Highly Efficient Near-IR Photoluminescence of Er Immobilized in Mesoporous SBA-15

SiO₂ mesoporous molecular sieve SBA-15 with the incorporation of erbium ions is studied as a novel type of nanoscopic composite photoluminescent material in this paper. To enhance the photoluminescence efficiency, two schemes have been used for the incorporation of Er³⁺ where (1) Er³⁺ is ligated with bis-(perfluoromethylsulfonyl)-aminate (PMS) forming Er(PMS)_x-SBA-15 and (2) Yb³⁺ is codoped with Er³⁺ forming Yb-Er-SBA-15. As high as 11.17 × 10⁻²¹cm² of fluorescent cross section at 1534 nm and 88 nm of “effective bandwidth” have been gained. It is a 29.3% boost in fluorescent cross section compared to what has been obtained in conventional silica. The upconversion coefficient in Yb-Er-SBA-15 is relatively small compared to that in other ordinary glass hosts. The increased fluorescent cross section and lowered upconversion coefficient could benefit for the high-gain optical amplifier. Finally, the Judd–Ofelt theory has also been used for the analyses of the optical spectra of Er(PMS)_x-SBA-15.     

A comparative investigation on the properties of Cr-SBA-15 and CrOx/SBA-15

High-surface area and well-ordered mesoporous Cr-incorporated SBA-15 (Cr-SBA-15) and SBA-15-supported chromia (CrO_x/SBA-15) with Cr surface density = 0.05–1.11 Cr-atom/nm² have been prepared, respectively, using the one-step synthesis and incipient wetness impregnation method, and characterized by AAS, XRD, BET, ESEM, TEM, XPS, laser Raman, UV-Vis, FT-IR, and H₂-TPR. It is observed that the Cr-SBA-15 and CrO_x/SBA-15 samples showed an evolution of surface morphology from long chain-shaped to short rod-like and further to an irregularly spherical architecture at elevated Cr content, which might arise from the interaction of Cr ions or CrO_x domains with SBA-15. There were co-presence of tetrahedrally coordinated mono- and poly-chromate (Cr⁶⁺) as well as octahedrally coordinated Cr³⁺ species in Cr-SBA-15 and CrO_x/SBA-15, with the Cr⁶⁺ species being dominant at Cr surface density ≤0.22 Cr-atom/nm² in Cr-SBA-15 and Cr ≤0.54 Cr-atom/nm² in CrO_x/SBA-15, whereas the amount of the Cr³⁺ species increased markedly at Cr surface density ≥0.53 Cr-atom/nm² due to the formation of crystal Cr₂O₃ phase. Maximal Cr incorporation into Cr-SBA-15 and one monolayer surface CrO_x coverage on CrO_x/SBA-15 occurred at Cr surface density ≤0.53 Cr-atom/nm² and <1.11 Cr-atom/nm², respectively. The CrO_x/SBA-15 samples exhibited better reducibility than the Cr-SBA-15 samples, with the best reducibility exhibited at Cr surface densities of 0.54 and 0.12 Cr-atom/nm², respectively.     

V/ SBA-15分子筛的制备及其对乙苯制苯乙酮反应的催化性能

以聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(简称P123)为模板剂,正硅酸乙酯为硅源,前驱体为柠檬酸氧钒配合物,采用水热法在酸性条件下制备了V-SBA-15有序介孔材料。考察了不同晶化时间、模板剂用量等因素对介孔分子筛V-SBA-15制备的影响。结果表明,最优晶化时间为96 h、模板剂用量n=1.0〔以n(P123)/n(V+Si)计〕,在该条件下所制备的材料具有类似于分子筛SBA-15高度有序的六方介孔结构,且活性组分钒在介孔氧化硅基体中均匀分散。用XRD、FTIR、BET、SEM及TEM等方法对制备的分子筛V-SBA-15进行结构表征,同时在乙苯制苯乙酮反应中以苯乙酮选择性及收率来验证催化剂的催化性能。结果表明,在催化氧化乙苯制苯乙酮反应较优工艺条件下,苯乙酮选择性及收率分别为82.0%和38.60%。     

