MXPA00006676A - Process for the preparation of phenol - Google Patents

Abstract

A process for the production of phenol by the Hock cleavage of aryl hydroperoxides involves the oxidation of a mixture containing cumene (I) and cyclohexyl-benzene (II) in a wt. ratio (I/II) of at least 3:1 with the aid of oxygen-containing gas, followed by cleavage of the resulting hydroperoxides of (I) and (II)to give phenol, acetone and cyclohexanone.

Description

PROCEDURE FOR THE OBTAINING OF FENOL The invention relates to a process for obtaining phenol by means of the Hock dissociation of aryl hydroperoxides. Within the scope of the present invention, "aryl hydroperoxides" are understood to mean all hydroperoxides in which Hock dissociation yields phenol. Phenol is an important chemical raw material with a wide range of. Applications. In addition to its use as a solvent, phenol is used, among other things, to obtain phenol resins, bisphenol-A, e-caprolactam, adipic acid, alkylphenols and plasticizers. It is known to obtain phenol by Hock dissociation of a suitable hydroperoxide. In this, in addition to phenol as a hydroxy compound, a carbonyl compound is always obtained as a coupled product which, for economic reasons, must also be able to be supplied to a suitable holding. Patent document FR-1 030 020 teaches the oxidation of cyclohexylbenzene with oxygen or air to obtain cyclohexylbenzene hydroperoxide and its subsequent Hock dissociation to obtain phenol and cyclohexanone. This is also an interesting valuable product, which can be used, for example, as a solvent or for obtaining adipic acid and cyclohexanone oxime, which is required for the production of. e-caprolactam. In the other patent literature related to this process the oxidation of cyclohexylbenzene with air or oxygen to obtain cyclohexylbenzene hydroperoxide is described, at temperatures between 60 ° C and 200 ° C under normal pressure or overpressure, with and without catalyst. While the patent documents EP-0 037 167 describe the use of alkylamines of 14 to 16 carbon atoms, straight chain, or polyvinylpyrrolidone as a catalyst for the oxidation of cyclohexylbenzene, in patent documents FR-1 030 020 and BE-551 908 the oxidation is also described without catalyst. US Pat. No. 4,299,991 describes the oxidation of cyclohexylbenzene in the presence of a polymaleimide catalyst. According to FR-1 030 020, the dissociation of phenol and cyclohexanone from the cyclohexylhydroperoxide obtained through the oxidation of cyclohexylbenzene can be carried out with cyclohexylbenzene as an acid catalyzed solvent by benzenesulfonic acid or sulfuric acid. According to US Patent 4 246 203, the dissociation of cyclohexylbenzene hydroperoxide can also be carried out at temperatures of 120 to 200 ° C, in the presence of 50 to 2'000 ppm of sulfuric acid, taking advantage of the heat released from the reaction directly to evaporate phenol and cyclohexanone. A series of new patent documents from the company Phillips describes improved dissociation catalysts compared to aqueous acid catalysts, which avoid the disadvantage of the subsequent neutralization of the product flow always linked to the acid catalysts, which can affect its further processing . Thus, US Pat. No. 4,487,970 teaches the use of SbF5 and graphite as catalysts, while US Pat. No. 4,480,141, on the other hand, uses BF3 x H3P0 and US Pat. No. 4,482,757 an organic phosphonium halogenide of the formula R4PX and an acid such as hydrochloric acid, sulfuric acid or phosphoric acid. Finally, US Pat. No. 4,532,360 teaches a direct one-stage process for obtaining, for example, phenol and cyclohexanone starting from cyclohexylbenzene, in the presence of hydrogen bromide or hydrogen chloride and at least one additive selected from the group consisting of by cerium oxide, triphenyl borate, boron triphosphate and water. However, at present phenol is obtained mainly by Hock dissociation of cumol hydroperoxide. In this so-called cumol procedure, cumol is first oxidized preferably with air or oxygen to obtain cumene hydroperoxidewhich, normally after a concentration by distillation by dissociation of the cumol which did not react until having a content of cumol hydroperoxide of 60 to 85% by weight, is then dissociated with acid catalysts, preferably sulfuric acid, to obtain phenol and acetone. For example, eissermel / Arpe, Industrielle Organische Chemie, 2a. edition, Verlag Chemie, 1978 or Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 19, p. 302 et seq., VCH Verlagsgesellschaft, 1991, provide a good overview of the cumol procedure. New developments thereof relate mainly to the field of dissociation of the cumol hydroperoxide and to the processing of the dissociation product to reduce the formation of secondary products and the consumption of energy. See, for example, EP-0 589 588 Al, EP-0 670 296 Al or WO 97/06905. The cumol process always produces equal portions in the molar aspect in the production of phenol and acetone. Regarding the weight, 0.62 tons of acetone are produced per ton of phenol. An essential application of both products is the synthesis of bisphenol-A, in which, according to the reaction equation, starting from 2 moles of phenol and 1 mole of acetone, 1 mole of bisphenol-A is produced. This serves as a starting substance for the preparation of polycarbonates and epoxy resins and, therefore, is produced in large quantities. However, from the molar point of view, for the synthesis of bisphenol-A, only half the amount of acetone is required than that of phenol. Although acetone also has other applications, for example, as solvent or for obtaining, for example, methyl methacrylate, a different market growth for phenol is generally predicted than for acetone, so that, from the molar aspect, it will be required a little more phenol than acetone. However, the cumol procedure, due to its reaction scheme, can not meet this different market requirement. Thus, the aim is to provide a process for obtaining phenol, which, although it also produces acetone, allows in an economically advantageous way a flexible adjustment of the production to a higher molar demand of phenol than of acetone. This object is achieved according to the invention according to claim 1, by means of a process for obtaining phenol by means of the Hock dissociation of aryl hydroperoxides, which is characterized in that a mixture