CRN synthesis of β-SiAlON from a nanocomposite precursor of mesoporous silica–alumina (Al-SBA-15) with poly 4-vinyl pyridine

This paper reports the use of a nanocomposite precursor of mesoporous silica?Calumina (Al-SBA-15) with poly 4-vinyl pyridine (P4VP) to synthesise ??-SiAlON by carbothermal reduction and nitridation under N₂ at 1,450?°C. Small-angle XRD, SEM/TEM, ²⁹Si and ²⁷Al MAS-NMR and BET specific surface area measurements of the Al-SBA-15 and P4VP/Al-SBA-15 composite confirmed the mesoporous structure and the presence of Al in the precursors, while surface polymerization of the Al-SBA-15 was indicated by ²⁹Si-NMR. Firing the nanocomposite in a N₂ atmosphere forms the nitride phase, depending on the amount and type of carbon present, on the surface area of the precursor. Even with these precursors of high surface area, the present result was obtained using approximately twice the stochiometric amount of carbon.     

Composite SBA-15/MFI Type Materials: Preparation, Characterization and Catalytic Performance

SBA-15 type mesoporous molecular sieve was prepared and used as a parent material for synthesis of a SBA-15/zeolite composite. Thus, after addition of an aluminum source into the pristine sample, it was subjected to recrystallization in the water-vapor phase to give the SBA-15/MFI composites. The samples obtained were characterized by XRD, nitrogen sorption, scanning and transmission electron microscopies, ²⁷Al MAS NMR and FT IR. The materials after recrystallization retained their mesoporous character. Characteristics of the material revealed that all the aluminum added was inserted into the final hybrid. As shown by FT IR and NMR, at least some of aluminum was introduced into the nanoparticles of MFI and adopted four-fold coordination, typical for zeolites. Formation of Brønsted acid centres was directly confirmed by IR studies. The catalytic activity was screened in the liquid-phase isomerization of α-pinene. The main products of α-pinene transformations were camphene, limonene and γ-terpinene. The overall selectivity toward camphene + limonene was ca. 90%. Taking into account the low amount of the MFI phase present in a composite sample, calculated initial reaction rate was comparable with other catalytic systems explored in the isomerization of α-pinene.     

Direct synthesis of nano titania on highly-ordered mesoporous SBA-15 framework for enhancing adsorption and photocatalytic activity

This paper reports the synthesis of TiO₂-containing mesoporous catalysts for effectively enhancing the adsorption and photocatalytic activity. The factors that affect the photocatalytic activity of catalyst composites, including types of silica support, TiO₂ content, calcination temperature, and catalyst mass, were examined in this study. The samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and surface area analysis. The experimental results showed that incorporating TiO₂ nanoparticles into silica gel or SBA-15 frameworks could enhance the photodegradation rate more effectively than pure TiO₂. The TiO₂/SBA-15 sample displayed much higher adsorption and photocatalytic activity levels than did TiO₂/silica-gel. The pore volume and pore size of TiO₂/SBA-15 were as high as 1.317 cm³/g and 7.51 nm, respectively, which exceeded those of TiO₂/silica-gel (0.437 cm³/g and 3.68 nm, respectively). The rate constants of photocatalysis were determined. The photodegradation rate of the catalyst increased with decreasing TiO₂ content and increasing calcination temperature. The proposed method of preparing mesoporous photocatalysts is simple and suitable for mass production.     

Al-SBA-15固体酸催化合成硬脂酸三乙醇胺酯

制备了一系列Si/Al比(均为摩尔比,下同)从15到50的Al-SBA-15固体酸催化剂,并将其应用于硬脂酸与三乙醇胺的酯化反应中。结果表明,Si/Al比为25的Al-SBA-15固体酸催化剂的催化活性和选择性较高,反应6 h酯胺的酸值可降至1.78 mg KOH/g,单双酯总质量分数可达84.79%;该催化剂重复使用6次,催化活性没有明显降低,说明该催化剂具有高的稳定性。采用XRD、N2吸附脱附、透射电镜和吸附吡啶的红外光谱对催化剂的结构、比表面积和表面酸性进行了表征,结果表明,Si/Al比为25的Al-SBA-15催化剂保持了SBA-15的结构,具有大的比表面积和均一的孔径,在催化剂表面同时存在Lewis酸和Brnsted酸。     

