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.     

Catalytic properties of antimony-SBA-15 materials in the benzylation of aromatics reactions

Antimony-containing mesoporous SBA-15 with different Si/Sb ratio has been synthesized using a post-treatment procedure with an aqueous solution of SbCl₃ and characterized by elemental analysis, XRD method, N₂ adsorption measurements (BET and BJH theory) and FTIR spectroscopy. The benzylation of aromatics by benzyl chloride has been investigated over these solids. Indeed, the antimony-containing mesoporous SBA-15 showed both high activity and high selectivity for this reaction. More interesting is the observation that Sb-SBA-15 (35) catalyst is active and selective for large molecules like naphthenic compounds such as 2-methylnaphthalene and it can also be reused in the benzylation of benzene for several times. Kinetics of the benzene benzylation over these catalysts have also been investigated. Published in Russian in Kinetika i Kataliz, 2009, vol. 50, no. 3, pp. 428–433. The article is published in the original.     

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.     

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.     

Reactions of organic exhausts and the thermal stability of catalysts

The catalytic combustion of various organic compounds has been investigated over noble and non-noble metal catalysts using a fixed bed. It was concluded that the activity order of different organic compounds on a noble metal catalyst, is toluene > 2-butanone > benzene >n-heptane≈isopropyl alcohol > acrylonitrile > cyclohexane. On non-noble metal catalyst, it is isopropyl alcohol > 2-butanone > acrylonitrile > toluene >n-heptane > cyclohexane > benzene. In order to compare the thermal stability of catalysts, the catalytic reaction of toluene has been studied over noble and non-noble metal catalysts which were calcined at various temperatures up to 900°C for 3 h.     

Highly selective synthesis of diphenyl methane via liquid phase benzylation of benzene over cobalt doped zinc nanoferrite catalysts at mild conditions

Liquid phase benzylation of benzene with benzyl chloride was investigated over different compositions of cobalt zinc ferrite (Co_xZn_1-xFe₂O_4, x-0.0, 0.25, 0.5, 0.75, 1.0) nano composites, synthesized by sol–gel method. The un-substituted cobalt ferrite catalyst exhibited excellent activity among the series effecting complete conversion of benzyl chloride in 60?min at 90?°C with 100% selectivity for diphenyl methane. The effect of various reaction parameters on the reaction was studied. Higher benzylation activity of cobalt ferrite nanocomposite is attributed to the presence of higher quantities of moderately acidic sites and a good correlation was observed between surface acidity and benzylation activity of catalysts. The catalysts are reusable without any significant structural change as indicated by X-ray Diffraction (XRD) and Atomic Absorption Spectrophotometer (AAS).     

Recent developments of heterogeneous solid catalysts for liquid-phase Friedel–Crafts type benzylation reaction

Liquid-phase Friedel–Crafts type benzylation of aromatics has been effected traditionally with catalysis by homogeneous protonic acid or Lewis acid. However, heterogeneous catalysts have the advantages, compared to their homogeneous counterparts, of facile recovering and recycling. This short article describes the recent advances in the liquid-phase Friedel–Crafts type benzylation by benzyl chloride of aromatics over redox metal: gallium (Ga), indium (In) and thallium (Tl) containing novel heterogeneous solid catalysts. Unlike conventional acidic catalyst, the benzylation activity of the Ga-, In- or Tl-based solids does not depend solely on their acidic properties, even present; these solids in their non-acidic or basic form also shows high benzylation activity. The catalytic activity order of Ga, In and Tl containing solid catalysts supported on chemically similar inert catalyst carrier is as follows: thallium/support > indium/support > gallium/support, which is quite similar to their redox potential values indicating the role of redox function in the benzylation process. A plausible reaction mechanism for the benzylation reaction over these catalysts is proposed. These heterogeneous solids are highly efficient for the Friedel–Crafts type benzylation, even in the presence of moisture, than the conventional strongly acidic solid acid catalysts.Dedicated to Dr.Vasanth R. Choudhary, National Chemical Laboratory, Pune, India     

