LYTIC SYSTEMS
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POLIMERI EUROPA S.p.A.
Via Enrico Permi 4 - BRINDISI
POLITECNICO DI MILANO - DIPARTIMENTO DI CHIMICA, MATERIA- LI E INGEGNERIA CHIMICA "GIULIO NATTA" Piazza Leonardo da Vinci 32 - MILAN
****** stamp Of the CHAMESR OF COMMERCE OF MILAN - PATENT DEPT.
SEPT. 28, 2006
DESCRIPTION
The present invention relates to a process for the preparation of phenol by the aerobic oxidation of cumene which is based on the use of a new catalytic system.
More specifically, the invention relates to a process for the preparation of phenol by the aerobic oxidation of cumene and subsequent acid decomposition of hydroperoxide to phenol and acetone, carried out in the presence of new catalytic systeras, under extremely mild conditions and with high conversions and selectivities.
The Hock process for the production of phenol, com- monly used by the chemical industry, is based on the auto- oxidation of cumene to hydroperoxide, which is then decora- posed by means of acid catalysis to phenol and acetone (H. Hock, S. Lang, Ber. 1944, 77, 257; W. Jordan, H. Van Bar- meveld, O. Gerlich, M, K. Baymann, S. Ulrich, Ullman's En- cyclopedia of Industrial Organic Chemicals, Vol. A 9, Wiley-VCH, Weinheim, 1985, 299).
oxidation phase which is characterized by a classical radi- cal chain process in which the hydroperoxide fcrmed acts in turn as initiator of the radical chain. The selectivity in the formation of the hydroperoxide decreases to the extent in which the hydroperoxide itself acts as initiator as its decomposition produces acetophenone, which is the main by- product at relatively high temperatures, and cumyl alcohol. The decomposition of the hydroperoxide, on the other hand, increases with the conversion (the greater the conversion and therefore the concentration of hydroperoxide, the higher the decomposition will be) and with the temperature. The lower the conversion and temperature, the higher the formation selectivity of hydroperoxide will be.
Another important aspect is the necessity, for indus- trial processes, of operating in an alkaline environment in Order to neutralizs the carboxylic acids, essentially for- mic acid, which are formed during the oxidation and which catalyze the decomposition of the hydroperoxide to phenol which is an auto-oxidation process Inhibitor.
At temperatures lower than 100°C, the non-catalyzed oxidation of cumene is too slow; upon increasing the tem¬perature, the conversion increases, but the selectivity de¬creases. In any case, the conversion of cumene cannot be high as the consequent selectivity is considerably jeopard-

Under inaustrial conditions for the non-cat:alyzec oxidation of cumene, a co."promise between temperature, con- version and selectivity has always been sought.
The use of metallic salts (Co, Mn) as catalysts con- siderably increases the aerobic oxidation rate of the cu- mene and allows lower temperatures to be used, but it also significantly reduces the selectivity as these metallic salts accelerate the decomposition of the hydroperoxide.
This type of catalysis does not seem particularly suitable for the production of cumene hydroperoxide by means of aerobic oxidation (F. Minisci, F. Recupero, A. Cecchetto, C. Gambarotti, C. Punta, R. Paganelli Org. Proc. Res. Devel. 2004, 163).
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A different approach concerns the use as catalysts of N-hydroxyphthalimide both in association with cumene hy-
ercxide (R. A. Sheldon, I.W.E. Arends Adv. Svnth.
Catal. 2001, 343, 1051) and with traditional radical Ini¬tiators, such as azoisobutyronitrile (0. Fueuda, S. Sakagu- chi, Y. Ishii Adv. Synth. Catal. 2001, 343, 809).
Also in these cases, temperatures ranging from 75°C to 100°C are used; either the conversions or the selectivities are not high; moreover the N-hydroxyphthalimide is decom- posed during the oxidation. At lower temperatures, these Initiators are not effective. It is not possible in these
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oxidation temperature, partiaily deccmpose "he curo.ene hy- droperoxide to phenol, inhibiting the auto-oxidaticn proc- ess itself.
A catalytic system has now been found, which allows the aerobic oxidation of cumene to be carried out under particularly mild temperature and pressure conditions. Fur- thermore, this catalytic system allows high conversions to be obtained, associated with high selectivities, unlike the industrial processes currently in use, in which the selec¬tivities decrease with an increase in the conversions.
