CA1178616A

CA1178616A - Decomposition of cumene oxidation product

Info

Publication number: CA1178616A
Application number: CA000405592A
Authority: CA
Inventors: Stylianos Sifniades; Allen A. Tunick; Fred W. Koff
Original assignee: Individual
Current assignee: Sunoco Inc R&M
Priority date: 1981-06-22
Filing date: 1982-06-21
Publication date: 1984-11-27
Also published as: IT8267783A0; DE3222533C2; US4358618A; JPS5832831A; DE3222533A1; KR850001469B1; MX165355B; IT1156366B; JPH0251408B2; GB2100730B; KR840000460A; GB2100730A

Abstract

ABSTRACT
A cumene oxidation product containing cumene hydroperoxide (CHP) and dimethylphenylcarbinol (DMPC) is decomposed with acid catalyst in a first step at mild temperatures that lowers the CHP concentration to about 0.5-5% and converts most of the DMPC to dicumylperoxide (DCP). In a second step at mild temperatures the CHP
concentration is lowered below 0.4%. In a third step the DCP is decomposed at a higher temperature for a short time to alpha-methylstyrene (AMS), Phenol and acetone, with any remianing DMPC also converted to AMS.
The DCP concentration is monitored during the third step, and the reaction is stopped by cooling when about 0.5-5% of the DCP remains undecomposed so as to maximize AMS yield.

Description

,~J -- ~ J -~ -~l786316 DESCRIPTION
DECOMPOSITION OF CUMENE OXIDATION PRODUCT
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BACKGROUND OF THE INVENTION
_ _ _ _ Phenol is manufactured via air oxidation of cumene to cumene hydroperoxide (CHP), followed by acid-catalyzed cleavage of the latter to phenol and acetone.
S CHP decomposition is a very exothermic reaction which is normally carried out on a commercial scale in continuous stirred or back-mixed reactors. In such reactors only a small fraction of CHP is unreacted any given time and the reaction medium consists essentially of the products of decompositiQn of CHP, i.e., phenol and acetone, plus any solvent (e.g., cumene) and other materials added with CHP to the reactor. During cumene oxidation small amounts of dimethyl phenyl carbinol (DMPC) and aceto-phenone are also formed. In the presence of acid cata-lyst, DMPC dehydrates to alpha-methylstyrene (AMS), a useful by-product. Very high yields of AMS can be obtained from pure DMPC, e.g., 98~ yield upon dehydra-tion over acidic silica at 300C. In the presence of phenol, however, and more .specifically in phenol/ace-tone/cumene which is solvent in decomposition of tech-; nical CHP/DMPC mixtures, the ultimate AMS yield is normally about 50-60 mol~ of the DMPC. Main by-products are AMS dimers and cumylphenol which have no commercial value. Formation of cumylphenol also reduces the phenol yield.
G.G. Joris, U.~S. Patent 2,757,209, teaches that the amount of AMS dimers and cumylphenol formed .~

