DBU-Based Ionic Liquid Grafted SBA-15 Dual-Functional Catalyst for the Cycloaddition Reaction of CO2 and Epoxide

Catalysis Letters - The development of novel catalysts for the synthesis of cyclic carbonates under mild conditions remains a challenge. Herein, we designed the strategy of immobilizing DBU-based...     

SBA-15 Supported Silver Catalyst for the Efficient Aerobic Oxidation of Toluene Under Solvent-Free Conditions

The efficient SBA-15 supported silver catalysts(Ag/SBA-15) were prepared and characterized by ICP-OES, XRD, TEM, SEM, XPS and N₂ adsorption–desorption techniques. The catalysts exhibited an excellent catalytic activity for the aerobic oxidation of toluene to benzaldehyde under solvent-free conditions. Conversion of toluene and selectivity of benzaldehyde were 50% and 89% respectively over catalyst with 9.1 wt% Ag loading (10Ag/SBA-15). A wide range of substrates were tolerated under the selected reaction conditions. The kinetic study shows that the oxidation of toluene over 10Ag/SBA-15 is pseudo-first-order reaction and the activation energy E_a is 45.1 kJ/mol. A plausible mechanism involving oxygen free radicals was proposed for the aerobic oxidation reaction. Compared with the traditional method, the newly designed heterogeneous catalytic system shows better economic applicability, environmental friendliness and broader application prospects.

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The AEROPILs Generation: Novel Poly(Ionic Liquid)-Based Aerogels for CO2 Capture

CO₂ levels in the atmosphere are increasing exponentially. The current climate change effects motivate an urgent need for new and sustainable materials to capture CO₂. Porous materials are particularly interesting for processes that take place near atmospheric pressure. However, materials design should not only consider the morphology, but also the chemical identity of the CO₂ sorbent to enhance the affinity towards CO₂. Poly(ionic liquid)s (PILs) can enhance CO₂ sorption capacity, but tailoring the porosity is still a challenge. Aerogel’s properties grant production strategies that ensure a porosity control. In this work, we joined both worlds, PILs and aerogels, to produce a sustainable CO₂ sorbent. PIL-chitosan aerogels (AEROPILs) in the form of beads were successfully obtained with high porosity (94.6–97.0%) and surface areas (270–744 m²/g). AEROPILs were applied for the first time as CO₂ sorbents. The combination of PILs with chitosan aerogels generally increased the CO₂ sorption capability of these materials, being the maximum CO₂ capture capacity obtained (0.70 mmol g⁻¹, at 25 °C and 1 bar) for the CHT:P[DADMA]Cl_30% AEROPIL.     

Gold Nanoparticles Supported on the Periodic Mesoporous Organosilicas as Efficient and Reusable Catalyst for Room Temperature Aerobic Oxidation of Alcohols

Gold nanoparticles supported on the channels of a bifunctional periodic mesoporous organosilica, were found to be a highly efficient catalyst system for the aerobic oxidation of various types of alcohols into their corresponding aldehydes and ketones at room temperature. The catalyst showed no significant loss of efficiency for the aerobic oxidation of benzyl alcohol to give benzaldehyde after 7 reaction cycles.     

环己烷催化氧化制环己醇(酮)的SBA-15催化剂研究

由环己烷直接氧化生产环己酮、环己醇等含氧化合物的选择性氧化反应虽早已应用于工业生产中,但由于产物收率很低,能耗大及污染严重等方面的严重不足,一直以来,科学家们都在对该反应体系加以改进,尤其是对催化剂的改进更成为研究的重点.SBA-15是一种新型的全硅介孔分子筛,具有较大的孔径、孔径分布均一且可控,为其改性和应用提供了更广阔的空间.主要阐述了使用不同金属改性的SBA-15催化剂在环己烷催化氧化制环己醇(酮)的研究与进展.     

Use of a New Polymer Anchored Cu(II) Azo Complex Catalyst for the Efficient Liquid Phase Oxidation Reactions

A new polymer anchored copper(II) azo complex has been synthesized and characterized by using scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis, atomic absorption spectroscopy (AAS) and spectrometric methods like diffuse reflectance spectra of solid (DRS) and Fourier transform infrared spectroscopy (FTIR). The immobilized Cu(II) catalyst shows excellent catalytic activity in oxidation of cyclohexene, styrene, benzyl alcohol and ethylbenzene in presence of tert-butylhydroperoxide (TBHP) as an oxidant. The effects of different solvents, oxidants, temperature, substrate oxidant ratio and amount of catalyst were also studied. The catalytic results reveal that the polymer-anchored Cu(II) azo complex catalyst can be recycled more than five times without appreciable loss in the catalytic activity.     

A Novel Method to Immobilize Ru Nanoparticles on SBA-15 Firmly by Ionic Liquid and Hydrogenation of Arene

A novel support of the Ru nanoparticles was achieved by combination of electrostatic force and coordination. The Ru catalyst was used as heterogeneous catalyst for hydrogenation of arene. This catalyst is very active for the hydrogenation of benzene to cyclohexane even under mild conditions. The TOF of this Ru catalyst is 85.3 mol mol⁻¹ h⁻¹ at 20 °C and 1.0 MPa for complete hydrogenation of benzene. The catalytic activity did not decrease after other five runs. The excellent performance of this catalyst demonstrated that there existed synergistic effects among 1,1,3,3-tetramethylguanidinium, mesoporous SBA-15, and Ru nanoparticles.     

