ZSM-5分子筛外壳的核壳结构材料研究进展

近年来,以ZSM-5分子筛为外壳的核壳结构纳米材料的制备及其应用研究受到了广泛的关注.ZSM-5分子筛壳层结构不仅具有独特的三维交叉孔道体系和均一的孔径尺寸,可提供独特的封闭式微环境,同时还具有良好的生物兼容性,使得以ZSM-5分子筛为外壳的核壳结构纳米材料在催化、医药生物等方面具有很好的应用前景.从不同结构特点(实心...     

Co-conversion of methanol and n-hexane into aromatics using intergrown ZSM-5/ZSM-11 as a catalyst

The conversion of n-hexane and methanol into value-added aromatic compounds is a promising method for their industrially relevant utilization. In this study, intergrown ZSM-5/ZSM-11 crystals were synthesized and their resulting catalytic performance was investigated and compared to those of the isolated ZSM-5 and ZSM-11 zeolites. The physicochemical properties of ZSM-5/ZSM-11 intergrown zeolite were analyzed using X-ray diffraction, N₂ isothermal adsorption-desorption, the temperature-programmed desorption of ammonium, scanning electron microscopy, Fourier transform infrared spectra of adsorbed pyridine, and nuclear magnetic resonance of ²⁷Al , and compared with those of the ZSM-5 and ZSM-11 zeolites. The catalytic performances of the materials were evaluated during the co-feeding reaction of methanol and n-hexane under the fixed bed conditions of 400°C, 0.5 MPa (N₂), methanol:꞉n-hexane=7꞉:3 (mass ratio), and weight hourly space velocity=1 h^–1 (methanol). Compared to the ZSM-5 and ZSM-11 zeolites, the ZSM-5/ZSM-11 zeolite exhibited the largest specific surface area, a unique crystal structure, moderate acidity, and suitable Brønsted/Lewis acid ratio. The evaluation results showed that ZSM-5/ZSM-11 catalyst exhibited better catalytic reactivity than the ZSM-5 and ZSM-11 catalysts in terms of methanol conversion rate, n-hexane conversion rate, and aromatic selectivity. The outstanding catalytic property of the intergrown ZSM-5/ZSM-11 was attributed to the enhanced diffusion associated with its unique crystal structure. The benefit of using zeolite intergrowth in the co-conversion of methanol and alkanes offers a novel route for future catalyst development.     

Unique properties of Ir/ZSM-5 catalyst for NO reduction with CO in the presence of excess oxygen

The reduction of NO with CO in the presence of excess oxygen was investigated over different noble metal catalysts for probing the relationship between catalytic properties and adsorption behaviors. Among the four precious metal catalysts investigated, Ir/ZSM-5 was found to be the only active one for NO reduction with CO under lean conditions. With the decreasing of the Ir content, higher NO conversion and CO selectivity was obtained. Temperature-programmed reaction (TPR) studies of NO/H₂/O₂ and NO/CO/O₂ showed that the Pt/ZSM-5 was active when H₂ was used as the reductant, whereas, the Ir/ZSM-5 was active when CO was the reducing agent. This difference is due to the different mechanisms of the two reactions. Temperature-programmed desorption (TPD) of NO, CO and O₂ showed that NO could dissociate more easily over the Ir/ZSM-5 than on the Pt/ZSM-5, while the oxidation of CO by O₂ proceeded more rapidly on the Pt/ZSM-5 than on the Ir/ZSM-5. The presence of excess O₂ inhibited drastically the dissociation of NO, which is considered as the key step for the NO–CO reaction. The high dissociation rate of NO over the Ir/ZSM-5 is visualized as the key factor for its superior high activity in NO reduction with CO under lean conditions.     

Synthesis of ZSM-5/SAPO-11 composite and its application in FCC gasoline hydro-upgrading catalyst

This article describes the synthesis, characterization and application of a novel aluminosilicate/silicoaluminophosphate composite zeolite ZSM-5/SAPO-11. The composite was synthesized by the in situ overgrowth of SAPO-11 on ZSM-5 and was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared (FT-IR) spectrometry, N₂ adsorption and infrared spectroscopy of adsorbed pyridine. The results were compared with those of the mechanical mixture composed of individual ZSM-5 and SAPO-11. In the mechanical mixture, the ZSM-5 phase was morphologically separate from the SAPO-11 phase, while the ZSM-5/SAPO-11 composite existed in a form of a core-shell structure, with the ZSM-5 phase as the core and the SAPO-11 phase as the shell. Compared with the mechanical mixture, the composite had more mesopores and moderate acidity distribution, which could accelerate the diffusion of substances and enhance the synergetic effect between Brönsted and Lewis acids. The comparison of the catalytic performances of the mechanical mixture and the composite-based Ni–Mo catalysts for FCC gasoline hydro-upgrading showed that, due to the above advantages of the composite, the corresponding catalyst yielded improved gasoline research octane number, high liquid yield, good desulfurization activity and lower coke amount and thus could be considered as a potential catalyst system for hydro-upgrading FCC gasoline.     

