Process for Producing Acetyl-Substituted Aromatic

turopaisches Patentamt European Patent Office © Publication number: 0 21 5 351 Office europeen des brevets A2

<2> EUROPEAN PATENT APPLICATION

© Designated Contracting States: @ Inventor: Fujiyama, Susumu DE FR GB IT NL 522-65, Kamitomii Kurashiki-shi(JP) Inventor: Matsumoto, Shunichi 1168-3, Tanoue Kurashiki-shi(JP) Inventor: Yanagawa, Tatsuhiko 1987, Nakashima Kurashiki-shi(JP)

Process for producing acetyi-substituted aromatic compound.

v=y This invention provides a process for producing an acetyi-substituted aromatic compound by making an aromatic compound react with acetyl fluoride in the presence of substantially anhydrous hydrogen fluoride as a catalyst. M It has been already known to acylate- an ar- ômatic compound with an acid fluoride in the presence of boron fluoride or hydrogen fluoride and O boron fluoride as a catalyst. It has been found that, *în a reaction of an aromatic compound with acetyl fjfluoride, even when hydrogen fluoride alone is used ■as a catalyst, the intended acetyi-substituted ar- ômatic compound can be obtained in excellent yield 5 and further the complex compound formed can be ^decomposed without difficulty and the hydrogen flu- yoride catalyst can be easily recovered.

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PROCESS FOR PRODUCING ACETYL-SU BSTITUTED AROMATIC COMPOUND

The aromatic compounds used as the starting BACKGROUND OF THE INVENTION material in this invention include alkylbenzenes such as toluene, xylene, trimethylbenzene, ethyl- This invention relates to a process for produc- benzene, cumene, and butylbenzene; naphthalene ing an acetyi-substituted aromatic compound which 5 and alkylanphthalenes such as methylnaphthalene; comprises acetylating an aromatic compound such phenols and naphthols; and further aromatic ethers as an aromatic hydrocarbon and a phenol with such as anisole and phenyl ether. Particularly pre- acetyl fluoride. ferred are compounds in which the para position to It is disclosed in Japanese Patent Application the substituent in the aromatic ring is vacant and Kokai (Laid-open) No. 135756/79 to produce a 2- io naphthalenes having a substituent in the 2-position. alkyl-6-acylnaphthalene by acylating a 2-alkylnaph- Acetyl fluoride as the other starting material, thalene with an acid fluoride in the presence of can be obtained by mixing acetic anhydride or boron fluoride or hydrogen fluoride and boron flu- acetyl chloride with hydrogen fluoride to produce oride as a catalyst. acetyl fluoride according to the following equation - It is described in the above-mentioned inven- 75 (I) or (2) and separating the free acid simulta- tion that the presence of boron fluoride as a cata- neously formed. lyst component is essential .and the absence of boron fluoride results in low yield of the acylation (CH3CO),0 + HF - CH3COF + CH3COOH - product. However, according to the experiment of (I) the present inventors, it has been found that when 20 boron fluoride is used as a catalyst component in CH3COCI + HF - CH3COF + HCI (2) the reaction of aromatic compound with acetyl flu- It is essential here that the reaction (2) men- oride, it is difficult to decompose the resulting tioned above should be carried out at a slight complex compound on account of the instability of excess of acetic anhydride. Thus, when hydrogen aromatic keton of the reaction product. 25 fluoride is in excess of the equivalent, the maxi- mum azeotropic mixture combined hydrogen fluoride with the r acid, which leads to the loss of SUMMARY OF THE INVENTION hydrogen fluoride, is formed to become insepa- rable and further the acid formed is contaminated Accordingly, the present inventors have made 30 with fluorine, so that special treatments are re- extensive studies to attain a process for producing quired to remove it. When acetic anhydride is in an acetyi-substituted aromatic compound with high- excess, such difficulties do not occur and hydrogen er efficiency including the steps of the decomposi- fluoride can be quantitatively recovered as acetyl tion of the complex compound and the recovery of fluoride. However, there is no need of large excess the catalyst component. Consequently, it has been 35 and the ratio of excess acetic anhydride to hy- found that, in the reaction of an aromatic com- drogen fluoride may be 5 mol% or below. pound with acetyl fluoride, even when hydrogen The apparatus used for generating acetyl flu- fluoride alone is used as a catalyst the intended oride may be a conventional distillation column acetyi-substituted aromatic compound can be ob- having a number of plates necessary for fractionat- tained in excellent yield and further the complex 40 ing acetyl fluoride and the free acid. Acetic anhy- compound formed can be readily decomposed and dride and hydrogen fluoride are fed to the appro- the hydrogen fluoride catalyst can be easily recov- priate plate of the distillation column as a mixture ered. This invention has been accomplished on the or separately, the column bottom is heated up to basis of above findings. the boiling point of the acid and the column top is 45 given an appropriate reflux. Such a conventional distillation operation makes it possible to recover DETAILED DESCRIPTION OF THE INVENTION pure acetyl fluoride from the column top and an acid containing no fluorine from the column bottom. Thus, this invention provides a process for Since the reaction proceeds at a high rate, producing an acetyi-substituted aromatic com- 50 virtually no residence time is necessary. The reac- pound which comprises making an aromatic com- tion can be conducted under an ordinary or an pound including an 2-alkylnaphthalene react with applied pressure, for example I kg/cm2G, and either acetyl fluoride in the presence of substantially anhydrous hydrogen fluoride as a catalyst.

