RU2095342C1 - Method of inhibition of zeolite catalysts - Google Patents

Abstract

FIELD: preparation of nitrobenzene feedstock for synthesis of aniline, quinoline, and azobenzene. SUBSTANCE: benzene is nitrated with 68-70 % nitric acid used in 80 % excess on repeatedly used aluminosilicates (beta and mordenite) under continuous conditions at 105-130 C. Partial distillation of water from reaction space may be carried out. Nitrobenzene yield is increased by 1.25-1.55 times; nitrobenzene recovery is increased from catalyst volume unit. EFFECT: increased amount of the desired product in catalysate. 2 cl, 1 tbl

Description

 The invention relates to methods for nitration of benzene and can be used to produce nitrobenzene, which is a raw material for the synthesis of aniline, benzidine, quinoline, azobenzene. Nitrobenzene also has independent use.

By technology and environmental impact, the most promising way to nitrate benzene is nitration catalyzed by synthetic zeolites. The most often proposed gas-phase regimen (150 - 200 ^o C) [1] Nitrating agents are either 65 70% HNO ₃ with an excess of benzene [2] or nitrogen oxides [3] It is necessary to use a carrier gas.

 The main disadvantage of this use of zeolite is its quick deactivation. In addition, the elevated temperature promotes the occurrence of side reactions and complicates the hardware design of the process, and the result of excess benzene is the low productivity of the catalyst.

A variant of liquid-phase nitration of benzene in the presence of zeolite has also been proposed [4]
The closest to the proposed process for nitration of benzene is described in the patent [4]. Benzene, 61% HNO ₃ and zeolite ZSM-5 in H-form are introduced into the reaction vessel. The molar ratio of HNO ₃ : benzene is 1.9. The reaction is carried out at 75 ^o C for 2 hours. The yield of nitrobenzene is 34%, no formation of dinitro derivatives is observed. The productivity of the catalyst is 335 kg of nitrobenzene per 1 ton of zeolite in 1 h.

The disadvantages of the described method are the low reaction rate and yield of nitrobenzene and, as a consequence, the low productivity of the catalyst and the efficiency of the process, which is aggravated by its periodic mode of operation. In addition, there is no data on the possibility of reusing the catalyst and spent HNO ₃ , data on the processing of the nitration product, and on the content of other by-products, in addition to dinitrobenzene, in particular nitrobenzene.

 The purpose of this invention is the acceleration of the nitration reaction, the intensification of the reactor and the process as a whole with a moderate excess and circulating volume of nitric acid.

The goals are achieved by using as catalysts for nitration of benzene 68 with 70% nitric acid, zeolites such as beta and mordenite, synthesized according to the methods [5, 6] by nitration at 105 130 ^o C with 80% excess of HNO ₃ , or a combination of these conditions with partial distillation of water from the reaction space.

The essence of the latter technique consists in the distillation of part of the water from the reactor in the form of an azeotrope with benzene, as a result of which the concentration of HNO ₃ in the reaction medium slightly increases. This allows you to use one of the modifications of zeolite beta to accelerate the growth of technological indicators with an increase in nitration temperature by 20 - 25 ^o C, almost 2 times compared with the nitration option without distillation of water. For other zeolites, this technique increases the yield of nitrobenzene based on the consumed benzene.

The zeolites proposed in this invention have not yet received widespread use and were used in nitration in only two works during the process in the vapor phase [3, 7]
The proposed temperature range is due to the following circumstances: with 105 ^o C begins a steady excess of the proposed method over the prototype, and above 130 ^o C the nitration process when it is implemented in the liquid phase version loses stability.

 Benzene nitration was carried out in a plant with a cylindrical reactor made of glass or stainless steel having an inner diameter of 16.5 mm and a working zone height of 71–78 mm. There was a grate in the reactor to maintain the column of reaction-catalytic packing.

Thus, the hallmarks of the proposed method are:
the use of zeolites such as beta or mordenite;
conducting a nitration reaction at 105 130 ^o C;
partial distillation during nitration of water from the reaction space;
bringing nitration in a continuous mode with the return in the process of unreacted benzene and spent nitric acid. These distinctive features allow you to expand the range of catalysts for the nitration process, due to its intensification, increase 2.4 times the yield of nitrobenzene in one pass of reactants through the reactor, increase the removal of nitrobenzene from 1 ton of catalyst by 2.7 3.5 times, and from 1 m ³ 4.6 5.2 times.

 Methods for the synthesis of zeolites are illustrated by examples 1, 2. The essence of the method of nitration of benzene is illustrated by examples 3 8.

 The main conditions and results of nitration achieved in the prototype and examples of this invention are shown in the table.

