有序介孔分子筛SBA-15的改性研究进展

综述了有序介孔分子筛SBA-15材料由于其骨架缺陷少,导致催化活性较低,为了扩展其在催化、大分子吸附领域的应用,需要在SBA-15表面引入活性组分的现状。从改性机理和方法出发,并结合了近年来国内外研究现状,SBA-15在金属改性和酸改性领域的应用,对今后的研究方向做出了展望。     

有序介孔分子筛SBA-15的改性研究进展

综述了有序介孔分子筛SBA-15材料由于其骨架缺陷少,导致催化活性较低,为了扩展其在催化、大分子吸附领域的应用,需要在SBA-15表面引入活性组分的现状。从改性机理和方法出发,并结合了近年来国内外研究现状,SBA-15在金属改性和酸改性领域的应用,对今后的研究方向做出了展望。     

改性SBA-15介孔分子筛的催化研究进展

SBA-15介孔分子筛,以其独特的结构、所能提供的特殊微环境以及广阔的应用前景,成为催化与纳米材料领域长久以来研究和开发的热点之一。综述了近年来SBA-15介孔分子筛的研究进展情况,侧重于改性原理、改性方法以及金属改性、酸改性和有机物改性3个具体的改性方向,并对其今后的研究方向进行了展望。     

介孔SBA-15分子筛的改性研究进展

SBA-15作为介孔分子筛材料中的代表已经成为当今化工领域的研究热点之一。它具有高度有序六方孔道结构,并且具有大的比表面积、规则有序的孔道结构、良好的热稳定性、方便对其进行功能化改性、可反复再生利用等一系列优点,被广泛应用。本文介绍了在SBA-15上掺杂金属及其化合物、嫁接有机基团、负载固体酸三种改性手段,并对其改性后的样品做了性能评价,得出理想的改性条件及反应条件,在此基础上笔者展望了SBA-15的发展前景。     

组装法制备巯基改性磁性SBA-15

采用热分解法制备了单分散、平均粒径约15nm的锰铁氧体磁性纳米粒子。通过正硅酸乙酯与磁性纳米粒子表面油酸盐的配体交换将磁性纳米粒子锚定在SBA-15表面。并且将负载过程与巯基改性过程耦合制备了巯基改性的磁性SBA-15。考察了合成SBA-15过程中干燥方式对其结构和性质的影响,研究了负载磁性纳米粒子和巯基改性顺序对巯基改性磁性SBA-15的结构和性能的影响。结果表明,喷雾干燥法合成的SBA-15介孔孔壁较薄,但具有更大的比表面积、孔体积和平均孔径。以其为载体时磁性纳米粒子负载量更大,所得磁性SBA-15的饱和磁强度更高。当将巯基改性和负载磁性纳米粒子分为前后两步时,巯基改性SBA-15的表面疏水环境有利于吸附疏水磁性纳米粒子,所得磁性SBA-15负载磁性纳米粒子量更大,饱和磁强度更高。磁性纳米粒子粒径大于SBA-15孔径,其主要负载于SBA-15外表面,有利于得到介孔孔道通畅的磁性SBA-15。巯基改性的磁性SBA-15的孔体积介于0.56~0.6cm³/g,比表面积介于353~432m²/g,饱和磁强度最高达到0.91emu/g,可作为一种大容量的吸附材料用于吸附分离、药物缓释等领域。     

杂多酸改性SBA-15对柴油氧化-吸附脱硫

用磷钨酸和磷钼酸改性SBA-15制备吸附剂,对直馏柴油、催化柴油进行氧化-吸附脱硫研究。结果表明,吸附剂对氧化后的油品吸附脱硫作用好于未被氧化的油品;经杂多酸改性后的SBA-15比单纯用SBA-15吸附脱硫效果更好;杂多酸负载量为30%时的吸附脱硫性能最好;SBA-15通过磷钼酸改性,其脱硫效果好于磷钨酸改性的SBA-15,直馏柴油的饱和吸附量可以达到17.32 mg/g;吸附剂对直馏柴油的吸附效果优于催化柴油。     