containing cumol and cyclohexylbenzene in a weight ratio of cumol to cyclohexylbenzene of at least 3: 1, "is oxidized with a gas containing molecular oxygen, and the obtained cumol and cyclohexylbenzene hydroperoxide is dissociated to obtain phenol, acetone and cyclohexanone. found now that, with the aid of the process steps known from the cumol process, not only can cyclohexylbenzene be treated to obtain phenol and cyclohexanone, but also that mixtures containing cumol and cyclohexylbenzene can be used as starting material, In this way, they can be converted together into phenol, acetone and cyclohexanone. By adjusting the composition of the educts mixture with respect to the content of cumol and cyclohexylbenzene, the molar ratio of phenol: acetone: cyclohexanone can be controlled directly in the product mixture, and a non-commercial excess of one of the two carbonyl compounds that are formed. The process according to the invention thus offers the great advantage of being able to adjust the production to the markets for the valuable products phenol, acetone and cyclohexanone, being able in particular to avoid the predicted overcapacity of acetone. Also, the process according to the invention offers the advantage that, by using mixtures of educts containing cumol and cyclohexylbenzene, one can have a positive influence on the reaction rate of pure cyclohexylbenzene oxidation, which is lower compared to the oxidation of pure cumol. Since the reaction according to the invention of the mixture containing cumol and cyclohexylbenzene can take place under the conditions known from the usual cumol method, the process according to the invention can be carried out quickly and easily. In the realization in the area of oxidation and dissociation, preferential parts of already existing installations are used; only adjustments are required in the feed of the educts and, especially, in the processing of the flow of the dissociation product to obtain the certain valuable products. For this reason, an existing production facility for phenol and acetone, which works according to the usual cumol process, can be easily extended, so that it is suitable for carrying out the process according to the invention, and which, according to the market conditions, may operate in accordance with the invention or solely for the production of phenol and acetone. A mixture having a weight ratio of cumol to cyclohexylbenzene of at least 3: 1, preferably from 5: 1 to 9: 1 serves as starting material for the process according to the invention. This mixture can already be kept in storage tanks or formed just before entry to the oxidation reactors, mixing from different sources. It is also possible to separately dose the reactors of oxidation flows of substance containing cumol or cyclohexylbenzene and mix them there. The bubbling column reactors known from the cumol process are preferably used as oxidation reactors. The oxidation takes place analogously to the same, preferably without catalyst, at temperatures of 100 ° C to 140 ° C and absolute pressures of 1 to 20 bar, in the presence of, preferably, air or oxygen as a gas containing molecular oxygen, up to usually achieve a total content of maximum 35% by weight of peroxides in the product flow rate of the oxidation. The remainder includes mainly cumol 'and cyclshexylbenzene which did not react, since a largely pure cumol / cyclohexylbenzene mixture is preferably used. In addition, some secondary products that were formed with oxidation are contained in small quantities. These include in particular dimethylphenylcarbinol, phenylisohexanol-1, acetophenone and caprofenone. As in the usual cumol process, the product flow rate of the oxidation can be supplied either directly or via an intermediate storage tank, to a concentrator unit in which, preferably by vacuum distillation routes, by dissociation of cumol and / or unreacted cyclohexylbenzene, the content of cumol hydroperoxide is preferably increased to 30 to 60% by weight and / or cyclohexylbenzene hydroperoxide is preferably increased to 5 to 20% by weight in the substance flow rate. The dissociated cumol and / or cyclohexylbenzene is preferably fed back to the oxidation, if necessary after processing. The flow rate of the substance of the concentration is supplied to the cleavage, which, according to the invention, preferably takes place with acid catalysts, in particular by sulfuric acid, in a homogeneous phase. At this time, the cumol hydroperoxide and the cyclohexylbenzene hydroperoxide are essentially converted to phenol, acetone and cyclohexanone. Dissociation reactors and suitable reaction conditions are known, for example, from EP-0 589 588 Al or WO 97/06905. It may be advantageous, analogously to the process in said documents, to subject the dissociation product to a later tempering to reduce the content of unwanted by-products, which affect the yield. Subsequently, a preferential processing of distillation of the dissociation product mixture, in a manner known to those skilled in the art and analogous to the cumol process, is carried out to isolate the valuable products phenol, acetone and cyclohexanone. The process according to the invention is not limited to the main process steps described herein; rather all the variants of procedure, complements and ramifications known of the procedure cumol, especially when they are oriented to reduce the formation of secondary products and to optimize the energy consumption, they can also be transferred to the process according to the invention. Knowing this one and based on the cumol procedure, a great diversity of designs of the process technique and of the apparatuses opens up to the expert in the matter. With the aid of the process according to the invention, dissociation yields of phenol, acetone and cyclohexanone of more than 90% can be achieved. The composition of the educts mixture used in the oxidation is preferably adjusted so that its content of cyclohexylbenzene is preferably such that for the valuable products acetone and cyclohexanone, which are formed as coupling products of the phenol, there are respectively sufficient market possibilities. In this way losses due to overcapacities are avoided and high economic performance is achieved. The method according to the invention is illustrated in more detail by the following example, without being limited thereto.