Example 1. Synthetic mordenite is synthesized in the absence of organic substances with a SiO ₂ / Al ₂ O ₃ ratio of 9 + 10 [5] Ludox type silica sol is used as a silicon source, the synthesis temperature is maintained up to 100 ^o C. After the end of crystallization, the precipitate is filtered off, washed with distilled water and decationed three times with 1N. a solution of NH ₄ Cl + NH ₄ OH, followed by calcination at 460,480 ^o C. Before testing, the powder is pressed into tablets at a pressure of 100 kg / cm ² .

Example 2. Synthesis of zeolite beta. Beta type zeolite crystallizes in the presence of TEA-OH, used as an organic template. The method is taken from the patent [6] without any significant modifications: Solution A: 72.7 g of Ludox AS40. Solution B: 3.9 g of NaAlO ₂ in 30 g of water + 37 ML TEA-OH (40%). The gel obtained after adding solution A to solution B: (TEA) ₂ O) _2.8 (Na ₂ O) _0.9 (Al ₂ O ₃ ) _1.0 (SiO ₂ ) _27.1 (H ₂ O) ₁₆₆ was autoclaved for 10 days at 423 K. As a result, a zeolite beta with a SiO ₂ / Al ₂ O ₃ content of 31 was obtained. After the end of crystallization, the precipitate was filtered off, washed with distilled water and decated three times 1N. a solution of NH ₄ Cl + NH ₄ OH, followed by calcination at 460,480 ^o C. Before testing, the powder is pressed into tablets under a pressure of 100 kg / cm ² .

Example 3. A glass reactor is filled with glass and zeolite granules. The last component of the nozzle is one of the modifications of fresh zeolite beta synthesized according to the method [6] (example 2). The total mass of the nozzle is 13.34 g, volume is 15 ml. The reactor is placed in an oven, heated at 515 + 15 ^o C (the interval is determined by a temperature control system) with air purge (18 20 l / h) for 1.5 hours. The nozzle is cooled and nitration is carried out continuously for 9 hours at an average temperature of 120 ^o C, feeding benzene at a rate of 12.13 g / h and 69.5% nitric acid at a speed of 25.40 g / h to the reactor. The molar ratio of HNO ₃ : benzene is 1.8. The products leaving the reactor after stabilization of the process are processed: the aqueous and organic phases are separated; organic substances are extracted from one phase; the extract is combined with the organic phase; the mixture is washed with water, dried; the solvent is evaporated. If the aqueous phase is extracted with benzene, the extract is directed to nitration. For 6 hours, taking into account losses, 106.24 g of organic nitration products containing about 89% nitrobenzene, about 11% benzene, 0.4% nitrophenol, 0.07% dinitrobenzene are obtained. The yield of nitrobenzene on the consumed benzene is 97.5%. Nitrophenol can be removed from the resulting mixture by washing with a 5% NaOH solution. From the remaining mixture, vacuum distillation (residual pressure 40 mmHg) at 55 ^° C. in a cube and 30 ^° C. in vapors remove benzene, which is returned to nitration.

Example 4. The reactor is filled with granular glass and zeolite type beta, used in example 3 and regenerated by heating at 515 ± 15 ^o C with a purge of air (18 20 l / h) for 1.5 hours. Nitration is carried out under the conditions of example 3, for except for the temperature of the nozzle, which is 105 ^o C. Nitration products are processed according to the scheme described in example 3. For 6 hours of operation of the installation receive taking into account losses of 98.41 g of organic nitration products containing 83% nitrobenzene, 16.5% benzene, 0 , 2% nitrophenol; 0.02% dinitrobenzene. Purification of the crude nitrobenzene is carried out as described in example 3.

Example 5. After the nitration described in example 4, the reactor nozzle is regenerated by heating at 515 ± 15 ^o C with air blowing for 1.5 hours. The nitration is carried out at an average nozzle temperature of 120 ^o C, leaving the remaining parameters the same as in the example 3. The processing of catalysis is similar to the processing described in example 3. For 6 hours of nitration on the catalyst, which went through 2 cycles of nitration and regeneration, 97.67 g of organic products are obtained containing 81.5% nitrobenzene, 18% benzene, 0.3 % nitrophenol; 0.06% dinitrobenzene. Purification of crude nitrobenzene is carried out as in example 3.

