United States Patent (19) 11 Patent Number: 4,967,004 Maki Et Al
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United States Patent (19) 11 Patent Number: 4,967,004 Maki et al. (45) Date of Patent: Oct. 30, 1990 54 PROCESS FOR PRODUCING Chemical Abstracts, vol. 85, No. 7, Aug. 16, 1979, CA N,N-DETHYLAMINOPHENOLS 46 172r. 75) Inventors: Hiroshi Maki; Shigeru Sasaki, both European Search Report EP 88303116.3. of Chiba, Japan Primary Examiner-Nathan M. Nutter 73 Assignee: Sumitomo Chemical Company, Attorney, Agent, or Firm-Sughrue, Mion, Zinn, Limited, Osaka, Japan Macpeak & Seas (21) Appl. No.: 179,447 (57 ABSTRACT A process for producing an N,N-diethylaminophenol is 22 Filed: Apr. 8, 1988 disclosed, comprising subjecting an aminophenol to 30 Foreign Application Priority Data reductive alkylation with acetaldehyde in the presence Apr. 9, 1987 JP Japan .................................. 62-88068 of a solvent, a catalyst, and hydrogen is disclosed, in Apr. 21, 1987 JP Japan .................................. 62-99047 which the reaction mixture from which the catalyst has been removed is subjected to distillation while maintain 51) Int. Cl. ............................................ CO1C 209/00 ing the temperature of the bottom at 160 C. or lower to 52 U.S. C. .................................... 564/397; 564/398; substantially remove the unreacted acetaldehyde and 564/437 the solvent, the residual bottom is distilled while main 58 Field of Search ................. 564/397, 437, 398, 86, taining the temperature of the bottom at 200 C. or 564/177, 180, 184, 218; 260/508; 558/56; lower to recover a crude N,N-diethylaminophenol as a 560/43; 562/433 distillate, and the recovered crude N,N-diethylamino 56) References Cited phenol is contacted with a solvent to which at least one U.S. PATENT DOCUMENTS of acid sulfites and dithionites has been added, said solvent being substantially incompatible with the N,N- 4,760,183 7/1988 Papenfuhs et al. ................... 558/56 diethylaminophenol, in an inert gas atmosphere, fol FOREIGN PATENT DOCUMENTS lowed by precipitating and recovering the N,N-die thylaminophenol by cooling. N,N-Diethylamino 1352826 2/1987 Fed. Rep. of Germany . 127337 10/1981 Japan. phenols of high purity can be obtained in high yield 1585018 2/1981 United Kingdom. without involving problems, such as production of large quantities of waste water and sludge, corrosion of OTHER PUBLICATIONS materials, and coloring with time. Chemical Abstracts, vol. 107, No. 13, Sep. 28, 1987, CA 15359u. 4 Claims, No Drawings 4,967,004 1. 2 having higher purity and suffering from lesser coloring, PROCESS FOR PRODUCING depending on the end use. N,N-DIETHYLAMINOPHENOLS SUMMARY OF THE INVENTION FIELD OF THE INVENTION 5 Accordingly, one object of this invention is to pro vide a process for producing an N,N-diethylamino This invention relates to a process for producing an phenol of high quality in a high yield without involving N,N-diethylaminophenol. N,N-Diethylaminophenols the above-described problems associated with the con are of high industrial importance as intermediates for ventional techniques, such as production of large quan the production of dyes for heat-sensitive or pressure 10 tities of waste water and sludge, corrosion of materials, sensitive paper, xanthene dyes, fluorescent dyes, etc. and the like. That is, the present invention relates to an improved BACKGROUND OF THE INVENTION process for producing an N,N-diethylaminophenol Conventionally known processes for synthesizing comprising subjecting an aminophenol to reductive N,N-diethylaminophenols include (1) a method com 15 alkylation with acetaldehyde in the presence of a sol prising obtaining sodium metanilate from nitrobenzene vent, a catalyst, and hydrogen, in which the reaction ethylating sodium metanilate with ethyl chloride or mixture from which the catalyst has been removed is diethyl sulfate, and subjecting the ethylated compound subjected to distillation while maintaining the tempera to alkali fusion, (2) a method comprising reacting a ture of the bottom at 160 C. or lower to substantially dihydric phenol with diethylamine in the presence of an 20 remove the unreacted acetaldehyde and the solvent, the acid catalyst, and (3) a method comprising ethylating an residual bottom is distilled while maintaining the tem aminophenol with ethyl chloride or diethyl sulfate in perature of the bottom at 200 C. or lower to recover a the presence of an alkali salt. crude N,N-diethylaminophenol diethylaminophenol as The method (1) is called an alkali fusion process. This a distillate, and the recovered crude N,N-diethylamino method is of little industrial interest because it produces 25 phenol is contacted with a solvent to which at least one large quantities of waste water and sludge and also of acid sulfites and dithionites has been added, said requires a lengthy process. solvent being substantially incompatible with the N,N- The method (2), in which the reaction is carried out diethylaminophenol, in an