RU2110511C1 - Method for producing aminobenzoic acids - Google Patents

Abstract

FIELD: organic chemistry; production of ortho-, metha- and para-aminobenzoic acids for use as intermediates for synthesis of pharmaceuticals, dyes, antioxidants, developers and other chemicals. SUBSTANCE: aminobenzoic acids are produced by liquid-phase hydrogenation of corresponding precursor nitrobenzoic acids or their alkali salts, in presence of support-borne palladium-containing catalysts, namely: palladium-modified and iron-containing nickel catalyst, or iron-containing palladium catalyst. Nickel catalyst contains 0.07-0.25% and 0.05-0.3% of iron based on weight of support, nickel-to-palladium weight ratio in catalyst is 1:1-0.5. Palladium catalyst contains 0.07-0.6% of palladium and 0,05-0.55% of iron based on weight support. Palladium is applied onto support by adsorption from aqueous solutions of palladium chlorohydroxy complex compounds prepared with alkali metal hydroxide-to-palladium weight ratio of 0.25-0.65:1. High-purity aminobenzoic acids are produced with yield 85-95% of theoretical. EFFECT: higher process output. 4 cl

Description

 The invention relates to a method for producing o-, m-, p-aminobenzoic acids by catalytic hydrogenation of the corresponding nitrobenzoic acids.

 Aminobenzoic acids (ABA) and their water-soluble salts are intermediate compounds in the synthesis of pharmaceuticals, dyes, antioxidants, developers and other products; in industry, they are obtained by reduction of the corresponding nitrobenzoic acids (NSCs) with zinc and iron. This process is characterized by significant disadvantages, including the low purity of the target product and a large amount of non-recyclable waste.

 The use of heterogeneous catalysts, for example, based on platinum metals and rhenium, is considered more promising for obtaining ABA [1]. However, the lack of quantitative indicators does not allow us to evaluate the activity and effectiveness of these catalysts.

 The synthesis of ABA, especially p-ABA, by hydrogenation of the corresponding NSC is sufficiently covered in known sources of information [2-4].

 A known method of catalytic reduction of p-NSC in the aquatic environment [2]; the process in this case is limited by the amount of p-NSC that is in solution, and in order to increase the productivity of the process, it is proposed to use a suspension of p-NSC. To maintain p-NSC in suspension, a high stirring rate is required to increase the productivity of the process, it is proposed to use a thin suspension of nitro compounds (≤ 8 wt.% P-NSC).

.The catalyst used in the process is platinum, palladium or their oxides at a concentration of at least 0.025% by weight of the starting nitro compound, while the activity of the catalyst is <

.

.An improvement of the known method [2] consists in the proposal to hydrogenate a mixture of salts of p-NBK (ammonium and sodium), maintaining the pH of the medium in a very narrow range (7.0 - 7.5) [3]. As a catalyst, platinum or palladium supported on coal or their oxides are used. At a concentration of precious metal catalyst ≈0.01% by weight of p-NSC, its activity is ≈

.

 A known method of producing p-ABA by hydrogenation of a "solution consisting of p-NBA and an aqueous solution of 0.95 - 1.0 equivalents of a compound (hydroxide or carbonate, or bicarbonate) of an alkali metal" [4]. Substantially hydrogenation is carried out in an aqueous solution of the alkaline salt of p-NSC, in which up to 5% p-NSC is present (if the ratio of alkaline reagent and p-NSC in the mixture is <1.0). The range of permissible pH values is much wider than in [3], and is 5–7 units.

, соответственно концентрация драгметалла - 0,005% от массы п-НБК. Производительность процесса по этому способу не превышает

. Основным недостатком известного способа является недостаточно высокая активность катализатора, а следовательно, и его производительность по целевому продукту п-АБК.Palladium, platinum, rhodium, ruthenium (or their oxides, or mixtures thereof), possibly supported on carriers (coal, Al, Si, and others), are used as catalysts, moreover, the composition may contain 0.5 - 25 wt.% Active component (preferably 1 to 5%). The maximum activity of the catalyst, calculated according to the examples of the described method [4], is

, respectively, the concentration of precious metal is 0.005% by weight of p-NSC. The performance of the process by this method does not exceed

. The main disadvantage of this method is the insufficiently high activity of the catalyst, and hence its performance in the target product p-ABA.