杂多酸改性SBA-15对柴油氧化-吸附脱硫

用磷钨酸和磷钼酸改性SBA-15制备吸附剂,对直馏柴油、催化柴油进行氧化-吸附脱硫研究。结果表明,吸附剂对氧化后的油品吸附脱硫作用好于未被氧化的油品;经杂多酸改性后的SBA-15比单纯用SBA-15吸附脱硫效果更好;杂多酸负载量为30%时的吸附脱硫性能最好;SBA-15通过磷钼酸改性,其脱硫效果好于磷钨酸改性的SBA-15,直馏柴油的饱和吸附量可以达到17.32 mg/g;吸附剂对直馏柴油的吸附效果优于催化柴油。     

M/SBA-15(M=Cu、Fe、Cr)介孔分子筛的制备、表征及其催化NO+CO反应研究

以介孔分子筛SBA-15为载体,采用浸渍法制备M/SBA-15(M=Cu、Fe、Cr) 介孔分子筛催化剂。采用XRD、BET、FT-IR、H₂-TPR和XPS等对样品进行分析表征,在固定床微型反应器中评价M/SBA-15(M=Cu、Fe、Cr)分子筛催化剂催化NO+CO的反应性能。结果表明,负载金属的SBA-15分子筛仍保持高度有序的二维六方介孔结构,比表面积和孔径略有减少,负载的活性金属组分在SBA-15分子筛表面具有较高的分散度。Cu/SBA-15、Cr/SBA-15和Fe/SBA-15催化剂对NO+CO反应体系均有一定活性,但由于活性金属自身的特性及其在载体表面负载量的差异,3种催化剂上呈现的NO还原活性不同,顺序为：Cr/SBA-15＞Cu/SBA-15＞Fe/SBA-15。     

Ag/SBA-15材料的制备及其CO催化氧化性能研究

采用2种不同方法将金属Ag浸渍在SBA-15上制备Ag/SBA-15复合材料,通过SEM、UV-Vis、XRD对Ag/SBA-15复合材料进行表征,并对Ag/SBA-15进行CO气体催化氧化实验,评价Ag/SBA-15复合材料的催化性能。结果表明,去除模板剂后浸渍合成的Ag/SBA-15的催化性能较好,其中金属负载量为1%的产品催化性能最好,催化所需的温度最低,CO转化率最高。     

Al-SBA-15介孔分子筛的制备及应用进展

介孔分子筛SBA-15通过化学改性,可将一些官能团引入到其骨架中改善催化性能,其中以铝改性效果最好,铝改性后的SBA-15介孔分子筛的水热稳定性及酸性明显提高。介绍了Al-SBA-15介孔分子筛的合成及应用现状,展望了介孔分子筛Al-SBA-15未来的发展方向。     

SBA-15 mesoporous silica modified with metal oxides by MDD method in the role of DeNOx catalysts

SBA-15 mesoporous silica was modified with metal (Al, Ti, Cu, Fe) oxides by the molecular designed dispersion (MDD) method using acetylacetonate complexes of metals as precursors of the catalytically active components. The modified mesoporous silicas were characterized with respect to texture (BET), composition (EPMA), coordination and aggregation of transition metal species (UV–vis-DRS), reducibility of the deposited transition metals (TPRed) and surface acidity (FT-IR). Deposition of aluminium and titanium species on the SBA-15 surface significantly increased its acidity, mainly by generation of strong Lewis acid sites. Copper and iron deposited on the surface of pure SBA-15 were present nearly exclusively in the form of mononuclear cations. Deposition of Fe or Cu on the SBA-15 supports modified with alumina or titania resulted in a formation of significant amounts of oligomeric metal oxide clusters. The SBA-15 based samples have been found to be active and selective catalysts of the DeNO_x process. The modification of the silica surface with titanium or aluminium prior to the deposition of iron or copper significantly improved the activity of the SBA-15 based catalysts.     