inert gas atmosphere, fol using an excessive amount of diethylamine in the pres lowed by precipitating and recovering the N,N-die ence of an acid catalyst at a high temperature and a high 30 thylaminophenol by cooling. pressure, provides N,N-diethylaminophenols only in a DETAILED DESCRIPTION OF THE low yield with large amounts of by-products, and the INVENTION excess diethylamine should be recovered. There is a further problem of corrosion of materials. Therefore, The aminophenols which can be used in the present 35 invention include o-aminophenol, m-aminophenol, p this method is very difficult to carry out on an industrial aminophenol, etc., with m-aminophenol being particu scale. larly preferred. The N,N-diethylaminophenols specifi The method (3), though using an alkali salt as an acid cally include N,N-diethyl-o-aminophenol, N,N-diethyl scavenger, still involves a problem of material corro m-aminophenol, N,N-diethyl-p-aminophenol, etc., with sion. Further, it is difficult to separate a by-product 40 N,N-diethyl-m-aminophenol being particularly pre chloride and a produced N,N-diethylaminophenol after ferred. completion of the reaction, and purification of the de The reductive alkylation according to the present sired product produces a large quantity of waste water, invention can be carried out easily in a known manner, thus making the process considerably complicated. that is an aminophenol, a solvent, and a catalyst are In addition, while any of the methods (1), (2), and (3) 45 charged in a reactor, and acetaldehyde is then continu inevitably requires neutralization treatment with an acid ously fed thereinto while applying a hydrogen pressure. or an alkali for recovery of the produced N,N-die The solvent to be generally used includes aliphatic alco thylaminophenol, it is difficult, by nature of amino hols, e.g., methanol, ethanol, propanol, etc., and the group-containing compounds, to judge the end point of catalyst includes those capable of catalyzing reductive neutralization. Moreover, the thermal instability of the 50 alkylation, such as platinum, palladium, nickel, etc. N,N-diethylaminophenols has permitted of no use of The acetaldehyde is usually used in an amount of distillation for purification. This naturally limits the from 2.1 to 4 mols per mol of the aminophenol. The quality of the finally obtained N,N-diethylaminophenol. solvent is used in an amount of from 1 to 20 parts by More specifically, the N,N-diethylaminophenols pro weight per part by weight of the aminophenol. The duced by these conventional methods generally assume 55 amount of the catalyst to be used ranges from 0.005 to brown due to a small tar content (heavy content), which 0.1 part by weight per part by weight of the aminophe has often adversely affected their commercial value. nol. It has also been proposed that an aminophenol is The reaction temperature is from room temperature subjected to reductive alkylation with acetaldehyde and to 150° C. The hydrogen pressure is not particularly the produced N,N-diethylaminophenol is recovered by 60 limited and is usually 20 kg/cm2G or less. distillation. The product obtained by this technique has After the reductive alkylation, the catalyst is re markedly improved quality over those obtained by the moved from the reaction mixture, for example, by filtra methods (1) to (3). Nevertheless, the product is still tion. The reaction mixture is then distilled while main unsatisfactory in quality, particularly considering that taining the bottom temperature at 160 C. or lower to the demand of N,N-diethylaminophenols for the pro 65 thereby substantially remove the unreacted acetalde duction of dyes for heat-sensitive or pressure-sensitive hyde and the solvent while recovering the N,N-die paper has recently been increasing. Thus, it has been thylaminophenol-containing bottom. The resulting bot keenly demanded to develop N,N-diethylaminophenols tom containing virtually no acetaldehyde or solvent is 4,967,004 3 4. further distilled while maintaining the bottom tempera by centrifugation. If desired, the filter cake may be ture at 200 C. or lower to recover a crude N,N-die subjected to rinse washing or repulp washing with thylaminophenol as a distillate. water having dissolved therein an acid sulfite and/or a The process of the present invention is characterized dithionite. The thus collected cake of the N,N-die in that the thus obtained crude N,N-diethylamino thylaminophenol is further worked-up, for example, by phenol is contacted with a solvent which is substantially drying to obtain a final product. incompatible with the N,N-diethylaminophenol and According to the present invention, N,N-die contains one or more of acid sulfites and dithionites in thylaminophenols can be obtained in good yield as a an inert gas atmosphere, and the resulting mixture is pale yellowish white or pale red solid without encoun then cooled to precipitate the N,N-diethylaminophenol O tering various problems associated with the conven for recovery. tional techniques.