Active Catalysts For Selective Oxidation Research Articles

Synthesis of salicylaldehyde through oxidation of o-cresol: Evaluation of activity and selectivity of different metals supported on OMS-2 nanorods and kinetics

Octahedral molecular sieve (OMS-2) was synthesized by the hydrothermal method and modified by the impregnation of different metals to give M/OMS-2 catalysts (where M = V, Cr, Fe, Co, and Mo). All these catalysts were tested in the oxidation of o-cresol to 2-hydroxybenzaldehyde (or salicylaldehyde, SAL). Among all M/OMS-2 catalysts, 5% Co/OMS-2 was found to be the most active catalyst for selective oxidation of o-cresol to SAL. Effect of several oxygen sources such as air, hydrogen peroxide (H2O2), molecular oxygen (O2), and tert-butyl hydroperoxide (TBHP) was studied for the oxidation of o-cresol. There was a complete conversion of o-cresol with 98% yield of SAL at 5 atm O2 pressure and 80 °C in 2 h. Additionally, the catalysts (virgin as well as reused forms) were characterized by FESEM, EDS, HR-TEM, XRD, CO2-TPD, TPR, Raman Spectra, BET surface area analysis, XPS, and DSC-TGA. The reaction kinetic model was developed using Mars van Krevelen mechanism. The catalyst was found to be inexpensive, robust, active, and showed very good reusability of 4 cycles, which makes it an attractive choice for o-cresol oxidation to SAL. The atom economy of the oxidation process is 98.15%. Thus, this process is an example of the synthesis of a vital chemical entity, salicylaldehyde, at mild reaction condition by a novel clean and green route.

Au–Pd NPs immobilised on nanostructured ceria and titania: impact of support morphology on the catalytic activity for selective oxidation

Au–Pd colloidal NPs immobilised on ceria nanorods are highly active catalysts for selective oxidation.

Au‐Pd Bimetallic Nanoparticles Immobilised on Titanate Nanotubes: A Highly Active Catalyst for Selective Oxidation

AbstractIn this work, a highly active Au‐Pd/Ti‐NT catalyst has been produced by using colloidal synthesis and immobilisation on essentially sodium‐free Ti‐nanotubes (NTs). The new catalyst has markedly superior catalytic activity (turnover frequency>19 000 h−1) for the selective oxidation of benzyl alcohol compared with similar catalysts reported in the literature, and to Au‐Pd catalysts supported on Ti‐NTs prepared by adsorption, as well as conventional Au‐Pd/TiO2 prepared by impregnation. The superior catalytic activity of the catalyst is shown to be a result of the high metal dispersion on the external surfaces of Ti‐NTs, the narrow particle size distribution and the consistent formation of Au‐Pd mixed alloy nanoparticles in close to a 1:1 weight ratio. In repeated use, the Au‐Pd/Ti‐NT catalyst showed only a modest fall in activity, which is shown by FTIR to be associated mainly with the irreversible adsorption of benzoic acid and benzyl benzoate by the catalyst.

Metal nanoparticle catalysts decorated with metal oxide clusters

Au nanoparticles decorated with mononuclear Ti-oxo units dispersed in silica clusters were formed by activating Au nanoparticles (~2 nm) stabilized with Ti- and amine-functionalized siloxane oligomers. These Au nanoparticles were active catalysts for selective oxidation of propane to acetone, and the activity increased with increasing Ti density.

Selective oxidation of benzyl alcohol to benzaldehyde with hydrogen peroxide over alkali-treated ZSM-5 zeolite catalysts

A stable, economic and high active catalyst for selective oxidation of benzyl alcohol (BzOH) was developed by treating ZSM-5 zeolite with sodium hydroxide solution. The changes resulted by alkali-treatment in crystallinity, composition, structure parameters and acidities of alkali-treated ZSM-5 zeolites were examined by XRD, ICP, N2 adsorption-desorption, scanning electron micrographs (SEM), temperature program desorption (TPD) and Fourier transform infrared spectroscopic (FT-IR). The results showed that the specific MFI structure was preserved and the intrinsic micropores were kept without obvious change, the amount of Lewis acid sites and the external surface area were evidently increased after alkali-treatment. Without any organic solvent, the catalytic performance of alkali-treated ZSM-5 zeolite was investigated in selective oxidation of BzOH with hydrogen peroxide (H2O2), and the effects of reaction temperature, reaction time, dosage of catalyst, dosage of H2O2 and SiO2/Al2O3 ratio of as-received zeolites on catalytic selective-oxidation of BzOH were investigated. The results showed that the conversion of BzOH and the selectivity to benzaldehyde (BzH) were about 53% and about 86% respectively under reflux for 4h in water. At the same time, the catalyst was very stable and could be reused for more than six times.

