Preparation of SBA-15 extrudates: Evaluation of textural and mechanical properties

SBA-15 powder (P) was shaped into cylindrical extrudates (Ex) by compounding with additives such as bentonite (binder), methylcellulose and tetraethylorthosilicate (TEOS). The extrudates of SBA-15 were characterized by XRD, N₂ adsorption and thermogravimetric analysis. The orderly growth of SBA-15 is evident from the XRD patterns. The surface area and pore volume of SBA-15 (P) were around 884 m²/g and 1.1 cm³/g, respectively. The decrease in surface area and pore volume were observed for SBA-15 (Ex) in comparison to SBA-15 (P). This may be due to partial blocking of pore entry and surface coverage of additives during shaping of extrudates. The mechanical strength of SBA-15 (Ex) was examined by vertical crushing method. The effect of additives on the mechanical strength of SBA-15 (Ex) was examined by varying the composition. The results indicate linear increase of mechanical strength with increase in the content of bentonite and methylcellulose, but non-linear response with increase of TEOS and water. Compounding additives have been established to improve the mechanical strength of the extrudates.     

In-vitro drug release kinetics studies of mesoporous SBA-15-azathioprine composite

The mesoporous silica (or SBA-15) was loaded with azathioprine drug. Azathioprine drug was incorporated into mesoporous silica by post impregnation method to reduce its toxic effects by controlling the drug release property. The synthesized pure SBA-15 and SBA-15-azathioprine composite were characterized by UV–visible spectrophotometry, thermo-gravimetric analysis, small and large angle powder X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption–desorption analysis. The successful inclusion of azathioprine drug in host material SBA-15 was confirmed by the reduced surface area (114 m²/g) and pore diameter (6.5 nm) of the organic–inorganic composite material. The drug entrapment efficiency of 90.67 % and loading efficiency of 72.67 % was achieved. The azathioprine drug release process from the mesoporous silica to simulated gastric, intestinal and body fluid were examined and the controlled release effect of the azathioprine drug in all fluids were studied. The Korsmeyer–Peppas model fits well the drug release data with the non-Fickian diffusion model and zero order kinetics for produced mesoporous silica. The controlled drug release enhanced the bioavailability and reduces its repeated administration. Hence, the composite drug can reduce the toxicity and side effects of the azathioprine.     

高分散的Ir/SBA-15的制备及其催化性能

采用一锅法将P123、TEOS、HCl和H2IrCl6溶液混合,酸性条件下得到高度分散的Ir/SBA-15催化剂.使用X射线衍射、透射电镜和N2吸附-脱附等对样品进行表征.结果表明,一步合成的Ir/SBA-15依然保持高度有序的介孔孔道结构、较大比表面积和孔容,而且Ir在SBA-15孔道内高度分散.CO的催化氧化反应结...     

Pd/SBA-15 nanocomposite: Synthesis, structure and catalytic properties in Heck reactions

Pd nanoparticles supported in mesoporous silica SBA-15 (or Pd/SBA-15 nanocomposites) were prepared by ion-exchange with cationic Pd precursor in an alkaline solution on an uncalcined silica. The high Pd loading in these nanocomposites can be achieved up to 5.21 wt.% by adjusting the pH value of the solution. The surface area and the pore volume decrease with increasing Pd loading. The Pd nanoparticles equal to or smaller than 6 nm in size in the nanocomposites are distributed in the channels of the mesoporous SBA-15. The Pd/SBA-15 nanocomposites exhibit excellent catalytic activities and high reuse ability in air for the Heck carbon-carbon coupling reactions.     

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。     

SBA-15改性石墨烯环氧复合涂层制备及其防腐性能

用γ-氨丙基三乙氧基硅烷（KH-550）将SBA-15分子筛接枝到石墨烯上制备功能填料，并将其填充到水性环氧树脂中制备复合涂层。采用红外光谱（FTIR）、氮气吸附脱附和透射电镜（TEM）对填料进行表征；采用电化学阻抗谱（EIS）、盐雾试验和附着力测试等方法对不同填料添加量涂层的防腐性能及力学性能进行表征。实验结果表明，当功能填料添加质量为1.0%时，涂层具有最佳的电化学性能、耐盐雾性能、以及附着力性能。复合涂层的防腐性能明显优于纯环氧涂层，因为功能填料的孔/片协同结构有效的延缓了腐蚀粒子到达金属基材表面的时间。     

Facile synthesis route to monodispersed platelet-like SBA-15 silica

We here report a facile synthesis route to monodispersed platelet-like SBA-15 mesoporous silica employing kinetically controlled micelles as templates. In previous preparations of SBA-15 silica, it was believed that thermodynamically equilibrated micelles were used as templates. The kinetically controlled micelle has never been used before to generate periodic mesoporous materials with unique morphology. Monodispersed hexagonal platelet-like SBA-15 microparticles were prepared via a very facile synthesis route by tuning the micelle formation process, i.e. the stirring rate and the time of dissolution of the triblock copolymer and formation of the micelles. Shorter micelle formation time and faster stirring are essential to generate platelet-like SBA-15 silica particles. It is expected to apply in the synthesis of a wide variety of mesophase materials.     