Highly Effective Oxidative Dehydrogenation of Propane Over Vanadia Supported on Mesoporous SBA-15 Silica

Vanadia-containing mesoporous SBA-15 catalysts were prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadia-supported SBA-15 catalysts exhibit a much higher catalytic activity than those reported in the literature obtained over vanadium-supported mesoporous MCM-41 catalysts in the ODH of propane. The high catalytic performance of the mesoporous SBA-15 catalysts is attributed to the particularly large pore diameters and low surface acidity.     

Organo-Modification of Mesoporous SBA-15 with Chiral Diacid and its Utilization for the Preparation of L-Phenylalanine-Based Poly(amide-imide) Nanocomposites

In this study ultrasonic irradiation has been proposed for organo-modification of SBA-15 with N,N′-(pyromellitoyl)-bis-L-phenylalanine. Chiral poly(amide-imide) (PAI) was synthesized by the direct polymerization of L-chiral diacid and 4,4-diaminodiphenyle sulfone in molten tetrabutylammonium bromide. Different nanocomposites (NCs) of modified SBA-15 and chiral PAI were synthesized by solution intercalation method under ultrasonic irradiation. The structures and morphology of the hybrids were investigated by different techniques. The NCs showed an improvement in the thermal properties in comparison with the neat PAI. Transmission electron microscopy images show well-ordered hexagonal arrays of mesopores SBA and the average distances between neighboring pores is around 3–5 nm.     

Catalytic aerobic oxidation of ethylbenzene over Co/SBA-15

Co(II)O was highly dispersed in the mesopores of SBA-15 by alcoholic impregnation method and characterized by XRD, TEM, UV–VIS DRS, TPR, and XRF techniques. It was found that tetrahedral coordinated Co(II)O was stabilized by SBA-15 at low Co-loading. Co/SBA-15 showed much higher activity than Co(OAc)₂ or Co₃O₄ in the liquid-phase aerobic oxidation of ethylbenzene under solvent-free condition.     

Tuning of nanostructured SBA-15 silica using phosphoric acid

A simple method is described to synthesize mesoporous SBA-15 with controlled distinct morphologies. Using the same initial synthesis mixture composition consisting of non-ionic P123 block co-polymer, tetra-ethyl orthosilicate as silica source and phosphoric acid, well-ordered mesoporous films, cakes, fibers and bundle-like structures were produced simply by changing the stirring rate. Free-standing films at the air–water interface and cake-like structures were obtained simultaneously under static conditions. On the other hand, fibers and bundles of threads resulted under vigorous and slow stirring conditions, respectively. Transmission electron microscopy (TEM) images of these bundles revealed straight parallel nanochannels oriented along the long axis of the bundles. X-ray fluorescence (XRF) measurements of the calcined samples indicated the presence of phosphorus, which might provide additional Brønsted acid sites for potential applications in catalysis.     

Synthesis and characterization of Co-containing SBA-15 catalysts

Two Co-SBA-15 catalysts were synthesized and characterized by thermogravimetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, porosity, UV–visible diffuse reflectance and temperature programmed reduction with H₂. The first catalyst was prepared synthesizing SBA-15 and then adding Co ions by impregnation (Co_imprSBA-15). The second catalyst was prepared using a more complex procedure of immobilization of cobalt ions in the presence of pyridine and H₂O₂ on –COOH groups anchored to the SBA-15 structure [Co-SBA-15(COOH)]. These COOH groups were created starting from cyano groups introduced during the synthesis of the periodic mesoporous materials as 4-triethoxysilylbutyronitrile. Characterization of the samples indicates that in both cases the typical 2D periodical hexagonal structure of SBA-15 was obtained, but with less ordered packing in the second case. The cobalt is highly dispersed in the SBA-15 (up to 9% w/w) and is present mainly as Co²⁺ ions in highly distorted tetrahedral or square pyramidal coordination. Some coordinatively unsaturated Co(II) Lewis acid centers are present in Co_imprSBA-15, while in Co-SBA-15(COOH) coordination of pyridine to cobalt tentatively may induce the formation of Co³⁺ ions, although in both catalysts the dominant species are Co²⁺ ions in a very close environment.     

