DE1518967B2 - Process for the production of styrenes - Google Patents

Description

Propylene oxide and similar epoxy compounds are valuable starting materials for the chemical industry. The same also applies to styrene itself and corresponding other styrene compounds - such as substituted styrenes.

Propylene oxide is currently largely produced from propylene using the so-called chlorohydrin process manufactured. This requires chlorine as one of the main raw materials. This chlorine is thereby in a The salt of the hydrochloric acid was transferred, which ruled out the economic recycling of chlorine is. This process for the production of propylene oxide is therefore much less favorable than that the manufacture of ethylene oxide, which is made using ethylene and oxygen as the essentials Starting materials can be produced. In addition to propylene oxide, there are other epoxy compounds, which are also valuable commercial products, for example epoxides of unsaturated esters and Alcohols as well as service.

It is also already known that lower olefins, such as propylene, using peracids, how peracetic acid can be converted into the corresponding epoxides as an epoxidizing agent (FR-PS 12 25 155). However, such methods have several disadvantages.

Handling peracids is very dangerous, and the associated risks require special precautions that complicate the operation of the process. In addition, peracids have a corrosive effect and cannot be regenerated, as hydrogen peroxide does as water is lost. The epoxidation mixture obtained with peracids contains substances (water, Acetic acid), which react very easily with the epoxides formed and thereby numerous by-products, such as Glycol, glycol monoesters and glycol diesters, which limit the efficiency of the process. These disadvantages are particularly serious in the case of the less reactive olefins, particularly propylene.

For the reasons given above, attempts have been made to use hydrogen peroxide for epoxidations to make usable (US-PS 28 33 787). From US-PS 27 86 854 it was known that epoxides of Olefins can be obtained with hydrogen peroxide if the reaction mixture is not heated to above 100 ° C is, as long as the catalyst is not yet completely separated, or if in the case of using a Hydroxyolefins a neutral salt of tungstic acid is used.

Appropriate tests have shown, however, that hydrogen peroxide is unable to effect the epoxidation of olefins such as propylene. In addition, hydrogen peroxide has the disadvantage that it cannot be regenerated and that water is formed when it is used, which causes product losses. More recent work has the epoxidation of α, β-ethylenic _: unsaturated ketones and aldehydes with organic hydroperoxides at carefully controlled

to pH conditions on the subject. However, this mode of operation is only extremely reactive on substituted ones Olefins can be used (US Pat. No. 3,013,024 and 3,062,841).

In the further known epoxidation of relatively reactive olefins with higher Molecular weight with an organohydroperoxide in the presence of vanadium pentoxide as a catalyst relatively low yields were obtained. So was the yield of cyclohexene oxide from cyclohexene and cumene hydroperoxide 36% and the yield of epoxy octane from the less reactive octene-1 and Cumohydroperoxide only 14%. When reacting cyclohexene with cumene hydroperoxide in the presence of Osmium tetroxide could not be isolated from the products any epoxide (J. Chem. Soc, 1950, 2169).

In DE-PS 14 68 012 a process for the production of epoxy compounds by oxidation of a epoxidizable low molecular weight olefinically unsaturated compound with an organohydroperoxide in The presence of catalytic amounts of epoxidation catalysts described, which consists in being as Catalysts hydrocarbon-soluble organometallic compounds of vanadium, molybdenum and / or Tungsten or carbonyls of these metals are used. A corresponding procedure can also be found in DE-PS 14 68 025, with the exception of inorganic molybdenum compounds as catalysts the carbonyls of molybdenum. These procedures are also used in the first stage of the applied in the present proceedings, namely in the

-to manufacture of epoxides from olefinically unsaturated Compounds with 3 to 30 carbon atoms.

This based on the use of Arälkylhydroperoxiden as oxidizing agent results in the desired epoxides now in high conversion and selectivity and avoiding the other Process for making epoxies inherent disadvantages. The aralkyl hydroperoxides required for this are inevitably reduced to the corresponding arylalkanols, so that in the epoxidation reaction mixture large amounts of these by-products are also included. A recovery and purification of the respective arylalkanol from the Reaction mixture is usually not very attractive, as it is related to directly marketable products high purity requirements are made.

