CA1120949A - Phenol production - Google Patents

Phenol production

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Publication number
CA1120949A
CA1120949A CA000307902A CA307902A CA1120949A CA 1120949 A CA1120949 A CA 1120949A CA 000307902 A CA000307902 A CA 000307902A CA 307902 A CA307902 A CA 307902A CA 1120949 A CA1120949 A CA 1120949A
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CA
Canada
Prior art keywords
benzoate
benzoic acid
oxide
temperature
heating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000307902A
Other languages
French (fr)
Inventor
Placido M. Spaziante
Luigi Giuffre
Giancarlo Sioli
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De Nora SpA
Original Assignee
Oronzio de Nora Impianti Elettrochimici SpA
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C39/00Compounds having at least one hydroxy or O-metal group bound to a carbon atom of a six-membered aromatic ring
    • C07C39/02Compounds having at least one hydroxy or O-metal group bound to a carbon atom of a six-membered aromatic ring monocyclic with no unsaturation outside the aromatic ring
    • C07C39/04Phenol
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C37/00Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
    • C07C37/01Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by replacing functional groups bound to a six-membered aromatic ring by hydroxy groups, e.g. by hydrolysis
    • C07C37/055Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by replacing functional groups bound to a six-membered aromatic ring by hydroxy groups, e.g. by hydrolysis the substituted group being bound to oxygen, e.g. ether group
    • C07C37/0555Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by replacing functional groups bound to a six-membered aromatic ring by hydroxy groups, e.g. by hydrolysis the substituted group being bound to oxygen, e.g. ether group being esterified hydroxy groups
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/41Preparation of salts of carboxylic acids
    • C07C51/412Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/52Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE

An improved process for the production of phenol in high yields with low tar formation comprising oxidizing benzoic acid with an oxide of copper or molybdenum in the presence of excess benzoic acid and substantially in the absence of water to form the corresponding metal dibenzoate, heat-ing the said dibenzoate in the absence of oxygen and water to decarboxylate the same and form phenyl benzoate and hydrolzying the phenyl benzoate with water to form a benzoic acid and phenol mixture and recovering phenol from the said mixture, the improvement comprising performing the said steps separately.

Description

:

( ~~ STATE OP T~IE APT

; ¦ The production of phenol from benzoic acid is -Il known and the process generally comprises oxidizing toluene ¦I to for~ benzoic acid, oxldizing the latter in the presence of a catalytic amount o~ a copper catalyst to form phenyl benzoate and hydrolyzing the latter to obtain phenol.
Ho~ever, this process produces a considerable amount o~
¦1 undesirable by-products such as tar. U.S. Patent 3,639,452 . I acknowledges this fact and attempts to avold this difficulty I by conductin~ the oxidation of benzoic acid with benzoic acid, ! anhydride present in large amountsr However, this entails .' ~[`. ., . .

~ ~ -thc usc o~ an undesirably large a~loun~, of benzoic ac-ld anhydricle. Furthermore, excessive decarboxylation of the j benz.oic acid with benze}le evolution appears to occur. An ~ attempt to improve the ylelds is described in U.S. Patent .' 5 Il No. 2~766,?9ll where the phenyl benzoate ~as produced with a ¦, copper oxide oxidizing agent in the absence o~ elemental oxygen.

OBJECTS OF T~IE INVF.NTION
!' ! ~
i It is an ob~ect o~ the invention to provide an 10 ~ improved process for the production o~ ~ benzoate from j ' benzoic acid while avoidin~ substantial tar formation.
¦l It is another object of the invention to provide ~1 an improved process for producing phenol in hl~h yields in a simpre~ contlnuousmanner.
C 15 I These and other objects and advantages of the ; ~¦ invention ~ill become obvious-from the following detailed ¦ description-~, .. I . .
i THE INVENTION
. . .
i The no~el process of the invention for the pre-ll paration o~ phenyl benzoate in high yields comprises ~eastin~
benzoic acid with cupric oxide and/or cuprous oxide and oxygen to form cupric benzoate or with molybdenum oxide to j! form molybdenum dibenzoate and decarboxylatlng theprcdust by;
¦I heating in the substantial absence of oxygen and water to f~m a 25 ¦I mixture of phenyl benzoate and cuprous benzoate or molybdenur benzoate and optionally recovering phenyl benzoate from the r~ ' I
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mixture. It is also possible to recover phenol ~rom the ixture as discussed in~ra.
It is essentlal for the high ylelds of the process j to avoid the simultaneous presence o~ phenyl bcnzoate, water , and an oxidizin~ agent (free oxygen or CuO) in the decar ¦~ boxylation step and to avoid the sirnultaneous presence of phenol and oxidizing agent during the productlon of phenol I, from phenyl benzoate.
¦ The formation of cupric benzoate or molybdenum ¦I benzoate is preferably effected at a temperature betT.een 100 and 200C, most preferably at 120 to 170C. Some ~;~ater !! of reaction ls formed during this step which has to be ¦, eliminated before proceeding to the decarboxylation step.
The water may be removed by azeotroplc distillation with a !I hydrocarbon such as benzene, toluene~ xylene, etc.or by bubbling a hot gaseous phase throug~l the liquid or any other ¦ suitable means.
. The decarboxylation of the benzoates to form . I phenyl benzoate and cuprous benzoate or molybdenum benzoate :20 jl ~Yith carbon dioxide evolution is effected under non-oxidizin~ r ¦I conditions by heatlng at 190 to 250C, preferably not higher¦
than 220C. During the decarboxylation ~tep, it is possible¦
-li that water may be formed by sel~-dehydration of benzoic acid ,I depending upon the temperature selected. The water may be . ~ , ! ' . .
- 25 !I removed from the reaction mixture by adding a dehydrating jl agent to the mixture such as benzoic acid anhydride or by azootropic diati~lat1~n ~r wcter wLth a hydrocar~on s~ch a~

