Study on the Development of High-Performance P-Mo-V Catalyst and the Influence of Aldehyde Impurities on Catalytic Performance in Selective Oxidation of Methacrolein to Methacrylic Acid

Baohe Wang,Honggang Dong,Hongxia Liu,Jing Zhu,Zhaobang Zhang,Liang Lu

doi:10.3390/catal11030394

Abstract

A series of KxH1.1-xCu0.2Cs1(NH4)1.5PVMo11O40 (KxCuCsNH4PVA) catalysts with different x values were synthesized to catalyze the selective oxidation of methacrolein (MAL) to methacrylic acid (MAA). The effects of potassium (K) ions on both the structure and catalytic activity were studied in detail. The optimum K0.6CuCsNH4PVA exhibited a large surface area, more acid sites, and abundant active species (V4+/VO2+) in the secondary structure of the Keggin structure, consequently offering good catalytic performance. Furthermore, K ions increased the MAA selectivity at the expense of carbon monoxide and carbon dioxide (together defined as COX). Additionally, several process parameters for MAL oxidation were evaluated in the processing experiments. The effects of aldehyde impurities (formaldehyde and propanal) on the catalytic performance were investigated. Possible detrimental effects (catalyst poisoning and structural damage) of aldehyde impurities were excluded. A light decrease in MAL conversion could be attributed to the competitive adsorption of aldehyde impurities and MAL on the catalyst. Hopefully, this work contributes to the design of stable and feasible catalysts for the industrial production of MAA.

Highlights

Methacrylic acid (MAA) is a chemical monomer used for the synthesis of methyl methacrylate (MMA)
A typical route of the C2 process is as follows: the hydroformylation of ethylene to propionaldehyde is the first step, condensation follows with formaldehyde to form methacrolein (MAL), which is oxidized by oxygen (O2) to MAA [1,2,3]
Selective oxidation of MAL to MAA is an important intermediate step in the synthesis of MMA Keggin-type P-Mo-V based on heteropoly acids (HPAs) and their salts are suitable for the selective oxidation of MAL to MAA [4,5,6,7,8,9]

Summary

Introduction

Methacrylic acid (MAA) is a chemical monomer used for the synthesis of methyl methacrylate (MMA). Selective oxidation of MAL to MAA is an important intermediate step in the synthesis of MMA Keggin-type P-Mo-V based on heteropoly acids (HPAs) and their salts are suitable for the selective oxidation of MAL to MAA [4,5,6,7,8,9]. Their poor thermal stability and low surface area led to low catalytic activity and high costs of the catalysts. The decomposition of the Keggin structure and irreversible deactivation significantly reduces the lifetime of HPAs catalysts [10,11,12]

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Discussion

Conclusion