Influence of initial Si/Al ratios on the structural,acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors

Nano-ZSM-5/SBA-15 analog composites (ZSC) were prepared in a two-step process from ZSM-5 precursors with different Si/Al molar ratios (10–50) via high-temperature synthesis in mildly acidic media (200 °C, pH 3.5) aiming to evaluate the influence of the initial Si/Al ratio on their structural, acidic and catalytic properties. The resulting materials were characterized by SAXS, XRD, FTIR, TEM, N₂ sorption, ²⁷Al solid state-NMR, NH₃-TPD, FTIR spectroscopy of adsorbed pyridine, AAS and ICP-AES. Under the applied synthesis conditions, a ZSC material with controlled distribution of nano-ZSM-5 and SBA-15 analog phases can be prepared from ZSM-5 precursors by adjusting the initial Si/Al ratio in the range of 20–30. Increasing the initial Si/Al ratio to 50, only ZSM-5 nanocrystals were obtained whereas reducing the initial Si/Al ratio to 10 led to the formation of a disordered mesoporous SBA-15 analog. The total acidity increases with the crystallinity of the ZSM-5 phase as varying the Si/Al ratio from 10 to 30 despite the decreased amount of incorporated aluminum. However, the acidity declines slightly when raising the Si/Al ratio to 50 because of the low incorporated aluminum. The catalytic performance of the ZSC materials compared to the reference materials, i.e. purely mesoporous Al-SBA-15 and purely microporous H-ZSM-5 was assessed in the gas phase cracking of cumene and 1,3,5-tri-isopropylbenzene (TIPB) as test reactions. The results show that a balanced ratio of nano-ZSM-5 and SBA-15 analog phases obtained by tuning the initial Si/Al ratio is crucial to achieve superior catalytic performance of the ZSC materials in the cracking of both cumene and TIPB.     

Desulfurization of fuels by means of a nanoporous carbon adsorbent

Mesoporous carbon, CMK-3, was prepared using hexagonal Al-SBA-15 mesoporous silica, instead of SBA-15, as a template. The synthesized materials were examined via X-ray diffraction and N₂-adsorption. The mesoporous carbon was studied for its adsorption of dibenzothiophene (DBT) from petroleum fuels. The performance of this adsorbent was compared with SBA-15 and Al-SBA-15, through which CMK-3 showed higher sulfur adsorption capabilities due to a larger mesopore volume and a higher specific surface area. The uptake capacity for DBT followed the order CMK-3 > Al-SBA-15 > SBA-15. The results confirmed the importance of the adsorbent pore size and its surface chemistry for the adsorption of DBT from liquid phase.Langmuir and Freundlich isotherm models were used to fit equilibrium data for CMK-3. The equilibrium data were best represented by the Langmuir isotherm. Kinetic studies were carried out and showed the sorption kinetics of dibenzothiophene was best described by a pseudo-second-order kinetic model.     

介孔材料Al-SBA-15的合成研究进展

Al掺杂的介孔SBA-15材料不仅保持了介孔SBA-15材料原有的结构特征,还赋予了材料新的催化活性位,成为近年来介孔材料领域最为活跃的研究对象之一。本文详细阐述了近十几年来Al-SBA-15介孔材料的研究进展,比较了各合成方法之间的区别,并讨论了Si/Al摩尔比、合成方法和反应条件等因素对Al原子嵌入SBA-15介孔骨架的效率以及介孔材料的有序性、稳定性和酸性的影响。同时总结出加深对合成机理的研究,优化合成过程,使用较简单且高效的方法制备具有完全晶化骨架和较高Al含量的介孔Al-SBA-15是未来介孔Al-SBA-15合成研究的新方向。     

n-Hexane Hydroisomerization Over Composite Catalysts Based on BEA Zeolite and Mesoporous Materials

Composite catalysts based on HBEA zeolite and Pt loaded mesoporous materials—Al/SBA-15, Al/MCM-41 and PCH—where studied in n-hexane hydroisomerization. Textural characterization showed that the Pt particles are mainly at the external surface. A synergistic effect was achieved for Pt-PCH + HBEA composite, where an increase in di-branched products was observed.     

