CA1105052A - Method for processing a tar containing benzyl benzoate - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates to a method for processing a tar contain-ing benzyl benzoate. According to the invention a tar containing benzyl ben-zoate is processed by subjecting it to a hydrolysis or ammonolysis reaction.
Thus the benzyl benzoate with a high boiling point which is difficult to separate from some tar components by distillation is converted into the benzyl alcohol with a considerably lower boiling point in addition to the benzoic acid or a salt or amide thereof, which differs considerably in chemical pro-perties from the benzyl benzoate and the tar components. Pure benzyl alcohol can be recovered from the hydrolysed or ammonolysed mixture, e.g., by dis-tillation. Benzyl alcohol is a useful product that is used in the scents and flavours industries, Hence, it is achieved by the method according to the invention that a waste product with no applications so far is converted into a useful product.

Description

The inverltion relates to a method ~or processing a tar containing benzyl bsnzoate.
Mixtures oP this type may form in the o~idation o~ monoalkyl benzsne compounds with a gas containing molecular o~ygen. The oxydation o~ tolusne i~ applied on a technical ~cale, and the b~nzyl ben70ate that ~:
~a~ ~orm then is the unsubstituted b~nzyl ben70a~e, i.e. that both benz~n~
rings o~ the benzyl benzoate sxe u~substituted. Because o~ the technical importance the invention ~ill b~ explained mainly wlth reference to the toluene oxidation and the tar than obtained, which contains unsu~qtitu~ed benzyl benzoate.
Th~ invention may also be used, however, for tar that contains subs~ituted bcn3yl benzoates and which may ~orm, i'or in3tanc~, in the o~idation O.e othsr alkyl-benzene compounds.
~ he oxidatlon reac~ion may take plsce ei~her ln the liquid phasa with, e.g., a cobalt and/or manganase salt that is soluble in the reaction medium a.~ a ~ataly~t, or in the gaseou~ phase with, e.g. J a catalyst based o~ ~n oxlda o~ vanadium or another tran~ition ~etal (Stani'ord Research }n ti~u~o (SRI)~rsports No. 7 (1965), 29;;No. 7A (1968), ~41; No. 7 1~1976), 53).
All or part oi the benzoic acid, toge~her with all products w~th lower bolling polnts may be dlstilled ~rom the reaction mixture, which contaln3 benzoic acid, benzyl bonzoate, other products ~ith higher boiling polnts than bsnzoic acid and her~ refarred to by the name o~ 'tar residua', unconverted toluen3 and by-products with lowar boiling points than benzoic aaid, such as benzyl alcohol and benzaldehyd~, and the distillate may be processed ~urther ~or pure b0nzsic acid so that a tar containing benzyl benzo~te and, possibly, some benzoio acid i9 le~t as a resldw. Thi5 residu can be us~d as the start~ng waterial ~or the method according to ~he invention.

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A tar contalning benzyl benzoate which may also be used as the s~arting material ~or the method according to the invention can also ~orm i~ ths abovementioned distillate is heated whether or not i~ the presenc~
o~ an esteri~ication/re-esteri~ication catalyst, e.g. sulphuric acid, phosphoric aaid, borotrii'luoride or ~inc ace~at~t in order to e~tsriXy or ro-~st~ri~y be~zylalcohol and/or light benzyl esters, such as benzyl ~ormiate and benzyl acetate, into benzyl bsnzoate, e3pecially i~ ths ~i~ture still contalns benzaldehyde during thi~ eeteri~ication.
It is particularly di~ic~lt to r~cover use~ul product.~ ~rom such o A tar contalning ben~yl benzoato. What can be done 13 ~ di~til ben2yl ben~oste ~ro~ the tar re~idu, but a pure benzyl-benzoate produot can hardly be obtained in this way. Applicant hae found that the ~luorenone component o* the tar pre~ents ~pecial problems. For, it appears that ~luorenon0 can hardly be ~eparat0d ~ro~ benzyl benzoate. But be~ldes ~luorenone, o~her unidenti~ied comp~unds may play a part.
Acaording to the invention a tar contalnin; benzyl benzoa~s is processed by s~b~ecting lt to a hydrolyYis or a =onolysis reaction~ Thus the benzyl bQn~oa~e ~ith a high boiling point wh~ch i9 di~cult to ~epara~e ~rom so~e tar components by ditlllation is converted into'the benzyl alcohol ~ith a aon~derably lower boilin6 point in addition to the ben~olc acid or a ~alt or a~ide thereo~, which di~er~ considerably in chemical properties irom the bsnzyl benzo~te a~d the tar components.
Pure benzyl alo~hol can be recovered ~rom the hydrolysad or ammo~olysed mlxture, e.g., by distillation. Ben2yl alcohol is a usei'ul product that is used in the scents and ~lavou~s industrles. Hence, i~ is achieved by the msthod according to the inv~ntion that a wast~ product with no appl1cations ao i'ar ls converted into a use~ul product.