Effect of the preparation method on the structural stability and hydrodesulfurization activity of NiMo/SBA-15 catalysts

Defined hexagonal cylindrical pore structure SBA-15 material was synthesized as support for hydrotreating catalysts. The stability of the mesoporous material under acid and basic environments commonly used to prepare hydrotreating catalysts was investigated. The effects of the acid and basic treatments on the stability of SBA-15 and NiMo/SBA-15 catalysts were evidenced by different characterization techniques such as N₂ adsorption–desorption, X-ray diffraction (XRD), Raman Spectroscopy and high resolution transmission electron microscopy (HRTEM). Supported NiMo/SBA-15 catalysts prepared by pore volume co-impregnation in acidic, neutral and basic solutions of the Ni and Mo precursor salts were characterized to evaluate the textural and structural changes caused by the method of preparation. Characterization of the support after accelerated stability tests indicates large deterioration of the SBA-15 structural order at basic pH. The characterization results of oxide and sulfided catalysts indicate, for the catalysts prepared at high pH, an increasing presence of β–NiMoO₄ phase in the oxide catalysts, and a relatively lower population of MoS₂ in the sulfided catalysts. The activity of the different catalysts evaluated in the thiophene hydrodesulfurization reaction was higher for the catalysts prepared at low pH.     

Preparation, Characterization and Catalytic Activity of Palladium Nanoparticles Encapsulated in SBA-15

A simple adsorption method was studied for the preparation of SBA-15-encapsulated palladium nanoparticles. This method employed the SBA-15 with organic template removed by ethanol extraction for the adsorption of cationic Pd precursors in alkaline solution followed by calcination and H₂ reduction. The pH of the solution was found to be a critical factor in determining the palladium content and the ordered mesoporous structure. Our characterizations revealed that the Pd nanoparticles prepared by this method were located inside the mesoporous channels and were quite uniform in size (mostly 3–4 nm). The SBA-15-encapsulated uniform Pd nanoparticles were efficient catalysts for solvent-free aerobic oxidation of alcohols.     

介孔材料SBA-15固定化脂肪酶的研究进展

介孔材料由于其孔道分布有序且孔径均匀等优点而在固定化酶催化领域引起人们的广泛关注.本文综述了新型介孔材料SBA-15对脂肪酶固定化的研究进展.总结了SBA-15的孔径大小、形貌及等电点等因素对脂肪酶固定化的影响.归纳了SBA-15上三种不同固定化方法的优缺点,并介绍了SBA-15固定化脂肪酶在手性拆分、酯水解、酯合成及转醇化反应等领域的应用.最后提出SBA-15固定化脂肪酶在发展过程中存在的问题以及今后的发展趋势.     

Incorporation of a tungsten Fischer-type metal carbene covalently bound to functionalized SBA-15

A metal Fischer carbene [(CO)₅WC(φ)OCH₂CH₃] was covalently linked for the first time to the silanol groups of the mesoporous channels of SBA15 by following two different synthetic anchoring routes. The first one goes through the reaction of the SBA15 mesoporous silica walls functionalized by aminopropyltriethoxysilane (APTES) with a tungsten carbene Wφ, while in the second approach a precursor synthesized by reacting APTES with the carbene Wφ is then anchored via a direct bond to the silanol groups in the interior pore channels of SBA-15.

This tethering is helpful to prevent the decomposition of the metallic complex. XRD, N₂ adsorption–desorption, and TEM analysis provide strong evidence that the mesoporous support structure retains its long-range ordering after the grafting process, despite a significant reduction of its specific surface area, pore-volume and pore-size. The chemical bonding of the tungsten carbene to the silanol groups of SBA-15 materials was studied with solid-state NMR spectroscopy. Both ¹³C MAS NMR and ²⁹Si CP MAS NMR spectra confirm the covalent linking of the carbene to the silica-pore system.     

