FI112362B - A process for the preparation of cumene hydroperoxide - Google Patents

Description

112362

Process for the preparation of cumene hydroperoxide - Förfarande för framställning av cumenhydroperoxid

The present invention relates to the preparation of phenol from cumene.

More particularly, the present invention relates to a first step of the process, i.e. to the provision of cumene hydroperoxide.

The preparation of phenol from cumene is a well-known industrial process which is carried out continuously and comprises essentially two steps.

In the first, in the liquid phase, cumene is oxidized to cumene hydroperoxide using an oxygen-containing gas. The hydroperoxide thus obtained is then decomposed in a second step into phenol and acetone.

The hydroperoxide formed must be concentrated before this final step. For reasons of efficiency and safety of the process, oxidation reactions of cumene are not performed when the hydroperoxide concentration in the reaction is above a certain level. The reason is that it is desired to prevent premature decomposition of the formed hydroperoxide, which may become uncontrolled. Usually the concentration of hydroperox is less than 40% by weight of the reaction mixture, therefore a previous concentration step before the phenol step is required.

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During the first step of the process, cumene hydroperoxide is formed at the same time as various by-products which are, in particular, dimethylphenylcarbinol, dicumylperoxide, acetophenone as well as phenol and organic acids. The presence of these latter compounds is known for the reaction: extremely harmful. Namely, these acids promote the decomposition of hydroperoxide to phenol, which itself is an oxidation reaction! inhibitor.

'; Therefore, there are a number of methods which recommend the oxidation reaction of cumene with various additives. 5 cide, an alkali metal carbonate and an alkali metal salt of cumene hydroperoxide.

In the first type of processes for the preparation of cumene hydroperoxide, a reaction is performed when a neutralizing agent is present in a few 10%. However, these processes have the disadvantage that relatively large amounts of such substances have to be used.

On the other hand, these amounts significantly increase the raw material cost of the process.

On the other hand, they require the use of additional material before the cumene hydroperoxide concentration step. It will be recalled that the use of this type of additive results in the formation of alkali metal salts which must be removed from the reaction mixture prior to the concentration step in order to avoid the equipment becoming hot during this concentration step. This is again not possible except by washing the reaction mixture once or more. min. In addition, such a method requires a pre-concentration step of the washed reaction mixture prior to the actual hydroperoxide converter; · Centering step.

One way to remove alkali metal salts may be by filtration of the i:: reaction mixture. Furthermore, the amounts of agents used in the known methods 30 prevent such a method. use at the industrial level, since the filters become very rapidly carded due to the deposition of salts and thus become unusable. In addition, this separation step is highly sensitive, since the drained salts are viscous in consistency and make filtration itself more difficult, as well as subsequent cleaning of the filters.

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In addition, safety concerns may arise as these salts are unstable and may spontaneously ignite when exposed to air.

In another type of process for the preparation of cumene hydroperox, a neutralizing agent is used which is used in a few hundred parts per million relative to the amount of cumene present in the medium. Such a method is described in particular in Japanese Patent Application JP-3287574. However, in this process 10, high pressure is used.

In another known method of making cumene hydroperox, the oxidation of cumene is carried out without the addition of a neutralizing agent. However, during the reaction, the acidity li-15 is regulated in the one or more reactors used, and it is therefore advisable to modify some aspects of the operation of the process to make the reaction conditions more favorable. For example, the temperature may be lowered while all other parameters of the reaction remain unchanged, but the difficulty is the slowing of the oxidation rate and hence the reduction in the productivity of the process. Another possible way would be to increase the temperature to maintain good productivity. But again this would lead to a loss of selectivity and probably also of safety due to premature degradation of the cumene hydroperoxide being produced.

Problems in controlling the temperature of the hydroperoxide production reaction are specifically addressed in European Patent Application EP-32758. When the temperature deviation is constant at 30, it is advisable to add 0.05 to 20 g of basic substance per ton of reaction mixture. Further, it is disclosed that it is preferable to lower the temperature of the reaction sequence. However, this reference does not specifically refer to providing ethylbenzene hydroperoxide, a compound which is not as readily reactive as cumene.

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It is therefore an object of the present invention to overcome the drawbacks of the known processes relating to the above-mentioned phenol production from cumenes, in particular those related to the oxidation step of cumene. The process of the invention achieves said oxidation reaction at good oxidation rates without even temporarily resorting to conditions unfavorable to productivity. In addition, the process of the invention solves the problems of carding with filters placed before the hydroperoxy-10 concentration step formed.