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I' xylene, toluene or benzene or by bubbllng a dry, inert gas through the mixture.
j In a pre~erred mode o~ the process of the in~ent~
¦~. ion, a porti.on Or the metal oxide is replaced ~ilth up to - ¦
! 15%, pref`erably 5 to ~.0%, by welg~t of the total metal oxides with an alkallne earth metal ox:ide such as magneslum , oxide which i3 converted into magneslur~ benzoate. The addi-tion of alkallne earth metal alds. the complete decarboxy- !
lation to phenyl benzoate. Wlthout the addition o~ an o 3 alkaline ear-th metal, the reaction mixture may contain as ¦I much as 25~ of benzoyl salicylic acid. The mixture result-ing from the decarboxylation step comprises phenyl benzoate,¦
¦¦ benzoic acid,;cuprous.benæoate, cupric benzoate, magnesium benzoate, benzolc.acid anhydride and possible small amounts ¦
l of other components.
~ . In a preferred mode of the process o~ the invent- ¦
. ¦ I ion to produce phenol, the mixture of phenyl benzoate and cupric benzoate.is hydrolyzed with water.at elevated tempera . . ¦ tures and pressure to convert.the phenyl benzoate to benzoic; 20 I acid and phenol and to convert the copper benzoates to . , benzoic acid, cuprous oxide and small amounts o~ cupric . : ¦
.. ¦ oxide whlle any magnesium benzoate is converted to magneslum . I hydroxide, the solid metal oxides are removed and phenol is recovered fr~m the a~ueous phlse.

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The hydrolysis step is preferably effected at 160 i ~o 260G, most preferably at about 220C and at a pres~;ure of 40 Kg/cm and preferably 25 Kg/cm atmosphere ¦¦ gauge. The solid metal oxides are separated from the llquid phase by appropriate means such as¦
' filtration or centrifu~at~on and they may therl be diLuted and recycled to the c~lpric benzoate step and the phenol can ¦
' be recovered by conventional ractionation means. Alterna~
tively the excess water and phenol may be removed by distil-lation and the recoveredslurry ~an be recycled to the cupric , benzoate step. Pure phenol is recovered again by conven-tional means.
Referring now to -t~le dra~iinæs:-Fig~: 1 isadiagra~natic flow sheet of an embocli-i ment of the process illustrating the steps of forMing the !'. _.
¦~ cupric benzoate from the copper oxides, heating this cupric ! benzoate to generate phenyl benzoate, hydrolyzing phenylbenzoate to produce phenol and metal oxides, separatin~ and ¦, recycling the solid oxides followed by the final purifica-l¦ tion of phenol by fractional distillation.
Fig. 2 ls an alternatlve process for the reco~ery steps in ~hich phenol is distilled from the reaction mixture *rom the hydrolysis step.
ji These drawings illustrate a typical embodi~ent which may be modlfied as ~;~ill be u~derstood by those skilled in the art. The principal steps illustrated in Fig. 1 ¦l include Metal Benzoate Formatlon Zone 10, Heatlng or Decom-, ¦ position Zone 20, Hydrolysis Zone 30, Filtration Zone 40 a d Phenol Fractlo~at 10A zDr e 50.
`I
' .

i ~9 ,, ~

In a typical exa~ple in tlhich all parts or pro- j portions are by weigh~, cupric ~enzoate is formed ln the Metal Formation Zone by reactin~ benzoic acid with copper ¦ oxides. As a gener;al rule, it is ad~antageous.to conduct , the oxi.dation and heating in the.presence of magnesium oxide ¦l and there~ore, magnesium oxide is also fed to the metal.
¦ benzoates formation skation 10. The amount Or magnesium oxide required.is small, rarely being more than 5 to 10% by I
, weight of the total oxldes fed to the reaction. Copper 1I carbonate or copper hydroxide serve as equivalents to copper oxide.

