CA1146585A

CA1146585A - Co-oxidation of methyl benzenes and benzaldehyde

Info

Publication number: CA1146585A
Application number: CA000337949A
Authority: CA
Inventors: Robert W. Shinn; George Suld; James E. Lyons
Original assignee: Sun Tech Inc
Current assignee: Sun Tech Inc
Priority date: 1978-11-03
Filing date: 1979-10-18
Publication date: 1983-05-17
Also published as: IT7927031A0; GB2035318B; IT1126310B; FR2440930A1; DE2944088A1; GB2035318A; FR2440930B1; NL7908008A

Abstract

ABSTRACT OF THE DISCLOSURE

The oxidation of methyl benzenes, such as toluene, with air or oxygen in the presence of acetic anhydride, or acetic acid and phosphorus pentoxide, and sulfuric acid catalyst to form a phenolic acetate and methylene diacetate may be carried out under mild conditions when small amounts of benzaldehyde are added to the reaction.
The resulting acetates may then be pyrolyzed to yield phenolic compounds and formaldehyde, respectively.

Description

BACKGROUND OF THE I~rJENTION

This inventlon re]ates to novel processes for the oxidation of methyl benzenes. More particularly, this invention relates to an improved process for the oxidation of methyl benzenes with air or oxygen in the presence of a strong acid c atalyst, benzaldehyde, and either acetic anhydride or the combination of acetic acid and phosphorus pentoxide, The products, in each case, are a phenolic acetate and, depending upon the reaction conditions, within methylene diace,tate or formaldehyde (or paraformaldehyde~. lhe pher.olic acetate, and methylene diacetate, when obtained, may then be converted to the resp_ctive phenolic compounds and formalde~yde or para~ormaldehyde by pyrolysis or the like~

Earlier wor~ o~ Gro~hen et al, (Doklady Akad. Nauk, SSSR, 204, No. 4,872~ established that acid catal~zed oxidation of toluene at high temperature and pressure in acetic anhydride followed by saponification of the reaction product gave phenol in modest yeild. ~ore recent work has shown that phenyl acetate, methylene diacetate and acetic acid are the ma~or products o~ the acid catalyzed air oxidation of toluene in acetic anhydride. Despite recent improvements using catalysts initiators and promoters and acetic acid as a solvent this prior wor~ has necessitated high temperatures and pressures to achieve reasonable rates and yields.

SUMMARY OF THE INVENTION

We have now discovered that the acid-catalyzed oxidation of methyl benzenes in acetic anh~dride~ or in ~cetic acid and phospho~us pentoxide to form a phenolic acetate, methylene diacetate, and acetic acid occurs at convenient rates and good yields under mild conditions of temperature and pressure when the reaction is carried out in the presence of small amounts of' benzaldehyde. The reaction proceeds readily at temperatures as low as 80C and oxygen pressure of 1 atmos-phere. The resulting acetates may then be converted to the respective phenolic compounds and formaldehyde or paraformaldehyde by pyrolysis or the like.

DESCRIPTION OF THE INV~NTION
-The process wherein acetic anhydride is employed may be depicted by the following equation, using toluene as an example:

phCH3+2Ac20 + 2- CX3C02H ~ PhOAc + CH2(0Ac~2 ~ HQAc PhCHO
Caro's Acid in which acetic acid is being used solely as a solvent, together with Caro's acid, a promoter for the reaction.

The process wherein the comblnation acetic acid and phosphorus pentoxide may be used in place of acetic acid may be depicted as follows, using toluene:

rCH20 and/o~
PhCX3 + P205 + HOAc + 2 ~ C4 ~ PhOAc + ~ ~ (OAc~

PhCHO + [ P205 XH2 Caro's Acid It will be understood, o~ course, that these methods are equally applicable to other methyl benzenes such as xylenes and trimethyl benzenes, e.g., mesitylene and pseudocumene.