 The purpose of the invention is, without complicating the method of hydrogenation, significantly increase the productivity of the process, i.e. the removal of the target product from a unit of precious metal per unit of time, which leads to a proportional decrease in the cost of the target product.

 The goal is achieved by the proposed method of liquid-phase hydrogenation of NSCs or their alkaline salts in the presence of a nickel catalyst on a carrier modified with palladium and containing iron, or in the presence of a palladium catalyst on a carrier containing iron, moreover, the palladium in the catalysts is supported by adsorption from an aqueous solution of its chlorohydroxy complexes, obtained at a mass ratio of alkali metal hydroxide: palladium, equal to 0.25 - 0.65: 1.

 The nickel catalyst contains 0.07 - 0.25% nickel, 0.05 - 0.3% iron by weight of the carrier and the ratio of nickel: palladium in the catalyst is 1: 1 - 0.5, and the palladium catalyst contains 0.07 - 0 , 6% palladium and 0.05 - 0.55% iron by weight of the carrier.

 Hydrogenation of nitrobenzoic acid is preferred as an aqueous solution of ammonium, sodium or potassium salt, or as an aqueous solution of a mixture thereof. Hydroxides, carbonates, ammonium, sodium, and potassium bicarbonates are used as an alkaline reagent to obtain these salts.

 Nickel and iron are deposited on a carrier by adsorption from aqueous solutions of their salts (chlorides, nitrates, sulfates, etc.).

 As a catalyst carrier, traditional materials are used - activated carbons, oxides, aluminum, silicon, etc.

Hydrogenation of NSC on the proposed catalysts is carried out in a wide range of temperature and pressure of hydrogen, however, an excess of temperature of 110 ^o C is undesirable, as it leads to a deterioration in the quality of the final product. It is irrational to use pressure above 20 atm, since this does not give visible advantages.

 The method of preparation of the catalyst. In separate containers prepare solutions A, B, C.

A - a solution of palladium chlorohydroxocomplexes is prepared by reacting palladium chloride and an alkali metal chloride in an acidic aqueous medium, followed by alkaline hydrolysis, which is carried out by dosed addition of an alkali solution to a mass ratio of alkali metal hydroxide: Pd = 0.25 ^o C0.65.

B - an aqueous solution of nickel salts (chloride, acetate, nitrate, etc.) with a concentration of 0.01 - 0.2 g / mol • l ^-1 .

In - an aqueous solution of iron salts (chlorides, sulfates, nitrates) with a concentration of 0.01 - 0.2 g / mol • l ^-1 .

 The support is suspended in a neutral or alkaline aqueous solution, the concentration of the support in the suspension varies between 6.5 and 20 wt.%, The alkaline medium is achieved by adding an alkali solution (the support is alkaline to obtain a nickel catalyst on a support modified with palladium and containing iron). A carrier suspended in an aqueous medium is treated in a certain sequence with solutions A, B, C, varying their concentrations and volumes depending on the desired metal content in the catalyst and the conditions of its synthesis (reactor capacity, for example).

 Although the sequence of deposition of metal compounds to some extent affects the activity of the resulting catalysts, this effect is not decisive.

 Preparation in this way the catalysts do not need preliminary reduction.

 The preparation of catalysts is described in more detail in Examples 1a - 6a.

 A. Preparation of catalysts.

 Example 1a The catalyst is prepared in a laboratory setup consisting of a round-bottomed flask with a capacity of 500 ml, equipped with a stirrer, thermometer, dropping funnel and refrigerator and heated with a mantle heater, as well as a Bunsen flask with a funnel for filtering under vacuum.

Under stirring, 10 g (calculated on dry basis) of active carbon OU-A and 100 ml of distilled water are loaded into the flask. Coal is suspended in water at room temperature. A solution of palladium chlorohydroxocomplexes (CGC Pd) is preliminarily prepared. For this purpose, 1 ml of distilled water, 0.0017 ml of concentrated hydrochloric acid, 0.023 g of palladium chloride (59.5% Pd) and 0.02 g of potassium chloride are loaded into a 10 ml glass. The mixture is heated to 65 - 70 ^o C and stirred on a magnetic stirrer until the palladium salt is completely dissolved. The resulting solution was cooled to 40-50 ^o C and hydrolyzed, slowly, dropwise dosing, 1 N potassium hydroxide solution to a mass ratio of KOH: Pd = 0.65 and holding for 2 hours

A solution of nickel chloride is also preliminarily prepared by dissolving 0.101 g of NiCl ₂ • 6H ₂ O salt in 2 ml of distilled water at room temperature, and a solution of FeCl ₃ • 6H ₂ O iron chloride (0.092 g in 27 ml of water).