The metal benzoates are produced.simply by adding the metal oxides di~ectly to a pool of moli,en benozic acid : I in any suitable reactor such as a kettle. This mixture is . , then fed to reactor 10 where the copper is stabilized in the . ¦ cupric form as cupric benzoate by action of oxygen o.r the : ~ . . I addltion of the metal oxides to the benzoic acid can take ¦ place.directl~ in the reactor 10, while molten benzoic acid . I at a convenient temperature, usually at 125 to 200C, is ~ed;
. through line 1. As shown, the reactants are supplied in .¦ the ratio of 208.1 parts of met~l oxides and 1362.8 parts ofj ¦¦ benzoic acid by weight. More specifically, for what is re-¦, sulting from the subsequent steps~ the metal oxide distri-bution is typically as follows: ~ ~ .

I; . g 7%
'~ CuO g%
u20 84% .
.1, Air is bubbled throu~h line 3 into 10 at a flow rate . . ! corresponding to 97.5 par-ts hy weight of air in the reaction mixture.

' ' - ' .

.
.

~ ~L 2~ 94$~
i:
j ~
As a consequence o~ the reactions in reactor 10, ater is evolved in a quan~ity as ~ndicated in line 4 and cupric benzoate which is practically insoluble :Ln benzolc acid, is produced. It has been foun~ helpful to have the 1 presence of an adequate hydrocarbon such as toluene or xylene to improve the dispersion o~ the solld phase and to strip azeotropically the water rrom the system. The reactor 10 is conveniently a kettle provided with a stirrer means to supply the reac-tants and maintain them uniformly mlxed, means to feed air or other gas containing oxygen and means ; to withdraw evolved gaseous products.
j , The temperature o~ the reaction mixture in reactor' 10 should be high enough to oxidize cuprous benzoate to cupric benzoate but generally is low enough to prevent f~
15 ll ma-tion~~ phenyl benzoate. Consequently, the reaction mix-, ;
ture is generally held above about 100C but rarely above 220C, generally between 120 and 170C. A gas containing oxygen is fed into the lo~er part of reactor 10 and this gas is conveniently air although other oxygen sources ~iiay supply ~I the gas, if desired. Traces of benzoic acid and other ¦~ organics may also escape from the oxidation reactor, but may !;
be conveniently condensed and refluxed back to the reaction kettle.
, The time o~ reaction usually is a matter of li minutes and the process may be conducted batchwise or con-,~, tinuously. If batchwise, the liquid or dissolved reactants ¦, are placed in the reactor and oxygen is fed in until the i,i , .
` r il ' ', :':`. : ' . ::

.

`

~l i ; ' oxidation of cuprous copper has proceeded to the desired degree. Complete oxidat:ion of cuprous to cupric may be accomplished, if desired but generally it is advantageous to ( I achieve only a partlal oY~idation so that the reaction mix-!' t~re al~ays contains sorne cuprous ben%oate, even at the end of the oxidat;ion. If -the reaction is conducted con-' tinuously~ the reaction mixture may have t~e composition o~
¦I the stream leaving through line 5 with the reactants bein~
1` gradually added, continuously or intermittentlyJ at the 1~ average rate at which they are consumed.

In either case, a stream is withdrawn from oxida- ¦
~, tion zone 10 through line 5 and has the composition ' benzoic acid 656.2 !~ cuprous benzoate 411.9 li cupric benzoate 743.1 i magnesiuM benzoate 92.1 ¦ accompanied by a convenient quantity of an hydrocarbon to better suspend the solid cupric benzoate. This q~antity can ¦ be ln the order Or 700 to 1000 parts. As is apparent, a ljl substantial proportion of cuprous benzoate is o~idized sub-il stantially according to the equation:
2 Benzoic Acid ~ 2 Cu Benzoate + 1 02-~2 Cu j, (Benzoate)2+ H20 !l Benzoic acid is partially consumed to ~orm the cupric salt.

l' The stream withdrawn throu~h line 5 is ~ed tu De-¦¦ composition or Heatin~ Zone20 ~hich maybe a stirred ~ac~;eted ~ettle capable Or maintainlng the mixture ln the liqui~

. . .
.