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.     

Copper and chromium modified SBA-15: C-radiolabeling catalytic study

Novel ¹¹C-radiolabeling catalytic approach is applied for the characterization of copper and chromium modified SBA-15 materials. The method is based on the selective adsorption of ¹¹C-methanol on different catalytic sites with the detection of the products of the conversion. The high CO₂ and methylformate selectivity is related to the activity of CuO and Cr₂O₃ species, while copper chromate nanoparticles facilitate the formation of dimethoxymethane.     

Nanocrystalline CeO2 in SBA-15: Performance of Pt/CeO2/SBA-15 Catalyst for Water-gas-shift Reaction

CeO₂ particles confined within the pores of an SBA-15 mesoporous silica host were prepared by incipient wetness impregnation (IMP) and deposition precipitation (DP) methods. The materials were characterized by XRD, N₂-adsorption and temperature programmed reduction (TPR) to evaluate the structure, texture, and redox properties. The preparation procedure had significant impact on the assembling mode of CeO₂ inside the SBA-15 mesopores. A high dispersion of CeO₂ particles was achieved via DP, whereas the dispersion of CeO₂ prepared by IMP was found to be inhomogeneous and CeO₂ partially blocked the pores. The CO conversion in the water-gas-shift reaction was enhanced over 1 wt% Pt supported on CeO₂-modified SBA-15 obtained by DP.     

Investigation of the photodegradation properties of iron oxide doped mesoporous SBA-15 silica

Mesoporous silica (SBA-15) and iron oxide incorporated silica (Fe₂O₃-SBA-15) were synthesized by co-operative self-assembly technique. Samples were characterized using nitrogen adsorption–desorption isotherm, electron microscopic and spectroscopic techniques. The results confirm the uniform distribution of pores, presence of metal oxides in the pores as well as in the surface of the mesoporous wall and oxidation state of iron in the Fe₂O₃-SBA-15. The photocatalytic degradation of methylene blue (MB), sulphorhodamine B (SR-B) and methyl orange (MO) by Fe₂O₃-SBA-15 was investigated. It was observed that Fe₂O₃-SBA-15 degraded 98 % of MB, 96 % of SR-B and 99 % of MO within 3 h after exposure to sunlight. SBA-15 does not exhibit any photocatalytic effect. These results demonstrate the potential of Fe₂O₃-SBA-15 for environmental pollution control.     

One-pot synthesis of Ga-SBA-15: Activity comparison with Ga-post-treated SBA-15 catalysts

Gallium containing SBA-15 mesoporous materials with different Si/Ga ratio were synthesized using an in situ sol–gel procedure with an aqueous solution of Ga(NO₃)₃. The materials were characterised by means of elemental analysis, BET, XRD, TEM, and H/D isotope exchange techniques. It appears that depending their loading, stable Ga-species were either anchored to the siliceous matrix of SBA-15 or introduced in the framework via isomorphous substitution, thus generating acid properties in their host material.The catalytic activity of Ga-SBA-15 materials has been evaluated in the Friedel–Crafts acylation of anisole with benzoyl chloride and in the alkylation of benzene using benzyl chloride as alkylating agent. The activity of these catalysts was compared with the one of Ga-modified SBA-15 by post-treatment. A complete conversion of benzyl chloride over Ga-SBA-15 materials has been reached after 3 h of reaction with a 75% selectivity toward diphenylmethane. In contrast to Ga-samples prepared by post-treatment, in situ Ga-SBA-15 present a lower stability in the acylation reaction. However, the catalytic results indicate that Ga-SBA-15 mesoporous materials can be used as versatile and stable acid catalysts for Friedel–Crafts reactions with appropriate behavior depending on their preparation mode.     

Mesoporous TiO2/SBA-15, and Cu/TiO2/SBA-15 Composite Photocatalysts for Photoreduction of CO2 to Methanol

A series of mesoporous TiO₂/SBA-15, Cu/TiO₂ and Cu/TiO₂/SBA-15 composite photocatalysts were prepared by sol–gel synthesis for photoreduction of CO₂ with H₂O to methanol. It was found that optimum amount of titanium loading of TiO₂/SBA-15 was 45 wt% which exhibited higher photoreduction activity than pure TiO₂. An addition of copper on TiO₂ or TiO₂/SBA-15 catalyst as cocatalyst was found to enhance the catalytic activity because copper serves as an electron trapper and prohibits the recombination of hole and electron.     