A novel room temperature synthesis of mesoporous SBA-15 from silatrane

Well-ordered and stable two dimensional mesoporous silica, SBA-15, was synthesized at room temperature (RT) from a silatrane precursor and a non-ionic triblock copolymer (EO₂₀PO₇₀EO₂₀) as the structure-directing agent. Using a combination of small angle X-ray scattering, electron microscopy, and nitrogen gas absorption–desorption isotherms, the RT product was found to be equivalent to SBA-15 prepared using more elaborative microwave-assisted hydrothermal methods. Both synthesis routes yielded large surface areas (486–613 m²/g), pore diameters (45–67 Å) and channel volumes (0.6–0.8 cm³/g). All materials condensed as sinuous bundles of silica tubes in a morphology that approximates p6mm symmetry, but where long range order was absent. In addition, portions of the products consisted of fine crystalline mosaics or were aperiodic. The simplicity of the room temperature synthesis route may create an inexpensive and energy-saving process for the large scale production of thermally stable SBA-15 as a catalyst support.     

Synthesis of TiO2 nanoparticles on mesoporous aluminosilicate Al-SBA-15 in supercritical CO2 for photocatalytic decolorization of methylene blue

In the present study, titania nanoparticles were first constructed on mesoporous aluminosilicate Al-SBA-15 in supercritical carbon dioxide (Sc-CO₂) and the resultant samples were characterized by a combination of various techniques, such as X-ray diffraction (XRD), nitrogen physisorption, ²⁷Al MAS NMR, UV–vis diffuse reflectance spectroscopy, and transmission electron microscopy (TEM). It was identified that the Al species incorporated samples retained structures similar to that of the parent SBA-15. In addition, the content of titania loading varied with reaction temperature and time in Sc-CO₂. As-synthesized TiO₂/Al-SBA-15 samples were evaluated in terms of photocatalytic decolorization of methylene blue in aqueous solutions. It was observed that all TiO₂/Al-SBA-15 samples showed satisfactory decolorization efficiency that was much higher than those of TiO₂/SBA-15 and commercial TiO₂ under identical conditions, which could be mainly attributed to the effective adsorption capability, resulting from the extension of specific surface area after substitution of Si species with Al species.     

Synthesis and characteristics of Ce modified HY/SBA-15 and its desulfurization performance for simulated oil

A composite zeolite HY/SBA-15 has been synthesized by an overgrowth approach, and then doped with Ce by a liquid phase ion exchange process to form the Ce modified HY/SBA-15 catalyst. The synthesized materials were examined by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), BJH analysis and pyridine adsorption Fourier-transform infrared spectroscopy (Py-FTIR). The results showed the existence of two different pores sizes of 1.8 and 6 nm. Thus, the HY/SBA-15 composite includes both microporous and mesoporous structures. Desulfurization activity of the composite materials was evaluated using as simulated oil gas. The results showed that the SO_x adsorption capacity of Ce-HY/SBA-15 was enhanced by 1.97 mg/g compared to HY/SBA-15, which suggested that the Ce plays an important role in the desulfurization of simulated oil over composite zeolite. Furthermore, the Py-FTIR results revealed the relationship between the surface acids and the desulfurization performance. It was found that the weak Lewis acids were important for the improved desulfurization performance, while the Brönsted acids inhibited the desulfurization performance.     

