III International Conference

PP-II-52LIQUID PHASE OXIDATION OF CYCLOHEXANE IN THE PRESENCEOF Au/SILICALITE CATALYSTSKhramov M., Pirutko L. 1 , Chernyavsky V. 1 , Ivanov A. 1 , Abornev S. 1 , Uriarte A.,Kharitonov A. 1Solutia Inc., Pensacola, USA1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: khar@catalysis.ruA study of Au catalysts in cyclohexane oxidation by dioxygen showed that Au catalystconverts cyclohexyl hydroperoxide (CHHP), which forms in the reaction, to ketone andalcohol with selectivity close to 100 %, and has no significant effect on the rate ofcyclohexane oxidation. An increased gold content in the samples increases the activity inCHHP decomposition and decreases the selectivity for side products formation.Liquid-phase oxidation of cyclohexane is the most difficult step in the polyamideproduction. Cyclohexanol and cyclohexanone are the target products, and CHHP is the mainintermediate. Without catalyst, up to 30% of the initial cyclohexane is converted to sideproducts. Such a low selectivity is caused mainly by the free radical mechanism of CHHPdecomposition.Attempts to use heterogeneous catalysts for the liquid-phase oxidation of cyclohexanehave not produced a commercially feasible process [1]. In recent years, research efforts in thisfield were focused on gold catalysts [2]. Of particular interest are results of the work [3], inwhich cyclohexane was oxidized on Au/NaY catalysts. However, the lack of blank runs(without catalyst) and the chromatographic measurement of CHHP concentration cast somedoubt on the reliability of these results.Our study was aimed at elucidating the role of Au/silicalite catalysts in the liquid-phaseoxidation of cyclohexane. The catalysts were prepared by the Deposition–Precipitationmethod. Gold content in the samples was varied from 0 to 3.9 wt.%. Cyclohexane wasoxidized in a passivated Parr reactor at temperature 170 °C and pressure 900 kPa; air waspassed at a constant rate through cyclohexane containing 0.5 wt % catalyst, the reactorcontents were periodically sampled.Figure 1 shows the results of a blank run and runs in the presence of catalysts. One maysee that the rates of cyclohexane oxidation with and without catalyst are very similar. In thepresence of the catalyst the CHHP concentration is significantly lower and what is even moreimportant the selectivity of cyclohexane conversion to side products decreases at conversions258