An object of the present invention therefore relates to a process for the preparation of cumene hydroperoxide characterized in that cumene is reacted with oxygen in the presence of a catalytic system comprising an N-hydroxyimide or an N-hydroxysulfonamide having general formula I and II,
CO SO2
r" \ R/ N—OH N-OH
R / R /
I \ / \ y "
CO CO
wherein R is an alkyl, aryl group or is part of aliphatic and aromatic cyclic systems, associated with a peracid or dioxirane, at a temperature < 100°C.
The N-hydroxyimide or N-hydroxysulfonamide is prefera- bly selected from the group consisting of N-
hydroxysaccharine.
N-hydroxyphthalimide and N-hydroxysuccinimide particular industrial interest, as they are easily accessi- ble from low-cost industrial producta such as phthalic or succinic anhydride.
A further object of the present invention relates to a process for the preparation of phenol which comprises the preparation of cumene hydroperoxide as previously described and the subsequent acid decomposition of the hydroperoxide to phenol and acetone.
In any case, the N-hydroxy-derivatives are not decom- posed due to the particularly mild conditi ons of the oxida— tion process and can be recovered and recycled, contrary to what occurs when the same derivatives are used at higher temperatures.
The pcracids sr.d dioxiranes can be either aliDharic or aromatic commercial products, such as peracetic or m- chloroperbenzoic acid, whereas the dioxiranes are prepared starting from ketones and potassium monopersulfate (A. Bravo, F. Fontana, G. Fronza, F. Minisci J. Org. Chem. 1998, 53, 254).
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Instead of peracids or dioxiranes, precursors such as aldehydes for the peracids and a mixture of ketones and potassium monopersulfate for the dioxiranes, can be used

The U3e of aldehydesr such as acetaldehyde er benzai- dehyde, is particularly ccnvenient, as, under the reaction conditions, they are slowly oxidized to peracids by oxygen, and do not require further oxidizing agents, as in the case of dioxiranes.
This relatively slow oxidation prccess of aldehvdes is useful as, given the same conditions, the conversions of cumene increase maintaining low stationary concentrations of peracid.
An analogous result can be obtained by slowly adding the peracid or dioxirane to the reaction mixture as the peracids and dioxiranes are decomposed during the oxidation to cumene, maintaining their stationary concentrations low, whereas the N-hydroxy-derivatives remain unaltered and can be recycled.
In crdsr to trioger the oxidation of aldehvdes anc re— duce the induction period, it is also possible to use a very small quantity of peracid.
The oxidation can be carried out with cumene in a So¬lution of solvents such as acetonitrile, acetone, di- methylcarbonate or ethylacetate, which do not easily form explosive mixtures with oxygen under mild conditions; the latter also allow the use of acetic acid as solvent, with which it is even more difficult to form explosive mixtures acid dces not catalyze the decomposition of hydroperoxide to phenol. In all the other processes described and men- tioned above, the acetic acid inhibits the oxidation proc- ess and cannot be used as solvent. It is also possible to operate without solvents, but in this case an N-hydroxy- derivative must be used, which is soluble in cumens as the simplest chain-ends (N-hydroxysuccinimide, N-
hydroxyphthalimide, N-hydroxysaccharine) are not very solu¬ble. The solubility of the N-hydroxy-derivative in cumene is increased by introducing sufficiently long alkyl chains (Cs-Cid into the N-hydroxy-derivative itself.
The hydroperoxide Solution is decomposed to phenol or acetone by means of homogeneous or heterogeneous catalysis; the latter, obtained by the use of acid polymers such as AjTtberlyst 15 or Nafion, is particularly advantageous for the Isolation of the phenol and recycling of the catalyst after Separation.
The oxidation is carried out at temperatures lower than 100°C and preferably at atmospheric pressure. It is preferably carried out at temperatures ranging from 20°C to 70°C.
Quantities of N-hydroxy-derivatives, peracids or di- oxiranes ranging from 1 to 10% with respect to the cumene, are preferably used; when the N-hydroxy-derivative is asso- bly ranges froir. 1% T:O 20% with respect to uhe cumens.
An important discovery is that neither N-hydroxy- derivatives, nor peracids, or dioxiranes or their precur- sors alone have catalytic activities in the aerobic oxida- tion of cumene under the particularly mild operating condi- tions used; i.e. a significant oxidation does not take place using an N-hydroxy-derivative or peracid or dioxirane or one of their precursors alone as catalysts.
