RU2174504C1 - Method of purification of benzene from thiophene - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: benzene is purified from thiophene by treatment with sulfuric acid in amount of 0.5-1 wt.% calculated for benzene in the presence of diene hydrocarbons at molar ratio thereof to thiophene of 0.80-1.0, water in amount of 0.002-0.005 wt.% calculated for benzene and catalyst of interphase transfer of alkyl- and aryl-alkyl substituted amines. EFFECT: smaller amount of sulfuric acid, lower losses of benzene during purification and smaller amount of waste. 2 cl, 1 tbl

Description

 The invention relates to the petrochemical industry, to the production of high-purity benzene used in petrochemical synthesis.

 The organic synthesis industry places high demands on the quality of benzene, especially in terms of thiophene content, since thiophene is a catalytic poison in most benzene processing processes, for example, in nitration and catalytic hydrogenation processes.

 The thiophene content in coke-chemical benzene used in syntheses on polymetallic catalysts containing platinum, palladium, nickel should not exceed 0.00005 wt.%.

 The most effective industrial method for the purification of benzene from thiophene is the catalytic hydrotreatment method.

The method includes processing the raw materials with hydrogen (hydrogen-containing gas) in the presence of polymetallic catalysts at a temperature of 350-480 ^o C, pressure 3-5 ata (at the stage of purification from thiophene) [Composition and processing of liquid pyrolysis products in domestic plants. Thematic review. M., TsNIITEkhim, 1977, p. 76-77].

 This is one of the widely used industrial methods for the purification of benzene of coke-chemical and petroleum origin.

 The content of thiophene after hydrotreating meets the requirements for benzene of the highest grades.

 However, the method due to its technological complexity, large capital costs for its organization and high energy intensity can only be used in large industrial production of benzene, it is unprofitable for installations of small and medium capacity.

 The proximity of the adsorption properties of benzene and thiophene do not allow them to be divided into conventional adsorbers [S.Yu. Elovich, O.G. Larionov, ZhPKh, 1961, v. 34, No. 9, p. 2067-2073].

A known method of purification of benzene from thiophene using natural adsorbents (active clays) at a temperature of 150-250 ^o C, a pressure of 2-2.8 atm, followed by the isolation of benzene by distillation [A.D. Berenz et al. Processing of liquid pyrolysis products. M .: Chemistry, 1985, p. 216].

 However, the method is applicable for the purification of benzene with a low thiophene content, in addition, the method requires a high consumption of adsorbents, solving the problem of their disposal.

 Known methods for the purification of benzene from thiophene by treatment with chemical reagents — aluminum chloride, chlorine, formaldehyde, hypochlorite with the formation of condensation products of thiophene with a reagent, but they are associated with a high consumption of reagents, losses of the target product, and waste disposal problems [L. I. Kolyandr. Getting pure benzene. M .: Metallurgy, 1966, p. 64-69].

 The method of purifying benzene from thiophene by treatment with urotropine in the presence of catalytic amounts of sulfuric acid is devoid of the above disadvantages, but it can be used only with a low initial thiophene content in benzene not exceeding 0.0005 wt.%. [Application N 99117305/04 of 08/10/99, the decision to grant a patent of the Russian Federation of 03/29/2000].

 In industry, in the absence of catalytic hydrotreating, a method for cleaning benzene from thiophene with sulfuric acid is widely used (Yu.A. Pustovit. Coke and Chemistry. 1960, N10, p. 44]. The removal of thiophene is based on the difference in benzene sulfonation rates and thiophene. The method requires the use of highly concentrated sulfuric acid (8-100%) or oleum, the greater the amount, the higher the degree of purification required; when purified to a thiophene content not exceeding the requirements of GOST 8448-78 for benzene grade "for synthesis ", its consumption amounted to it is 120-150 kg per ton of benzene, the method involves losses of benzene due to its sulfonation, entrainment with an "acid tar", and the higher the degree of purification, the greater the loss, in addition, problems arise in the regeneration of used sulfuric acid.

 The closest in technical essence to the claimed is a method for purifying benzene from thiophene by treating it with sulfuric acid in the presence of unsaturated hydrocarbons [L.Ya. Kolyandr. Obtaining pure benzene for synthesis. M .: Metallurgy, 1966, p. 79-80]. Use 93-94% sulfuric acid in an amount of 10.0-11.3 wt.% Calculated on the purified benzene.

As unsaturated hydrocarbons, a mixture of olefin and diene hydrocarbons contained in the pyrolysis resin fraction having a boiling point of 82-86 ^° C, a temperature at 95% distillation of 142-156 ^° C, an end of boiling of 180-186 ^° C, namely a styrene mixture, is used. , cyclohexene, dicyclopentadiene, vinyl toluene, indene, methylcyclohexene, methylhexanedienes and dimethylhexenes.

 As a starting material, benzene coke chemical grade “for nitration” is used, containing 0.045-0.060 wt.% Thiophene.

 The consumption of a pyrolysis resin containing 7.5-8.5% (volumetric) unsaturated hydrocarbons is 8.2-9.0 wt.%.

 The mass ratio of unsaturated hydrocarbons to thiophene is 8.7-12.0: 1.0.

 The cleaning time is 5-20 minutes at ordinary temperature.

 In purified benzene, the thiophene content is 0.00046 wt.% After 5 minutes of purification; after purification for 20 minutes, the absence of thiophene in benzene is achieved.

 After rectification, benzene is obtained that fully complies with the requirements of GOST 8448-78 for benzene of the "highest purification category" grade.

 The method is based on the ability of the chemical interaction of thiophene and unsaturated hydrocarbons with the formation of alkyl derivatives of thiophene and its copolymers with unsaturated hydrocarbons.

