Method for producing ϵ-caprolactam

Abstract

A method produces ε-caprolactam through adipamide as an intermediate, and characteristically includes a lactamization step of reacting adipamide, formed from a material compound, with hydrogen and ammonia in the presence of a catalyst containing: a metal oxide mainly containing an oxide(s) of one or more metallic elements selected from the group consisting of metallic elements of group 5 and groups 7 to 14 in the 4th to 6th periods of the periodic table; and a metal and/or a metal compound having a hydrogenation ability.

Claims

1. A method of producing 5-cyanovaleramide through adipamide as an intermediate, the method comprising converting adipamide, formed from a material compound, to 5-cyanovaleramide in the presence of a metal oxide and a solvent, wherein the metal oxide an oxide of one or more metallic elements selected from the group consisting of metallic elements of group 5 and groups 7 to 14 in the 4th to 6th periods of the periodic table, wherein said material compound is a carboxylic acid represented by the following Formula (I) or (II): ##STR00009## wherein in Formula (I) and Formula (II), R′, R.sup.2, and R.sup.3 each independently represent a hydrogen atom (H) or an alkyl group having 1 to 6 carbon atoms; in Formula (I), X represents —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—, —CH.sub.2—CH.sub.2—CH═CH—, —CH.sub.2—CH═CH—CH.sub.2—, —CH═CH—CH═CH—, —CH.sub.2—CH.sub.2—CH.sub.2—CH(OH)—, —CH.sub.2—CH.sub.2—C(OH)H—CH.sub.2—, —CH═CH—C(OH)H—CH.sub.2—, —C(OH)H—CH.sub.2—CH═CH—, or —CH.sub.2—CH═CH—CH(OH)—; and, in Formula (II), Y represents —CH.sub.2—CH.sub.2— or —CH═CH—, or a salt or an ester thereof, or a mixture thereof; and wherein said oxide of one or more metallic elements constitutes only said oxide of said metallic element, or said oxide of one or more metallic elements is in the form of a composite metal oxide in which the oxide of said metallic element covers the surface of an oxide of a metallic element other than said metallic element wherein the ratio of said oxide of said metallic element in said composite metal oxide is 2% by weight to 80% by weight.

2. The method according to claim 1, wherein the material compound is one or more compounds selected from the following group of compounds: ##STR00010## or a salt(s) thereof, or a mixture thereof.

3. The method according to claim 1, wherein the material compound is one or more carboxylic acids selected from the group consisting of adipic acid, muconic acid, 3-hydroxyadipic acid, α-hydromuconic acid, 3-hydroxyadipic acid-3,6-lactone, and muconolactone, or a salt(s) thereof, or a mixture thereof.

4. The method according to claim 1, wherein the oxide of the metallic element is an oxide of one or more metallic elements selected from the group consisting of vanadium, niobium, tantalum, manganese, iron, cobalt, nickel, copper, zinc, gallium, indium, thorium, germanium, tin, and lead.

Description

EXAMPLES

(1) The present invention is described below in more detail by way of Examples. However, the present invention is not limited to the Examples below. In the Reference Examples, Examples, and Comparative Examples, the reaction results are defined according to the following equations.
Material compound conversion (%)=((Fed material compound (mol)−unreacted material compound (mol))/Fed material compound (mol)×100.
Selectivity of product (%)=amount of product formed (mol)/(Fed material compound (mol)−unreacted material compound (mol))×100.
Intermediate selectivity (%)=selectivity of 6-amino-6-oxohexanoic acid (%)+selectivity of adipamide (%).
ε-Caprolactam selectivity (%)=selectivity of 5-cyanovaleramide (%)+selectivity of 6-aminohexanamide (%)+selectivity of ε-caprolactam (%)+selectivity of hexamethyleneimine (%).
By-product selectivity (%)=selectivity of cyclopentylamine (%)+selectivity of cyclopentanecarboxamide (%).
By-product precursor selectivity (%)=selectivity of cyclopentanone (%)+selectivity of 1-cyclopenten-1-amine (%)+selectivity of cyclopentaneimine (%).

(2) Reaction solutions, and aqueous solutions of reaction solution concentrates were analyzed by gas chromatography (GC) and high-performance liquid chromatography (HPLC), respectively. The product was quantified with an absolute calibration curve prepared using standard samples. Quantitative analysis of 5-cyanovaleramide, ε-caprolactam, hexamethyleneimine, cyclopentylamine, cyclopentanecarboxamide, adiponitrile, cyclopentanone, 1-cyclopenten-1-amine, and cyclopentaneimine was carried out mainly by GC, and quantitative analysis of adipic acid, muconic acid, α-hydromuconic acid, 3-hydroxyadipic acid, 3-hydroxyadipic acid-3,6-lactone, muconolactone, 6-amino-6-oxohexanoic acid, adipamide, and 6-aminohexanamide was carried out mainly by HPLC. The analysis conditions of GC and HPLC were as follows.

(3) [GC Analysis Conditions]

(4) GC apparatus: GC2010 plus (manufactured by Shimadzu Corporation)

(5) Column: InertCap for amines; length, 30 m; inner diameter, 0.32 mm (manufactured by GL Sciences Inc.)

(6) Carrier gas: helium; constant linear velocity (40.0 cm/second)

(7) Vaporizing chamber temperature: 250° C.

(8) Detector temperature: 250° C.

(9) Column oven temperature: 100° C..fwdarw.(10° C./minute).fwdarw.230° C. for 3 minutes (16 minutes in total)

(10) Detector: FID.

(11) [HPLC Analysis Conditions]

(12) HPLC apparatus: Prominence (manufactured by Shimadzu Corporation)

(13) Column: Synergi hydro-RP (manufactured by Phenomenex Inc.); length, 250 mm; inner diameter, 4.60 mm; particle size, 4 μm

(14) Mobile phase: 0.1% by weight aqueous phosphoric acid solution/acetonitrile=95/5 (volume ratio)

(15) Flow rate: 1.0 mL/minute

(16) Detector: UV (210 nm)

(17) Column temperature: 40° C.

