CA2099173A1 - Recovery of hydrogen peroxide - Google Patents

Abstract

Abstract of the Disclosure A process is provided whereby the hydrogen peroxide-containing oxidate from methyl benzyl alcohol oxidation is extracted with water and with ethyl benzene extractive solvent and an aqueous hydrogen peroxide phase is separated from an ethyl benzene solvent phase which also contains methyl benzyl alcohol and acetophenone, the improvement being that ethyl benzene is introduced into the extraction zone below the point of introduction of the oxidate, thus avoiding the possibility of formation of an aqueous hydrogen peroxide phase concentrated to a hazardous degree in hydrogen peroxide in the extraction zone.

Description

2099~73 RECOVERY OF HYDROGEN_PEROX~

Backqround of the Invention Field of the Inventio~
The present invention relate~ to the separation of hydrogen peroxide from methyl benzyl alcohol oxidate by water and othyl benzene extraction.
Description of the Prior Ar~
Hydrogen peroxide i8 an important chemical of commerce which is produced in VQry large quantities for u~e in a number o~ industrial applications. Th~ prQdominant process u~ed commercially ~or the production o~ hydrogen peroxide involves the oxidation o~ anthrahydroquinone, extraction of hydrogen peroxide and reduction of the resulting an~hraquinone to anthrahydroquinone which is reused. This process requireq very high capital expenditure~ in ~hat use of a working solvent with e~lciQnt r~cycla o~ v~rlous 2 0 proceg~ compone~tg i8 a necessity.
Sub~tantlal e~orts have been dir~cted to processe3 which involve dlrect combination o~ hydrogen and oxygen but thus far such proces~e~ have not ~ound widespread ~uccess.
Hydrogen peroxide has baen form~d by thQ oxidation of secondary alcohol~. At one tim~ ths production of hydrogen peroxide by oxidation o~ isopropanol waR practiced commercially. Other secondary alcohols which hav~ been mentioned as starting materials for hydrogen peroxide 20~3~73 .
production include 1-phenyl ethanol (methyl benzyl alcohol) and cyclohexanol. See, ~or example, U.S. ~atents 2,871,102-4 of Shell Development. In such prior procedures, difficulties have been encountered in the ~eparation and recovery of product hydrogen peroxide from the secondary alcohol oxidate mixtures. See, for example, Sh~ll U.S.
Patents 2,819,949, 2,869,989, 2,949,343, 3,003,853, 3,012,860 and 3,074,782.
Hydrog~n peroxide has also been formed by oxidation of very high boiling secondary alcohols such a~ diaryl methanol, the product hydrogen peroxide being stripped from the reaction mixture durin~ oxidation; see U.S. Patent 4,303,632.
In csrtain commercial tQchnologies, there are produced substantial quantities o~ various secondary alcohols. For example, in the coproduction o~ propylene oxide and 3tyrene monomer by the reaction o~ 0thyl b~nzene hydroperoxide with propylene, methyl benzyl alcohol is ~ormed and ultimately converted by dehydration to styrQne monomer. S~e U.S.
Patent 3,351,635.
In U.S. Patent 4,8g7,085, a proces~ ~8 de3cribed for the production o~ hydrogen peroxid~ by oxidation of methyl benzyl alcohol containing streams, such as those ~ormed in th~ oxiranQ proces~.
In U.S. Patent 4,897,252, a proce~ ~or th~ recovery of hydrogen peroxid~ fro~ m~thyl benzyl ~lcohol oxidation mixtures by ~thyl benz~n~ extraction i9 described. ~he 2~9~:L73 , present invention provides a further improvement in this proces~.
Summary of the Invention In the process of U.S. Patent 4,897,085 there is provided an improved process for the recovery of hydrogen peroxide from methyl benzyl alcohol oxidate involving the use o~ ethyl benzene as an extractive solvent. Efficient separation is achieved, and the process i~ especially advantageous in that only materials normally found in the co~mercial propylene oxide/styrene monomer proces5 are employed in the instant separation and recovery. In said process, ethyl benz~ne is admixed with the hydrogen peroxido containing oxidate, and the admixture is sub~ected to countercurrent extraction with water to separate hydrogen peroxide. The present invention represents the ~urther improvement over said proces~ wherein ethyl banzene is introduced into the water extraction column at a point below thd oxidate point o~ introduction ~uch that th~ water and the ethyl benzene contact ths oxidatQ ~eed at essantially the same point. This procedur~ avoids proble~ which might occur wh~r~ th~ oxidate and ethyl benzene are ad~ixed prior to contact with th~ oxtraction water where thare is a tendency ~or the ~ormation of a potenti~lly hazardous separate aqueou3 ph~e highly concentrsted ln hydrogen p~roxide. In especially advantageou~ operatlon, ths extraction is carried out in a singl~ column with the organic phase as the continuous phaso.

