Preparation and characterization of alumina supported silicalite membranes by sol–gel hydrothermal method

Two types of unsupported zeolites (silicalite-1 and silicalite-2) and porous alumina discs supports were prepared by the hydrothermal sol–gel synthesis method. The influence of the raw materials used as SiO₂ source, the temperature of the thermal treatment and the presence of the ceramic support on the crystallization of zeolites were studied. The reaction products were characterized by X-ray diffraction (XRD), IR spectroscopy (IR) and scanning electron microscopy (SEM) studies. The SiO₂ source had a significant effect on the final zeolite obtained: the use of colloidal silica sol (ZCS) as SiO₂ source in the synthesis led to ZSM-11 (silicalite-2) crystals, while the sodium silicate solution (ZSS) produced the ZSM-5 (silicalite-1) type. The presence of the alumina support influences the crystallization process of ZSM-5, as it improves nucleation and the ordering of the crystals.     

Synthesis,characterization and application of sulfonic acid supported on ferrite–silica superparamagnetic nanoparticles

In this study, the synthesis of sulfonic acid supported on ferrite–silica superparamagnetic nanoparticles (Fe₃O₄@SiO₂@SO₃H) as a nanocatalyst with large density of acidic groups is suggested. This nanocatalyst was prepared in three steps: preparation of colloidal iron oxide magnetic nanoparticles (Fe₃O₄ MNPs), coating of silica on Fe₃O₄ MNPs (Fe₃O₄@SiO₂) and incorporation of sulfonic acid as a functional group on the surface of Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂@SO₃H). The properties of the prepared magnetic nanoparticles were characterized using transmission electron microscopy, infrared spectroscopy, vibrating sample magnetometry, X‐ray diffraction and thermogravimetric analysis. Finally, the applicability of the synthesized magnetic nanoparticles was tested as a heterogeneous solid acid nanocatalyst for one‐pot synthesis of diindolyloxindole derivatives in aqueous medium. Oxindole derivatives were produced by the coupling of indole and isatin compounds with good to high yields (60–98%). Copyright © 2016 John Wiley & Sons, Ltd.     

微波辐射I2／Al2O3催化合成腈类化合物

微波辐射下,I2/Al2O3催化芳香醛和盐酸羟氨的无溶剂反应.一锅法合成了腈类化合物,产率80%～99%.     

Preparation and characterization of highly dispersed V2O5/SiO2prepared by a CVD method

Highly dispersed V₂O₅/SiO₂(CVD catalyst) was prepared by the reaction of vaporized VO(OPrⁱ)₃ with silica at 293 K, whose process was followed by an IR technique. The rate of propylene photooxidation increased with an increase in V₂O₅ loading for CVD catalysts, but leveled off for impregnated ones. The CVD catalysts were characterized by XAFS and photoluminescence spectroscopy.     

KF/Al2O3催化下4-芳基-9,10-二氢萘并[2,1-b]-4H-吡喃衍生物的合成

在KF/Al₂O₃催化下, α,β-不饱和腈或α,β-不饱和羧酸酯和7-甲氧基-1,2,3,4-四氢-2-萘酮反应, 生成了一系列4-芳基-9,10-二氢萘并[2,1-b]-4H-吡喃衍生物. 产物的结构通过红外光谱和核磁共振氢谱进行表征, 并通过X单晶衍射分析进一步证实产物的结构.     

Highly selective aerobic oxidation of alkylarenes catalyzed by cobalt‐based nanocatalyst in aqueous solution

The catalytic aerobic oxidation of alkylarenes catalyzed by cobalt supported on a highly crystalline γ‐Al₂O₃ support (Co/Al₂O₃ nanocatalyst) is reported. The catalyst was prepared by a co‐precipitation method and characterized using scanning and high‐resolution transmission electron microscopies, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction and surface area measurements. A wide range of alkylarenes were converted to corresponding ketones. The catalyst can be recovered by simple filtration is recyclable for up to six consecutive runs.     

Synthesis and characterization of the novel diamine‐functionalized Fe3O4@SiO2 nanocatalyst and its application for one‐pot three‐component synthesis of chromenes

Fe₃O₄@SiO₂@propyltriethoxysilane@o‐phenylendiamine as an environmentally‐benign functionalized silica‐coated magnetic organometallic nanomaterial has been synthesized and characterized by Fourier transforms infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM) images and energy dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. Then, its catalytic activity was investigated for the one‐pot three‐component condensation reaction between dimedone, malononitrile and various substituted aromatic aldehydes to afford the corresponding 2‐amino‐4H‐chromene derivatives under mild reaction conditions. This nanocatalyst can be easily recovered from the reaction mixture by using a magnet and reused for at least five times without significant decrease in catalytic activity.     

