Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2869
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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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
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di~tillation has a co~po~ition a3 mentlcned in Table II.
Tablo~
co~positio~(% by ~eight)
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:~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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