The same also applies with regard to the possibility of converting the respective alcohol into the corresponding alcohol by dehydration To transfer ketone, which is of course possible in principle. The resulting aryl alcohol could be

to such epoxidation processes, however, to a certain extent can also be recycled by first converting it to the corresponding arylalkyl hydrocarbon hydrogenated and this then by air oxidation into the arylalkyl hydroperoxide required as an epoxidizing agent

f> 5 transferred. Such an overall procedure would then practically no by-product at all, but only hydrogen to reduce the Consumed alcohol. Such a mode of operation

seems very attractive at first, but still does not represent an optimal utilization option for the arylalkanol obtained as a by-product in such epoxidation processes. In addition, there would be greater 'flexibility with regard to the possible uses of the arylalkanols formed in> epoxidations using aralkylhydroperoxides and the management of such Procedure very welcome. Above all, it would be useful if this by-product, which is not always attractive, could be converted in a simple manner into a valuable and easily marketable other product.

The invention therefore relates to a process for the preparation of styrene by dehydration of the corresponding aryl alcohols, which is characterized in that an, as aryl alcohol by reacting a Aralkylhydroperoxids with a epoxidizable olefinically unsaturated compound having 3 to 30 carbon atoms at from -20 to 200 ⁰ C, if appropriate, in the presence of a solvent, in the presence of compounds of vanadium, molybdenum or tungsten as a catalyst and separation

,. of the epoxide obtained aryl alcohol formed verwen- V det.

The process according to the invention enables a particularly flexible design of the epoxidation process of olefins by means of arylalkyl hydroperoxides and the simultaneous formation are particularly useful Products, namely of styrene or substituted styrenes, normally used as monomers for manufacture of polystyrenes and corresponding copolymers thereof are used.

The temperatures which can be used in the epoxidation can vary widely depending on the reactivity and other characteristics of the other reactants. It is carried out at temperatures of -20 to +200 ⁰ C, preferably from 40 to 150 ⁰ C and in particular from 60 to 120 ⁰ C. The reaction is carried out at a pressure which is sufficient to maintain a liquid reaction phase. Although it is possible to work at negative pressures, pressures of about atmospheric pressure up to 71 bar are generally preferred.
The epoxidation catalyst is used in an amount

: J used, which is at least sufficient to 0.0ImMoI To supply molybdenum or an equivalent catalytically active substance per mole of A-arylalkyl peroxide. It is preferred to use 0.02 to 40 mmol, in particular 0.1 to 4.0 mmol, of catalyst. Usable Molybdenum compounds include the organic molybdenum salts, the oxides, such as MO2O3, MOO2, molybdic acid, the molybdenum chlorides and oxychlorides, molybdenum fluoride, phosphate or sulphide. One can also use heteropoly acids of molybdenum and their salts. Examples include Phosphomolybdic acid and its sodium and potassium salts.

The arylalkyl hydroperoxides required as epoxidizing agents are made from alkyl aromatic hydrocarbons with at least one hydrogen atom on a carbon atom attached to the ring obtain. The aromatic nucleus can be a benzene or naphthalene nucleus, the one or carries several optionally branched side chains with up to 12 carbon atoms per chain. Examples of suitable arylalkyl hydroperoxides are the hydroperoxides of ethylbenzene, cumene, p-ethyltoluene, Isobutylbenzene, diisopropylbenzene, or p-isopropyltoluene. Cumene hydroperoxide and ethylbenzene hydroperoxide are preferred.

For the practical implementation of the epoxidation process, catalytically active components can be used in The form of a compound or mixture can be used which is initially soluble in the reaction medium is. The solubility depends to a certain extent on the reaction medium used in the individual case. Suitable Soluble substances are, for example, the hydrocarbon-soluble organometallic compounds with a solubility in methanol of at least 0.1 g / l at room temperature. Examples of soluble forms of the catalytically active substances are the naphthenates, stearates, octoates and carbonyls specified Metals. Various chelates, addition compounds, and enol salts such as acetoacetonate can can also be used. Preferred catalysts are the naphthenates and carbonyls of molybdenum, Vanadium and tungsten.