TPR/TPO characterization of cobalt–silicon mixed oxide nanocomposites prepared by sol–gel

Cobalt–silicon mixed oxides with Co/Si ratio of 10/90 (10Co), 20/80 (20Co) and 30/70 (30Co) were prepared by a modified sol–gel method. The materials treated in air at 400 and 600 °C were characterized by SEM and TPR/TPO techniques. TPR measurements showed that in all samples only a fraction of Co was present as Co₃O₄ and as amorphous silicate and was reducible by H₂ within 800 °C, while a part was not reducible under TPR conditions. The fraction of Co not reducible decreased with increasing Co content. A TPO/TPR cycle gave rise to an increase of the fraction of not reducible Co.     

Synthesis of spherical silica particles by sol‐gel method and application

Spherical silica particles were synthesized using the sol‐gel method by hydrolyzing tetraethyl orthosilicate (TEOS) with an alkali catalyst, and it was investigated how the experimental conditions (the reaction temperature, the concentration and dropping rate of the hydrolysis catalyst solution) affected the size and morphology of silica particles. Furthermore, the silica particles were doped with sodium fluoride to measure their ion release ability. The mean diameters of the silica particles changed according to the reaction temperature and the dropping rate of the hydrolysis catalyst, namely the higher the reaction temperature or the slower the dropping rate the smaller are the mean diameters. The surface area of the silica particles was significantly different depending on the dropping rate of the hydrolysis catalyst, namely the slower the dropping rate the larger the specific surface area. The specific heat capacity and thermal reduction (TG) of the silica particles were significantly different according to the reaction temperature, namely the higher the reaction temperature the lower the specific heat capacity and the TG. It was found that the fluoride‐retaining ability was proportional to the surface area of silica particles. The fluoride ion release was equilibrated on elapsing 5 min. Copyright © 2008 John Wiley & Sons, Ltd.     

Solvent‐free synthesis of propargylamines catalyzed by an efficient recyclable ZnO‐supported CuO/Al2O3 nanocatalyst

An efficient nanocatalyst of ZnO‐supported CuO/Al₂O₃ (CuO/ZnO/Al₂O₃ nanocatalyst) was prepared by the co‐precipitation method and characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray powder diffraction and Brunauer–Emmett–Teller surface area analysis. CuO/ZnO/Al₂O₃ nanocatalyst proved to be a very efficient catalyst on the synthesis of propargylamines under solvent‐free conditions in high yields. Moreover, the catalyst can be recyclable without reducing catalytic activity up to five times.     

Pt/Al2O3催化剂还原方法对Pt粒子表面性质的影响

以CO吸附红外光谱结合CO化学吸附、透射电镜和能量散射谱等手段,研究了Pt/Al₂O₃制备过程中还原方法对最终Pt粒子表面活性位分布、粒径大小和表面残余氯等表面性质的影响,重点考察了普通的气相氢气还原和甲酸钠水溶液还原两种方法的对比。结果表明,采用氢气气相还原时,Pt/Al₂O₃上Pt粒子表面台阶位和平台位比例基本不随焙烧温度而变;而采用甲酸钠水溶液还原时,Pt粒子表面台阶位所占比例随焙烧温度升高而提高。水的存在和还原条件剧烈这两个因素使得水相甲酸钠还原不利于Pt的分散,所得Pt/Al₂O₃上Pt的分散度比氢气气相还原所得要小。无论何种还原条件,水的存在都有利于Pt前躯体中的氯从Pt/Al₂O₃表面去除;而氢气气相还原所得催化剂表面则有大量残余氯存在。     

Preparation and characterization of MgO/Al2O3 mixed oxides support for hydrotreating catalysts

The characteristics of pure MgO, Al₂O₃ and three binary mixtures of MgO-Al₂O₃ were studied by determining their BET surface areas, micropore surface area, total pore volume, adsorption-desorption isotherms, the x-ray diffractogram, surface acidity and catalytic functionality for cumene cracking.The XRD results show that the incorporation of alumina into the magnesia beyond 50% renders it amorphous. Furthermore, the mixed oxide containing 50% magnesia and 50% alumina had the highest BET surface area of 200 m²/g and is the only mixed oxide with bimodal pores.The results of the acidity measurements and cumene cracking functionality indicates that strong acid sites are found only in mixed oxides containing more than 50% alumina.     

Pt/Al2O3和Pt-Cu/Al2O3催化CCl4氢化脱氯反应

制备了Al2O3负载Pt单金属催化剂和负载Pt-Cu双金属催化剂,比较了二者不同还原温度对其催化CCl4氢化脱氯反应性能的影响。 单金属Pt催化剂上主要生成CHCl3,而双金属Pt-Cu催化剂上产物随催化剂制备时的还原温度不同而异,当催化剂经400 ℃用H2还原后产物主要为CHCl3,而当催化剂经800 ℃用H2还原后产物主要为CCl2CCl2。 由于CCl4氢化反应是强放热反应,催化剂表面局部过热使得在反应中生成的C2等产物聚合结焦,覆盖了催化剂的活性中心,导致催化剂失活。 因此,通过加入甲醇作为稀释剂以带走部分反应热可提高催化剂的稳定性。 同时也降低了CHCl3的选择性,提高了CCl2CCl2的选择性。     

