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

Catalysts

卷:11

Bettina Kraushaar-Czarnetzki¹  Maximilian Sennerich¹  Stefan Heißler²  Peter G. Weidler² 

[1] Institute of Chemical Process Engineering CVT, Karlsruhe Institute of Technology, Campus South, 76131 Karlsruhe, Germany;

[2] Institute of Functional Interfaces, Karlsruhe Institute of Technology, Campus North, 76344 Eggenstein-Leopoldshafen, Germany;

关键词: partial oxidation;    molybdenum-based mixed oxide;    methacrolein;    methacrylic acid;    cesium promoter;    phosphorous promoter;   

DOI  :  10.3390/catal11020231

来源: DOAJ

【 摘 要 】

The present study investigates modified Mo/V/W mixed oxides as a possible alternative for state of the art heteropoly acid catalysts (HPA) in the partial oxidation of methacrolein (MAC) to methacrylic acid (MAA). Even though HPAs show an excellent activity and MAA selectivity, their long-term stability is unsatisfying, rendering the catalyst inoperable after runtimes of roughly 6 months. Mo/V/W mixed oxides consisting of M1 and a hexagonal (Mo,V,W)O_x-phase (h-phase) in varying proportions were modified by impregnation with aqueous solutions containing cesium and phosphate ions. All samples were characterized with respect to specific surface area, crystallinity, elemental and phase composition. The catalytic performance in the oxidation of MAC to MAA was investigated using a continuously operated reaction unit with tubular fixed bed reactor. Impregnation with cesium and phosphate ions and subsequent heating triggers the transformation of the mixed oxide into a Keggin-type HPA, whereby the h-phase is more reactive than M1. The transformation into HPA is accompanied by a change in the catalytic properties, i.e., the selectivity to MAA is considerably improved. Compared to HPA synthesized directly, however, the HPA samples obtained by transformation of mixed oxides exhibit no advantages, be it with respect to activity, MAA selectivity or stability.

【 授权许可】

Unknown