High activities of iron-FSM-16 materials synthesized by a microwave-hydrothermal process in friedel-crafts alkylations

Iron-FSM-16 materials with different Si/Fe ratios (Si/Fe = 90, 60, and 10) have been synthesized by microwave-hydrothermal process and characterized by several spectroscopic techniques. X-ray diffraction, electron spin resonance, diffuse reflectance UV-visual and Mössbauer absorption spectroscopies allowed differentiation of several iron species. These species correspond to hematite particles, very small isolated Fe (III) species possibly incorporated in the mesoporous silica wall, and iron oxide clusters either isolated or agglomerated, forming “rafts” at the surface of the silica and exhibiting ferromagnetic ordering. Very importantly, catalytic data in benzylation of aromatic compounds such as benzene, toluene, and ethylbenzene with benzyl chloride shows that Fe-FSM-16 synthesized by microwave-hydrothermal process samples are very active and recycle catalysts.     

介孔硅材料及其负载型催化剂去除挥发性有机物的最新进展

介孔硅材料由于具有大的比表面积,均一的孔结构和大的孔径,常被用于分离、吸附和催化等领域.本文综述了近年来国内外介孔硅材料及其负载型催化剂去除各类挥发性有机物(VOCs)的研究进展,主要包括烃类、甲醇、甲醛、丙酮、苯、甲苯、萘、乙酸乙酯等.讨论了介孔硅材料的结构对VOCs吸附过程的影响;介绍了不同催化剂消除各类VOCs的催化性能及反应机理,并重点评述了甲苯在不同催化剂上的研究进展.分析结果表明,介孔硅材料的表面环境、孔道结构以及宏观形貌是影响VOCs分子在介孔硅材料上吸附的主要因素;贵金属催化剂的应用需要提高其抗中毒性以及降低成本;过渡金属的研究应着重于研发高活性的负载型过渡金属复合氧化物催化剂.最后对国内外介孔硅材料及其负载型催化剂的发展进行了展望,今后催化剂的设计可以从“氧化硅载体”和“介孔孔道”两个方面展开,这将为设计合适的催化剂处理各类VOCs污染物提供一定参考.     

AgMn/HZSM-5催化剂上室温O3氧化脱除空气中的苯：Mn含量和水含量的影响

考察了Mn含量和水含量对AgMn/HZSM-5（AgMn/HZ）催化剂上室温O₃氧化（OZCO）脱除空气中苯的影响. 研究发现,Mn含量为2.4 wt%的AgMn/HZ催化剂（AgMn/HZ（2.4））具有大的比表面积和高的MnO_x分散度,OZCO活性和稳定性最高. 反应后的程序升温脱附结果表明,2.4 wt%的Mn含量能有效抑制苯和甲酸在催化剂上的残留. 当Mn含量≤ 2.4 wt%时,催化剂分解O₃的活性在苯氧化过程中占主导;当Mn含量 > 2.4 wt%时,苯的活化起主要作用. 基于AgMn/HZ（2.4）催化剂优越的反应活性和稳定性,进一步研究了湿气流中该催化剂上苯的氧化. 与干气流相比,水汽的加入能显著提高催化剂的反应活性和稳定性,且以0.1-0.2 vol%水含量时最优.     

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.     

A Porous Polyaromatic Solid for Vapor Adsorption of Xylene with High Efficiency,Selectivity, and Reusability

Development of porous materials capable of capturing volatile organic compounds (VOCs), such as benzene and its derivatives, with high efficiency, selectivity, and reusability is highly demanded. Here we report unusual vapor adsorption behavior toward VOCs by a new porous solid, composed of a polyaromatic capsule bearing a spherical nanocavity with subnano-sized windows. Without prior crystallization and high-temperature vacuum drying, the porous polyaromatic solid exhibits the following five features: vapor adsorption of benzene over cyclohexane with 90 % selectivity, high affinity toward o-xylene over benzene and toluene with >80 % selectivity, ortho-selective adsorption ability (>50 %) from mixed xylene isomers, tight VOCs storage even under high temperature and vacuum conditions, and at least 5 times reusability for xylene adsorption. The observed adsorption abilities are accomplished at ambient temperature and pressure within 1 h, which has not been demonstrated by organic/inorganic porous materials reported previously.     