Example 6. Granular glass and mordenite-type zeolite synthesized according to the procedure [5] and after 4 cycles of nitration (9 hours each) and regeneration were placed in a glass reactor. The total mass of the nozzle is 14.23 g, the volume is 13.8 ml. The reactor with the nozzle is prepared for the nitration process, as described in example 3. The reaction is carried out at an average nozzle temperature of 130 ^o C, feeding benzene and 68% nitric acid to the reactor. The benzene feed rate is 12.13 g / h, NHO _{3 is} 25.27 g / h. The molar ratio of HNO ₃ : benzene is 1.8. The catalyst collected for 6 hours of continuous operation of the installation is treated as described in Example 3. 96.29 g of a mixture of organic nitration products containing 79.5% nitrobenzene, more than 20% benzene, 0.25% nitrophenol, 0.03% are obtained. dinitrobenzene. Purification of crude nitrobenzene is carried out analogously to example 3.

Example 7. After the nitration cycle described in example 6, the reactor nozzle is regenerated by heating with air blowing at 515 ± 10 ^o C for 1.5 hours. After cooling the reactor to 100 ^o C, a 9-hour nitration cycle is carried out at 120 ^o C feeding benzene and 68% nitric acid to the reactor at the rates and in the ratio indicated in Example 63. The catalyst collected over 6 hours of continuous operation of the unit is treated as described in Example 3. 98.08 g of a mixture of organic nitration products are obtained. containing 83% nitrobenzene, 16.5% benzene, 0.2% nitrophenol, 0.03% dinitrobenzo a. Concentration and purification of this product is carried out analogously to example 3.

Example 8. A glass reactor having a device for draining from the reaction space and condensing part of an azeotropic benzene-water mixture is filled in the same way as described in example 3 using the same nozzle components. The total mass of the nozzle is 15.09 g, the volume is 15.5 ml. The reactor with the nozzle is prepared for operation as described in example 3. Nitration is carried out for 9 hours at an average nozzle temperature of 119 ^o C, feeding benzene and 70% nitric acid to the reactor at the rates and in the ratio given in example 3. Catalyst collected over 6 hours of continuous operation of the reactor, is treated analogously to example 3. Receive, taking into account the distillation of 106.62 g of organic products containing 87.5% nitrobenzene, 12% benzene, 0.4% nitrophenol, 0.07% dinitrobenzene. The yield of nitrobenzene to consumed benzene is 99.5%. Purification of the crude nitrobenzene is carried out as described in Example 3. 16.8 g of the organic phase (benzene) and 6.5 g of the aqueous phase, which is diluted nitrogen, are collected in the collection for products distilled from the reaction space. acid.

The final product obtained by the proposed method contains at least 99.8% nitrobenzene, less than 0.1% benzene, less than 0.1% dinitrobenzene, does not contain nitrophenol and corresponds to TU 6-36-0204208-107-89 for brand A nitrobenzene The yield of nitrobenzene on the consumed benzene is up to 99.5% of theoretical. Unreacted vacuum distillation benzene from crude nitrobenzene is returned to nitration. Spent HNO ₃ (concentration 52–55%) after strengthening with concentrated nitric acid also returns to nitration.

Thus, the proposed method of nitration in comparison with the known allows due to the intensification of the nitration process in 2.4 times to increase the yield of nitrobenzene; 2.7 3.5 times increase the removal of nitrobenzene from 1 ton and 4.6 5.2 times with 1 m ^{3 of} catalyst.

 These advantages, combined with the expansion of the range of catalysts used and the transition of the nitration process to continuous operation, enhance the technical and economic feasibility of the industrial implementation of the new benzene nitration process.

Information sources:
1. M.V. Gorelik, L.S. Efros. Fundamentals of chemistry and technology of aromatic compounds. M. Chemistry, 1992, p. 141.

 2. Bertea L.E. Kouwenhoven H.W. Prins R. Stud. Surf Sci. Catal. 1994, v. 84, p 1973 1980.

 3. N.F. Salakhutdinov, K.G. Ione, E.A. Kobzar L.V. Malysheva. Organ magazine Chemistry, 1993, v. 29, N 3, p. 546.

 4. Japanese patent 63-225339 (prototype).

 5. D.W. Breck. Zeolite Molecular Sieves. Wiley, New York, 1974, p. 162 - 163.

 6. US patent 3308069.

 7. W.F. Holderich and van Bekkum. Stud. Surf Sci. Catal. 1991, v. 58, p 677.

Claims (2)

1. The method of nitration of benzene with aqueous solutions of nitric acid in the presence of aluminosilicates when heated, characterized in that it is carried out continuously at 105 130 ^o With using 68 70% nitric acid, with the return of unreacted benzene and nitric acid to nitration, and as aluminosilicates take reusable zeolites such as beta and mordenite.  2. The method according to claim 1, characterized in that during the process, partial distillation of water from the reaction space is performed.

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