Catalytic combustion of benzene over metal oxides supported on SBA-15

The catalytic combustion of benzene over metal oxides supported on SBA-15 was investigated. The catalysts were prepared by the incipient wetness method and characterized by XRD, BET, TEM, ESR and TPR. The calcined siliceous SBA-15 and CuO/SBA-15 samples displayed well-resolved patterns with a sharp peak at about 1.0°. It is clear that the loading of CuO on the silica matrix drastically decreases the surface area and pore volume of the catalysts, as would be expected for the incorporation of CuO. Among the supported metal oxides, CuO supported on SBA-15 was found to have the highest activity for benzene oxidation. In addition, copper oxide supported on SBA-15 gives higher catalytic activity than copper oxide supported on MCM-41. From the ESR results, the CuO dispersed on the SBA-15 acts as the active site of the CuO/SBA-15 catalysts in the oxidative decomposition of benzene. The catalytic activity gradually increases with increasing CuO loading on SBA-15.     

A mesoporous Pt-SBA-15 nano architecture with catalytic functions on oxidation of CO

Among many kinds of noble metal catalysts, platinum is the most efficient and widely used as automotive exhaust catalysts for treatment to remove poison gases. Due to the regular pore system and controllable pore size, mesoporous silica has been acknowledged as supports of adsorption, separation, catalysts for the extremely large surface areas and shape selective properties. SBA-15 supported Pt particles are prepared by a facile method and characterized by X-ray diffraction, Transmission Electron Microscopy and N₂ isotherms techniques. Results indicate that the Pt precursor is introduced into the mesoporous successfully and all of the particles are confined in SBA-15 with monodispersed form and uniform size. The catalytic activity of Pt-SBA-15 on oxidation of carbon monoxide are also investigated and the result indicate that the catalysts possess high catalytic activity, catalytic efficiency and stability on oxidation of CO.     

SBA-15负载杂多化合物在苹果酯合成中的催化性能

用浸渍法制备了一系列中孔二氧化硅分子筛SBA-15负载的磷钨酸(PW)及其铯盐和钾盐催化剂,考察了其在乙酰乙酸乙酯与乙二醇缩合制苹果酯反应中的催化性能, 并以N2吸附,Hammett指示剂和FT-IR等手段表征了催化剂的物化性质, 在水处理试验中考察了催化剂的稳定性,溶脱到水中的杂多化合物浓度用紫外可见分光光度仪测定.结果表明,在合成苹果酯的反应中,当PW的负载量低于30%,杂多酸盐负载量低于20%时,固体催化剂无活性;催化剂在反复使用过程中活性下降的量与活性组分在极性体系中的溶脱量成对应关系,说明催化剂活性下降的主要原因是杂多酸(盐)活性组分的流失造成的,而负载磷钨酸铯盐良好的催化稳定性来源于磷钨酸铯盐的难溶脱性.     

MgO-SBA-15 Supported Pd-Pb Catalysts for Oxidative Esterification of Methacrolein with Methanol to Methyl Methacrylate☆

Novel MgO–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO–SBA-15 supports were synthesized with different...     

Catalytic performance of various mesoporous silicas modified with copper or iron oxides introduced by different ways in the selective reduction of NO by ammonia

Mesoporous silicas (MCM-48, SBA-15, MCF), reflecting various porous structures, were modified with copper and iron oxides by two different methods. For a first series of the samples the molecular designed dispersion (MDD) method using acetylacetonate complexes of copper and iron was applied for the deposition of transition metal oxides on the silica supports. A second series of the catalysts was obtained by the incipient impregnation technique using aqueous solutions of the suitable metal nitrates. The modified materials were characterized with respect to the texture (BET), composition (electron microprobe analysis), coordination of the transition metals (UV–vis–DRS) and surface acidity (NH₃-TPD, FTIR). The mesoporous silica supports modified with transition metal oxides were tested as catalysts of the selective reduction of NO with ammonia. The catalytic performance of the studied samples depended on the method used for the deposition of transition metal oxide as well as the kind of mesoporous silica used as a catalytic support. In general, the Cu-containing mesoporous samples effectively operated at lower temperatures than silicas modified with iron. The samples obtained by the MDD method have been found to be more active and selective compared to the analogous samples prepared by the impregnation technique. An introduction of water vapor into the reaction mixture only slightly decreased the NO conversion and selectivity towards N₂ over the MCF mesoporous silica modified with copper or iron oxide.     

