改性分子筛催化乳酸甲酯的脱水反应

通过生物基路线制备丙烯酸及酯具有潜在的经济效益.同时对化石资源的绿色替代具有重要意义.考察了X.Y.ZSM-5等沸石分子筛经过钾、钙、钻等金属离子交换改性后,在乳酸甲酯脱水制备生物基丙烯酸甲酯过程中的催化性能.试验结果表明K离子改性Y沸石分子筛对产物的选择性高,而ZSM-5类具有较高的转化率,但是选择性低.分析结果说明:Y分子筛催化剂的高选择性与其特有的骨架结构相关.沸石分子筛催化剂需要通过金属离子的交换才能调整到适当的酸碱性实现最佳催化的效果.在上述结论的基础上.以钾离子改性的NaY分子筛为催化剂,对反应温度.反应空适等反应条件进行了优化得到了较高的丙烯酸甲酯得率.     

生物基乳酸(酯)制丙烯酸的工艺研究

以乳酸（酯）脱水反应为模型反应,分别考察了X、Y、ZSM-5和SBA等分子筛、硫酸盐、磷酸盐以及复配催化剂的催化性能。结果表明,适当调节分子筛催化剂的酸碱度,实现多种催化剂的复配应用,催化剂性能较好,丙烯酸及其酯的总选择性达80.3%。     

Carbonylation of Formaldehyde with Zeolite Catalysts

Carbonylation of formaldehyde with carbon monoxide over zeolite catalysts has been investigated. Compared with resins (Amberlyst-15 and Amberlyst-70), and phosphotungstic acid, the zeolite catalysts especially ZSM-5 showed very high selectivity to methyl glycolate. The selectivity of ZSM-5 was maintained to high temperature up to 200 °C.     

Catalysts based on zeolite ZSM-23 for isodewaxing of a lubricant stock

Granular Pt/(ZSM-23-γ-Al₂O₃) catalysts with different platinum and zeolite contents have been synthesized with the aim of developing efficient isodewaxing catalysts for lowering the pour point of lubricants and diesel fuels. Their physicochemical properties have been studied by X-ray diffraction, temperature-programmed desorption of ammonia, and low-temperature nitrogen adsorption/desorption. The effects of catalyst composition and process conditions (1.0–3.0 MPa, 220–400°C) on the outcomes of the isodewaxing of the 280°C-EBP lubricant fraction isolated from the hydrocracking product of vacuum gas oil have been investigated. The highest yields of products with the same pour points have been obtained with a 0.30 wt % platinum catalyst supported on the 20 wt % zeolite ZSM-23 + 80 wt % γ-Al₂O₃ material. An analysis of the basic performance characteristics of the isodewaxing catalysts based on zeolite ZSM-23 and dewaxing catalysts based on zeolite ZSM-5 has demonstrated that the catalysts based on ZSM-23 ensure higher yields of dew-axed products than the laboratory and commercial catalysts based on ZSM-5.     

Preparation and application of Ba/ZSM-5 zeolite for reaction of methyl vinyl ether and methanol

The ZSM-5 zeolite is widely used to catalyze the reactions of methanol to olefins. Herein, we have prepared the H-ZSM-5 doped with barium (Ba/ZSM-5) using incipient wetness impregnation method. The Ba modified catalysts were used to catalyze a new reaction of methanol with methyl vinyl ether to improve the selectivity of ethylene and propylene (C₂⁼ + C₃⁼). The reaction catalyzed by Ba doped H-ZSM-5 shows higher propylene selectivity over H-ZSM-5. The reaction mechanism is discussed.     

Isomerization of isobutyraldehyde to methyl ethyl ketone on zeolite catalysts

The isomerization of isobutyraldehyde (IBH) was studied over aluminium-free ZSM-5 zeolite catalysts with different boron content in the framework. The selectivity to methyl ethyl ketone (MEK) is high, ca. 83 wt%. With the increase of boron content, the conversion of IBH increased but the selectivity to MEK decreased. The effects of Na content, cation-exchange, 500°C-steam treatment and temperature on catalyst activity were investigated. It was observed that cation-exchange resulted in the decrease of conversion of IBH and increase of selectivity to MEK, but 500°C-steam treatment resulted in the decrease of selectivity to MEK.     

