铁铝柱撑酸化蒙脱土催化剂的表征及催化性能

为改善柱撑蒙脱土的催化活性,对蒙脱土进行酸预处理,并采用离子交换法制备铁铝柱撑酸化蒙脱土(Fe-Al-酸化土)催化剂,通过XRD、BET、ICP和FI-IR对其进行表征。结果表明,蒙脱土经酸化预处理制备Fe-Al酸化土催化剂比表面积为157.3 m~2·g~(-1),层间距d001为1.787 nm,铁铝柱撑剂进入酸化蒙脱土层间域形成均一稳定的Si—O—Fe结构,在2 930 cm-1处出现尖锐的吸收峰,在协同过氧化氢降解废水实验中表现出较高的活性和稳定性。     

蒙脱土负载型固体酸催化剂的烷基化性能与结构研究

以酸化后蒙脱土为载体，采用浸渍蒸发法制备了环境友好的蒙脱土负载znCl2型固体酸催化剂。研究了蒙脱土酸化处理、ZnCl2负载量及活化温度对催化剂烷基化活性的影响，并初步考察了催化剂的稳定性，比较了几种不同酸催化剂的烷基化活性。利用XRD、BET、TG—DTA、吡啶吸附FTIR对催化剂的结构进行了表征和测定；结果表明，蒙脱土酸化处理后形成的孔道有利于负载ZnCl2，ZnCl2与蒙脱土的羟基之间存在着化学键合，经活化后转化成Zn(0H)C1。蒙脱土负载ZnCl2后明显地提高蒙脱土表面的总酸量，催化剂活性与其表面总酸量之间有关，催化剂表面L酸与B酸的共存有利于其烷基化活性的提高。实验条件下，蒙脱土负载ZnCl2型催化剂在苯与氯节的烷基化反应中表现出较高的催化活性，二苯甲烷的收率最高可达83．6％。与其它Lewis酸试剂及酸化蒙脱土相比，蒙脱土负载型催化剂催化活性大有提高。     

表面活性剂改性的铝交联蒙脱土的表征及催化性能

以聚乙烯醇为支撑前体，合成了一类新型的表面活剂改性的铝交联蒙脱土。通过ＸＲＤ，低温Ｎ２脱吸附分析，骨架振动红外光谱等手段的表征及对催化转化柴油为汽油的测试，表明热稳定性与催化活性传统的铝交联蒙脱土都有显著提高。     

铝交联蒙脱土结构影响因素的研究

利用电镜、比表面仪和X射线衍射分析方法表征了制备的铝交联蒙脱土。结果表明,OH^-与Al^3+物质的量比、焙烧温度和酸化浓度对交联蒙脱土结构有一定影响,交联剂陈化时间对酸化交联蒙脱土的收率也有影响,最佳条件:n(OH^-)∶n(Al³⁺)=2.2,焙烧温度65 ℃,酸化浓度5%～20%,交联剂陈化时间1.5天。     

蒙脱土负载［C14mim］+有机阳离子催化合成柠檬酸三丁酯

通过咪唑基离子液体和蒙脱土在甲苯溶液中的离子交换反应，将热稳定性高的咪唑基有机阳离子［C₁₄mim］⁺交换吸附进入蒙脱土片层间，制备了蒙脱土负载的有机阳离子固体催化剂［C₁₄mim］⁺/MMT。利用XRD和TGA对催化剂的结构与性能进行了表征和测定，研究了蒙脱土负载有机阳离子固体催化剂的催化性能，初步考察了其稳定性及再次使用效率。研究结果表明，［C₁₄mim］⁺/MMT在合成无毒增塑剂柠檬酸三丁酯的酯化反应中表现出较高的催化活性，可循环使用。与未负载的C₁₄mimBF₄相比，［C₁₄mim］⁺/MMT具有催化活性高、稳定性好和易分离的特点。     

蒙脱土改性催化材料的研究进展

改性蒙脱土是一种用途广泛的催化新材料。分别介绍了酸化蒙脱土酸催化剂、交联蒙脱土催化剂、蒙脱土中孔异构催化材料等的制备、结构及催化应用研究。     

改性交联蒙脱土催化合成乙酸丁酯

对交联蒙脱土酸处理产物进行了X射线衍射、电镜和比表面积分析。当酸化浓度为15%时,d₀₀₁=1.25 nm,比表面积229 m²·g^-1。用合成的酸化交联蒙脱土作催化剂,以正丁醇和冰醋酸直接酯化合成乙酸丁酯,用正交试验方法探索了合成的较佳工艺条件,结果表明,当酸化浓度为15%时,催化活性最高,当n(醇)∶n(酸)=1∶1.3,w(催化剂)=3%,反应时间 2.5 h,醇的酯化率达到98%以上。     

铝层柱蒙脱土的制备研究

采用铝交联剂交联蒙脱土,制备了不同Al/MMT配比的铝层柱蒙脱土,并采用XRD、吡啶吸附红外进行了表征,研究了铝层柱蒙脱土的水热稳定性及其表面酸性.研究表明,在500℃下焙烧8～12 h,有效改善了Al-MMT蒙脱土的水热稳定性,铝层柱蒙脱土酸类型和酸强度可以通过改变铝与蒙脱土的配比来实现.     