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can be substantially reduced by carrying out the reac-tion in two stages. In the first stage CHP is decom-posed in a stirred or back-mixed reactor in the presence of small amounts of sulfur dioxide as catalyst and water as catalyst moderator. Preferred conditions are: tem-perature 45-65C, sulfur dioxide 50-5no ppm, water 2-5 wt~. Under these conditions the C~P concentration in the reaction mixture withdrawn from the reactor is less than 5% ~ut more than 1% by weight. In the second stage, the mixture withdrawn from the first reactor is heated in a second reactor, optionally with additional catalyst, in order to effect the dehydration of DMPC to AMS. -This second reactor is either a batch reactor, or a continuous plug-flow reactor. Preferred conditions are: temperature 110-120C, reaction time 5-15 min.
Care must be taken to stop the high temperature reaction once AMS formation is completed so as to avoid the dimerization of ~IS or the reaction of AMS with phenol to form byproducts.
C.Y. Yeh, et al, U.S. Patent 4,016,213, teaches a modification of the above process wherein the back-mix reactor is operated in a manner to avoid the dehydration of DMPC. The mixture withdrawn from the back-mix reactor is immediately treated with base and the DMPC is subsequently recovered from the final dis-tillation wherein crude phenol is the overheads and DMPC
is found with acetophenone in the bottoms.
~ . Boardman, U.S. Patent 2,668,180, teaches that DMPC and CHP interact in the presence of an acid condensation catalyst to form dicumyl peroxide (DCP).
The reaction medium is excess DMPC; examples of cata-lysts used are p-toluenesulfonic acid, sulfuric acid and boron trifluoride.
Ko. Tsunoda and T. Kato, Nippon Kagaku Zasshi, Volume 81, No. 2, page 310 (1960) studied the reaction of DMPC with CHP in homogeneous benzene/acetic acid solution using perchloric acid as catalyst and also in a two phase benzene/aqueous mixture using sulfuric acid as , `
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catalyst. They report that two reactions take place simultaneously: a) condensation of DMPC with CHP to form DCP, and b) decomposition of CHP to phenol and acetone.
These last two references indicate that DCP
may also be formed during the acid catalyzed decomposi-tion of technical CHP. M.S. Kharasch et al, Journal of organic Chemistry, Volume 15, page 753 (1950), reported that DCP is decomposed in acetic acid solution in the `-presence of catalytic amounts of perchloric acid to phenol, acetone and AMS dimer. It is, therefore, possible that DCP is formed during the decomposition of technical CHP and that at least some of the AMS dimers formed during ~he process originate from subsequent decomposition of DCP.
SUMMARY OF THE INVENTION
The present invention includes a process for decomposing a cumene oxidation product mixture contain-ing cumene hydroperoxide (CHP) and dimethylphenyl car-binol (DMPC) to produce phenol, acetone and alpha-methyl styrene (AMS) with reduced byproduct formation which comprises the steps:
a) mixing the cumene oxidation product with an acid catalyst in a back-mix reactor in the presence of about 0.4 to about 4.5 % water, by weight of reaction mixture, at a temperature between about 50C and about 90C for a time sufficient to lower the CHP concentra-tion of the back-mix reaction mixture to between about 0.5 and about 5.0 weight % and to convert at least 40 %
of the DMPC in the cumene oxidation product to dicumyl-peroxide (DCP);
b) reacting the back-mix reaction product at between about 50C and about 90C under plug flow conditions for a time sufficient to produce a second mixture having a CHP concentration no more than about 0.4%; and c) reacting the second reaction mixture, at a temperature between about 120 and about 150C under plug flow conditions for a time sufficient to convert at ~ .

`' .` ' : ' 8~6 least 90 % of the DCP to AMS, phenol and acetone.
Thus the present invention involves intention-ally converting a substantial amount of the DMPC to DCP
in step (a) while the CHP concentration remains at least 0.5~, lowering the CHP concentration to below 0.4~ under mild conditions in step (b) which will not result in substantial AMS formation, and in step (c), quickly con-verting the DMPC and DCP to AMS. The DCP concentration during step (c) is preferably monitored, e.g. by gas chromatography, and the reaction is stopped by cooling or neutralizing when 0.5-5~ of the DCP remain undecom-posed.
BRIE~ DESCRIPTION OF THE DRAWING
Figure 1 is a schematic flow diagram of an embodiment of the process of the invention.
Figure 2 is a plot of disappearance of dicumyl peroxide (DCP) and yield of alpha-methyl styrene (AMS) as a function of tempera~ure (C) and time under the isothermal plug flow conditions described on page 5 of this Specification.

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-4a-DETAILED DESCRIPTION OF THE INVENTION
We have discovered that when technical CHP is decomposed in a stirred or back-mixed reactor in the presence of an acid catalyst, varying amounts of DCP are formed. The amount of DCP formed increases with increasing concentration of CHP in the reaction mixture and it may be as high as 70 mol% of the amount of DMPC
present in the CHP feed. DCP is rela~ively stable under conditions that cause substantial CHP decomposition, but it can be decomposed to yield mainly phenol, acetone and AMS under more forcing conditions, e.g., in the presence of increased acid catalyst concentrations or at higher temperature. We have found that high AMS yields are obtained from DCP in the temperature range 120-150C.
The same higher temperature conditions that favor forma-tion of AMS from DCP also favor dehydration of DMPC to AMS. It is, therefore, convenient to transform both the DMPC and the DCP present in the reaction mixture result-ing from the acid catalyzed decomposition of technical CHP in a stirred or back-mixed reactor by simply heating that mixture to 120-150C for a limited period of time in a plug-flow reactor, optionally with additional acid catalyst. The plug flow reactor generally is composed of a heat exchanger in which the reaction mixture is brought up to the desired temperature, in series with a pipe or baffled tank, in which the reaction is ccm-.