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.     

Partial Oxidation of Ethylene Over Silver Catalyst Supported on Mesoporous Materials

The partial oxidation of ethylene was investigated over silver catalysts supported on mesoporous materials. KIT-1 mesoporous materials with 30–50 wt.% silver exhibited a high conversion of ethylene and a relatively high selectivity for ethylene oxide. The selectivity of Ag/KIT-1 is enhanced by the modification of the silane.     

Functionalization of mesoporous carbon with superbasic MgO nanoparticles for the efficient synthesis of sulfinamides

Highly basic MgO nanoparticles with different sizes have been successfully immobilized over mesoporous carbon with different pore diameters by a simple wet-impregnation method. The prepared catalysts have been characterized by various sophisticated techniques, such as XRD, nitrogen adsorption, electron energy loss spectroscopy, high-resolution TEM, X-ray photoelectron spectroscopy, and the temperature-programmed desorption of CO(2). XRD results reveal that the mesostructure of the support is retained even after the huge loading of MgO nanoparticles inside the mesochannels of the support. It is also demonstrated that the particle size and dispersion of the MgO nanoparticles on the support can be finely controlled by the simple adjustment of the textural parameters of the supports. Among the support materials studied, mesoporous carbon with the largest pore diameter and large pore volume offered highly crystalline small-size cubic-phase MgO nanoparticles with a high dispersion. The basicity of the MgO-supported mesoporous carbons can also be controlled by simply changing the loading of the MgO and the pore diameter of the support. These materials have been employed as heterogeneous catalysts for the first time in the selective synthesis of sulfinamides. Among the catalysts investigated, the support with the large pore diameter and high loading of MgO showed the highest activity with an excellent yield of sulfinamides. The catalyst also showed much higher activity than the pristine MgO nanoparticles. The effects of the reaction parameters, including the solvents and reaction temperature, and textural parameters of the supports in the activity of the catalyst have also been demonstrated. Most importantly, the catalyst was found to be highly stable, showing excellent activity even after the third cycle of reaction.     

Comparative Study of Nickel Catalysts Supported on X- and Y-Zeolites

We have made a comparative study of CO/H₂ reactions over the nickel catalysts supported on X- and Y-zeolites, prepared by incipient-wetness impregnation (W) and ion-exchange (E) methods. The catalysts were characterized by surface area and volumetric chemisorption measurements, temperature programmed reduction profiles, and x-ray diffraction analysis. The results show that the turnover frequency decreases in the order; NiX(W)>NiY(W)>NiY(E)>NiX(E). The metal dispersion and catalytic activity of the catalyst are mainly affected by the support materials, the preparation methods, and the activation procedures. The high activity of NiX(W) was due to its higher reducibility, smaller nickel crystalline size, and better nickel dispersion. The low activity of NiX(E) was attributed to the poor ion-exchange of Ni with NaX, the poor reducibility, the large crystalline size, and the poor nickel dispersion.     

