铌酸催化剂的结构和酸性催化性质

研究了铌酸催化剂的制备方法、表面酸性及晶体结构对乙醇和乙酸酯化反应的影响。结果表明，热处理温度对水洗法制备的铌酸催化剂的催化性能有显著的影响，经３５０℃热处理后其达到活性极大值。并发现催化性能受热处理温度影响的原因是铌酸结构中含水量及比表面积随热处理温度变化而导致铌酸表面酸性的变化，而与氧化铌的形态和晶体结构无明显关系。     

新型MCM-41固载化铌酸催化氧化环戊烯制备戊二醛

通过可溶的草酸配合物将铌酸固载到中孔分子筛MCM-41上，得到含催化氧化活性中心的Nb2O5／MCM-41负载型催化剂，并用XRD，BET，N2吸附等手段进行了表征．该催化剂在环戊烯催化氧化制备戊二醛的反应中表现出优良的催化性能，环戊烯的转化率高达100％，戊二醛收率达到50％，展现了良好的应用前景．     

在铌酸催化剂上气相酯化反应的研究

氧化铌在含水体系中表现出强酸性,因而得到越来越多的应用。有机羧酸酯是一类重要的化工产品,一般用硫酸等作催化剂,但存在腐蚀设备等问题。我们采用铌酸催化剂进行乙醇和6种羧酸的常压气相酯化反应。实验表明,不仅乙醇转化性高,而且酯的选择率高达100％,同时,也克服了上述液体酸催化剂的缺点,有希望成为酯化反应的有效催化剂。     

固体铌酸催化下甲苯的硝化

在不同焙烧温度下制备了一系列固体铌酸催化剂。测定了固体铌酸催化剂的比表面积、表面酸强度及表面酸量。研究了催化剂焙烧温度、硝化反应时间、硝化反应温度、有无醋酐存在、硝酸浓度、催化剂的重复使用等因素对甲苯硝化反应影响。实验结果表明,当反应温度为40℃,反应时间为60 min时,以CCl4为溶剂,以质量分数为95%的硝酸为硝化剂,在醋酐存在条件下,以经300℃焙烧3 h后的铌酸作为催化剂,甲苯硝化产物中异构体的邻对比达1.26,较硝硫混酸的1.67显著降低,产物得率达99.3%。且该催化剂循环使用5次,催化活性基本不变,是一种极具应用前景的绿色硝化反应催化剂。     

Keggin结构过氧铌钨磷杂多配合物的合成、表征及催化性能

钼钨的杂多化合物（HPC）在催化、电催化、分子材料、药物等诸多领域中已显示出独特的功能。含过氧金属离子取代的杂多阴离子在催化以过氧化氢为氧化剂的烯烃环氧化反应中具有很高的活性和选择性。近年来，含铌的杂多配合物由于良好的催化活性和抗病毒性，引起了人们的重视。本文合成了8种Keggin结构过氧铌钨磷杂多配合物，并用红外、紫外吸收光谱、极谱-循环伏安、及^183W NMR谱等测试手段对其结构和性质进行了确定和比较，考察了它们对烯烃环氧化反应的催化活性。     

铌酸催化液相合成乙酸乙酯

报道了铌酸催化乙醇与乙酸的液相酯化反应考察了反应温度、催化剂用量、酸醇比、反应时间对产品乙酸乙酯经的影响。在优化条件下,产品收率棕达８８．０％,选择性为１００％,同时我们采用自制间式反应,对催化剂的稳定性进行了考察,发现铌酸在该实验条件下,能保持较高的稳定性和较高的催化活性。     

铌钼杂多酸的极谱行为及其应用于铌的测定

在ｐＨ２．５的硫酸、抗坏血酸溶液中，铌与钼形成了具有电活性的铌钼蓝杂多酸，并在ｐＨ８．８的ＮＨ３－ＮＨ４Ｃｌ溶液中可在滴汞电极上于－１．１０Ｖ（ｖｓ．ＳＣＥ）产生一灵敏的还原波。导数波高与铌量在０．００５￣０．４ｍｇ／Ｌ范围内呈线性关系。研究了极谱波性质，证明其为吸附波，电极反应属于准可逆。求得电极反应中电子转移数及质子转移数均为２。应用本法已测定了合金钢标样中的铌。     