In general, these processes are carried out by oxidizing the desired ~ethyl benzene with air or oxygen in the liquid phase at pressures of at least 1 atmosphere and at temperatures as low as 80C to form equimolar amounts of a phenolic acetake and methylene diacetate, together with acetic acid and lesser amounts of certain methyl-benzene-derived by-products. The phenolic acetate and methylene diacetate, following separation, may then be pyrolyzed to form the corresponding phenolic compound and ~ormaldehyde respectively, while the acetic acid may be routinely converted to acetic anhydride and recycled to the oxidation step.

It will thus be seen that as contrasted with the prior art, this invention is particularly characterized by the surprising discovery that the above-described oxidation can be carried out under very mild reaction conditions by simply addin~ small amounts of benzaldehyde to the reaction.

As a~orementioned, the reactants are methyl benzenes, such as toluene, xylene (ortho, meta, or para3 and trimethyl-benzenes such as mesitylene and pseudocumene, together with acetic anhydride and oxygen or air, in the presence of a strong acid catalyst, preferably H2S04, and, as the novel feature of this invention, benzaldehyde. The weight ratio of methyl benzene to acetic anhydride should desirably be in the range of from about 50:1 to 1:10, and preferably 10:1 to 2:1, while the weight ratio OL H2SOLL to methyl benzene should generally be from about 5 x 10 4 to 1 x 10 , and preferably 1 x 10 3 to 5 x 10-3.

S~35 The amount of benzaldehyde employed is about 0.~1 to 1.0 moles, and preferably 0.05 to 0.10 moles, per mole of methyl benzene.

The amount of benzaldehyde employed is about 0.01 to 1.0 moles, and pre~erably 0.05 to 0.10 moles, per mole of methyl benzene.

When P205 is employed, the amount is about 1:1 to 1:20 moles~ and preferably 1:2 to 1:5 moles, per mole of acetic acid.
If desired, the reactlon may be run in excess methyl benzene reactant as a solvent, or in a suitable organic solvent such as benzene or chlorobenzene.

It has further been found that persul~ate promoters such as sodium persulfate, potassium persulfate, persulfuric acid or Dry Caro's acid are particularly effective promoters for this oxidation reaction. These promoters are desirably used in amounts of from about 10 3 to 10 gm per gram of methyl benzene.

The reaction, which employs oxygen or equivalent amounts of air, can, and should, as aforestated, be carried out under relatively ~ild conditions, i.e. 3 at temperatures of at least 80C, up to about 150C, and most desirably at about 90-120C, and at air or 2 pressures of at least 1 atmosphere, up to about 10 atmospheres, with the lower ranges of both pressure and temperatures being preferred.

The reaction product containing the phenolic acetate and methylene diacetate, as well as a^~t c acid, ~nd lesser amolmts of ~ethyl benzene derived by-products, and the like is then routinely treated to remove the acid catalyst~ following which the two acetate ?roducts may be separated by distillation under vacuum.

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The recovered phenolic acetate is then converted to phenol, cresol or the like by pyrolysis. This is conventionally achieved by heating the acetate at temperatures of from about 500 to 1000C, preferably at about 625C, and preferably in the presence of a catalyst such as triethyl phosphate and recovering the desired product by routine means.

In a like manner, the pyrolysis of methylene diacetate yields formaldehyde and acetic anhydride. This pyrolysis is conventionally carried out in one step in a homogeneous gas phase reaction, at about 450-550C under reduced pressure.

Any acetic acid recovered from the oxidation of the alkyl benzene may ~hen be converted to acetic anhydride for recycling to the initial oxidation step. This may readily be achieved e.g. by contacting ketene with acetic acid at room temperature in the liquid phase.

