The gas phase disproportionation reaction of propene on
supported organometallic catalysts is described in detail.
The catalysts studied during the research were based mainly
on molybdenum and tungsten, and were supported on a variety
of oxides. A static vacuum system was employed in the
catalysis and the reproducibility of catalyst activities was
guaranteed to a large extent by the development of an "in
situ" preparation technique.
The molybdenum hexacarbonyl catalyst was studied in
close detail using a series of supports and the effect of
varying the pretreatment of support indicated a maximum in
activity attributable to the appearance of certain surface
hydroxyl groups. Study of the activation temperature of
these supported catalysts suggested that the active species . contained no carbonyl groups and that the molybdenum had
undergone oxidation from Mo(0) to a higher oxidation state
during the process of activation. Infrared and e.s.r.
spectroscopic techniques were used to support the findings
of the kinetic experiments.
The activities of a series of molybdenum and tungsten
non -carbonyl complexes supported on alumina and silica were
measured using the same mode of catalyst preparation. The
considerable activity of such catalysts was a consequence
of the rapid decomposition of the complex on the support.and
formation of the active species by oxidation. In the case
of the hexamethyltungsten catalyst it is thought that the
active catalytic species is generated by a reduction process.