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state substantially as a benzoic acld solutlon of the various components. The kettle may also be provided with a recycle ; line ~ith a heat exc~langer to establish and malntaln the ( I desired temperature. In the heating zone 20, the te~pcra-- ` 5 !~ ture is raised high enough to cause thermal decompositlon .' 1, and decarboxyla~ion of the cupric ben~oate substantially , accordin~ to the reac-tion: ~

2 Cu ~-0-C- ~ ~ Phenyl ~enzoate ~ 2Cu-0~ C02 The heating is conducted substantially in the absence of lG 1' oxygen.
Pref`erably,, the cupric benzoate entering the heat-. ing vessel contains an i~iitial amount of cuprous salt and of co~se, ~his salt is generated as the rcaction proceeds. I
( , The therrnal decompositlon of cuprlc benzoate may be conduc- ¦
¦. ted batchwise in which case the initial reaction mixture is . ¦ a suspension of cupric benzoate which may and usually does ¦ contain some cuprous benzoate dissolved in molten benzoic .
acid. The initia'l amount of such cuprous salt.ranges.from ' to 10 or m~ore parts by weight per part o~ cupric benzoate.
20 li Some benzoic acid anhydride is preferably added , j, to the reaction mixture to improve the reaction yieldalthough I , jl it is not required. This material serves to dehydrate the : ~I mixture if` water is inadvertently formed or added and also .
serves to minimize or prevent the self-dehydration ofbenzoio . 25 !¦ acid to water and benzoic acid anhydride by shifting the '' ~ C'. ' ~ _9_. , " ' -.

~ :

li 3 i, equilibriuM. Eventually, ~Ja~er can be removed also by azeotropic distillation with the hydrocarbon added during the preceding process step 10.
" The reaction may be conduc~e~ continuously, in j, which case the reaction mixture may cornprise a solution of , cuprous benzoate in benzoic acid. Thus, it may have the com-Il position Or the product mixture flowing out o~ the reactor ¦, through line 7 and suitable stirrers are provided to stir ~ the mixture.
, The temperature of the heating zone liquld is high ¦' enough to cause the decomposition of the cupric benzoate but, , preferably the temperature is lo~ enough to keep at least the major part of the reactants and products in liquid Phase, ji i.e. dissolved in liquid benzoic acid. A suitable tempera-!
I 15 i ture range is 180 to 250C, preferably in the ran~e of 210-220C. Gas escaping from the heating zone through line 6 is substantially carbon dioxide, from which the organic ¦ material ls substracted to the reactor by gas saturation may be conveniently refluxed to the reaction zone by adequate cooling. Product is withdra~m through line 7 has the I l approximate composition ' benzoic acid650.4 parts il ouprous benzoate 449.2 "
' cupric benzoate 74.3 "
25 ! phenyl benzoate 210.6 ~l magnesium benzoate 92.1 "
j tarry by-products 10.0 "
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. ; 11 . .
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The time of heatl.ng generally is long enough to ¦ eonvert at least hal~ of the cuprie berlzoate and o~ten, thisj eon~ersion is incomplete as in the typical example describ~d above. The substanti.al absence Or ~later in the reaction mix-,, ture during the heating or decomposltlon of cupric benzoate I I improves the overall yield and thi.s may be achieved by addi.-tion Or benzoie acid anhydride as 5 to 10~ ofthe total benzoie aeicl or by adding a hydrocarbon eapable of azeotropic ll water withdrawal. While the principal produet is phenyl !~ benzoate, a small amount of benzoyl salicylate may be present ¦~ as an intermediate product of the overall decomQosition. ¦
¦l . The reactlon mixtùre from reactor 20 is eondueted ¦I through llne 7 to an hydrolysis zone where it is mixed With ¦l water and hydrolyæed under pressure to produee phenol and 11 - . .
I benzoie aeid and to transform the metal salts into their metal o~ides Which remain in suspension into the liquid phase.
I I The phenol-benzoie aeid-water mixture is for~arded to a . filter to separate the solid oxides from the liquid phase.
: Typieally, the slurry fed to the filtration zone 40 may have the eomposition: ..
¦ metal oxides 208.1 parts benzoie acid 1223.1 ~' phenol 100.0 ~ .
¦ water 500.0 7~
25 1l although water could be in smaller or large amounts.
The filtrate stream 9 is deli~ered to a final ,l fraetionation zone 50. This is one or more fraetionation . . 1~
,', C.' 1i -11- , ' .' ' , 11 , ' . .
1' 11 ' ' reflux columns where water and phenol are di.stilled orf , thereof and an intermediate liquld benzoic acid fraction is ,~ taken from a central zone and a bottoM rraction. These - fractlons typical.ly comprises:

~' Top or Product Fraction phenol 100 parts tl.O64 mole benzoic acid trace water trace Il Intermediate Fraction 1' benzoic acid 1100 parts . phenol. trace This intermediate fraction is recycled through line 11 to the Metal Benzoate Formation Zone 10 as described above. .