Fe-BEA Zeolite Catalysts for NH3-SCR of NOx

Iron-containing zeolites are known to be promising catalysts for the NH₃-SCR reaction. Here, we will investigate the catalytic activity of iron-based BEA catalysts, which was found to exhibit improved activities compared to previously described iron-containing zeolite catalysts, such as ZSM-5 and ZSM-12. Series of Fe-BEA zeolite catalysts were prepared using a range of different preparation methods. Furthermore, we found that an iron concentration around 3 wt% on BEA showed a small optimum in SCR activity compared to the other iron loadings studied.     

One-Step Synthesis of Dimethyl Ether from Syngas with Fe-Modified Zeolite ZSM-5 as Dehydration Catalyst

A number of Fe-containing ZSM-5 zeolites, such as HFeZSM-5 and HFeAlZSM-5 prepared by hydrothermal synthesis and Fe-modified ZSM-5 through solid-state ion-exchange, were adopted as methanol dehydration catalysts for syngas to dimethyl ether (STD) process. Their structures, acidic and basic properties were characterized by XRD, ESR, ICP-AES, TPD and FT-IR. Among these Fe-containing zeolites, the Fe-modified ZSM-5 displayed the highest dimethyl ether selectivity, least CO₂ production. Some correlations between catalytic performance and acidity and basicity of Fe-containing ZSM-5 zeolite were discussed.     

A new <Emphasis Type="Italic">n</Emphasis>-alkane hydroisomerization catalyst modified with nanosized molybdenum carbides and its catalytic properties in diesel fraction hydroisomerization. I. Synthesis and physicochemical properties of different acidic supports for hydroisomerization catalysts

Hydroisomerization catalysts based on nanosized molybdenum carbides are developed. Such catalysts are resistant to sulfur compounds and can be used for the synthesis of waxy diesel fuels with the same characteristics as on platinum-containing catalysts. In the first part of this work, acidic supports with different types of porous structure and concentrations and strengths of Brønsted acidic sites (e.g., silicoaluminophosphate SAPO-31, zeolite ZSM-12, modified zeolite Beta, and desiliconized zeolite ZSM-5) are synthesized for a new type of catalysts. Their physicochemical properties are studied by means of adsorption, temperature- programmed desorption of ammonia (TPD-NH₃), nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM).     

Decomposition of nitrous oxide in excess oxygen over Co- and Cu-exchanged MFI zeolites

The decomposition of nitrous oxide on several Co- and Cu-ZSM-5 zeolite catalysts was studied in the absence and presence of excess oxygen. Also, the effect of methane addition, as well as catalyst steaming in dry and wet feeds is reported. N₂O decomposition with no oxygen in the feed was proportional to metal loading on both catalysts. Co-ZSM-5 was much more resistant than Cu-ZSM-5 in excess oxygen. The tolerance of Co-ZSM-5 catalysts to excessive amounts of oxygen is high when Co²⁺ is stabilized in the zeolite framework and depends on the catalyst method of preparation. The presence of methane with no oxygen in the feed enhanced N₂O decomposition while the addition of both methane and oxygen to the feed decreased N₂O conversion on all catalysts tested. Co²⁺ ions stabilized by ZSM-5 framework have high hydrothermal stability in comparison to Cu²⁺ -exchanged ZSM-5.     

甲苯甲醇烷基化合成对二甲苯催化剂研究进展

甲苯甲醇烷基化是新型高选择性合成对二甲苯的方法,可以解决石化行业甲苯和甲醇过剩问题,具有较高的工业开发价值。在具有B酸中心及特殊孔结构的分子筛催化下,甲苯甲醇发生苯环上亲电取代反应得到对二甲苯。甲苯甲醇烷基化催化剂主要有Y沸石催化剂、SAPO及MCM-22和ZSM-5分子筛催化剂等,研究较多的是ZSM-5分子筛催化剂。通过对ZSM-5分子筛进行金属、非金属或复合改性后,可以显著提高烷基化反应转化率和选择性。未来研究的主要目标是获得选择性高且稳定性好的催化剂。     