Under the operating conditions adopted, cumene hy- droperoxide or other hydroperoxides, such as azoisobuty- ronitrile or benzoylperoxide, in association with N- hydroxy-derivatives, are completely inert and have no Ini¬tiation activity of aerobic oxidation processes of cumene. This is contrary to the industrial oxidation processes cur- rently adopted in which, operating at high temperatures, the Initiation of the oxvgenation process occurs by the thermal decomposition of the cumene hydroperoxide, which therefore reduces the process selectivity as the conversion and consequently the concentration of hydroperoxide in- crease.
This explains the possibility of obtaining, under mild temperature conditions, high conversions associated with high selectivities by means of the new catalytic systems discovered with this invention.
of peracids and dioxiranes v/hich are stabie az. uhe reaciiion temperatures without N-hydroxy-derivates and consequently do not initiate oxidation processes by means of thermal de- composition, with respect to the use of Initiators such as cumene hydroperoxide or azoisobutyronitrile used formerly, which are inert at a low temperature and must be brought to decomposition temperatures to be able to initiate and rr-ain- tain the oxidation process of cumene.
With the catalysts of this invention, the Initiation and maintenance of the oxidation process of cumene occur as a result of the reaction, even at low temperatures, between N-hydroxy-derivatives and peracids or dioxiranes, which are separately stable under these conditions.
The following examples are provided for illustrative purposes but in no way limit the process object of the pre- sent invention. EXAMPLE 1
A Solution of 2.5 mmoles of m-chloroperbenzoic acid in 10 mL of acetonitrile is added dropwise under stirring to a Solution of 50 mmoles of cumene and 5 mmoles of N- hydroxyphthalimide in 100 mL of acetonitrile, in an oxygen atmosphere, at atmospheric pressure, at 20°C over a period of 12 hours. HPLC analysis of the reaction mixture shows a conversion of cumene of 91% with a yield of cumyl- ■che N-hydrcxyphnhaliinide remains substant ially unaltered. The reaction mixture is treated with a 0.3 M Solution of H2SO4 in acetonitrile (5 mL) for 2 hours at room terripera- ture, obtaining phenol with a yield of 92% with respect to the cumene converted. EXAMPLE 2
The same procedure is effected as in Example 1 without m-chloroperbenzoic acid. There is no significant oxidation. EXAMPLE 3
The same procedure is effected as in Example 1 without N-hydroxyphthalimide; the conversion of cumene is 1% with the formation of traces of cumyl alcohol. EXAMPLE 4
The same procedure is effected as in Example 1 in which all the m-chloroperbenzoic acid was added to the re¬action mixture at the beginning. The cumene conversion is 70% with a yield to cumyl-hydroperoxide of 88% based on the cumene converted. The acid decomposition as in Example 1 leads to the formation of phenol with a yield of 84% with respect to the cumene converted.
EXAMPLE 5
A Solution of 50 mmoles of cumene, 5 mmoles of N- hydroxyphthalimide and 5 mmoles of acetaldehyde in 100 mL of acetonitrile is stirred at 20°C for 24 hours in an oxy- a corjversion Ci cumere er 6S% with a yield to cumyl — hydroperoxide of 94% based on the cumene converted. 2 g of Amberlyst 15 are added to the Solution and the mixture stirred at room temperature for 1 hour, leading to the for- mation of phenol with yields of 91% with respect to the cu¬mene converted. The Ainberlyst, insoluble in the reaction environment was separated and reused without loosing its catalytic activity. EXAMPLE 6
The same procedure is effected as in Example 5 without N-hydroxyphthalimide; there is no significant reaction. EXAMPLE 7
The same procedure is effected as in Example 5 without acetaldehyde; there is no significant reaction. EXAMPLE 8
The same procedure is effected as in Example 5 adding 0.1 mmoles of m-chloroperbenzoic acid during the reaction. The cumene conversion is 77% with a 93% yield to hydroper¬oxide based on the cumene converted and 89% to phenol after acid catalysis based on the cumene converted. EXAMPLE 9
The same procedure is effected as in Example 8 using benzaldehyde in the place of acetaldehyde. The cumene con¬version is 59% with a 97% yield to hydroperoxide based on
eroxide leads ro a yield or 92% to phenol based mene converted. EXAMPLE 10
