RU2087463C1 - Method of nitration of benzene - Google Patents

Abstract

FIELD: preparation of nitrobenzene stock for synthesis of aniline, benzidine, quinoline, and azobenzene. SUBSTANCE: benzene is nitrated with 65-70% nitric acid on alumosilicates (ZSM-5 and ZSM-11 modified with iron oxides) and/or glass granular packing at 70-90 C under continuous conditions at nitric acid to benzene molar ratio of 1.4- 4.5. Alumosilicates are used many times and unreacted benzene and nitric acid are recycled for nitration. Yield is 39-82%. EFFECT: continuous benzene and nitric acid closed cycle conditions, reaction is accelerated by 2-2!5 times, catalyst efficiency increased by 1!2-3!5 times, and yield is increased by 1!1-2!4 times. 3 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, benzadine, quinoline, azobenzene. Nitrobenzene also has independent use.

In industry, the nitration of benzene is carried out by a nitrating mixture (356% HNO ₃ , 50% H ₂ SO ₄ , 15% H ₂ O) in a cascade of capacitive reactors at a temperature of 60-70 ^o C [1] The molar ratio of HNO ₃ to benzene is 0.95 -0.98.

 The main disadvantage of this method is the presence of large quantities (0.0-1.0 tons per 1 ton of nitrobenzene) of difficultly utilized spent sulfuric acid. In addition, the resulting nitrobenzene contains impurities of dinitrobenzene and nitrophenol.

In a number of articles and patents, modifications of the above method are described: adiabatic [2] and azeotropic [3] nitration. The essence of the first modification is to accelerate the reaction by increasing the temperature along the flow of reagents through the reactors to 140 ^o C. The essence of the second modification is the continuous removal of water from the reaction medium in the form of an azeotrope with excess benzene, as a result of which it is possible to return sulfuric acid to nitration without treatment . Possessing some advantages, the described variants of homogeneous nitration do not eliminate sulfuric acid from the process and require an elevated temperature.

A number of patents and articles suggest heterogeneous-catalytic methods for nitration of aromatic compounds, including benzene. The vast majority of these methods have any significant drawback: either the catalyst is expensive and difficult to reach [4], the reaction conditions are difficult (temperature up to 300 ^o C [5]), or the process efficiency is low [6] In some cases, it is necessary to use activating sulfuric additives acid, acetic anhydride [7]). The most promising is the use of synthetic zeolites as solid catalysts. The most frequently proposed gas-nitration regimen is gas-phase (170 ^o C). Nitrating agent 65-70% nitric acid with an excess of benzene. Carrier gas required [8]
The main disadvantage of this use of zeolite is its quick deactivation. In addition, elevated temperature contributes to the occurrence of adverse reactions and complicates the hardware design of the process.

The closest to the proposed method the process of nitration of benzene is described in the patent [9]. The reaction was carried out in a glass vessel in the presence of zeolite ZSM-5 (0.8 g per 1 ton of benzene). 5 g of benzene and 12.5 g of 61% nitric acid were introduced into the vessel. The molar ratio of HNO ₃ to benzene is 1.89. The mixture was stirred for 2 hours at 75 ^° C. The yield of nitrobenzene free of dinitro derivatives was 34%. The catalyst productivity was 335 kg per 1 ton of zeolite in 1 hour.

 The disadvantages of the described method are the low reaction rate and yield of nitrobenzene and, as a result, the low productivity of the catalyst and the efficiency of the process, which is aggravated by its periodic mode of operation. There is no data on the possibility of reuse of the catalyst and spent nitric acid, data on the processing of the nitration product, on the content in it of other, except dinitrobenzene, by-products, in particular nitrophenol.

 The purpose of the invention is the acceleration of the nitration reaction, increasing the productivity of the catalyst, the intensification of the reactor and the process as a whole. The second goal is to create a continuous process with a closed cycle on benzene and nitric acid.

 The tasks are achieved by continuously swaying the reagents through a layer of zeolite of type ZSM-5 or type ZSM-11 of a certain composition and (or) a layer of a glass nozzle, filled in the reactor, in combination with an increased concentration of nitric acid against the prototype, transferring the nitration process to a continuous mode with a decrease the duration of contact of the reagents in the catalyst, repeated use of the catalyst after regeneration, return to nitration of unreacted benzene and spent nitric acid.