铌和过氧铌取代Dawson结构钨磷杂多配合物的氧化还原性质研究

本文用电化学方法研究了铌和过氧铌一、三取代Ｄｗｓｏｎ结构杂多配合物：ａ２－ＭａＨｂＰ２Ｗ１５ＮｂＯ６２．ｘＨ２Ｏ，ａ－１，２，３－ＭａＨｂＰ２Ｗ１５Ｎｂ３Ｏ６２．ｘＨ２Ｏ，ａ２－ＭａＨｂＰ２Ｗ１７（ＮｂＯ２）Ｏ６１．ｘＨ２Ｏ，ａ－１，２，３－ＭａＨｂＰ２Ｗ１５（ＮｂＯ２）３Ｏ５９．ｘＨ２Ｏ（Ｍ＝Ｋ，ＴＭＡ，ＴＥＡ和ＴＢＡ）共十六种盐的氧化还原性质。     

铌酸催化合成环己酮1,2-丙二醇缩酮

将铌酸应用于催化缩酮反应，以环己酮和1，2－丙二醇的缩酮反应为探针，详细探索了影响缩合反应的各种因素，并得出了铌酸催化环己酮与丙二醇反应的最佳条件：mol环己酮：mol丙二醇＝1：1.5，环己烷作带水剂，环己烷和铌酸催化剂的用量分别为反应物总体积、总质量的35％和1．2％，回流搅拌反应3.5h，产品环己酮1，2－丙二醇缩酮的总收率为73．5％。     

铌酸锰-还原氧化石墨烯复合光催化剂的构建以及可见光下降解亚甲基蓝

通过水热法和光还原方法成功地制备了铌酸锰-还原氧化石墨烯复合光催化剂。这种复合光催化剂可以明显地提高光催化降解亚甲基蓝的光催化活性,降解效率在60 min内达到了78.2%,是单体铌酸锰降解效率的2倍。通过活性物质捕获实验的研究,增强的光催化性能可以归因于还原氧化石墨烯加速了光生电子-空穴的分离效率,进而解决了低光催化活性的问题。     

Crystallization and relative stabilities of Polymorphs of Niobium(V) Oxide under hydrothermal conditions

The TT-, T-, B-, P-, and poorly ordered M-forms of niobium(V) oxide were crystallized hydrothermally by treating niobic acid with pure water and acids such as hydrochloric acid, nitric acid, and sulfuric acid at 250–750°C and 15–100MPa. Triniobium chloride heptaoxide was hydrolyzed in pure water and acids solutions at 250–500°C and 15–98MPa, producing the P-, R-, and B-forms. The formation of the above polymorphs involved either dissolution-precipitation or the solid-phase rearrangement of the structures of amorphous solids. The B-form was shown to be the most stable phase below 760°C by an isothermal-conversion method. The relative stabilities of seven polymorphs of niobium(V) oxide were estimated by observing the rates of conversion of metastable forms into the B-forms in 1.2 mol/dm³ hydrochloric acid.     

Synthesis of lead metaniobate by thermal decomposition of a coprecipitation product

The paper reports a new, nonconventional method for the preparation of oxygen-containing niobium compounds, based upon coprecipitation. The coprecipitation product of niobic acid with lead oxalate was used as precursor. Lead metaniobate was obtained by proper thermal treatment of the coprecipitate. The coprecipitate mechanism was studied and the optimal conditions for quantitative precipitation of niobium and lead were established. The mechanism of thermal decomposition of the coprecipitate was investigated by differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, lead metaniobate, is formed at 850°C.     