Effect of magnesium in the conversion of methanol on chryso-zeolite or zeolite ZSM-5 catalysts

Methanol can be converted to a wide range of hydrocarbons using zeolite or chryso-zeolite ZSM-5 type catalysts. Chryso-zeolite ZSM-5 catalysts, which were prepared from asbestos fibers, were found to be active and very selective in the conversion of methanol when compared to a “pure” zeolite ZSM-5. Their peculiar catalytic properties were essentially related to the presence of magnesium coming from the asbestos microstructure. The amount of magnesium extracted from the fibers before the zeolite hydrothermal synthesis influenced the particle size, the selectivity and particularly the adsorption/desorption properties of the catalysts. The presence of a basic site generated by the magnesium led to catalysts with controlled selectivity and activity under normal reaction conditions.     

Bimetallic PtSn nanoparticles confined in hierarchical ZSM-5 for propane dehydrogenation

A series of PtSn/hierarchical ZSM-5 catalysts were developed for propane dehydrogenation,in which the PtSn bimetallic particles are confined in the mesopores of hierarchical ZSM-5 zeolite.The synthesis of PtSn/hierarchical ZSM-5 catalysts was achieved via the loading of Pt and Sn species onto the hierarchical ZSM-5 catalysts that are obtained through a desilication of conventional ZSM-5.The PtSn/hierarchical ZSM-5 catalysts were fully characterized by XRD,N2 adsorption,STEM,XPS,and CO-IR techniques,which reveals that highly dispersed PtSn bimetallic nanoparticles are enclosed into mesopores of hierarchical ZSM-5.The catalytic performance of PtSn/hierarchical ZSM-5 is greatly affected by the concentrations of alkali solution in the desilication process and Sn/Pt ratios in PtSn bimetallic particles.The PtSn1.00/ZSM-5(0.8) catalyst shows the highest efficiency in propane dehydrogenation,which gives an initial con-version of 46％ and selectivity of 98％ at 570 ℃.The high efficiency in these PtSn/hierarchical ZSM-5 cat-alysts for propane dehydrogenation is mainly ascribed to the confinement of PtSn particles in the mesopores of hierarchical ZSM-5 zeolite.     

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。     

Differences between ZSM-5 and ZSM-11 zeolite catalysts in 1-hexene aromatization and isomerization

ZSM-5 and ZSM-11 zeolites with high crystallinity are synthesized and tested in the aromatization and isomerization reactions of 1-hexene at 370 °C in a continuous flow fixed bed. The results indicate that ZSM-5 and ZSM-11 zeolites possess similar acid site amount and strength, and most of the acid sites belong to Brønsted acid. When the ZSM-5 and ZSM-11 zeolites were used as catalysts, the aromatics selectivity over ZSM-11 catalyst was higher than that over ZSM-5 catalyst in contrast to i-paraffins selectivity, maybe attributed to that the C₇ and C₈ aromatics have an easier exit from the ZSM-11 zeolite. Moreover, the decrease of particle size can present superior aromatics selectivity and less i-paraffins selectivity in the aromatization and isomerization of 1-hexene over the ZSM-11 catalyst.     

Synthesis and characterization of MCM-41-type composite materials prepared from ZSM-5 zeolite

Micro/mesoporous composite materials with microporous and mesoporous double pores-size distribution were hydrothermally synthesized by using slurry or filtrate of alkali-treated ZSM-5 zeolite and were characterized by XRD, N₂ adsorption, FT-IR, TEM and so on. The XRD and TEM patterns indicate the composite materials possess ordered hexagonal structure. The sample MZ-B using filtrate of alkali-treated ZSM-5 zeolite hardly contains raw ZSM-5 particles. However, sample MZ-A originated from the slurry of alkali-treated ZSM-5 zeolite may contain some ZSM-5 crystallites, owing to the differences in concentration and time of alkaline treatment for ZSM-5 zeolite.     