, имеющие следующие химические формулы:
(0,02-0,03)Na₂O•Al₂O₃•(27-150)SiO₂ •(0,09-0,5)Fe₂O₃
Отличительной особенностью способа синтеза таких цеолитов является применение следующей последовательности стадий: получение цеолитного порошка из алюмокремнегеля, силикагеля, смеси силикагелей различного состава или метасиликата натрия в присутствии или отсутствии спиртов, в присутствии одного или нескольких изоморфнозамещающих элементов (алюминию, железо) при температуре не выше 175^oC в течение не менее 4 ч; промывка синтезированного порошка до нейтральной pH; удаление органического соединения (спирта) с одновременным декатионированием (удалением части катионов Na) путем обработки раствором HNO₃ с концентрацией не более 10% при температуре не выше 100^oC в течение не более 4 ч; промывка цеолитного порошка дистиллированной водой; сушка цеолитного порошка при температуре не выше 110^oC. В процессе кристаллизации цеолитов при введении в реакционную смесь, поступающую на гидротермальную обработку, соединений (источников) катионов железа происходит модификация алюмосиликатного каркаса цеолитов.It is proposed to use zeolites with channel sizes in the range of 5.1-5.6

having the following chemical formulas:
(0.02-0.03) Na ₂ O • Al ₂ O ₃ • (27-150) SiO ₂ • (0.09-0.5) Fe ₂ O ₃
A distinctive feature of the method for the synthesis of such zeolites is the application of the following sequence of stages: obtaining a zeolite powder from alumina-silica gel, silica gel, a mixture of silica gels of various compositions or sodium metasilicate in the presence or absence of alcohols, in the presence of one or more isomorphous substituting elements (aluminum, iron) at a temperature of no higher than 175 ^o C for at least 4 hours; washing the synthesized powder to a neutral pH; removal of the organic compound (alcohol) with simultaneous decationation (removal of part of the Na cations) by treatment with a solution of HNO ₃ with a concentration of not more than 10% at a temperature not exceeding 100 ^o C for no more than 4 hours; washing the zeolite powder with distilled water; drying of the zeolite powder at a temperature of no higher than 110 ^o C. In the process of zeolite crystallization, when the iron cation compounds (sources) are introduced into the reaction mixture entering the hydrothermal treatment, the zeolite aluminosilicate framework is modified.

 The proposed sequence of stages for the preparation of zeolite catalysts ensures their activity in reactions proceeding according to the acid-base mechanism, and is described in examples 1, 2.

 A granular glass nozzle is obtained by grinding and sieving glass.

Nitration on these zeolites is carried out with nitric acid at a concentration of 65-70% at a temperature of 70-90 ^o C, the molar ratio of nitric acid to benzene is 1.4-4.5. The productivity of the catalyst is in the range of 400-1188 kg of nitrobenzene per 1 ton per 1 hour (392-864 kg per 1 m ³ in 1 h).

The above ranges of moles of oxides per mole of Al ₂ O ₃ given in the generalized chemical formula of zeolites provide a rational combination of the activity of the catalysts with their selectivity. An increase in the relative content of modifying additives (aluminum, iron) leads to a sharp acceleration of adverse reactions, and a decrease in the content of modifying additives leads to a decrease in catalyst activity and a deterioration of technological parameters.

 When using glass granular packing as a catalyst, technological parameters are reduced, but the technology is simplified.

The aluminosilicate catalysts were regenerated by any method, for example, by blowing air at a temperature of 500 ^o C for 1.5 hours

A decrease in the concentration of nitric acid to 65% reduces the technological results by about 20%. An increase in the concentration of HNO _{3 in} excess of 70% irreversibly deactivates the zeolite.

The implementation of nitration in the temperature range of concentrations of HNO ₃ with differentiation depending on the type of catalyst and some technological parameters leads to a rational combination of intensity and selectivity of the reaction.

 The amount of excess nitric acid can be selected depending on the desired end result: an increase in excess increases the degree of conversion of benzene and the yield of nitrobenzene in one pass through the reactor, but impairs the purity of the product.

