Study of the benzylation of benzene and other aromatics by benzyl chloride over transition metal chloride supported mesoporous SBA-15 catalysts

The benzylation of benzene by benzyl chloride to diphenylmethane over FeCl₃, InCl₃, GaCl₃, ZnCl₂, CuCl₂ and NiCl₂ supported on mesoporous SBA-15 at 353 K has been investigated. The redox property due to the impregnation of the SBA-15 by transition metal chloride seems to play a very important role in the benzene benzylation process. Among the catalysts, the FeCl₃/SBA-15 showed both high conversation and high selectivity for the benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > anisole. More interesting is the observation that this catalyst is always active and selective for large molecules like naphthenic compounds such as methoxynaphthalene and he can also be reused in the benzylation of benzene for several times. Kinetics of the benzene benzylation over these catalysts have also been investigated.     

Catalytic properties of the Cr-HMS materials in the benzylation of benzene with benzyl chloride

A series of chromium-containing mesoporous silicas with different Cr contents were prepared and characterized with chemical analysis, N₂ adsorption measurements (BET equation and BJH theory), X-ray diffraction, diffuse reflectance UV-visible and H₂-temperature programmed reduction techniques. Excellent results in benzylation of benzene and substituted benzenes employing benzyl chloride as the alkylating agent were obtained. The mesoporous chromium-containing materials showed both high activity and high selectivity for benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > anisole. Kinetics of the benzene benzylation over these catalysts has also been investigated.     

Zinc-containing mesoporous silicas as a catalyst for the benzylation of benzene and other aromatics by benzyl chloride

The benzylation of benzene and the substituted benzenes reaction employing benzyl chloride as the alkylating agent over a series of zinc-containing mesoporous silicas with different Zn contents have been investigated. These materials (Zn-HMS-n) have been characterized by chemical analysis, BET, and XRD. The mesoporous zinc-containing materials showed both high activity and high selectivity for benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > anisole. The kinetics of the benzene benzylation over these catalysts has also been investigated. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 3, pp. 421–425.     

Benzylation of benzene and substituted benzenes by benzyl chloride over InCl3, GaCl3, FeCl3 and ZnCl2 supported on clays and Si-MCM-41

Liquid phase benzylation of benzene by benzyl chloride to diphenyl methane over InCl₃, GaCl₃, FeCl₃ and ZnCl₂ supported on commercial clays (viz. Montmorillonite-K10, Montmorillonite-KSF and Kaolin) or on high silica mesoporous MCM-41 (at 60, 70 and 80 °C) has been investigated. The supported InCl₃, GaCl₃ and FeCl₃ showed high activity for the benzylation of benzene. The redox function created due to the impregnation of the clays or Si-MCM-41 by InCl₃, GaCl₃, FeCl₃ or ZnCl₂ seems to play a very important role in the benzylation process. Among the catalysts, the InCl₃/Mont.-K10 showed both high activity and high selectivity for the benzylation. The activity of this catalyst for the benzylation of different aromatic compounds is in the following order: benzene>toluene>mesitylene>anisole. The InCl₃ (or GaCl₃)/Mont.-K10 (or Si-MCM-41) catalyst showed high benzene benzylation activity even in the presence of moisture in the reaction mixture. The catalyst can also be reused in the benzylation for several times. Kinetics of the benzene benzylation (using excess of benzene) over the supported metal chloride catalysts have also been thoroughly investigated. A plausible reaction mechanism for the benzylation over the supported metal chloride catalysts is proposed.     

介孔载体负载Pt催化剂上α-酮酸酯的不对称氢化

以介孔材料SBA-15、经或未经Al2O3修饰的具有三维立方孔道结构的SiO2为载体,制备了负载型Pt催化剂,并用于催化α-酮酸酯底物2-氧代-4-苯基-丁酸乙酯(EOPB)和丙酮酸乙酯(Etpy)的不对称氢化反应中.结果表明,当SBA-15孔径由6.2,7.6和9.2nm依次增加时,EOPB不对称氢化的活性和手性选择...     

Deep oxidative desulfurization of fuels catalyzed by molybdovanadophosphoric acid on amino-functionalized SBA-15 using hydrogen peroxide as oxidant

This study reports the usage of molybdovanadophosphoric acid catalyst on amino-functionalized SBA-15(PMoV₂/SBA-15-NH₂) for the removal of sulfur from model oil (dibenzothiophene dissolved in n-hexane). To increase the tendency for adsorption of heteropoly acids, mesoporous SBA-15 silica was functionalized with amino groups by postsynthesis grafting, using 3-aminopropyltrimethoxy silane as the coupling agent. Immobilization of molybdovanadophosphoric acid on pure SBA-15 (PMoV₂/SBA-15) was also studied for comparison and the catalysts were characterized by physicochemical and spectroscopic methods. It was found that the catalysts exhibit high catalytic activities and PMoV₂/SBA-15-NH₂ is more durable than PMoV₂ impregnated on unmodified mesoporous SBA-15 silica. The results may bring about improvement for oxidative desulfurization of transportation fuels.     

