Selective Methacrolein Oxidation Catalyzed with Heteropoly Compounds: Effect of the Oxidation State Modulated with Hydrogen Pretreatment

Abstract

The chemical state of catalysts is a vital factor affecting their catalytic performance. Herein, a method for controllable modification of the chemical state was proposed for the heteropoly catalyst in the methacrolein oxidation reaction to methacrylic acid by means of hydrogen pretreatment. The inherent relationship between the chemical state and the catalytic performance of the Keggin catalyst was systematically investigated. The changes in structure and element valence induced by hydrogen pretreatment were characterized with various methods, including XRD, FTIR, UV, Raman, SEM, O2-TPD, XPS, and ESR spectra. The pretreatment conditions were optimized on a fixed-bed tubular reactor, and the favored chemical state of the catalyst was obtained. This report provides an effective approach to activating the Keggin catalyst for oxidation reactions.

DFT Insights into the Effect of Metal Substitution on the Catalytic Activity of Molybdenum-Based Heteropoly Acid in the Oxidation of Methacrolein to Methacrylic Acid

“…The selective oxidation of MAL to MAA on heteropoly acid compounds described as Scheme shows a high atomic efficiency for the preparation of MAA, and the catalyst is environmentally friendly and easy to recover. , The application of efficient heteropoly acid catalysts is crucial for the economic efficiency of the entire process . Therefore, it has attracted the interest of many researchers. − …”

Continuous Synthesis of Methacrolein over Sulfonic Acid Resin Catalysts: Unraveling the Effect of Acid Strength and Solvent Permittivity

“…For example, the core raw materials polymethacrylimide (PMI) for rocket fairings are typically obtained through methacrylonitrile and methacrylic acid, , which are produced by cyanation and oxidation of MAL, respectively (Scheme ). Methyl acrylate (MMA), which is synthesized by oxidation , and esterification , or a one-step process , utilizing MAL as raw material, is widely used in the synthesis of plexiglass for the decoration industry. In the construction industry, the reduction product methyl alcohol from MAL is gaining popularity in producing a new generation of water-reducing reagents. , As a result, MAL production significantly impacts downstream chemicals and industrial chains.…”

“…The industrial approach for MAL production is mainly focused on the C 4 -selective oxidation route in the past decades, utilizing isobutane 11−13 and isobutene 14−16 as raw materials over mixed metal oxides or heteropoly acid catalysts (Scheme 2), while the improvement of conversion and selectivity are still intractable problems. Although considerable efforts have been made to improve the oxidation process efficiency, the difficulties in C(sp 3 )−H bond activation and complicated side products continue to puzzle researchers. Meanwhile, the relatively high reaction temperature may raise safety risks during industrial scale-up.…”