Transesterification of Refined Sunflower Oil to Biodiesel Using a CaO/ZSM-5 Powder Catalyst

The production of biodiesel from refined sunflower vegetable oil over basic CaO/ZSM-5 catalysts was investigated. Several catalysts with various loadings of CaO on ZSM-5 were prepared, calcined at 800 °C, and characterized by N₂ adsorption-desorption, X-ray diffraction, Fourier transform infrared spectroscopy, and CO₂-temperature-programmed desorption techniques. Calcined catalysts were tested in the transesterification reaction and reaction conditions were optimized by varying the catalyst-to-oil ratio and reaction time. The most active catalyst was the CaO/ZSM-5 catalyst with a 35 wt % loading which gave the highest fatty acid methyl ester yield. The high catalytic activity was attributed to the active basic sites generated following CaO addition. Furthermore, the catalyst demonstrated stability against the leaching process.     

Organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite

A series of ZSM-5/ZSM-11 co-crystalline zeolites with various compositions and morphologies were successfully synthesized via an organic template-free hydrothermal route and characterized by XRD, XRF, SEM, NMR and N₂ adsorption/desorption technologies. The effects of raw materials and batch composition were investigated systematically. Various silicon sources can be employed in the organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite, however only a few types of aluminum sources are available. This organic template-free system is favorable to the aluminum-rich zeolite. With the increase of initial SiO₂/Al₂O₃ ratio, the ZSM-5 percentage in the ZSM-5/ZSM-11 co-crystalline zeolite increases as well as the crystal size, and especially the morphology of ZSM-5/ZSM-11 co-crystalline zeolite prepared from the colloidal silica-NaAlO₂ solution system changes gradually from nano-rod aggregation, micro-spindle to single hexagon and then to twinned hexagon crystals. Moreover, Na⁺ and OH⁻ in the initial materials can promote the nucleation of the ZSM-5/ZSM-11 co-crystalline zeolite significantly and are beneficial to the formation of crystals with relatively low length/width ratio, while K⁺ postpones the crystallization process seriously.     

Metal Exchanged ZSM-5 Zeolite Based Catalysts for Direct Decomposition of N2O

Co+Pt/ZSM-5 and Ag+Pt/ZSM-5 type catalysts were prepared by ion exchange method followed by calcination. These Co and Ag based catalysts, promoted by a small amount of Pt have been studied for their catalytic activity towards N₂O decomposition. Both the catalysts show high catalytic activity, however, cobalt–platinum based catalyst shows relatively better activity at higher temperature. At 550 °C almost 100% conversion of N₂O is achieved over Co+Pt/ZSM-5 with a maximum of 0.08479 mmole of N₂O decomposed per gram of the catalyst per unit time. These catalytic materials have been characterized for their structure, composition, morphology and other details, using XRD, SEM, EDX, ICP, BET techniques. Much improved catalytic activity for the bimetallic zeolite than the mono-metal containing compositions clearly demonstrate the synergistic effect of these transition metals, while high surface area of ZSM-5 is also responsible for the improved N₂O decomposition activity.     

不同结构分子筛的甲醇制丙烯催化性能

在常压、空速为1.5 h^-1、反应温度为450℃条件下,考察了4种具有不同拓扑结构的分子筛(SAPO-34、ZSM-48、ZSM-5和beta)在甲醇转化制丙烯(MTP)反应中的催化性能,并对催化剂的积炭失活行为进行了研究。结果表明,从8元环到12元环,分子筛孔口尺寸越小,低碳烯烃(乙烯+丙烯)选择性越高,积炭失活速率也越快。孔道尺寸越大,丙烯/乙烯(P/E)比越高,但产物分布向C₄以上组分偏移,丙烯选择性降低。10元环分子筛具有较高的丙烯选择性,但催化剂的积炭失活速率随孔道体系的不同有很大差异。一维直通孔道的ZSM-48容易积炭失活,而具有三维交叉孔结构的ZSM-5表现出了优异的抗积炭失活性能。不同结构分子筛在MTP反应中催化性能的差异主要归因于分子筛的过渡态择形和产物择形作用的不同。