(Reference Example 1) Providing of α-Hydromuconic Acid (I−4)

(18) The α-hydromuconic acid used in the present invention was provided by chemical synthesis. First, 1.5 of super-dehydrated tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 13.2 g (0.1 mol) of succinic acid monomethyl ester (manufactured by Wako Pure Chemical Industries, Ltd.), and 16.2 g (0.1 mol) of carbonyldiimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto with stirring, followed by stirring the resulting mixture under nitrogen atmosphere at room temperature for 1 hour. To this suspension, 15.6 g (0.1 mol) of malonic acid monomethyl ester potassium salt (manufactured by Tokyo Chemical Industry Co., Ltd.) and 9.5 g (0.1 mol) of magnesium chloride (manufactured by Nacalai Tesque, Inc.) were added. The resulting mixture was stirred under nitrogen atmosphere at room temperature for 1 hour, and then stirred at 40° C. for 12 hours. After completion of the reaction, 0.05 of 1 mol/L hydrochloric acid was added to the mixture, and extraction with ethyl acetate was carried out. By separation purification by silica gel column chromatography (hexane:ethyl acetate=1:5), 13.1 g of pure 3-oxohexanedicarboxylic acid dimethyl ester was obtained. Yield: 70%.

(19) To 10 g (0.05 mol) of the 3-oxohexanedicarboxylic acid dimethyl ester obtained, 0.1 of methanol (manufactured by Kokusan Chemical Co., Ltd.) was added, and 2.0 g (0.05 mol) of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the resulting mixture with stirring, followed by stirring the mixture at room temperature for 1 hour. Subsequently, 0.02 of 5 mol/L aqueous sodium hydroxide solution was added thereto, and the resulting mixture was stirred at room temperature for 2 hours. After completion of the reaction, the pH was adjusted to 1 with 5 mol/L hydrochloric acid, and the mixture was then concentrated using a rotary evaporator. By recrystallization with water, 7.2 g of pure α-hydromuconic acid was obtained. Yield: 95%.

(20) .sup.1H-NMR (400 MHz, CD.sub.3OD): δ2.48 (m, 4H), δ5.84 (d, 1H), δ6.96 (m, 1H).

(Reference Example 2) Providing of 3-Hydroxyadipic Acid (I−10)

(21) The 3-hydroxyadipic acid used in the present invention was provided by chemical synthesis. First, 1.5 of super-dehydrated tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 13.2 g (0.1 mol) of succinic acid monomethyl ester (manufactured by Wako Pure Chemical Industries, Ltd.), and 16.2 g (0.1 mol) of carbonyldiimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto with stirring, followed by stirring the resulting mixture under nitrogen atmosphere at room temperature for 1 hour. To this suspension, 15.6 g (0.1 mol) of malonic acid monomethyl ester potassium salt (manufactured by Tokyo Chemical Industry Co., Ltd.) and 9.5 g (0.1 mol) of magnesium chloride (manufactured by Nacalai Tesque, Inc.) were added. The resulting mixture was stirred under nitrogen atmosphere at room temperature for 1 hour, and then stirred at 40° C. for 12 hours. After completion of the reaction, 0.05 of 1 mol/L hydrochloric acid was added to the mixture, and extraction with ethyl acetate was carried out. By separation purification by silica gel column chromatography (hexane:ethyl acetate=1:5), 13.1 g of pure 3-oxohexanedicarboxylic acid dimethyl ester was obtained. Yield: 70%.

(22) To 10 g (0.05 mol) of the 3-oxohexanedicarboxylic acid dimethyl ester obtained, 0.1 of methanol (manufactured by Kokusan Chemical Co., Ltd.) was added, and 0.02 of 5 mol/L aqueous sodium hydroxide solution was added to the resulting mixture with stirring, followed by stirring the mixture at room temperature for 2 hours. After completion of the reaction, the pH was adjusted to 1 with 5 mol/L hydrochloric acid. Subsequently, 2.0 g (0.05 mol) of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto, and the resulting mixture was stirred at room temperature for 2 hours. After completion of the reaction, the mixture was concentrated using a rotary evaporator. By recrystallization with water, 7.2 g of pure 3-hydroxyadipic acid was obtained. Yield: 95%.

(23) .sup.1H-NMR (400 MHz, CD.sub.3OD): δ1.70 (m, 1H), 61.83 (m, 1H), δ2.42 (m, 4H), δ4.01 (m, 1H).

(Reference Example 3) Providing of 3-Hydroxyadipic Acid-3,6-Lactone (II-1)

(24) The 3-hydroxyadipic acid-3,6-lactone used in the present invention was provided by chemical synthesis. First, 1.5 of super-dehydrated tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 13.2 g (0.1 mol) of succinic acid monomethyl ester (manufactured by Wako Pure Chemical Industries, Ltd.), and 16.2 g (0.1 mol) of carbonyldiimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto with stirring, followed by stirring the resulting mixture under nitrogen atmosphere at room temperature for 1 hour. To this suspension, 15.6 g (0.1 mol) of malonic acid monomethyl ester potassium salt (manufactured by Tokyo Chemical Industry Co., Ltd.) and 9.5 g (0.1 mol) of magnesium chloride (manufactured by Nacalai Tesque, Inc.) were added. The resulting mixture was stirred under nitrogen atmosphere at room temperature for 1 hour, and then stirred at 40° C. for 12 hours. After completion of the reaction, 0.05 L of 1 mol/L hydrochloric acid was added to the mixture, and extraction with ethyl acetate was carried out. By separation purification by silica gel column chromatography (hexane:ethyl acetate=1:5), 13.1 g of pure 3-oxohexanedicarboxylic acid dimethyl ester was obtained. Yield: 70%.

