Cu/ZSM-5催化剂制备及SCR催化性能研究

采用固态离子交换法制备了不同Cu含量的Cu/ZSM-5改性分子筛型催化剂,并对其理化特性及SCR反应活性进行了表征。结果表明:所制备催化剂中Cu元素富集于分子筛的浅层及表面,并主要以二价铜的形式存在;随Cu含量增加,低温弱酸吸附峰和中温中强酸吸附峰面积增加,有利于提高低温SCR催化性能;铜含量超过13%后,Cu含量的增加对催化剂的低温SCR催化活性影响不大,但将导致高温SCR催化性能急剧恶化;b4催化剂兼具良好的高、低温SCR催化性能,值得深入研究。     

镍改性ZSM-5催化剂及其SCR催化性能

采用液态离子交换法制备了不同负载量的镍改性ZSM-5分子筛催化剂,并考察了上述催化剂的微观结构和物理化学特性及其在NH3-SCR反应中的催化性能。结果表明:在负载量<10.9%时镍在分子筛中具有高度的分散性,而随着镍负载量的进一步增加,分子筛表面开始出现较大的NiO颗粒;镍元素只以+2价存在于分子筛催化剂中;在NH₃-SCR反应中,镍负载量低于14.9%时,增加镍负载量将提高催化剂的低温活性;当反应温度超过300℃时,高温催化中心开始起作用,但随镍负载量的增加,高温活性开始下降时的温度逐渐降低。     

Cr—MCM—48分子筛的催化活性研究

用掺杂Ｃｒ的ＭＣＭ－４８中介孔分子筛催化剂对α－二十醇催化氧化剂α－二十酸进行了考察研究了反应最佳温度和反应时间,并对目的反应的催化性能进行了评价。结果表明,添加适量的Ｃｒ可提高α－二十醇氧化成α－二十酸的收率。ＸＲＤ和ＩＲ技术表征结果表明,掺杂的Ｃｒ能进入ＭＣＭ－４８分子筛的骨架,反应产物的收率同分子筛催化剂的Ｌ酸相对含量有一定顺变关系,用红外光谱对目的产物进行了半定量分析。     

二氧化硅改性分子筛催化生物质基多元醇制备对二甲苯

本文证明了在二氧化硅改性的分子筛催化作用下,生物质基多元醇(如山梨醇、木糖醇、赤藓糖醇、甘油和乙二醇)可以经过催化裂解、烷基化和异构化等反应,生成高附加值的化学品(对二甲苯).与HZSM-5分子筛催化剂相比,二氧化硅改性的分子筛降低了分子筛催化剂的外表面酸和孔径,从而显著的提高对甲苯的选择性和产率.本文详细讨论了催化剂、甲醇添加剂、反应温度和不同类型多元醇原料对对二甲苯选择性和产率的影响.甲醇的添加促进多元醇催化裂解中的烷基化反应,提高了二甲苯的产率.在15%SiO_2/HZSM-5催化剂作用下,对二甲苯的产率最高可达到10.9 C-mol%,对二甲苯在二甲苯中选择性达到91.1%.本文通过研究相关重要反应和催化剂特性,揭示了生物质基多元醇催化裂解制备对二甲苯的反应路径.     

二氧化硅改性分子筛催化生物质基多元醇制备对二甲苯（英文）

本文证明了在二氧化硅改性的分子筛催化作用下,生物质基多元醇(如山梨醇、木糖醇、赤藓糖醇、甘油和乙二醇)可以经过催化裂解、烷基化和异构化等反应,生成高附加值的化学品(对二甲苯).与HZSM-5分子筛催化剂相比,二氧化硅改性的分子筛降低了分子筛催化剂的外表面酸和孔径,从而显著的提高对甲苯的选择性和产率.本文详细讨论了催化剂、甲醇添加剂、反应温度和不同类型多元醇原料对对二甲苯选择性和产率的影响.甲醇的添加促进多元醇催化裂解中的烷基化反应,提高了二甲苯的产率.在15%SiO_2/HZSM-5催化剂作用下,对二甲苯的产率最高可达到10.9 C-mol%,对二甲苯在二甲苯中选择性达到91.1%.本文通过研究相关重要反应和催化剂特性,揭示了生物质基多元醇催化裂解制备对二甲苯的反应路径.     