ChemInform Abstract: Copper‐Triethanolamine Complex as Efficient and Active Catalyst for Selective Oxidation of Alkylarenes to Phenyl Ketones by tert‐Butylhydroperoxide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Copper-triethanolamine complex as efficient and active catalyst for selective oxidation of alkylarenes to phenyl ketones by tert-butylhydroperoxide

Several types of alkylarenes were selectively oxidized to the corresponding α-phenyl ketones in moderate to good selectivities and conversions using tert-butylhydroperoxide in the presence of a tetranuclear copper-triethanolamine complex under mild reaction conditions.

TiO 2 nanotube-supported ruthenium(III) hydrated oxide: A highly active catalyst for selective oxidation of alcohols by oxygen

Ruthenium(III) hydrated oxide was deposited onto the surface of TiO 2 nanotubes via ion exchange followed by alkali treatment. The catalytic activity of Ru(III)/TiO 2 catalyst for the selective oxidation of alcohols by oxygen was studied in a continuous multichannel, compact reactor. It was found that the activity of Ru(III)/TiO 2 (turnover frequency [TOF] ⩽ 450 h −1) is greater than that of a recently reported Ru(III)/Al 2O 3 catalyst (TOF = 335 h −1), and that the ruthenium loading could exceed 8 wt% without any significant loss of specific catalytic activity. High-resolution transmission electron microscopy and X-ray diffraction data show that ruthenium is highly dispersed on both the inner and the outer surfaces of the mesoporous TiO 2 nanotubes with the diameter of nanoparticles between 1.2 and 2.4 nm, and is easily accessible by reactant molecules.

Hydrotalcite like compounds with low Mo-loading active catalysts for selective oxidation of cyclohexene with hydrogen peroxide

Several Mo-containing hydrotalcite-like compounds (HTlcs-Mo) were prepared by different ionic exchange procedures using as parent a synthetic hydrotalcite Mg 3Al(OH) 8(CO 3) 0.5·2H 2O with a composition similar to the natural occurring mineral. Their physico-chemical properties determined by chemical and TG–DTA analyses, XRD, BET, FTIR, SEM-EDX, DR–UV–vis and Raman spectroscopy, were compared to those of two HTlcs-Mo prepared by direct synthesis at constant pH = 10 and low or respectively high supersaturation. The catalytic activity of these solids towards cyclohexene oxidation with hydrogen peroxide was investigated. The catalytic activity was mainly influenced by the basic properties of the catalysts, which varied depending on the preparation procedure. The best catalysts for hydroperoxidation were found to be those having a low Mo content (about 2.5–2.8%) in the form of MoO 4 2− species, and higher Mg concentration in the brucite layer. The catalysts containing also Mo 7O 24 6− species were more active for epoxidation.

Preparation of α,β‐Acetylenic Ketones by Catalytic Heterogeneous Oxidation of Alkynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparation of alpha, beta-acetylenic ketones by catalytic heterogeneous oxidation of alkynes.

Covalent grafting of iron phthalocyanines onto silica affords active catalysts for selective oxidation of alkynes and propargylic alcohols to alpha, beta-acetylenic ketones, highly valuable precursors in the preparation of fine chemicals.

New SiO2-bound mo dimers: active catalysts for selective oxidation of propene to acrylaldehyde

SiO2-bound molybdenum(VI) dimers (Mo–Mo 0.330 nm)with bridging oxygen atoms (Mo-O 0.194 nm), prepared from Mo2(η3-C3H5)4-SiO2 followed by treatment with H2 or O2, showed high activity in the selective oxidation of propene to acrylaldehyde.