Investigations into the C4 olefin metathesis over Mo/Al2O3: Effects of support nature and pretreatment conditions on the product distribution

A series of Mo/Al 2 O 3 catalysts were prepared and evaluated in the consecutive metathesis of 1-butene and isobutene. The correlations between the states of Mo species and Metathesis I (2-C 4 = + 1-C 4 = → C 3 = + 2-C 5 = ), Metathesis II (2-C 4 = + i -C 4 = → C 3 = + i -C 5 = ) were discussed in detail. It was found that Metathesis I and Metathesis II followed different deactivation rate due to the differences in active sites. Metathesis I was more acidity-sensitive and it was suppressed when alumina was calcined at high temperature due to the decrease of acid sites. Metathesis II kept relative good catalytic stability and high calcination temperature was beneficial to increase the ratio of isopentene in pentene fraction. As revealed by the XPS and reductive pretreatment results, different C 4 olefin molecules on the same Mo-based catalyst exhibited different metathesis activity and partially reduced Mo V (or Mo IV ) species from octahedrally coordinated Mo(O) species contributed to the selective promotion of Metathesis II.