航空煤油在不同孔径的Ag基介孔材料吸附剂上深度吸附脱硫的研究

以3种不同孔径的介孔材料MCM-41,SBA-15,大孔SBA-15(SBA-15-L)为载体,采用离子交换法制备了Ag/Al-MCM-41,Ag/Al-SBA-15和Ag/Al-SBA-15-L介孔材料吸附剂。利用XRD,N2吸附,SEM-EDS,ICP-MS等手段对所制备的吸附剂进行了表征,并在固定床上对航空煤油进行了吸附脱硫研究。结果表明,交换Ag+所制备的吸附剂依然保持介孔材料的特性,并可将含S量为150×10-6的航空煤油中的硫化物,选择性的吸附脱除到S含量低于1.0×10-6。其中,在Ag/Al-MCM-41,Ag/Al-SBA-15和Ag/Al-SBA-15-L吸附剂上,可分别得到8.0,9.0和17.0mL的清洁航空煤油(含硫量小于1.0×10-6)。实验结果也表明,所制备的吸附剂吸附脱硫性能主要取决于介孔材料载体的孔径大小,载体的孔径越大,Ag+的利用率越高,吸附剂的吸附脱硫性能越强。将吸附饱和的Ag/Al-SBA-15-L吸附剂,于空气中在350℃进行再生5h,吸附剂的吸附性能可以100%的恢复。     

Effect of different synthesis methods on the structural and catalytic performance of SBA-15 modified by aluminum

Two different aluminum-containing mesoporous Al/SBA-15 were prepared by post-synthesis method and direct synthesis method using P123 as structure directing agent and aluminum isopropoxide as the aluminum source. Samples were characterized in detail by XRD, N₂ adsorption, TEM,²⁷Al MAS NMR, and the acidic properties were performed by FT-IR of pyridine adsorption (Py-IR). The results show that Al/SBA-15 prepared by the direct synthesis method possessed higher BET surface area and larger pore volume. The acidic properties were investigated in Friedel–Crafts alkylation of phenol tert-butylation. The different synthesis method leads to distinct coordination of Al and intensity of acidity. Kinetics of the alkylation over Al/SBA-15 was also investigated. These results indicated that Al/SBA-15, prepared by post-synthetic grafting method, has more activity ability than the corresponding one synthesized by direct method since they contain more Lewis acid sites and Brönsted acid sites. The catalysts preserved almost their initial catalytic activity after four reuses.     

Dendritic SBA-15 supported Wilkinson's catalyst for hydroformylation of styrene

After PAMAM (polyamidoamine) dendrimers have been successfully grown in SBA-15 mesoporous materials, Wilkinson's catalyst (RhCl(PPh₃)₃) precursor has been tethered on these dendritic supports to produce heterogeneous catalysts for hydroformylation reaction of styrene. SBA-15 has been functionalized by two methods. In the passivation method, the silanols outside the SBA-15 pores have been passivated to preclude the rhodium precursor to be tethered outside the channels. The rhodium catalysts supported in the pore channels of this passivated SBA-15 show positive dendritic effects in enhancing the catalytic activity, regio-selectivity and stability of the catalyst by minimizing the leaching of the rhodium complex catalyst from the catalyst support to the liquid-phase media.     

Direct synthesis, characterization and catalytic performance of Al-SBA-15 mesoporous catalysts with varying Si/Al molar ratios

Through a directly hydrothermal process and utilizing Pluronic P123 triblock polymer (EO₂₀PO₇₀EO₂₀, M_av = 5800) as a template, Al-SBA-15 mesoporous materials have been prepared with different Si/Al molar ratios. The materials were characterized by XRD, ICP-OES, SEM, TEM, Py FT-IR, N₂ adsorption–desorption and NH₃-TPD techniques. Meanwhile, the catalytic performance of the Al-SBA-15 materials was investigated through Friedel–Crafts alkylation of 2,4-ditert-butyl-phenol with cinnamyl alcohol. Characterization results showed that the catalysts contain a variety of acid sites whose contents vary in a systematic manner with various Si/Al molar ratios of the materials, and have a higher catalytic activity in the alkylation reaction of phenol with tert-butanol. It was found that the Al-SBA-15 samples with good mesoporous structure are highly reusable preserving most of their catalytic activity after five cycles.     