Pre-prepared platinum nanoparticles supported on SBA-15 – preparation, pretreatment conditions and catalytic properties

The primary objective of this paper is the complete characterization of Pt/SBA-15 catalysts prepared by sonication aided impregnation. During the experiments (i) the influence of sonication applied for introducing the already prepared platinum nanoparticles into the pores of the silica support, (ii) the pressure used for preparing the tablets and/or wafers for catalytic test, (iii) the temperature of heat treatment on the structural changes of catalyst samples, (iv) the effect of platinum particle concentration, and (v) the removal of rest organic matter from the catalysts by different procedures were systematically studied. The samples were characterized by nitrogen adsorption/desorption measurements (BET), TEM, SAXS, XRD and IR. The catalytic activity of the samples was also investigated in the reaction of cyclohexene hydrogenation.     

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.     

Sn修饰SBA-15、MCM-41催化剂的制备及顺酐酯化性能

以SBA-15和MCM-41分子筛为载体,负载无水四氯化锡,制备了SnCl4-SBA-15和SnCl4-MCM-41催化剂,考察了不同锡与硅物质的量比对催化顺酐与正丁醇酯化反应的影响。结果表明,SnCl4-SBA-15表现出比SnCl4-MCM-41更高的催化性能,顺酐转化率为99.8%,副产物较少,马来酸二丁酯的产率最高可达91.3%。采用X射线衍射、N₂物理吸附、傅立叶红外光谱和紫外-可见漫反射技术对催化剂进行表征,结果显示, SnCl₄-SBA-15具有较高的比表面积,较大的孔容和孔径,更有利于催化反应的进行。     

Base-Free Benzyl Alcohol Aerobic Oxidation Catalyzed by AuPdNPs Supported on SBA-15 and TiO2/SBA-15 Mesoporous Materials

Catalysis Letters - It is known that the oxidative reactions of alcohols are sensitive to the characteristics of the catalyst, in such a way that the properties of the support are as important as...     

V、Mo修饰SBA-15分子筛结构与催化性质的DFT计算预测

采用密度泛函方法,计算了介空分子筛SBA-15及V和Mo原子修饰后分子筛的几何参数及红外光谱,与实测值比较,确定了分子筛的合理模型。通过分析模型化合物的前线分子轨道,推测了V和Mo原子修饰前后分子筛表面的酸碱中心及氧化还原性质。最后,由计算得到分子筛表面VO4和MoO5基团的Mayer键级推测,当此类催化剂参与酸碱和氧化还原反应时,基团上的三种化学键(MO─Si、M─OSi和MO)中,MO─Si键最容易断裂打开,参加化学反应。     

Preparation, characterization, and catalytic properties of the Mo2C/SBA-15 catalysts

A series of Mo₂C/SBA-15 catalysts with different Mo contents were prepared by temperature-programmed carburization (TPC). The materials obtained and their oxide precursors (MoO₃/SBA-15) were characterized by Nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) spectroscopy. The activities of the catalysts for deep hydrodesulfurization (HDS) of thiophene were evaluated. The results of N₂ adsorption-desorption isotherms indicated that the surface area and pore diameter of the oxide precursors increase after carburization. The XRD patterns show that Mo₂C particles are highly dispersed in the SBA-15 ordered mesoporous. The test results show that Mo₂C/SBA-15 catalysts have an excellent performance for the deep HDS under the lower temperature region.     

Synthesis of functionalized SBA-15 with ordered large pore size and its adsorption properties of BSA

SBA-15, mesoporous material, is a very excellent candidate for drug delivery system because its pore size is easy to control according to synthesis conditions and the presence of swelling agent. In this study, a known swelling agent, 1,3,5-trimethylbenzene (TMB), was used to increase the pore size with increased aging temperature and prolonged aging time. Furthermore, 3-aminopropyltriethoxysilane (APTES) was incorporated on SBA-15 surface via post synthesis method to separate protein effectively. The samples were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption analyses, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier Transform Infrared (FT-IR). Adsorption capacity increased with temperature at the isoelectric point (pI) of bovine serum albumin (BSA) regardless of the pore size of SBA-15 samples. Release studies were carried out in the range of pH from neutral to basic solution on unmodified and amine-modified samples. In addition, the adsorption mechanism was investigated by employing the pseudo-first order, pseudo-second order, and intraparticle diffusion models.