Pt/TiO2/ZSM-5催化剂的制备及其催化转化正丁烷

采用溶胶-凝胶法和等体积浸渍法,分别对ZSM-5分子筛进行TiO₂改性和Pt负载,获得了具有脱氢-裂解双功能的Pt/TiO₂/ZSM-5催化剂,采用XRD、N₂吸附-脱附、TEM、XPS和NH₃-TPD对样品的晶体结构,孔结构、形貌、活性金属价态和酸性质等进行了表征,并研究了正丁烷在此催化剂上催化转化制备低碳烯烃的反应规律。研究结果表明,TiO₂的引入,一方面使得改性后的ZSM-5分子筛获得了额外的酸性中心,特别是强酸性位含量的增加,有助于促进正丁烷的活化;另一方面Pt与TiO₂之间存在“金属-载体”强相互作用（SMSI）,在H₂还原气氛下,Pt能够促进TiO₂的还原,生成Ti³⁺物种,而Ti³⁺的存在增加了Pt周围的电荷密度,降低了Pt对低碳烯烃（C₂⁼～C₃⁼）的吸附能力,抑制了深度脱氢和生焦反应,从而提高双功能催化剂对烯烃的选择性。当H₂还原温度为450℃时,Pt/10TiO₂/ZSM-5催化剂在625℃下的正丁烷转化率为76.1%,低碳烯烃（C₂⁼～C₃⁼）收率为50.9%,分别比Pt/ZSM-5催化剂提高了16.7%和12.6%。     

空气气氛下RuO2/ZSM-5催化醇的部分氧化反应

通过原位反应法制备了RuO₂/ZSM-5催化剂，并用XRD、XPS和TEM对合成的催化剂进行了表征，结果表明，RuO₂主要以20 nm左右的微晶分散在载体中，原位反应引入钌物种，没有改变载体ZSM-5的结构，大部分钌为四价。催化试验表明，在以空气为氧化剂的温和条件下，RuO₂/ZSM-5不仅可有效地催化芳香醇和带烯丙基的醇类（激活醇）氧化生成醛酮，而且对一些非激活醇也有较好的催化效果。     

铜-铈/ZSM-5分子筛催化剂制备及脱硝性能研究

氮氧化物是大气主要污染源之一,危害人体健康,并引发酸雨。随着环保法规的升级,氮氧化物排放浓度的限值要求越来越高。这要求脱硝工艺尤其是脱硝催化剂必须进一步提高脱硝性能。以ZSM-5分子筛为载体,以铜、铈为活性组分,制备脱硝催化剂活性组分;用铝胶将脱硝催化剂活性组分附着在蜂窝状陶瓷上,得到脱硝催化剂。与ZSM-5分子筛相比,脱硝催化剂活性组分增加了4.73%的铜（以CuO质量分数计）和5.40%的铈（以CeO₂质量分数计）,比表面积由287.04 m²/g降到275.05 m²/g,孔容、孔径未发生变化,酸性增强,晶型基本保持不变。脱硝催化剂最佳反应条件：反应时间≥60 min,反应温度≥250 ℃,空速≤10 200 h^-1。脱硝催化剂在最佳反应条件下的脱硝效率约为85%。脱硝催化剂能适应较低的反应温度,并且具有较高的脱硝效率。     

Hollow core/mesoporous shell carbon capsule as an unique cathode catalyst support in direct methanol fuel cell

Hollow core mesoporous shell (HCMS) carbon has been explored for the first time as a cathode catalyst support in direct methanol fuel cells (DMFCs). The HCMS carbon consisting of discrete spherical particles possesses unique structural characteristics including large specific surface area and mesoporous volume and well-developed interconnected void structure, which are highly desired for a cathode catalyst support in low temperature fuel cells. Significant enhancement in the electrocatalytic activity toward oxygen reduction reaction has been achieved by the HCMS carbon-supported Pt nanoparticles compared with carbon black Vulcan XC-72-supported ones in the DMFC. In addition, much higher power was delivered by the Pt/HCMS catalysts (i.e., corresponding to an enhancement of ca. 91–128% in power density compared with that of Pt/Vulcan), suggesting that HCMS carbon is a unique cathode catalyst support in direct methanol fuel cell.     