 In the accepted ranges of nitration conditions, the competitiveness of the proposed method is maintained.

 A tube made of glass or stainless steel with an inner diameter of 16 mm and a working zone height of 80 mm, with a grate on which aluminosilicates were poured, was used as a reactor. Reagents were brought to the working area through a system of tubes.

Thus, the hallmarks of the proposed method are:
1. The use of zeolites of the type ZSM-5 or ZSM-11 with a molar ratio of SiO ₂ / Al ₂ O ₃ equal to 27-150, modified with small amounts of iron cations, as well as glass granular packing.

 2. Repeated reuse of the nozzle of the reactor, catalyzing the nitration reaction.

 3. The continuous process of nitration, which reduces losses, waste, stabilization of the quality of the product, which does not contain dinitrobenzene and nitrophenol.

 The above distinguishing features allow us to expand the range of catalysts for the benzene nitration process, accelerate the nitration reaction by 2.5–5 times, increase the yield of nitrobenzene 1.1–2.4 times, and increase the catalyst productivity by 1.2–3.5 times. The basis is created for the efficient continuous production of nitrobenzene.

 The essence of the method is illustrated by the following examples.

Example 1. The reaction mixture for the synthesis of zeolite powder is prepared by mixing in 158 ml of water finely dispersed 0.98 g of seed of zeolite and 31.63 g of powder brand SHSK-G containing 91.6% SiO ₂ and 0.33% Al ₂ O ₃ , with successive addition of the following solutions with stirring: 3.65 ml of 0.5 M sodium aluminate; 5.1 ml of 0.28 M iron chloride; 15.5 ml of 0.2 M boric acid; 8.8 ml of 11.7 M sodium hydroxide and 12.3 ml of butyl alcohol.

The mixture was kept at 170-175 ^o C for 4 hours. The zeolite mass obtained by synthesis was washed with excess alkali from the filter water with water, then a triple amount of a 6% HNO ₃ solution was added to it (which corresponds to a liquid to solid ratio of 3), heated to 90 ^o C and maintained with stirring for 0.5 hours

Then the mass is filtered off, washed with distilled water to a pH of 4-5 and dried at a temperature of 110 ^o C.

The chemical formula of the final product:
0.02Na ₂ O • Al ₂ O ₃ • 150SiO ₂ • 0.5Fe ₂ O ₃
The structure and composition of the zeolite corresponds to the type ZSM-11.

 Example 2. The synthesis of zeolite is carried out analogously to example 1, but 20.3 ml of a 0.5 M solution of sodium aluminate are added to the reaction mixture.

The chemical formula of the finished product:
0.3Na ₂ O • Al ₂ O ₃ • 27SiO ₂ • 0.09Fe ₂ O ₃
The structure and composition of the zeolite corresponds to the type ZSM-5.

Example 3. A glass reactor having a support grid for a nozzle is filled with glass granules 1-1.5 mm in size. The mass of the nozzle in the working area of 15.21 g (11.6 ml). The nozzle is heated for 1.5 hours at 135 ^o C with a purge of 17 l / h of air. Cool the reactor to 80 ^o C.

Continuously pumped through the reactor for 12 hours at an average nozzle temperature of 81-83 ^o C benzene (speed of 5.9 ml / h) and 68.6% nitric acid (speed of 19.6 ml / h). The molar ratio of HNO ₃ : benzene is 4.5. The nitration products are collected in a receiver, the organic layer is separated from the aqueous layer. Organic substances were extracted from the aqueous layer with methyl chloride, the extract was combined with the organic layer, the mixture was washed with water, dried with sodium sulfate, filtered, and the solvent was evaporated. Obtain 79.22 g of nitration products containing 92.2 nitrobenzene, 7.2 benzene, 0.15% nitrophenol, 0.4% unidentified impurities. Dinitrobenzene is absent. Nitrophenol can be removed from the resulting mixture by washing with a 2.5% NaOH solution. From the remaining mixture, vacuum distillation (residual pressure 60-70 mm Hg) at 40 ^° C. remove benzene, which is returned to nitration. Spent nitric acid (concentration of 59.4%) after strengthening is also returned to nitration. The output of nitrobenzene in one pass through the reactor is 72%. The productivity of the nozzle of the reactor for nitrobenzene is 1 hour per 1 ton and 1 m ^3, respectively 400 kg and 525 kg.

