Pore size control of monodispersed starburst carbon spheres

We describe the synthesis of highly monodispersed starburst carbon spheres (MSCS) with pore size of 1.9–3.8 nm by using monodispersed mesoporous silica spheres (MMSS) which is modified with aminopropyl group, as a starting material. The wall thickness of the MMSS could be thickened by solvothermal treatment with increasing the ratio of aminopropyl group. The thickened silica wall of solvothermally treated MMSS (MS) prevented the shrinkage of the mesoporous silica template during carbonization, causing the formation of nanospaces between carbon and the silica. Furthermore, the thicker carbon nanorods obtained from pore-expanded MS would prevent the starburst structure from collapsing. As a result, MSCS with large mesopores could be obtained after removing the silica template by hydrofluoric acid etching.     

新型磺酸基功能化的介孔MCM-41分子筛的合成及其性能研究

利用糠醇的聚合和碳化对介孔分子筛Al-MCM-41进行表面处理后,直接加浓硫酸磺化制备了一系列新型的磺酸基功能化的介孔MCM-41分子筛催化剂,并用氮气吸附-脱附(BET)、X-射线粉末衍射(XRD)、傅里叶变换红外光谱(FTIR)和吡啶-程序升温脱附(吡啶-TPD)等方法对其进行了结构表征,以乙酸与乙醇的酯化反应为模...     

One-Pot Synthesis of Spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-diones Using Sulfonic Acid Functionalized Nanoporous Silica SBA-Pr-SO3H and Study of Their Antimicrobial Properties

A novel and clean one-pot synthesis of spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-2′,5(6H)-diones via cyclocondensation reaction of isatins, 1,3-cyclohexadiones, and pyrazolone in aqueous media using SBA-Pr-SO₃H (sulfonic acid-functionalized mesoporous silica) as an efficient heterogeneous solid acid catalyst was reported. The antimicrobial activities of synthesized compounds have been tested.     

Synthesis of porous hollow silica spheres using functionalized polystyrene latex spheres as templates

Uniform sized and integrated hollow silica spheres with porous shells were prepared by using sulfuric and carboxylic acid-functionalized polystyrene latex spheres as templates, sodium silicate as a precursor, and cetyltrimethylammonium bromide as a shell structure-directing agent. When polystyrene-methyl acrylic acid latex spheres were used as the templates, the pores in the shells of the resultant hollow silica spheres were composed of both micropores and mesopores. The pores in the shells of the hollow silica spheres were mainly composed of mesopores when sulfonated polystyrene-methyl acrylic acid latex spheres were used as the templates. The shell thickness and the specific surface area of the hollow silica spheres increased with the increase in the surface acidity of the latex spheres.     

Liquid-phase diffusivity of benzene within mesoporous materials measured by a laser Raman technique

The intracrystalline diffusivities of benzene within a series of porous materials in the liquid phase (cyclohexane was used as solvent) were measured by a constant volumetric method using Raman spectroscopy at a temperature range from 323 to 393 K. Silicalite-1, mono-dispersed mesoporous silica spheres (MMSS), silica gel, γ-Al₂O₃, and SiO₂–Al₂O₃ were used as adsorbents. The intracrystalline diffusivity was calculated by parameter fitting using theoretical equations and the experimental transient change of benzene concentrations with time in response to the adsorption. The intracrystalline diffusivities of benzene within mesoporous silicas were almost the same as that within the micropore of silicalite-1, though the pore diameters of silicalite-1 and mesoporous silicas were different from each other. It is considered that the pore walls as well as the solvent molecules of cyclohexane affect the diffusion of benzene molecules in the mesopore region.     

Synthesis of Dimethyl Ether over Modified H-Mordenite Zeolites and Bifunctional Catalysts Composed of Cu/ZnO/ZrO2 and Modified H-Mordenite Zeolite in Slurry Phase

A simple, cost effective and reusable transition metal (M = Ti, V, Mn)-grafted mesoporous silica spheres were synthesized by sol–gel technique and characterized by SXRD, FTIR, UV–Vis DRS, SEM, EDS, BET-surface area, pore volume and average pore diameter. Epoxidation of cyclohexene to cyclohexene oxide over these modified silica spheres using TBHP as oxidant was performed to compare the catalytic activities. Cyclohexene oxide selectivity was recorded to be 87.5% with 72.5% conversion over 8 wt% Ti-grafted silica spheres in comparison to V and Mn-grafted catalysts.     

