改性ZSM-5催化剂在甲苯、甲醇烷基化制备对二甲苯技术的研究进展

甲苯甲醇烷基化反应是制备对二甲苯的一条新的工艺路线,因原料甲苯和甲醇价格低、产物选择性高而仅采用结晶分离可得到高纯度的对二甲苯、投资少等优点,引起研究者的极大关注.从非金属改性、金属和非金属元素同时改性、催化剂研究新思路3个方面综述了国内外有关改性ZSM-5分子筛催化剂在甲苯、甲醇烷基化技术的研究进展状况.     

Benzene alkylation with methanol over phosphate modified hierarchical porous ZSM-5 with tailored acidity

The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification.The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus.Meanwhile,side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently.The acid strength and sites amount of Br(o)nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene,whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.     

Removal of Thiophene from Coke-Chemical Benzene by Liquid Adsorption on Modified ZSM-5 Synthetic Zeolite

1 INTRODUCTIONIt is of great importance to remove thiophene to obtain a highly-purified benzene product.Anumber of methods practiced in industry involve the catalytic sulfuric acid desulfurization and/orcatalytic hydrodesulfurization.With catalytic sulfuric acid desulfurization,large quantities of ef-fluent which contaminate to the environment are being discharged in addition to acid corrosionon process equipment.Whereas,high capital investment and more stringent operating condi-     

Removal of Thiophene from Coke-Chemical Benzene by Liquid Adsorption on Modified ZSM-5 Synthetic Zeolite

1 INTRODUCTION It is of great importance to remove thiophene to obtain a highly-purified benzene product. A number of methods practiced in industry involve the catalytic sulfuric acid desulfurization and/or catalytic hydrodesulfurization. With catalytic sulfuric acid desulfurization, large quantities of effluent which contaminate to the environment are being discharged in addition to acid corrosion on process equipment. Whereas, high capital investment and more stringent operating conditions appear to be the major drawbacks of the catalytic hydrodesulfurization.     

ZSM-5沸石分子筛吸附模拟废水中对苯二酚的研究

以正硅酸乙酯为硅源、偏铝酸钠为铝源、四丙基氢氧化铵为模板剂,利用水热合成法制备ZSM-5沸石分子筛并将其应用到吸附水中对苯二酚的研究,考察了吸附时间、对苯二酚溶液pH值、吸附温度、吸附剂用量对吸附效果的影响。结果表明,最佳吸附条件是:吸附温度为35℃,吸附时间为60 min,对苯二酚溶液pH值为6,吸附剂用量为0.4 g。此时,对苯二酚的去除率最高,达到了68.28%。     

ZSM-5沸石合成与改性技术进展

ZSM-5沸石在石油化工过程中得到广泛应用。阐述了ZSM-5沸石的合成、改性技术现状及其应用以及近年来的研究和开发应用最新进展，为ZSM-5沸石的开发利用提供新的思路。     

ZSM-5沸石的改性及其在烷基化反应中的应用进展

ZSM-5沸石在石油化工中的应用非常重要。本文对ZSM-5沸石的改性技术的现状及其近年来在烷基化反应中的开发应用的最新进展进行了综合阐述,ZSM-5沸石的应用已取得了一定的成果,为其今后的开发利用提供了新的思路。     

ZSM-5 型沸石膜反应器在乙苯脱氢反应中的模式

引言 沸石分子筛膜是近些年发展起来的和种新型的膜分离技术[1],它是通过分子筛孔道实现分子筛分,从而得到较高的分离因数.     

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.     

