Promoting effect of Mg in supported Mo/HBeta–Al2O3 catalyst for cross-metathesis of ethene and butene-2 to propene

Promoting effects of Mg in heterogeneous Mo/HBeta–Al2O3 catalyst have been carefully studied for cross-metathesis of ethene and butene-2 to propene. The catalyst shows good stability with Mg content in the range of 1–2 wt%. Such effect may be attributed to the elimination of weak acid sites through introduction of Mg which suppresses the side olefin oligomerization reaction, as evidenced from NH3-TPD and 1H MAS NMR results. Addition of more Mg content to 3 wt% may change the state and reducibility of Mo species, as indicated from the UV–vis, UV-Raman and H2-TPR measurements. The increasing difficulty for the reduction of Mo(VI) species is closely related with the poor performance of 3 wt% Mg–4Mo/HBeta–30% Al2O3 catalyst in the metathesis reaction.

Graphical abstractAddition of Mg to Mo/HBeta–Al2O3 olefin metathesis catalysts may change the acidity and surrounding symmetry of Mo species. Better catalyst stability could be obtained with the Mg content in the range of 1–2 wt% owing to the elimination of weak acid sites. High Mg loading increases the reducibility difficulty of Mo species which leads to poor performances of the catalyst in the metathesis reaction of ethene and butene-2 to propene.Figure optionsDownload full-size imageDownload as PowerPoint slide