Effect of hierarchical meso-macroporous silica supports on Fischer-Tropsch synthesis using cobalt catalyst

Hierarchical meso-macroporous (HS-X) silica with different mesopore diameters synthesized by using rice husk ash as a silica source and chitosan as a natural template were applied for the first time as the cobalt support for Fischer-Tropsch synthesis. Unimodal mesoporous silica (MS-X) supports with equivalent mesopore diameters to HS-X supports have also been prepared for comparison. Effects of diffusion in MS-X and HS-X supports of different particle sizes on the catalytic activity and hydrocarbon selectivity were investigated. The cobalt crystallite sizes were increased with increasing mesopore diameters, whereas the highest amount of H₂ chemisorbed was found for the catalyst with the medium mesopore diameter. The HS-X supports revealed lower surface area and higher macroporosity which led to the formation of larger cobalt crystallite size and less chemisorbed H₂. However, the catalytic activity was much higher for cobalt supported on HS-X silica of both small and large catalyst particle sizes. Moreover, with the large catalyst particle size, the C₅₊ selectivity of cobalt supported on HS-X silica was much higher than that on MS-X silica, indicating the influence of mass transfer of reactants and products in macropores of HS-X supports.     

利用甲基纤维素辅助合成介孔二氧化硅微球

通过调节硅酸四乙酯（TEOS）和嵌段聚合物F127（EO₁₀₆PO₇₀EO₁₀₆）体系的pH值调控TEOS水解的速度,并利用甲基纤维素（MC）在水热条件下形成网格状液晶微滴结构的特点,一步诱导硅胶初级粒子聚沉制备微米级介孔氧化硅微球。研究了溶胶 凝胶的温度、pH值对成球性和孔结构的影响,通过氮吸附（BET）,X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、马尔文激光粒度分析（Malven）等手段分析表征了介孔氧化硅微球的形貌和孔结构,实验结果表明通过向TEOS和F127体系中加入MC,在pH＝1、80℃条件下一步水热晶化可以合成直径在4～6 μm、比表面积为450 m²·g^-1、孔径为4.2 nm的介孔氧化硅微球。     

Preparation of bicontinuous mesoporous silica and organosilica materials containing gold nanoparticles by co-synthesis method

Catalytic activities of gold strongly depend on its particle size. It is necessary to have homogeneous distributions of small gold nanoparticles with diameters between 2 and 5 nm for excellent catalytic activities. In this study, gold-containing mesoporous silica materials were prepared by a co-synthesis method. The essence of this sol–gel co-synthesis method is to combine together neutral surfactant template synthesis of mesoporous silica materials with the introduction of metal ions via bifunctional silane ligands, so that the formation of mesostructures and metal–ion doping occur simultaneously. The formation of gold nanoparticles with size less than 5 nm inside mesoporous materials (HMS, MSU, and PMO) has been achieved by this co-synthesis sol–gel process. In addition, the effects of post-treatments, such as calcination and reduction, on pore structures and nanoparticle size distributions were also investigated.     

Ordered mesoporous carbons with controlled particle sizes as catalyst supports for direct methanol fuel cell cathodes

The ordered mesoporous carbons (OMCs) with various primary particle sizes were synthesized and the effect of the particle size of the OMC supports on their performance for the oxygen reduction reaction (ORR) in direct methanol fuel cells was investigated. The ordered mesoporous silica (OMS) templates with particle sizes of 100, 300, and 700 nm (OMS-100, -300, and -700) were synthesized by changing the synthesis pH and Na content in the silica source, sodium silicate. The OMCs with similar particle sizes and morphologies (OMC-100, -300, and -700) were faithfully replicated by using the corresponding OMSs as templates and phenanthrene as a carbon source. Structural characterizations revealed that three OMCs exhibit uniform mesopores of 4–5 nm and BET surface areas of 600–800 m² g⁻¹. The Pt nanoparticles of ca. 3 nm were supported onto these OMCs and the resulting Pt/OMC catalysts were tested for the ORR. The three OMC supported catalysts exhibited the catalyst utilization efficiencies and ORR activities of similar range, with the values of Pt/OMC-300 catalyst being slightly higher than the other two catalysts.     

The particle size effect of N-doped mesoporous carbons as oxygen reduction reaction catalysts for PEMFC

The particle size effect of N-doped mesoporous carbon was investigated for ORR activity in acid condition and for issue of a mass transfer and gas diffusion in PEMFCs. As for a non-Pt ORR catalyst, nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a various particle sizes with the range of the average 20, 45 and 75 μm were synthesized by the precursor of polyaniline for the N/C species, and a mesoporous silica template was used for the physical structure for preparation of nitrogen doped OMCs. The N-doped mesoporous carbons are promoted by a transition metal (Fe) to improve catalytic activity for ORR in PEMFCs. All the prepared carbons were characterized by via scanning electron microscopy (SEM), and to evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The surface area and pore volume were increased as the particles decreased, which was effective for the mass transfer of the reactant for higher activity at the limiting current regions.     

