Direct Oxidation Of Cyclohexene Research Articles

Influence of reactional parameters in the adipic acid synthesis from cyclohexene using heterogeneous polyoxometalates

One-step oxidative cleavage of cyclohexene to adipic acid using H2O2 as oxidizing agent and heteropolysalts as heterogeneous catalysts was successfully performed, without the use of additives, such as organic or inorganic acids. The K3PW12O40, K3PMo12O40, Cs3PW12O40 and Cs3PMo12O40 heteropolysalts were synthesized by ion exchange of the respective heteropolyacids using cesium and potassium carbonates. The catalysts were thermally treated at 200 or 600 °C and characterized by Raman spectroscopy, thermogravimetric analysis, X-ray fluorescence (XRF) and photoelectronic X-ray spectroscopy (XPS). Raman results showed that the Keggin structure of the polyoxometalates was successfully obtained for both heteropolyacids and heteropolysalts and remained stable even after thermal treatment at 600 °C. XRF analysis confirmed the insertion of the cations (Cs+ and K+) into the heteropolysalt structures. All catalysts completely converted cyclohexene within 24 h and they were selective to adipic acid. The best catalyst, K3PW12O40 calcined at 600 °C (KPW-600), achieved the highest adipic acid yield (83 %). In this work, we associate the best activity of the KPW-600 heteropolysalt not only to its greater acidity, but also to the higher concentration of (W-O-W)/W species (identified by XPS). Both properties are fundamental for the oxidation reaction of cyclohexene to adipic acid under the experimental conditions used. The results showed that the presence of peroxide species is essential, mainly to favor oxidation reactions, such as the Baeyer-Villiger rearrangement reaction. A reaction scheme for the oxidation of cyclohexene to adipic acid with the best catalyst (KPW-600), was proposed based on our kinetic studies and literature results. In addition to the main route of adipic acid formation from the direct oxidation of cyclohexene, undesirable parallel reactions of the rearrangement of 1,2 - cyclohexanediol and allyl oxidation were also observed. The influence of reaction conditions was also investigated, as well as the reuse of the most promising catalyst.

Activity of Bimetallic Gold-Iron Catalysts in Adipic Acid Production by Direct Oxidation of Cyclohexene with Molecular Oxygen

Activity of Bimetallic Gold-Iron Catalysts in Adipic Acid Production by Direct Oxidation of Cyclohexene with Molecular Oxygen

Improving Energy Efficiency of Process of Direct Adipic Acid Synthesis in Flow Using Pinch Analysis

Together with transport and chemical intensification, process-design intensification is situated under the umbrella of Novel Process Windows and heads for integrated and simplified smart-scaled (micro/meso) flow process design in a holistic picture. As a demonstration example, the direct oxidation of cyclohexene with hydrogen peroxide for adipic acid synthesis is considered. It provides an innovative alternative to the two-step industrial process currently used. It is aimed to design an energy efficient process for this novel route. For systematically and holistically analyzing the process and, in particular, its heat integration, pinch analysis is employed. With the use of the software Aspen Energy Analyzer, the available energy recovery potential is determined, and a heat exchanger network is designed that gives a minimum total annual cost. Compared with the initial heat exchanger network where energy requirements are supplied with utility streams, the improved heat exchanger network designed enables 70% saving in operating cost which enables to pay back the extra capital cost requirement in 8 months. The heat exchanger selection is also a very important design consideration. The utilization of compact heat exchangers (including microchannel-based), which have proven advantages in thermal effectiveness, safety, and reduced size, can enable further benefits in terms of total plant cost and plant complexity. The opportunity to have lower operable temperature approach gives the possibility to lower the utility requirement by 20%. For the case of temperature cross, the additional capital cost requirement can be halved. As a consequence, for operation of flow processes using micro/meso-reactors at large scale, the utility/energy support and heat exchanger selection should be taken into consideration. Such holistic thinking has not been detailed and justified so far for micro- or similar smart-scale flow reactors, to our best knowledge.

Direct Oxidation of Cyclohexene with Inert Polymeric Membrane Reactor

In this work, the use of PVDF flat membranes as contactors for direct solvent-free biphasic oxidation of cyclohexene to adipic acid has been reported. The oxidation has been carried out using 30% H2O2 and ammonium molybdate ((NH4)6Mo7O24) in the presence of succinic acid. The effect of different membranes as interfaces between the organic phase, containing cyclohexene, and the aqueous phase, with the oxidant and catalyst, has been studied and related to conversion and selectivity.

Clean Synthesis of Adipic Acid by Direct Oxidation of Cyclohexene with H2O2 Catalyzed by Na2WO4×2H2O and Acidic Ionic Liquids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cleavage of alkenes by anodic oxidation

Oxidative cleavage of olefinic double bonds to carboxylic acids, aldehydes or ketones is one of the important reactions in organic synthesis. Ozonolysis is mostly applied for this purpose, however, high costs for safety precautions in technical scale conversions demand alternatives. For this purpose different electrochemical methods are investigated. In the direct oxidation of cyclohexene at a platinum or graphite anode no cleavage occurs, but substituted and rearranged products are obtained. At the boron doped diamond electrode (BDDE) aliphatic olefins with high oxidation potential are not converted. Electrochemical ozonolysis by oxidation of water to ozone at the lead dioxide electrode leads to carboxylic acids as cleavage products in high material yield but low current yield. Anodic bromo-formyloxylation followed by an anodic cleavage provides a two step conversion of cyclohexene to hexane-1,6-dial derivatives. Thereby anodic discharge of bromide in formic acid leads to (2-bromocyclohexyl)-formate, which is converted to cyclohexane-1,2-diol and the major part of potassium bromide is recovered for the next cycle. This electrochemical conversion appears to be an attractive alternative to chemical oxidations with oxygen and catalysts or with hydrogen peroxide. The diol is cleaved in high yield to hexane-1,6-dial or its acetal either directly or indirectly with periodate as mediator.

Clean Synthesis of Adipic Acid by Direct Oxidation of Cyclohexene with H2O2 catalysed by Na2WO4.2H2O and Acidic Ionic Liquids

Without any other organic solvents or halide present, direct catalytic oxidation of cyclohexene to adipic acid with hydrogen peroxide catalysed by Na2WO4.2H2O and acidic ionic liquids has been performed with excellent yields and selectivities, and the catalyst system could be easily reused.

Clean synthesis of adipic acid by direct oxidation of cyclohexene with H2O2 over peroxytungstate–organic complex catalysts

Directly catalytic oxidation of cyclohexene to adipic acid with hydrogen peroxide over environmentally benign peroxytungstate–organic complex catalysts is performed with excellent yields and selectivities, without any organic solvent and harmful phase-transer catalyst.