Mesoporous silica supported cobalt oxide catalysts for catalytic removal of benzene

Two types of mesoporous silica SBA-15 with different pore diameter were synthesized with an ageing temperature of 373 K and an ageing temperature of 308 K, respectively; in addition, mesoporous silica with amorphous structure was synthesized by adding organosiloxane as part of the silica source during the synthesis procedure. Mesoporous silica and conventional alumina supported cobalt oxide catalysts were prepared by incipient wetness impregnation method. These materials were characterized by FT-IR, nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Temperature programmed reduction (TPR) techniques, and the activity of the supported cobalt oxide catalysts for deep oxidation of benzene were evaluated in a fixed-bed reactor. It seems that the pore diameter of the silica increase with the elevation of the ageing temperature. Mesoporous silica supported cobalt oxide catalysts are more active than conventional alumina supported ones. Cobalt oxide can be relatively better dispersed on the surface of mesoporous silica which has larger pore diameter and surface areas. Meanwhile, more silanol groups exist on the surface of amorphous silica, which could induce a strong interaction with the supported cobalt oxide species, leading to poor activity for benzene oxidation.     

SBA-15分子筛形成过程的介观动力学模拟及实验研究

为了研究三嵌段共聚物的自组装过程和SBA-15的形成机理,采用介观动力学(MesoDyn)方法模拟介孔分子筛SBA-15形成过程中模板剂P123与硅源试剂TEOS的协同自组装过程,并通过向体系引入稳恒剪切力来代替实际外力模拟了SBA-15六角介观相的形成过程,直观地展现了P123/硅酸物种超分子聚集体在SBA-15结构形成过程中的作用。模拟结果表明,P123与TEOS在水溶液中通过协同作用能够自组装形成尺寸均一的球状超分子聚集体,这是硅基有序介孔分子筛SBA-15形成过程中的前驱体:疏水的PPO嵌段团缩在该超分子聚集体的内部,在SBA-15分子筛形成中起决定性的致孔作用;亲水的PEO嵌段与包裹在胶束外部的TEOS相互交织在一起,其使得SBA-15在制备后期脱除模板剂后形成一些与主介孔相互连接的无规则微孔。在引入剪切力作用后,该P123/TEOS超分子聚集体不再自组装形成球状胶束,而是被拉扯成圆柱状的胶束,并且最终排列成为具有规则的六角形状的聚集结构,这一六角介观相则是介孔分子筛SBA-15的结构基础。今采用模拟条件,用水热法合成了高质量的SBA-15分子筛,通过XRD和高分辨透射电镜分析表明,模拟SBA-15形成过程的结果与实验合成的SBA-15具有相互吻合的完美二维六方结构。     

Flash induction calcination: A powerful tool for total template removal and fine tuning of the hydrophobic/hydrophilic balance in SBA-15 type silica mesoporous materials

A new rapid calcination method has been used to completely remove the organic template from SBA-15 ordered mesoporous silica, and to preserve a high number of silanol in these materials. This calcination method provided by an induction furnace was found to considerably reduce the calcination time and therefore the energy consumption associated. Moreover, adjustment of both calcination temperature and duration allowed tuning the hydrophobic/hydrophilic balance of the mesoporous SBA-15 silica materials. For comparison, short and long time conventional muffle furnace calcination was performed. The induction calcination was also successfully applied to different type of mesoporous silica materials such as SBA-16 and MCM-41.     