(25) To 10 g (0.05 mol) of the 3-oxohexanedicarboxylic acid dimethyl ester obtained, 0.1 of methanol (manufactured by Kokusan Chemical Co., Ltd.) was added, and 0.02 of 5 mol/L aqueous sodium hydroxide solution was added to the resulting mixture with stirring, followed by stirring the mixture at room temperature for 2 hours. After completion of the reaction, the pH was adjusted to 1 with 5 mol/L hydrochloric acid. Subsequently, 2.0 g (0.05 mol) of sodium borohydride (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto, and the resulting mixture was stirred at room temperature for 2 hours. After completion of the reaction, the mixture was concentrated using a rotary evaporator. By recrystallization with water, 7.2 g of pure 3-hydroxyadipic acid was obtained. Yield: 95%.

(26) .sup.1H-NMR (400 MHz, CD.sub.3OD): δ1.70 (m, 1H), 61.83 (m, 1H), δ2.42 (m, 4H), δ4.01 (m, 1H).

(27) To 7.2 g (0.044 mol) of the pure 3-hydroxyadipic acid obtained, 0.1 of ultrapure water was added, and 0.01 of 1 mol/L sulfuric acid was added thereto with stirring, followed by stirring the resulting mixture at 100° C. for 2 hours. After completion of the reaction, the mixture was concentrated using a rotary evaporator. By separation purification by silica gel column chromatography (chloroform:methanol=10:1), 5.8 g of pure 3-hydroxyadipic acid-3,6-lactone was obtained. Yield: 90%.

(28) .sup.1H-NMR (400 MHz, D.sub.2O): δ2.03 (m, 1H), δ2.04-2.90 (m, 5H), δ5.00 (m, 1H).

(Reference Example 4) Providing of Catalyst

(29) To an aqueous solution prepared by dissolving 0.13 g of palladium nitrate (Pd(NO.sub.3).sub.2.2H.sub.2O, manufactured by Alfa Aesar) in 10 mL of water, 1 g of niobium oxide (Nb.sub.2O.sub.5, manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the resulting mixture was stirred at room temperature for 3 hours. Water was evaporated using an evaporator at 20 mmHg at 40° C., and the resulting powder was dried at 110° C. overnight, followed by calcination under air flow at 500° C. for 4 hours. Subsequently, the powder was treated under hydrogen flow at 400° C. for 2 hours to thereby obtain 5% palladium-supporting niobium oxide (5% Pd/Nb.sub.2O.sub.5). Here, “5%” means that the ratio of palladium to the total weight of palladium and the metal oxide is 5% by weight at the time of feeding the materials. In addition, a different amount of palladium nitrate was used to obtain 1.7% palladium-supporting niobium oxide (1.7% Pd/Nb.sub.2O.sub.5).

(30) Similarly, tantalum oxide (Ta.sub.2O.sub.5, manufactured by Wako Pure Chemical Industries, Ltd.), zirconium oxide (ZrO.sub.2, reference catalyst JRC—ZRO-3 according to Catalysis Society of Japan), titanium oxide (anatase type) (TiO.sub.2, reference catalyst JRC-TIO-1 according to Catalysis Society of Japan), silicon dioxide (SiO.sub.2, CARiACT G6, manufactured by Fuji Silysia Chemical Ltd.), and α-iron oxide (α-Fe.sub.2O.sub.3, manufactured by Wako Pure Chemical Industries, Ltd.) were used instead of niobium oxide to prepare 5% palladium-supporting tantalum oxide (5% Pd/Ta.sub.2O.sub.5), 5% palladium-supporting zirconium oxide (5% Pd/ZrO.sub.2), 5% palladium-supporting titanium oxide (5% Pd/TiO.sub.2), 5% palladium-supporting silicon dioxide (5% Pd/SiO.sub.2), and 5% palladium-supporting α-iron oxide (5% Pd/α-Fe.sub.2O.sub.3), respectively. Similarly, nickel nitrate hexahydrate (Ni(NO.sub.3).sub.2.6H.sub.2O, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of palladium nitrate to prepare 5% nickel-supporting niobium oxide (5% Ni/Nb.sub.2O.sub.5), 10% nickel-supporting silicon dioxide (10% Ni/SiO.sub.2), and 20% nickel-supporting silicon dioxide (20% Ni/SiO.sub.2).

(31) Similarly, nickel nitrate hexahydrate and cobalt nitrate hexahydrate (Co(NO.sub.3).sub.2.6H.sub.2O, manufactured by Wako Pure Chemical Industries, Ltd.), or nickel nitrate hexahydrate and iron nitrate nonahydrate (Fe(NO.sub.3).sub.3.9H.sub.2O, manufactured by Wako Pure Chemical Industries, Ltd.), were used to prepare 10% nickel-10% cobalt-supporting silicon dioxide (10% Ni-10% Co/SiO.sub.2) or 10% nickel-10% iron-supporting silicon dioxide (10% Ni-10% Fe/SiO.sub.2), respectively.

(Reference Example 5) Preparation of Indium Oxide-Supporting Silicon Dioxide

(32) To an aqueous solution prepared by dissolving 2.62 g of indium nitrate trihydrate (In(NO.sub.3).sub.3.3H.sub.2O, manufactured by Wako Pure Chemical Industries, Ltd.) in 40 mL of water, 4.1 g of silicon dioxide (SiO.sub.2, CARiACT G6, manufactured by Fuji Silysia Chemical Ltd.) was added, and the resulting mixture was stirred at room temperature for 15 hours. Water was evaporated using an evaporator at 20 mmHg at 40° C., and the resulting powder was dried at 110° C. overnight, followed by calcination under air flow at 600° C. for 4 hours, to obtain 20% indium oxide-supporting silicon dioxide (20% In.sub.2O.sub.3/SiO.sub.2). Here, “20%” means that the ratio of indium oxide to the total weight of indium oxide-supporting silicon dioxide is 20% by weight.

