JPH11505230A - Method for producing caprolactam - Google Patents

Abstract

  (57) [Summary] In a process for producing a cyclic lactam by reacting aminocarbonitrile with water in the presence of a catalyst, this reaction is carried out in an amount ranging from 0.1 to 95% by weight, based on the total amount of titanium dioxide, of rutile. And a liquid phase in the presence of a heterogeneous catalyst based on titanium dioxide containing anatase in a proportion by weight of 99.9 to 5% by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel process for producing cyclic lactams by reacting aminocarbonitrile with water in the presence of a catalyst. U.S. Pat. No. 4,628,085 discloses a process in which 6-aminocapronitrile is reacted with water on acidic silica gel at a temperature of 300 DEG C. in the gas phase. This reaction is a quantitative reaction that initially forms caprolactam with a selectivity of 95%, but it is known that its productivity and selectivity are sharply reduced. A similar method is described in US Pat. No. 4,625,023, in which a highly diluted gaseous stream containing 6-aminocapronitrile, adiponitrile, ammonia, water and a carrier gas is mixed with silica gel and copper. Run over a / chromium / barium-titanium oxide catalyst. Caprolactam is obtained with a selectivity of 91% and a conversion of 85%. In this case, too, rapid catalyst deactivation is observed. No. 2,301,964 relates to the conversion of 6-aminocapronitrile to caprolactam in an aqueous solution at 285 ° C. under non-catalysis, but the conversion is 80% or less. French patent publication 0 209 540 describes a process for cyclizing 6-aminocapronitrile in aqueous solution to produce caprolactam using a homogeneous metal catalyst from zinc and copper. Although the yield is up to 83%, complete removal of the catalyst from the required product is difficult because it forms a complex with the metal used. Therefore, an object of the present invention is to provide a method for producing a cyclic lactam which does not have the above-mentioned disadvantages by reacting aminocarbonitrile with water. However, the above-mentioned object is based on titanium dioxide in the presence of a heterogeneous catalyst based on titanium dioxide, each containing 0.1 to 95% by weight of rutile and 99.9 to 5% by weight of anatase. It has now been found by the inventors that this is achieved by carrying out the reaction in the liquid phase. Preferred embodiments of the present invention are evident from the claims. The starting material used in the method of the present invention is aminocarbonitrile, especially a compound represented by the following formula (I). Here, n and m in the formula each mean any of 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, and the sum of n + m is at least 3, especially 4 Must. R ¹ and R ² in the formula may be any type of substituents, but it is necessary to prevent the necessary cyclization reaction from being performed by these substituents. It is preferred that R ¹ and R ² independently of _{one another represent} C ₁ -C ₆ alkyl, C ₅ -C ₇ cycloalkyl and C ₆ -C ₁₂ aryl, respectively. A particularly preferred starting compound is aminocarbonitrile of the formula H ₂ N— (CH ₂ ) m—C≡N where m means 3, 4, 5 or 6, especially 5. The starting material when m = 5 is 6-aminocapronitrile. In the method of the present invention, the above-mentioned aminocarbonitrile reacts with water in a liquid phase using a heterogeneous catalyst to form a cyclic lactam. Use of the aminocarbonitrile of formula I gives the corresponding cyclic lactam of formula II below. In the formula, n, m, R ¹ and R ² have the meanings described above, and it is preferred that n is 4, 5, 6, and especially 5 (in this case, caprolactam is obtained). The reaction is carried out in the liquid phase at a temperature of from 140 to 320 ° C., in particular from 160 to 280 ° C., a pressure of from 1 to 250 bar, in particular from 5 to 150 bar, but under the conditions in which the reaction mixture is used. Care must be taken to be generally liquid except for the catalyst present in the solid phase. In general, at least 0.01 mol, preferably 0.1 to 20 mol, in particular 1 to 5 mol, of water are used per mol of aminocarbonitrile. The aminocarbonitrile is used in the form of a 1 to 50% by weight, preferably 5 to 50, in particular 5 to 30% by weight aqueous solution (where the solvent is also a reactant) or a water / solvent mixture solution. Preferably. Examples of the solvent in this case include alkanols such as methanol, ethanol, n-, i-propanol, n-, i-, and t-butanol, polyols such as diethylene glycol and tetraethylene glycol, petroleum ether, benzene, and toluene. Hydrocarbons such as xylene, lactams such as pyrrolidone and caprolactam, alkyl-substituted lactams such as N-methylpyrrolidone, N-methylcaprolactam and N-ethylcaprolactam, especially carboxylic acids having 1 to 8 carbon atoms. . The reaction can also be performed in the presence of ammonia. Of course, mixtures of organic solvents can also be used. In particular, it is particularly preferred to use a water / alkanol mixture in a proportion by weight of 1 to 75 to 25 to 99, in particular 1 to 50 to 50 to 99. The