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.     

Cu/SBA-15 is an Efficient Solvent-Free and Acid-Free Catalyst for the Rearrangement of Benzaldoxime into Benzamide

Abstract  

Cu/SBA-15 catalysts with various Cu loadings in the range of 5–20 wt% were prepared by an impregnation method and characterized by N₂ adsorption, X-ray diffraction, temperature programmed reduction and X-Ray photoelectron spectroscopic techniques. Cu/SBA-15 catalysts are found to be highly active and selective for the Beckmann rearrangement of benzaldoxime into benzamide under solvent-free and acid-free conditions.     

An Efficient and Reusable Catalyst of Bismuth-Containing SBA-15 Mesoporous Materials for Solvent-free Liquid Phase Oxidation of Cyclohexane by Oxygen

Bismuth-containing SBA-15 mesoporous materials with different n_si/n_Bi ratio was synthesized for the first time through a direct hydrothermal method, and characterized by various physico-chemical techniques. XRD patterns indicate that the synthesized materials have an ordered two-dimensional p6mm hexagonal mesostructure. Transmission electron microscopy and scanning electron microscopy studies show that Bi-SBA-15 has well-ordered hexagonal arrays of mesoporous channels and the morphology of rod-like particles. Raman spectroscopy and UV–Vis DRS show that bismuth atoms in Bi-SBA-15 exist in a highly dispersed state, and locate mainly at tetrahedrally coordinated sites. Thermogravimetric analysis was used to observe the removal of the organic template P₁₂₃. In the catalytic test, Bi-SBA-15 is found to be a very efficient and reusable catalyst for the oxidation of cyclohexane, in a solvent-free system, with oxygen as oxidant. The influence of different parameters, such as reaction time, reaction temperature, oxygen pressure, and the dosage of catalyst on the oxidation of cyclohexane, is also investigated.     

Novel 2,2,6,6‐Tetramethylpiperidine 1‐Oxyl–Iodobenzene Hybrid Catalyst for Oxidation of Primary Alcohols to Carboxylic Acids

Novel bifunctional hybrid‐type catalysts bearing 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) and iodobenzene moieties ( 1a and 1b ) were developed and used for the environmentally benign oxidation of primary alcohols to carboxylic acids. Reaction of primary alcohols 2 with a catalytic amount of 1 in the presence of peracetic acid as a co‐oxidant under mild conditions gave the corresponding carboxylic acids 3 in excellent yields.     

离子液体催化合成2-(4-乙基苯甲酰基)苯甲酸

研究了离子液体催化合成2-(4-乙基苯甲酰基)苯甲酸。并对离子液体中[Bmim]Cl与三氯化铝的摩尔比、原料配比、反应温度和反应时间等工艺条件进行了考察。较优工艺条件为:n(AlCl3)∶n([Bmim]Cl)=1∶3,n(离子液体)∶n(邻苯二甲酸酐)∶n(乙苯)=1∶1∶1,反应温度为50℃,反应时间为4h,在此条件下,[Bmim]Cl-AlCl3催化邻苯二甲酸酐的转化率可达100%,目标产物2-(4-乙基苯甲酰基)苯甲酸的选择性达97.14%,可避免使用有机溶剂。     

Supported Ionic Liquid Catalysts (SILCA) for Preparation of Organic Chemicals

Supported Ionic Liquid Catalysts (SILCA) designed by immobilization of catalytic species residing in an ionic liquid layer, which in turn was immobilized on a solid support, were applied on the selective hydrogenation of citral in a batch reactor and in a continuous reactor. Different ionic liquids with and without addition of acid modificators were studied in terms of the catalyst activity and product selectivity. Consequently, mechanistic kinetic models describing the differences in the activity and selectivity of the catalysts consisting different ionic liquids, were developed.     

Methanobactin-Mediated Synthesis of Gold Nanoparticles Supported over Al2O3 toward an Efficient Catalyst for Glucose Oxidation

Methanobactin (Mb) is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III) to Au(0). In this paper, Au/Al₂O₃ catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w). The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al₂O₃ catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al₂O₃ catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al₂O₃ catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al₂O₃ catalysts by Mb-mediated in situ synthesis of gold nanoparticles.     

Anchoring of Copper(II) Schiff Base Complex into Aminopropyl-Functionalised MCM-41: A Novel,Efficient and Reusable Catalyst for Selective Oxidation of Alcohols

A copper(II) complex containing tetradentate N₂O₂ Schiff base ligand immobilized into aminopropyl-functionalised MCM-41 (mobile crystalline material number 41), was prepared and characterized by Fourier-transform infrared, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption and inductively coupled plasma analysis techniques. The novel heterogeneous catalyst, MCM-41-pr-NH₂-CuL, can be successfully applied for efficient and selective oxidation of different primary and secondary alcohols to the corresponding carbonyl compounds using hydrogen peroxide as an oxidant in acetonitrile at 60 °C. The effect of reaction parameters such as solvent, amount of catalyst, temperature and kind of oxidant on the oxidation of benzyl alcohol was also studied. The prepared catalyst could be recovered and reused four times without important loss of its catalytic performance. The heterogeneous MCM-41-pr-NH₂-CuL catalyst was found to be catalytically more active in the oxidation of alcohols compared to the similar type of copper(II) Schiff base complex in homogeneous media under the same reaction conditions.