In a further embodiment of this invention, it has been found that when acetic anhydride is used, as in the first of the above two reaction schemes, quite surprisingly parafor-maldehyde, together with a phenolic acetate, may be formed directly, and under mild conditions, by the oxidation of methyl benzenes in the presence of acetic anhydride, benzaldehyde, and an acid catalyst when (1) the ratio of acetic anhydride to methyl benzene is controlled in such a fashion as to induce the selective formation of for~aldehyde and the phenolic acetate, to the exclusion of methylene diacetate ~ormation; and

(2) the flow rate o~ air or oxygen through the reaction medium is sufficient to remove formaldeyde as it is formed.

~4f~iS~3~

This process, using the oxidation of toluene as an example, may be illustrated by the following equation:

PhCHO

3 2 2 ~ S04 This reaction scheme is in contrast to the first reaction scheme mentioned above which reads as follows:

PhCHO
phCH3+ 2AC2o + 2 ~ PhOAc + C ~ (OAc~2 + HOAc Thus it will be seen that by reducing the amount of acetic anhydride in the present case there is unexpectedly and selectively formed in addition to phenyl acetate, formaldehyde, to the substantial exclusion of methylene diacetate. When this modification is accompanied by an adequate, continuous flow of air or oxygen, formaldehyde vapors come out o~ solution where they are eondensed and recovered from the reaction medium, together wlth acetic acid and lesser amounts of certain methyl benzene-derived by products. As aforestated, the phenyl acetate may then be pyrolyzed to form phenol.

In generala this process is carried out as described above by oxidizing the desired methyl benzene with air or oxygen in the l~quid phase at pressures of at least 1 atmosphere and at temperatures as low as 80C to form a phenolic acetate and paraformaldehyde, together with the aforementioned acetic acid and methyl benzene-deri~ed by-products. After separation and recovery of the phenyl acetate and paraformaldehyde, the acetlc acid may be routinely converted to acetle anhydride and recycled to the oxidation step.

_ 7 _ . . , ~

In order to fully achieve the ob~ects of this invention and optimize the formation of paraformaldehyde, it is essential that acetic anhydride be metered into the reaction mixture at a rate such that there is sufficient acetic anhydride present to selectively react with one of the toluene oxidation products, (phenol) to ~ive phenyl acetate but not enough acetic anhydride to convert the other oxidation product (formaldehyde) to methylene diacetate, under reaction conditions. This may conveniently be accomplished by careful control of the amount of acetic anhydride introduced into the reaction as the oxidation process is monitored, e.g., by conventional chromatographic techniques.

The amounts and flow rate of air or oxygen are not critical but should in any event be sufficient to both oxidize the methyl benzene and at the same time remove the formaldehyde as it is formed. Thus, it is only essential that the air or oxygen be provided in a continuous flow. Generally, however, it may be sald that the amount of said gas can vary from about 1 to 100 volumes of gas per volume of liquid reaction mixture per unit of t~me, and preferably should be about 10 volumes of gas per minute per volume of reaction mixture.

The reaction is carried out in the presence of an acid catalyst, preferably H2S04, and benzaldehyde. The weight ratio of H2S04 to methyl benzene should generally be from about 5 x 10 to 1 x 10 2, and preferably 1 x 10 3 to 5 x 10 3, while the amount of benzaldehyde employed should be about 0.01 to 1.0 moles, and preferably 0.05 to 0.10 moles, ~er mole of alXyl ben~ene.

~:' If desired, the reaction may be run in excess methyl benzene reactant as a solvent, or in a suitable organic solvent such as benzene, chlorobenzene, or acetic acid. The latter is preferred inasmuch as increased selectivities are observed.
In order for rapid reactions in acetic acid, promoters such as Caro's Dry Acid should be present in amounts of lO-100 wt.
based on the amount of acetic anhydride used.

The formaldehyde may be recovered either as a monomer or perferably as a solid polymer, paraformaldehyde, which solidifies on a cool surface downstream of the reactor.

~ he reaction mixture containing the phenolic acetate, as well as lesser amounts of acetic acid, methyl benzene derived by-products, and the like is routinely treated to remove the acid catalyst, following which the acetate may be recovered by distillation under vacuum.