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~L h The hydrolysi~ o~ the tar can be e~iected by means oi a basicsolution, particularly an aqueou~ sodium hydroxide ~olutio;l or a soda solution. Alqo potassium hydroxlde, ~or instance, or calcium hydroxide might be u~ed. But there is mainly a need o~ sodium benzoate aq a reactien product, 90 that the hydroly~is i9 pre~erably e$fected ~ith a basic qodiu~
G~mpDund. The benzoate salt obtai~ed c~n ba ~eparate~ Xro~ the tar by .: ::
~xtraction with water. In tead o~ hydroly~is, aDmonolysls may be used9 e.g. with am~on~s, liquid a~monia, or, iP 50 desired, an amine, which, pr~erably, has a boiling point at atmo~pheric pr~asure o~ ~t most 150 C.
I~ 50 do~ired, th~ benzoata salt or bonzamide thus ~btained can ~ -be c~ert~d into vary pure ~re* benzoic acid by reaction with a strong aeid, e.g. sulphuric acid or ~itric acid.
I~ ~o d~ired, th~ hydrolysl~ r~action may also be ~i'ect~d by mean~ o~ a~ acid, in~tead o~ a ba~ic cstalyst,~e.g. A mineral acid, such a~ ~ulphuric acid or phosphoric acid. Naturally, ~ree bonzoic acid will then iorn, which9 1~ 50 de~ired, may be recov~red by distillation or by.
extraction~ o.g., be mea~.~ o~ water.
~ The temp~rature in the hydrolysi~ or ammonolysis may rangH, e.g., bet~e~n 30 snd 200 C. The pressur~ is not crltlcal a~d pre~erably ranges botw~ nd 10 ~tm. ~or practlcal rea~on~.
Un~ortunately, it ia extremely di~icult to recover not enl~ the ben~yl alcohol, but also the benzoate salt, e3peclally the useiul sodium b~nzoat~, in a pura ~o~ irom thQ reaction mixture obtained in the basic hydrol~ oi the benzyl beo2oateJtar mlxture. Some co~ponents oi the tar perslstently combin~ ~ith the sodium benzoate, e~pecially in th~ presence o~ benzyl alcohol.

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According to the invention this problem i9 solved by extracting the hydrolysis reaction mixtura with an organic extracting agent which cause~ sepa~ation into liquid phase~ with the hydrolysi~ reaction mixtnre.
In ~his separation the b~nzyl &lcohol and tha t r components pass into ~he orgsnic phase, ~hile the aqueous pha.qe is a virtually pure ~odium-benzoate 301u~ion from ~hich solid pure sodiu~ benzoate ca~ be reco~red i~ a simple way. Pure benzyl alcohol a~d the extractlng sgent can be recovered ~rom the organic phsse by distillation.
Exa~ple~ o~ suitable organic extracting agent~ are aliphatic, aromatic and mixed aliphatic-aromatic hydrocarbons ~ith, preFerably, at most 1~- carbon atom~ per ~ol~cul~, ethors, eRters, and halogenatad and, e~pecially chlorinated or bro~inated hydroca~bons with normal boilin~ points, pr~ferably not exceeding 250 C. Specii'ic examples are gasoline, hep.tane, benzena, toluene, the xylenes, diisopropyl ether, amyl acetate, ethyl benzoate, chloro~orm, 1,2-dicblor0thene, and 1,1,1-trichlorethane.
:Special pre~erence is give~ to toluene, as it i5 available in large quantities in a tolu~ne-oxidation work~ and e~ects pr~per qeparation.
According to a ~ultable embodiment o~ ~he method according to the invention, the product mi~ture o~ the hydroly~is re&ct~on i9 ~ed to an ~xtraction column, to which the e~tracting a~ent i9 al.qo i'ed.
It is also po~ible ~or the extracting agent to be pre~ent during th~ h~droly~i_ reaction~ ID thi~ ca~o it iR recommendable, o~ course, to chooqe an e~tra~ting a~ent ~hat i5 iner~t under the reaction condit~on~
co~cerned. Ai'ter the reaction th~ product ~ixture i9 then sep~ated into an organlc layer con~aining~benzyl alcohol, tar re~ldue~ an~ extracting agent and an aqueou~ layer containing sodium benzoate. . .
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The hydrolysi3 may then be eP4ected in an extraction column throu~h which the tar containing benzyl benzoate and the basic solution are passed in countar-current relation to the extracting agent.
The inven~ion will be elucidated with re~erence to the ~ollowing no~ 3t~1cting example.