' 86~6 5pleted. The latter part of the reactor is essentially isothermal. The yield of AMS formed in the reaction increases with time as DCP and the residual DMPC decom-pose, until it reaches a maximum and then decreases as AMS reacts further to orm AMS dimers and cumylphenol.
The optimum reaction time depends on the temperature and the concentrations of acid catalyst and water present in the mixture. Generally, shorter times are required at higher temperatures and in the presence of higher con-lQ centrations of acid and lower concentrations of water.
We have found that an excellent way of locat-ing optimum reaction conditions in the plug flow reactor is by monitoring the DCP concentration. The attached Figure 2 shows the yield of AMS produced and the per-centage of DCP left unreacted by heating a typical feed-tock at various temperatures (C indicated by numbers over arrows) for various periods of time in an isother-mal plug-flow reactor. This particular feedstock was produced by decomposing technical CHP (83 wt~ in cumene, containing also 3.0 wt~ DMPC, 0.4 wt~ acetophenone and 0.2 wt~ DCP) in a back-mix reactor with residence time 28 min, at 75C, in the presence of 75 ppm sulfuric acid and 1 wt% added water. The reaction mixture contained 0.93 wt~ CHP, 0.69 wt% DMPC, 0.92 wt% AMS, 2.40 wt ~ DCP
and small amounts of AMS dimer, cumylphenol and cumyl-phenyl ether. Plots similar to those shown in the figure were produced starting from several other feed-stock compositions. These plots have two common fea-tures:
a) DCP disappearance is linear on a logarith~
mic scale, i.e. it follows first order kinetics, under all conditions of practical interest~ and b) The maximum AMS yield is obtained when the remaining DCP concentration is between about 0.5% and about 5~ of the DCP concentration charged into the iso-thermal plug flow reactor.
- DCP concentration may be conveniently deter-mined by gas chromatography, li~uid chromatography or . ~; , ' .
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~j iodometric titration. Since the DCP concentration at the plug flow reactor exit is relatively low and thus subject to large analytical errors at the DCP conver-sion desired, it may be more convenient to measure DCP
at an intermediate point in the reactor. Because of the linearity of DCP disappearance on a logarithmic scale, the DCP concentration at the reactor exit may be found by extrapolation.
In order to effect substantial transformation of DMPC to DCP, it is necessary to have between 0.5~ and 5% CHP, and preferable to have between about 0.8 and about 2% CHP, all by weight, present in the reaction mixture resulting from the decomposition of technical C~IP in a stirred reactor; i.e., step (a). The percent-age of unreacted CHP can be ad]usted by employing theappropriate combination of acid catalyst concentration, reaction temperature, water concentration and residence time in the reactor. The choice of particular combina-tions of these elements should be easily determinable by routine experimentation. Thus~ in addition to sulfur dioxide, various strong stable mineral acids such as sulfuric acid, perchloric acid and the like may be used;
or Lewis acids such as boron trifluoride or aluminum chloride may be used; or organic acids such as toluene ~5 sulfonic acid may be used. Typical acid levels are between 30 and 400 ppm (0.003-0.04~). Water is desira-bly added to the back-mix reactor in addition to that formed by the desired reaction of DMPC with CHP to form DCP, by other condensation of DMPC or by the dehydration of DMPC to form AMS. The preferred water concentration present in step (a) is between 0.8 and l.S % by weight.
The water present from condensation and decom-position of DMPC will be between 0.3 and 0.7% when DMPC
is about 3-7% of the oxidation product and about 70-80%
of the DMPC is either condensed or dehydrated in the first step. The water level desired for the first step, 0.4 to 4.5%, preferably 0.8 to 1.5%, may be achieved by the water formed from DMPC or may require ~L17~6 additional waterO
The temperature for step (a) is in the range of 50-90C; preferably 60-80C. Below 50C removal of the heat of reaction becomes inefficient; above 90C the yield of phenol and acetone produced from CHP is signi-ficantly diminished. Residence time in the reactor depends on the temperature and acid and water content of the reaction mixture. A typical combination is 70C, 70 ppm sulfuric acid catalyst, 1~ water added, 20 min resi-dence time. Under these conditions the reaction productcontains 0.5-5 wt% CHP; some of the DMPC remains unre-acted, some is converted to AMS and a large portion is converted to DCP. Only minor amounts of AMS dimers and cumylphenol are formed.
The product of this reactor may be subsequent-ly heated at a higher temperature in a second, plug-flow reactor. This treatmen~ results in the decomposition of residual CHP to phenol and acetone and also in the decompositlon of DCP to phenol, acetone and AMS and of DMPC to A~S.
We have also discovered, however, that the acid-catalyzed decomposition of CHP to phenol and ace-tone proceeds in high yield at temperatures lower than - 90C. At higher temperatures, increasing amounts of DMPC-related by-products are formed. To the extent that unreacted CHP is present in the reaction product of the first reactor and it is decomposed at elevated tempera-tures in the second reactor, small hut significant yield losses of phenol and acetone are incurred (as indicated below in the discussion in the Examples 1-5). We have discovered that these losses can be avoided by placing a third reactor between the two already mentioned. This reactor is plug-flow and is maintained at a temperature which is roughly equal to that of the first reactor.
Residence time may be a few minutes. Due to the short residence time required, this reactor may simply be a pipe connecting the other two reactors. Residual CHP is substantially decomposed in this reactor, to below 0.4%