The following examples are provided solely for purposes of illustrating but not limiting the novel processes of this invention. Examples l to 10 illustrate the process wherein acetic anhydride is employed; examples 11 to 13 illustrate the use of acetic acid and phosphorus pentoxide; examples 14 and 15 illustrate the conversion of phenyl acetate and methylene diacetate to phenol and formaldehyde respectively, and examples 16 to 18 illustrate the direct recovery of formaldehyde and paraformaldehyde when special reaction conditions are employed.

Into a manometric gas-recirculation oxidation apparatus were charged following reactants:

Toluene 21.4 ml Acetic Anhydride 4.0 ml Sulfuric Acid 1 drop (-0.03g) Air in the reaction flask was replaced with nitrogen and the reaction mixture was heated to 101-3C. When the temperature reached the desired level nitrogen was replaced by pure oxyyen and the gas recirculating pump was started, charging oxygen through the liquid at 300-400 ml/min. The gas uptake was measured in the mercury filled buret by a/
displacement method. Liquld samples were withdrawn from the reaction vessel and analyzed by standard gas chromato-graphic techniques. No measurable oxygen uptake occurred under these conditions and no oxidation product(s) were found in the reaction mixture. After 2 hours and 25 minutes on stream 0.49g of benzoyl peroxide, a free radical initiator, was added to the reaction mixture and the reaction was contin-ued for additional 2 hours and 35 minutes. A slow oxygen up-take, a total of 185 ml was recorded as a function of time.

. -- 10 --~,r.

~4~S8~

At the end of this period, toluene oxidation products were analyzed by gas chromatography. The wt.%
values given are normalized on the basis of the following compounds:
Methylene diacetate (MDA), benzaldehyde (BAL), phenyl acetate (PA), benzyl acetate (BAC), phenyl hemiformal acetate (PHF), and other, unidentified products appearing within the same GC scanning range.
Although benzaldehyde is an added reagent it is conveniently included in the product analysis since it appears within the GC scanning range of toluene oxidation products.
The reaction mixture contained, calculated on the basis of the normalized product scans less than 1% of methylene diacetate (MDA) and ~3% phenyl acetate (PA). The bulk of the oxidized product was benzyl acetate (BAC), 28%, and benzylidine diacetate (BDA) 26~, together with a number of unidentified products.

Into the reactor was charged:

Toluene 21.4 ml Acetic Anhydride 4.0 ml Sulfuric Acid 1 drop (0.03g) The reaction was carried out in the same manner as in Example 1 for 1 hour. There was no oxygen absorption over this time period, at the end of which 1.0 ml. benzaldehyde and 3 drops of sulfuric acid were added. The oxygen absorp-tion commenced after a few minutes; at the end of the reaction .

i5~

after total of 3 hours, 50 minutes 636 ml oxygen had been absorbed. Analysis of the liquid ox:idation product carried out as described in Example 1 showed 10% MDA and 11% PA were present, together with 20% ~AC and 12~ phenylhemiformal acetate (PHF), a precursor of both PA and MDA.

Into the reactor was charged:

Toluene 21.4 ml Acetic Anhydride 4.0 ml Sulfuric Acid1 drop (0.03g) The reaction was carried out initially as in Example 1 for 4 hours and 16 minutes with only negligible oxygen uptake recorded over this time period. At the end of this period 1.0 ml. of benzaldehyde and 0.56g. of potassium persulfate were added to the reaction mixture. The oxygen uptake commenced after a few minutes and a total of 712 ml oxygen were absorbed by the end of 7 hours and 33 minutes.
The toluene conversion, based on oxygen absorbed was ca 10%.
The liquid product analysis as determined in Example 1, showed 10% MDA, 12% PA, 16% ~AC and 10% PHF among the oxidation products of toluene.