The coal suspension is heated to 65 - 70 ^o C and alkalinized with a 1 N potassium hydroxide solution to pH≥10.0, then a solution of nickel chloride is dosed and a 30-minute exposure is performed. The suspension is cooled to ≈30 ^o C, after which the iron chloride solution is dosed and the pH adjusted to 9.5 with 1 N KOH solution followed by a 15-minute exposure.

 The HCG Pd solution is dosed to the suspension and kept for 30 minutes.

 The catalyst suspension thus obtained is filtered under vacuum on a Buchner funnel, the paste is washed with distilled water until there are no chlorine ions in the wash water (silver nitrate sample) and dried in a vacuum desiccator to a residual moisture content of 20-30 wt%.

 The finished catalyst contains 0.25 wt. % nickel, 0.12 wt.% palladium, 0.3 wt.% iron (according to atomic absorption analysis).

 Example 2. The synthesis of the catalyst is carried out in a laboratory setup described in example 1A.

 A pre-prepared solution of CHA Pd (as in example 1a): a mixture of 0.0131 g of palladium chloride and 0.0055 g of potassium chloride is dissolved in 1 ml of distilled water, acidified with 0.001 ml of concentrated hydrochloric acid, followed by hydrolysis with a 0.25 N potassium hydroxide solution to a mass ratio of KOH: Pd = 0.45.

 10 g of finely dispersed chromatographic alumina in 100 ml of distilled water are suspended in a flask.

6.8 ml of a pre-prepared solution of iron chloride (FeCl ₂ • 4H ₂ O) with a concentration of 0.01 g mol / L, then 3.8 ml of a 1% solution of sodium carbonate and 12.5 ml of 10% are dosed to the suspension sodium bicarbonate solution, after which the suspension is kept under stirring for 30 minutes.

 The prepared HCA Pd solution is dosed to the stirred suspension and, after the obtained exposure, the catalyst paste is separated by vacuum filtration. Washing and drying of the catalyst is carried out as in example 1A. The finished catalyst contains (based on the dry weight of the product) 0.07% palladium and 0.05% iron.

 Example 3a The catalyst is prepared in a laboratory setup described in example 1A.

 10 g (calculated on dry basis) of the carbon carrier of the Sibunit brand are suspended in 100 ml of distilled water.

A pre-prepared solution of CHC Pd (2.5 ml of H ₂ O, 0.006 ml of HCl, 0.1 g of palladium chloride, 0.033 g of sodium chloride, hydrolysis of 0.25 N sodium hydroxide solution to a mass ratio of NaOH: Pd = 0.5), which after exposure for 15 to 20 minutes is dosed to a suspension of the carrier at t = 50 ^o C.

The suspension is kept under stirring for 20-30 minutes, then 7.4 ml of a solution of Fe chloride (FeCl ₂ • 4H ₂ O) with a concentration of 0.1 g mol / L, 4.1 ml of a 10% solution of Na carbonate and 65 ml of a 10% solution of Na bicarbonate, after which the suspension is kept under stirring for ≈ 30 min, filtered, the catalyst is washed and dried, as described in example 1a, to a residual moisture content of 20-30%. The finished catalyst contains 0.6 wt.% Palladium and 0.5 wt.% Iron (calculated on the weight of the dry product).

 Example 4a The catalyst is prepared in an installation consisting of an enameled synthesis reactor with a capacity of 160 l, equipped with a heating jacket, stirrer and refrigerator, a suction filter and a glass dispenser.

With stirring, 50 - 70 l of distilled water and 5 kg (based on the weight of the dry product) of active carbon OU-B are loaded. The suspension is dosed from the dosing tank for ≈ 10 minutes. a solution of iron sulfate obtained by dissolving 25 g of FeSO ₄ • 7H ₂ O in 1 liter of water. Then a ≈ 10% solution of sodium carbonate (125 g of Na ₂ CO ₃ in 1100 ml of water) is dosed and the contents of the reactor are heated to 65 - 70 ^o C.