Tha liquid resction product o~ the ogidation o~ toluene in the liquid pha~e with air in the preqence of cobalt acetate a~ a catalyst (d~gre~ o~ conversion o~ toluene about 2070 by weight~ 19 distilled until virtually.s11 benzoic acid and component~ ~lth lower boili~g point3 hsve bee~ ~moved grom the resction product. The residue i~ subJected to ~ilm evaporstion at a temperature o~ 260 C and ~ pres~ure o~ 25 mm o~ Hg.
An aqueous sodium hydroxide solution (1470 bg weight o~ NaOB) iq added to the dl~tlllate obtained iD the ~llm e~aporation, a mixture o~ benzyl benzoate :and tar, ln Rn hydroly~i3 reoc~or consistin~ oi a glass ~la k with re~lu~
cond~n~er aDd atirring mechanl3~. Th~ co~position o~ the mixture thus obtained 1~ gi~e~ in Table I ~'be~ore hgdrolysis'~. The tar residue consist~, i.a., o~ Pluor~none (about 40% by weight relative to the tar), 1,2~diphenyl ethan~, and 2-methyl, 3-methyl and ~-methyl diphenyl.~.
~ The:mlxture in th~ hy~drolysis reactor i~ ~tirred at 100 & ~or 30 minutes, a~ter which virtually all banzyl benzoate has been hgdroly~ed.
The compositioL o~ the reactoF contents a~ter hydrolyjis is al~o given in Table I.
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Table I

compo~ition composition b~ore hyd~oly~i~ a~ter hydrolysis ~ by ~eight) ~0 by weight~

be~zoic acid 8.7 benzyl benzoate ~6.1 C ~.~ -1:2r re~idue ~7 -~7 sodium hydro~ide 8.1 _0.3 w~ter 48.4 4g.8 benzyl alcohol - 13.3 ~odium benzoate - 27.9 - Th~ contents o~ the hydrolysis reactor are extracted ~our tlmes .
with equal po~tiona e~ toluene ~the total amount i9 equsl to twice the weight o~ water preqe~t). The layers o toluene thus obtalned are added togo~her and are waqhed with water (10% by weight rel~tive to the amount o~ toluene present). A~ter separation o~ the layer~, the washing water is added to the abovem0ntioned a~ueou~ layer.
The toluene and th~ =ater aro distilled st atmospheric pressure ~rom the ~hed toluene layer. Nest, the re31due i9 di3tillad at 70 C
~nd 1 mm o~ Hg. The top ~low oi this d~ 9tillation con~ist~ o~ virtually pure benzyl ~lcohol (purity over 99~ by woigh:t). The re~idue o~ the .
di~tillation has a co~po~ition a3 mentlcned in Table II.

Tablo~

co~positio~(% by ~eight) . . . _ _ _ _ _ " " , . . .
:~luoranone ~ 38.9 re~aining tar re~idue 57.8 benzyl alcohol ~ 3.3 he~zyl benzoate 0.1 ~ , .
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, , . ' : : ~ , ' ' The yield o~ benzyl alcohol a~ter di~tillation relative to benzyl benzoat0 is over 99%.
Solid sodium b~n~oate i~ obtained virtually quantitatively ~rom the co~bin~d w~ter layer by removal o~ water.

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Claims (6)

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

1. Method for processing a tar containing benzyl benzoate, characterized in that the tar is subjected to a hydrolysis or ammonolysis reaction.

2. Method according to claim 1, characterized in that the hydrolysis reaction is effected with sodium-hydroxide or sodium carbonate and sodium benzoate is recovered from the product mixture.

3. Method according to claims 1 and 2, characterized in that a benzyl alcohol is recovered from the product mixture of the hydrolysis or ammonolysis reaction.

4. Method according to claim 2, characterized in that a benzyl alcohol is recovered from the product mixture of the hydrolysis or ammonolysis reaction and the product mixture is extracted with an organic extracting agent.

5. Process according to claim 4, characterized in that the extracting agent is toluene.

6. Method according to claim 4 or 5, characterized in that the hydrolysis reaction is carried out in the presence of the extracting agent.