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Methylsulfonylmethane (MSM) is a newly discovered human nutrient that has significant health care and therapeutic function. In this work, we developed a new type of catalyst-free air oxidation of dimethyl sulfoxide (DMSO) to MSM under relatively mild conditions based on the mechanism of isopropylphenyl free radicals (R·) activating molecular oxygen (O2) generating reactive oxygen species (ROS). Experimental results showed that cumene as a solvent, due to its active tertiary sp3 C–H bond, promotes the efficient catalyst-free air oxidation of DMSO to MSM under relatively mild optimized conditions. Based on the quenching test of free radicals and theoretical calculation of the activation energies of two oxidation pathways of isopropylphenyl peroxy radicals (ROO·) and cumene hydroperoxide (CHP), it has been demonstrated that ROS in this reaction is mainly ROO· and hydroxyl radicals (HO·). Furthermore, we proposed a possible catalyst-free air oxidation mechanism. This work provided a simple and cost-efficient approach for the green synthesis of MSM. [ABSTRACT FROM AUTHOR]

para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al2O3, to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81% via a cascade dehydroaromatization–hydrodeoxygenation (DHA–HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx-modified Pd/Al2O3 catalyst compared to Pd/Al2O3, thus tuning the preferential adsorption mode of the substrate from η2-(C,O), the key transition state of the decarbonylation reaction, to the η1-(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA–HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis. [ABSTRACT FROM AUTHOR]

Abstract: It is firstly discovered that ZnCl2 modified γ-Al2O3 solid Lewis acidic catalysts (ZnCl2/γ-Al2O3), which are prepared by solid-state reaction, are very active and extremely selective for the preparation of guaiacol by the vapor phase O-methylation of catechol with methanol in a fixed-bed reactor at 553K, under the optimum reaction conditions, the conversion of catechol and the selectivity for guaiacol are up to 81.8 and 90.9%, respectively over ZnCl2 (10%)/γ-Al2O3 and by far better than the reaction results over the solid Brønsted acid catalyst (HY), proposing that the weak coordination of catechol with the Zn2+ sites of ZnCl2/γ-Al2O3 plays a key impact on the high selectivity for guaiacol. The recycling tests indicate that the modification of ZnCl2 could significantly improve the catalytic stability of γ-Al2O3 by it efficiently restraining the catalyst''s coking. And the deactivation of ZnCl2/γ-Al2O3 is mainly caused by its ZnCl2 leaching and surface coking in the run procedure, therefore its catalytic activity can be only partly recovered by the calcination in air at 773K for 4h. [Copyright &y& Elsevier]

Abstract: Novel hexadentate binding 8-quinolinolato manganese(III) complexes were proposed and conveniently synthesized for the epoxidation of olefins with aqueous hydrogen peroxide in water–acetone media with ammonium acetate and acetic acid as additives. The catalytic efficiencies of the suggested catalysts were found to be obviously superior to the traditional tetradentate salen–MnIIICl, due to their special hexadentate binding structures that could be easily converted to the corresponding pentadentate with pendant hydroxyl groups by opening an axial Mn the reaction media, as supported by UV–vis spectra, in situ cyclic voltammetry, and quartz crystal microbalance characterizations. [Copyright &y& Elsevier]

[Display omitted] • Simultaneous steep increase of BET and construction of CN-based homojunction were achieved. • The CN-based homojunction photocatalytic CO 2 conversion performance was 13.8 or 16.1 times higher than that of pristine CN. • The adsorption and activation properties of catalysts for CO 2 were studied using the first principles calculations. • A detailed mechanism of photocatalytic CO 2 conversion was proposed based on in situ infrared characterization. The value-added conversion of CO 2 by photocatalytic reduction is considered as a potential way to solve the current energy and environmental crisis. In this paper, we report that a mechanical mixture of the as-thermally polymerized melamine (Me)- and 3-amino-1,2,4-triazole (AT)-based nitride carbons (MCN and TCN) can turn into a homojunction material (MTCN) by a calcination under air. A series of characterizations and photo-catalytic tests, combined with DFT calculations, support that the constructed MTCN has an improved porosity and photoelectric conversion efficiency. And the nitrogen-rich structure not only broadens the visible light response range but also provides stronger Lewis basic sites for the adsorption and activation of CO 2 at the surface. As a result, MTCN exhibits the most outstanding performance on tetracycline degradation under visible light illumination. In particular, its photo-catalytic efficiency for the visible-triggered CO 2 reduction under normal temperature and pressure can reach 7.75 μmol·g−1·h−1, which is 13.8 or 16.1 times higher than the single MCN or TCN. This work provides a facile pathway to construct CN-based homojunction photocatalyst for the efficient conversion of CO 2 into valuable products. [ABSTRACT FROM AUTHOR]