Preparation of Mesoporous Carbons from Acrylonitrile-methyl Methacrylate Copolymer/Silica Nanocomposites Synthesized by in-situ Emulsion Polymerization

Acrylonitrile-methyl methacrylate (AN-MMA) copolymer/silica nanocomposites were synthesized by in-situ emulsion polymerization initiated by 2,2'-azobis(2-amidinopropane) dihydrochloride absorbed onto colloidal silica particles, and the mesoporous carbon materials were prepared through carbonization of the obtained AN-MMA copolymer/silica nanocomposites, followed by HF etching. Thermogravimetric analysis of AN-MMA copolymer/silica nanocomposites showed that the carbon yield of copolymer was slightly decreased as silica particle incorporated. N₂ adsorption-desorption, scan electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the mesoporous carbon materials. Both SEM and TEM results showed that disordered mesopores were formed in the obtained carbon material mainly through templating effect of silica nanoparticles. The diameter of mesopores was mainly distributed in the range from 5 nm to 15 nm. The mean pore diameter and total pore volume of the material increased as the mass fraction of silica in the nanocomposites increased from 0 to 24.93%. The significant increase of the mean pore diameter and the decrease of surface area for the carbon material prepared from the nanocomposite with 24.93% silica were caused by partial aggregation of silica nanoparticles in the polymer matrix.     

Monodispersed nanoporous starburst carbon spheres and their three-dimensionally ordered arrays

Controlled syntheses of highly monodispersed nanoporous carbon spheres via a nanocasting route are described. Previously reported monodispersed super-microporous or mesoporous silica spheres with hexagonally ordered pore channels were used as sacrificial templates, and the effect of pore sizes of the templates on the porous properties of the nanocast carbon spheres was comprehensively studied. The resultant carbon spheres exhibited a unique starburst structure derived from radially-aligned pore channels in the silica template, and had a BET surface area of over 1000 m²g^?1. It was found out that the radial alignment and sufficiently large pore size of hexagonally ordered pore channels in the silica spheres were effective to enhance the degree of order of the starburst structure in the nanocast carbon spheres and that ordered nanoporous carbon spheres could be obtained even from the MCM-41-type mesoporous silica. The diameters of the nanoporous carbon spheres were controlled in the sub-micrometer range by changing the sizes of silica templates. Furthermore, three-dimensionally ordered arrays consisting of nanoporous carbon spheres were successfully fabricated via the self-assembly of mesoporous silica/carbon composite spheres and the subsequent dissolution of the silica templates.     

Direct visualization of hetero-enzyme co-encapsulated in mesoporous silicas

In this study, a direct visualization technique was applied to the determination of a hetero-enzyme co-encapsulated in pores of mesoporous silicas in solution. Lipase and trypsin modified with fluorescent dyes, used as model enzymes, were co-encapsulated at the same instant in two kinds of mesoporous silicas – FSM-22 and SBA-15 – with pore diameters of 4.2 and 7.1 nm, respectively. A direct observation of composite materials of a hetero-enzyme and a mesoporous silica by a combination of differential interference contrast and fluorescence microscopy revealed that the enzymes were uniformly dispersed throughout the particles of the mesoporous silicas, because of the successful incorporation of the two enzymes. Moreover, lipase and trypsin co-encapsulated in the mesopores maintained their enzymatic activities in hydrolysis reactions of their substrates (triglyceride and casein, respectively), without loss of their enzymatic activities due to structural degradation.     

Preparation of Mesoporous Catalyst Supported on Silica with Finely Dispersed Ni Particles

A novel nickel catalyst supported on SBA-15 type mesoporous silica was synthesized by the grafting of N-(trimethoxysilylpropyl)ethylene diamine triacetic acid salt (EDTA) onto the surface of SBA-15 and followed by adsorption of nickel ions and calcinations (Ni-E-SBA). The catalysts prepared were characterized using XRD, TEM, TED, SAXS and N₂ adsorption/desorption measurements. While nickel particles loaded on catalysts prepared by the wet impregnation method were found to be aggregated on the outer wall of the supports, nickel particles were finely dispersed on the surface of the mesopores in the Ni-E-SBA catalyst. The catalytic performances of the prepared catalysts were evaluated using the hydrodechlorination (HDC) of 1,1,2-trichloroethane (TCEa) as a model reaction. Results showed that the Ni-E-SBA catalyst had the highest activities of the catalysts examined under the given conditions.     

