Taking advantage of a priori unwanted catalysts modifications

• Several typical catalysts changes often occurring during catalytic processes are surveyed.
• Textural change, decomposition, volatilization, sulphation, etc. of active phases are addressed.
• Modifications of the catalysts may become beneficial when induced in suitable conditions.
• Taming a priori unwanted changes may lead to improve the performance.
• Partial and total oxidations on Mo, Re and Mn based catalysts are evoked.

A catalyst experiences numerous physico-chemical changes during its life. Often these changes are a priori regarded as ‘unwanted’ in terms of catalytic performance. However, understanding the details of these transformations offers the opportunity to control them. By distinguishing which changes do contribute to deteriorate the catalytic performance, vs. those that bring improved catalytic behaviours, it becomes possible to channel the system towards specific modifications. Along this strategy, a priori unwanted modifications of the catalysts become beneficial when induced and exploited in suitable conditions. This paper revisits examples wherein such an approach was payful: (i) MoO3 + α-Sb2O4 mixtures and (ii) ReSbO compounds, explored in the oxidation of isobutene to methacrolein, (iii) γ-MnO2 explored in the total oxidation of methanethiol, and (iv) (NH4)6P2Mo18O62 polyoxometalate explored in the oxidative dehydrogenation of 2-butanol to methyl-ethyl-ketone.

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