Using an IN NaOH solution, the pH of the suspension, which decreases during hydrolysis to 8.0 - 8.5, is adjusted to a value of ≥10, after which a solution of nickel nitrate (25 g of Ni (NO ₃ ) ₂ • 6H ₂ O in 800 l of water is dosed ) and incubated for 30 min at a temperature of 65 - 70 ^o C then, the suspension is cooled to 50 ^o and dosed with 320 ml of a solution of HGC Pd for ≈ 10 minutes

The CHC Pd solution is preliminarily prepared in a container with a stirrer by dissolving 8.5 g of palladium chloride and 5.5 g of sodium chloride in 250 ml of distilled water acidified with 0.6 ml of concentrated hydrochloric acid when heated to 60 - 70 ^° C, after which the solution is cooled to 40 - 50 ^o C and hydrolyzed IN with a NaOH solution to a mass ratio of NaOH: Pd = 0.45, followed by exposure for 2 hours. After applying the PgC, the suspension was kept under stirring for 30 minutes, then filtered on a suction filter under vacuum wash the catalyst paste to the absence of chlorine ions in romyvnoy water and squeeze excess moisture from the vacuum.

 The finished catalyst is a paste (40 - 50 wt.% Water) containing, according to atomic absorption analysis (based on the weight of the dry product), 0.12 wt.% Nickel, 0.11 wt.% Palladium, 0.13 wt. .% iron.

 Example 5 a. The catalyst is prepared in a laboratory setup described in example 1A.

 In a flask with the stirrer on, 10 g of finely dispersed silica gel of the KSK brand are suspended in 100 ml of distilled water. Preliminarily, a HGC Pd solution is prepared: 0.034 g of palladium chloride and 0.023 g of sodium chloride are dissolved in 1.0 ml of water, acidified with 0.0025 ml of concentrated hydrochloric acid, after which the mixture is hydrolyzed with IN NaOH solution (NaOH: Pd = 0.55 wt.) and incubated for 3.5 hours. The resulting HCA Pd solution is metered to a suspension of coal at room temperature and neutral pH.

After 30 minutes of exposure of the suspension, a solution of FeCl ₃ • 6H ₂ O iron chloride is metered (0.092 g in 10 ml of water), then 15 ml of a 1% sodium carbonate solution and 54 ml of a 10% sodium bicarbonate solution until the pH of the suspension is ≈ 9 , 0 with exposure for 30 min.

The suspension is filtered under vacuum, the catalyst paste is washed on the filter, and then dried in a vacuum desiccator to a residual moisture content of 20-30 wt.%
According to atomic absorption analysis, the catalyst contains 0.20 wt.% Palladium and 0.27 wt.% Iron (calculated on the weight of the dry product).

 Example 6a The catalyst is prepared on the installation described in example 1A. 20 g (calculated on dry) of chromatographic alumina are suspended in 200 ml of distilled water.

 Pre-prepared solutions of CHC Pd, salts of nickel and iron. 0.0238 g of palladium chloride and 0.0154 g of sodium chloride are dissolved in 0.5 ml of distilled water, acidified with 0.001 ml of concentrated hydrochloric acid, as described in example 1a, then hydrolyzing the mixture with a solution of NaOH (NaOH: Pd = 0.5 wt. ) and maintain the resulting solution of CHC Pd for 2 hours

A suspension of Al ₂ O _{3 is} heated to 65 - 70 ^o C and with the help of an IN NaOH solution, its pH is adjusted to a value of ≥10 (10 - 11). After that, a pre-prepared solution of nickel sulfate NiSO ₄ • 7H ₂ O (0.0672 g in 25 ml of water) is dosed and the hot suspension is kept for 30 minutes.

The suspension is cooled to ≈ 50 ^o C, after which a solution of CHC Pd is dosed, followed by exposure for 30 minutes, then a solution of iron sulfate FeSO ₄ • 7H ₂ O (0.049 g in 1 ml of water), the pH is adjusted to 9.5 IN with a solution NaOH and produce a 30-minute exposure.

 The catalyst is filtered on a Buchner funnel under vacuum and washed from chlorine ions, then dried in a vacuum desiccator to a residual moisture content of 20-30 wt.%.

 The catalyst thus prepared contains (based on the weight of the dry product) 0.07 wt.% Nickel, 0.07 wt.% Palladium and 0.05 wt.% Iron.

 Example 7a The catalyst is prepared in a laboratory setup described in example 14a.