Into the reactor was charged:

Toluene 21.4 ml Acetic Anhydride 4.0 ml Acetic Acid12.0 ml Benzaldehyde2.0 ml Dry Caro's Acid0.25 g Sulfuric Acid3 drops (~ O.lg) Reaction was carried out initially as in Example 1 with all the ingredients added at the start and after 2 hours and 20 minutes a liquid product sample was analyzed; 12% MDA, 11% PA and 9.5% of PHF were present in the product. The reaetion was continued for a total of 6 hours and 55 minutes.
At 3 hours and 34 minutes 2.0 ml of acetic anhydride and at 6 hours and 4 minutes 0.25g of Dry Caro's acid were added.
The final liquid oxidation product, analyzed as in Example 1, contained 20% MDA, 19% PA, 13% BAC and 4% PHF. The total oxygen uptake was 490 ml with 1.6 m mole CO2 produced in the reaction.

Into the reactor was charged:

Toluene 21~4 ml Acetic Anhydride4.0 ml Acetic Acid12.0 ml Benzaldehyde1.0 ml Co-stearate 7.4 mg The oxidation reaction was carried out initially as in Example 1. At the end of 3 hours and 15 minutes 514 ml oxygen had been absorbed. The product, analyzed as in Example 1, contained 16% MDA, 5% PA and 7% PHF.

Into the reactor was charged:

~oluene 21.4 ml Acetie Anhydride 8.0 ml Aeetie Aeid12.0 ml Benzaldehyde1.0 ml Sodium Perborate 1.54 g.
Tetrahydrate ~: Sulfuric Acid3 drops (-- 0.1 g.) 8~i Reaction was carried out as in Example 1. After 3 hours and 22 minutes 780 ml oxygen had been absorbed.
Analysis of the liquid oxidation product, as in Example l, showed 14% MDA 2% PA, 37% benzaldehyde and 34% other products.

Into the reactor was charged-Toluene 42.8 ml Acetic Anhydride 8.0 ml Sulfuric Acid 2 drops (0.07g) Reaction was carried out initially as in Example l.The following reactants were added in the course of the oxida-tion reaction at given time intervals: cyclohexanone, 0~6 ml at 35 min. over a 40 min. period; azobisisobutyronitrile (AIBN), 66 mg. at 186 min.; potassium persulfate, 0.20 g. at 300 min.
The reaction was carried out for a total of l0 hours and 27 minutes whereby a total oxygen uptake was 790 ml. Only traces of the desired products PA and MDA were found among the oxidation products.

Into the reactor was charged:

p-Xylene 24.l ml Acetic Anhydride 4.0 ml Benzaldehyde l.0 ml Dry Caro's Acid 0.5 g Sulfuric Acid 3 drops (~0.1g) Chlorobenzene l.0 ml (as internal standard) The reaction was carried out initially as in Example l; the reaction temperature was 104-7 and after 4 hours the total oxygen uptake was 582 ml. Analysis of the oxidized product showed the presence of _-cresyl acetate 28%, '.."~' B~

and methylene diacetate 16%, 7.5 m mole of carbon dioxide was also formed.

Into a 300 ml rocker bomb was charged:

~ Toluene 43.0 ml Acetic Anhydride 8.0 ml ~enzaldehyde 2.0 ml Dry Caro's Acid 1.0 g Sulfuric Acid 0.11 g The bomb was pressurized with 120 psl oxygen and 170 psi nitrogen, i.e. total 290 psi at room temperature and was heated to 120 over a 30 minute period. The reactor was heated at 115-120 for 3 hours, 35 minutes, resulting in the pressure drop of 65 psi. Analysis of the oxidation product, as in Example 1, showed 17% PA, 24% MDA and 8% PHF.

Into a 300 ml rocker bomb was charged:

Toluene 50 ml Acetic Anhydride 11.4 ml Sulfuric Acid 0.11 g The bomb was pressurized with 30 psi oxygen and 145 psi nitrogen, i.e. total of 175 psi at room temperature.
The reactor was heated at 130 for an 8 hour period; no pressure drop was observed and no oxidation products were detected in the reaction mixture at the end of the reaction.