Metallic nickel supported on mesoporous silica as catalyst for hydrodeoxygenation: effect of pore size and structure

Catalytic hydrodeoxygenation (HDO) of anisole, a methoxy-rich lignin-derived bio-oil model compound, was carried out over a series of Ni-containing (5, 10, 20, and 30 wt%) catalysts with commercial silica and ordered mesoporous silica SBA-15 as support. Both supports and catalysts were characterized by N₂ adsorption–desorption isotherms, X-ray diffraction, CO chemisorption, and transmission electron microscopy (TEM). Catalytic reaction was performed at 250 °C and 10 bar H₂ pressure. Depending on the catalyst support used and the content of active metal, the catalytic activity and product distribution changed drastically. Increase of the nickel loading resulted in increased anisole conversion and C₆ hydrocarbon (benzene and cyclohexane) yield. However, loading more Ni than 20 wt% resulted in a decrease of both conversion and C₆ yield due to agglomeration of Ni particles. In addition, Ni/SBA-15 samples exhibited much stronger catalytic activity and selectivity toward C₆ hydrocarbon products compared with Ni/silica catalysts. The differences in catalytic activity among these catalysts can be attributed to the effect of the pore size and pore structure of mesoporous SBA-15. SBA-15 can accommodate more Ni species inside channels than conventional silica due to its high pore volume with uniform pore structure, leading to high HDO catalytic activity.     

Functionalized SBA-15 and its Catalytic Applications in Selective Organic Transformations

Ordered, mesoporous SBA-15 functionalized with organic and inorganic moieties exhibits efficient catalytic activity in a variety of organic transformations. In this account, reviewing our own work, three-sets of surface-modified SBA-15 materials have been investigated. The first-set of materials consists of SBA-15 modified with organo-acidic (propyl thiol and propyl sulfonic acid) and basic (propyl amine and propyl adenine) moieties. The second-set of materials was prepared by grafting Mn complexes to the organo-functionalized SBA-15. The third-set composes of nanocrystalline metal oxides supported on SBA-15. All these catalysts have been characterized by structural and spectroscopic techniques. Catalytic activities of the first-set of solid materials have been investigated in acid/base-catalyzed reactions viz., ring-opening of epoxides with amines (producing β-amino alcohols), esterification, three-component-Mannich reactions and cycloaddition of CO₂ to epoxides. The Mn complexes grafted on organofunctionalized SBA-15 are efficient catalysts for the chemo-, regio- and stereoselective aerial oxidation of monoterpenes at ambient conditions. TiO_x, VO_x, MoO_x and WO_x supported on SBA-15 catalyzed biomimetic oxyhalogenation of aromatic compounds. In all these reactions, the functionalized SBA-15 showed high selectivity.     

Nanostructured CoMoO4 Supported on Mesoporous SBA-15 for Catalytic Oxidative Dehydrogenation of Propane to Propene

Nanostructured cobalt molybdate catalysts supported on mesoporous silica SBA-15 with different loadings were prepared by citric acid coordination-impregnation method and characterized by XRD, TEM, and BET techniques. The characterization results showed that high loading of well-dispersed crystalline CoMoO₄ may be achieved using citric acid coordination-impregnation method and the mesoporous structure of the support remained intact. The catalytic activity of these catalysts in the oxidative dehydrogenation of propane was investigated. The catalysts of nanostructured cobalt molybdate supported on mesoporous silica SBA-15 showed better catalytic performance than the corresponding bulk composite oxide and nanostructured CoMoO₄ supported on SBA-15 with loading of 13% (mass fraction, w) displayed propene yield of 16.8% at 823 K.     

Encapsulation hemoglobin in ordered mesoporous silicas: Influence factors for immobilization and bioelectrochemistry

The encapsulation of hemoglobin (Hb) on the mesoporous silicas SBA-15 and Au-doped SBA-15 (Au-SBA-15) has been studied as a model protein adsorption system. The influences of solution pH, structure of mesoporous silicas and gold nanoparticles incorporation on Hb immobilization are investigated in detail. The spectral characteristics of Hb/SBA-15 and Hb/Au-SBA-15 nanoconjugate show an absorption curve quite similar to that of native Hb, indicating that Hb retains its higher-order structure in the mesopores of SBA-15. Direct electrochemistry of Hb is obtained when Hb is adsorpted by mesoporous silicas SBA-15 or Au-SBA-15. Moreover, Hb/Au-SBA-15 exerts enhancing electron transfer ability because of the Au incorporation. Additionally, the Hb/Au-SBA-15 displays good electrocatalytic reduction of hydrogen peroxide with a detection limit of 1.0 μM, about 3 times as low as that for the Hb/SBA-15. The Hb/Au-SBA-15 exhibits higher peroxidase-like activity with the apparent Michaelis–Menton constant (K_m) of 2.87 mM, significantly lower than the 7.78 mM value for the Hb/SBA-15.     