Example 4. The working zone of the glass reactor is filled (bottom to top) with a glass nozzle (cylinders 1-1.5 mm in diameter, 3-6 mm long; granules 1-1.5 mm in size and ZSM-11 type zeolite obtained under the conditions of Example 1 The mass and volume of glass particles is 5.4 g, 4.5 ml, The mass and volume of zeolite is 5.58 g, 8.1 ml, The reactor is heated by an oven to 500 ^o C and purged with air (20 l / h) at 500-525 ^o C for 1.5 hours. Cool the reactor to 80 ^° C. for 4.7 hours. Nitrate at an average temperature of 76 ^° C. Pumping benzene (5.9 ml / h) and 69.5% nitric acid through the reactor (18.1 ml / h). Molar ratio of HNO ₃ : be nzol 4.2 After the treatment described in example 3, 30.68 g of a mixture containing 94.8% nitrobenzene, 4.8% benzene, 0.4% nitrophenol are obtained, dinitrobenzene is absent, nitrobenzene is released in one pass through the reactor 75 % Productivity of the reactor nozzle for nitrobenzene in 1 hour per 1 ton 560 kg, per 1 m ³ 488 kg.

Example 5. 5.57 g (4.5 ml) of the glass nozzle used in Example 4 is poured onto the glass reactor grate and on top of it 4.56 g (8.5 ml) of ZSM-5 type zeolite obtained under the conditions of Example 2 and having passed three nitration and regeneration cycle. The reactor is calcined and cooled, as described in example 4, and nitration is carried out continuously for 21.9 hours at an average temperature of 81-84 ^o C, pumping benzene (12 ml / h) and 70% nitric acid (12 ml / h). The molar ratio of HNO ₃ : benzene is 1.4. The mixture collected in the receiver at the outlet of the reactor is separated into organic and aqueous phases.

The organic phase is washed with water (0.39 g per 1 ton of the organic phase), 2.6% sodium hydroxide solution (0.17 g per 1 g of the organic phase) and again with water (0.33 per 1 g of the organic phase). Dry the mixture with sodium sulfate (0.024 g per 1 g of the organic phase), decanter the liquid. Obtain 295.0 g of a mixture of organic products containing 51.7% nitrobenzene, 48.2% benzene, 0.1% unidentified impurities. Dinitrobenzene and nitrophenol are absent. From this mixture at a temperature of 36 ^o C and a residual pressure of 15 mm RT.article benzene is distilled off, which is returned to nitration.

 The aqueous phase is washed with benzene (0.36 g per 1 g of the aqueous phase). An extract containing organic matter recovered from spent nitric acid is subsequently used as a starting material for nitration. The washed spent nitric acid (concentration 57%) is strengthened with smoking acid to 65% and is further used as a nitrating agent.

The output of nitrobenzene in one pass of the reagents through the reactor in the first 21.9 hours of nitration was 41%. The hourly productivity of the reactor nozzle for nitrobenzene was 688 kg per 1 ton and 536 kg per 1 m ³ during this period.

Without any effect on the reactor nozzle, the nitration process is continued at a temperature of 82 ^° C., reducing the feed rates of benzene and 70% nitric acid to 8.5 ml / h. After 10 hours of nitration and processing of the products described above, 94.4 g of a mixture of nitrobenzene (67.9%) and benzene (32.1%) are obtained. The yield of nitrobenzene 54%. The productivity of the nozzle for nitrobenzene in 1 h was 633 kg ha 1 t, 493 kg per 1 m ³ .

The nitration is continued at 80 ^° C., feeding the extract (see above) and spent fortified nitric acid obtained in the first section of the nitration cycle to the reactor. After 13.6 hours of nitration, 123.7 g of a mixture of nitrobenzene (56%), benzene (43.9%) and unidentified impurities (0.1%) are present. The yield of nitrobenzene 43% With 1 t of nozzle receive in 1 h 504 kg of nitrobenzene, 1 m ³ 392 kg

Example 6. The working area of a glass reactor is filled (bottom to top) with a glass nozzle used in example 3 (4.11 g, 3.2 ml) and fresh zeolite type ZSM-5 used in example 5 (4.98 g, 9 3 ml). The reactor is calcined at 200-225 ^o C for 1.5 hours with a flow of 17 l / h of air, then cooled to 80 ^o C.