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and preferably below 0.2 %, whereas DCP and DMPC are essentially unaffected. The product from this reactor can then be sent downstream for decomposition of DCP and DMPC at elevated temperatures.
The invention can be illustrated by reference to Figure 1 which can be compared to the Figure of U.S. Patent 2,757,209. Step (a) is performed in back-mix reactor 1 at between 50C and 90C under conditions establishing a residence time of 5 - 120 min. Technical CHP, acid catalyst and water are introduced to the reac-tor through inlets 2, 3 and 4 respectively. The desired temperature is maintained by means of circulation through cooler 5. Due to the strong exothermicity of CHP decomposition, the minimum residence time in reactor 1, which includes time spent in cooler 5 is determined by the design of the cooler, and the nature of cooling fluid. A practical lower limit of approximately 5 min is imposed if the coolant is water. Lower residence time may be achieved if a refrigeration system is employed bu~ this serves no useful purpose. The upper limit of residence time depends on the temperature, the acid content and the water content of the reaction mix-ture. A residence time of approximately 120 min may be considered as the upper limit. Preferred residence time is between 10 and 60 min.
The product from reactor 1 is next pumped through a piece of tube 6 to heater 7. Step (b) of the reaction is carried out in tube 6 which has sufficient capacity ~o pro~ide a residence time between 0.1 and 10 min. The temperature in tube 6 is approximately the same as in 1. No means for cooling is provided, because the only significant reaction taking place in this step is decomposition of residual CHP which has already been reduced to 0O5-5~ level in step (a). In heater 7 the product is heated to 120-150C and then is pumped to cooler 9 through pipe 8. The total residence time in heater 7 and pipe 8 is sufficient to cause decomposition of DCP and dehydration of DMPC to AMS as , .
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7~6~i g well as complete decomposition of any residual CHP.
Best AMS yields are obtained if the residence time in heater 7 is relatively short (e.g. under 30 seconds) compared to that in pipe 8 (at least 30 additional seconds), because in that way most of the DMPC dehy-drates at the higher temperature regime which favors AMS
formation. Pipe 8 is fitted with sampling ports at the entrance 8A, at an intermediate point 8B and at the exit 8C, for monitoring DCP concentration. At the cooler 9, the reaction product is cooled to 30-50C and then sent to an anion exchange resin bed, 10, in order to neutral-ize the acid catalyst. The neutralized product is then sent to a distillation train for frationation and recovery of the various components.
Examples 1-5, Decomposition of Pure CHP
0.8 mL of a mixture composed of 53 wt% phenol, 32 wt% acetone and 15 wt% cumene was mixed with 0.04 mL
of 2% aqueous sulfuric acid. The resulting mixture con-tained 0.5% water and 100 ppm acid. It was piaced in a