(Reference Example 6) Production of ε-Caprolactam Using Adipamide as Material

(33) To a stainless steel autoclave having a capacity of 0.1 (manufactured by Taiatsu Techno Corporation), 0.144 g of adipamide (Tokyo Chemical Industry Co., Ltd.), 50 mL of dioxane (Wako Pure Chemical Industries, Ltd.), and 0.025 g of Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) were added. With stirring at 500 rpm at room temperature, the inside of the autoclave was purged with nitrogen, and ammonia gas was introduced thereto such that the partial pressure of ammonia gas in the autoclave was adjusted to 0.18 MPa (gauge pressure), followed by keeping the pressure for 45 minutes. Thereafter, while the stirring was continued, hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 0.72 MPa (gauge pressure) (total pressure (gauge pressure): 0.90 MPa). Subsequently, the temperature in the autoclave was increased to 250° C. After keeping the temperature at 250° C. for 3 hours, the autoclave was allowed to cool to room temperature, and the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. After addition of 50 mL of water, the reaction solution was mixed, and the catalyst was removed by centrifugation. The supernatant was then analyzed by GC and HPLC. The results are shown in Table 1.

(Reference Example 7) Production of ε-Caprolactam Using Adipamide as Material

(34) To a stainless steel autoclave having a capacity of 0.2 (manufactured by Taiatsu Techno Corporation), 0.3 g of adipamide (Tokyo Chemical Industry Co., Ltd.), 100 mL of dioxane (Kanto Chemical Co., Inc.), and 0.05 g of Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa Aesar) were added. With stirring at 1000 rpm at room temperature, the inside of the autoclave was purged with nitrogen, and ammonia gas was introduced thereto such that the partial pressure of ammonia gas in the autoclave was adjusted to 0.35 MPa (gauge pressure), followed by keeping the pressure for 45 minutes. While the stirring was continued, hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 1.35 MPa (gauge pressure) (total pressure (gauge pressure): 1.70 MPa). Subsequently, the temperature in the autoclave was increased to 250° C. for 1 hour. After keeping the temperature at 250° C. for 3 hours, the autoclave was allowed to cool to room temperature, and the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. After addition of 100 mL of water, the reaction solution was mixed, and the catalyst was removed by centrifugation. The supernatant was then analyzed by GC and HPLC. The results are shown in Table 1.

(Reference Example 8) Production of ε-Caprolactam Using Adipamide as Material

(35) A reaction was carried out in the same manner as in Reference Example 6 except that a mixture of 0.1 g of 10% nickel-supporting silicon dioxide and 0.05 g of α-iron oxide (10% Ni/SiO.sub.2+α-Fe.sub.2O.sub.3) was added instead of 5% Pd/Al.sub.2O.sub.3, and that the temperature in the autoclave was increased to 230° C. and then kept at 230° C. for 3 hours. After the autoclave was allowed to cool to room temperature, the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. The catalyst was removed by filtration, and the supernatant was analyzed by GC. The supernatant was concentrated with a rotary evaporator (Tokyo Rikakikai Co., Ltd.). An aqueous solution of the resulting concentrate was prepared, and analyzed by HPLC. The results are shown in Table 1.

(36) TABLE-US-00001 TABLE 1 Production of ε-caprolactam using adipamide as a material Adi- By- ε-Capro- pamide product lactam con- selec- selec- version tivity tivity Material Catalyst (%) (%) (%) Reference Adi- 5% Pd/Al.sub.2O.sub.3 76.9 36.7 46.6 Example 6 pamide Reference Adi- 5% Pd/Al.sub.2O.sub.3 98.3 25.8 53.9 Example 7 pamide Reference Adi- 10% Ni/SiO.sub.2 + 78.8 0.5 94.7 Example 8 pamide α-Fe.sub.2O.sub.3

(37) As shown in Reference Examples 6 and 7 in Table 1, in cases where adipamide was used as the material, and palladium-supporting aluminum oxide was used as the catalyst, remarkable formation of by-products that do not contribute to formation of ε-caprolactam occurred, resulting in insufficient ε-caprolactam selectivities. On the other hand, as shown in Reference Example 8, in the case where the catalyst to be used in the present invention was used, by-products that do not contribute to formation of ε-caprolactam decreased, resulting in a high ε-caprolactam selectivity.

(Reference Example 9) Providing of α-Hydromuconic Acid Dimethyl Ester (I−5)

(38) To 5.0 g (0.035 mol) of the α-hydromuconic acid obtained in Reference Example 1, 50 mL of methanol (manufactured by Kokusan Chemical Co., Ltd.) was added to dissolve the α-hydromuconic acid completely. A solution of diazomethane in diethyl ether (containing 0.07 mol of diazomethane) was added thereto with stirring, and the resulting mixture was stirred at room temperature for 3 hours. After completion of the reaction, methanol was removed by distillation using a rotary evaporator, and separation purification by silica gel chromatography (hexane:ethyl acetate=9:1) was carried out to obtain 5.4 g of pure α-hydromuconic acid dimethyl ester. Yield: 90%.

(39) .sup.1H-NMR (400 MHz, CDCl.sub.3): δ2.46-2.57 (m, 4H), δ3.69 (s, 3H), δ3.72 (s, 3H) δ5.86 (m, 1H), δ6.91-7.02 (m, 1H).

