为生成介孔丝光沸石晶相的5倍以上。联合碱处理的丝光沸石样品具有骨架脱硅选择性和介孔率高、介孔分布(4.4~5.7nm)可控的特性,其结晶度、固有微孔结构和酸性质退化程度较低。 相似文献
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《硅酸盐学报》2017,(7)
采用无机铁、硅原料合成不同组成的MFI型硅铁沸石。通过碱酸处理对质子化硅铁沸石进行介孔改性。用X射线衍射、Fourier变换红外光谱、紫外–可见光谱、N_2吸附、扫描电子显微镜和能量色散X射线谱表征沸石的晶体和孔结构性质,探究骨架Si/Fe摩尔比与晶内介孔率和Si、Fe脱除行为的关系。结果表明:合成的硅铁酸盐是结晶性好的Fe~(3+)同构取代MFI型沸石;系列改性硅铁沸石具有较高的结晶度保留率、脱硅选择性、介孔率及二级介孔分布特征。骨架Si/Fe比是影响沸石选择性脱硅和介孔形成的关键因素。起始Si/Fe比为60~120的改性沸石具有更高的介孔率及Si、Fe脱除效率。 相似文献
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丝光沸石是二甲醚羰基化反应的高活性催化剂,通过对其酸中心进行调控是进一步提高其催化性能的有效方法。采用不同浓度的草酸溶液对丝光沸石进行了酸处理,通过X射线粉末衍射、N2吸附-脱附、扫描电子显微镜、氨气-程序升温脱附、吡啶-红外等技术手段对草酸处理前后丝光沸石结构及酸中心的变化进行了表征。结果表明:草酸处理对丝光沸石的相对结晶度、晶型影响较小,但能够通过“蚀刻”或络合作用有效脱除部分酸中心,尤其是优先脱除十二元环孔道中的酸中心,同时能够在颗粒中制造出部分介孔、提升丝光沸石的介孔孔容。适当浓度的草酸处理能够有效提高丝光沸石的二甲醚羰基化反应活性,二甲醚转化率明显升高,乙酸甲酯选择性仅略有下降。草酸浓度过高时会脱除部分羰基化反应的活性中心,从而导致催化活性的降低。为丝光沸石的酸中心调控及其二甲醚羰基化反应活性的提高提供了简单有效的方法。 相似文献
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通过水热合成及铵交换制备不同硅铝比的氢型沸石H-ZSM-22;用碱、酸介质对H-ZSM-22样品进行介孔改性。研究起始沸石硅铝比对改性沸石相对结晶度、介孔结构、晶貌和产率的影响。N2吸附-脱附和XRD分析表明,改性沸石兼有结晶性的微孔-介孔结构;随着起始沸石n(Si)∶n(Al)由31.7增至43.2,改性沸石介孔体积出现极大值而结晶度保留率和产率呈相反的变化趋势;典型样品[n(Si)∶n(Al)=37.0]的介孔体积高达0.44cm3/g,结晶度保留率和相对产率分别为56.0%、44.4%。SEM观察显示,改性沸石的附加介孔结构主要源于H-ZSM-22骨架脱硅、脱铝产生的结构缺陷。 相似文献
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Yingjie Jin Yongdan LiShanlin Zhao Zhenbo LvQiao Wang Xianling LiuLei Wang 《Microporous and mesoporous materials》2012,147(1):259-266
An approach, which involved perturbations of synthesis conditions in crystallization temperature and organic template composition, has been proposed for derivation of mesopores from bulk structural defects formed in mordenite (MOR) phases, based on the character of intrinsic crystal defects and tensional distortions of two compressed 8-membered rings in MOR framework. Consequently, hierarchically porous materials with MOR structures were prepared by varying temperature synthesis and using ternary organic micelles templates. The synthesized materials were characterized by powder X-ray diffraction, nitrogen adsorption at 77 K and transmission electron microscopy. These crystalline materials combined the advantages of both mordenites with the micropore system and mesoporous materials by featuring an additional intracrystalline mesopore system in MOR single crystals, resulting in a hierarchical pore distribution in range of 1.7-80.0 nm together with the significant specific surface areas. In particular, individual crystal morphologies of typical mesoporous MOR materials showed the defect-rich structures responding essentially to the mesoporosity; the mesoporous materials were substantiated matchable well to normal mordenites in acid capacity and acid strength distribution. Furthermore, several factors acting on intracrystalline mesopore formation were elucidated for explicating the perturbation synthesis approach, and whole reaction routes for synthesizing different solid products under related crystallization conditions were summarized coupling with a demonstration of part TEM micrographs. The overall results suggested that the investigative approach of perturbation imposed on crystal growth provides an alternative route for direct hydrothermal synthesis of mesoporous zeolite materials and implied that bulk structural defects within single crystals lead to the formation of intracrystalline mesopores in various sizes. 相似文献