贫燃条件下铜离子改性铝交联蒙脱土汽车尾气净化催化剂的研制

以铝交联蒙脱土为载体,研制铜离子改性铝交联蒙脱土催化剂,在贫燃条件下考察其选择性还原NO的催化活性,并与Cu/ZSM-5做了比较。结果表明:采用浸渍法Cu2+负载量以w(Cu2+)=3%为最佳,可使NO转化率达52 25%;采用SO2-4改性能较大幅度提高催化活性,使NO转化率提高15 42%,同时能使操作温度范围更宽,500℃NO转化率仍达到22 16%,优于Cu/ZSM-5。     

星点设计-效应面法优化制备右旋布洛芬/酸改性蒙脱土

以右旋布洛芬为原料,酸化蒙脱土为药物载体,制得右旋布洛芬/酸改性蒙脱土S(+)-IBU/acid-MMT干混悬剂。通过星点设计-效应面法优化右旋布洛芬/酸改性蒙脱土干混悬剂的制备工艺。以蒙脱土的载药量为考察指标,采用三因素五水平星点设计考察了盐酸浓度、酸化时间、酸化温度对干混悬剂制备工艺的影响,并对结果进行了二元多项式线性回归方程拟合,经效应面法预测最佳处方;借助XRD和SEM技术对干混悬剂进行了结构表征。结果表明,右旋布洛芬/酸改性蒙脱土干混悬剂最佳制备条件为:盐酸浓度3.3 mol/L,酸化时间5.2 h,酸化温度54℃,在该条件下,干混悬剂载药量可达443.7 mg/g,较优化前(352.4 mg/g)提高了25.9%。星点设计-效应面法适用于右旋布洛芬/酸改性蒙脱土干混悬剂制备工艺优化,以该方法建立的数学模型具有良好的预测性,所得干混悬剂具有更高的载药量。     

Effect of pillared clays on the hydroisomerization of n-heptane

Different montmorillonites and saponites were pillared with Al polyoxocations to obtain catalytic supports for the hydroisomerization of n-heptane. The catalysts were characterized by different techniques such as X-ray diffraction, elemental analysis and N₂ adsoprtion. The temperature-programmed desorption of ammonia indicated that pillared clays exhibited moderate and strong acid sites. The concentration of the acid sites depended on the starting clays as well as the type of the clays. The pillared saponites are more effective for the hydroisomerization of n-heptane at 300 °C, however, it decreased over the Al-pillared montmorillonites, and mainly cracking products were obtained.     

Effect of the Si/Al ratio on the structure and surface properties of silica-alumina-pillared clays

In the present work, the synthesis of silica-alumina-pillared montmorillonites and their structure are studied. Hydroxy-silico-aluminum oligocations have been obtained by treating previously synthesised aluminum polycations with Si(OC₂H₅)₄. Several Si/Al ratios (0, 0.5, 1, and 2) have been used to prepare pillared clays with various microporous accessibility and acidic properties. The study of the fractal dimensions of the solids shows that their surface becomes more heterogeneous after pillaring. The acidity of alumina- and silica-alumina-pillared montmorillonites is mainly of the Lewis type, and the nature of the acid sites detected by pyridine adsorption seems to be independent of the Si/Al ratio. These results are supported by the product distribution obtained in the 1-butanol dehydration reaction.     

水中硝基苯在柱撑膨润土上的吸附行为

在［OH^-］/［Al³⁺］=2.4的反应条件下,利用Al³⁺与碱液反应制备出Keggin离子,并由此制备出了无机、无机-有机柱撑膨润土,XRD-衍射数据表明,经柱撑后的膨润土层间距明显增大,达1.9 nm以上.研究了硝基苯在4种改性膨润土上的吸附行为,结果表明：经柱撑处理后的膨润土吸附能力明显大于钠基土,其吸附动力学行为遵循Bingham方程和Langmuir方程所描述的规律,平衡吸附量q_e与平衡浓度C_e之间的关系符合Freundlich和Langmuir等温吸附方程,吸附表现为放热的物理吸附和有机质的分配作用.     