(Example 1) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(40) To a stainless steel autoclave having a capacity of 0.1 (manufactured by Taiatsu Techno Corporation), 0.146 g of adipic acid (manufactured by Wako Pure Chemical Industries, Ltd.), 50 mL of dioxane (manufactured by Wako Pure Chemical Industries, Ltd.), and 0.1 g of 5% palladium-supporting niobium oxide (5% Pd/Nb.sub.2O.sub.5) prepared in Reference Example 4 were added. The temperature in the autoclave was adjusted to 30° C., and, with stirring at a stirring rate of 500 rpm, the inside of the autoclave was purged with nitrogen, and ammonia gas was introduced thereto such that the partial pressure of ammonia gas in the autoclave was adjusted to 0.18 MPa (gauge pressure), followed by keeping the pressure for 45 minutes. Thereafter, while the stirring was continued, hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 0.72 MPa (gauge pressure) (total pressure (gauge pressure): 0.90 MPa). Subsequently, the temperature in the autoclave was increased to 250° C. After keeping the temperature at 250° C. for 3 hours, the autoclave was allowed to cool to room temperature, and the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. The catalyst was removed by filtration, and the supernatant was analyzed by GC. The supernatant was concentrated with a rotary evaporator (manufactured by Tokyo Rikakikai Co., Ltd.). An aqueous solution of the resulting concentrate was prepared, and analyzed by HPLC. The results are shown in Table 2.

(Example 2) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(41) A reaction was carried out in the same manner as in Example 1 except that 5% nickel-supporting niobium oxide (5% Ni/Nb.sub.2O.sub.5) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Example 3) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(42) A reaction was carried out in the same manner as in Example 1 except that 5% palladium-supporting tantalum oxide (5% Pd/Ta.sub.2O.sub.5) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Comparative Example 1) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(43) A reaction was carried out in the same manner as in Example 1 except that Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa Aesar) was used as the catalyst. The results are shown in Table 2.

(Comparative Example 2) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(44) A reaction was carried out in the same manner as in Example 1 except that 5% palladium-supporting zirconium oxide (5% Pd/ZrO.sub.2) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Comparative Example 3) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(45) A reaction was carried out in the same manner as in Example 1 except that 5% palladium-supporting titanium oxide (5% Pd/TiO.sub.2) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Comparative Example 4) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(46) A reaction was carried out in the same manner as in Example 1 except that 5% palladium-supporting silicon dioxide (5% Pd/SiO.sub.2) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Example 4) Production of ε-Caprolactam Using Muconic Acid (1-7) as Material Compound

(47) A reaction was carried out in the same manner as in Example 1 except that 0.142 g of trans, trans (t,t)-muconic acid (manufactured by Sigma-Aldrich) was used instead of adipic acid, that the stirring rate was set to 800 rpm, and that the temperature in the autoclave was increased to 180° C. and then kept for 1 hour, followed by increasing the temperature to 250° C. and keeping the temperature at 250° C. for 5 hours. The results are shown in Table 2.

(Comparative Example 5) Production of ε-Caprolactam Using Muconic Acid (1-7) as Material Compound

(48) A reaction was carried out in the same manner as in Example 4 except that Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) was used as the catalyst. The results are shown in Table 2.

(Example 5) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(49) A reaction was carried out in the same manner as in Example 1 except that 5% palladium-supporting α-iron oxide (5% Pd/α-Fe.sub.2O.sub.3) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Example 6) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(50) A reaction was carried out in the same manner as in Example 1 except that a physical mixture of 0.1 g of 10% nickel-supporting silicon dioxide prepared in Reference Example 4 and 0.05 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.) (10% Ni/SiO.sub.2+α-Fe.sub.2O.sub.3) was used as the catalyst. The results are shown in Table 2.

(Example 7) Production of ε-Caprolactam Using α-Hydromuconic Acid (I−4) as Material Compound

(51) A reaction was carried out in the same manner as in Example 4 except that 0.144 g of α-hydromuconic acid provided in Reference Example 1 was used, and that a temperature of 250° C. was kept for 3 hours. The results are shown in Table 2.

(Comparative Example 6) Production of ε-Caprolactam Using α-Hydromuconic Acid (I−4) as Material Compound

(52) A reaction was carried out in the same manner as in Example 7 except that Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) was used as the catalyst. The results are shown in Table 2.

(Example 8) Production of ε-Caprolactam Using 3-Hydroxyadipic Acid (I−10) as Material Compound

(53) A reaction was carried out in the same manner as in Example 4 except that 0.160 g of 3-hydroxyadipic acid provided in Reference Example 2 was used instead of muconic acid, and that 0.3 g of 1.7% palladium-supporting niobium oxide (1.7% Pd/Nb.sub.2O.sub.5) prepared in Reference Example 4 was used as the catalyst. The results are shown in Table 2.

(Comparative Example 7) Production of ε-Caprolactam Using 3-Hydroxyadipic Acid (I−10) as Material Compound

(54) A reaction was carried out in the same manner as in Example except that Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) was used as the catalyst. The results are shown in Table 2.

(Example 9) Production of ε-Caprolactam Using 3-Hydroxyadipic Acid-3,6-Lactone (II-1) as Material Compound

(55) To a stainless steel autoclave having a capacity of 0.1 (manufactured by Taiatsu Techno Corporation), 0.144 g of 3-hydroxyadipic acid-3,6-lactone provided in Reference Example 3, 50 mL of dioxane (Wako Pure Chemical Industries, Ltd.), and Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) were added. The temperature in the autoclave was adjusted to 30° C., and, with stirring at a stirring rate of 500 rpm, the inside of the autoclave was purged with nitrogen, and hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 0.90 MPa (gauge pressure). Subsequently, the temperature in the autoclave was increased to 230° C., and then the temperature was kept at 230° C. for 12 hours, followed by allowing the autoclave to cool to room temperature. The gas in the autoclave was released to allow the pressure to decrease to ambient pressure, and the reaction solution was recovered. Filtration was carried out to separate 5% Pd/Al.sub.2O.sub.3, and the supernatant was returned into the autoclave. After addition of 0.1 g of 5% palladium-supporting niobium oxide (5% Pd/Nb.sub.2O.sub.5) thereto, the temperature in the autoclave was adjusted to 30° C. With stirring at a stirring rate of 500 rpm, the inside of the autoclave was purged with nitrogen, and ammonia gas was introduced thereto such that the partial pressure of ammonia gas in the autoclave was adjusted to 0.18 MPa (gauge pressure), followed by keeping the pressure for 45 minutes. Thereafter, while the stirring was continued, hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 0.72 MPa (gauge pressure) (total pressure (gauge pressure): 0.90 MPa). Subsequently, the temperature in the autoclave was increased to 250° C. After keeping the temperature at 250° C. for 5 hours, the autoclave was allowed to cool to room temperature, and the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. The catalyst was removed by filtration, and the supernatant was analyzed by GC. The supernatant was concentrated with a rotary evaporator (Tokyo Rikakikai Co., Ltd.). An aqueous solution of the resulting concentrate was prepared, and analyzed by HPLC. The material conversion was 100%; the intermediate selectivity was 3.3%; the by-product selectivity was 2.8%; and the ε-caprolactam selectivity was 84.1%.