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, Brief ~escription of the Drawina The accompanying drawing illustrates in schematic form a suitable embodiment o~ the invention.
Detailed ~escription of the Invention In U.S. Patent 4,897,252 there is described a method for the production of hydrogen peroxide by oxidation of methyl benzyl alcohol with molecular oxygen. Acetophenone is a coproduct of the oxidation.
The present invention provides an e~fective method for the recovery of hydrogen peroxide from methyl benzyl alcohol oxidate reaction mixture~ such as those formed in the process described in said patent.
In accordance wlth the invention, the methyl benzyl alcohol oxidate mixture, which compri3es methyl benzyl alcohol, acetophenone and hydrogen peroxide, i9 subiected to water extraction in an extraction column to separatQ product hydrogen peroxide. Ethyl benzene i9 also employed aA an extractive solvent to a~hanc~ the ~Qparation o~ organic and inorganic matorial~. A key feature of the prQ~ent inv~ntive process i~ the provision for th~ addition o~ ethyl benzene to the extraction column at a point below the point o~
introduction oP the oxidate mixture. Water i~, o~ course, introduc-d at an upper point and flows downwardly a3 it extracts hydrcgen peroxide. Ethyl benz~ne ~lows upwardly and serve~ to cnhance eparation o~ acetophanone and unreacted m~thyl benzyl alcohol from aqueous hydrogen peroxide. The }owQr section oP the ~xtract$on column, r~ch in ethyl benzene, extracts organics from the aqueous phase containing hydrogen peroxide, while the upper section extract~ hydrogen peroxide from the oxidate.
By introducing ethyl benzene below the oxidats point of introduction, the oxidate effectively contacts both the downflowing water extractant and the upflowing ethyl benzene extractant at the same time, and as a resuLt the formation of a separate, aqueous phase highly concentrated in hydrogen peroxide is avoided. Ethyl benzene reduces the solubility of water and hydrogen peroxide in the oxidate. If ethyl benzene is added such that it is admixed with oxidate without sufficient water present, a concentrated hydrogen peroxide in water mixture (possib}y over 70% hydrogen peroxide) tends to phasQ out.
It i~ preferred to carry out the extractive separation in a single extraction column since, with a plurality of column , aqueous hydrogen peroxide must be pumpad from one zone to another, thu~ introducing potential hazards into the operation. It i~ al80 preferred to U8Q the organic as ths continuou phase in tho extraction zone.
The u~ o~ ethyl benzene as the extractive ~olvent for re~ov~ry o~ hydrogen peroxide from methyl bQnzyl alcohol oxidato h~- cert~in uniqua advantage~ as described in U.S.
Patent 4,897,085. In the ~irst place, ethyl benzene i8 highly effective as the extractiv~ ~olvent. Unre~cted methyl benzyl alcohol a~ well a5 acRtophenone are extracted into the ethyl benzene Qolvent while water and hydrogen _ 5 _ 2~9~17~
, peroxide are effectively excluded. In the second place, ethyl benzene is an essential feedstocX in the commercial propylene oxide/styrene monomer process which also can provide the methyl benæyl alcohol for the hydrogen peroxide production. Thus there is outstanding synergy between the technologies.
Referring to Figure 1, a methyl benzyl alcohol stream is introduced via line 101 into oxidation reactor 102.
Most suitably, the methyl benzyl alcohol stream also comprises acetophenone and represents a process stream conventionally available from propylene oxide/styrene monomer technology. Methyl benzyl alcohol i5 oxidized in reactor 102 by contact with molecular oxygen introduced a~
air via line 103. Conditions of the oxidation to ~orm hydrogen peroxide and acetophenone are as ~e~cribed in U.S.
Patent 4,897,085, the contents o~ which are incorporated herein by reference.
Liquid reaction mixture is w$thdrawn from reactor 102 via lin~ 104 and this oxidate co~prisas unreacted methyl benzyl alcohol, acetophenono oxidation coproduct as well as such acetophanone a~ may be present with tha methyl benzyl alcohol ~eed, and hydrogen peroxide product. Small amounts o~ wat~r may also ba present, below 4% by weight o~ the reaction mixture; preferably below 2% and mo3t pre~erably balow 1%. Thi~ oxidate mixture pa~s~3 to the intermediate section of ~olvent extraction co}umn 105.