process according to the invention makes it possible to obtain from 0.1 to 95, preferably from 1 to 90% by weight of rutile and from 99.5 to 5, in particular from 99 to 10% by weight of anatase, based on the total amount of titanium dioxide. The reaction is carried out in the presence of a titanium dioxide catalyst. In a preferred embodiment, the reaction is carried out in a fixed bed using the catalyst in the form of extrudates or tablets having a diameter of 1 to 10 mm. The extrudates or tablets can be prepared in a customary manner, already using the required amounts of dioxide powder containing anatase and rutile. Alternatively, starting from a modified form of pure anatase or from a mixed form consisting of anatase and rutile phases, or from a mixture of pure anatase and rutile modified forms, the appropriate temperature and time (eg, Catalysis, Today, 14 (1992) ), Pages 225-242), which are obtained by pyrolysis until the desired anatase / rutile ratio is achieved. (20-30% by weight of cellulose and 80-70% by weight of anatase)). It is commercially available as ze). Titanium dioxide can be used in neat form or as a supported catalyst, usually applied on a mechanically and chemically stable support having a large surface area. Titanium dioxide is a fine powder obtained from its aqueous solution, for example from a precipitate by a sulfate method or a pyrolysis method or other methods. If desired, the rutile / anatase containing titanium dioxide can be mixed with aluminum, zirconium, cerium oxide. There are several methods for producing these mixed oxides. Oxides or precursor compounds that can be converted to oxides by calcination can be precipitated in solution, for example, from solution. This method can result in a very good suspension of the two commonly used oxides. Precipitation of the oxide or a mixture of its precursors is also carried out by precipitating the first oxide or the precursor compound in the presence of the second oxide or the precursor compound in the form of a fine powder suspension. obtain. Another method consists in mechanically mixing the oxide or its precursor powder, in which case the mixture can be used as starting material for the production of extrudates or tablets. The preparation of the supported catalyst can also be carried out by several methods. That is, titanium dioxide in a sol state can be applied to a carrier by simple impregnation. Drying and calcination can remove volatile components of the sol from the catalyst. This type of gel for titanium dioxide is commercially available. Another method of forming a layer of activated titanium dioxide on a support involves hydrolyzing or pyrolyzing an organic or inorganic compound. That is, a thin layer thereof is formed on a ceramic carrier by hydrolysis of titanium isopropylate or other Ti alkoxide. A suitable Ti compound in this case is TiCl ₄ . Suitable carriers are titanium dioxide itself or other stable oxides, for example powders, extrudates or tablets of silicon dioxide. The carrier to be used can be made porous to improve its carrying capacity. When calcining this titanium dioxide, it is necessary to take care that the rutile phase and the anatase phase are in the above-mentioned amount ratio ranges. INDUSTRIAL APPLICABILITY The method of the present invention can produce a cyclic lactam, particularly caprolactam, with high yield and high selectivity, while maintaining constant catalytic activity. Experimental Example 1-7 A solution of 6-aminocapronitrile (ACN) dissolved in water and ethanol at the weight ratios shown in the following table was filled with titanium dioxide in the form of a tablet or extruded product, and the internal volume was 25%. It was fed to a milliliter (diameter 6 mm, length 800 mm) heated tubular reactor under a pressure of 100 bar. The flow product discharged from the reactor was analyzed by gal chromatography and the results are also shown in the table below.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, L U, MC, NL, PT, SE), UA (AM, AZ, BY) , KG, KZ, MD, RU, TJ, TM), AU, BG , BR, CA, CN, CZ, HU, JP, KR, MX, NO, NZ, PL, SG, SK, TR, UA, US (72) Inventor Flick, Clemens             Germany, D-76863, Herksheim,             Am, Bildsteckel, 16

Claims (1)

[Claims] 1. In a process for producing a cyclic lactam by reacting aminocarbonitrile with water in the presence of a catalyst, the reaction is carried out by a rutile in a proportion ranging from 0.1 to 95% by weight, based on the total amount of titanium dioxide. And a liquid phase in the presence of a heterogeneous catalyst based on titanium dioxide containing anatase in a proportion by weight of 99.9 to 5% by weight. 2. The method characterized in that the reaction is carried out at a temperature in the range from 140 to 320 ° C. 3. Represented by the formula _{H 2 N- (CH 2) m} -C≡N, characterized by the use of amino carbonitrile in which m in the formula means a 3, 4, 5 or 6, claim 1 or Method 2. 4. A method characterized by using 6-aminocapronitrile as aminocarbonitrile. 5. 5. The process according to claim 1, wherein an aqueous solution or a water / organic solvent solution of aminocarbonitrile having a concentration of 1 to 50% by weight is used.