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Maosheng Xia Yinshan Jiang Fangfei Li Mengmeng Sun Bing Xue 《Journal of Porous Materials》2010,17(2):139-144
Mesoporous material with dual mesoporous size distribution had been synthesized with montmorillonite as precursor. The materials
exhibited two kinds of mesopores: one is mesopore in interlayers of montmorillonite with mean sizes of 2.9 nm, the other is
mesopore out of layers of montmorillonite with mean sizes of 3.9 nm. With the increasing of pH values (8.0–11.0), the specific
surface area and pore volume of two kinds of mesopores changed regularly. The samples were characterized by XRD, TEM and Nitrogen
adsorption/desorption isotherms. The results indicated that higher pH benefits the synthesis of mesoporous montmorillonite
with smaller pore and the TOT of montmorillonite had been present as porous wall. 相似文献
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Guoqiang Song Hongtao Liu Fuxiang Li Zhiping Lv Jianwei Xue 《Journal of Porous Materials》2014,21(6):1101-1111
An ordered mesoporous LTA zeolites (MLTA) have been synthesized in presence of the bridged polysilsesquioxane monomer (BS-1) as mesoporogen. The relatively well-defined small-angle X-ray diffraction peaks and nitrogen sorption isotherms with narrow pore size distribution centered at around 2.2 nm both indicated the presence of uniformly mesopores in MLTA samples. The scanning electron microscopy and transmission electron microscopy observations further confirmed that the uniform and partially interconnected intracrystal mesopores were randomly distributed throughout the globular particles with rugged surfaces. Interestingly, removal of the BS-1 resulted in uniform mesopore diameters that are nearly consistent with the molecular size of BS-1 (1.8 nm). 29Si MAS NMR revealed that the BS-1 was linked to MLTA zeolite crystal surface through 2 Si–O bonds and 3 Si–O bonds before calcinations. Nitrogen sorption analysis showed that the mesoporosity in MLTA samples could be adjusted by adding different amounts of BS-1 in starting gels. Relative to conventional mesoporous materials, one obvious feature of MLTA is that the resultant mesopores were structured by the bridged polysilsesquioxane monomer instead of commercial polymers or micelles, which broad the routes in synthesizing of various mesoporous materials with controllable pore size distribution, adjustable mesopore volume, and large surface area. 相似文献
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Y分子筛/介孔Al-SBA-15复合材料与脱铝Y分子筛的表征和重油加氢裂化性能 总被引:1,自引:1,他引:0
采用两步法和水热-化学方法制备了具有高水热稳定性的Y分子筛/介孔Al-SBA-15复合材料和含有介孔的脱铝Y分子筛,用浸渍法制备了加氢裂化催化剂,并利用XRD、N2 吸附、SEM、XRF和TEM等分析手段对Y分子筛/介孔Al-SBA-15复合材料、含有介孔的脱铝Y分子筛及其催化剂的物化性质进行了对比分析。相同条件下催化剂的重油加氢裂化性能对比评价结果表明,以Y分子筛/介孔Al-SBA-15复合材料为载体的加氢裂化催化剂的中间馏分油收率和中油选择性高达66.21%和84.5%,比以脱铝Y分子筛为载体的催化剂分别提高了5.68%和5.7%。 相似文献