扫描ICP法测定催化剂Ⅰ——甲烷化催化剂中Ni、La和Mg的测定

前言催化剂的催化成分和担体的测定对催化剂的制备及性能鉴定是必不可少的。催化剂成份分析多采用化学分析方法;但繁琐费时。有人采用原子吸收光谱方法,但氧化铝、二氧化硅、硅胶、分子筛等担体对催化成分,(镍、铂、钼等)的干扰很严重,需预先分离基体或加入适当的释放剂。     

固体核磁共振技术在锡硅分子筛表征中的应用

生物质等绿色资源的高效转化利用是催化科学的重要发展方向.锡硅分子筛因具有优良的催化性能而得到相关研究者的普遍关注.准确构建催化剂活性中心结构/酸性与催化反应性能之间的构效关系是新型高效催化剂设计与研发的基础.固体核磁共振（NMR）是研究分子筛活性中心局域结构、酸特性与催化反应机理的重要手段.本文简述了近年来固体NMR技术在锡硅分子筛研究领域的一系列主要进展,并进行了展望.     

Cr-MnOx/堇青石催化剂制备及催化降解邻二氯苯性能研究

采用溶胶凝胶法、浸渍法、共沉淀法以及流变相法制备了新型 Cr-MnOx/堇青石催化剂,同时采用X射线衍射(XRD)、扫描电镜(SEM)、热重和差热分析(TG-DTA)、H2-程序升温还原(H2-TPR)以及元素能谱(EDS)技术对催化剂进行表征。经筛选发现,以共沉淀法制备的 Cr-MnOx/堇青石催化剂(Cr/Mn=2∶5)催化活性最高。通过表征结果可知,以共沉淀方法制备的催化剂主要活性成分为 Mn2 O3和 Cr2 O3,并且具有特殊的球形和较好的氧化还原性能,协同作用的存在有助于催化降解目标污染物邻二氯苯(o-DCB)性能的提高;在60 h之内,o-DCB降解率仍保持在80%以上,具有较好的催化稳定性。     

稀土改性的氧化镍基低温乙烷氧化脱氢催化剂活性氧物种的Raman光谱研究

利用共沉淀法制备了几种稀土金属氧化物改性的氧化镍催化剂 ,考察了其乙烷氧化脱氢 (ODE)制乙烯的催化性能 ,讨论了不同稀土金属氧化物掺杂浓度对催化剂催化性能的影响 ,利用Raman光谱技术初步表征反应在该类催化剂上的活性氧物种为Raman谱带出现在 1 0 60cm- 1 的表面双原子超氧物种O-2 ,该谱峰的大小与催化剂的ODE性能有很好的对应关系。     

铜钴铈复合体系对甲醇脱水催化性能的研究

以铜钴铈的氧化物为活性组分,对ZSM-5分子筛进行改性,用微反-色谱装置在线对甲醇脱水制二甲醚催化性能评价。从实验中可以发现：铜钴氧化物的摩尔分数之比为5：5,铈的摩尔百分含量为20%,450℃煅烧的催化剂的活性最高。     

Equilibrated thermodesorption studies of adsorption of n-hexane and n-heptane on zeolites Y, ZSM-5 and ZSM-11

Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur.     

