CA1099747A - Process for the preparation of polyalkylbenzene hydroperoxides - Google Patents

Abstract

Abstract of the Disclosure Polyalkylbenzene hydroperoxides are prepared from a homogeneous solu-tion at increased rates in the presence of sulfolane from polyalkylbenzenes which are poorly soluble or insoluble in sulfolane by preoxidizing the polyalkylbenzene to an oxidation level of at least 10 percent and less than 55 percent.
Then the sulfolane is added and a homogeneous solution is formed and oxidation is continued to produce a hydroperoxide product at increased rates and to ex-cellent conversions.

Description

~ 95~747 :.

l ~.,' Background of the Invention ~ ~
This invention relates to a process for preparing hydroperoxides from : ~-polyalkylbenzenes in the presence of sulfolane.
The use of sulfolane to increase the rate of formation of hydroperox- ;~
ides from alkyl- and polyalkylbenzenes is disclosed in U.S. Patent No. 3,524,888This patent also discloses that when an alkylbenzene like toluene, ethylbenzene,cumene or a polyalkylbenzene like ortho-xylene, 1,3,5-trimethylbenzene or 4-isopropyl-o-xylene are oxidized in the presence of sulfolane a homogeneous solution is formed. The homogeneous solution enables better contact of the re- -;
actants and aids in the reaction and permits ready separation of the hydroper-oxide products. When 5-isopropyl-m-xylene (3~5-dimethylcumene) was oxidized in the presence of sulfolane there was no apparent increase in the rate of forma-tion of hydroperoxides. The lack of such an increase occurred because of the immiscibility of 5-isopropyl-m-xylene in sulfolane preventing the formation of a homogeneous reaction mixture.
It is well known to produce resorcinol or hydroquinone from meta-di-~sopropylbenzene or para-diisopropylbenzene, respectively, by oxidation ~o pro-duce the dihydroperoxide which by cleavage with strong acid catalysts is con-verted to resorcinol or hydroqllinone and acetone. The oxidation of both alkyl .~

lU99~4~

f groups of the meta-, or para-diisopropylbenzene (DIPB) is readjly inhibited and only par~ial oxidation can be achieved without considerable loss of efficiency and rate of oxidation. DIPB is oxidized first to the mono-hydroperoxide which is then further oxidized to the dihydroperoxide. In actual practice the re-action is stopped at a high mono-/dihydroperoxide ratio to reduce the formation of the numerous undesirable by-products otherwise formed in the oxidation of DIPB, such as carbinols, ketones, and carbinol-hydroperoxides which interfere with the oxidation. Increasing the temperature will increase the rate of re-action but it will also increase the formation of by products. Therefore, a balanced operation requires relatively moderate temperatures of around 80-90 C.
Even at these conditions with a low rate of reaction the reaction eventually stops due to the inhibition of the oxidation by-products9 and the ratio of DIPB-mono-/-dihydroperoxide is high.
It would be most desirable to increase the rate of reaction to hydro peroxides and to increase the conversion to DIPB-dihydroperoxide by oxidizing .-,.
the DIPB in the presence of sulfolane. Unfortunately, the ~IPB, as well as S-isopropyl-m-xylene, and other polyalkylbenzenes, which have at least one alkyl group having three or more carbon atoms where one carbon atom is a terti-ary carbon atom, including compounds such as 1,3,5-triisopropylbenzene, is immiscible with sulfolane. This immiscibility prevents the formation of a homogeneous reaction mixture and, therefore, also prevents the benefit of higherreaction rates in the production of hydroperoxides from the above-mentioned compounds.
It is an object of this invention to provide a process to enable the

2~ formation of a homogeneous reaction mixture when polyalkylbenzenes that are im~iscible in sulfolane are oxidized in the presence of sulfolane to obtain an increased rate of reaction in the formation of hydroperoxicles.