氢氧化钠改性ZSM-5分子筛的碳四烯烃催化裂解性能

用不同浓度的氢氧化钠溶液对ZSM-5分子筛进行改性,以X射线衍射(XRD)、扫描电镜(SEM)、氪-程序升温脱附(NH_3-TPD)和N_2吸附方法对改性后的催化剂进行表征,并考察了改性后的ZSM-5分子筛催化剂在碳四烯烃裂解反应中的催化性能。结果表明,氢氧化钠改性没有破坏该分子筛骨架结构,改性后催化剂的酸量、介孔孔径、介孔孔容和比表面积BET都有所增加,从而改善了催化剂的反应性能。氢氧化钠溶液的浓度为0.4 mol/L比较合适,用该浓度的氢氧化钠改性后的ZSM-5分子筛催化剂0.4AT-HZ在550℃和常压下进行碳四烯烃催化裂解反应。具有较高的稳定性,丁烯转化率可达到78%以上,丙烯收率大于38%,丙烷收率为7%。     

Adsorption of alcohols from aqueous solution by ZSM-5

Isotherms have been measured for the adsorption from aqueous solution of water soluble alcohols onto the zeolite ZSM-5. For methanol and ethanol the amount of alcohol adsorbed increases with increasing percentage of Al₂O₃, whereas for n-butanol the amount adsorbed decreases as the amount of Al₂O₃ increases. Adsorption of alcohols is also dependent on the cation form. For the alkali metal ion forms, the amount of alcohol adsorbed decreases as the ionic size increases, the effect being particularly pronounced for Cs⁺. Subsequent alcohol desorption was studied by thermogravimetry and mass spectrometry which showed that the zeolite retained a portion of the alcohol to temperatures (ca 250°C) sufficiently high that catalytic breakdown occurred. This reduces its likely potential for commercial alcohol concentration.     

ZSM-5沸石分子筛吸附模拟含铬废水的研究

本论文以正硅酸乙酯为硅源、偏铝酸钠为铝源、四丙基氢氧化铵为模板剂,利用水热合成法制备ZSM-5沸石分子筛并将其应用到吸附水中六价铬的研究,考察了吸附时间、铬酸钾溶液pH值、吸附剂用量、吸附温度对吸附效果的影响。结果表明,最佳吸附条件是:吸附剂的使用量为0.5g,铬酸钾溶液pH值为5,吸附时间为60 min,吸附温度为30℃,此时,六价铬的去除率最高,达到了93.46%。     

水在ZSM-5型分子筛中吸附的Monte Carlo模拟

构建了ZSM-5型分子筛物理模型,采用Connoly表面方法和Solvent表面方法对ZSM-5型分子筛的几何结构和性质进行了模拟分析。通过巨正则系综蒙特卡罗方法(GCMC)模拟研究了水蒸气在ZSM-5型分子筛上的吸附特性。通过模拟方法看到了实验难以表征的水蒸气在分子筛中具体吸附位,研究了压力、温度和硅铝比对ZSM-5型分子筛吸附性能的影响及其吸附热的变化规律。     

Deactivation of ZSM-5 additives in laboratory for realistic testing

ZSM-5 deactivates differently from Y zeolite. Dealumination of Y zeolite during deactivation causes UCS shrinkage and thereby decline in activity and changes in selectivity. For ZSM-5 instead deactivation removes alumina from the zeolite structure, but in spite of that the zeolite structure does not collapse. Therefore, deactivation causes activity decline due to loss of active alumina sites, but no significant changes in the strength and separation between acid sites. Unlike with FCC catalyst, physical properties of ZSM-5 additive do not change significantly with deactivation and surface area and pore volume measurements cannot be used as indications of additive performance. Yet, since both Y and ZSM-5 are used simultaneously in practice, the information on the relative rates of deactivation between the two zeolites is very important. Therefore, the question remains, what is the best way to deactivate and test ZSM-5 additives in the laboratory to obtain realistic performance, e.g. propylene yield and to obtain proper ranking of various additives. This paper discusses the effect of deactivation conditions as well as performance testing aspects of ZSM-5 additives. It is shown that choice of deactivation conditions has an effect on additive ranking and performance. By choosing the deactivation conditions properly ranking can be made clearer and more realistic additive performance is obtained.     