Sulfonic acid-functionalized mesoporous silica catalyst with different morphology for biodiesel production

Sulfonic acid functionalized mesoporous silica based solid acid catalysts with different morphology were designed and fabricated. The synthesized materials were characterized by various physicochemical and spectroscopic techniques like scanning electron microscope-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area, thermogravimetric analysis and n-butylamine acidity. The shape of catalysts particles plays an important role in its activity. The sulfonic acid functionalized mesoporous silica catalysts of spherical shape and the cube shape were assessed for catalytic activity in biodiesel production. The catalytic biodiesel production reaction over the catalysts were studied by esterification of free fatty acid, oleic acid with methanol. The effect of various reaction parameters such as catalyst concentration, acid/alcohol molar ratio, catalyst amount, reaction temperature and reaction time on catalytic activity were investigated to optimize the conditions for maximum conversion. It was sulfonated cubic shape mesoporous silica which exhibited better activity as compared to the spherical shape silica catalysts. Additionally, the catalyst was regenerated and reused up to three cycles without any significant loss in activity. The present catalysts exhibit superior performance in biodiesel production and it can be used for the several biodiesel feedstock’s that are rich in free fatty acids.     

介孔二氧化硅KIT-6介观单晶微球的合成

以非离子表面活性剂［聚环氧乙烷（PEO）-聚环氧丙烷（PPO）-聚环氧乙烷三嵌段共聚物,P123］和阳离子聚电解质（聚二甲基二烯丙基氯化铵,PAC）形成的复合物胶束为模板,合成了具有球形形貌的介孔二氧化硅KIT-6介观单晶微球。通过扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、氮气物理吸附和热重分析（TGA）等手段对合成材料的形貌及孔结构进行了表征分析。结果表明,以有机复合物胶束为模板合成出的介孔KIT-6二氧化硅材料具有较规整的球形形貌,颗粒直径为2~3 μm,具有较大的比表面积和孔体积（747 m²/g和1.3 cm³/g）,介孔孔径为8.5 nm,且在整个颗粒内部介孔保持高度的有序排列。由于长链聚电解质PAC与硅源有着较强相互作用,样品可以在较高水热温度下（160 ℃）合成,有利于提升介观结构的稳定性。该合成方法对于介孔二氧化硅KIT-6单晶微球的合成及其在催化及吸附分离等领域的应用具有一定的启发意义。     

Synthesis and properties of mesoporous carbons with high loadings of inorganic species

A series of mesoporous carbons with high loading of silica has been synthesized by acid-catalyzed polymerization of resorcinol and formaldehyde in the presence of tetraethyl orthosilicate (TEOS), colloidal silica (silica source) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (soft template) followed by carbonization. This synthesis route can be considered as a combination of soft-templating and hard templating strategies. The resulting mesoporous silica-carbon composites contained spherical silica colloids in addition to uniformly distributed silica originated from TEOS. Dissolution of silica led to high surface area carbons, which in addition to the primary mesopores formed by thermal degradation of block copolymer template possessed spherical mesopores after dissolution of silica colloids and fine pores after removal of TEOS-generated silica species. This approach can be used to incorporate other inorganic nanoparticles into mesoporous carbons with extra microporosity created after dissolving TEOS-generated silica species.     

Preparation of hollow mesoporous silica spheres by a sol–gel/emulsion approach

Hollow mesoporous silica spheres were synthesized by a sol–gel/emulsion (oil-in-water/ethanol) approach, in which cetyltrimethylammonium bromide (CTAB) surfactant was employed to stabilize and direct the hydrolysis of oil droplets of tetraethoxysilane (TEOS). The diameters of the hollow spheres can be tuned in the range from 210 to 720 nm by varying the ratio of ethanol-to-water and their shell thickness can be mediated by changing the concentration of CTAB used in the system. BET surface areas of the hollow silica spheres are determined to be in the range of 924–1766 m² g^?1 and their pore sizes are around 3.10 nm as determined by BJH method.     

Enhanced esterification of carboxylic acids with ethanol using propylsulfonic acid-functionalized natural rubber/hexagonal mesoporous silica nanocomposites

Propylsulfonic acid-functionalized natural rubber (NR)/hexagonal mesoporous silica (HMS) nanocomposites (NR/HMS-SO₃H) with different acid contents were prepared via an in situ sol–gel process, and then applied as heterogeneous acid catalysts in the esterification of model carboxylic acids and palm fatty acid distillate (PFAD) with ethanol. The NR/HMS-SO₃H composites exhibited a wormhole-like framework with enhanced wall thickness, high mesoporosity, and enhanced hydrophobicity. The NR/HMS-SO₃H composites exhibited a superior catalytic performance compared to a commercial Nafion/silica composite solid acid catalyst (SAC-13) and conventional propylsulfonic acid-functionalized HMS (HMS-SO₃H). The NR/HMS-SO₃H catalyst can be regenerated and reused in the esterification.