2 mL sealed reaction vessel equipped with a thermometer and a magnetic stirrer. The mixture was placed in an oil bath and heated to 70C, then 0.75 mL of pure CHP
was introduced by a syringe pump through a silicon rub-ber septum within 7 min. The temperature was maintained at 70C during the CHP addition and for an additional 1 min afterwards. Then the reaction mixture was cooled and analyzed by gas chromatography for phenol, AMS, DMPC, AMS dimers, cumylphenol, cumylphenyl ether and acetophenone. All components other than phenol repre-sent undesirable decomposition of CHP (since there wasno DMPC initially present). For brevity, AMS, DMPC, AMS
dimers, cumylphenol and cumylphenyl ether were added together on an equivalent basis and reported as "carbinol equivalents produced per mol phenol produced."
Acetophenone was reported separately because its forma-tion does not involve the intermediacy of D~IPC. The experiment was repeated at various temperatures and the results were summarized in Table I. It is ~lear from - .. ..

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the data in Table I that as the temperature of C~P
decomposition increases the amount of carbinol equival-ents and acetophenone produced also increases. Yield loss of phenol due to these by-products amounts to 0.7 mol~ at 90C and becomes very significant at higher temperatures. It should be realized that, if DMPC were also originally present, the carbinol equivalents from CHP shown in Table I would be additional to the carbinol e~uivalents from DMPC.
Table_I
Acid Catalyzed Decomposition of Pure CHP
Temper-ature By-products (mol~mol phenol)X100 Example C Carbinol E~uivalent Acetophenone Total 1 70 0.36 0.06 0.42 2 90 0.61 0.06 0.70

3 110 1.24 0.15 1.49

4 122 2.19 0.25 2.44 146 5.04 0.69 5.75 aIn phenol/acetone/cumene solution containing initially 0.5 wt% water and 100 ppm sulfuric acid.
Examples 6-8: Dehydration of DMPC
A stock solution containing 6 wt~ DMPC, 15 wt%
cumene and 50 ppm sulfuric acid with the balance com-posed of equimolar phenol and acetone was distributed among several melting point capillary tubes which were subsequently sealed and heated for various lengths of time in a stirred oil bath. The tubes were then quickly cooled by immersion in an ice bath and the contents were analyzed by gas chromatography. The amount of AMS
formed increased with time up to a maximum yield and then declined as increased amounts of AMS dimers and cumylphenol were formed. Table II records the maximum AMS yield obtained at each temperature, as well as the heating time required to reach that yield. It is clear from the data of Table II that the best yields of AMS
were obtained at temperatures over 90C, e.g.~ 120 and 130C.

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Table II
Acid Catalyzed Dehydration of DMPCa Temperature Max. AMS Time to Max AMS
Example ~C mol% min _ 7 120 86 1.5 8 130 87 1.0 aIn phenol/acetone/cumene containing 50 ppm sulfuric acid When examples 1 to 8 are considered together, it is evi-dent that, given a mixture of CHP and carbinol, it is not possible to obtain highest yields of phenol from CHP
and AMS from carbinol at a single temperature because the first transformation gives bes~ yields at temperatures below 90C whereas the second gives best yields at temperatures higher than 90C.
Examples 9-12: Acid-Catalyzed Decomposition of Technical CHP
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Technical CHP, 83 wt~, also containing 3.2 wt% carbinol and 0.4 wt. ~ acetophenone with the balance being cumene, was pumped into a stirred vessel maintained at 50C. Simultaneously, a 1~ solution of suifuric acid in phenol was pumped into the vessel at a rate sufficient to maintain a concentration of 50;ppm sulfuric acid in the reaction mixture. ~Reaction product was contlnuously withdrawn from the vessel so that the amount of mixture in the vessel remainèd constant. The residence time of the reaction mixture in the vessel was 17 min. After two hours of continuous operation, the reaction product was analyzed by gas chromatography and found to contain 1% CHP, 0.4% acetophenone and 3.4% total carbinol equivalent. The latter is defined as the sum of all products which can be formed by reactions of DMPC
reported as DMPC in wt~. The carbinol equivalent 35 was composed of the following components (as equivalent `;
% of total carbinol equivalent): AMS 18.0, DMPC 15.8, AMS dimers 10.0/ DCP 4~.5, cumylphenol 9.5, cumylphenyl ether 0.7.