Application of mesoporous SiO2-Modified carbon paste electrode for voltammetric determination of epinephrine

Mesoporous SiO₂ of SBA-15 is reported to modify carbon paste electrodes for detecting epinephrine (EP). Carbon paste electrodes modified with synthesized SBA-15 show high sensitivity for voltammetric determination of EP, which is attributed to the strong adsorption ability of SBA-15 to EP and large surface area of the working electrode resulted from SBA-15 modification. The effects of pH value, amount of SBA-15 and scan rate were investigated. Under optimum conditions, the anodic peak current of EP was proportional to its concentration over the range from 1.0 × 10^?6 to 6.0 × 10^?5 mol L^?1 and the limit of detection was 6.0 × 10^?7 mol L^?1. The results show mesoporous SiO₂-modified carbon paste electrodes, particularly SBA-15-modificd electrodes, create new opportunities for sensitive, simple and suitable method in the electrochemical analysis of EP.     

Mesoporous SBA-15 materials modified with PW or W active species as catalysts for the epoxidation of olefins with H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Five catalysts containing PW or W active species that anchored onto aminosilylated mesoporous silica SBA-15 by a post-grafting route were prepared and the resulting PW or W/APTES/SBA-15 hybrid materials were characterized by XRD, N₂ adsorption/desorption, surface area analysis, TEM, FT-IR, and ICP (inductively coupled plasma atomic emission spectroscopy). The names of these catalysts have been abbreviated as SBA-15m-a, SBA-15m-b, SBA-15m-c, SBA-15m-d, and SBA-15m-e according to the different active species. The PW or W active species were highly dispersed in the channels of the modified mesoporous materials. The interaction between PW or W species and amino groups grafted on the channel surface of SBA-15 led to the immobilization of PW or W species. Their catalytic activity in the epoxidation of cyclooctene with H₂O₂ as oxidant was investigated. Among them, SBA-15m-a showed the best performance, with 98.9% conversion and 98.4% selectivity. The catalyst could be reused for six times with a little decrease in activity.     

Silicotungstic acid-derived WO3 composited with ZrO2 supported on SBA-15 as a highly efficient mesoporous solid acid catalyst for the alkenylation of p-xylene with phenylacetylene

Highly dispersed silicotungstic acid-derived WO₃ composited with ZrO₂ supported on SBA-15（WZ/SBA-15） as an ordered mesoporous solid acid catalyst was prepared via a facile incipient wetness impregnation（IWI） method that active ingredients,ZrO₂ and WO₃,were impregnated into the channels of SBA-15 simultaneously with a subsequent calcination process.The relationship between catalyst nature and performance was explored by high resolution transmission elec...     

Photocatalytic decomposition of orange II over TiO2-loaded on SBA-15 prepared using a microwave process

SBA-15 mesoporous material was prepared by microwave-hydrothermal method and was used as support in TiO₂-loaded SBA-15 photocatalysts. The physical properties of these particles were investigated. We also examined the activity of these samples as photocatalysts for the decomposition of orange II. Titania loaded on a silica matrix decreases the surface area of the support as expected for TiO₂ incorporation. For TiO₂-loaded SBA-15 photocatalysts, the IR absorption at ∼960 cm⁻¹ commonly accepted as the characteristic vibration of the Ti-O-Si bond. The photocatalytic activity increases with an increase of the TiO₂ loading.     

The application of pore size tunable SBA-15 molecular sieves in direct conversion of syngas to ethanol catalyzed by RhCl<Subscript>3</Subscript> and Fe(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>

Four kinds of mesoporous molecular sieve SBA-15 (SBA-15-HCl, SBA-15-HPMo, SBA-15-HPW, and SBA-15-HSiW) were synthesized by different methods or materials. Loaded with RhCl₃ and Fe(NO₃)₃, the SBA-15-HPMo supported catalyst performed well in catalyzing direct conversion of syngas to ethanol.     