Decatungstate (DT) is very potential photo-catalyst for the dioxygens (O 2)-based selective oxidation but still needs to be improved in photo-catalytic efficiency and regeneration. This paper discloses that Au nanoparticles (NPs)-loaded DT (Au/DT) is conveniently synthesized via the reduction of chloroauric acids introduced in the synthesis of DT. A series of characterizations and quenching tests support that the doped Au NPs can remarkably improve the visible-light- harvesting and photo-excited quantum efficiencies of DT, and as the excellent electronic transport carriers, they also plays an additional role in converting O 2 into the active superoxide (•O 2 -) anion radical. As a result, the suggested Au/DT exhibits a significantly enhanced photo-catalytic efficiency for the visible-light-triggered selective oxidation of inert hydrocarbons under 25–28 °C and 1 atm pure O 2 atmosphere. Under optimized conditions, the best 1%Au/DT achieves 64.2% conversion and 93% acetophenone selectivity in the photo-oxidation of ethylbenzene and it has an outstanding regeneration ability. The hybridizing engineering (HE) strategy of Au NPs doping can improve DT's visible light harvesting efficiency and redox capacity via lowering frontier orbital energy levels, and in which Au NPs as the excellent electronic transport carriers also hoist DT's photo-excited quantum efficiency and the reactivity of O 2 in the visible light-driven selective oxidation of inert hydrocarbons. [Display omitted] • Firstly realizing the doping of Au NPs in the cage of non-lacunary decatungstate (DT). • Doped Au NPs remarkably improve DT's photo-physiochemical and redox properties. • Doped Au NPs play a crucial role in converting O 2 into active •O 2 - anion radical. • Au/DT possesses significantly enhanced visible-light-catalytic performance. • Au/DT has a good application potential in photo-catalytic oxidation of hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract: A series of S-containing organic–inorganic hybrid mesoporous silicas were synthesized and used as supports for the fabrication of supported gold nanoparticle catalysts. It was found that the location and structure of organic moieties in these mesostructures played a crucial role in the dispersion level of gold nanoparticles, and thus, had a significant effect on the catalytic performance. Under optimum conditions, the gold nanoparticles supported on a periodic mesoporous organosilica with bridging disulfide-ionic liquid moieties showed excellent catalytic performance and reusability in epoxidation of styrene in the presence of H2O2-acetonitrile. Moreover, whole epoxidation process and role of gold nanoparticles were proposed. [Copyright &y& Elsevier]

Abstract: A novel solvent-regulated phase transfer catalyst of polymeric chiral salen Mn(III) complex with chiral diamine bridging was synthesized and its performance in the asymmetric epoxidation of styrene was investigated. In comparison with its low molecular weight counterpart of the homogeneous monomeric chiral salen Mn(III) complex, the polymeric chiral salen Mn(III) complex showed similar yield and enantioselectivity of the epoxide under the same reaction conditions. The effects of axial base, reaction temperature, and solvent on the catalytic performance of the polymeric chiral salen Mn(III) complex were investigated systematically. It was found that, under optimal reaction conditions, the yield of the epoxide and the enantioselectivity were as high as 98 and 47%, respectively. Furthermore, the polymeric chiral salen Mn(III) complex could be conveniently recovered for recycled use. Indeed the complex could be reused at least three times without significant losses of both activity and enantioselectivity. [Copyright &y& Elsevier]