Synthesis of ZSM-5 zeolite from expanded perlite and its catalytic performance in FCC gasoline aromatization

A hydrothermal synthesis method for ZSM-5 preparation was investigated by using expanded perlite as the only alumina source. The effect of crystallization conditions on ZSM-5 zeolite formation, such as temperature, time, pH, chemical composition of the reaction mixture, were studied. The samples were characterized by XRD, IR, SEM, XRF and BET surface area measurements. The ZSM-5 zeolite from expanded perlite showed better catalytic activity for the FCC gasoline aromatization reaction compared to ZSM-5 prepared by the standard method.     

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.     

Estimation of crystalline phase in ZSM-5 zeolites by infrared spectroscopy

A fast and accurate method for identification and determination of purity of Zeolite Socony Mobil 5 (ZSM-5) zeolite was developed using the IR optical density ratio of the bands at 550 and 450 cm^?1 in the mid-IR region of the structure spectra. The optical density values obtained from the proposed method, for ZSM-5 zeolite synthesized, are compared with those of the Bayer ZSM-5 zeolite used as reference material. For well-crystallized calcined ZSM-5 zeolite, this ratio is circa 0.8. This ratio is found to be less, if amorphous silicate is present in zeolite. The presence of a band at 550 cmSUP>?1 in addition to the one at 450 cm^?1 shows that ZSM-5 zeolite has been formed even if the material is X-ray amorphous. The absence of the structure-sensitive band at 550 cm^?1 unambiguously indicates that such a zeolite has not been formed.     

Control of acid-site location of ZSM-5 zeolite membrane and its application to the MTO reaction

ZSM-5 zeolite membrane, which shows high selectivity toward olefins in the methanol conversion, was developed by controlling the location of the acid sites. First, the ZSM-5 zeolite catalyst membrane without pinholes was successfully prepared by synthesizing a ZSM-5 zeolite layer on an outer surface of a cylindrical alumina ceramic filter. The membrane was used as the catalytic membrane reactor to recover olefins from methanol. Though the olefins were successfully produced from methanol with high selectivity (ca. 80%), production of paraffin and aromatics was observed at the feed side of the zeolite membrane. To prevent the such production, the location of the acid site of the ZSM-5 zeolite membrane was controlled by a new method called the catalytic cracking of silane (CCS) method. Selective deactivation of acid sites at the outer surface of the zeolite membrane (feed side of reactant) by the CCS method allowed us to increase the selectivity of the olefins by 10% as compared to the untreated membrane.     

Synthesis of ZSM-5 coatings on stainless steel grids and their catalytic performance for partial oxidation of benzene by N2O

The one step hydroxylation of benzene has been performed over structured catalytic bed made of ZSM-5 coatings grown by hydrothermal synthesis on stainless steel grids. The catalysts demonstrated a 97% selectivity towards phenol formation at benzene conversion of 11%. In addition of achieving the same reactivity as over the traditional zeolitic fixed beds, these new catalytic packings present several advantages gained from the special arrangement of the catalytic bed like low pressure drop, improved heat and mass transfer, and controlled hydrodynamics.     

ZSM-5沸石对水溶液中铅离子的吸附性能

研究了ZSM-5沸石对水溶液中铅离子（Pb^2＋）的吸附性能,考察了Pb^2＋初始浓度、吸附剂用量、pH值和吸附时间等因素对吸附的影响。结果表明：ESM-5沸石对水溶液中铅离子有较好的去除效果,当其用量为40g／L时,水溶液中铅离子的吸附去除率达到96．09％;吸附过程在180min时达到吸附平衡;溶液pH值和初始浓度对水溶液中铅离子的去除也有显著的影响,中性和碱性条件下的去除率大于酸性时的去除率;平衡吸附量与吸附平衡浓度之间的关系较好符合Freundlich和Langmuir等温吸附方程所描述的规律。