(Comparative Example 8) Production of ε-Caprolactam Using 3-Hydroxyadipic Acid-3,6-Lactone (II-1) as Material Compound

(56) Throughout the process, the reaction was carried out in the same manner as in Example 9 except that Palladium, 5% on gamma alumina powder, reduced (5% Pd/Al.sub.2O.sub.3, manufactured by Alfa aesar) was used as the catalyst. The material conversion was 100%; the intermediate selectivity was 6.7%; the by-product selectivity was 21.2%; and the ε-caprolactam selectivity was 60.5%.

(Example 10) Production of ε-Caprolactam Using Adipic Acid (I−1) as Material Compound

(57) A reaction was carried out in the same manner as in Example 1 except that a physical mixture of 0.05 g of 10% nickel-10% cobalt-supporting silicon dioxide prepared in Reference Example 4 and 0.05 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.) (10% Ni-10% Co/SiO.sub.2+α-Fe.sub.2O.sub.3) was used as the catalyst. The results are shown in Table 2.

(Example 11) Production of ε-Caprolactam Using Adipic Acid (I-1) as Material Compound

(58) A reaction was carried out in the same manner as in Example 10 except that 10% nickel-10% iron-supporting silicon dioxide (10% Ni-10% Fe/SiO.sub.2) was used instead of 10% nickel-10% cobalt-supporting silicon dioxide. The results are shown in Table 2.

(Example 12) Production of ε-Caprolactam Using α-Hydromuconic Acid (I-4) as Material Compound

(59) A reaction was carried out in the same manner as in Example 7 except that a physical mixture of 0.1 g of 10% nickel-supporting silicon dioxide and 0.1 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.) (10% Ni/SiO.sub.2+α-Fe.sub.2O.sub.3) was used as the catalyst. The results are shown in Table 2.

(Example 13) Production of ε-Caprolactam Using Diammonium Adipate as Material Compound

(60) A reaction was carried out in the same manner as in Example 1 except that 0.18 g of diammonium adipate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the material compound, that 50 mL of tert-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the solvent, that a physical mixture of 0.1 g of 20% nickel-supporting silicon dioxide, 0.05 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.), and 0.05 g of niobium oxide (manufactured by Wako Pure Chemical Industries, Ltd.) (20% Ni/SiO.sub.2+α-Fe.sub.2O.sub.3+Nb.sub.2O.sub.5) was used as the catalyst, and that the temperature in the autoclave was increased to 235° C. and then kept at 235° C. for 3 hours. The results are shown in Table 2.

(Example 14) Production of ε-Caprolactam Using Dimethyl Adipate (I-2) as Material Compound

(61) A reaction was carried out in the same manner as in Example 1 except that 0.18 g of dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the material compound, that 50 mL of 1,2-dimethoxyethane (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the solvent, and that a physical mixture of 0.05 g of 10% nickel-supporting silicon dioxide, 0.05 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.), and 0.05 g of niobium oxide (manufactured by Wako Pure Chemical Industries, Ltd.) (10% Ni/SiO.sub.2+α-Fe.sub.2O.sub.3+Nb.sub.2O.sub.5) was used as the catalyst. The results are shown in Table 2.

(Example 15) Production of ε-Caprolactam Using α-Hydromuconic Acid Dimethyl Ester (I-5) as Material Compound

(62) A reaction was carried out in the same manner as in Example 4 except that 0.17 g of α-hydromuconic acid dimethyl ester provided in Reference Example 9 was used as the material compound. The results are shown in Table 2.

(Comparative Example 9) Production of ε-Caprolactam Using Diammonium Adipate as Material Compound

(63) A reaction was carried out in the same manner as in Example 13 except that 0.1 g of 5% palladium-supporting titanium oxide (5% Pd/TiO.sub.2) was used as the catalyst. The results are shown in Table 2.