. 1, Bottom Fraction ll benzoic acid 4 parts ¦. tars 10 "
.It will be observed from the above that a number ¦l of features are involved in the practice oP this invention.
¦, Thus, the oxidation to cupric benzoate, the.heating of the 1l cupric benzoate to form phenyl benzoate and the hydrolysis ,I to evolve phenol are conducted as separate operations. The .. ¦I heating and decomposition to produce phenyl benzoate is con- .
, ducted preferably in the substantial absence of oxygen and ¦~ water. If some oxygen is introduced to partially regenerate ¦, cupric benzoate Prom the resulting cuProus benzoate, this ¦ reaction generates water which hydrolyzes phenyl benzoate -12- .
!l -, 11 ...
Il . . . .
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9'~

i to phenol and promotes tar formation, apparcntly through ' polymerization of phenolic. groups i In the oxidation process, the temperature is held lo~ cnough to avoid production of a substantial amourlt of . .
' aromatic ester i.e. phcnyl benzoate during the oxidation and this oxldation is primarily oonducted to convert cuprous benzoate to cupric benzoate. In this step :the cupric benzoate concentration is substantially increased and 'l the cuprous ll benzoate and oxide cbncentration is substantially I reduced.~ While complete conversion of the cuprous to cupric state is not necessary, it is preferred to convert at least ~
!~ 5% and preferably at least 70 to 90% of the incominG cuprous ¦I compou~ds to the cupric state and to avoid production Or ¦I detectable quantities of aromatic ester such as phcnyl ben-zoate.
I In vie~ of the above, the o~idation temperature ¦ rarely exceeds 220C, and preferably does not exceed about 170C. Furthermore, it is often desirable -to convert only l¦l a part of the cuprous materlal as this ensures the presence ¦l Or cuprous benzoate substantially throughou-t the heating or I! decomposition process. The oxidation is conducted in the 1 presence of benzoic acid to ensure the production of cupric ¦¦ benzoate.
! In the heating step, the temperature of the heated ¦ mass is held low enou~h to maintain evolved phenyI benzoate in theliquid phase rather than to vaporize It from the benzoil .
I acid solution as in older processes.
~., I ' .

:

~. Whereas prior processes used coppcr in small or '. catalytic amounts rarely in excess of' 5% by ~ieight or- 10% on the molar basis based upon the reaction mixture of benYoic and plus copper benzoate plus benzoic acid anhydride, much ~ 5 1! larger amounts Or copper benz.oates are present in the reac-I~ tion mixtures of the present i.nvention. Thus, the mlxture Il fed to oxidizer 10 through line 2 contains about 1.22 mols of cuprous copper, 0.24 ~ols o.~ cupric copper an~ 9.99 mols Ij of benzoic acid, the'total copper being 1.46 mols. Because j lQ I of the benæoic acid fed to 10 through line 1, the total ¦, benzoic acid fed is 11.17 moles. Accordingly, on a molar .¦
¦' basis, the ratlo R=(total benzoic moles)~Cu atoms) is 7.~5, ¦ although departure from this value is possible as seen in Example 1 (R=3.59) or Example 3 (R=3.83). This means that 15 ¦i on a mo~.ar basis, the % of copper upon the benzoic acid is i¦ in the range o~ 13 to 27%. I~hile some departure ~rom these ¦¦ values occurs, it.is rare that said percentage is below 10%
. or above 50%, and generally this ratio is within 15 to'30 in both the oxidation and heàting steps.
¦ While the process may be conducted in a series of ¦ reactors or columns, it is also possible to perform it in a ¦I single reactor by first oxidizing cuprous.material;wi~h ~, oxygen, then discontinuing feed of oxygen and rai.~ing the ¦1 temperature of the reaction mass in the reactor while exclud 1 25 ll ing oxygen to achieve the desired production of phenyl benzoate. Instead of heating cupric benzoate in the presence of benzoic acid anhydride, other means may be resorted to in .' C:
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order to remove and exclude ~la~er from the heclted rnass and thereby to reduce -the presence of water therein and the . tendency to produce phenolic polymers and/or condensation products.
. According to a further embodiment, the process may be performed to produce benzoyl salicyllc acid with or With-I out phenyl benzoate. This salicycli c acid is an intermedicLtc ~i product o~ Cupric benzoate conversion to phenyl benzoate.
~ Its ~ormation tends to be promoted if magnesium benzoate or 1. other alkaline earth benæoates are not present in adequate catalytic amount. In the total absence of Mg and while maintaining all other conditions the same~ the mole ratio of benzoyl salicylic acid to phenyl benzoate can be of the Ii order of 25%. Substantlally complete conversion of benzoyl.
-~ i5 I salicyi~icaci.d.to ~henylben30.-ltP iS achieved With heatlng times ¦1 in excess of 3-4 hours.
ll While the invention has been described with ¦¦ particu].ar reference to Copper benzoates, it may also be ! applied in the same molecular proportions to benzoates O~
I other metals which have two or more valent states. ThuS
¦~- molybdenum benzoates may be decomposed to produce phenyl benzo- .
. ¦ ate and a benzoate of molybdenum in a lower valent state.
.. l Use o~ molybdenum has some merits with ~he known benzoic acid-to-phenol.processes, where it increases the selectivity l with respect.to copper ~La Chimica e l'Industria, Vol. 50, i 1086~ (1968)] while significantly decreasing the reactlon ¦¦ zone.