B~

Into a manometric gas-reeirculating oxidation appara-tus was charged, under nitrogen Toluene 21.4 ml.
Acetic Acid 12.0 ml.
Benzaldehyde 1.0 ml.
Phosphorous Pentoxide 2.5 g.
Dry Caro's Acid 0.5 g.

The reaetion mixture was heated to 102, nitrogen was replaced by pure oxygen and the gas reeirculating pump was turned on, sparging oxygen below the surface of the liquid at a rate of 350 ml./min. The oxygen uptake was measured in the mereury filled buret by displacement. Liquid samples were withdrawn from the reaction flask, and analyzed by standard gas chromatographic techniques.

After 1 hr. and 15 min. 197 ml. of oxygen had been absorbed. The toluene oxidation produets were analyzed by GC.
The wt.% values given are normalized on the basis of the following compounds: Methylene diacetate (MDA), benzaldehyde (BAL), phenyl acetate (PA), benzyl aeetate (BAC), phenyl hemi-formal aeetate (PHF), and other, unidentified products appear-ing within the same GC seanning range. Although benzaldehyde is an added reagent it is eonveniently included in the product analysis sinee it appears within the GC scanning range of toluene oxidation products. The reaction mixture contained, caleulated on the basis of the normalized produet scans:
(MDA) 8~, (BAL) 30%, (PA) 23%, (BAC) 5%, other unidentified produets within the same scanning range 34%. The reaction was continued for 5 hrs. at the end of this period the reaction product analyzed: MDA 14%, BAL, 30~, PA 20%, BAC 3~, others 33%.

Into a 300-ml. rocking bomb was eharged:

Toluene 43.0 ml.
Aeetic Anhydride 2.0 ml.
Acetic Acid 16.0 ml.
Benzaldehyde 2.0 ml.
Dry Caro's Acid 1.0 g.
Phosphorus Pentoxide 5.0 g.
Sulfuric Acid 0.11 g.

The bomb was pressurized with 120 psi of oxygen and 170 psi nitrogen and was heated to 120C over a 30 min. period, then held at 120C for 1 hr. 25 min. The pressure drop after cooling to room temperature was 32 psi. The reaction mixture was analyzed for the toluene oxidation products as in Example 1.
MDA 21%, BAL 18%, PA 21%, BAC 5%, phenylhemiformal acetate (PHF) 8%, others 26%.

Into the manometric recirculating reactor was charged:

Toluene 21.4 ml.
Acetic Acid 12.0 ml.
Benzaldehyde 1.0 ml.
Dry Caro's Acid 0.5 g.
Anh. Magnesium Sulfate 3.0 g.

The reaction was carried out as in Example 1 at 103C for 2 hrs. and 30 min. At the end of this period no detectable oxidation products were shown by the gas chromato-graphy.

Pyrolysis of methylene diacetate to paraformal-dehyde and acetic anhydride can be accomplished thermally at about 500C in a known manner.

8~

Alternatively, the catalytic pyrolysis of methylene diacetate may be carried out at about 300C in the presence of a catalyst composed of 5% sodim chloride mixed with silica gel, dried and calcined. The methylene diacetate, dissolved in n-hexane, is passed through a passified tubular reactor packed with the catalyst at a space velocity of 900 hr 1 and a temperature of 300C. Paraformaldehyde and acetic anhydride condense downstream and are separated routinely. Selectivi-ties exceed 93% for acetic anhydride and 95% for methylene diacetate.