` ~395374'7 Su~mary o.f the Invention This .invention provides in a process for the hydroperoxidation of polyalkylbenzenes of the formula:

Rl ~,t ( R2 ' wherein Rl is an alkyl group having three to six carbon atoms, one of which is a tertiary carbon; and R2 is an alkyl group having one -to six carbon atoms and x is an integer from 1 to 3 and that have a poor solubility in sulfolane, which comprises contacting said polyalkylbenzene in the liquid phase with oxygen or an oxygen-containing gas mixture at a temperature of 75 to 150 C in the presence of sulfolane in an amount of 25 to 150 percent 10 by weight based on the amount of said polyalkylbenzene, the improvement comprising:
(a) contacting said polyalkylbenzene ~in the liquid phas~ with ` oxygen to oxidize the polyalkylbenzene at least by about10 percent based on tha amount of polyaIkylbenzene before the addition fo the 25 to 150 percent by weight of sulfo-lane and the continuation of the oxidation in order to effect a homogeneous solution of said polyalkylbenzene and sulfolane at reaction conditions.

Detailed Description of the Invention . Polyalkylbenzenes which are preoxidized by the process of this ; invention are those that are immiscible with sulfolane, Eor example, meta-diisopropylbenzene, para-diisopropylbenzene, S-isopropyl-m-xylene, tri-isopropylbenzene and diisopropyl toluene~ The polyalkylbenzenes become miscible with sulfolane after being treatedbY the peroxida-tion step of the present invention. The homogeneous solution, wherein sulfolane is the .~ ' solvent, and which is formed as a result of this miscibility, proyides many benefits~ These benefits are i.ll~strated in U.S. Patent No. 3,524,888.
The predominant benefi-t is that the rate of formation of hydropero~ides ~om the polyalkylated aromatic hydrocarbon is increased. General:Ly, the pro-cess of the present invention does not vary depencling on what polyalkylbenzene is used, but ~Iy minor variations are within the ability of one skilled in the art.

- 3a -.~

.
:

' ~' , . .
~ i: ' ~ - ' ~. ` ~9974~

In the preferred embodiment of the present invention meta-diisopro-pylbenzene (m-DIPB) is used as the polyalkylbenzene since its dihydroperoxide can be cleaved by strong acid catalysts to produce resorcinol. Also, the hydro-peroxide solution could be used for the production of a mixture of isopropyl-phenol and dihydric phenol by the acid-cataly~ed cleavage of the mixed DIPB-mono-/dihydroperoxide. The m-DIPB is added in the liquid state to any suitable oxidation reactor to give good gas/liquid contact, which is capable of maintain-ing oxygen pressure at the desired level and which may be equipped with an agitation device. Gaseous oxygen or an oxygen containing gas, such as air, or oxygen in admixture with a non-reactive gas, such as nitrogen, is normally added near the bottom of the reactor to improve the contact between the oxy~en and the liquid m-DIPB. The rate of oxygen flow can be varied over a wide range and such rates are known to those skilled in the art. The reaction is in the liquid phase at temperatures between 7~-150C. Atmospheric pressure is prefer-1~ able although superatmospheric pressures may be used. The reaction time is I suFficient to allow at least about 10 percent and preferably 15 to 25 percent ¦oxidation of the m-DIPB. Although any percent of oxidation of m-DIPB above ¦about 10 percent may be used, a practical limit above which the invention is Iless beneFicial and less economic is around 55 percent oxidation of m-DIPB.
¦The higher amounts, around 55 percent, of oxidation of m-DIPB are useful when I ¦the m-DIPB contains impurities.
¦ As ln conventional hydroperoxide producing processes, the reaction is ¦performed in the presence of small amounts of basic metal salts, oxides, or ¦hydroxides. The amounts used should be that which is sufficient to neutralize ¦acidic compounds formed during the reaction. The carbonates, hydroxides, and ¦acetates of the alkali metals, and oxides or hydroxides of alkaline earth metals ¦are preferred. Examples include magnesium oxide, sodium carbonate, sodium ¦acetate and the like. In addition to basic metal salts, oxides, or hydroxides, !a catalytic a~ount of an initiator such as diisopropylbenzene monohydroperoxide3~ ~is added to the reaction.