., ~
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In the ~oLlowing examples there are described several preferred embodiments to illustrate the invention.
However, lt is to be understood that the invention 1s not intended to be llmlted to the specific embodiments.

1I EXA~IPL~: 1 A vertically aligrled glass flaslc with a volume o~
i! about one cublc decimeter was provided with a heating jacket, a stirrer and an outlet tube in the upper part thereof. A
Il valved sampling tube extended from the bottom and an inlet i tube also was provided in the top of the reactor. The outlet i, was connected to a reflux condenser to return evaporated i benzoic acid and the reflu~ condenscr exited through a ¦ silica gel trap, a trap ~or benzolc acid, a barium hydroxide trap and a sodium carbonàte-lirne trap.
I 27~5 g Or a mixture of 32.18~ o~ cupric ben~,o-ate, 65.64% o~ benzolc acid and 2.18% o~ benzoic acld anhy-I dride was introduced lnto the reactor and the reflux con-.~ ¦ denser was held at about 120C. Nltrogen was ~ed lnto the - ¦¦ reactor to provide a nitrogen atmosphere over the reaction l'' mixture and the temperature of the mixture was held at 215 ~,l to 220C for about one hour. Xn a series of samples, the i amount of cuprlc benzoate converted to cuprous benzoate ran-ged from 10 to 80~ o~ the initial cupric benzoate. The i resulting llquid reaction mixture contained benzoyl salicylic 111 acid and phenyl benzoate in approximately 100~ yield based upon the amount Or cupric benzoate decomposed to cuprous benzoate.

'' I
i ~ . .

9~g .' . ~.
, The process of Example 1 ~iasrePeated except that '~ c ~, 0.8 g , of magnesium benzoate ~as added to the mixture introduced to the reactor. The temperature Or the mixture 1 was maintained at about 215 to 225C for abou~ one hour and yleld of 98 to 99% of pheny~ benzoate (based upon initial cupric benzoate) ~ras obtained and carbon dioxide in the pro-¦
portion of one mole per mole of phenyl benzoate formed was ~~ evolved. ¦' ' , EXAMPLE 3 Into the reactor of Example 1 were introduced 1 i'' 46.4 g_ of cupric benzoate, 5.8 g o~ magnesium benzo-j ¦~ ate, 52.4 g of, benzoic acid~and 58 e of xylene and j, a second conaen~ser was put in series to the one described ¦~ in ~xample l to reflux back xylene to the reaction mixture.
This second condenser was maintained at 80C and the tempera _ ture of the'mixture'was held at about 210 to 220C and the mixture ~as stirred. After about one ho~lr, the mole ratio ¦, of cupric benzoate to cuprous benzoate is about 0.7 and the ,' yield of phenyl benzoate based upon cupric benzoate con-- i verted was 99-100~ with stoichiometric evolution of carbon , ~ j dloxide. No appreciate by-products are found.
,' ' 1'1 .. j!
. jl .