EXA~PLE 15 Pyrolysis of phenyl acetate to phenol and ketene is accomplished thermally at 625C by passing it through a well-conditioned tubular reactor. The effluent is condensed to give 84% yield of phenol and 89% yield of ketene.
The reaction may be carried out at a somewhat lower temperature in the presence of triethyl phosphate catalyst at space velocities of between 900 and 1000 hr 1. Yields in excess of 90% are obtained.
Cresyl acetate may be converted in a like manner to cresol.
The results of the foregoing Examples can better be appreciated in llght of the following discussion:
Example 1 shows that essentially no oxidation of toluene occurs in the presence of acetic anhydride and sulfuric at the pressures and temperatures given. It further shows that upon addition of a free radical chain initiator such as ~4~i~8~

benzoyl peroxide, a slow oxidation reaction takes place but the predominant products are not the desired phenyl acetate (PA) and methylene diacetate (MDA) which are both present in amounts less than 3%.
Example 2 shows that addition of benzaldehyde to toluene plus acetic anydride plus sulfuric acid causes a resonably rapid reaction to occur, whereby ~10% MDA, ll~o PA
and 12% PHF, a precursor of MDA and PA, are formed.
Example 4 shows that the oxidation of toluene in the presence of acetic anhydride, and acetic acid, benzalde-hyde, dry Caro's acid, and sulfuric acid gives a superior selectivity to PA and MDA. The key factor here would appear to be the addition of Caro's acid plus acetic acid to other previsouly used reactants.
Example 5 shows that addition of a conventional toluene oxidation catalyst i.e. a cobalt salt, does not promote a selective reaction since only 5% of PA was found together with 11% BAC.
Example 6 shows that another strong, non-heavy metal oxidant such as sodium perborate does not promote the formation of PA since less than 2% of the latter was present.
Example 7 shows that use of another carbonyl-containing promoter, cyclohexanone, instead of benzaldehyde does not result in the formation of the desired products, PA and MDA.

51~5 Example 8 shows that benzaldehyde can promote the oxidation of higher homologs of toluene e.g., xylenes. In the case of p-xylene, p-cresyl acetate is formed.
Example 9 shows that when co-oxidation of toluene and benzaldehyde is carried out at 120 i.e. at low tempera-ture and somewhat elevated pressure of oxygen (120 psi), substantial quantities of both PA and MDA are obtained.
Example 10 shows that no oxidation occurs at 130 in the absence of benzaldehyde.

Into a manometric gas~recirculation oxidation appa-ratus was charged:

Toluene 42.8 ml Acetic Anhydride 1.0 ml Benzaldehyde 1.0 ml Sulfuric Acid 2 drops (~J0.06g) Air in the reaction flask was replaced by nitrogen and the reaction mixture was heated to~ 100C. When the temperature reached 100C nitrogen was replaced by pure oxygen and the gas recirculating pump was started, sparging oxygen through the liquid at 300-400 ml/min. The gas uptake was recorded with time by measuring the displacement in a mer-cury filled gas buret assembly. Liquid samples were withdrawn from the reaction flask and analyzed by standard gas chromato-graphic techniques. Acetic anhydride was added, incrementally, -~

to the reaction mixture from a motor driven syringe pump be-tween 49-108 min., 0.72 ml and 172-220 min. 0.20 ml. At the end of this time period (3 hours, 40 min.) the oxygen uptake was 349 ml and the oxidized product contained phenyl acetate (PA) 26%, methylene diacetate (MDA) 7%, pheny~ hemiformal acetate (PHF) 2%, ben~yl acetate (BAC) 14%. A substantial quantity of a white solid covered the cold surfaces of the reactor and con-denser. Analysis showed this material to be a solid polymer of formaldehyde, i.e., paraformaldehyde.
In accordance with foregoing procedure, but substi-tuting xylene for toluene, there is obtained cresyl acetate and paraformaldehyde, together with acetic acid and related by-products.

