Fabrication of tungstate metal foams as efficient catalysts for dimethyl sulfoxide oxidation in a microreactor

To overcome the problems of traditional catalyst in the microreaction technology, a microreactor system with tungstate metal foam catalyst was constructed and the catalytic efficiency were investigated by dimethyl sulfoxide (DMSO) oxidation reaction as a probe reaction. Three tungstate metal (CuWO₄, NiWO₄, FeWO₄) foams were fabricated, and inherited the porous structure from the metal foam and had a high loading density of tungstate metal crystal particles. In the lab-built flat-plate microreactor, the effects of reaction temperature, residence time, molar ratio and pH on the yield of dimethyl sulfone (MSM) were investigated, and the tungstate metal foams showed prefect catalytic activity. Compared with NiWO₄ foam and FeWO₄ foam, the larger specific surface area and higher porosity endow CuWO₄ with a better catalytic performance. When the reaction temperature was 80 °C, the residence time was 40 min, the molar ratio was 1:1 and the pH value of the reaction system was 3, the yield of MSM reached 82.1%. Furthermore, the NiWO₄ foam catalyst system showed a better performance compared with other two catalyst system. This work indicates the potential opportunity of the construction of various metal foam catalysts in the versatile continuous microreaction technology.