Use of mesoporous SBA-15 for nanostructuring titania for photocatalytic applications

SBA15–TiO₂ samples prepared by introducing titanium with a grafting method and having TiO₂ loadings below 15 wt.% have been characterized by XRF, XRD, IR, porosimetry, SEM, HRTEM, and UV–Visible diffuse reflectance. Differently from the samples reported in the literature characterized by a high TiO₂ loading, no evidences have been found for the presence of titania particles inside or outside the mesopores of SBA-15. Three different titanium species were instead evidenced to be present. The first two derive from the reaction of titanium with silanol groups in the corona area of inner SBA-15 walls leading to the formation of either TiO₄ tetrahedral sites (by reaction by hydroxyl nests of surface defect sites) and/or pseudo-octahedral surface sites anchored by two (or more) Si or Ti ions through bridging oxygens. The third species derives from the reaction of titanium in the regions with high sylanol density, e.g. in the micropores located in the corona of SBA-15 channels, leading to the formation of TiO₂-like nanoareas (probably Si-doped) with dimensions of around 1–2 nm maximum. The potential interest of these materials as photocatalysts, for the presence of a TiO₂-like nanoareas highly accessible by reactants, is discussed.     

超声对Cu(I)/SBA-15脱硫吸附剂制备和性能的影响

分别采用超声浸渍法和普通浸渍法制备了Cu(I)/SBA-15吸附剂,利用静态吸附实验比较了这两种方法制备的吸附剂在模型汽油中的噻吩吸附脱硫性能,并利用BET,TEM,XPS等手段对所制备的吸附剂进行了表征.结果表明,超声浸渍法制备的Cu(I)/SBA-15吸附剂的脱硫性能明显优于普通浸渍法制备的吸附剂.BET结果显示,超声促进了活性组分铜在吸附剂表面的分散.TEM分析表明,在超声场下制备的Cu(I)/SBA-15吸附剂表面的铜粒子颗粒较小,且分布均匀.XPS分析显示,超声有效地提高了铜离子在吸附剂表面的负载量,并且促进Cu(I)在其表面含量的增加,从而有利于吸附脱硫性能的提高.     

介孔Fe2O3/SBA-15催化臭氧氧化含酚废水

含酚废水来源广泛自然条件下难以去除,酚类物质毒性大对生态环境和人类生活健康造成了较严重的影响。本文选取了有机废水处理中较为高效的臭氧催化氧化技术,使用臭氧氧源曝气产生大量的含氧自由基,催化氧化降解酚类有机物,同时对活性中心载体进行了优化,选取制备了一类水热稳定性好及机械强度高的多孔材料,使用这些多孔材料对活性中心Fe₂O₃进行了再组装,合成了一系列表面富集Fe₂O₃的SBA-15介孔薄膜材料,由于SBA-15材料较大的比表面积、丰富的孔隙结构、高度分散的活性中心,在臭氧催化氧化含酚废水中取得了较好效果。苯酚溶液初始浓度为100mg/L (COD 238mg/L)、Fe₂O₃(5)/SBA-15催化剂投加量为30g、臭氧气体流量为2mg/min、废水HRT为5min、流量为0.8L/h的条件下,该催化剂能高效连续稳定运行500h不易失活,其COD去除率仍能保持在65%以上,催化剂活性依然保持在83%以上。Fe₂O₃/SBA-15类介孔催化材料在深度处理含酚废水中具有工业化应用潜质。     

介孔SBA-15负载磷钨酸催化四氢呋喃聚合的研究

以SBA-15为载体负载磷钨酸(HPW),用于催化四氢呋喃(THF)开环聚合,采用在线反应红外分析仪(ReactIR)测定THF转化率,实验考察了HPW负载质量百分比、3-氨丙基三乙氧基硅烷(APTES)/SBA-15质量比和载体SBA-15孔径等因素对催化剂的催化性能和THF转化率的影响。结果表明:采用直接浸渍法负载HPW,HPW最优负载质量百分比为40%;将SBA-15进行氨基改性后负载HPW,最优APTES/SBA-15质量比为mAPTES/mSBA-15=0.0712,且通过氨基改性可有效改善催化剂的重复利用性能;当载体SBA-15的比表面积较大时(853 m2·g-1)或孔径较大(比表面积较小498~585 m2·g-1)时,所制备的催化剂具有较高的催化效率、聚合产物平均分子量较大,催化剂的催化效率和聚合产物分子量随着孔径增大而增大。