Direct oxidation of cyclohexane to adipic acid using nano-gold catalysts

Adipic acid (AA) is one of the most important commercially available aliphatic dicarboxylic acids, which has a large industrial application in the manufacture of Nylon-6 and Nylon-66. The present work demonstrated a green chemistry route for the direct oxidation of cyclohexane (CH) to AA using supported nano-gold catalyst in one-step reaction. The catalysts were prepared in two steps and were then characterized by different methods such as ICP, BET surface area, XRD, SEM, TEM, etc. Catalytic tests were carried out using Parr autoclave in the temperature range of 100–170 °C, and the products were analyzed by gas chromatograph. Among all investigated catalysts, TiO2 supported nano-gold exhibited the superior activity compared to all other tested catalysts. The conversion of CH and the selectivity of AA obtained over TiO2 supported catalyst were 16.4 % and ca. 21.6 %, respectively, without a noticeable change in the catalyst stability. In summary, it is possible to produce AA with ca. 8 % yield using nano-gold supported on TiO2.