Solvent-free Liquid Phase Oxidation Research Articles

Transforming Waste Clamshell into Highly Selective Nanostructured Catalysts for Solvent Free Liquid Phase Oxidation of Benzyl Alcohol

High yield production of benzaldehyde in the solvent-free oxidation of benzyl alcohol by using green catalysts is highly desirable. In this work, calcium hydroxide derived from waste clamshell was used as low-cost and environmentally friendly catalyst support (CaSUP) for Pd and V nanoparticles. The physicochemical properties of the catalysts were analyzed using X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic oxidation of benzyl alcohol to benzaldehyde was studied in a liquid phase reaction by using H2O2 as an oxidizing agent. The effects of catalyst loading, the molar ratio of hydrogen peroxide to benzyl alcohol, temperature and reaction duration were investigated. In the optimized conditions, Pd nanoparticles supported on clamshell-derived supports displayed excellent catalytic conversion (88%) and selectivity to benzaldehyde (89%). Furthermore, the catalyst can be effectively reused without a significant loss in its activity and selectivity. The high yield and stability can be related to the structural and basic properties of the catalyst. These results provide important insights into the benzyl alcohol oxidation process for industrial applications.

Supported TiO2/MCM-41 as an efficient and eco-friendly catalyst for highly selective preparation of cyclohexanone oxime from solvent-free liquid phase oxidation of cyclohexylamine with molecular oxygen

A green and efficient approach for solvent-free selective catalytic oxidation of cyclohexylamine to cyclohexanone oxime in liquid phase has been developed. The results showed that the supported 30%TiO2/MCM-41 as efficient and eco-friendly catalyst gave 78.4% of cyclohexylamine conversion with 89.1% of selectivity to cyclohexanone oxime. It has been demonstrated that the catalytic active sites are the surface titanium hydroxyl groups of catalyst. Moreover, the present catalyst can be easily separated, recycled, regenerated and reused. The probable catalytic reaction mechanism of cyclohexylamine with molecular oxygen over supported TiO2/MCM-41 was suggested. This work affords a new and environmentally friendly route for the synthesis of cyclohexanone oxime, and has important industrial application prospects.

The Impact of Hydrogen Peroxide as An Oxidant for Solvent-free Liquid Phase Oxidation of Benzyl Alcohol using Au-Pd Supported Carbon and Titanium Catalysts

The solvent free oxidation of benzyl alcohol was conducted employing Au and Pd supported catalysts, while utilizing hydrogen peroxide 35% (H2O2) as the oxidant, H2O2 is very cheap, mild, and an environment friendly reagent, which produced water as the only by-product. Various proportions of Au-Pd catalysts on carbon and titanium oxide activated as supports were synthesized through the use of sol immobilization catalyst synthesis technique. Characterization of the synthesized catalysts was performed using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). It was found that the synthesized Au-Pd/ activated carbon catalyst was beneficial for the solvent free oxidation of benzyl alcohol after its containing high surface area measuring 871 m2g-1. Analysis of the TEM data and particle dimension revealed smaller and narrower particle size of 1 wt%. Thus, the distribution of Au-Pd/C was attained. Carbon-supported bimetallic catalysts presented a higher conversion compared to catalysts that are supported titanium oxide (TiO2) for for the oxidation reaction of benzyl alcohol. It was determined that this technique was a suitable process for catalyst synthesis with high selectivity, same distribution of the particle size and activations.

Probing the Catalytic Activity of Tin-Platinum Decorated Graphene; Liquid Phase Oxidation of Cyclohexane

Pt-Sn supported on reduced graphene oxide (Pt-Sn/rGO) was synthesized and characterized by SEM, EDX, and XRD. The catalytic activity of Pt-Sn/rGO was tested for the solvent free liquid phase oxidation of cyclohexane to a mixture of cyclohexanol and cyclohexanone, also called KA oil, under mild reaction conditions. The products were analyzed gravimetrically, by UV spectrophotometer, and GC equipped with FID. The catalyst was found to be fairly active as well as selective for the desired products. The experimental data was analyzed by Freundlich, Temkin, and Langmuir adsorption isotherms. The L-H model was found to give a better fit of the data. The catalyst was fully recyclable and truly heterogeneous.

Tetranuclear Mn(II) substituted sandwich complex as a recyclable homogeneous catalyst for selective oxidation of styrene to benzaldehyde: Effect of reaction parameters and kinetics

An attempt has been made to use tetranuclear sandwich type Mn(II) substituted POMs as catalyst for solvent free liquid phase oxidation of styrene under mild reaction conditions. The present catalytic system considered as an efficient and effective approach in achieving high conversion rate with high turnover numbers (TONs) with single selective product (benzaldehyde (BA)). Surprisingly, synthesized complex behaved as homogeneous catalyst under present reaction conditions. An efficient simple approach was introduced to regenerate catalyst and further reuse up to two cycles. Kinetic investigation reveals that the oxidation reaction of styrene follows a first order kinetics in presence of H2O2 as an oxidant. The influence of temperature on rate constant was also studied and the activation energy was found to be 34.1kJmol−1.

