共查询到19条相似文献,搜索用时 171 毫秒
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介绍了用于催化甲醇制烯烃的SAPO-34分子筛合成的研究近况。SAPO-34分子筛的合成过程是影响其晶粒尺寸、酸性强弱等物化性能的重要因素, 因而是影响其催化性能的关键因素。本文详细叙述了原料配比及其种类、模板剂、F-等合成因素对SAPO-34分子筛物化性能及其MTO反应催化性能的影响。针对SAPO-34合成及其催化性能优化的新技术, 综述了SAPO-34分子筛的金属改性及其超声波、微波辅助合成的特点和效果, 指出通过研发新的模板剂及其助剂、改性或制备新工艺进而改善分子筛的酸性、提高其烯烃选择性、延长催化反应寿命、降低合成成本是SAPO-34今后研发的重要方向。 相似文献
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用XRD、SEM、N2物理吸附、XRF、ICP-AES以及NH3-TPD、FT-IR、固体NMR和固定床甲醇制烯烃技术(MTO)反应评价等表征手段,研究了草酸溶液处理对SAPO-34分子筛的改性作用。结果表明,用草酸溶液对SAPO-34分子筛进行后处理可以通过刻蚀骨架在晶体中产生大孔,调变孔道结构,改善微孔扩散性能;选择性地降低分子筛的骨架硅含量,从而降低分子筛的酸强度和酸中心密度。将改性前后的分子筛应用于MTO反应中。评价结果表明,适度的酸处理能够在保证分子筛收率和乙烯、丙烯选择性的前提下,明显提高催化剂的单程寿命。草酸溶液处理是一种值得研究的SAPO-34分子筛后处理改性方法和MTO催化剂制备手段。 相似文献
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为制备性能更加优异的甲醇制烯烃(MTO)催化剂及进一步探究多级孔道对MTO催化反应的影响,采用柠檬酸溶液(CA)运用后处理方法对复合分子筛进行刻蚀,成功制备了具有多级孔道结构的ZSM-5/SAPO-34复合分子筛(CA-Z-S)。对复合分子筛的晶相、骨架、孔结构等理化性质进行了表征;将复合分子筛用于催化MTO反应,考察了复合分子筛的催化性能。表征结果表明,使用CA处理对ZSM-5/SAPO-34复合分子筛的形貌、结构会产生影响,使CA-Z-S具有更紧密的复合结构、适量的弱酸中心和多级孔道复合结构。催化测试结果表明,甲醇转化率达到100%时,CA-Z-S的寿命为1 200 min,较SAPO-34提高79%,较ZSM-5/SAPO-34提高30%;CA-Z-S对轻烯烃的选择性达到90.5%,较SAPO-34提高约3.7%。研究结果表明,利用CA对复合分子筛进行后处理,有利于复合分子筛催化MTO反应性能的提升。 相似文献
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采用Na OH溶液处理法制备了介孔ZSM-5分子筛。采用包埋法合成了ZSM-5/SAPO-34复合介孔分子筛,并采用X射线衍射图谱(XRD)、电子扫描电镜(SEM)、氮吸附进行分析,在固定床反应器中进行了甲醇芳构化反应。研究结果表明,ZSM-5/SAPO-34复合分子筛孔径呈微孔和介孔多级孔分布,孔径和孔容均高于ZSM-5分子筛。当ZSM-5与SAPO-34分子筛的质量比为1∶2时,ZSM-5/SAPO-34复合分子筛具有较好的芳构化活性。在反应温度为475℃、反应压力0.5 MPa、空速(LHSV)1.2 h-1条件下,BTX(苯、甲苯和二甲苯)的收率可达30.8%。 相似文献
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Yeon Hye Kwon Christine Kiang Emily Benjamin Phillip Crawford Sankar Nair Ramesh Bhave 《American Institute of Chemical Engineers》2017,63(2):761-769
Separation of the radioisotope 85Kr from 136Xe is an important target during used nuclear fuel recycling. We report a detailed study on the Kr and Xe adsorption, diffusion, and membrane permeation properties of the silicoaluminophosphate zeolite SAPO‐34. Adsorption and diffusion measurements on SAPO‐34 crystals indicate their potential for use in Kr‐Xe separation membranes, but also highlight competing effects of adsorption and diffusion selectivity. SAPO‐34 membranes are synthesized on α?alumina disk and tubular substrates via steam assisted conversion seeding and hydrothermal growth, and are characterized in detail. Membrane transport measurements reveal that SAPO‐34 membranes can separate Kr from Xe by molecular sieving, with Kr permeabilities around 50 Barrer and mixture selectivity of 25–30 for Kr at ambient or slight sub‐ambient conditions. The membrane transport characteristics are modeled by the Maxwell‐Stefan equations, whose predictions are in very good agreement with experiment and confirm the minimal competing effects of adsorption and diffusion. © 2016 American Institute of Chemical Engineers AIChE J, 63: 761–769, 2017 相似文献
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Niu Li Yanfeng Ma Wenbo Kong Naijia Guan Shouhe Xiang 《Microporous and mesoporous materials》2008,115(3):356-363