~ ' i C 11 ' -17- ' , . , ~

:il3 ~
, .
EX_~PLE 4 The reaction mass obtained by Exampl~ 2 was placed , in a rocker-bomb autoclave wit~l-the addition of 20% by ` ~ I weight of water. The autoclave was sealed and hcated-up to .' 5 '` 220C at a corresponding equillbrium pressure of about 2? kg/cm~ After t~o hours a~ 210-230C, the autocla.ve ~Jas allo~ed to cool do~ln by internal coil refrigeratlon and product analysis demonstrated a practically complete con-version of the initial phenyl benzoate to phenol and benzoic ~ acid while copper and magnesium were essent;ally present in 1~ ~orm o~ the starting oxides.

i` . EXAMPLE 5 jl I
A mixture of 109.26 g Or cuprous oxide, 12.]4 g ofj cupric oxide, 8.66 g Or magnesium hydroxide containini, 6.5 ~i iil o~ moisture was iiiss,:~lved in 783.3 g o- melted ben~oic acid, and tlle, j !¦ mixture was held at 1350C in a jacketed reactor provlded ¦I with a reElux condenser as in Examp:le 3 and with an opera-ting pressure control valve. To this mass, 785 g of toluene were added under agitation. From the reactor I 20 ',, bottom, an air flow o~ 700 Nlt/h was in-troduced. After i l~ 15 minu-tes, the mass assumed a dark blue color and after , ,, cooling the reactor, the whole mass was analyzed to determin~
! i the ratio of Cu and Cul . This determination showed that li the copper oxidation Nas co~plete so that the metal was in ¦ the Eorm oE cuPriC benzoate.
1'i ,.
C ' 11 - 1 8 - `
1i .
' .' Il, ' ` .

, E~lU/lE'IE 6 The experln~nt of Exarl21e 5wasrepQated~ but at the end of I
the o~cidation proceeis, the mass was cL,}cldually heated to the temperatur~e ¦
of 215C. ALter about onr hour of rrQintain:ing the m~lss clt this terrlpera ,, i;ur*, part ot' the mass ~LS drawrl and analyzed. It l~las a transparent ancl hono"~neous licluid containlncr 5~: by ~r~ t; of toluelle ~Ihile the 'j conversion of cupric benzoate into cuprous benzocLte ~ras 85%. Corres-1' pondingly the phenyl benzoate forr.~:d was Ipp~o:~irr~tely 93.5% mole w:Lth ~. reg~-Lrds to the transformed cupric benzoate. r~ne terminal mass aspect ~ den~nstrated no color bodies forrration.
i, , I
E~APIPLE 7 j', i A port.ion of the mass obtained in Example 6 was subjected I, to hydrolysis in a reactor wherein 93.02 g of the said rl!ass ar~d 20.ol~ g ¦, of ~.ater were placed. r~he nLixture ~ras heated ln 15 nLlnutes at 220C
1¦ at autorrenous pressure and the rDass was held at this ternperature and !i pressure for 45 rninutes. men, the mass was cooled and depressurized ¦¦ and analysis sho~red that phenyl benzoate had transl`or~ned completely i~ into phenol and benzoic acid. At the sarne ti~.e, it l,ras possible to see the forrnation of a phase ~"hich ren~:Lined solid ¦; up to 100C. miS solld n iss ~hich was about 20% in volume of the total~
rrQss ~ras essentially cornprised of copper and n~onesi~ oxides.
/arious rnodifications of the process rnay be n~ade ~lthout il departing rrom khe spirit or scope thereof and it should be understood li that the invention is intended to be limited only as defined in the appe~d~d cla~ms.

~l -19-lli .

. . . -- -- .

Claims (27)

