Liquid-phase oxidation of cyclohexane. Cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone, mechanisms of formation and transformation

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Oxidative Conversion of Polyethylene Towards Di-Carboxylic Acids: A Multi-Analytical Approach

To reduce the pressure on the environment created by the increasing amount of plastic waste, the need to develop suitable plastic recycling methods has become more evident. However, the chemical recycling toolbox for polyethylene (PE), the most abundant type of plastic waste, remains underdeveloped. In this work, analytical methods were developed to explore the possibility to oxidatively convert PE into di-carboxylic acids as reaction products. A multi-analytical approach including gas chromatography-mass spectrometry, gas chromatography-flame ionization detection, several (2D) nuclear magnetic resonance methods as well as in-situ transmission infrared spectroscopy was used. This led to a thorough qualitative and quantitative analysis on the product mixture, which extends and clarifies the existing literature. Without a catalyst (thermally) already up to 7 mol % di-carboxylic acids can be formed. Furthermore, it was found that the majority of the oxidized functionalities are carboxylic acids, (methyl) ketones, γ-lactones, γ-ketones and esters. An intra-molecular hydrogen shift seemed key in the cleavage step and the formation of late-stage side products. In addition, crosslinking reactions due to esterification reactions seem to limit the di-carboxylic acid yield. Therefore, these two handles can be taken into account to study and design similar (catalytic) systems for the oxidative conversion of plastic waste.

Controllable oxidation of cyclohexanone to produce sodium adipate in an electrochemical reactor with a Pt NPs/Ti membrane electrode

An electrocatalytic membrane reactor (ECMR) with an anode consisting of Pt nanoparticles (NPs) loaded on a Ti membrane electrode (Pt NPs/Ti) was designed to oxidize cyclohexanone (K) to produce sodium adipate (SA) under mild conditions. The effects of residence time, reaction temperature, current density and initial K concentration on K conversion were investigated. Optimization experiments were conducted to determine the effects of and interactions between different operating parameters on K conversion using a central composite design within the response surface methodology. A 88.3% conversion of K and 99% selectivity to SA were obtained by the ECMR under the optimum conditions of reaction temperature = 30.8 °C, K concentration = 22.54 mmol L−1, residence time = 25 min and current density = 2.07 mA cm−2. The high performance of the ECMR is attributed to electrocatalytic oxidation (at the Pt NPs/Ti electrode), convection-enhanced mass transfer, and the timely removal of the desired products.

Light-Driven Waste-To-Value Upcycling: Bio-Based Polyols and Polyurethanes from the Photo-Oxygenation of Cardanols

The upcycling of waste biomass into valuable materials by resource-efficient chemical transformations is a prime objective for sustainable chemistry. This approach is demonstrated in a straightforward light-driven synthesis of polyols and polyurethane foams from the multi-ton waste products of cashew nut processing. The photo-oxygenation of cardanol from nutshell oil results in the formation of synthetically versatile hydroperoxides. The choice of the workup method (i. e., reduction, hydrogenation, epoxidation) enables access to a diverse range of alcohols with tunable alkene and OH functions. Condensation with isocyanates to give rigid polyurethane foams provides a resource-efficient waste-to-value chain that benefits from the availability of cardanol and installation of OH groups from aerial O2 .

Recent Progress in Adipic Acid Synthesis Over Heterogeneous Catalysts

Adipic acid is one of the most important feedstocks for producing resins, nylons, lubricants, plasticizers. Current industrial petrochemical process, producing adipic acid from KA oil, catalyzed by nitric acid, has a serious pollution to the environment, due to the formation of waste nitrous oxide. Hence, developing cleaner methods to produce adipic acid has attracted much attention of both industry and academia. This mini-review article discussed advances on adipic acid synthesis from bio-renewable feedstocks, as well as most recent progress on cleaner technology from fossil fuels over novel catalytic materials. This work on recent advances in green adipic acid production will provide insights and guidance to further study of various other industrial processes for producing nylon precursors.