The synthesis of Co-doped SAPO-5 molecular sieve and its performance in the oxidation of cyclohexane with molecular oxygen

Ionothermal Crystallization of SAPO-11 Using Novel Pyridinium Ionic Liquid and Its Catalytic Activity in Esterification of Levulinic Acid into Ethyl Levulinate

A study using a novel pyridinium ionic liquid, namely 1-propylpyridinium bromide ([PPy]Br), to crystallize SAPO-11 under ionothermal conditions is reported. By carefully following the crystallization process, SAPO-11 can readily be crystallized in the presence of [PPy]Br, which serves as a synthesis solvent and structure-directing agent, at 150 °C after 133 h of heating. The study also focuses on manipulating other synthesis parameters (e.g., crystallization temperature, phosphorous content, silicon amount and [PPy]Br concentration) and investigating their respective effects on the formation of SAPO-11. The crystallized SAPO-11 has an acidic nature and a high surface area. Under conductive instant heating conditions, the SAPO-11 catalyst is very active in the conversion of levulinic acid into ethyl levulinate; 93.4% conversion and 100% selectivity of ethyl levulinate are recorded at 180 °C after 30 min of reaction. This result is comparable to or even better than those of conventional homogeneous catalysts.

A comprehensive and updated review of studies on the oxidation of cyclohexane to produce ketone-alcohol (KA) oil

Oxidation of cyclohexane is an essential chemical reaction for the industrial manufacture of cyclohexanol and cyclohexanone. These two compounds, together known as ketone–alcohol (KA) oil, are the main feedstock for nylon 6 and nylon 6,6 productions. Several types of catalysts and reaction conditions have been used for cyclohexane oxidation. This paper presents a thorough literature review of catalytic materials used for cyclohexane oxidation to produce KA oil using oxygen, air and other oxidizing agents as well as utilizing different solvents. This review covers research and development reported over the years 2014–2020. This review aims to comprehend the type of catalysts, solvents, oxidants and other reaction parameters used for the oxidation of cyclohexane. Three types of cyclohexane oxidation processes namely thermocatalytic, photocatalytic and microwave-assisted catalytic have been reported. The results of the review showed that metal and metal oxide loaded silica catalysts performed excellently and provided high selectivity of KA oil and cyclohexane conversion. The use of peroxides is not feasible due to their high price compared to air and oxygen. Gold nanoparticles supported on silica performed with high selectivity and good conversion. The use of hydrochloric acid as an additive was found very effective to enhance the photocatalytic oxidation of cyclohexane. Water on the catalyst surface enhanced the reactivity of the photocatalysts since it helps in the generation of hydroxyl radicals.

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.

Interfacial CoOx Layers on TiO2 as an Efficient Catalyst for Solvent-Free Aerobic Oxidation of Hydrocarbons

Construction of efficient interfaces to improve the performance of supported metal catalysts is a challenging but effective technique. A newly synthesized catalyst with layered cobalt oxide on the surface of titania (layer-CoO_x /TiO₂ ) is highly selective towards the aerobic oxidation of C-H bonds in a series of hydrocarbons under sustainable conditions. The layer-CoO_x /TiO₂ easily outperforms the state-of-the-art noble metal catalysts and homogeneous cobalt salts used in industry. In-depth structural and functional characterization reveal that the layer-CoO_x /TiO₂ readily reacts with O₂ for the adsorption and activation of C-H bonds. The layered structure of CoO_x can maximize the interfacial effect of CoO_x /TiO₂ leading to a good performance for the oxidation of C-H bonds.