 Under stirring, 10 g (calculated on dry basis) of active carbon OUB (Fe content — 0.03 wt.%) And 10 ml of distilled water are loaded into the flask. Pre-prepared solution of HGC Pd (2.5 ml of water, 0.005 ml of concentrated hydrochloric acid, 0.075 g of palladium chloride, 0.025 g of sodium chloride, hydrolysis with 0.25 N sodium hydroxide solution to a mass ratio of NaOH: Pd = 0.25, holding for 24 hours ) dosed at room temperature to a suspension of coal and kept with stirring for 30 to 40 minutes

 The suspension of the catalyst is processed as in example 1A and get a paste with a moisture content of 20-30% and a palladium content of 0.45 wt.%, Iron 0.27 wt.% (Calculated on the weight of the dry product).

 B. Obtaining ABA.

 In the following examples of synthesis of ABA by hydrogenation of NSC, three types of plants are used.

Type 1 - laboratory kinetic hydrogenation unit at constant temperature and pressure of hydrogen. The reactor is a glass ampoule with a volume of 45 - 55 cm ³ , sealed in a steel thermostatic casing of the shaking device, connected through a valve system with hydrogen and nitrogen cylinders, a buffer tank and a measuring system. The system is heated using a thermostat. Heat carriers - glycerin or water, the temperature is regulated by a contact thermometer. The presence of a buffer tank in the system ensures that the process is conducted at almost constant pressure.

 After the process is over, hydrogen is replaced with nitrogen in the system. The catalyst is separated from the reaction mass by hot vacuum filtration (if necessary, the catalyzate is heated) in an ice-cooled receiver, where the isolation of ABA is then carried out upon cooling (or neutralization of the alkaline salt solution of ABA).

 Type II is a laboratory kinetic hydrogenation unit at normal hydrogen pressure. Glass duck reactor with a jacket for the coolant is fixed in a shaking device. The reactor and the measuring burette are heated (the process is monitored by the amount of absorbed hydrogen) using a thermostat. Isolation of ABA is similar to the previous one.

 Type III - a batch pilot plant, includes a hydrogenation reactor, a filter for separating the catalyst, a crystallizer (with a jacket for cooling), in which, if necessary, neutralization of the alkaline salt of ABA with HCl solution, a nutsc filter to separate the paste of ABA from the mother liquor can be carried out.

 The reactor is a vertical cylindrical apparatus with a volume of 25 l with a turbine stirrer (n = 2800 rpm), equipped with a heating jacket, a built-in coil for cooling, a loading hatch and a lower fitting for the release of the product.

Hydrogenation is carried out at a constant pressure of hydrogen in polythermal mode. After the termination of hydrogen uptake and 10–15 min of exposure, the hydrogen is replaced by nitrogen and, under a pressure of 3–4 atm, the reaction mixture is pumped through a heated filter (volume 1 l, filtering surface 0.14 m ² ) to a crystallizer (volume 100 l, n - 43 rpm), where, if necessary, a preliminary neutralization of the alkaline salt of ABA can be carried out. The mold is cooled to a temperature of 5 - 10 ^o C by supplying refrigerant to the jacket. The precipitated ABA crystals are filtered on a suction filter and washed with chilled water.

 Example 1b Hydrogenation of p-NSC is carried out on a laboratory kinetic installation of type II.

при загрузке его по Pd ≈ 0,0042% от массы п-НБК.30 ml of H ₂ O, 1 g of p-NSC and 0.035 g of the catalyst prepared according to Example 1a (NO 25 wt.%, Pd 0.12 wt.%, Fe 0.3 wt.%) Are loaded into the reactor. The hydrogenation process at normal hydrogen pressure and a temperature of 30 ^o C ends in ≈40 min with 100% hydrogen absorption. The activity of the catalyst is

when loading it at Pd ≈ 0.0042% by weight of p-NSC.

.After the hydrogenation has been completed, heated water is fed into the reactor jacket to increase the temperature of the catalyst to 80 ^° C, while the resulting p-ABA is completely transferred to the solution. The catalyst is separated by hot filtration from the solution, and the p-ABA solution is cooled to a temperature of 4-5 ^° C in a crystallization vessel through which argon is passed, while crystals of the target product are isolated with a yield of 90.0% of theory, with a color of 6.5 ^° C , mp 186.5 - 187.8 ^o C at 100% conversion of the starting nitro compound. Process performance

.

 Example 2b Hydrogenation is carried out in a type I installation.