The duration of the epoxidation reaction depends on the conversion desired. Very short response times on the order of less than 1 minute can be applied when dealing with low Degree of conversion and / or very active substances works. Usually response times of Applied for about 1 minute to 10 hours and more often from 5 minutes to 4 hours.

Epoxiesable olefinically unsaturated compounds that can be used in the present process include substituted and unsubstituted aliphatic and alicyclic olefins, the hydrocarbons, esters, Alcohols, ketones or ethers with 3 to 30 carbon atoms can be. Examples of such olefins are Propylene, butylene, isobutylene, the pentenes, the methylpentenes, the hexenes, the octenes, the dodecenes, Cyclohexene, methylcyclohexene, 1,3-butadiene, styrene, methylstyrene, vinyltoluene, vinylcyclohexene or the Phenylcyclohexenes, olefins with substituents that contain, for example, halogen or oxygen, can also be used. Examples of such substituted olefins are allyl alcohol, methallyl alcohol, Cyclohexeriol, diallyl ether, methyl methacrylate, methyl oleate, methyl vinyl ketone or allyl chloride. The lower olefins with 3 to 4 carbon atoms in one are particularly advantageous aliphatic chain epoxidized by the present process. ■. .

The ratio of olefins to arylalkyl hydroperoxides in general, the epoxidation reaction can vary over a wide range. in the Generally, olefin to hydroperoxide molar ratios of about 1:15 to 20: 1 are preferred 1: 1 to 10: 1, and in particular 2: 1 to 5: 1, are used.

The concentration of arylalkyl hydroperoxide in the epoxidation reaction mixture is at the beginning of the Implementation usually at 1% or above, but lower concentrations can be used with good Effect can be applied: '

The epoxidation can be carried out in the presence of a solvent, which in general is appropriate. In most cases, aqueous solvents cannot be used. Suitable for this Solvents are hydrocarbons, namely aliphatic, aromatic or naphthenic hydrocarbons and their oxygenated derivatives. Alcohols, ketones, ethers and esters are particularly beneficial, and the presence of alcohols or ketones has an effect

often beneficial even when the solvent consists primarily of a hydrocarbon. the Use of ethyl acetate, tert-butyl alcohol, Is cumyl alcohol, alpha-phenylethanol and acetone particularly favorable, and tert-butanol is the preferred solvent.

The dehydration of the arylalkanol obtained as a coproduct in the epoxidation to styrene or an appropriately substituted styrene is generally carried out in the presence of a dehydration catalyst. This catalyst can be used in a supported form or in the form of granules or pellets. Examples of suitable carrier materials are crushed sandstone, silicon dioxide, filter stone and molten aluminum oxide bound by ceramic processes. To prepare a suitable catalyst, one can wet the carrier with water, then apply titania powder in an amount of about 10 to 15% of the carrier and the whole then allowed to dry at 150 ⁰ C. The activity of the titanium dioxide can be increased by treatment with aqueous sulfuric acid (e.g. 10%) and subsequent washing with water to remove the acid before the titanium dioxide is applied to the support. A production rate of 400 to 650 g of styrene per liter of catalyst per hour can be achieved with titanium dioxide on a molten aluminum oxide with a particle size of about 3 to 5 mm which is bound by ceramic processes as a carrier. Higher production speeds can be achieved with the titanium dioxide catalyst in granular form, for example with a catalyst which is produced as follows: Chemically pure, powdery anhydrous titanium dioxide is wetted with water and the paste obtained is ^{dried at 130 to 150 °} C., whereupon the dried product is pulverized and is then pelletized. The pellets or grains are then burned in a furnace at a temperature of at least 800 ^° C., as a result of which they acquire high mechanical strength. They can then an activation stage during about 90 minutes, washing with water and drying, are subjected to at about 130 to 150 ⁰ C by immersion in boiling aqueous nitric acid (concentration 18 to 20%). For this acid treatment, hydrochloric acid, phosphoric acid or sulfuric acid can also be used instead of nitric acid. The pellets shrink between 800 and 1000 ^° C., making them harder and denser. These denser, harder pellets apparently cannot be activated by nitric acid as easily as those ^{fired at 800 °} C., even if concentrated nitric acid is used. However, they can be activated by aqueous phosphoric acid at a concentration of 20%. Since the formation of dust in the catalyst is largely eliminated in the case of the denser, harder pellets, a roasting temperature of around 1000 ° C. is preferred.