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高稳定性介孔分子筛的合成与表征 总被引:1,自引:0,他引:1
以天然黏土和硅酸钠为原料、十六烷基三甲基溴化铵为模板剂,水热法合成了有序性好的高稳定性介孔分子筛.用粉末X射线衍射、透射电镜、Fourier变换红外光谱和比表面积孔径分析等方法对所合成的介孔分子筛进行了表征.结果表明:所合成的介孔分子筛的比表面积大于550m2/g,平均孔径为2.72nm.样品经850℃焙烧3 h,100℃水热处理10 d,介孔分子筛的介孔结构没有被破坏,并且热处理使孔发生收缩,比表面积减小,水热处理使介孔的有序性变得更好,天然黏土为原料提高了介孔分子筛的水热稳定性. 相似文献
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以非离子表面活性剂[聚环氧乙烷(PEO)-聚环氧丙烷(PPO)-聚环氧乙烷三嵌段共聚物,P123]和阳离子聚电解质(聚二甲基二烯丙基氯化铵,PAC)形成的复合物胶束为模板,合成了具有球形形貌的介孔二氧化硅KIT-6介观单晶微球。通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、氮气物理吸附和热重分析(TGA)等手段对合成材料的形貌及孔结构进行了表征分析。结果表明,以有机复合物胶束为模板合成出的介孔KIT-6二氧化硅材料具有较规整的球形形貌,颗粒直径为2~3 μm,具有较大的比表面积和孔体积(747 m2/g和1.3 cm3/g),介孔孔径为8.5 nm,且在整个颗粒内部介孔保持高度的有序排列。由于长链聚电解质PAC与硅源有着较强相互作用,样品可以在较高水热温度下(160 ℃)合成,有利于提升介观结构的稳定性。该合成方法对于介孔二氧化硅KIT-6单晶微球的合成及其在催化及吸附分离等领域的应用具有一定的启发意义。 相似文献
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Three types of ordered mesoporous carbon materials with different pore characteristics have been synthesized via different routes. Whatever the synthesis route was, triblock copolymer was employed as both a carbon precursor and a structure-directing agent. The relationship between the capacitances of carbon electrodes and their pore characteristics was elucidated in detail. The material C-P exhibits the lowest resistance and highest specific capacitance value of exceeding 170 F/g among these carbon materials, which can be due to not only high surface area but also its appropriate pore size distribution. In addition, the noteworthy is that the maintenance of specific capacitance with increasing current load for each sample is better than that for general activated carbons, where larger mesopores and high mesopore fraction play important roles in the rate capability. 相似文献
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Toshihide Horikawa Tomoki Sekida Jun’ichi Hayashi Masahiro Katoh Duong D. Do 《Carbon》2011,49(2):416-424
A new model is proposed to describe the adsorption and desorption branches of water adsorption in carefully synthesized mesoporous carbon materials. This model is an extension of a previous adsorption–desorption model proposed by Do et al. We prepared mesoporous resorcinol–formaldehyde carbon cryogels (RFCCs) by sol–gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution, followed by drying with freeze-drying and then carbonizing the RF cryogels at a high temperature under a nitrogen atmosphere. The resulting carbon materials have different surface and pore properties, which are valuable in the study of their effects on water vapor adsorption and desorption on RFCCs. The experimental data were used to test the model, and we have found that the model describes reasonably well all the data. We have also observed some interesting, but not unexpected, results in the analysis: the water cluster size in mesopore is larger than that in micropore, and the hysteresis loop of adsorption–desorption in mesopores is greater than that in micropores. 相似文献