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An ethyl benzene stream is introduced via line 106 to extraction column 105 at a point below the point of introduction of th~ oxidate, preferably near the bottom as shown. The light organic phase passes upwardly in 105, countercurrently contacting a heavy aqueous phase pas~ing downwardly from the top, water being introduced via line 107 near the top of column 105. The H22 contained in the organic feed oxidate is extract~d into the aqueous ~tream which exits from the bottom of the column via line 108.
The organic phase, now with H22 product removed, exits column 105 from the top via line 109 and passes to distillation column 110 wherein it is distilled to separate ethyl benzene overhead via line 111 from the hi~her boiling methyl benzyl alcohol/acetophenone mixture which i~ removed via line 112. The ethyl benzene can be recycled to the extraction or used 21sewhere. The methyl benzyl alcohol/acetophenon~ i9 especially advantageou~ly dehydrated in accordance with Xnown procedure~ to form ~tyrene mono~er from the ~ethyl benzyl alcohol, followed ultimately by hydrogenation o~ th~ acetophenone to produce more ~ethyl benzyl alcohol.
In th- anthraquinone-based technology curr~ntly employ~d, th~ extractions involve the aqueou~ phase as the continuou~ phaso whlch re~ults in large inv~ntorie~ o~
concentrated hydrogen p~rox$do in th~ ~xtraction column~
The inventory of concentrated hydro~en peroxide in th~
extraction column i~ reduced in the preferred practice o~

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the invention wherein the organic phase is the continuous phase.
The aqueous hydrogen peroxide phase remov~d from eolumn 105 can be treated by conve.~tional procedures to further concentrate and purify the hydrogen peroxide product. In especially preferred practice, this stream is treated, as described in copending Serial No. filed on even date herewith, with an adsorptive resin to further remove organic impurities.
Practice of the invention avoids the ca~ where ethyl benzene contacts the oxidats before extraction water, and thus avoids the formation of a separate aqueous phase concentrated in hydrogen peroxide to a possible hazardous level.
The ~ollowing exampla illustrates the invention.
Unless otherwise indicated, part~ are weight~ per hour and percentage~ are by weight.
Ex~le A methyl benzyl alcohol oxidat~ in amount of 1000 parts comprised o~ 56.0% ~Qthyl benzyl alcohol, 37.9%
acetophenone, 5.3% H22 and 0 . 8% H20 i~ removed ~rom oxidizor 102 by moans o~ line 104. Thi~ stream i8 introduc~d into a Rarr extract:Lon column 105 at an intermodiate point whersin thera are three theor~tical extraction stag~ both abov~ and below the point o~
introduction. About 500 part o~ an ethyl b~nzene -~tr~a~ is introduced into column 105 at a point near th~ bottom.

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To the ~op of lOS is introduced 150 parts of a pure water stream. The extraction column 105 operates at 200C
and atmospheric pressure. The organic product from column 105 in amount of 1445 parts, compri~ed of 34.6% ethyl benzene, 38.8~ methyl benzyl alcohol, 26.2'~ acetophenone and 0.4% H20, exits the top of column 105 via :Line 109 and is sent to ethyl benzene distillation unit llo. The aqueous product from column 105 in amount of 205 parts, comprised of 200 ppm methyl benzyl alcohol, 200 ppm acetophenone, 25.8~
lo H202 and 74.2% H20, exits the bottom of column 105 via line 108. This stream can be concentrated and ~urther purified by conventional methods, but preferably is treated in accordance with the proce~s d~scribed in copending Serial No. _ _ filed of even date herewith.
In column 105 the organic phas~ ie the continuo~s phase. The upper and lower sections of column 105 hav0 different diameters to maintain th~ ~am~ flow velocities in the two sections.
The ethyl benzene distillation unit 110 which receive~
organic product ~rom th~ H22 extractor 105 via llne 109 -~eparate~ athyl benzen~ ~or recycl~ to the extraction or for usage ~ls0wher~. The ov~rhead stream ~rom 110 in amount of 506 p~rts comprised of 98.8~ ethyl benz~ne and 1.2% H20 exits via line 111; the water can later be decantad from this stream. The bottom~ product from 110 in amount of g39 parts compris0d o~ 59.6% methyl b~nzyl alcohol and 40.4%

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acetophenone exits via line 112 and can be converted to styrene monomer in accordance with conventional procedures.
In operation as above indicated, most of the organic impurities which could cause explosion hazards are removed prior to the time the extract stream concentrated in hydrogen peroxide reaches the column bottom. Also by the use of one column, intermediate pumping of hydrogen peroxide is avoided.

Claims (2)

I Claim:

1. In a process for the extraction in an extraction zone of hydrogen peroxide from a methyl benzyl alcohol oxidate mixture containing methyl benzyl alcohol, acetophenone and hydrogen peroxide wherein ethyl benzene and water are employed as extractive solvents, water being introduced in the upper section of the extraction zone, the improvement which comprises introducing ethyl benzene solvent into the extraction zone at a point below the point of introduction of the oxidate mixture.

2. The process of Claim 1 wherein the organic phase is the continuous phase in the extraction zone.