CS207676B2 - Method of o-alcylation of the phenols - Google Patents

Abstract

1. A process for the ortho-alkylation of phenols by reaction of a phenol with an alkanol in the gaseous phase and in the presence of a catalyst which is obtained by impregnation of an aluminium oxid with a solution of an alkaline earth metal salt and subsequent calcination characterized in that the catalyst contains 0,01 to 0,1 millimole of alkaline earth metal per gram of aluminium oxid and that the reaction is conducted at temperatures in the range of 250 - 400 degrees C and at a liquid hourly space velocity in the range of 0,5 - 2h**-1 .

Description

(54) A method for o-alkylating phenols

The present invention provides a process for the o-alkylation of phenols.

Phenol compounds alkylated in o-pole-ozone are important intermediates and are used, for example, for the production of insecticides, herbicides, antioxidants, polymeric polyphenylethers and pharmaceutical products.

Various methods of o-alkylation of phenols with alcohols are already known. Magnesium oxide and alumina are the most commonly described catalysts for this purpose, but also mixed catalysts (K.-D. Bode, in Houben-Weyy, Methoden der organischen Chemie, Vol. VI / 1c, p. 1 008 and later). 1, G. Tiieme neak, Stuttgart 1976).

Thus, GB-A-1,065,337 describes the alkylation of phenol with alkanoe, wherein the reactants are passed in the gas phase over optionally activated alumina as a catalyst. By way of example, the reaction in o-creaol is obtained in an average yield of 27.3% by weight, yielding 12.4% by weight of 2,6-diethylphenol and 5.0% by weight of other phenols. (The ratio of by-products to o-cresol is thus 0; 64.)

According to DE patent specification 1,668,880 phenol and methanol mixture (10% methanol hmoonnotních) in ^d e at ² 5 ^{0 F} and ³⁵⁰ ° ^C and space ^for apalin ^{0.5 y} (H ^'') through ^{g * l} шnoakyy ICN ^{Cart to} an aluminum catalyzed by the multi ^Tor on spec ^^ Kem surface ^{(--τ) 240 U2 /} g, wherein Z ^ ^ka product mixture of 22% o-cresol, 5% ^ o-dimethylphenol and traces aiisolu.

In GB-A-1,228,174 it is recommended that the alumina used for the methylation of phenol be completely free of particularly basic impurities, while small amounts of acid impurities can be tolerated: The presence of basic impurities in alumina reduces the activity of the catalyst and makes it more selective . However, the overall loss in yields outweighs the advantage of improved selectivity.

GB-A-1,034,500 describes an alkylation reaction using magnesium oxide as a catalyst. However, due to the relatively low reactivity of the magnesium oxide catalyst, high reaction temperatures of 475 to 600 ° C are required, at which a strong decomposition of the starting materials such as phenol and methanol is already occurring. A further disadvantage is the rapid permitting of the activity and the short life of the catalyst.

The use of mixed catalysts of vanadium oxide / iron oxide, etc., or cerium oxide / manganese oxide for the phenol alkylation is suggested in DE 2 161 252 and in DAS 2 127 083. However, these types of catalysts exhibit relatively low reactivity, so that in particular for production A high excess of methanol must be used in the monoalkylated product, which greatly reduces the yield of the monoalkylation product.

Thus, these methods show various disadvantages because they are either not sufficiently selective, leading to the formation of undesirable by-products and / or not sufficiently reactive, resulting in higher reaction temperatures, excess methylating agent or low spatial velocity. liquid.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for the o-alkylation of phenols in the gas phase, which more preferably combines activity and selectivity. It has now been found that catalysts obtained by impregnating a conventional alumina catalyst with an alkaline earth salt solution and subsequent calcination are well suited for the o-alkylation of phenols in the gas phase (i.e., with improved yield and / or low byproduct content). This finding was surprising since it has been hitherto assumed that doping of the alumina catalyst with bases, such as is also carried out with the alkaline earth salts of the invention, still results in a reduction in catalyst activity and thus yields in the o-alkylation of phenols.

The present invention provides a process for the o-alkylation of phenols of formula (I):

(I) where

R and R ', which are the same or different, each represent a hydrogen atom, an alkyl group of 1 to 6 carbon atoms or also a phenyl or benzyl group by reacting a phenol with an alkanol at elevated temperature in the gas phase in the presence of a metal oxide catalyst characterized in that the alkylation is carried out in the presence of a catalyst obtained by impregnating an aluminum oxide catalyst with a solution of alkaline earth salts and then calcining at a temperature of 450 to 600 ° C, the catalyst containing from 0.1 to 0.01 per gram of alumina millimol of alkaline earth and has a residual acidity of about 0.05 to 0.2 milliequivalents per gram.