These and other objects are achieved by the present invention, which relates to a process for the continuous preparation of cumene hydroperoxide by oxidation in a liquid phase of a reaction mixture comprising cumene in the presence of an oxygen containing gas. The process is characterized in that it undergoes an oxidation reaction in the presence of at least one of the following: hydroxide, alkali metal and / or alkaline earth metal carbonate. This material is used in an amount of 2-10 to 20 ppb (expressed as sodium hydroxide) of the amount of cumene added.

It has been surprisingly found that amounts as small as the above are sufficient to keep the oxidation conditions suitable for industrial production. By way of comparison, the concentrations of the neutralizing agents used in the reaction mixture were considerably higher in the prior art, as they typically have a concentration of 0.1% to a few percent.

30 Furthermore, the presence of the substance in question does not allow the circumstances. in order to remain functionally stable, it is necessary to change the reaction parameters but simply to adjust the amount of the neutralizing agent.

35 Other advantages and characteristics are clearly set forth below:. the following explanations and examples.

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As already mentioned above, the process for preparing phenol from cumene has two main steps, the oxidation of cumene to hydroperoxide and then decomposition of said peroxide into a mixture of acetone and phenol.

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The six oxidation reactions are usually carried out in one or more devices (oxidants) in series. More specifically, it is implemented on two to eight devices.

The reaction mixture from the latest oxidant is treated to remove minor amounts of alkali metal salts therein. Any method known to those skilled in the art can be used. However, it is particularly advantageous to separate the salts from the reaction mixture using any of the filtration methods.

Finally, the reaction mixture is treated so as to separate, on the one hand, the unreacted cumene of the cumene hydroperoxide and, on the other hand, concentrate said peroxide so that the concentration of the effluent is about 80-85%.

This operation may be performed in one or more steps. Conventionally, the vacuum filtration principle is used, with one or more fractional columns.

25: The concentrated hydroperoxide stream is then decomposed to phenol and 'acetone.

<t ♦> J 'During the first step of the process, the oxidation of cumene 30 with oxygen-containing gas is carried out in one or more steps.

The cumene entering oxidants consists of partly new cumene '·' · and partly recycled cumene.

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As stated above, not all the cumene to be added is transformed into hydroperoxide. Usually the degree of transformation of cumene is 20-40%. For obvious economic reasons, in the process, unreacted cumene is recycled to a maximum of 5 times.

The amount of cumene to be recycled is not critical and can be adjusted by one skilled in the art.

Whatever the nature of the cumene (new or recycled cumene), its purity should preferably be at least 99.5%, more specifically at least 99.8%.

In addition, cumene is substantially free of acid and phenol.

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Thus, unreacted cumene is treated before being returned to the process so as to remove all impurities it contains, in particular acidic impurities.

Conventionally, one or more washing cycles of cumene are performed such that each step is followed by decantation.

Initially, the treatment is carried out with an aqueous solution of a base selected mainly from the hydroxides of the alkali or alkaline-earth metals. The concentration of these solutions is 10-20%. The cumene thus treated is then subjected to one or more washes / de-; water removal to remove any residual traces of alkali or alkaline earth metal salts.

t:: 30 In these operations, the temperature is usually 25-45 ° C.

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It should be noted that the process of the invention does not favor the formation of by-products such as phenol in particular. Thus, the concentration of the contaminants, which are found mainly in the 35 cumene wash waters, is reduced, which in turn facilitates; their cleaning.

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The oxidation reaction is carried out in the presence of an oxygen gas, any source of oxygen, pure or diluted, for example air, whether or not enriched with oxygen, may be used. Preferably, 5 air is used as the oxidant for cumene.

All oxidizers have a device for introducing oxygen-containing gas. Usually, and to optimize the quality of the liquid / gas mixture, oxygen is introduced through the oxidant base in any manner known to those skilled in the art.

The concentration of oxygen added to the reaction mixture may be at least 8%, more preferably at least 20%.

15 Generally, and for safety reasons, the oxygen content of gas from oxidants is kept below 6.5%. More specifically, the amount of oxygen is maintained in the range of 2 to 65%, more preferably in the range of 4.5 to 6.5%.

An essential feature of the invention is the addition of a hydroxide, alkali metal and / or alkaline earth metal carbonate to the oxidants; this material is used in significantly smaller amounts than in prior art, namely 2 to 10 ppb (expressed as sodium hydroxide) of added cumene.

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The additive should preferably be in the range of 2 to 5 ppb (expressed as sodium hydroxide).

i: V: The most suitable agent is a compound based on an alkali metal, especially sodium, potassium, sodium kar; i "; bonate and potassium carbonate.

