N-Hydroxyphthalimide on a Polystyrene Support Coated with Co(II)-Containing Ionic Liquid as a New Catalytic System for Solvent-Free Ethylbenzene Oxidation

The oxidation of ethylbenzene using dioxygen was carried out applying a new catalytic system—heterogeneous N-hydroxyphthalimide (PS-NHPI) coated with an ionic liquid containing CoCl2. The catalytic system represents a combination of solid catalyst with ionic liquid layer (SCILL) and supported ionic liquid phase (SILP) techniques, wherein the resulting system utilizes CoCl2 dissolved in the 1-ethyl-3-methylimidazolium octyl sulphate ([emim)][OcOSO3]) ionic liquid phase that is layered onto the solid catalyst support. PS-NHPI was obtained by immobilizing N-hydroxyphthalimide on chloromethyl polystyrene resins by ester bonds. It was observed that novel SCILL/SILP systems significantly improved the selectivity toward acetophenone. We also demonstrate that these systems can be separated from the reaction mixture and recycled without appreciably reducing its activity and selectivity.

OXIDATION PRODUCTS OF ETHYLBENZENE AND ITS SUBSTITUTED BY OZONE IN ACETIC ACID

Based on the obtained kinetic regularities and the mixture of the products of the reaction of ethylbenzene oxidation with ozone in acetic acid, the scientific bases of the technology of synthesis of acetophenone was developed. It is shown that in the ozonation conditions, in the presence of manganese (II) acetate, it is possible to direct oxidation mainly through the ethyl group of the substrate with the formation of aromatic products. The technological parameters are studied and the optimal conditions for the process realization are ascertained. The obtained experimental and theoretical results allowed us to propose a new low-temperature low-waste method of acetophenone production, which ensures the efficiency of the process due to the mild oxidation conditions (288 K, atmospheric pressure) and the reduction of toxic waste. The technology can be an alternative to existing methods of the synthesis of aromatic ketones.

Recent Development of Catalytic Materials for Ethylbenzene Oxidation

Catalysts are well-known to convert alkylbenzenes at high thermal condition to a number of useful products. However, the current schemes of transformation are not suitable for the hazard-free industrial applications because their reactive intermediates are transformed to a variety of side products that often retard the optimum yield and cause environmental pollutions. It is also observed that the formation of products depends on a wide range of parameters which are extremely difficult to control and often incur extra cost. Recently, heterogeneous catalysts have received huge commercial interests for the oxidation of alkylbenzene into carbonyl compounds which are platform chemicals in various synthetics and fine chemicals. This review is an up-to-date documentary on various catalysts used for the oxidation of alkyl-substituted benzenes along with their reaction condition and selectivity profiles. This work updates our knowledge for the selection and/or design of novel catalysts for the chemists and engineers in the industrial and academic settings.

N-Hydroxyphthalimide Supported on Silica Coated with Ionic Liquids Containing CoCl2 (SCILLs) as New Catalytic System for Solvent-Free Ethylbenzene Oxidation

N-Hydroxyphthalimide was immobilized via ester bond on commercially available silica gel (SiOCONHPI) and then coated with various ionic liquids containing dissolved CoCl2 (SiOCONHPI@CoCl2@IL). New catalysts were characterized by means of FT IR spectroscopy, elemental analysis, SEM and TGA analysis and used in ethylbenzene oxidation with oxygen under mild solvent-free conditions (80 °C, 0.1 MPa). High catalytic activity of SiOCONHPI was proved. In comparison to a non-catalytic reaction, a two-fold increase in conversion of ethylbenzene was observed (from 4.7% to 8.6%). Coating of SiOCONHPI with [bmim][OcOSO3], [bmim][Cl] and [bmim][CF3SO3] containing CoCl2 enabled to increase the catalytic activity in relation to systems in which IL and CoCl2 were added directly to reaction mixture. The highest conversion of ethylbenzene was obtained while SiOCONHPI@CoCl2@[bmim][OcOSO3] were used (12.1%). Catalysts recovery and reuse was also studied.

Noncontact catalysis: Initiation of selective ethylbenzene oxidation by Au cluster-facilitated cyclooctene epoxidation

Traditionally, a catalyst functions by direct interaction with reactants. In a new noncontact catalytic system (NCCS), an intermediate produced by one catalytic reaction serves as an intermediary to enable an independent reaction to proceed. An example is the selective oxidation of ethylbenzene, which could not occur in the presence of either solubilized Au nanoclusters or cyclooctene, but proceeded readily when both were present simultaneously. The Au-initiated selective epoxidation of cyclooctene generated cyclooctenyl peroxy and oxy radicals that served as intermediaries to initiate the ethylbenzene oxidation. This combined system effectively extended the catalytic effect of Au. The reaction mechanism was supported by reaction kinetics and spin trap experiments. NCCS enables parallel reactions to proceed without the constraints of stoichiometric relationships, offering new degrees of freedom in industrial hydrocarbon co-oxidation processes.