In the report, H3PO3 was used in place of H3PO4 as the phosphorus source to synthesize chabazite structure silicoaluminophosphate (SAPO) molecular sieves, SAPO-34, SAPO-44, and SAPO-47. It has been found that the directing effects of organic bases have met with a competition coming from the alternation of phosphorus source. For example, using H3PO4 as the phosphorus source, morpholine and triethylamine are two well known organic bases for directing the formation of SAPO-34. However, when H3PO3 or the mixtures of H3PO3 and H3PO4 are used as the phosphorus source, the directing product has changed from SAPO-34 to SAPO-47. Raman investigation has shown that there are some P(III) species in the intermediates for crystallizing SAPO-47. It means that chabazite structure SAPO molecular sieves are formed from a new route containing the transformation of P(III) to P(V) species. Meanwhile, the host–guest interactions between organic bases and SAPO framework have been studied and used to discuss why SAPO-47 is the preferable crystallizing product in the presence of H3PO3. Moreover, the competitive effect of phosphorus source H3PO3 on the synthesis of SAPO-47 has met its limitation when employing cyclohexylamine as the structure-directing agent. It has shown that no matter using H3PO3 or the mixture of H3PO3 and H3PO4 as the source of phosphorus, SAPO-44 is always the crystallizing product. 相似文献
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Deactivation by coke of a catalyst based on a SAPO‐34 in the transformation of methanol into olefins
Andrs T Aguayo Ana E Snchez del Campo Ana G Gayubo Ana Tarrío Javier Bilbao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1999,74(4):315-321
When methanol is converted to olefins on a SAPO‐34 catalyst between 350 and 425°C, there is a rapid initial formation of coke, followed by a slower rate of coke deposition. The rate of coke formation decreases with increasing temperature, and with progression through the catalyst bed. The coke completely blocks the internal channels of the SAPO‐34 crystals and subsequently blocks the mesopores (intercrystalline and those of the bentonite). Coke deposition mainly blocks sites of acidic strength above 175 kJ mol−1. The presence of water in the feed lessens coke formation, either by converting Lewis to Brønsted sites or by competing for surface sites with coke precursors. © 1999 Society of Chemical Industry 相似文献
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SAPO分子筛及其应用 总被引:3,自引:0,他引:3
磷酸硅铝分子筛(SAPO)是由SiO2、AlO2-、PO2 三种四面体单元构成的微孔型晶体,其孔结构可通过改变不同的合成条件及硅含量来控制.由于骨架呈负电性,具有可交换的阳离子,同时呈现出质子酸性,因此SAPO分子筛被广泛用作吸附剂、催化剂和催化剂载体,是一种具有优异择形选择性、热稳定性和湿热稳定性的新型催化材料. 相似文献
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磷酸硅铝分子筛SAPO是由PO_4、AlO_4和SiO_4三种四面体构成的三维骨架结构微孔型晶体,具有优异择形选择性、离子交换性、酸性可调性和水热稳定性等特殊性能,广泛用于裂解、烷基化、聚合、重整、加氢、脱氢和水合等反应。综述了SAPO系列分子筛在正构烷烃异构化反应中的应用。SAPO作载体比传统载体制得的催化剂活性高;SAPO-11负载的贵金属催化剂有较高的活性和异构选择性;小粒径SAPO系列分子筛负载的高比表面积、高活性、高稳定性和强抗中毒性能的非贵金属催化材料是异构化催化剂的研究热点。展望了SAPO系列分子筛的研究方向及应用前景。 相似文献