室温光致发光含钒硅胶的制备和研究

钒掺杂的硅胶显示出有广阔应用前景的催化和光催化特性,引起了人们在其催化机理和应用方面的研究热潮[1-6]。硅胶中氧化钒的微观分子结构和电子状态与它的催化特性密切相关,而荧光谱和磷光谱是研究分子结构,电子状态和光反应的重要工具,目前关于发光机制的研究已经取得巨大进展     

含铈钒基SCR催化剂脱硝性能及SO_2失活机理研究

掺杂Ce到V_2O_5-WO_3/TiO_2催化剂中,并研究其NH_3-SCR脱硝性能及SO_2失活机理。结果表明,V_1W_5Ce_6 Ti表现出更好的脱硝活性。采用XRD、BET、FT-IR、TG-DSC、XPS等手段表征分析Ce对催化剂性能的影响,并提出V_1W_5Ce_6Ti硫失活机理。结果表明,Ce、V、W都能在催化剂中很好的分散,当Ce的掺杂量达到8%时,有明显的CeO_2特征峰出现。在250℃时,V_1W_5Ti(U)表面会有NH4HSO4和(NH_4)_2SO_4生成。掺杂Ce后,V1W5Ce6Ti催化剂的Brnste酸位和表面化学吸附氧都增加。Ce与烟气中的SO_2和H_2O结合生成硫酸铈盐,从而抑制硫酸铵盐的生成。同时也阻断了Ce~(3+)与Ce~(4+)氧化还原循环,破坏V-O-Ce结构,造成催化剂活性下降。     

KF-Al2O3催化下2-氨基-6-甲基-4-芳基-1,3-二氰基苯衍生物的合成

以芳醛、丙二腈和丙酮为底物, 乙醇为溶剂, 在70 ℃以KF/Al2O3催化合成了一系列的2-氨基-6-甲基-4-芳基-1,3-二氰基苯衍生物, 产物的结构通过IR, 1H NMR和元素分析确证.     

Two-stage catalytic system of Sn/Al2O3 and Pt/Al2O3for NO reduction by propene in lean conditions

The Pt/Al₂O₃, Sn/Al₂O₃catalysts were prepared by the single sol-gel method. The two-stage Sn/Al₂O₃and Pt/Al₂O₃catalyst in series for NO reduction with propene were investigated. The coexistance of water vapor enhanced the activity at medium temperature of 300-400^oC, and the NO conversion was above 50% at 225 to 500^oC even in the presence of water vapor and SO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

KF/K2CO3/Al2O3催化合成香豆素

以Al2O3负载KF/K2CO3催化合成香豆素,水杨醛100 mmol,n(水杨醛)∶n(乙酸酐)∶n(KF/K2CO3/Al2O3)=1.0∶3.0∶0.3,于165℃反应2 h,香豆素产率高达89.8%。     

催化剂低温NH3选择催化还原NO的研究

研究了碳纳米管担载的五氧化二钒（V₂O₅/CNTs）催化剂上NO低温选择催化还原反应（SCR）。与活性炭载体的催化剂作了对比,结果显示,在负载低含量V₂O₅时碳纳米管较活性炭显示了更好的催化能力,而且在SO₂存在下,催化性能有更大幅度的提高。暂态反应实验显示,V₂O₅/CNTs 催化剂上NO选择催化还原反应遵循Eley Rideal机理,即反应发生于吸附态的NH₃和气相或弱吸附的NO之间。     

浆态床二甲醚合成中V2O5、Sm2O3对脱水组分γ-Al2O3的修饰作用

采用等容浸渍法制备改性脱水催化剂,通过H2-TPR、Pyridine-IR、还原态NH3-TPD、XRD等表征手段,以及目标反应浆态床CO+H2合成二甲醚,研究了催化剂的还原性能以及酸中心分布与反应性能之间的关系。H2-TPR结果表明,在脱水催化剂γ-Al2O3、V2O5/γ-Al2O3和Sm2O3/γ-Al2O3上不出现还原峰,V2O5、Sm2O3的加入改善了复合催化剂中Cu的还原性能,促进了甲醇催化剂的还原。Pyridine-IR表明,V2O5和Sm2O3的加入对L酸、B酸的量影响不大。还原态NH3-TPD说明V2O5和Sm2O3的加入改变了酸中心的分布,增加了弱酸中心的比率。XRD结果发现,V2O5和Sm2O3均匀分散在γ-Al2O3上,没有新的物种生成。二甲醚合成目标反应的结果表明,改性后催化剂的反应活性增强,合成反应中CO转化率、二甲醚的选择性都得到提高。V2O5和Sm2O3的添加增加了弱酸中心数量,促进了脱水活性,从而提高了复合催化剂合成二甲醚的活性和选择性。