Efficient oxidation of cycloalkanes with simultaneously increased conversion and selectivity using O2 catalyzed by metalloporphyrins and boosted by Zn(AcO)2: A practical strategy to inhibit the formation of aliphatic diacids

The conversion and selectivity in oxidation of cycloalkanes to cycloalkanols and cycloalkanones with O2 catalyzed by metalloporphyrins were increased simultaneously through adjusting the transformation of oxidation intermediates to cycloalkanols by Zn(II), delaying the emergence of cycloalkanones and inhibiting the formation of by-products aliphatic diacids. The conversion of cyclohexane reached up to 6.53 % with the selectivity of 96.9 %. [Display omitted] •Direct source of acids in cycloalkane oxidation was confirmed as cycloalkanone.•Delayed formation of cycloalkanone favored the inhibition of aliphatic diacids.•Enhanced formation of cycloalkanol favored the inhibition of aliphatic diacids.•Conversion and selectivity were increased simultaneously in cycloalkane oxidation.•A strategy to boost alkane oxidation was gained by adjusting peroxide conversion. The direct sources of aliphatic acids in cycloalkanes oxidation were investigated, and a strategy to suppress the formation of aliphatic acids was adopted through enhancing the catalytic transformation of oxidation intermediates cycloalkyl hydroperoxides to cycloalkanols by Zn(II) and delaying the emergence of cycloalkanones. Benefitted from the delayed formation of cycloalkanones and suppressed non-selective thermal decomposition of cycloalkyl hydroperoxides, the conversion of cycloalkanes and selectivity towards cycloalkanols and cycloalkanones were increased simultaneously with satisfying tolerance to both of metalloporphyrins and substrates. For cyclohexane, the selectivity towards KA-oil was increased from 80.1% to 96.9% meanwhile the conversion was increased from 3.83 % to 6.53 %, a very competitive conversion level with higher selectivity compared with current industrial process. This protocol is not only a valuable strategy to overcome the problems of low conversion and low selectivity lying in front of current cyclohexane oxidation in industry, but also an important reference to other alkanes oxidation.