Into the reactor was charged:

Toluene 42.8 ml Acetic Anhydride 1.0 ml Benzaldehyde 1.0 ml Potassium Persulfate 0.54 g Sulfuric Acid 2 drops (~ 0.06 g) The reaction was carried out as in Example 1, at lOO~C with incremental addition of acetic anhydride between 33-73 min., 0.82 ml and 100-160 min., 0.62 ml. After 2 hrs.
40 min. the reaction was stopped, with a total oxygen uptake of 280 ml. The oxidation product contained PA-17%, MDA-trace, BAC 8%. The cold walls of the reactor and condenser were covered with a white solid which was shown to be solid paraformaldehyde by infrared analysis.

Into the reactor was charged:

Toluene 42.8 ml Acetic Anhydride 16.0 ml Benzaldehyde 1.0 ml Potassium Persulfate 0.43 g Sulfuric Acid 2 drops (~ 0.06 g) The~reaction was carried out as in Example 1, except that all the reactants were present initially and no incremental addi-tion was carried out. At the end of 5 hr. reaction had stopped with total of 240 ml oxygen absorbed.
Only 3% PA and MDA were found among the oxidation products which also contained 19~ BAC. No solid paraformal-dehyde was detected.

Claims

1. A process for the oxidation of methyl benzenes under mild reaction conditions to form phenolic acetates and methylene diacetate which comprises contacting said methyl benzenes with air or oxygen, and acetic anhydride, in the presence of a strong acid catalyst and benzaldehyde at tempera-tures of at least 80°C and pressures of at least 1 atmosphere, and recovering the phenolic acetate and methylene diacetate.

2. The process of Claim 1 wherein the acid catalyst is H2SO4.

3. The process of Claim 1 wherein the temperature is from about 80° to 150°C.

4. The process of Claim 1 wherein the pressure is from about 1 to 10 atmospheres.

5. The process of Claim 1 wherein a suitable organic solvent is employed.

6. The process of Claim 5 wherein the solvent is acetic acid and a promoter for said acid.

7. The process of Claim 1 wherein the reaction is carried out in the presence of a persulfate promoter.

8. The process of Claim 7 wherein the promoter is Dry Caro's acid.

9. The process of Claim 1 wherein the benzaldehyde is present in amounts of 0.01-1.0 mole based on the methyl benzene.

10. The process of Claim 1 wherein the methyl benzene is toluene and the products are phenyl acetate and methylene diacetate.

11. The process of Claim 1 wherein the methyl benzene is a xylene and the products are a cresyl acetate and methylene diacetate.

12. The process of Claim 1 wherein the phenolic acetate and methylene diacetate are separated and pyrolyzed to form respectively a phenol and formaldehyde.

13. A process for the oxidation of methyl benzenes to form phenolic acetates and formaldehyde or methylene diacetate which comprises contacting said methyl benzenes with air or oxygen, and acetic acid and P2O5, in the presence of a strong acid catalyst and benzaldehyde.

14. The process of Claim 13 wherein the acid catalyst is H2SO4.

15. The process of Claim 13 wherein the reaction is carried out at a temerpature of at least about 80°C and pressures of at least about 1 atmosphere.

16. The process of Claim 13 wherein the temperature is from about 80°C to 150°C.

17. The process of Claim 13 wherein the pressure is from about 1 to 10 atmospheres.

18. The process of Claim 13 wherein a suitable organic solvent is employed.

19. The process of Claim 13 wherein the reaction is carried out in the presence of a persulfate promoter.

20. The process of Claim 19 wherein the promoter is Dry Caro's Acid.

21. The process of Claim 13 wherein the benzaldehyde is present in amounts of about 0.01 - 1.0 mole based on the methyl benzene.

22. The process of Claim 13 wherein the methyl benzene is toluene and the products are phenyl acetate and methylene diacetate.

23. The process of Claim 13 wherein the methyl benzene is xylene and the products are cresyl acetate and methylene diacetate.

24. The process of Claim 13 wherein the phenolic acetate and methylene diacetate are separated and pyrolyzed to form respectively a phenol and formaldehyde.