Synthesis of ordered mesoporous silica/ceria–silica composites and their high catalytic performance for solvent-free oxidation of benzyl alcohol at room temperature

Ordered mesoporous Ce-MCM-41 and Ce-MCM-48 were prepared in which cerium was incorporated up to 29% of Ce/Si. These materials exhibit outstanding efficiency for highly selective solvent-free liquid phase oxidation of benzyl alcohol to benzaldehyde at room temperature.

Cs salt of di-manganese(II) substituted phosphotungstate: One pot synthesis, structural, spectroscopic characterization and solvent free liquid phase oxidation of styrene using different oxidants

The in-pocket Cs salt of di-manganese(II) substituted phosphotungstate was synthesized and characterized by various spectral techniques. The use of the synthesized complex for liquid phase oxidation of styrene using the environmentally benign oxidants O2 and H2O2 was explored. A kinetic study was also carried out in the case of H2O2. The activation energy was found to be 44.3kJ/mol. The catalyst recycling study indicates that the present catalyst has the potential of being used as a recyclable catalytic material after simple regeneration, without significant loss in the conversion.

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 nsi/nBi 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.

Aerobic oxidation of alcohols catalyzed by gold nanoparticles supported on gallia polymorphs

Abstract Gold nanoparticles supported on polymorphs of gallia (α-, β-, and γ-Ga2O3) were evaluated for the solvent-free liquid phase oxidation of benzyl alcohol by molecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 130 °C, 5 atm and 5 h in an autoclave. The Au/γ-Ga2O3 catalyst was also evaluated for oxidation of a range of alcohols using mesitylene as solvent under flowing oxygen at atmospheric pressure and 90 °C. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled four times without significant loss of activity. The structural data (TEM, XPS and TPSR of 2-propanol adsorption) along with the catalytic results indicate that the unique dehydrogenation capabilities of the Au/γ-gallia system are responsible for the enhanced activity achieved in the liquid phase oxidation of benzyl alcohol.

Aerobic oxidation of alcohols catalyzed by gold nano-particles confined in the walls of mesoporous silica

Gold nano-particles confined in the walls of mesoporous silica (GMS) catalysts were successfully prepared by a novel and simple technique utilizing thioether functional groups in the walls of mesoporous silica to anchor HAuCl 4. Calcination of the materials removed organic moieties and reduced the gold salt to gold nano-particles. In this procedure, the thioether groups were introduced into the silica wall via a co-condensation of tetraethyl orthosilicate (TEOS) with 1,4-bis(triethoxysily)propane tetrasulfide. These gold containing mesoporous catalysts have unusually high surface area and pore volume. The catalysts were evaluated for the solvent free liquid phase oxidation of benzyl alcohol by molecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 403 K, 15 atm and 5 h in an autoclave. The 1.5% GMS catalyst was also evaluated for oxidation of alcohols using toluene as solvent under flowing oxygen at atmospheric pressure at 353 K in a two-necked flask. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled three times without significant loss of activity.

Solvent free liquid phase oxidation of benzyl alcohol using Au supported catalysts prepared using a sol immobilization technique

Solvent free oxidation of benzyl alcohol was investigated in the absence of a base using Au catalysts prepared by sol immobilization on titania and carbon supports. Comparison between the Au supported catalysts revealed that activity and distribution of products was dependent on the nature of support and heat treatment. Specifically, heat pre-treatment of the Au catalysts has a beneficial effect in terms of activity, but is detrimental in terms of selectivity to the benzaldehyde. We conclude that sol immobilization is a suitable technique for preparing gold catalysts with small particle size and narrow particle size distributions and very high activity and selectivity for benzyl alcohol oxidation.

A novel Ce/AlPO-5 catalyst for solvent-free liquid phase oxidation of cyclohexane by oxygen

Cerium-containing AlPO-5 with an AFI structure has been prepared by hydrothermal synthesis in the presence of HF, and characterized by XRD, XPS, SEM, N2 adsorption/desorption, solid state 27Al, 31P MAS NMR and TG-DTA techniques. The results show that all the samples have good crystallinity, high dispersity of Ce and high surface area, and Ce(III) replaces the position of Al(III) and enters the framework of AlPO-5. Ce/AlPO-5 is a very efficient catalyst for the oxidation of cyclohexane in a solvent-free system with oxygen as an oxidant. In the condition of 0.5 MPa O2 and 413 K for 4 h, the conversion of cyclohexane is 13%, the total selectivity of cyclohexanol and cyclohaxnone is above 92%. In addition, the Ce/AlPO-5 catalyst is very stable in the cyclohexane oxidation system.

Solvent-free liquid phase oxidation of benzyl alcohol to benzaldehyde by molecular oxygen using non-noble transition metal containing hydrotalcite-like solid catalysts

Performance of Co–Al, Ni–Al, Cu–Al, Zn–Cu–Al, Mg–Fe, Co–Fe, Ni–Fe, Mn–Cr, Co–Cr, Ni–Cr, Zn–Cr and Cu–Cr hydrotalcite-like solid catalysts has been evaluated for the liquid phase oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as an oxidizing agent in the absence of any solvent. The Mn and Cu containing hydrotalcite-like solids show good catalytic activity in the oxidation and hence these are promising catalysts for the solvent-free oxidation reaction.