(64) TABLE-US-00002 TABLE 2 Production of ε-caprolactam from various material compounds Material Intermediate By-product compound selectivity selectivity ε-Caprolactam Material compound Catalyst Solvent conversion (%) (%) (%) selectivity (%) Example 1 Adipic acid 5% Pd/Nb.sub.2O.sub.5 Dioxane 100 5.0 2.9 82.6 Example 2 Adipic acid 5% Ni/Nb.sub.2O.sub.5 Dioxane 100 4.9 2.3 81.4 Example 3 Adipic acid 5% Pd/Ta.sub.2O.sub.5 Dioxane 100 11.3 2.4 81.9 Example 4 t,t-Muconic acid 5% Pd/Nb.sub.2O.sub.5 Dioxane 100 5.2 3.2 82.8 Example 5 Adipic acid 5% Pd/α-Fe.sub.2O.sub.3 Dioxane 100 8.1 3.9 78.0 Example 6 Adipic acid 10% Ni/SiO.sub.2, α-Fe.sub.2O.sub.3 Dioxane 100 2.9 2.5 83.2 Example 7 α-Hydromuconic acid 5% Pd/Nb.sub.2O.sub.5 Dioxane 100 13.4 2.3 76.2 Example 8 3-Hydroxyadipic acid 1.7% Pd/Nb.sub.2O.sub.5 Dioxane 100 6.8 2.3 78.6 Example 10 Adipic acid 10% Ni-10%Co/SiO.sub.2 + α-Fe.sub.2O.sub.3 Dioxane 100 11.8 1.2 70.5 Example 11 Adipic acid 10% Ni-10%Fe/SiO.sub.2 + α-Fe.sub.2O.sub.3 Dioxane 100 18.0 0.8 63.7 Example 12 α-Hydromuconic acid 10% Ni/SiO.sub.2 + α-Fe.sub.2O.sub.3 Dioxane 100 10.7 3.9 73.8 Example 13 Diammonium adipate 20% Ni/SiO.sub.2 + α-Fe.sub.2O.sub.3 + tert-Butanol 100 1.2 4.3 83.6 Nb.sub.2O.sub.5 Example 14 Adipic acid dimethyl 10% Ni/SiO.sub.2 + α-Fe.sub.2O.sub.3 + 1,2- 64 5.5 2.5 83.8 ester Nb.sub.2O.sub.5 dimethoxyethane Example 15 α-Hydromuconic acid 5% Pd/Nb.sub.2O.sub.5 Dioxane 81 7.3 2.0 77.2 dimethyl ester Comparative Adipic acid 5% Pd/Al.sub.2O.sub.3 Dioxane 100 7.8 20.1 66.4 Example 1 Comparative Adipic acid 5% Pd/ZrO.sub.2 Dioxane 100 0.7 20.4 67.0 Example 2 Comparative Adipic acid 5% Pd/TiO.sub.2 Dioxane 100 4.2 28.7 32.7 Example 3 Comparative Adipic acid 5% Pd/SiO.sub.2 Dioxane 100 84.6 11.2 0.5 Example 4 Cornparative t,t-Muconic acid 5% Pd/Al.sub.2O.sub.3 Dioxane 100 2.7 19.9 67.6 Example 5 Comparative α-Hydromuconic acid 5% Pd/Al.sub.2O.sub.3 Dioxane 100 13.7 17.9 59.1 Example 6 Comparative 3-Hydroxyadipic acid 5% Pd/Al.sub.2O.sub.3 Dioxane 100 12.3 13.2 61.1 Example 7 Comparative Diammonium adipate 5% Pd/TiO.sub.2 tert-Butanol 100 6.2 27.8 23.5 Example 9

(65) From the Examples in Table 2, it was shown that a compound from which adipamide can be formed, such as a carboxylic acid represented by General Formula (I) or (II), or a salt or an ester thereof, can be used as a material compound for ε-caprolactam.

(Example 16) Production of 5-Cyanovaleramide from Adipamide

(66) To a stainless steel autoclave having a capacity of 0.1 (manufactured by Taiatsu Techno Corporation), 0.144 g of adipamide (Tokyo Chemical Industry Co., Ltd.), 50 mL of dioxane (Wako Pure Chemical Industries, Ltd.), and 0.1 g of niobium oxide (Nb.sub.2O.sub.5, manufactured by Wako Pure Chemical Industries, Ltd.) were added. The temperature in the autoclave was adjusted to 30° C., and, with stirring at a stirring rate of 500 rpm, the inside of the autoclave was purged with nitrogen. Ammonia gas was introduced thereto such that the partial pressure of ammonia gas in the autoclave was adjusted to 0.18 MPa (gauge pressure), and then the pressure was kept for 45 minutes. Thereafter, while the stirring was continued, hydrogen was introduced thereto such that the partial pressure of hydrogen in the autoclave was adjusted to 0.72 MPa (gauge pressure) (total pressure (gauge pressure): 0.90 MPa). Subsequently, the temperature in the autoclave was increased to 250° C. After keeping the temperature at 250° C. for 1 hour, the autoclave was allowed to cool to room temperature, and the gas in the autoclave was released to allow the pressure to decrease to ambient pressure, followed by recovering the reaction solution. The catalyst was removed by filtration, and the supernatant was analyzed by GC. The supernatant was concentrated with a rotary evaporator (Tokyo Rikakikai Co., Ltd.). An aqueous solution of the resulting concentrate was prepared, and analyzed by HPLC. The results are shown in Table 3.

Example 17

(67) A reaction was carried out in the same manner as in Example 16 except that tantalum oxide (Ta.sub.2O.sub.5, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 18

(68) A reaction was carried out in the same manner as in Example 16 except that α-iron oxide (α-Fe.sub.2O.sub.3, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 19

(69) A reaction was carried out in the same manner as in Example 16 except that zinc oxide (ZnO, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 20

(70) A reaction was carried out in the same manner as in Example 16 except that indium oxide (In.sub.2O.sub.3, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 21

(71) A reaction was carried out in the same manner as in Example 16 except that tin oxide (SnO.sub.2, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 22

(72) A reaction was carried out in the same manner as in Example 16 except that lead oxide (PbO, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 23

(73) A reaction was carried out in the same manner as in Example 16 except that 20% indium oxide-supporting silicon dioxide (20% In.sub.2O.sub.3/SiO.sub.2) prepared in Reference Example 5 was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 10

(74) A reaction was carried out in the same manner as in Example 16 except that Aluminium oxide, gamma-phase (Al.sub.2O.sub.3, manufactured by Alfa Aesar) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 11

(75) A reaction was carried out in the same manner as in Example 16 except that zirconium oxide (ZrO.sub.2, reference catalyst JRC—ZRO-3 according to Catalysis Society of Japan) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 12

(76) A reaction was carried out in the same manner as in Example 16 except that silicon dioxide (SiO.sub.2, CARiACT G6, manufactured by Fuji Silysia Chemical Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 13