Preparation of Ni2P/Al-SBA-15 catalyst and its performance for benzofuran hydrodeoxygenation

The Al-doped Ni2P/Al-SBA-15 catalyst with high hydrodeoxygenation(HDO)activity was synthesized by tem-perature programmed reduction at a relatively low reduction temperature of 400°C.The as-prepared catalyst was characterized by X-ray diffraction(XRD),H2temperature-programmed reduction(H2-TPR),X-ray photo-electron spectroscopy(XPS),transmission electron microscope(TEM),NH3temperature programmed desorp-tion (NH3-TPD), N2adsorption-desorption and CO uptake. The effect of Al on benzofuran (BF) HDO performance was investigated.The result indicates that the incorporation of Al into the SBA-15 support can pro-mote the formation of much uniform,smaller,highly dispersed Ni2P particles on the catalyst.The Al also contrib-utes to suppress the enrichment of P and promote more exposed Ni sites on the surface. In addition,the incorporation of Al can enhance the acid strength.The total deoxygenated product yield over Ni2P/Al-SBA-15 reached 90.3%,which is an increase of 19.4%,when compared with that found for Ni2P/SBA-15(70.9%).     

Bridged-ferrocene functionalized mesoporous SBA-15 material prepared via evaporation-induced self-assembly

Bridged-ferrocene functionalized mesoporous SBA-15 (Fc-SBA) were prepared by evaporation-induced self-assembly (EISA) of 1,1′-bis[(2-(triethoxylsilyl)ethyl)ferrocene and tetraethyl orthosilicate with polymer Pluronic P123 as a template under acid conditions. The prepared materials were characterized by N₂ sorption, XRD and TEM, and the results showed the materials exhibited highly ordered 2D hexagonal pore structure, thick pore wall with the pore width of 4.66–6.58 nm. The highly ordered structure maintained even the content of the ferrocene precursor in the initial mixture is 30 mol%. The FT-IR revealed that the ferrocene bridge is preserved during the material synthesis and subsequent extraction procedure. In the reaction of phenol hydroxylation, the phenol conversion was found to be almost the same as the homogeneous ferrocene catalyst over the Fc-SBA mesoporous materials. The selectivities of catechol and hydroquinone were about 55 and 40% respectively.     

A biomimetic mesoporous silica–polymer composite scaffold for bone tissue engineering

A biomimetic organic–inorganic composite system comprising of microspheres fabricated from combination of a biodegradable polymer poly(lactide-co-glycolide) (PLGA) and bioactive mesoporous silica (SBA-15) has been developed through sintering technique for bone regeneration applications. The morphological and structural properties of the SBA-15/PLGA composite scaffold were evaluated using electron microscopy and fourier transform infrared spectroscopy and the results showed spherical morphology and composite nature. The presence of mesopores in the silica was confirmed through nitrogen adsorption–desorption isotherms. The surface area and pore size of mesoporous silica were found to be 792 m² g^?1 and 3.7 nm, respectively. The thermal characteristics of the SBA-15/PLGA composites studied using thermogravimetry analysis shows a weight loss of around 80% with the degradation occurring at 324?°C. The prepared scaffold is also found to support the adhesion and proliferation of osteoblast cells. The expression of specific bone markers is significantly enhanced in the SBA-15/PLGA composite scaffold when compared with the pristine polymeric scaffold indicating the positive effect of mesoporous silica. Hence, these SBA-15/PLGA composite scaffolds can be explored further for bone regeneration applications.     

Al-SBA-15介孔分子筛催化合成叔丁基苯酚

采用水热直接合成法合成了n(Si)∶n(Al)为10、25和50的Al-SBA-15介孔分子筛。用X射线衍射对材料进行了表征,结果表明,Al-SBA-15保持了母体SBA-15高度有序的六方介孔结构。并研究其在苯酚与甲基叔丁基醚的烷基化反应中的催化性能,结果表明,Al-SBA-15(25)催化剂具有较高的苯酚转化率和2,4-二叔丁基苯酚选择性,最佳工艺条件为：反应温度160 ℃,n(甲基叔丁基醚)∶n(苯酚)=1.5∶1,空速1.5 h^－1。在此条件下,苯酚转化率为73.2％,2,4-二叔丁基苯酚选择性为57.9％,催化剂Al-SBA-15(25)可稳定运行约80 h。     

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.