2 o 0 215 351 4 now operauon or Datcnwise operation may De used. The reaction proceeds in a homogeneous liq- The difference of boiling point between acetyl flu- uid phase or, according to circumstances, in two- oride and the acid formed is so large that the two liquid phases consisting of a starting aromatic com- can be easily separated. pound phase and a catalyst phase, so that there is The acetyl fluoride thus formed is used for 5 no need of vigorous stirring. Since the reaction is acetylation as the acetylating agent. The molar slightly exothermic, a reactor provided with heat ratio of acetyl fluoride to the starting aromatic com- removal equipment is used as required. pound is I or below, 0.9 to 0.5 being particularly The acetylation reaction liquid thus obtained is preferable. The presence of excess acetyl fluoride a solution of an aromatic ketone, the acetylation decreases the overall reaction rate (i.e. the space w product, in hydrogen fluoride. On heating the -reac- time yield of the acetylation product). tion liquid, the affinity between the reaction product As the catalyst, a substantially anhydrous hy- and hydrogen fluoride is broken and hydrogen flu- drogen fluoride is used. Its water content is prefer- oride can be easily vaporized and separated. ably 5% or below because the presence of water in It is necessary to conduct the above-mentioned hydrogen fluoride causes the rapid decrease of rs catalyst recovery operation as rapidly as possible catalytic activity. In order to obtain a sufficient in order to avoid the thermal degradation of the reaction rate, the molar ratio of hydrogen fluoride to reaction product. For this purpose, the catalyst be used relative to the acetylating agent is 5 or recovery operation is preferably conducted in a above, preferably in the range of 10 to 20. Hy- flow operation using a multistage gas-liquid contact drogen fluoride used in a molar ratio of 20 or above 20 apparatus (i.e. a distillation column). For catalyst gives little additional effect and hence is not ad- recovery, heating at a temperature of 40°C or from vantageous the economical viewpoint of the higher, particularly 40 to 100 °C, is necessary. The process. decomposition column is preferably fed with an The reaction temperature of acetylation is 0 to amount of heat which is in excess of that neces- 70°C, preferably 10 to 50°C. Since the reaction rate ?5 sary for vaporizing hydrogen fiuoride fed to the increases as the temperature is increased but also column. It is advantageous in the process to con- the side reaction increases, an optimum tempera- duct the catalyst recovery operation under atmo- ture is selected from the above-mentioned range spheric pressure or a slightly increased pressure of depending upon the starting material used. When 2 kg/cm2G or below. In order to make the thermal the starting compound has a high melting point and ?o decomposition of the complex compound between further is insoluble in hydrogen fluoride as in the the acetyi-substituted aromatic compound and hy- :ase of aromatic hydrocarbons, it is effective to drogen fluoride proceed smoothly, the decomposi- jse a suitable solvent in order to make the reaction tion is preferably conducted by heating the com- Droceed smoothly. Preferable solvents are those plex compound under reflux using as a diluent a which can dissolve the starting compound well, are is substance which has a boiling point such that it is :hemically inert under reaction conditions, and easily separable from hydrogen fluoride, has a lave a good compatibility also with the reaction good compatibility with the reaction product, name- iquid formed. They include, for example, benzene ly the acetyi-substituted aromatic compound, and )r halogenated hydrocarbons such as chloroben- with hydrogen fluoride, and is inert to hydrogen tene, dichloromethane, dichloroethane and freon.

