Processing Study on the Stability of Heteropoly Acid Catalyst in the Oxidation of Methacrolein to Methacrylic Acid

Abstract

The oxidation of methacrolein to methacrylic acid over a heteropoly acid catalyst was studied in a pilot scale unit with tubular multisampling reactor. The catalyst performance was monitored at different aging phases during a total runtime of 195 days. Deactivation was accompanied by a loss of catalyst mass through evaporation of molybdenum oxide. With time on stream, deactivation expands from an area close to the inlet of the catalyst bed downstream to the outlet. Several causes for the deactivation were evaluated in processing experiments. Possible detrimental effects of acetic acid and carbon monoxide were excluded by cofeeding these byproducts in high concentrations. A critical parameter is the oxygen concentration because reoxidation of the catalysts is rate limiting. Low oxygen supply results in a depletion of lattice oxygen accompanied by a marked activity loss. It is suggested that continued preservation of the catalyst in the reduced state promotes structural disintegration.

Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40 supported on amine-functionalized MCM-41

“…Therefore, they are widely used in many oxidation reactions (such as selective oxidation methacrolein (MAL) to methacrylic acid (MAA), conversion of sugar to sugar acid, etc.). [26][27][28][29][30][31][32][33] However, the direct use of POMs for hydroxylation of benzene to phenol is adverse to the catalyst recovery and reuse since it is difficult to separate POMs from reaction media. An effective strategy is to immobilize POMs onto high surface area carriers (such as activated carbon, silica, MCM-41, titania, resin, etc.).…”

Effect of Cesium and Phosphate Addition to Mo/V/W Mixed Oxide Catalysts for the Gas Phase Oxidation of Methacrolein to Methacrylic Acid

“…This is likely caused by its lower selectivity towards CO x and respectively a lower oxygen consumption, fueling the reaction with oxygen and increasing the conversion at higher residence times. Even though catalyst A modified with Cs and P contains about 95 wt.% HPA, it still falls far behind the reported MAA selectivity (≈85%) of industrial HPA catalysts at respective conversions [11]. This can be explained by significant amounts of tungsten in the formed HPA phase, which lowers the selectivity towards MAA [17,19].…”

“…In a closer investigation, Schunk et al achieved promising results with S MAA,MAC of about 70% at a conversion of 64%, after adding Cs and P to M1 mixed oxides under Cs/P and (Mo + V + W)/P variation [8]. Despite all progress made in improving the MAA selectivity of Mo/V/W oxides it is still significantly lower than for industrial HPAs [10,11]. Since the published data concerning the addition of Cs and P is limited, there are still unresolved questions of great interest.…”

Preparation, Characterization and Ion-Exchange Properties of an Organic-Inorganic Composite Cation Exchanger: Polyaniline-Bi(III) Iodovanadate and Catalytic Properties of Bi(III) Iodovanadate Inorganic Ion Exchanger

“…The hetropolyacid (iodovanadate) unit of inorganic ion exchanger like Bi(III) iodovanadate is made up of oxygen and hydrogen with some metals and nonmetal (iodine and vanadium). Bi(III) iodovanadate can act as a oxidizing agent, to the polymerization of aniline monomer into green colored polyaniline gels without adding oxidizing agent [10,[21][22][23][24].…”