过渡金属改性对MgO/ZSM-5催化剂苯-甲醇烷基化性能的影响

采用过渡金属对2.5%Mg O/ZSM-5催化剂进行负载改性,考察其苯-甲醇烷基化性能,结果表明,Ni和Fe改性催化剂因改性后弱酸量大幅增加,苯转化率提高,分别为56.6%和55.8%;W和Mn改性催化剂二甲苯选择性较高,约为35%;与其他改性催化剂相比,Co和Mo改性催化剂上的苯转化率和二甲苯选择性没有明显优势。选择改性效果较好的双金属催化剂进行苯-甲醇烷基化高空速(15 h-1)长时间运转实验,催化剂初始活性均大于57%,反应20 h时,苯转化率约50%,20 h后烷基化活性迅速下降,是由于催化剂积炭失活所致。     

核/壳结构硅丙微乳液的合成与表征

以丙烯酸酯[如MAA(α-甲基丙烯酸)、n-BMA(甲基丙烯酸正丁酯)和MA(丙烯酸甲酯)等]和A-151(乙烯基三乙氧基硅烷)为共聚单体、OP-10(辛基酚聚氧乙烯醚)/JFC(聚醚渗透剂)为复合乳化剂、戊醇为助乳化剂和KPS(过硫酸钾)为引发剂,采用分段控温、补加引发剂等方法制得丙烯酸酯预聚乳液;然后采用核/壳接枝聚合反应和氨化反应,制得半透明核/壳型硅丙微乳液。研究结果表明:当分段聚合温度为75℃和65℃时,采用上述方法制成的硅丙微乳液中A-151含量高达12%左右(相对于微乳液总质量而言),乳胶粒具有明显的核/壳型结构,粒径为10⁶0 nm,并且微乳液体系聚合稳定性良好。     

Characterization and Adsorption Behavior of ZSM-5 Zeolite Film on Cordierite Honeycombs Prepared by a Novel in situ Crystallization Method

Thin films of ZSM-5 zeolite prepared on three types of cordierite ceramic honeycomb substrates by a novel in situ crystallization method were characterized by XRD, FTIR, XRF, SEM-EDX, NH₃-TPD and propane gas adsorption to examine the effect of the substrate on various properties of the ZSM-5 films. The substrates were both as-prepared and acid treated cordierite honeycombs. The XRD, FTIR and XRF results showed that silica-rich surface layers were formed on the surface of the honeycombs by the acid treatments. The SiO₂/Al₂O₃ ratios of the ZSM-5 zeolite formed on these layers increased with increasing time of acid treatment. Both Al₂O₃ and SiO₂ from the substrates were found to contribute to the formation reaction of the zeolite films corresponding to the composition of the interfacial layer. The porous properties of the honeycomb substrates also varied in relation to the amount of zeolite film, which increased linearly with acid treatment time. The presence of the silica-rich interfacial layer between the substrate and zeolite film increased the amount of ZSM-5 and the physical adsorption but decreased the solid acidity and amount of chemisorption.     

In situ high temperature FTIR studies of NOx reduction with propylene over Cu/ZSM-5 catalysts

High temperature in situ FTIR has been used to investigate the surface species present on Cu/ZSM-5 during the reduction of NO_x with propylene in a lean environment. Parallels have been observed between adsorbed surface species and catalytic activity for this reaction. Species detected at low temperatures are not representative of those detected at high temperatures where the catalyst is active. An oxidized nitrogen-containing species has been observed at 2580 cm^–1 on Cu during reaction conditions (400°C). In contrast, at low temperatures, where the catalyst is less active, coke and Cu⁺-CO predominated. The effects of Cu weight loading, C/NO ratio, reaction temperature, and catalyst deactivation by steaming have been investigated with IR.     

多级孔ZSM-5/SAPO-34复合分子筛制备及催化MTO性能研究

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。     

用于高湿度废气中甲苯吸附净化的疏水型ZSM-5分子筛的合成及其吸附性能研究

采用水热原位法合成了不同硅铝比的ZSM-5分子筛,研究了硅铝比对ZSM-5分子筛结构和疏水性的影响。以典型的挥发性有机物甲苯为对象,在动态吸附实验装置上评价了ZSM-5分子筛吸附有机物的性能,并拟合了甲苯在疏水ZSM-5上的吸附等温线方程。结果表明,高硅铝比ZSM-5具有良好的疏水性,其静态水吸附容量为0.014 g·g^-1,在高湿度条件下,甲苯浓度为1800 mg·m^-3,GHSV为25000 ml·h^-1·g^-1,温度为35℃,甲苯穿透吸附容量为0.041 g·g^-1,甲苯饱和吸附容量为0.075 g·g^-1。吸附等温线的拟合显示,甲苯在疏水ZSM-5分子筛上的吸附符合Langmuir-Freundlich复合模型。     

