Preparation, Characterization, and Catalytic Activity of Tin (Antimony) Substituted and Lacunar Dawson Phosphotungstomolybdates for Synthesis of Adipic Acid

Tin (antimony) substituted and lacunar Dawson phosphotungstomolybdates (a1-K10P2W12Mo5ÿO61, a1-K8P2W12Mo5SnO61 and a-Cs4SnP2W12Mo6O62,and a-Cs3SbP2W12Mo6O62) were synthesized and characterized by Fourier Transform Infra Red (FTIR), nuclear magnetic resonance (31P NMR), Visible Ultra Violet (UV-Vis) spectroscopy, and X-ray diffraction (XRD). Their catalytic properties were examined in the oxidation reaction of cyclohexanone at 90 °C and that of cyclohexene at 70 °C to adipic acid (AA), in presence of hydrogen peroxide and in free solvent. The effects of catalyst/substrate molar ratios, hydrogene peroxide flow rate, heteropolysalt composition, and cyclohexanol addition on AA yields were studied. The Cs4SnP2W12Mo6O62 (the most efficient) led to 61 % of AA yield from the cyclohexanone oxidation using a catalyst/substrate molar ratio of 13.3×10-4, H2O2 flow rate of 0.5 mL/h, and a reaction time of 20 h. Copyright © 2019 BCREC Group. All rights reserve

Preparation, characterization of mixed-valence antimony-tin phosphomolybdic polyoxometalates and application in the cyclohexanone oxidation in the presence of hydrogen peroxide

In this work, a series of polyoxometalates (POMs), as soluble salts of formula Sn1.5PMo12O40, SbPMo12O40 and $\mathrm{H}_{3-x}\mathrm{Sn}_{x1}\mathrm{Sb}_{x2}\mathrm{PMo}_{12} \mathrm{O}_{40}$ ($x=2x_{1}+3x_{2}$ and $x_{1}$, $x_{2}=$ 0–0.75) were synthesized using the cationic exchange method under stoichiometric conditions. They were characterized and tested in the oxidation of cyclohexanone using hydrogen peroxide in the absence of organic solvent, co-catalyst phase transfer compounds or surfactants. UV–Visible and X-ray photoelectron spectroscopic analyses showed a partially reduced state of POM with coexistence of the couples Mo(VI)/Mo(V), Sb(V)/Sb(III) and Sn(IV)/Sn(II), without affecting their structure, results confirmed by FT-IR and Raman spectroscopies. The reversible cyclic voltammetry analysis evidenced the valence change of the Mo species, Mo(VI)/Mo(V). The POMs are found to be active in the cyclohexanone oxidation reaction and among them the most efficient is $\mathrm{H}_{0.75}\mathrm{Sb}_{0.75}\mathrm{PMo}_{12}\mathrm{O}_{40}$ with 49% of adipic acid yield

Preparation, characterization of mixed-valence antimony-tin phosphomolybdic polyoxometalates and application in the cyclohexanone oxidation in the presence of hydrogen peroxide

In this work, a series of polyoxometalates (POMs), as soluble salts of formula Sn1.5PMo12O40, SbPMo12O40 and $\mathrm{H}_{3-x}\mathrm{Sn}_{x1}\mathrm{Sb}_{x2}\mathrm{PMo}_{12} \mathrm{O}_{40}$ ($x=2x_{1}+3x_{2}$ and $x_{1}$, $x_{2}=$ 0–0.75) were synthesized using the cationic exchange method under stoichiometric conditions. They were characterized and tested in the oxidation of cyclohexanone using hydrogen peroxide in the absence of organic solvent, co-catalyst phase transfer compounds or surfactants. UV–Visible and X-ray photoelectron spectroscopic analyses showed a partially reduced state of POM with coexistence of the couples Mo(VI)/Mo(V), Sb(V)/Sb(III) and Sn(IV)/Sn(II), without affecting their structure, results confirmed by FT-IR and Raman spectroscopies. The reversible cyclic voltammetry analysis evidenced the valence change of the Mo species, Mo(VI)/Mo(V). The POMs are found to be active in the cyclohexanone oxidation reaction and among them the most efficient is $\mathrm{H}_{0.75}\mathrm{Sb}_{0.75}\mathrm{PMo}_{12}\mathrm{O}_{40}$ with 49% of adipic acid yield

Catalytic Oxidation of Volatile Organic Compounds Alone or in Mixture over Mg₄Al_2−xCe_x Mixed Oxides

This study investigates Ce-containing MgAl layered double hydroxides (LDH), focusing on its structural and catalytic properties. Mg4Al2−xCex (x = 0; 0.4; 0.8; 2) hydrotalcite-like compounds were prepared using the co-precipitation method. The effects of cerium content and calcination temperature on the structural and catalytic properties of Ce-containing MgAl LDH were investigated. The samples were characterized by XRD, BET, Raman, XPS, and DTA/TGA techniques. The catalytic activity of the resulting compound in n-butanol oxidation was studied. Increasing the calcination temperature (from 280 to 500 °C) caused changes in the structural, textural, and reducibility properties. The Mg4Al2−xCex LDH structure series (calcined at 280 °C) exhibited the highest catalytic activity, especially for x = 2. The material’s properties improved with increased Ce content, allowing complete butanol conversion below 280 °C. The formation of active sites occupied by cerium within the LDH structure, along with its reducibility properties, contributed to the material’s performance. The Ce3+/Ce4+ redox couple in the external layers enhanced O2− diffusion and their activation into nucleophilic species, facilitating butanol transformation. Adding water vapor to the reaction mixture slightly decreased the butanol oxidation, while the presence of ethyl acetate and butanol together exhibited a mutual inhibitory effect, with butanol demonstrating a more prominent influence

Preparation of CMI-1 supported H3+xPMo12-xVxO40 for the selective oxidation of propylene

Catalysts, comprising 30 wt.% of heteropolyacids (HPAs) H3+xPMo12−xVxO40 (x = 0−3) supported on a mesoporous material CMI-1 by dry impregnation were characterized by several techniques. Their catalytic performances were compared to those of bulk HPAs in the propylene oxidation by molecular oxygen at 350 °C. The supported HPAs exhibit higher catalytic activity in propylene oxidation than the bulk ones and favoured the formation of acrolein, acetaldehyde and acetic acid, compared to the mother catalysts which lead only to the formation of COx. The enhanced oxidation catalytic activity of supported systems was attributed to the fine dispersion of H3+xPMo12−xVxO40 species on the CMI-1 mesoporous material via physical adsorption, together with the fact that the structure of both CMI-1 and HPAs remained intact during the impregnation

The primary stages of polyoxomolybdate catalyzed cyclohexanone oxidation by hydrogen peroxide as investigated by in situ NMR. Substrate activation and evolution of the working catalyst

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