ίο In general the relation of production is so higher, the smaller the grain size. Grain sizes of less than 4.7 mm largest dimension are off not well suited for mechanical reasons. Good production conditions are achieved with grains that measure up to 9.5 mm in one or more directions.

Cheap dehydration temperatures are between 180 and 28O ⁰ C. It is usually necessary to employ temperatures below 22O ⁰ C or above 250 ⁰ C, in order to promote the evaporation of the Aralkylalkohols. Temperatures above about 25O ⁰ C to 280 ⁰ C can be used in conjunction with a high feed rate. If desired, the dehydration according to the invention can also be carried out using other methods.

The following examples illustrate the invention. Parts and percentages are by weight when nothing else is stated.

Examples 1-10

According to these examples, the epoxidation of propylene is carried out by adding the amount of hydroperoxide given in the table below in g (z. B. CHP, cumene hydroperoxide), 5 g of tert-butyl alcohol or the specified solvent, the specified amount of molybdenum naphthenate or a pressure reactor another molybdenum salt in g with the specified Mo content in% and the specified amount of propylene in g. The reaction mixture is heated to the specified temperature in ⁰ C and reacted for the specified time without agitation at ordinary pressure. The results are also shown in the following table, in which the hydroperoxide conversion and selectivity, calculated from the propylene oxide formed, are given in moles per mole of converted hydroperoxide.

at peroxide solvent catalyst 5% mon-naphth. C ₃ H ₆ Temp. Reak peroxide Selek game . 5% mon-naphth. ions activity 5% hexanoate **) Time Conversion (%) 5% mon-naphth. lung 99.9 (G) (G) (G) 5% Mo-citrate (G) (X) (Hours) (%) 99.1 1 5 CHP 5 t-B A. *) 0.16 5% Mo oxalate 16.5 90 1.0 91.6 87.0 2 5 CHP 5 t-B A. *) 0.16 Mo (X) 15.9 90 1.0 93.8 84.0 3 5 CHP 5 t-B A. *) 0.16 5% mon-naphth. 16.7V 90 1.0 96.5 86.5 4th 5 CHP 5 t-B A. *) 0.16 13.6 ... 110 0.25 93.0 75.6 5 5 CHP 5 t-B A. *) 0.16 14.8 90 '. 1.0 87.6 75.3 6th 5 CHP 5 t-B A. *) 0.16 15.8 90 1.0 76.4 96.4 7th 5 CHP 5 t-B A. *) 0.03 17.2 90 1.0 90.3 8th 3 CHP 7 (XX) 0.04 14.7 90 1.0 92.7

continuation

at peroxide solvent Catalyst"; (G) C ₃ H ₆ Temp. Reak peroxide Selek game ι ions activity '; Time Conversion (%) r lung (G) (G) (G) (C) (Hours) (%)

3 CHP

10 5 (XXXX)

4.5 (XXX)
2.9 (XX)

0.08
2.0

5% mon-naphth. .2% mon-naphth.

16.2
13.9

90
90

1.0
1.0

97.0
83.0

81.9
85.0

*) tert-butyl alcohol.
(X) acetylacetonate.
(XX) cumyl alcohol.
(XXX) cumene.

(XXXX) Alpha-phenylethyl hydroperoxide.
**) Mon.

Example 11

The epoxidation of propylene is carried out essentially as described in Example 10, with the Except that the amount of catalyst is 0.9 g and the reaction time is 0.5 hours. The hydroperoxide conversion is 77% and the selectivity is 94%, based on propylene oxide formed in moles per mol converted hydroperoxide.

