硅铝比对ZSM-5分子筛催化甲醇制烯烃性能的影响

以n(Si)/n(A1)分别为25、38、50、80、360的ZSM-5分子筛为催化剂,利用N2吸附-脱附、XRD和NH3-TPD对催化剂的孔结构和表面酸性进行表征分析,测定催化剂对甲醇制低碳烯烃(MTO)各产物的选择性,讨论催化剂的孔结构与表面酸性对其催化性能的影响。结果表明,随硅铝比增加,催化剂平均孔径逐渐减小,中强酸逐渐消失,酸强度逐渐减弱,烯烃的选择性逐渐增大,催化剂的稳定性逐渐增强。其中,硅铝比360的分子筛具有最低的表面酸强度,最大的比表面积和最小的孔径,MTO催化性能最佳,乙烯+丙烯的选择性达69.36%。     

Multifunctional Silver‐Exchanged Zeolite Micromotors for Catalytic Detoxification of Chemical and Biological Threats

Multifunctional reactive‐zeolite‐based micromotors have been developed and characterized toward effective and rapid elimination of chemical and biological threats. The incorporation of silver ions (Ag⁺) into aluminosilicate zeolite framework imparts several attractive functions, including strong binding to chemical warfare agents (CWA) followed by effective degradation, and enhanced antibacterial activity. The new zeolite‐micromotors protocol thus combines the remarkable adsorption capacity of zeolites and the efficient catalytic properties of the reactive Ag⁺ ions with the autonomous movement of the zeolite micromotors for an accelerated detoxification of CWA. Furthermore, the high antibacterial activity of Ag⁺ along with the rapid micromotor movement enhances the contact between bacteria and reactive Ag⁺, leading to a powerful “on‐the‐fly” bacteria killing capacity. These attractive adsorptive/catalytic features of the self‐propelled zeolite micromotors eliminate secondary environmental contamination compared to adsorptive micromotors. The distinct cubic geometry of the zeolite micromotors leads to enhanced bubble generation and faster movement, in unique movement trajectories, which increases the fluid convection and highly efficient detoxification of CWA and killing of bacteria. The attractive capabilities of these zeolite micromotors will pave the way for their diverse applications in defense, environmental and biomedical applications in more economical and sustainable manner.     

A review on Zeolite-Reinforced Polymeric Membranes: Salient Features and Applications

Various types of synthetic polymeric membranes have been fabricated for separation purposes in industry/laboratory. Zeolite is ceramic-based material and well known for its antiwear resistance and high mechanical strength. Mixed matrix membranes are the latest membrane technology constituting inorganic nanoparticle phase and organic polymer phase. The review represents various types and applications of zeolite-reinforced polymeric membranes. Consequently, fabrication procedure and working principle of zeolite-reinforced mixed matrix (polyimide, polysulfone, polycarbonate) membranes have been discussed. The significant relevance of polymer/zeolite membranes is in water purification, medical, catalytic, and gas separation industries. Improvement in polymeric membrane properties has been observed through incorporation of zeolite filler.     

ZSM-5分子筛在MTP反应中的催化性能

合成了3种不同晶粒尺寸的ZSM-5分子筛,并制得MTP催化剂,对ZSM-5分子筛催化剂在MTP反应中的性能进行系统研究。采用XRD、SEM、N2物理吸附和TGA等对ZSM-5分子筛催化剂进行表征,发现小晶粒的ZSM-5分子筛具有良好的抗积炭性能,在MTP反应中具有较高的稳定性。采用小晶粒分子筛制成的催化剂,考察反应工艺条件对催化剂催化性能的影响,结果表明,丙烯选择性随反应温度和空速提高而增加,降低反应压力和提高水醇质量比也有利于提高丙烯选择性,为调整MTP工艺的产物分布和优化反应工艺条件提供了技术依据。     

TS-1分子筛催化剂的制备和表征

以四丙基氢氧化铵为模板剂,正硅酸乙酯为硅源,钛酸四丁酯为钛源,异丙醇为络合剂,碳酸铵为晶化调节剂,对经典水热法进行改进,制备出形貌规则且粒径约为200 nm的TS-1分子筛,考察晶化时间、正硅酸乙酯水解时间及络合剂种类对骨架Ti含量的影响,并采用XRD、SEM、FTIR和UV-Vis等对合成的样品进行表征。结果表明,当正硅酸乙酯水解2 h和晶化时间3天时,异丙醇的加入可有效阻止TiO_2沉淀的产生,同时加入(NH_4)_2CO_3能够促进钛物种进入TS-1分子筛骨架,提高骨架中的Ti含量。     