(77) A reaction was carried out in the same manner as in Example 16 except that magnesium oxide (MgO, reference catalyst JRC-MGO-3-1000A according to Catalysis Society of Japan) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 14

(78) A reaction was carried out in the same manner as in Example 16 except that scandium oxide (Sc.sub.2O.sub.3, manufactured by Mitsuwa Chemicals Co., Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 15

(79) A reaction was carried out in the same manner as in Example 16 except that cerium oxide (CeO.sub.2, reference catalyst JRC-CEO-3 according to Catalysis Society of Japan) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 16

(80) A reaction was carried out in the same manner as in Example 16 except that antimony oxide (Sb.sub.2O.sub.3, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Comparative Example 17

(81) A reaction was carried out in the same manner as in Example 16 except that bismuth oxide (Bi.sub.2O.sub.3, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 24

(82) A reaction was carried out in the same manner as in Example 16 except that triiron tetroxide (Fe.sub.3O.sub.4, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 25

(83) A reaction was carried out in the same manner as in Example 16 except that manganese dioxide (MnO.sub.2, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of niobium oxide. The results are shown in Table 3.

Example 26

(84) The reaction was carried out in the same manner as in Example 18 except that the temperature in the autoclave was set to 230° C., and that the temperature of 230° C. was kept for 1 hour.

Example 27

(85) A reaction was carried out in the same manner as in Example 16 except that a physical mixture of 0.1 g of α-iron oxide (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.1 g of silicon dioxide (CARiACT G6, manufactured by Fuji Silysia Chemical Ltd.) (α-Fe.sub.2O.sub.3+ SiO.sub.2) was used instead of niobium oxide. The results are shown in Table 3.

(86) TABLE-US-00003 TABLE 3 Production of 5-cyanovaleramide from adipamide Selectivity Selectivity By-product of 5-Cyano- of Adi- precursor Metal valeramide ponitrile selectivity oxide (%) (%) (%) Example 16 Nb.sub.2O.sub.5 70.7 14.8 0.9 Example 17 Ta.sub.2O.sub.5 82.5 5.5 1.9 Example 18 α-Fe.sub.2O.sub.3 75.0 7.2 1.4 Example 19 ZnO 85.9 1.0 5.8 Example 20 In.sub.2O.sub.3 80.7 8.3 0.9 Example 21 SnO.sub.2 71.7 2.3 3.1 Example 22 PbO 71.8 1.7 11.8 Example 23 20% 75.0 4.0 4.4 In.sub.2O.sub.3/ SiO.sub.2 Example 24 Fe.sub.3O.sub.4 70.5 1.2 12.0 Example 25 MnO.sub.2 68.8 2.6 9.1 Example 26 α-Fe.sub.2O.sub.3 82.7 3.4 4.0 Example 27 α-Fe.sub.2O.sub.3 + 75.3 10.2 2.5 SiO.sub.2 Comparative Al.sub.2O.sub.3 47.4 3.1 23.1 Example 10 Comparative ZrO.sub.2 39.1 17.2 14.4 Example 11 Comparative SiO.sub.2 29.7 Not 8.7 Example 12 detected Comparative MgO 16.5 Not 45.9 Example 13 detected Comparative Sc.sub.2O.sub.3 35.0 Not 5.1 Example 14 detected Comparative CeO.sub.2 2.3 12.3 43.1 Example 15 Comparative Sb.sub.2O.sub.3 11.3 Not 4.0 Example 16 detected Comparative Bi.sub.2O.sub.3 38.5 Not Not Example 17 detected detected

(87) From the results of the Examples shown in Table 3, it was shown that, in cases where a metal oxide mainly containing an oxide of a metallic element in group 5 or groups 7 to 14 in the 4th to 6th periods of the periodic table is used to perform a reaction to convert adipamide to 5-cyanovaleramide, formation of by-product precursors that do not contribute to formation of s-caprolactam can be suppressed, leading to a high selectivity of 5-cyanovaleramide. Furthermore, from the results of the Examples shown in Table 2, it was shown that, in cases where a catalyst containing: a metal oxide mainly containing an oxide of a metallic element in group 5 or groups 7 to 14 in the 4th to 6th periods of the periodic table, such as a metal oxide used in the Examples shown in Table 3; and a metal and/or a metal compound having a hydrogenation ability; is used, the selectivities of by-products that do not contribute to formation of s-caprolactam are low, and the ε-caprolactam selectivity is high.

(88) On the other hand, from the results of the Comparative Examples shown in Table 3, it was shown that, in cases where a metal oxide mainly containing an oxide of a metallic element other than the metallic elements of group 5 and groups 7 to 14 in the 4th to 6th periods of the periodic table is used alone to perform a reaction to convert adipamide to 5-cyanovaleramide, the selectivity of 5-cyanovaleramide is low, or large amounts of precursors of by-products that do not contribute to formation of ε-caprolactam are formed. Furthermore, from the results of the Comparative Examples shown in Table 2, it was shown that, in cases where a catalyst containing: a metal oxide mainly containing an oxide of a metallic element other than the metallic elements of group 5 and groups 7 to 14 in the 4th to 6th periods of the periodic table, such as a metal oxide used in the Comparative Examples shown in Table 3; and a metal and/or a metal compound having a hydrogenation ability; is used, the selectivities of by-products that do not contribute to formation of ε-caprolactam are high, and the ε-caprolactam selectivity is insufficient.

(89) As described above, it was shown that, in the method of producing 8-caprolactam using adipamide as an intermediate, by reacting adipamide, formed from a material compound, with hydrogen and ammonia in the presence of a catalyst containing: a metal oxide mainly containing an oxide(s) of one or more metallic elements selected from the group consisting of metallic elements of group 5 and groups 7 to 14 in the 4th to 6th periods of the periodic table; and a metal and/or a metal compound having a hydrogenation ability; side reactions from adipamide can be suppressed well, and the ε-caprolactam selectivity can be increased.