Example 12

5 g of 88% iges -phenylethyl hydroperoxide, 5 g of a-phenylethanol, 0.6 g of molybdenum naphthenate (Mo content 2%) and 16.0 g of propylene are reacted in a pressure ^{vessel for 15 minutes at 100 ° C. without stirring.} The analysis shows a peroxide conversion of 91% and the formation of propylene oxide in a selectivity of 84%, based on the peroxide consumed. The propylene oxide yield based on propylene is 99.6%.

Example 13

The epoxidation is carried out essentially as described in Example 6, but with 0.016 g of permolybdic acid can be used as a catalyst. The conversion is 92% and the on Peroxide related selectivity 52%.

The use of molybdenum disulfide as a catalyst in the procedure described above also leads to good results.

Example 14

The procedure described in Example 1 is repeated, but using 10 g of a solution of the Hydroperoxide of p-ethyltoluene in ethyltoluene, 16.8 g Propylene and 0.03 g of molybdenum naphthenate can be used with a molybdenum content of 5% and one Temperature of 90 ° C and a reaction time of 30 minutes is used. The Hydroxy Peroxide Conversion is 75.5% and the selectivity is 92%, expressed in moles of propylene oxide formed per mole converted hydroperoxide.

Example 15

The procedure described in Example 8 is repeated, but using 16.4 g of propylene, 0.08 g of naphthenate, a temperature of 8O ⁰ C and a reaction time of 1 hour are applied. The hydroperoxide conversion is 92.5% and the selectivity is 83%.

Example 16

Following the procedure described in Example 10 operation will be with 11 g 63% strength Äthylbenzolhydroperoxids in ethylbenzene, 29.6 g of methyl oleate, 0.1 g of molybdenum naphthenate having a molybdenum content of 5% at a temperature of 80 ⁰ C and a reaction time of 3 hours, a hydroperoxide conversion of 83 , 8% and a selectivity of over 89%, expressed as moles of methyl oleate epoxide formed per mole of converted hydroperoxide achieved.

B e i s ρ i e 1 17

Following the procedure described in Example 16, 5.6 g of the hydroperoxide solution and 10.8 g 4-vinylcyclohexone, a temperature of 20 - 50 ° C and a reaction time of 1 hour a hydroperoxide conversion of 87.7% and about 100% Selectivity, expressed as moles of 4-vinylcyclohexane epoxide formed achieved per mole of converted hydroperoxide.

Octene-1, dodecene-1 and hexadecene-1 are used in the converted into their epoxides in the same way.

Example 18

Following the procedure described in Example 17 operation is obtained with 5 g of cumene hydroperoxide, 5 g of cumyl alcohol, 0.2 g of a catalyst solution containing 3.4% vanadium as naphthenate, and 15.4 g of propylene at a temperature of 9O ⁰ C and a Reaction time of 3 hours, a hydroperoxide conversion of 68.2% and a selectivity of 38%.

In the procedure described above, tungsten carbonyl can also be used as a catalyst will.

After separating the epoxides obtained according to the above examples from the respective epoxidation reaction mixtures the respective arylalkanol obtained as a coproduct is then already in the described manner dehydrated to the respective styrene.

For example, alpha-phenylethanol (that from the hydroperoxide is formed in a molar ratio of about 1: 1) in 80% or higher yield by dehydration in the gas phase at 200 to

030 138/2

9 10

250 ° C above grained titanium dioxide or a similar! Ation, styrene is obtained as a highly pure, commercially available one

Chen oxide catalyst at atmospheric pressure in styrene product.

convict. Other catalysts suitable for this purpose can also be used in a corresponding manner for the others

are for example silicon dioxide or aluminum oxide. obtained aryl alcohols dehydrated to the respective styrene

Can be dratized by customary distillation, preferably vacuum distillation.

Claims (1)

Claim: Process for the preparation of styrenes by dehydrating the corresponding aryl alcohols, characterized in that the aryl alcohol is one obtained by reacting an aralkyl hydroperoxide with an epoxidizable olefinically unsaturated compound having 3 to 30 carbon atoms at -20 to 200 ° C _1, optionally in the presence of a solvent, in the presence of compounds of vanadium, molybdenum or tungsten used as a catalyst and separation of the epoxide formed aryl alcohol.