Extraction of cationic surfactant templates from mesoporous materials by CH(3)OH-modified CO(2) supercritical fluid

Extraction of cationic surfactant templates from MCM-41, MCM-48, SBA-1 and SBA-3 has been conducted using CH₃OH-modified CO₂ supercritical fluid. The supercritical fluid extraction (SFE) has been integrated with thermogravimetry (TG), X-ray diffraction (XRD) and N₂ adsorption-desorption to evaluate extraction efficiency and structural stability of mesoporous materials. Experiments of optimization indicate that the conditions of 90 bar, 85 °C, CH₃OH/CO₂ = 0.1/1.0 ml/min and 3 h are most suitable for the SFE of cationic templates. 76-95% of the cationic templates can be extracted from the mesoporous materials. XRD and N₂ adsorption-desorption studies illustrate that SFE possesses some advantages over calcination in maintaining mesoporous uniformity and structural stability when used to remove templates. The impact of curing on mesoporous structure is also dealt with.     

Thermal stability of high surface area silicon carbide materials

The synthesis of mesoporous silicon carbide by chemical vapor infiltration of dimethyl dichlorosilane into mesoporous silica SBA-15 and subsequent dissolution of the silica matrix with HF was investigated. The influence of the synthesis parameters of the composite material (SiC/SBA-15) on the final product (mesoporous SiC) was determined. Depending on the preparation conditions, materials with specific surface areas from 410 to 830 m² g⁻¹ and pore sizes between 2 and 10 nm with high mesopore volume (0.31-0.96 cm³ g⁻¹) were prepared. Additionally, the thermal stability of mesoporous silicon carbide at 1573 K in an inert atmosphere (argon) was investigated, and compared to that of SBA-15 and ordered mesoporous carbon (CMK-1). Mesoporous SiC has a much higher thermal textural stability as compared to SBA-15, but a lower stability than ordered mesoporous carbon CMK-1.     

Preparation and characterization of (SBA-15)-La2O3 host-guest composite materials

Lanthanum oxide was successfully incorporated into an SBA-15 mesoporous molecular sieve via the microwave-assisted synthesis method (MASM) for the first time, and was compared with liquid-phase grafting and thermal diffusion methods. A series of characterizations were used to characterize the prepared materials. The results showed that the preparation of (SBA-15)-La₂O₃ host-guest composite materials by MASM has the advantages of simpler operation, higher efficiency and more plentiful lanthanum oxide could be incorporated into SBA-15 compared with other methods. In the prepared host-guest (SBA-15)-La₂O₃ materials, the frameworks of the host molecular sieve were kept intact, their structures were still kept high ordered and the guest lanthanum oxide locates inside the pores of the SBA-15. The sizes of the prepared (SBA-15)-La₂O₃ samples were 340-357 nm. The prepared host-guest composite materials show the properties of luminescence, and the luminescent intensities are about 2 times of bulk La₂O₃.     

In-situ oxidation of block copolymer for producing copper oxalate or copper oxide nanowires in mesoporous channels

Copper oxalate nanowires inside the channels of mesoporous SBA-15 are created by in-situ oxidation of block copolymer in as-prepared SBA-15 samples. The pyrolysis of CuC₂O₄/SBA-15 composites under different conditions results in the formation of CuO or Cu₂O nanowires encapsulated in the nanoscale channels. The appearance, structure and composition of these materials are characterized by the X-ray power diffraction, transmission electron microscopy, N₂ adsorption-desorption isotherms, infrared spectra and inductive coupled plasma emission spectra. CuC₂O₄, CuO and Cu₂O nanomaterials filled in the channels of SBA-15 have been proven to possess the electrochemical hydrogen storage capacities of 102, 165 and 231 mAh/g in the second cycle, respectively, and are expected to have a high potential for use in practical applications.     

介孔氧化硅孔径尺寸对Eu(Ⅲ)配合物的影响

分别以十六烷基三甲基溴化铵(CTAB)和聚乙氧基-聚丙氧基-聚乙氧基三嵌段共聚物(P123)为模板剂、正硅酸乙酯(TEOS)为硅源，采用水热法合成了有序介孔分子筛MCM-41和SBA-15。选择Eu(DBM)₃phen为客体，有序介孔氧化硅MCM-41和SBA-15为载体，分别在氯仿中进行分子组装，制备出具有较强发光性能的介孔复合材料Eu(DBM)₃phen/APTES-MCM-41(EAM)和Eu(DBM)₃phen/APTES-SBA-15(EAS)。采用XRD、TEM、N₂吸附-脱附和荧光光谱等对产物的结构与性能进行了分析。结果表明，Eu(DBM)₃phen组装进有序介孔氧化硅的孔道中后，发光纯度提高。而且孔径越小，发光纯度越高。选用较大孔径的SBA-15为载体，在不显著影响发光纯度的同时，可以获得较高的发光强度。