Mesoporous inorganic salts with crystal defects: unusual catalysts and catalyst supports

We proposed a strategy to synthesize mesoporous inorganic salt particles using the special properties of ionic liquid (IL) mixtures, and hollow mesoporous LaF₃, NdF₃, and YF₃ particles were synthesized and characterized using different techniques. The size of the mesopores in the salt particles was about 4 nm, and the materials were full of crystal defects. The LaF₃, NdF₃ and YF₃ particles were used as the catalysts for the cyanosilylation reaction of benzaldehyde using trimethylsilyl cyanide, and Ru/LaF₃ and Ru/NdF₃, in which Ru nanocatalysts were supported on the LaF₃ and NdF₃ particles with mesopores, were used to catalyze hydrogenations of benzene to cyclohexane and levulinic acid (LA) to γ-valerolactone (GVL). It was discovered that the activities of these catalysts were unprecedentedly high for these reactions. Detailed study showed that both the crystal defects and the mesopores in the salt particles played crucial roles for the extremely high catalytic activity.     

Preparation of nickel-mesoporous materials and their application to the hydrodechlorination of chlorinated organic compounds

Mesoporous materials have attracted considerable attention for use as a catalyst or a catalyst support due to their remarkable textural properties such as high surface area and large pore volume with a narrow pore size distribution. Many efforts have been made to design mesoporous materials for use in heterogeneous catalyst systems. Recent progress and results regarding the preparation of nickel-mesoporous materials and their application to the hydrodechlorination of chlorinated organic compounds were discussed in this review. Mesoporous materials were used as a support for nickel catalyst or a nickel-incorporated mesoporous catalytic material in this work. Two research areas were described and discussed in this review. One is the preparation of mesoporous alumina-supported nickel catalysts and their application to the hydrodechlorination of 1,2-dichloropropane and o-dichlorobenzene. The other is the preparation of mesoporous silica-supported nickel catalysts and their application to the hydrodechlorination of 1,1,2-trichloroethane and chlorobenzene.     

Effects of Morphology and Structural Characteristics of Ordered SBA-15 Mesoporous Silica on Release of Ibuprofen

Three kinds of highly ordered SBA-15 mesoporous materials with different pore sizes and morphologies denoted as LPS-SBA-15 (stick-like with pore size 7.28 nm), CPS-SBA-15 (stick-like with pore size 5.96 nm) and T-SBA-15 (tablet-like with pore size 4.64 nm) have been prepared, characterized and employed as carrier materials. The release behaviors of the ibuprofen in a simulated body fluid from these mesoporous silica materials were studied. The influences of pore size and exterior morphologies of mesoporous silica on the release behaviors of ibuprofen have been investigated. It has been found that the release becomes fast with increasing of pore size and slow with extending of transport pathway, and that the release rate of ibuprofen from the three kinds of SBA-15 is LPS-SBA-15 > T-SBA-15 > CPS-SBA-15. The results show that the inner structure as well as the exterior morphologies of SBA-15 mesoporous silica can seriously affect the release behaviors of ibuprofen.     

Multiporous Carbon Encapsulated Ni Nanoparticles Promoting Glycerol Valorisation towards Hydrogenation against Rearrangement†

A dual‐templating method was used to synthesize a series of hierarchical carbon supports containing different proportions of spherical macropores (ca. 200 nm in diameter) and mesoporous channels (ca. 4 nm in diameter). These and some other conventional carbon materials were subsequently impregnated with Ni and tested for the conversion of glycerol. The hierarchical catalysts exhibited a significantly higher conversion (96%) and selectivity (77%) to 1,2‐propanediol, and the specificity selectivity coefficient (6.1) towards 1,2‐propanediol against lactic acid was three times higher than that observed over a conventional Ni/C_micro catalyst (2.1). The enhanced performance of these materials, compared with the Ni nanoparticles supported on conventional carbon supports, was attributed to their high surface areas (> 1110 m²?g^?1) and large pore volumes (ca. 0.4 cm³?g^?1) permitting greater accessibility of substrate and/or intermediates to Ni active sites. Given that the concentration of accessible Ni sites in these materials is higher, a competitive benzilic‐acid‐rearrangement reaction to produce lactic acid was suppressed, leading to an enhanced hydrogenation selectivity to 1,2‐propanediol. This study evidences the potential benefits, which can be established from utilizing hierarchical support materials in the valorization of biomass.