The same procedure is effected as in Example 8 using acetone as solvent instead of acetonitrile. The cumene con- version is 39% with a yield to hydroperoxide and phenol of 97% and 92% respectively based on the cumene converted. EXAMPLE 11
A Solution of 5 mmoles of dimethyldioxirane in 10 mL of acetone is added dropwise under stirring to a Solution of 50 mmoles of cumene and 2.5 mmoles of N- hydroxyphthalimide in 100 mL of acetone, at 20°C, in an oxygen atmosphere, at atmospheric pressure, over a period of 12 hours . The conversion of cumene is 45% with a yield to hydroperoxide of 97% based on the cumene converted. De- composition by means of heterogeneous catalysis as in exam¬ple 5 leads to a yield to phenol of 93% with respect to the cumene converted. EXAMPLE 12
The same procedure is effected as in Example 11 with- out N-hydroxyphthalimide; a conversion of 4% of cumene in cumyl alcohol is obtained. EXAMPLE 13
A Solution of m-chloroperbenzoic acid (5 mmoles) in 10
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mmoles) in 100 mL of acetic acid, over a period of 15 hours, under oxygen, at atmospheric pressure and 25°C. Af¬ter decomposition with Amberlyst 15 according to Example 5, a cumene conversion of 62% is obtained with a yield of 89% to phenol with respect to the cumene converted. EXAMPLE 14
0.5 mmoles of m-chloroperbenzoic acid are added drop- wise at 50°C, over a period of 24 hours, to a Solution of 5 mmoles of cumene, 0.5 mmoles of N-hydroxysuccinimide in 10 mL of acetonitrile, in an oxygen atmosphere at ordinary pressure. A conversion of 45% is obtained with a yield to phenol of 88% with respect to the cumene converted.
1 . A prccess for rhe preparation or cumene nyaroperoxiae characterized in that cumene is reacted with oxygen in the presence of a catalytic system comprising an N-hydroxyimide or an N-hydroxysulfonamide having general formula I and II,
CO SO2
r" \ R/ N—OH N-OH
R / R
' ^CO ' CO'
wherein R is an alkyl, aryl group or is part of aliphatic and aromatic cyclic systems, associated with a peracid or dioxirane, at a temperature < 100°C.
2. The process according to claim 1, wherein the N- hydroxyimide or N-hydroxysulfonamide is selected from the group consisting of N-hydroxysuccinimide, N- hydroxyphthalimide, N-hydroxysaccharine.
3. The process according to claim 1, wherein the reaction is carried out at temperatures ranging from 20°C to 70°C.
4. The process according to claim 1, wherein the reaction is carried out at atmospheric pressure.
5. The process according to claim 1, wherein the peracid is selected from aliphatic or aromatic peracids.
6. The process according to claim 5, wherein the peracid is selected from peracetic acid or m-chloroperbenzoic acid.
aiipnaLxC or arOi!ia.i.ic aj-dehy-cis is useci in ^hc ^^ac^ ^^ peracid, which under the reaction conditions acus as pre- cursor of the peracid.
8. The process according to claim 7, wherein the aldehyde is selected from acetaldehyde or benzaldehyde.
9. The process according to claim 1, wherein the di- oxirane is selected from aromatic or aliphatic dioxiranes .
10. The process according to claim 1 and 9, wherein a ke- tone and potassium monopersulfate are used in the place of the dioxirane, which under the reaction conditions act as precursor of the dioxirane.
11. The process according to claim 1, wherein the peracid or dioxirane are added slowly to the reaction mixture.
12. The process according to claim 1, wherein the reaction is carried out in the presence of a solvent.
13. The process according to claim 1, wherein the quantity of N-hydroxyderivatives, peracids or dioxiranes ranges from 1% to 10% with respect to the cumene.
14. The process according to claim 7, wherein when ühe N- hydroxyderivative is associated with the aldehyde, the quantity of the latter ranges from 1% to 20% with respect to the cumene.
15. A process for the preparation of phenol which com- prises the preparation of cumene hydroperoxide according to
QG CCTTipO S X L i On Oi^ tlHS riVOlT OpS IT OX iGS oO pTiGnO-L SüCI '^CSL-C^iS.
16. The process according co claim 15, wherein the acid decomposition of the hydroperoxide takes pl ace by rneans of heterogeneous acid catalysis in the presence of acid poly- mers selected from Amberlyst 15 or Nafion.
17. The process according to claim 15, wherein the acid decomposition of cumene hydroperoxide takes place by rneans of homogeneous acid catalysis.