Synthesis of Smectites and Porous Pillared Clay Catalysts: A Review

This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal/Al pillared clays. The use of these pillared clays in some catalytic reactions is also briefly reviewed.     

改性蒙脱土的研究进展

改性蒙脱土是近年来受国内外学者广泛关注的矿物材料之一,由于其层间的特殊结构而被广泛应用于吸附、催化等领域。概括介绍了蒙脱土的结构和基本性质,重点讨论了蒙脱土改性方法和机理。对无机改性、有机改性和有机一无机复合改性分别作了论述,并展望了其应用前景。     

Isomerization of 1-butene catalyzed by ion-exchanged,pillared and ion-exchanged/pillared clays

A natural smectite clay (STx-1, USA) was ion-exchanged with Al, Fe or pillared with polyoxocations of the same metals. Samples were also prepared by combining these two treatments. The prepared solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), TPD of ammonia and N₂ adsorption. The catalytic activity was evaluated by using the isomerization of 1-butene at 300 °C. XRF results showed an increase in the content of Al or Fe thus giving evidence that these metals were effectively exchanged or deposited over the starting material. Al- and Fe-pillared clays showed a significant increase of the surface area. Ion-exchanged clays showed similar surface areas to that of the starting clay. From XRD patterns only the Al-pillared clay gave an increase of the d-spacing. The synthesized pillared clays were superior catalysts for the isomerization of 1-butene than the ion-exchanged clays; the ion-exchanged/pillared clays showed a similar catalytic behavior as that of the parent pillared clays. The Al-pillared clay was the best catalyst for the reaction and its efficiency was related to the high acidity and high surface area.     

Synthetic organic chemistry using pillared, cation-exchanged and acid-treated montmorillonite catalysts — A review

This review is concerned with the use of pillared, cation-exchanged and acid-treated montmorillonites as catalysts for reactions which can be carried out on a preparative laboratory or industrial scale. Most notably the clays display Brønsted and Lewis acid activities, but Diels-Alder reactions can also be effected using these materials. An introduction covers the basis of the various types of catalytic activity and gives some experimental details, while the main body of the text reviews reaction types, giving typical conditions and yields.     

Acidity and catalytic activity of the mesoporous aluminosilicate molecular sieve MCM-41

The acidity and catalytic properties of aluminosilicate mesoporous molecular sieves with the MCM-41 structure and bulk Si/Al ratios in the 10–60 range have been investigated. The incorporation of 4-coordinate aluminium into the structure of MCM-41 generates both BrØnsted and Lewis acid sites in amounts increasing with the degree of incorporation. However, the BrØnsted/Lewis acid population ratio is independent of the content of aluminium. The number and strength of acid sites generated are comparable to those of a pillared acid-activated clay and lower than in zeolite H-Y with Si/Al=3.65. Aluminosilicate MCM-41 is a moderate catalyst for the conversion of cumene which proceeds predominantly via catalytic cracking to propene and benzene. The sample of MCM-41 with the highest content of framework aluminium (Si/Al=10) has the largest number of BrØnsted acid sites and exhibits highest catalytic activity.     

Selective Methyl <Emphasis Type="Italic">Tert</Emphasis>-Butyl Ether Synthesis over Metal Exchanged Pillared Clays

Iron and mixed iron aluminium pillared montmorillonites prepared by partial hydrolysis method was subjected to room temperature exchange with transition metals of the first series. The materials exhibit good structural as well as thermal stability. Exchanged metals were found to be present inside the porous network, in the environs of the pillars. Mixed pillaring resulted in the intercalation of Al₁₃ like polymers in which Al is partially substituted by Fe. The acidic structure was followed by temperature programmed desorption of ammonia and cumene cracking test reaction. Weak and medium sites overshadow the strong sites in all systems. However, exchange with metals increases the number of strong sites. The prepared materials are efficient catalysts for gas phase MTBE synthesis. The catalytic activity can be well correlated with the total amount of weak and medium acid sites.     

Selective catalytic reduction of NO by NH3 on titanium pillared montmorillonite

The acidity of a titanium pillared montmorillonite (Ti-PILC) has been modified by two methods of sulfation. The acidic properties of these pillared clays have been studied by temperature-programmed ammonia desorption and FTIR analysis of pyridine adsorption. The catalytic activity of these titanium pillared clays in the selective catalytic reduction (SCR) of NO by NH₃ with or without SO₂ has been investigated. For the three titanium pillared clays, a high resistance to SO₂ presence has been observed.