钾对丙烷脱氢催化剂性能的影响

考察助剂钾对氧化铝和介孔分子筛SBA-15载体体系的丙烷脱氢催化剂性能的影响,XRD、NH₃-TPD和铂分散度表征结果表明,钾对两种体系催化剂的影响完全不同,在氧化铝体系中,钾助剂降低催化剂酸性,提高催化剂性能,而在SBA-15载体体系中,钾的引入使催化剂中铂的分散度大大降低,从而使催化剂活性降低,不利于反应。     

Assessment of Fe2O3/SiO2 catalysts for the continuous treatment of phenol aqueous solutions in a fixed bed reactor

Different iron-containing catalysts have been tested for the oxidation of phenol aqueous solutions in a catalytic fixed bed reactor in the presence of hydrogen peroxide. All the catalysts consist of iron oxide, mainly crystalline hematite particles, over different silica supports (mesostructured SBA-15 silica and non-ordered mesoporous silica). The immobilization of iron species over different silica supports was addressed by direct incorporation of metal during the synthesis or post-synthesis impregnation. The synthesis conditions were tuned up to yield agglomerated catalysts with iron loadings between 10 and 15 wt.%. The influence of the preparation method and the type of silica support was evaluated in a catalytic fixed bed reactor for the continuous oxidation of phenol in terms of catalysts activity (phenol and total organic carbon degradation) as well as their stability (catalyst deactivation by iron leaching). Those catalysts prepared by direct synthesis, either in presence of a structure-directing agent (Fe₂O₃/SBA-15(DS)) or in absence (Fe₂O₃/SiO₂(DS)), achieved high catalytic performances (TOC reduction of 65% and 52%, respectively) with remarkable low iron leaching in comparison with their silica-based iron counterparts prepared by impregnation. Catalytic results have demonstrated that the synthesis method plays a crucial role in the dispersion and stability of active species and hence resulting in superior catalytic performances.     

Covalent anchoring of Mo(VI) Schiff base complex into SBA-15 as a novel heterogeneous catalyst for enhanced alkene epoxidation

Molybdenum(VI) Schiff base complexes modified mesoporous SBA-15 hybrid heterogeneous catalysts were synthesized by the reaction of MoO₂(acac)₂ with mesoporous SBA-15 functionalized by grafting procedures of 3-aminopropyl-triethoxysilane and salicylaldehyde, respectively. The physico-chemical properties of the as-synthesized catalysts were analyzed by ICP-AES, XRD, N₂ adsorption–desorption, FT-IR, SEM, TEM and EDX. The as-synthesized catalysts were effective in the catalytic epoxidation of cyclohexene. The catalytic activity can be further enhanced by silylation of the residual Si–OH groups using Me₃SiCl, which was largely due to the higher content of Mo active sites. The conversion and selectivity reached to 97.78 and 93.99 % using tert-butyl hydroperoxide as oxidant for Mo–CH₃–SA–NH₂–SBA-15, while 81.97 and 89.41 % in conversion and selectivity for Mo–SA–NH₂–SBA-15. At the same time, the catalytic performances of the hybrid materials were further systematically investigated under various reaction conditions (solvent, oxidants and alkenes, etc.). Mo–CH₃–SA–NH₂–SBA-15 catalyst can be recycled effectively and reused four cycles with little loss in activity. In addition, the results from hot filtration demonstrated that the catalytic activity mostly resulted from the heterogeneous catalytic process.