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~L~L78~6 Other examples are summarized in Table II.
These examples show that decomposition of CHP
under mild conditions that allow a significant amount of CHP to remain unreacted result in substantial transfor-mation of DMPC to DCP. On the other hand, if the decom-position conditions are such that very little CHP re-mains unreacted, no significant amount of DCP is formed.
Thus in comparative example 12, in which 0.1 wt~ C~P
remained in the reaction produc~, only 6~0 mol% of the DMPC-derived products was DCP; moreover, a larger por-tion of the DMPC was converted to AMS dimers and cumyl-phenol in this example.
TABLE III
Acid Catalyzed Decomposition of Technical CHPa Examples _ Temperature, C S0 60 75 75 Time, min 17 13 13 30 H2S4' ppm 50 50 50 75 H2O added, wt~ - 0.5 1.0 Acetophenone, wt%0.4 0.4 0.4 0.4 CHP, wt% 1.0 0.9 1.2 0.1 Total CE,b wt~ 3.4 3.4 3.4 3.6 AMS, mol~ of CEb18.0 8.7 22.7 51.7 DMPC, mol% of CEb15.821.6 19.7 8.3 CPE~C n n n 0.7 1.8 1.6 0.9 AMS Dimers," " "10.0 0.5 3.8 19.9 DCP, n " n 46.5 65.2 47.7 6.0 Cum~lphenol, n n9. 5 2.2 4.6 13.1 aInitial composition: 83 wt% CHP, 3.2 wt% DMPC, 0.4 wt% acetophenone, balance cumene.
bCE = carbinol equivalent CCPE = Cumylphenyl ether Examples 13-17: Acid-Catalyzed Composition of DCP
A stock solution containing 6 wt% DCP, 15 wt~
cumene, 1 wt~ water and 50 ppm sulfuric acid with the balance composed of equimolar phenol and acetone was distributed among several melting point capillary tubes ~7~ 6 ~13-which were subsequently sealed and heated for various lengths of time in a stirred oil bath. The tubes were then quickly cooled by immersion in an ice bath and the contents were analyzed by gas chromatography. The amount of AMS formed increased with time up to a maxi-mum yield and then declined as increased amounts of AMS
dimers and cumylphenol were formed. Table IV records the maximum AMS yield obtained at each temperature as well as the heating time required to reach that yield.
It is clear from the data of Table IV that best yields of AMS are obtained at temperatures over 100C, e.g., 120 to 150C.
TABLE IV
Acid Catalyzed Decomposition of DCP
Temperature Max. AMS Time to Max AMS
Example C mol% min 17 150 90 1.5 Example 18 Technical 83 wt% CHP~ also containing 3.4 wt%
DMPC, 0.4 wt% acetophenone and 0.3 wt~ DCP was pumped at the rate of 2 mL/min into a stirred glass vessel of 32 mL holdup capacity. A 0.4g wt% aqueous solution of sul-furic acid was also pumped into the vessel at the rate of 0.02 mL/min. Thus the resulting reaction mixture contained 1% added water and 49 ppm sulfuric acid;
residence time was 16 min. Temperature in the vessel was maintained at 75C. The reactor effluent contained 2.7 wt% CHP, 0.72 wt% DMPC, 0.4 wt% acetophenone, 4.2 wt% DCP, 0.47 wt% AMS and minor amounts of cumylphenyl ether~ AMS dimers and cumylphenol. The reactor effluent was fed through a 150 cm long coiled polytetrafluoro-ethylene tube immersed in a bath at 75C. Residence time was 2,6 min. The effluent from the tube contained 0.14% CHP; the other components remained relatively : . :
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~ ~7~361~i unchanged. The tube effluen~ was next fed through a coiled 2.2 mm inside diameter stainless steel tube immersed in a bath at 130C. Residence time was 1.5 min. The effluent was cooled by passage through a coiled 2.2 mm inside diameter stainless steel tube immersed in cold water. The final product contained 2.~4 wt % AMS, 0.4 wt % acetophenone, 0.23 wt % DMPC, 0.1 wt % DCP, 0.16 wt % AMS dimers and 0.33% cumylphenol; the balance of the other components analyzed by gas chroma-tography was phenol, acetone and cumene. Short pathdistillation of 100 g of the final product at 110C and 2.67 kPa (20 mm mercury) left a residue of 1.60 g.
Example 19 (Comparative) The experiment of Example 18 was repeated with the following modifications: no water was added to the reactor and the polytetrafluoroethylene tube was shortened to 25 cm and maintained at room temperature; residence in the 2.2 mm inside diameter stainless steel tube was 1 min and the temperature was 115C. The stirred reactor 20 effluent contained 0.10 wt % CHP, 0.4 wt % acetophenone, 0.34 wt % DMPC, 1.43 wt % AMS, 0.91 wt % DCP, 0.51 wt ~
AMS dimers and 0.4 wt % cumylphenol. The final product contained 2.02 wt % AMS, 0.4 wt % acetophenone, 0.16 wt % DMPC, 0.60 wt ~ AMS dimers and 0.78 wt % cumylphenol;
the balance of the components analyzed by gas chroma-tography was phenol, acetone and cumene. Short path distillation of 100 g of final product at 110C and 2.67 kPa left a residue of 2.63 g.
Gas Chromatography Analysis of CHP Decomposition Mixture A 2 ft. (61 cm) x 2 mm inside diameter Pyrex~
column packed with 3% QF-l and 3% OV-17 on 80-100 mesh high performance Chromosorb W~ was used. The column packing was obtained from Applied Science Laboratories Inc. The column was held at 50C for 1 min., then 35 heated at 5C/min. to 180C and held at 180C for 3 min. Injection temperature was 150C. Helium was used as carrier gas at 40 mL/min. Elution times were as follows (in min): cumene, 1.6: AMS, 2.3; phenol, 3-5;
,~ ~, DMPC, 5.2; acetophenone, 5.7; CHP, 7.6; hexamethyl ben-zene (as internal standard), 11.9; cumylphenyl ether, 16.1; AMS dimers, four peaks of area ratio equal to 0.05/0.20/1.00/0.23, correspondingly at 17.6, 18.6, 19.5 and 20.2; DCP, 20.2; cumylphenol, 22.6. In deter-mining the amount of DCP, a correction was applied for contribution of AMS dimers to that peak due to the over-lap of DCP and the last dimer peaks. DCP determinakion was quite reliable down to 0.1 wt% DCP.

