Temperature-Controlled Hydrothermal Synthesis of α-MnO2 Nanorods for Catalytic Oxidation of Cyclohexanone.

This work describes the comparison of the catalytic performances of α-MnO2 nanorods synthesized by a facile hydrothermal approach at varying temperatures (140-200 °C). The structure and morphology of these nanorods were analyzed by XRD, N2 -physisorption, NH3 -TPD, Raman, SEM, HRTEM, and XPS. The prepared α-MnO2 nanorods also performed exceptionally well in the catalytic oxidation of cyclohexanone to dicarboxylic acids under mild reaction conditions. The characterization results conferred that there is a significant influence of hydrothermal temperatures on the textural properties, morphology, and catalytic activity. Notably, the α-MnO2 nanorods obtained from 180 °C hydrothermal conditions outperformed other catalysts with 77.3 % cyclohexanone conversion and 99 % selectivity towards acid products such as adipic acid (AA), glutaric acid (GA) and succinic acid (SA). The improved catalytic activity may be attributed to the interaction of the bifunctional Mn3+/4+ redox metal centres and surface acidic sites. The present oxidation reaction was found to be a promising eco-benign process with high selectivity for the production of commercially significant carboxylic acids from cyclohexanone.

A strategy to convert propane to aromatics (BTX) using TiNp4 grafted at the periphery of ZSM-5 by surface organometallic chemistry.

The direct conversion of propane into aromatics (BTX) using modified ZSM-5 was achieved with a strategy of "catalysis by design". In contrast to the classical mode of action of classical aromatization catalysts which are purely based on acidity, we have designed the catalyst associating two functions: One function (Ti-hydride) was selected to activate the C-H bond of propane by σ-bond metathesis to further obtain olefin by ß-H elimination and the other function (Brønsted acid) being responsible for the oligomerization, cyclization, and aromatization. This bifunctional catalyst was obtained by selectively grafting a bulky organometallic complex of tetrakis(neopentyl)titanium (TiNp4) at the external surface (external silanol ([triple bond, length as m-dash]Si-OH) group) of [H-ZSM-5300] to obtain [Ti/ZSM-5] catalyst 1. This metal was chosen to activate the C-H bond of paraffin at the periphery of the ZSM-5 while maintaining the Brønsted acid properties of the internal [H-ZSM-5] for oligomerization, cyclization, and aromatization. Catalyst 2 [Ti-H/ZSM-5] was obtained after treatment under H2 at 550 °C of freshly prepared catalyst 1 ([Ti/ZSM-5]) and catalyst 1 was thoroughly characterized by ICP analysis, DRIFT, XRD, N2-physisorption, multinuclear solid-state NMR, XPS and HR-TEM analysis including STEM imaging. The conversion of propane to aromatics was studied in a dynamic flow reactor. With the pristine [H-ZSM-5300] catalyst, the conversion of propane is very low. However, with [Ti-H/ZSM-5] catalyst 2 under the same reaction conditions, the conversion of propane remains significant during 60 h of the reaction (ca. 22%). Furthermore, the [Ti-H/ZSM-5] catalyst shows a good and stable selectivity (55%) for aromatics (BTX) of time on stream. With 2, it was found that the Ti remains at the periphery of the [H-ZSM-5] even after reaction time.

Palladium-catalyzed carbon-monoxide-free aminocarbonylation of aryl halides using N-substituted formamides as an amide source.

A carbon-monoxide-free aminocarbonylation of various N-substituted formamides with aryl iodides and aryl bromides using palladium acetate and Xantphos is described. The developed methodology is applicable for a wide range of formamides and aryl halides containing different functional groups furnishing good to excellent yield of the corresponding products. N-substituted formamides are used as an amide source wherein a Vilsmeier-type intermediate plays a major role, thus eliminating the need of toxic carbon monoxide gas.

Ultrasound assisted additive free synthesis of nanocrystalline zinc oxide.

A novel method for the synthesis of nanocrystalline zinc oxide without any additive was developed using zinc acetate and 1,4-butanediol through sonication. The structure and morphology of prepared nanocrystalline zinc oxide was investigated by various techniques like TEM, XRD, EDAX, UV-Vis spectroscopy. The solvent 1,4-butanediol played a dual role of fuel as well as capping agent eliminating addition of any extraneous species. The results showed that using ultrasound sonication is green, cost effective compared to conventional wet chemical method for ZnO nanoparticle synthesis.