The alumina used for the production of the catalyst, preferably the gamma modification, can be produced, for example, by calcination of Al 2 O 3. 3H ₂ O, which is accessible by precipitation of ammonium salts, hydrolysis of aluminum alkoxide and the like. However, it is also possible to use commercially available activated alumina catalysts of high purity (sodium content preferably below 0.1%) and of a large specific internal surface area (specific internal surface area (BET) between 200-300 m @ 2 / g). It is known that pure alumina is substantially acidic. Acidic strength and distribution can be determined by known methods (cf. H. Pines, WO Haag,

J. Amer. Chem. Soc. 82, 2,471 (1960) and A. E. Hirschler, J. of Catal. 2, 428 (1963). By the action of alkaline earth salts and subsequent calcination, the initial acidity of about 0.2 to 0.3 milliequivalents per g of the alumina catalyst used was reduced, while at the same time the ratio of strong to weak acidity was reduced. However, the acidity loss did not occur proportionally to the alkaline earth concentration of the alumina catalyst.

The alkaline earth salts and preferably the barium salts used are, for example, nitrates, carbonates, bicarbonates, oxalates, acetates, hydroxides or oxides.

The acidity obtained after impregnation and calcination of the modified catalyst is about 0.05 to 0.2 milliequivalents per gran. The residual acidity of the catalyst is required for the process of the invention. A considerably higher alkaline earth doping, υ than above, is therefore undesirable and leads to a reduction in catalyst activity.

The alumina catalysts impregnated with a suitable, preferably aqueous, alkaline earth salt solution are carefully dried and then calcined at 450 to 600 ° C. Physical properties such as specific inner surface, specific pore volume, strength and abrasion do not change. The lifetime of the alumina catalysts does not deteriorate between 350 and 1000 hours, depending on the reaction conditions.

The process according to the invention is preferably carried out at temperatures of 250 to 400 ° C, in particular 290 to 360 ° C, and preferably at a liquid liquid velocity (LHSV) of about 0.5 to 2. This can be carried out both at normal and at elevated temperatures. pressure; it is possible to carry out the reaction in the presence of water vapor or an inert gas, but this is not absolutely necessary. The catalyst may be arranged, for example, as a fixed bed or as a fluidized bed. The process according to the invention is particularly suitable for the production of monoalkylated phenols, wherein the molar ratio of the alkylating agent to the phenolic compound is about 0.4 to 2, preferably 0.4 to 0.8.

Phenols of the general formula I are preferably used as starting products,

(I) where

R and R * are as defined above,

R 'is preferably a hydrogen atom.

The alkyl groups may be branched or preferably straight chain. They preferably have 1 to 6 and in particular 1 to 3 carbon atoms. Examples are methyl, ethyl or propyl.

The phenols of the formula I are known or can be prepared by methods known per se.

The alkanols used as alkylating agent may have a branched chain or preferably a straight chain. They preferably contain 1 to 6, in particular 1 to 3, carbon atoms and are, for example, methanol, ethanol or propanol.

The following definitions apply to the following terms:

207676 4 * · used material per h

Liquid space velocity (LHSST), (h ¹ ) = ----- · bulk catalyst volume

Sated, vztažaio ____________ _ ^{nt nrzrra alkylated} fnol g ^(%) HR ^and VR frnol ZCR faol / Ю - nrzrrtgovaný frnol ^{(MO O} / H)

Formation of by-products * "sum of all liquid by-products (kg / h) except water and frnol desired product (kg / h)

Percentages are intended.hmoonoot ·

Three different aluminum oxide catalysts A, B, C were used; The composition and physical data are given in Tables I and II. As a comparison, Tables I and II also show the corresponding data of non-corrosive alumina catalysts.

Example 1

By slowly adding aqueous ammonia to an aqueous solution of aluminum nitrate heated to 90 ° C, the aluminum hydroxide precipitates. · The precipitate is filtered, carefully · sr washed and 30 hours sr - dried at 120 ° C · Then calcined for 4 hours under vacuum at 650 ° C · 1000 g of activated alumina thus produced and treated with X sr impregnated with an aqueous solution of 2,61 g (0,01 mol) of barium nitrate · Measure the volume of the aqueous solutions sr to be completely absorbed by the catalyst · After 15 minutes · The catalyst is dried at 110 ° C and calcined in a nitrogen atmosphere at 450 to 500 ° C for 10 hours.