硅源对纳米级ZSM-5分子筛结构及其对甲醇转化制丙烯与丁烯反应催化性能的影响

采用低温水热晶化法,以四丙基氢氧化铵为模板剂,分别使用98%粗孔固体硅胶和30%硅溶胶为硅源,制备不同硅铝物质的量比的纳米级ZSM-5分子筛,研究硅源对其物化结构及甲醇转化制丙烯与丁烯催化性能的影响。结果表明,硅源种类影响ZSM-5分子筛的结构及铝分布,进而影响其酸性和催化性能。固体硅胶为硅源,有利于形成弱酸性位点;硅溶胶为硅源,有利于形成强酸性位点。在相同硅铝物质的量比时,以固体硅胶为硅源的ZSM-5分子筛的总酸量小于以硅溶胶为硅源的样品。无论使用何种硅源,对ZSM-5分子筛的晶型结构影响不大,且ZSM-5分子筛颗粒形貌均呈现为由小晶粒堆积成(500~1 000)nm的类球形颗粒。以硅溶胶为硅源制备的样品颗粒尺寸大于以固体硅胶为硅源制备的样品。硅铝物质的量比为400时,两种硅源合成分子筛的丙烯与丁烯的选择性相近,但以硅溶胶为硅源的ZSM-5分子筛的寿命更长。     

沸石去除废水中氨氮的研究进展

沸石是一种天然的廉价矿物,对水中的氨氮具有较强的吸附作用,本文介绍了天然及改性沸石在去除水中氨氮的应用现状及进展,在此基础上提出了加强沸石在水处理领域研究力度、加大对资源开发的资金投入和加速成果转化的建议。     

Fish-scale-like nano-porous membrane based on zeolite nanosheets for long stable zinc-based flow battery

Zinc-based flow batteries receive widespread attention due to their advantages of low cost and high energy density. However, zinc dendrites are easy to appear during the charge process, pierce the membrane and thus destroy the battery, which seriously restrict its further development. In this article, MFI-type zeolite nanosheets (ns-MFIs) with high mechanical strength and hydrophobicity are in situ introduced to porous polymer membranes, which spontaneously form turnup fish-scale-like structure through the one-step phase inversion/surface segregation process. This special structure well disperses mechanical energy to provide effective protection characteristics to resist the penetration of zinc dendrites, and meanwhile promotes the uniform zinc depositions on the electrode by alleviating the water migration and accelerating zincate ion diffusion, so as to prolong the cycle life of the battery for more than 600 cycles, which is 4 times and 2.5 times longer than the commercial Nafion 212 and pristine porous polymer membrane, respectively. Moreover, the sub-nano size pores and high-aspect-ratio of ns-MFIs afford membranes extra ion sieving ability and transport area for the charging-balancing ions OH⁻ to ensure superior battery performance, delivering an average coulombic efficiency (CE) of ~98.5%, voltage efficiency (VE) of ~83.2%, and energy efficiency (EE) of ~81.9% at 80 mA/cm².     

HZSM-5催化甲醇制丙烯工艺条件的考察

以工业应用的HZSM-5为催化剂,在连续固定床反应器中考察了反应温度和甲醇分压对甲醇制丙烯反应产物的影响,发现当温度大于450℃时,随着温度的升高,甲醇的转化率都能达到99%以上,乙烯和丙烯的总选择性增加,低碳烷烃选择性增加,高碳产物选择性下降;随着甲醇分压降低,甲醇转化率下降,产物丙烯/乙烯质量比(P/E比)增加,丙烯在甲醇分压为33 kPa时达到最高值,而当分压极低时,催化剂快速失活。从转化率、丙烯选择性、P/E比以及低碳烯烃产物选择性等多方面综合考虑,甲醇转化制丙烯的反应温度优选470℃,并建议甲醇分压为33 kPa。     

Ti02／13X分子筛的合成、表征及催化脂肪氧化的研究

以钾长石与碳酸钠焙烧的热料为原料,经水热法合成13X型分子筛。进一步经溶胶一凝胶化过程和13X分子筛上负载TiO2以制稀TiO2／13X,并利用XRD、FTIR、SEM和EDS等对儿结构与性能进行表征。将13X和TiO2／13X用于催化脂肪氧化,测定氧化脂肪的过氧化值、p-茴香胺值和酸值,并以总钒化值和p-1茴香胺值作为反戍转化牢和选择性的评价参数,考察了催化剂的催化性能。结果表明,Ti／13X催化脂肪氧化的转化率和选择性者都远高于13X。此外,还研究了催化反应条件如温度、时间、空气流量等对催化反应的影响。