ZSM—5分子筛生成中的模板效应：^13C—NMR对TBA^＋体系的研究

在合成一系列ZSM-5/11分子筛的基础上,用固体高分辨~(13)C-NMR技术考察样品中模板剂TBA~+的存在状态.讨论了TBA~+在ZSM-5和ZSM-11孔道中的分布方式,并发现了TBA~+的分解产物正丁胺的存在,从而说明了在SiO_2/Al_2O_3不十分高的体系中,TBA~+和正丁胺是ZSM-5共生晶相的模板剂。     

Physicochemical characteristics of ZSM-5/SAPO-34 composite catalyst for MTO reaction

SAPO-34 and ZSM-5 are the most well-known catalyst for MTO reaction. A combination of ZSM-5 and SAPO-34 might give rise to optimal catalyst to meet a change of market demand for ethylene, propylene and butadiene. In this study, we have developed ZSM-5/SAPO-34 composite catalysts to control the composition of light olefins in MTO reaction. ZSM-5/SAPO-34 composite catalysts showed very different physicochemical and catalytic properties with respect to ZSM-5 and SAPO-34 synthetic procedure. The physicochemical properties of the composite catalysts have been compared by XRD, SEM, N₂ isotherm, FT-IR and NH₃-TPD. Their catalytic performances were also evaluated for MTO reaction. The series composite catalyst synthesized by successive crystallization of SAPO-34 synthetic gel after ZSM-5 crystallization exhibited relatively high catalytic performance.     

Characterization of Copper-Modified ZSM-5 with Sorbed Pyridine Using Nuclear Magnetic Resonance Spectroscopy

Solid-state ¹H, ¹³C and ²⁹Si MAS NMR experiments were used to detect sorbed pyridine in hydrated copper-exchanged forms of synthetic zeolite ZSM-5, which is widely used in industry and green chemistry as well. The paper follows on from the previous study of sorption of organic pollutants by copper-modified forms of ZSM-5. Multinuclear MAS NMR experiments performed on hydrated and dehydrated copper-exchanged ZSM-5 samples with sorbed pyridine indicate that dissociation of water molecules in the vicinity of copper cations results in formation of new acid sites in the zeolite channels. Through their reaction with sorbed pyridine molecules, pyridinium ions are formed. ¹³C MAS NMR spectra also confirmed the presence of pyridine molecules not involved in forming pyridinium ions in the copper-modified ZSM-5 samples. From the changes in ²⁹Si NMR spectra, some slight changes in the structure of original copper-modified ZSM-5 after pyridine sorption can be also deduced.     

Facile synthesis of mesoporous ZSM-5 aided by sonication and its application for VOCs capture

Application of ultrasound power to the mother liquor is popular pretreatment for zeolite synthesis which offers a simple way of accelerating crystallization process and finetuning the properties of nanocrystalline zeolites. In this work, sonication-aided synthesis of mesoporous ZSM-5 at low temperature and ambient pressure was systematically studied, in an attempt to reach efficient and benign synthesis of zeolites with hierarchical pore structure, which has wide applications as catalysts and sorbents. The effects of sonication duration, power density, sonication temperature and seeding on the crystallization of ZSM-5 were investigated. The obtained samples were characterized by XRD, SEM, BET and VOCs capture. High quality mesoporous ZSM-5 can be obtained by a facile 5 d synthesis at 363 K, much faster than conventional hydrothermal synthesis. The reduced synthesis time was mainly attributed to the enhanced crystallization kinetics caused by the fragmentation of seeds and nuclei, while sonication radiation had little impact on the nucleation process. Compared with control sample, mesoporous ZSM-5 prepared by sonochemical method had higher surface area and mesoporosity which demonstrated improved adsorption performance for the capture of isopropanol.     