' I

lU99747 After the desired level of oxidation has been achieved the sulfolane is added to the reaction mixture. The amount of sulfolane added is between 25 to 150 percent based on the weight of m-DIPB. Lesser amounts do not give the four-fold or more increase in the rate of hydroperoxide Formations while the use of more than about 150 percent does not provide any additional benefits and ; would be uneconomical. After the addition of the sulfolane the reaction mix-ture is a homogeneous mixture. The oxidation of this homogeneous mixture is con tinued at the same conditions of temperature and pressure as the pre-oxidation until optimum oxidation is achieved.
The amount of oxidation may be measured by periodic sampling of the reaction mixture and determining the amount of oxidized products of m-DIPB
present in the reaction mixture. This determination may be performed by any method known to those skilled in the art.
The homo~eneous solution of hydroperoxides in sulfolane also permits ready separation of the hydroperoxide. The addition of water to the homogeneous reaction mixture after the oxidation causes a phase separation. By this ph~se separation the bulk of the hydroperoxide is carried by tlle solvent into the water phase. Then merely by decantation or the like~ the phases can be sepa-rated and the hydroperoxides concentrated or decomposed to useful produ~ts by conventional means. For example, the separated hydroyeroxides can be decomposed y acid catalysis to make mono- and/or dihydric phenols and acetone. In addi-tion the acid-catalyzed decomposition can be performed on the water-separated sulfolane phase rather than directly on the hydroperoxides.
The process can be operated as a batch process or can be carried out '~ as a continuous operation. The oxidation reaction zones may consist of one orore than one vessel. One vessel may be used for the preoxidation reaction zone nd another vessel may be used for the oxidation reaction zone. In the case of continuous operation, the effluent from preoxidation may be cascaded from the preoxidation vessel to the oxidation vessel to which the sulfolane is added.

- ;` 1~ 47 In order to better illustrate the operation of the process of the present invention the following examples are provided. These examples are for illustrat;ve purposes and do not limit the broader process as previously described.

Example 1 A stirred mixture of 100 grams of para-diisopropylbenzene (p-DIPB), 2.0 grams of sodium acetate and 1.0 grams of diisopropylbenzene (mono) hydro-peroxide was aerated at 125C. for 3.5 hours at which point the level o~ oxida-tion was 26.5 percent based on the hydroperoxide content calculated as mono-hydroperoxide. To this mixture 100 grams of sulfolane was added and the solu-tion was further oxidized for 3.5 hours at 125C. After this oxidation the total hydroperoxide content (based on the p-DIPB charged and calculated as DIPB-; monohydroperoxide) was 74 wt. percent~ The hydroperoxide product was analyzed by nuclear magnetic resonance (NMR) spectroscopy and it was ~ound that 65 per-cent of the p-DIPB was oxidized and the mole ratio of p-DIpB-mono-hydroperoxide -dihydroperoxide was 2.4.
' .
Example 2 A stirred mixture of 100 grams of meta-diisopropylbenzene (m-DIPB~, 2.0 grams of sodium acetate and 1.0 gram of diisopropylbenzene monohydro-peroxide was aerated at 125C. for 3.0 hours. At this point the level of oxi-dation was 19.4 percent based on the weight percent of hydroperoxide tcalcu-lated as monohydroperoxide). To this mixture 100 grams of sulfolane was added and the oxidation was continued for 7.0 hours at 125C. The total hydroperoxide content based on the m-DIPB charged and calculated as DlPB-monohydroperoxide was 96 weight percent. The hydroperoxide product was analyzed by NMR spectros-copy and it was found that 80 percent of the m-DIPB was oxidized and the mole ratio of m-DIPB-mono-hydroperoxide/dihydroperoxide was 1Ø Also, it was found : ~1 lO9g747 that only 5 percent oF the starting material had been converted to undesirable by-products.
According to the provisions of the patent statutes the principle and preferred mode of operation of the invention have been illustrated and de-scribed. However, it should be understood that within the scope of the appended . cla;ms the invention may be practiced otherwise than as specifically illustrated : and described.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a process for the hydroperoxidation of polyalkylbenzenes of the formula:
wherein R1 is an alkyl group having three to six carbon atoms, one of which is a tertiary carbon; and R2 is an alkyl group having one to six carbon atoms and x is an integer from 1 to 3 and that have a poor solubility in sulfolane, which comprises contacting said polyalkylbenzene in the liquid phase with oxygen or an oxygen-containing gas mixture at a temperature of 75° to 150° C in the presence of sulfolane in an amount of 25 to 150 percent by weight based on the amount of said polyalkylbenzene, the improvement comprising:
(a) contacting said polyalkylbenzene in the liquid phase with oxygen to oxidize the polyalkylbenzene at least by about 10 percent based on the amount of polyalkylbenzene before the addition of the 25 to 150 percent by weight of sulfolane and the continuation of the oxidation in order to effect a homogeneous solution of said polyalkylbenzene and sulfo-lane at reaction conditions.