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Claims

What is claimed is:

1. A process of decomposing a cumeme oxida-tion product mixture containing cumene hydroperoxide (CHP) and dimethylphenylcarbinol (DMPC) to produce phenol, acetone and alpha-methyl styrene (AMS) with reduced by-product formation which comprises the steps:
a) mixing the cumene oxidation product with an acid catalyst in a back-mix reactor in the presence of about 0.4 to about 4.5% water, by weight of reaction mixture, at a temperature between about 50°C
and about 90°C for a time sufficient to lower the CHP
concentration of the back-mix reaction mixture to between about 0.5 and about 5.0 weight % and to convert at least 40% of the DMPC in the cumene oxidation product to dicumylperoxide (DCP);
b) reacting the back-mix reaction mixture at between about 50°C and about 90°C under plug flow conditions for a time sufficient to produce a second mixture having a CHP concentration no more than about 0.4%; and c) reacting the second reaction mixture at a temperature between about 120 and about 150°C under plug flow conditions for a time sufficient to convert at least 90% of the DCP to AMS, phenol and acetone.

2. The process of claim 1 wherein the back-mix reaction mixture contains about 0.8 to 1.5% water and about 30 to about 100 ppm sulfur dioxide or sulfuric acid and is at between about 60 and about 80°C.

3. The process of claim 1 wherein the time for step b is sufficient to lower the CHP concentration to no more than about 0.2%.

4. The process of claim 1 wherein the product from step b is heated to the temperature of step c in under 30 seconds and then maintained at that temperature for at least 30 additional seconds.

5. The process of claim 1 further comprising the step:
d) measuring the DCP concentration during said step c and cooling the reaction mixture to below 100°C to stop the reaction when about 0.5 to about 5% of the DCP in the second mixture remains unconverted.