Redox solid catalysts for the selective oxidation of cyclohexane in air

The selective oxidation of cyclohexane to cyclohexanol, cyclohexanone and adipic acid using molecular oxygen as the oxidant and at moderate temperatures (403 K) has been investigated over four different cobalt-containing aluminophosphate (AlPO) molecular sieves. There is a correlation between catalytic activity and the fraction of (framework) Co(II) ions that is first oxidised to Co(III) in air. CoAlPO-36 (pore aperture 6.5 x 7.5 Angstrom) exhibits significant activity for the oxidation of cyclohexane in contrast to CoAlPO-18, which, although it has the highest fraction of oxidisable cobalt, does not show any activity chiefly because of its smaller pores.