16 ml of an alkaline solution of p-NSC (20% solution in aqueous alkali at a molar ratio of NaOH: p-NSC = 0.86) and the catalyst prepared according to example 3a (content of Pd wt.%, Fe 0.55 wt.%) in an amount of 0.6% by weight of p-NSC. The hydrogenation process of p-NSC at a hydrogen pressure of 10 ati and a temperature of 100 ^o C ends in 45 minutes with 100% (from theory) absorption of hydrogen.

. Катализатор отделяют горячей вакуумной фильтрацией в охлаждаемый приемник, где катализат при температуре ≈ 5^oC нейтрализуют разбавленной соляной кислотой до pH 4,0. Выпавшие белые кристаллы п-АБК отфильтровывают и промывают холодной водой. После сушки в вакууме полученные белые кристаллы (2,34 г ≈ 95% выход от теории) имеют цветность 5,2^oC т.пл. = 187,2 - 188,0^oC, в амине отсутствует исходное нитросоединение. Производительность процесса

.In terms of Pd, the concentration of the catalyst is 0.0036% by weight of p-NSC, the activity of the catalyst

. The catalyst is separated by hot vacuum filtration into a cooled receiver, where the catalyzate at a temperature of ≈ 5 ^o C is neutralized with dilute hydrochloric acid to a pH of 4.0. The precipitated white crystals of p-ABA are filtered off and washed with cold water. After drying in vacuum, the obtained white crystals (2.34 g ≈ 95% yield from theory) have a color of 5.2 ^o C mp = 187.2 - 188.0 ^o C, in the amine there is no initial nitro compound. Process performance

.

 Example 3b Hydrogenation of p-NSC is carried out in a type I installation.

, концентрация катализатора (по Pd) - 0,0027% от п-НБК.Download: 3.3 g of p-NBC, 10 ml of H ₂ O, 0.53 g of Na ₂ CO ₃ , 0.7 ml of 25% aqueous ammonia, 0.02 g of the catalyst according to example 7a (Pd 0.45 wt. %, Fe 0.27% by weight). The process is carried out at a pressure of 5 atm and a temperature of 90 ^o C, the theoretical amount of hydrogen is absorbed in 45 minutes. Catalyst activity

, the concentration of catalyst (according to Pd) is 0.0027% of p-NSC.

.Isolation of the product is carried out according to example 2b. Received p-ABA has so pl. 187.5 - 188.0 ^o C, color 3.4 ^o C, nitro compounds - otts. Yield - 90.3 ^o C from theory, process productivity

.

 Example 4b. For the hydrogenation of p-NSC on the catalyst according to example 4a (Ni 0.12 wt.%; Pd 0.11 wt.%, Fe 0.13 wt.%), A type III plant is used.

Downloads: p-NSC 3 kg, catalyst 39 g, KOH 1,056 kg, H ₂ O 15 l. (the molar ratio of KOH: p-NSC in this case is 1.05).

при концентрации палладия 0,001% от массы п-НБК.The hydrogenation process is carried out at a constant pressure of hydrogen (10 ami) and in the polythermal mode (t _beg = 60 ^o C, t _con = 110 ^o C). Theoretical hydrogen uptake is achieved in 1.5 hours. Catalyst activity

at a palladium concentration of 0.001% by weight of p-NSC.

.After the absorption of hydrogen has ceased, hot nitrogen pressure catalysis is pumped through a filter in a crystallizer, where, with stirring, the catalysis is cooled to ≈ 15 ^° C, after which, with constant stirring, a 15% HCl solution is metered until the pH of the aqueous filtrate reaches 3 , 8 - 4.0. The p-ABA crystals are separated by vacuum filtration on a suction filter, washed with cold water and dried. Yield 85.5% of theory, color 8.3 ^o C, mp. 186.3 - 187.5 ^o C, the residual nitro compounds - rel. Process performance

.

 Example 5b. Hydrogenation of o-NSC is carried out in a type I installation.