me acetyl tluonde tormed is distilled out through so as to keep the temperature of the column top at an outlet pipe 4 and acetic acid is withdrawn about 35 °C, acetyl fluoride was distilled out of the through a pipe 5. The acetyl fluoride is fed to an column top at a rate of 2I moles per hour, and a acetylation reactor 6 equipped with a stirrer 19 and liquid mixture comprising 21 moles of acetic acid is contacted there with stirring with the starting 5 and I mole of acetic anhydride was withdrawn aromatic compound fed through a pipe 7 and with every hour from the bottom. The yield of acetyl hydrogen fluoride fed through a pipe 8. The reac- fluoride relative to supplied hydrogen fluoride was tion begins in two liquid phases of the hydrogen quantitative. fluoride phase and the starting material oil phase, which then change into a homogeneous liquid 70 phase as the reaction proceeds. The reaction liquid Acetylation of 2-methylnaphthalene is drawn out through a pipe 9, led to a hydrogen fluoride recovery column 10, and contacted there Two stainless steel vessels each equipped with with a diluent such as benzene which is being a stirrer, the first reactor having an inner liquid refluxed and recycled. Hydrogen fluoride is sepa- 75 volume of 6 I and the second reactor having an rated by vaporization and drawn out through a pipe inner liquid volume of 4 t, were connected in II. The column top vapor is condensed by cooling series to be used as the acetylation reactor. A and separated into layers. The benzene phase is solution comprising I.5 kg of 2-methylnaphthalene refluxed from a pipe 12 to the recovery column 10; and 0.3 kg of benzene was fed every hour to the hydrogen fluoride is recycled to the acetyl fluoride 20 first reactor. Simultaneously, 0.5 kg per hour of generating apparatus and the acetylation reactor - acetyl fluoride synthesized above and 2.5 kg per (not shown in the Figure). From the bottom of the hour of hydrogen fluoride were also fed to the first hydrogen fluoride recovery column is withdrawn reactor. through a pipe 13 the acetylation product, a crude The reaction temperature was adjusted to 25 °C product, which is then freed from trace amount of 25 by passing cooling water through the jacket of the residual acid in a neutralization and washing equip- reactor. The pressure in the reaction was I ment 14 and distilled in a distillation apparatus 15, kg/cm2G. The reaction mixture was continuously whereby the byproduct is removed through a pipe withdrawn from the second reactor to be fed to the 16, the unreacted raw material is removed through a subsequent hydrogen fluoride recovery column. pipe 17 to be recycled to the reaction step, and the 30 final product is obtained through a pipe 18. A suitable solvent is used to make the reaction Recovery of hydrogen fluoride proceed smoothly as required. This is added to the starting material in a pipe 7. Fig. I shows a case The packed column used in acetyl fluoride where the solvent and the diluent for decomposi- 35 synthesis was employed as the hydrogen fluoride tion are the same. But, in the case where both are recovery column. The hydrogen fluoride recovery different, further a process for recovering the sol- column was charged with benzene, and heat was vent is added to it. supplied at a rate of 300 Kcal per hour to the This invention will be further explained in detail reboiler under a pressure of I kg/cm*G to keep the below with reference to Examples, but it is not to benzene refluxing. limited thereto. Then the above-mentioned reaction mixture was continuously fed to the upper part of the column at a rate of I kg per hour, and the hydrogen =xampie i fluoride recovery column was continuously oper- as ated while being replenished with benzene. Synthesis of acetyl fluoride From the column top were distilled out hydrogen fluoride and unreacted acetyl fluoride, while A stainless steel packed column having a di- from the column bottom were recovered every hour imeter of 50 mm and a height of I000 mm pro- 243 g of acetylated methylnaphthalene, I09 g of fided with a top reflux apparatus and a bottom ;o unreacted methylnaphthalene, and 20 g of a high eboiler was used as the acetyl fluoride synthe- boiling point product as the crude acetylation prod- sizer. Acetic anhydride (22.0 moles per hour) and uct. The acetylation product contained 75% of 2- lydrogen fluoride (2I.0 moles per hour) were mixed acetyl-6-methylnaphthalene. ind fed continuously to the middle plate of the jacked column, and heat was supplied to the re- 55 joiler with an electric heater at a rate of 260 Kcal jer hour. The synthesizer was operated under a )ressure of I.O kg/cm2G. While reflux was applied 0 215 351 8 example d. Example 3