催化裂化汽油在磷改性Ni/ZSM-5催化剂上的降烯烃工艺研究

采用浸渍法制备了Ni/ZSM-5和NiP/ZSM-5催化剂,其中Ni、P分别为HZSM-5质量的3％和0.5％。以锦州石化公司重油FCC汽油为原料,考察了助剂P加入前后催化剂的降烯烃反应性能。结果表明, NiP/ZSM-5催化剂具有较好的加氢降烯烃、异构化和芳构化活性,液体收率较高;考察了工艺条件对NiP/ZSM-5催化剂降烯烃反应的影响。在温度310 ℃、液时质量空速3 h^－1、氢油体积比300和反应压力2.5 MPa的最佳反应条件下,FCC汽油烯烃转化率、液体收率、产品中异构烷烃和芳烃的质量分数分别为72.9％、82.1％、45.84％和30.44％,而产品辛烷值不降低,达到了既降烯烃又不损失辛烷值的预期目的。     

A structural study of the Fe/ZSM-5 catalyst by through-focus exit-wavefunction reconstruction in HRTEM

Through-focus exit-wavefunction reconstruction in high-resolution transmission electron microscopy has been applied to process the image series obtained from both the simple ZSM-5 catalyst and an iron-loaded one prepared by impregnation. In conventional high-resolution transmission electron microscopic observations, artificial patches due to electron optical effects always appear in the centers of the ten-member ring channels of the ZSM-5 structures, preventing the atomic details in the channels to be revealed, which are crucial information for understanding the catalytic properties of this type of catalysts. Our study shows that such artificial patches can be removed in the retrieved exit-wavefunctions, allowing the projected structures of the ZSM-5 zeolites to be imaged. Together with X-ray energy dispersive spectroscopy, through-focus exit-wavefunction reconstruction confirmed the existence of iron atoms in the ten-member ring channels of the iron-loaded ZSM-5 catalyst.     

Fe-Cu/ZSM-5催化剂及其胺化催化性能研究

制备了一种Fe-Cu/ZSM-5胺化催化剂,考察其在乙醇胺选择性合成哌嗪、三乙烯二胺反应中的催化活性。结果表明,随着Fe、Cu负载量的增加,催化剂表面酸性逐渐向强酸方向位移,总酸量增加,反应转化率提高;Cu负载量对反应转化率及乙二胺选择性的影响相对较弱,但对哌嗪的生成有明显的促进作用;催化反应性能不仅受催化剂酸性的影响,还与负载组分的性质及负载组分与载体间的相互作用有关。     

Decomposition of methane and its reaction with CO2 over Rh/ZSM-5 catalyst

The decomposition of methane, its conversion into higher hydrocarbons and the reaction between CH₄ and CO₂ have been investigated on Rh/ZSM-5 in a fixed bed continuous-flow reactor. Independently of the temperature at 523–973 K, the decomposition of methane gave hydrogen, surface carbon and a small amount of ethane: ethylene and benzene were not detected. The reactivity of surface carbon formed at different temperatures has been examined toward H₂, O₂ and CO₂. The carbon exhibited less reactivity toward CO₂. The reaction between CH₄ and CO₂ occurred rapidly above 673 K to give CO and H₂ with a ratio of 1.3–1.6. Very little carbon was deposited during the reaction. It is concluded that the facile reactions between CH_x and CO₂ are responsible for the lack of carbon deposition. However, a significant amount of carbon deposition and the deactivation of the catalyst occurred when more than 4–5% of ethane was added to the reacting gas mixture. The extent of deactivation can be decreased by using a large excess of CO₂. This revised version was published online in June 2006 with corrections to the Cover Date.     

微米级聚苯乙烯/聚硅氧烷核壳微球的制备、表征及其作为光散射剂的应用

在乙醇/水混合溶剂中采用分散聚合法制备出微米级聚苯乙烯微球,将聚苯乙烯核微球与甲基三甲氧基硅烷的水解溶液混合,加入氨水使硅烷水解产物在核表面缩合交联,制备出微米级聚苯乙烯/聚硅氧烷核壳微球.采用TEM、粒径分布仪、EDX、TG等对核壳微球的形貌、粒径、表面成分和热失重进行了表征.将核壳微球作为光散射剂添加在聚甲基丙烯酸甲酯（PMMA）树脂中,制备出性能良好的光散射材料.当SS6核壳微球的添加浓度为1%（质量）时,制得的PMMA样片（2 mm）的雾度为88.16％,透光率为72.5％;当SS6添加浓度为2%（质量）时,其雾度为92.13％.     

Phosphorus poisoning of ZSM-5 and Pt/ZSM-5 zeolite catalysts in diesel exhaust gas conditions

Powdered ZSM-5 and Pt/ZSM-5 catalysts were studied as fresh and after two treatments: hydrothermal ageing and phosphorus poisoning in hydrothermal conditions. The results showed that the deactivating effect of phosphorus was stronger than the effect of the hydrothermal treatment alone. Phosphorus had accumulated in the samples during the ageing. The decrease in specific surface area and increase in Pt particle size indicated the possible reasons for deactivation.