The improvement of gas-sensing properties of SnO<Subscript>2</Subscript>/zeolite-assembled composite

SnO₂-impregnated zeolite composites were used as gas-sensing materials to improve the sensitivity and selectivity of the metal oxide-based resistive-type gas sensors. Nanocrystalline MFI type zeolite (ZSM-5) was prepared by hydrothermal synthesis. Highly dispersive SnO₂ nanoparticles were then successfully assembled on the surface of the ZSM-5 nanoparticles by using the impregnation methods. The SnO₂ nanoparticles are nearly spherical with the particle size of ~?10 nm. An enhanced formaldehyde sensing of as-synthesized SnO₂-ZSM-5-based sensor was observed whereas a suppression on the sensor response to other volatile organic vapors (VOCs) such as acetone, ethanol, and methanol was noticed. The possible reasons for this contrary observation were proposed to be related to the amount of the produced water vapor during the sensing reactions assisted by the ZSM-5 nanoparticles. This provides a possible new strategy to improve the selectivity of the gas sensors. The effect of the humidity on the sensor response to formaldehyde was investigated and it was found the higher humidity would decrease the sensor response. A coating layer of the ZSM-5 nanoparticles on top of the SnO₂-ZSM-5-sensing film was thus applied to further improve the sensitivity and selectivity of the sensor through the strong adsorption ability to polar gases and the “filtering effect” by the pores of ZSM-5.     

Key factor affecting the structural and textural properties of ZSM-5/MCM-41 composite

ZSM-5/MCM-41 micro/mesoporous composite materials were synthesized by the hydrothermal technique with alkali-treated ZSM-5 zeolite as source of silica and aluminum and characterized by various physico-chemical techniques such as X-ray diffraction (XRD), nitrogen sorption at 77 K, transmission electronic microscopy (TEM), FTIR spectroscopy and NH₃ temperature programmed desorption (TPD) techniques. The effect of concentration of CTAB in the synthesis of these solids has been investigated, the mesopore volume, surface area and surface acidity decrease with increasing the concentration of CTAB. Increasing the CTAB concentration causes the recrystallization of zeolite ZSM-5 and it disadvantage the formation of mesoporous materials MCM-41. The catalytic activity of ZSM-5/MCM-41 materials has been evaluated in the Friedel–Crafts acylation of anisole with benzoyl chloride as alkylating agent. The results revealed the reaction to be influenced by surface area, pore volume and surface acidity.     

Methane non-oxidative aromatization on Mo/ZSM-5: Effect of adding triethoxyphenylsilanes into the synthesis system of ZSM-5

A series of ZSM-5 zeolites were synthesized by adding triethoxyphenylsilane (PTEOS) into the initial sol of the synthesis system. The samples were studied by XRD, SEM, N₂ adsorption-desorption and acid assessment of d₃-acetonitrile adsorption. Characterization results showed that the crystal size of the ZSM-5 zeolites could be adjusted in a certain range by introducing different contents of PTEOS. Besides, the resultant materials possess hierarchical porosity in addition to those micropores generated by the MFI channels. Moreover, supported Mo/ZSM-5 catalysts were prepared, and their catalytic performances were investigated in the methane non-oxidative aromatization. It was found that the Mo/ZSM-5 catalyst, bearing suitable crystal size and mesoporous characteristic showed relatively high shape-selectivity to benzene and high stability for the reaction of methane aromatization.     

PVDF–PEO/ZSM-5 based composite microporous polymer electrolyte with novel pore configuration and ionic conductivity

A novel composite microporous polymer electrolyte based on poly(vinylidene fluoride), poly(ethylene oxide), and microporous molecular sieves ZSM-5 (denoted as PVDF–PEO/ZSM-5) was prepared by a simple phase inversion technique. PEO can obviously improve the pore configuration, such as pore size, porosity, and pore connectivity of PVDF-based microporous membranes, results in a high room temperature ionic conductivity. Microporous molecular sieves ZSM-5 can further improve the mechanical strength of PVDF–PEO blends and form special conducting pathway in PVDF–PEO matrix by absorb liquid electrolyte in its two-dimensional interconnect channels. The high room temperature ionic conductivity combined with good mechanical strength implies that PVDF–PEO/ZSM-5 based composite microporous polymer electrolyte can be used as candidate electrolyte and/or separator material for high-performance rechargeable lithium batteries.