The substance is contacted with the reaction mixture, preferably in the form of an aqueous solution. The concentration of the substance in the solution is such that it is maintained in the concentration range of 2 to 10 ppb (expressed as sodium hydroxide).

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The substance may be added continuously or in batches, to one or all of the oxidants. In the latter case, the total concentration of the substance in the reaction mixture is not more than 10 ppb (expressed as sodium hydroxide) of the amount of cumene added.

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The agent is injected so that the pH of the reaction mixture is maintained between 3-5.

The reaction mixture remains in all oxidants for 10-48 hours.

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The reaction temperature is in the range of 70-100 ° C. Preferably, the temperature should be 75-90 ° C.

It should be noted that, in a conventional manner, the reaction temperature 15 varies with different oxidants, and in particular that it decreases as the cumene hydroperoxide content increases.

Thus, as will be readily apparent to one skilled in the art, the possibility of premature decomposition of the peroxide is prevented and a good yield is maintained.

The oxidation reaction can be carried out at atmospheric pressure or at a slight excess pressure. The oxidation reaction can be carried out at a pressure of 1-3 absolute bar.

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After one or more oxidation steps, the reaction mixture is filtered to remove minor amounts of alkali or alkaline earth metal salts. Surprisingly, no filter shrinkage was observed due to the oxidation reaction of cumene to-30 in the presence of an alkaline or alkaline agent.

Thus, according to the method of the invention, I. uses industrial-scale filters, that is to say, • substantially multiplies the step of separating the salts of the alkali metal or alkaline earth metal from the reaction mixture.

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The reaction mixture so treated is fractionated and concentrated by vacuum distillation, carried out in one or more steps.

The cumene obtained during this distillation is recycled towards the oxidants after they have been purified according to the above process.

The concentration of the cumene lantern peroxide obtained is about 85%.

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The hydroperoxide is then decomposed to phenol and acetone under conditions well known to those skilled in the art.

The following are non-limiting concrete examples of the process of the invention.

Example

The oxidation reaction is carried out in a continuous steel reactor with a total volume of 8 liters fed with a continuous feed of a solution of washed cumene, a concentration of HPOC (cumene hydroperoxide) 0.1%, air and aqueous sodium.

The effect of stopping sodium supply is manifested by a decrease in HPOC: · a decrease in phenol and acidity: the temperature must be increased in order to maintain the productivity level.

This modification leads to a further deterioration of the reaction mass; ''.

Adding small amounts of sodium: about 5 ppb of 100% sodium is enough to get back to the normal oxidation profile. This makes the unit perform significantly more reliably without impairing the performance (concentration and filtration) of the above devices.

35 The results are shown in the following table: i * 10 112362

Time-Ku-Nat-T HPOC pH Fe-Hap-02 field (h) arsenic (° C) (%) nol pa- (%) (kg / h) (mg / h) (ppm) other (ppm) 0-62 0.1 5.10 4 78.2 30.1 3.6 4 30 6.2 62-124 0.1 0 80 29.5 - 4 30 6.2 124-186 0.1 0 80.6 27 , 3 3.3 28 55 6.5 186-248 0.1 5.10'4 78.3 27.9 3.9 8 30 6.0 248-310 0.1 5.10-4 78 29 3.8 4 25 5 , 8 j * * 1 tt

Claims (8)

A process for the continuous production of cumene hydroxide by oxidizing a reaction mixture comprising the cum in the liquid phase in the presence of a gas containing oxygen, characterized in that an oxidation reaction is carried out when at least one substance is present which is hydroxide or carbonate. of alkali and / or alkaline earth metal; said substance being used in an amount comprising 2-10 ppb (expressed as sodium hydroxide) of the amount of cum feed. 10 Process according to Claim 1, characterized in that the substance is used in an amount comprising 2-5 ppb (expressed as sodium hydroxide) of the amount of cum feed. Process according to any one of the preceding claims, characterized in that a substance which is sodium carbonate or potassium carbonate is used. 4. A method according to any preceding claim, characterized in that a cumen stream is used, the purity of which is at least edible. 99.5%, preferably at least 99.8. • i Method according to any of the preceding claims, characterized in that a cumen stream is used, which essentially does not! contains acid or phenol. • »« ♦ * t !!! 6. A process according to any preceding claim, characterized in that a reaction mixture is used which comprises at least 8%, preferably at least 20% oxygen. 25 Process according to any one of the preceding claims, characterized in that the reaction is carried out where the temperature is 75-120 ° C, preferably 75-110 ° C. * »» ». 8. Use of hydroperoxide obtained using. the process according to any of claims 1-7 for the preparation of phenol.