Covalantly bonded Schiff base cobalt complex catalyst for the selective oxidation of linear alkanes using molecular oxygen

Abstract

Graphic A Schiff base [1,2-bis(salicylidene amino)-phenylene] cobalt complex catalyst bonded on carbamate modified silica gel has been prepared for one step liquid-phase oxidation of alkanes with molecular oxygen. At moderate temperatures (150 °C) and low oxygen pressure (16 atm), the oxidation of n -hexane and n -heptane were studied. In the case of n -hexane, it was found that isomerization, dehydrocyclization as well as oxidation products both were formed, while for n -heptane, there was no cracking or reforming reaction and the oxidation products are principally 4-heptanone, 2-heptanone, 2-heptanol and heptanoic acid. For n -hexane, if the reaction is carried out in nitrogen atmosphere, only isomerization and dehydrocyclization products are formed in high yield (∼74.0%) with no 2,2-dimethyl butane (2,2-DMB) and 2,3-dimethyl butane (2,3-DMB). It is thus seen that the catalyst reported in this work can also be used for reforming of n -hexane and requires much lower temperature. The thermogravimetric analysis (TGA) analysis shows that it is stable up to 211 °C and the atomic absorption spectroscopy (AAS) shows a negligible loss of metal in 50 h use of the catalyst upto 180 °C reaction temperature.