Process for oxidation of cyclohexane
Process for oxidizing cyclohexane in which oxygen is contacted with cyclohexane at a pre-selected feed rate in a first reaction zone and unconsumed oxygen is contacted with cyclohexane in a second reaction zone in which the cyclohexane feed rate is lower than the pre-selected feed rate.
1. A cyclohexane oxidation process that comprises
(a) introducing into a reaction zone, a first stream of liquid cyclohexane at a first flow rate and an oxygen-containing gas, thereby contacting said first stream of cyclohexane and said oxygen containing gas, optionally in the presence of a cyclohexane oxidation catalyst, to produce a primary liquid reaction product that comprises cyclohexyl hydroperoxide (CHHP), cyclohexanone (K) and cyclohexanol (A),
(b) withdrawing from said primary reaction zone said liquid reaction product,
(c) withdrawing from said primary reaction zone a primary reaction zone gas that comprises unreacted gaseous cyclohexane and 0.5 to 6.0 vol % oxygen,
(d) introducing into a clean-up reaction zone the primary reaction zone gas and a second stream of liquid cyclohexane at a second flow rate that is lower than said first flow rate of the first stream of cyclohexane, thereby containing the primary reaction gas with the second stream of liquid cyclohexane to produce a clean-up reaction product that comprises CHHP, K and A, and
(e) withdrawing from said clean-up reaction zone a clean-up reaction zone gas that comprises oxygen in a concentration that is lower than the oxygen concentration in the primary reaction zone gas.
2. The process of claim 1 wherein the clean-up reaction zone gas comprises oxygen at a concentration below 2.0 vol %.
3. The process of claim 1 wherein the clean-up reaction zone comprises two or more reaction vessels in series.
4. The process of claim 1 , wherein the clean-up reaction zone comprises two or more reaction vessels in parallel.
5. The process of claim 1 , wherein the primary reaction zone and the clean-up reaction zone comprise compartments of a single column wherein the primary reaction zone is separated from the clean-up reaction zone by a tray comprising a series of holes, the tray adapted, to prevent liquid from flowing down through the tray and to allow gas to flow up through the series of holes.
6. The process of claim 5 , wherein liquid from the clean-up reaction zone is transferred to the primary reaction zone via a pipe external to the column.
7. The process of claim 5 , wherein liquid from the clean-up reaction zone is transferred to the primary reaction zone via an internal down-corner in the column.
8. The process of claim 1 , wherein the temperature of the clean-up reaction zone is in the range of 130° C. to 200° C.
9. The process of claim 1 , wherein the temperature of the primary reaction zone is in the range of 130° to 200° C.
10. The process of claim 1 , wherein the mass flow rate in the primary reaction zone is higher than the mass flow rate in the clean-up reaction zone.
11. The process of claim 1 , wherein the first stream of cyclohexane and the oxygen containing gas are contacted in the presence of a cyclohexane oxidation catalyst.
12. The process of claim 11 , wherein the cyclohexane oxidation catalyst comprises soluble salts of at least one metal selected from the group consisting of cobalt and chromium.