Synthesis of calcium metaniobate by thermal decomposition of a coprecipitation product

The paper presents a new, nonconventional method, based upon coprecipitation, for the synthesis of niobium oxidic compounds. The coprecipitation product of niobic acid with calcium oxalate was used as precursor. Calcium metaniobate was obtained by appropriate thermal treatment of the coprecipitate. The coprecipitation mechanism was studied and the optimal conditions for quantitative precipitation of niobium and calcium were established. The mechanism of thermal decomposition of the coprecipitate was investigated by means of differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, calcium metaniobate, is formed at 730°C.     

铌酸液相催化酯化

首次以丙酸与乙醇的酯化反应为探针反应,探索了铌酸液相催化合成丙酸乙酯的适宜条件.在优化条件下,酯收率达91.5%.     

Low-temperature synthesis of niobium oxide nanoparticles from peroxo niobic acid sol

A peroxo niobic acid sol was prepared by peptization of the niobic acid precipitate (Nb2O5.nH2O) with a H2O2 aqueous solution. Crystallized Nb2O5 nanoparticles and niobic acid nanoparticles were obtained by heating the peroxo niobic acid sol. When peroxo niobic acid sol prepared by peptization of the niobic acid precipitate ([NH3]=0.3 mol/l) was heated at 348 K for 1 week, Nb2O5 nanoparticles with a diameter of 4.5 nm and a S(BET) of 275 m2/g were obtained. When peroxo niobic acid sol prepared by peptization of the niobic acid precipitate ([NH3]=1 mol/l) was heated at 348 K for 1 week, niobic acid nanoparticles with a diameter of less than 2 nm were obtained. The pore structure and degree of crystallinity of the nanoparticles prepared by heating the peroxo niobic acid sol greatly depended on the concentration of the ammonia solution used for preparing the niobic acid precipitate.     

外延定向生长氧化铌模型催化剂的制备

为用现代表面科学技术研究金属氧化物催化剂，在Pt（111）上于超高真空系统中原位蒸镀制备了NbO、NbO2、NbO2、单晶薄膜（＞2nm）．通过AES、ISS、LEED、ILS等手段研究了单晶薄膜的成长模式、化学计量和几何结构．表明通过选择合适的废物和控制制备条件，可制备出确定结构的金属氧化物单晶薄膜表面作为体相氧化物催化剂的模型表面．这种方法克服了电子能谱技术研究金属氧化物表面的困难，为研究金属氧化物催化剂的表面化学物理性质提供了方法     

Amphiphilic NaY zeolite particles loaded with niobic acid: Materials with applications for catalysis in immiscible liquid-liquid system

The catalytic potential of catalysts for acid-catalyzed reactions has been demonstrated by NaY zeolite loaded with alkylsilane-covered niobic acid in the liquid phase hydration of 1,2-epoxyoctane with water. The catalytic activity of the catalysts was correlated to the amphiphilic character of the solid catalyst particles. This revised version was published online in August 2006 with corrections to the Cover Date.     

铌酸催化的苯甲醛与甲醇缩合反应

采用铌酸为催化剂,探索了该催化剂对苯甲醛与甲醇缩合反应的影响.优化反应条件是,催化剂用量为反应物质的量的5mol%,甲醇10mL(兼作溶剂),回流状态下反应2h,反应的产率和转化率分别达到94%、98.0%.该催化剂同样适用于其他醛(酮)与甲醇的缩合反应,可得到34%～89%的产率.所述方法操作简单、产率高、选择性好而且对环境友好,反应结束后,催化剂很容易回收,并能有效重复使用.     

Europium oxide containing catalysts for oxidative dehydrogenation of alkanes

A method is developed to incorporate europium into Mg–Al hydrotalcites, which are precursors for oxide catalysts of oxidative dehydrogenation (ODH) of alkanes; samples of oxide catalysts are prepared, where europium oxide and gallium, magnesium, aluminum, chromium, vanadium, molybdenum, and niobium oxides are contained in various combinations. The catalytic properties of these catalysts in the reactions of ethane, propane, and butane ODH are studied. The incorporation of europium into some of our studied multicomponent catalysts enhances the reaction selectivity and increases yields of desired products.