In the same way, from commercial activated alumina catalysts X and Z, catalysts B and C are prepared by employing an aqueous solution of 7.66 g (0.03 mol) of barium acetate in the case of B, and C · sr uses an aqueous solution of 5.18 g (0.05 mol) of stearate acetate. The catalyst composition and the physical properties are given in Tables I and II.

Table I

Composition and physical properties of catalyst

Composition and physical properties X AND K ataly Y z o t o r (B) OF C Al ₂ 0 ₃ . % 98.5 98.3 96 95.5 98 97.5 SiO ₂ 0.05 0.05 1.0 1.0 0.05 0.05 Na ₂ O 0.02 0.02 0.1 OJ 0.1 0.1 Ba ² + 0.13 0.35 Sr ²⁺ 0.45 Weight loss · at, Annealing (1 h 900 ° C) 1.5 · '5 2 2 1.5 1.7

crystal structure of crystalline phase r ~ Al ₂ O ₃ small subd 1 n -A1 ₂ O ₃

X-A1 ₂ O ₃ y-Al ^ small sub η -AlgOj continuation of Table I

Composition and physical properties X AND Catalyst Y В OF C spherical form mm cylindrical 2 x moldings 10 extrudate 1 1.5 x 4.5 extrudate 1,3x6 specific internal surface (BET) m / g 240 240 250 245 280 270 bulk density g / cnr ’ 0.8 0.8 0.62 0.62 pore volume ml / g 0.55 0.55 0.64 0.6 0.4. 0.4

T a b u 1 к ·? II

Catalyst acidity determined by titration with n-butylamine after previous annealing at 500 ° C

Indicator PKa % H 2 SO ₄ equivalents Milliequivalents acid / g catalyst X AND Y в of C phenylazonaphthylamine +4 5 x Ю ⁵ 0.2 0.15 0.25 0.2 0.2 0.1 p-dimethylaminoazobenzene ⁺ 3,3 3 x 10 ⁴ 0.15 0.05 0.25 0.2 0.2 0.1 4-Phenylazodiphenylamine + 1, 5 2 x 10 ^-2 0.05 0.0 0.2 0.0 OJ 0.0 benzalacetofenone -5.6 0.7 x 10 ² 0.0 0.0 0.1 0.0 0.0 0.0

Example 2

A mixture of methanol and phenol in a molar ratio of 0.5 is passed through a metering pump at normal pressure and a liquid space velocity of 1 h ^-1 through a preheater through a steel flow reactor. The catalyst bed is in the form of a cylindrical annulus formed by a 30 mm reactor jacket and a 10 mm central thermocouple protective tube. An aluminum oxide catalyst impregnated with 0.01 mol of barium nitrate composition A is charged, the catalyst charge is 200 ml. The reactor is heated by electrical resistors and maintained at a temperature of 300 ° C while adjusting the temperature to a maximum of 320 ° C on the catalyst.

The average composition of the reaction product is shown in Table III.

For comparison, reaction products obtained under the same reaction conditions with an impregnated alumina catalyst X are also shown in Table III.

Tib lulka III

Catalyst. Comparative · said-a-d AND AND 'X charge = mettrnoo / phenol in mol. ratio 0.5 / 1 temperature maximum temperature band (° C) 320 320 320 space velocity of liquid (h “1) '1 1 1 time (h) '10 350 10 yield of liquid product W 99, ₄ 99.2 99.3 Product composition and%) dimethyl ether and hydrocarbons 0.2 0.1 . 0.3 anisol 0.3 0.4 1, 2 phenol 58.7 59.1 57.6 o-cresol 25.5 25.0 23.7 m / p-cresol 0.4 0.4 0.8 dimethylphenol 5.8 6.0 ⁶ » ¹ other dimethylphenols 0.8 0.8 0.9 trimethylphenols 0.7 0.8 1.3 higher phenol homologs 0.4 0.4 1, 1 water 7.1 7.0 6.9 total 99.9 1 00 99.9. selectivity of o-cresol formation («) 61, 5 80.6 72.6 yield of by-products for t-o-cresol 0.337 0.356 С ₅ 4 94 Example 3 In the same way as described in  Example 2, not the mixture i mernno-fnol in a mole ratio of 0.4 on the catalyst based on gtInatkklSi aluminum aluminum A, impregnated 0.01 mol of magnesium nitrate . Reactor it warms up about 320 ° C on the catalyst adjusts the maximum temperature to 330 ° C. Spatial speed liquid is 1.5 h

For comparison, the reaction is also carried out on an impregnated aluminum oxide catalyst X under the same reaction conditions.

