Method for oxidizing saturated cyclic hydrocarbons by oxygen
The present invention relates to a continuous method for oxidizing saturated cyclic hydrocarbons by oxygen to obtain a mixture of hydroperoxides, alcohols and ketones. It relates more particularly to a method for oxidizing cyclohexane in a column forming a bubble reactor, for the formation of cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone. According to the invention, the column may be supplied with oxygen-enriched air, while meeting the maximum oxygen concentration requirements in the headspace of the reactor to avoid any risk of explosion.
1. A continuous method for oxidizing a saturated cyclic hydrocarbon by oxygen to a mixture of hydroperoxide, alcohol and ketone, comprising the steps of:
introducing a liquid stream of the hydrocarbon to be oxidized and a gas stream containing oxygen in cocurrent flow at the bottom of a column,
supplying a gas stream containing oxygen to various stages of the column, wherein the quantities of oxygen supplied to each stage of the column decrease along the flow direction of the liquid phase in the column,
forming a degasified liquid phase at the top of the column by forming an overhead gas at the top of the column,
supplying a stream of non-oxidizing gas to the overhead gas and/or in the liquid phase in the degasification zone or immediately upstream thereof, at a sufficient flow rate to maintain the oxygen concentration of the overhead gas at a volumetric concentration not exceeding the upper oxygen concentration limit wherein the overhead gas is present in an unexplosive state, and
withdrawing the degasified liquid phase.
2. The method according to claim 1 , wherein the non-oxidizing gas is nitrogen, an inert gas, or oxygen-depleted air.
3. The method according to claim 1 , wherein the saturated hydrocarbon is cyclohexane, decaline, or cyclododecane.
4. The method according to claim 3 , wherein the upper oxygen concentration limit is 8.5% if the hydrocarbon is cyclohexane.
5. The method according to claim 1 , wherein the column further comprises perforated trays.
6. The method according to claim 1 , wherein the gas containing oxygen is oxygen, oxygen-enriched air or oxygen-depleted air.
7. The method according to claim 1 , wherein the step of forming a degasified liquid phase further comprises degassing the liquid phase by placing a degasser in the column wherein the degasser is a vessel immersed in the liquid phase just below the upper level of the liquid phase.