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

    l. A method of preparing phenyl benzoate comprising oxidizing a lower valent salt of a member of the group consisting of cuprous benzoate and molybdenum benzoate to the corresponding benzoate of said metal in higher valent state with elemental oxygen at a temperature low enough to avoid sub-stantial phenyl benzoate formation and thereafter separately heating the oxidized benzoate at a higher temperature sufficient to produce -the phenyl benzoate and regenerate the lower valent salt, said latter heating being conducted in the substantial absence of oxygen.
  2. 2. The method of claim l wherein the lower valent salt is oxidized in the presence of benzoic acid,
  3. 3. The method of claim l wherein the oxidized salt is heated in the presence of benzoic acid.
  4. 4. The method of claim l wherein the salt is only partially oxidized whereby the lower valent salt is present throughout the heating.
  5. 5. The method of claim l wherein the heating is conducted in the sub-stantial absence of water.
  6. 6. The method of claim l wherein the heating is conducted in liquid phase in the presence of an alkaline earth metal benzoate.
  7. 7. The method of claim l wherein the heating is discontinued before all of the oxidized salt is consumed.
  8. 8. The method of claim l wherein the lower valent salt is cuprous benzoate
  9. 9. A process for the production of phenyl benzoate comprising the separate steps of reacting benzoic acid with cupric oxide and/or cuprous oxide and oxygen to form a mixture containing cupric benzoate or with molybdenum oxide to form a mixture containing molybdenum dibenzoate at a temperature of 100 to 200°C and decarboxylating the latter bv heating at a temperature of 190 to 250°C in the substantial absence of oxygen to a mixture of phenyl benzoate and cuprous benzoate or molybdenum benzoate and optionally recovering phenyl benzoate from the mixture, the water of reaction being substantially eliminated in all process; steps.
  10. 10. The process of claim 9 wherein benzoic acid is reacted with cupric oxide and/or cuprous oxide and oxygen at a temperature of 120 to 170°C.
  11. 11. The process of claim 9 wherein the water of reaction is removed by azeotropic distillation with a hydrocarbon.
  12. 12. The process of claim 9 wherein up to 15% by weight of the metal oxide is replaced with alkaline earth metal oxide.
  13. 13. The process of claim 9 wherein the decarboxylation step is effected at a temperature of 190 to 220°C.
  14. 14. The process of claim 9 wherein the decarboxylation step is effected in the presence of a dehydrating agent.
  15. 15. The process of claim 14 wherein the dehydrating agent is benzoic acid anhydride.
  16. 16. The process of claim 12 wherein the alkaline earth metal oxide is magnesium oxide.
  17. 17. In a process of phenol production comprising (a) oxidizing benzoic acid with an oxide of copper or molybdenum in the presence of excess benzoic acid at a temperature from 100 to 200°C to form the corresponding metal dibenzoate, (b) heating the said dibenzoate at a temperature of 190 to 250°C
    to decarboxylate the same and form phenyl benzoate (c) hydrolyzing the phenyl benzoate with water to form a benzoic acid and phenol mixture and (d) recovering phenol from the said mixture, the improvement comprising performing the said steps separately, conducting the decarboxylation step in the absence of oxygen and the water of reaction being substantially eliminated in steps (a) and (b).
  18. 18. The process of claim 17 wherein the benzoic acid is reacted with cupric oxide at temperature of 120 to 170°C.
  19. 19. The process of claim 17 wherein the water of reaction is removed by azeotropic distillation with a hydrocarbon.
  20. 20. The process of claim 17 wherein up to 15% by weight of the metal oxide is replaced with alkaline earth metal oxide.
  21. 21. The process of claim 17 wherein the temperature is 190 to 220°C.
  22. 22. The process of claim 17 wherein the decarboxylation step is effected in the presence of a dehydrating agent.
  23. 23. The process of claim 22 wherein the dehydrating agent is benzoic acid anhydride.
  24. 24. The process of claim 20 wherein the alkaline earth metal oxide is magnesium oxide.
  25. 25. The method of claim 17 wherein the decarboxylation temperature is approximately 220°C.
  26. 26. The process of claim 17 wherein the hydrolysis product is filtered to remove metal oxides which are recycled to the benzoate formation step.
  27. 27. The process of claim 17 wherein the hydrolysis product is distilled to recover phenol and the remainder is recycled to the benzoate formation step.
CA000307902A 1977-07-22 1978-07-21 Phenol production Expired CA1120949A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH9158/77 1977-07-22
CH915877A CH632478A5 (en) 1977-07-22 1977-07-22 PROCEDURE FOR THE PREPARATION OF PHENOL FROM BENZOIC ACID.

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BE (1) BE868779A (en)
CA (1) CA1120949A (en)
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DE (1) DE2832192A1 (en)
ES (1) ES471940A1 (en)
FR (1) FR2398043A1 (en)
GB (1) GB2001317B (en)
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JPS6187646A (en) * 1984-10-08 1986-05-06 Sagami Chem Res Center Fluorine-substituted phenyl benzoate and preparation thereof
NL8903098A (en) * 1989-12-19 1991-07-16 Stamicarbon PROCESS FOR PREPARING A PHENOL.

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GB2001317B (en) 1982-05-26
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ZA784156B (en) 1979-07-25
FR2398043A1 (en) 1979-02-16
SE7807919L (en) 1979-01-23
AU528850B2 (en) 1983-05-19
ES471940A1 (en) 1979-10-01
IT1097832B (en) 1985-08-31
JPS5439039A (en) 1979-03-24
CH632478A5 (en) 1982-10-15
BE868779A (en) 1978-11-03
FR2398043B1 (en) 1984-07-13
NL7807199A (en) 1979-01-24

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