The reaction products have the following average composition as well as Table IV).

Tíbu.lka IV

Catalyst S r And. . ’ ovnávací AND example And. X charge = 'methanoo / phenol in mol. ratio of 0.4 / 1. thermal maximum band, temperature (° C) 330 330 330 330 space speed liquid. (h-i) . '' '' 5 1.5 1.5 1.5 time (h) IT· 100 ALIGN! 300 10 yield of the liquid product (%) 99.5 99.5 99.4 99.5 Composition 'Droduktu (%) dimeryl ether and hydrocarbons tracks tracks 0.1 0.1 anisol 0.4 0 ' 0.5 1.0 phenol 63.3 61.6 63.5 62.7 o-cresol 23.1 24.4 22.7 22.0 m / ppd 0.4 0.7 0.4 0.5 dimeeylphenol 4.7 5.3 4.8 5.0 other dimethylphenols 0.7 1.5 0.8 1,2, trimethylphenols 0.7 - 0.6 0.8 higher phenol homologs 0.2 - 0.2 0.3 water 6.5 6.5 6.4 6.3 total 100 ALIGN! 100.1 100 ALIGN! 99.9 selectivity of o-cresol formation (%) 80.0 79.2 78.9 74.4 yield of by-products for t o-cresol 0,307 0.312 0,326 0.405

Example 4

A mixture of methanol and 3,5-dimethylphenol at a molar ratio of 0.5: 1 at a liquid space velocity of 1 h ^-1 reacted sterým Úsobí from ^p as ^p o ^p SAN příHaclu 2 to C katatyzáWru impregnated with 0.05 mol of strontium acetate.

The average composition of the reaction products as well as the results of the reaction carried out under the same conditions on the unimpregnated aluminum oxide catalyst Z are shown in Table V below.

Table V

Catalyst Comparative C example OF charge = methanol / 3,5-dimethylphenol in mol. ratio 0.5 / 1 thermal maximum band, temperature (° C) 330 330 space velocity of liquid (h '’) 1.3 1.3 time (h) 8 8 yield of liquid product (%) 99.2 99.3 Composition Of Droduct (%) low phenol homologues, ethers and hydrocarbons 2.6 2.8 3,5-dimethylphenol- 56.8 55.9 2,3,5-trimethylphenol 27.1 25.9 2,3,5,6-tetramethylphenol 5.8 6.4 other alkylphenols 0.4 water 7.3 7.4 total 100 ALIGN! 99.9 selectivity of trimethylphenol formation (%) 75.2 70.3 yield of by-products for t 2,3,5-trimethylphenol C, 32 0.413

Example 5

In a manner similar to that described in Example 2, a mixture of ethanol and phenol in a molar ratio of 0.4 with a water content of about 3% was reacted on an aluminum oxide catalyst impregnated with barium nitrate composition B.

The liquid velocity is 1 h ¹ , the maximum temperature on the catalyst is adjusted to 325 ° C.

The reaction product has an average composition as shown in Table VI. For comparison, results obtained under the same conditions on unimpregnated alumina catalyst uvádě are also reported.

Table VI

Caaalyzátor Comparative (B) example Y charge = ethanol / phenol / water in mol. ratio of 0.4 / 1 / 0.17 thermal maximum band, temperature (° C) 325 325 space velocity of liquid (h- ’) 1 1 time (h) 8 8 yield of liquid product (%) 99.9 ,8 99.8 Composition Of Droduct (96) diethyl ether and hydrocarbons tracks tracks phenetol tracks 0.1 phenol 58.7 60.3 o ^ ty ^ eno! ’ 24.5 22.3 mp-ethylphenol 2.3 2,0 diethylphenols 3.4 3.5 higher phenol homologs 2.3 2.4 water 8.8 9.4 total 100 ALIGN! 100 ALIGN! selectivity of origin («) 85.1 82.8 byproduct for ttylphenyl 0.338 0.359

Claims (1)

SUBJECT OF THE INVENTION A process for the o-alkylation of phenols of general formula (I): (I) wherein R and R, which are the same or different, each represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or also a phenyl or benzyl group by reacting a phenol with an alkanol at elevated temperature in the gas phase in the presence of a metal oxide catalyst characterized in that the alkylation is carried out in the presence of a catalyst obtained by impregnating the alumina catalyst with an alkaline earth salt solution and then calcining at a temperature of 450 to 600 ° C, the catalyst containing from 0.1 to 0.01 millimoles of alkali per gram of alumina % of soil and has a residual acidity of 0.05 to 0.2 mH2.