Acetylation of toluene Acetylation of m-xylene

Toluene was acetylated by using the same 5 A stainless steel autoclave of 500 ml volume apparatus and the same operation as In Example I. equipped with a jacket and a stirrer was used as To the first reactor were fed every hour 0.9 kg the acetylation reactor. of toluene, 0.4 kg of acetyl fluoride, and 2.0 kg of A solution of 56 g (0.9 mole) of acetyl fluoride hydrogen fluoride, and the reaction was conducted in 103.1 g (I mole) of m-xylene was placed in the at a reaction temperature of 40 °C and under a w autoclave, and then, with cooling, 300 g (15 moles) reaction pressure of I.5 kg/cm2G. The reaction mix- of hydrogen fluoride was introduced thereinto. The ture was continuously withdrawn from the second mixture was allowed to react at a reaction tempera- reactor and hydrogen fluoride was recovered in the ture of 40°C under a reaction pressure of 1.5 same manner as in Example I. The crude product kg/cmJG for 1.5 hours. Thereafter, the reaction mix- obtained from the bottom of the hydrogen fluoride 75 ture was withdrawn into ice water. The resulting oil recovery column had the following composition: layer was washed with alkaline water and distilled unreacted toluene 55%, methylacetophenone 41%, to determine the amount of high boiling point by- high boiling point product 4%. The products and analyzed by gas chromatograph to methylacetophenone contained 97.5% of 4- determine the yield of the acetylated product. methylacetophenone. 20 Examples of acetylations conducted in the same manner as mentioned above using various aromatic compounds as the starting material are summarized in Table I.

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4. A process for producing an acetyi-substituted aromatic compound according to claim I uiaims wherein said acetyl fluoride is obtained by the reaction of an excess of acetic anhydride or acetyl 1. A process for producing an acetyi-substituted chloride with hydrogen fluoride. aromatic compound which comprises making an 5. A process for producing an acetyi-substi- aromatic compound react with acetyl fluoride in the tuted aromatic compound according to claim 4 presence of substantially anhydrous hydrogen flu- wherein the ratio of excess acetic anhydride to oride as a catalyst. 50 hydrogen fluoride is 5 mol% or below. 2. A process for producing an acetyi-substi- 6. A process for producing an acetyi-substituted aromatic compound according to claim I tuted aromatic compound according to claim I wherein the said aromatic compound is an alkyl- wherein the reaction pressure in acetylation is an benzene or an alkylnaphthalene. ordinary pressure to 2 kg/cmaG. 3. A for process producing an acetyi-substi- 30 . 7. A process for producing an acetyi-substituted aromatic compound according to claim I tuted aromatic compound according to claim I wherein the said aromatic compound is phenol, wherein benzene is used as the solvent for ar- naphthol, or an aromatic ether. omatic hydrocarbons. 13 0 215 351 14

8. A process for producing an acetyi-substi- fluoride as a catalyst and then thermally decom- tuted aromatic compound according to claim I posing the resulting complex compound between wherein the reaction temperature of acetylation is 0 the acetyi-substituted aromatic compound and hy- to 70 °C. drogen fluoride in the presence of a diluent which 9. A process for producing an acetyi-substi- 5 is inert to hydrogen fluoride. tuted aromatic compound which comprises making 10. A process for producing an acetyi-substi- an aromatic compound react with acetyl fluoride in tuted aromatic compound according to claim 9 the presence of substantially anhydrous hydrogen wherein benzene is used as the said diluent.

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