Example: A mixture consisting of 75% by weight of cumol and 25% by weight of cyclohexylbenzene is oxidized at 132 ° C with oxygen in a thermostable bubble column reactor. After an oxidation time of 3 hours, the oxidation contains, according to the analysis with a gas chromatograph (GC analysis), 24.5% by weight of cumol hydroperoxide and 8.2% by weight of cyclohexylbenzene hydroperoxide. This mixture is then subjected to a high vacuum concentration, wherein the concentrate that is produced contains 38.3% by weight of cumol hydroperoxide and 13.1% by weight of cyclohexylbenzene hydroperoxide. The hydrocarbon mixture produced as a distillate contains less than 1% by weight of peroxide, calculated as cumol hydroperoxide. The concentrate is then subjected to a dissociation of a phase at 50 ° C, in the presence of 2000 ppm of sulfuric acid, dissolved in acetone or dissociated in an assay dissociation product consisting of acetone, MEK, phenol and the hydrocarbons. The dissociation yield after the evaluation of the GC analysis is, for acetone, of more than 95%, for ciciohexanone, of 80.8% and for phenol, of 91.5%.

Claims (9)

1. A process for obtaining phenol by dissociating Hock from aryl hydroperoxides, characterized in that a mixture containing cumol and cyclohexylbenzene in a mixture ratio of cumol to cyclohexylbenzene of at least 3: 1, is oxidized with a gas containing Molecular oxygen and the cumol hydroperoxide and cyclohexylbenzene produced are dissociated to obtain phenol, acetone and cyclohexanone.

2. A process according to claim 1, characterized in that the weight ratio of cumol / cyclohexylbenzene in the mixture is from 5: 1 to 9: 1.

3. A process according to at least one of the preceding claims, characterized in that the oxidation is carried out with air or with oxygen as a gas containing molecular oxygen.

4. A process according to at least one of the preceding claims, characterized in that the oxidation is carried out at temperatures of 100 ° C to 140 ° C.

5. A process according to at least one of the preceding claims, characterized in that the oxidized is concentrated distillatively before dissociation, by separation of cumol or cyclohexylbenzene or both.

6. A process according to claim 5, characterized in that the separated cumol or the separated cyclohexylbenzene or both are fed back to the oxidation.

7. A process according to at least one of the preceding claims, characterized in that the dissociation mixture is homogeneous.

8. A process according to at least one of the preceding claims, characterized in that the cleavage is catalyzed with acids.

9. A process according to claim 8, characterized in that sulfuric acid is used as the acid.