при концентрации Pd 0,00016% от массы о-НБК. Выделение продукта ведут по примеру 2б. Выход о-АБК 89,2%, т.пл. 146,5 - 147,3^oC, цветность 9,8^oC, содержание остаточных нитросоединений < 0,05 мас.%. Производительность процесса

Пример 6б. Гидрирование проводят в условиях установки типа I.Download: 3 g of o-NBC, 12 ml of H ₂ O, 0.2 g of NaOH, 0.9 Na HCO ₃ , 0.024 g of the catalyst of example 5a (Pd content of 0.2 wt.%, Fe 0.27 wt.% ) At a hydrogen pressure of 20 ati, a temperature of 60 ^{o, the} absorption of hydrogen is completed after 1.5 hours. The activity of the catalyst

at a concentration of Pd of 0.00016% by weight of o-NSC. Isolation of the product is carried out according to example 2b. The output of o-ABA 89.2%, so pl. 146.5 - 147.3 ^o C, color 9.8 ^o C, the content of residual nitro compounds <0.05 wt.%. Process performance

Example 6b. Hydrogenation is carried out in a type I installation.

при концентрации Pd 0,00117% от массы м-НБК.Download: 3 g m-NBC, 12 ml H ₂ O, 0.75 g NaOH, 0.05 g of the catalyst according to example 6a (Ni content 0.07 wt.%, Pd 0.07 wt.%, Fe 0.05 wt.%). At a hydrogen pressure of 15 atm and a temperature of 100 ^o C, the absorption of H ₂ ceases after 70 minutes Catalyst activity

at a Pd concentration of 0.00117% by weight of m-NSC.

.Isolation is carried out according to example 2b. The yield of m-ABA 93.4%, so pl. 179, -180.0 ^o C, color 5.1 ^o C. Residual nitro compounds - Ots. Process performance

.

 Example 7b Hydrogenation of o-NSC is carried out in a type I installation.

Download: 3.3 g of o-NBC, 0.83 g of NaOH, 10 ml of H ₂ O, 0.025 g of the catalyst according to example 4a (Ni 0.25 wt.%, Pd 0.12 wt.%), Fe 0.3 wt.%). At a pressure of 25 atm and a temperature of 100 ^o C after 80 minutes, the theoretical amount of hydrogen is absorbed.

.The concentration of the catalyst (according to Pd) was 1.89 • 10 ^-3 % by weight of o-NSC, activity

.

.The output of o-ABA 90.3%, so pl. 146.8 - 147.5 ^o C, color 8.7 ^o C, the content of residual nitro compounds <0.05 wt. % Process performance

.

 Example 8b. Hydrogenation of m-NSC is carried out in a type I installation.

.Download: 3.3 g m-NBC, 1.16 g KOH, 10 ml H ₂ O, 0.05 g of the catalyst of example 2a (Pd content 0.07 wt.%, Iron 0.05 wt.%). Temperature 100 ^o C, pressure 15 atm, reaction time 95 min. The concentration of the catalyst (according to Pd) amounted to 1.06 • 10 ^-3 % by weight of m-NSC, activity

.

.The output of m-ABA 92.8%, so pl. 179.2 - 179.8 ^o C, color 5.9 ^o C, residual nitro compounds - Ots. Process performance

.

(при концентрации драгметалла в катализаторе ≤ 0,005 (0,001 - 0,005)% от массы НБК.The activity of the catalyst in the proposed method for hydrogenation of NSC depends to some extent on their composition, but in all cases it exceeds

(at a concentration of precious metal in the catalyst ≤ 0.005 (0.001 - 0.005)% by weight of the NSC.

 The proposed method allows to significantly increase the productivity of the process and to obtain ABA of a high degree of purity, the yield is determined by the solubility of ABA in water at the temperature of planting, the initial concentration of NBA and is 85 - 95% of theory.

Claims (4)

 1. The method of producing aminobenzoic acids by liquid-phase catalytic hydrogenation of the corresponding nitrobenzoic acids or their alkaline salts in the presence of a palladium-containing catalyst on a support, characterized in that the catalyst used is palladium-modified nickel or palladium catalysts containing iron.  2. The method according to claim 1, characterized in that the catalyst contains palladium supported by adsorption from an aqueous solution of its chlorohydroxocomplexes obtained from palladium chloride by alkaline hydrolysis at a mass ratio of alkali metal hydroxide and palladium equal to 0.25 - 0.65: one.  3. The method according to claim 1, characterized in that the nickel catalyst contains 0.07 - 0.25% nickel, 0.05 - 0.3% iron by weight of the carrier and the ratio of nickel: palladium in the catalyst is 1: 1 - 0 ,5.  4. The method according to claim 1, characterized in that the palladium catalyst contains 0.07 - 0.6% palladium and 0.05 - 0.55% iron by weight of the carrier.