2. Process according to claim 1 wherein the polyalkylbenzene is con-tacted with oxygen to oxidize about 15 to about 25 percent of the polyalkyl-benzene before the polyalkylbenzene is oxidized in the presence of sulfolane.

3. Process according to claim 1 wherein the alkylbenzene is selected from the group consisting of meta-diisopropylbenzene, para-diisopropylbenzene, triisopropylbenzene, diisopropyltoluene and 5-isopropyl-m-xylene.

4. Process according to claim 1 wherein the hydroperoxides produced are decomposed by acid catalysis to produce monohydric or dihydric phenols and acetone.

5. In a process for producing hydroperoxides from a polyalkylbenzene selected from the group consisting of 5-isopropyl-m-xylene, diisopropyl-benzene, triisopropylbenzene, and diisopropyltoluene by contacting in the liquid phase with oxygen at a temperature of 75° to 150° C. in the presence of 25 to 150 weight percent of sulfolane based on the amount of the poly-alkylbenzene to produce a product mixture containing the hydroperoxide, the improvement comprising:
contacting the alkylbenzene with oxygen at a temperature of 75° to 150° C in the liquid phase to oxidize at least about 10 per-cent of said hydrocarbon before the alkylbenzene is oxidized in the presence of the sulfolane to form a homogeneous reaction mixture.

6. Process according to claim 5 wherein the alkylbenzene is contacted with oxygen to oxidize about 15 to about 25 percent of the polyalkylbenzene before the polyalkylbenzene is oxidized in the presence of sulfolane.

7. Process according to claim 5 wherein the diisopropylbenzene is meta-diisopropylbenzene.

8. Process according to claim 5 wherein the diisopropylbenzene is para-diisopropylbenzene.

9. Process according to claim 5 wherein the hydroperoxides produced are decomposed by acid catalysis to monohydric or dihydric phenols and acetone.

10. A process for producing a hydroperoxide of a polyalkylbenzene selected from the group consisting of 5-isopropyl-m-xylene, meta- or para-diisopropylbenzene, triisopropylbenzene and diisopropyltoluene which comprises:
(a) contacting the polyalkylbenzene in the liquid phase with oxygen to oxidize about 15 to about 25 percent of the polyalkylbenzene;
(b) adding sulfolane in the amount of 25 to 150 percent by weight based on the amount of the polyalkylbenzene to form a mixture of partially oxidized polyalkylbenzene and sulfo-lane;
(c) contacting said mixture in the liquid phase with oxygen at a temperature of 75° to 150° C. to produce a mixture con-taining the hydroperoxide;
(d) adding water to said product mixture to separate the mixture into two phases; and (e) separating the phases and recovering the hydroperoxide therefrom.