Nitration is carried out at an average nozzle temperature of 84 ^° C. for 10.7 hours, feeding benzene at a rate of 13.8 ml / h and 69.3% nitric acid at a rate of 18.0 ml / h. The molar ratio of HNO ₃ : benzene is 1.8.

 The nitration product is treated analogously to example 3 to obtain 160.5 g of a mixture of organic products containing 72.2% nitrobenzene, 27.7% benzene and 0.1% unidentified impurities. Dinitrobenzene and nitrophenol are absent.

The output of nitrobenzene in one pass of the reagents through the reactor was 54%
The hourly productivity of the reactor nozzle in nitrobenzene was 1183 kg per 1 ton and 864 kg per 1 m ^{3 of} nozzle.

Example 7. Nitration is carried out in a reactor made of X18H10T steel, containing in the working zone 7.5 g (5.4 ml) of a glass nozzle and 4.21 g (8.0 ml) of the ZSM-5 type zeolite used in Example 5. Nozzle went through two cycles of nitration and regeneration. Benzene and 68.6% nitric acid are pumped through the reactor at a temperature of 85 ^° C. for 10 hours. Both reagents are supplied at a rate of 12 ml / h, which corresponds to a molar ratio of HNO ₃ : benzene 1.4.

 The reaction product is treated in the same manner as in Example 5, and 132.94 g of a mixture of nitrobenzene (48.3%) with benzene (51.7%) are obtained.

The yield of nitrobenzene was 39%. The hourly productivity of 1 ton and 1 m ^{3 of} nozzle was 548 and 479 kg, respectively.

The benzene pumping rate is reduced to 8.5 ml / h, as a result of which the ratio of NHO ₃ : benzene increases to 1.9 and nitration is continued for another 9.2 hours.

 The organic part of the nitration product treated in Example 5 is a mixture of nitrobenzene and benzene in a ratio of 62.6: 37.4.

The output of nitrobenzene in one pass of the reagents through the reactor amounted to 50% removal of nitrobenzene from 1 t and 1 m ^{3 of} nozzle 508 kg and 444 kg, respectively.

 The table below shows the conditions and results of nitration achieved in the prototype and examples 3-7 of this invention.

 Thus, the proposed method of nitration of benzene in comparison with the known method allows 2.5-5 times to accelerate the nitration reaction; to increase the productivity of the catalyst by 1.2-3.5 times; 1.1-2.4 times increase the yield of nitrobenzene; to develop a technology for nitration of benzene in a continuous mode with closed cycles on benzene and nitric acid.

 These advantages, combined with the expansion of the range of aluminosilicates used and the possibility of their repeated use, open up the prospect of industrial implementation of a new benzene nitration process.

Sources of information taken into account:
1. M.V. Gorelik, L.S. Efros. Fundamentals of chemistry and technology of aromatic compounds. M. Chemistry, 1992, p. 140.

 2. US patent N 4.021.498.

 3. European patent application N 395556.

 4. PCT Int. Appl. WO 9000,087.

 5. Application of Japan 249755.

 6. US patent 3957889.

 7. US patent 5030776.

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

 9. Japanese Patent 63-225339.

Claims (3)

 1. The method of nitration of benzene with aqueous solutions of nitric acid in the presence of aluminosilicates upon heating, characterized in that it is carried out continuously and glass granular packing and (or) zeolites ZSM-5 and ZSM-11 modified with iron oxides are used as aluminosilicates.  2. The method according to p. 1, characterized in that the nitration on aluminosilicates is carried out with 65-70% nitric acid with a molar ratio of nitric acid to benzene equal to 1.4-4.5.  3. The method according to p. 1, characterized in that the aluminosilicates loaded into the reactor are used repeatedly, and unreacted benzene and nitric acid are returned to nitration.

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