 Since the rate of the alkylation reaction is ten times higher than the rate of copolymerization, 90% of thiophene forms alkylthiophenes and only about 10% are copolymers.

 The introduction of an additional amount of unsaturated hydrocarbons in the composition of the pyrolysis resin is necessary, since the starting benzene contains them in an amount insufficient to bind thiophene.

 The disadvantages of the method are the high consumption of concentrated sulfuric acid (100-113 kg / t of benzene), the high content of unsaturated hydrocarbons in the reaction mixture, this inevitably entails loss of benzene due to its sulfonation, entrainment with the resulting "acid tar", deterioration of the quality of benzene due to clogging its impurities in the introduction of unsaturated hydrocarbons, the need for the regeneration of large quantities of sulfuric acid, the need for waste disposal ("acid tar").

 The aim of the invention is to reduce the consumption of sulfuric acid, reduce losses of benzene during purification from thiophene, reduce the amount of waste.

 This goal is achieved by the fact that the purification of benzene from thiophene is carried out by treating it with sulfuric acid in the presence of diene hydrocarbons at a water concentration in benzene of 0.002-0.005 wt.% And with the introduction of an interphase transfer catalyst - alkyl or dialkylaryl substituted amines.

 For cleaning use technical sulfuric acid (oleum) (GOST 2184-77) containing 104.16% sulfuric acid.

 As diene hydrocarbons, isoprene, cyclohexadiene, piperylene, isolated from light fractions associated with the coke-chemical or petrochemical production of benzene are used. The molar ratio of diene hydrocarbons to thiophene is 1.0-1.1: 1.0.

 For cleaning use benzene coke chemical brand "for nitration" (GOST 8448-78).

As catalysts for interfacial transfer - alkyl-, dialkylaryl-substituted amines, N, N-benzyldialkylamines are used, where C ₁ -C ₁₂ alkyl, N, N-tetramethylmethylenebisamine (bisamine), hexamethylenetetraamine (urotropin) are used. The amount of catalyst leaves 0.0001-0.001 wt.% Calculated on benzene.

The treatment is carried out with vigorous stirring at a temperature of 6.0-15.0 ^o C for 1-10 minutes.

 Refined benzene does not contain thiophene or its content does not exceed 0.00005 wt.%, Which meets the requirements for benzene coke brand "highest quality category" (GOST 8448-78).

 The high efficiency of cleaning benzene from thiophene according to the claimed method when using significantly lower amounts of sulfuric acid and introduced unsaturated hydrocarbons than in the known methods is obviously explained by an increase in the strength of the acid in a non-polar medium due to a change in its degree of protonation when the water content in the reaction mixture in the range of 0.002-0.005 wt. % and the effect of phase transfer catalysts (substituted amines) on diffusion factors.

 Since the reaction medium during the cleaning process is heterogeneous, and during the cleaning process the reacting substances are transferred to the phase interaction surface by molecular and turbulent diffusion, all chemical reactions occur at the phase boundary, and the use of the above catalysts facilitates the supply of reactants to this surface and the removal of her reaction products, which is especially necessary at low concentrations of reagents, as in the present method.

 The process is carried out in an apparatus with a stirrer. Mixing speed 800-1000 rpm.

 Isolation of benzene is carried out by draining the products of condensation of thiophene and polymerization of diene hydrocarbons after settling the reaction mixture and washing benzene with water. In this case, one water wash is sufficient with a volume ratio of water / benzene equal to 1-1.2: 1. The condensation products of thiophene with unsaturated hydrocarbons, polymers of unsaturated hydrocarbons are sent to combustion or regeneration at a low thiophene content in the starting benzene (up to 0.01% by weight). The yield of benzene is 99.20-99.60 wt.% From the original.

 The following are examples of the practical purification of benzene from thiophene according to the claimed and known methods.

 Example 1

 In the apparatus with a paddle-type mixer, 1000 kg of “nitration” grade benzene (GOST 8448-78) containing 0.04 wt.% Thiophene are loaded. The content of the main substance in benzene is 99.88 wt.%. With stirring, add 50 g of water (0.005 wt.% Calculated on benzene), 12.95 kg (6.85 l) of industrial sulfuric acid containing 104.16 wt. % sulfuric acid (GOST 2181-77), 324.0 g (472.0 ml) of piperylene and 10.0 g of N, N-benzyldimethylamine.

 The amount of sulfuric acid introduced corresponds to 1.1 wt.% Calculated on its 100% concentration.

The molar ratio of piperylene to thiophene is 1.0: 1.0; the amount of N, N-benzyldimethylamine introduced as a phase transfer catalyst is 0.001 wt. % calculated on the purified benzene. The purification is carried out with stirring at a speed of 1000 rpm. for 10 minutes at a temperature of 15 ^o C.

 After sludge, the "acid tar" is drained (the condensation products of thiophene with piperylene, piperylene polymers), the amount of which is 1.15 wt.% Calculated on benzene, and put out for burning.

 The upper product is washed with water at a volume ratio of 1.2: 1.0 to benzene; after sludge, the water is drained.

 Refined benzene contains 0.00005 wt.% Thiophene and meets the requirements of GOST 8448-78 for benzene of the "highest quality category".

 The yield of benzene is 99.20 wt.%, The content of the main substance in it is 99.92 wt.%.

 Example 2

 In the apparatus of example 1 load 1000 kg of benzene brand "for nitration" containing 0.005 wt.% Thiophene, the main substance is 99.90 wt.%. With stirring, add 20 g of water (0.002 wt.% Calculated on benzene), 5.90 kg (3.10 l) of oleum containing 104.16 wt.% Sulfuric acid, 44.50 g of isoprene, 1.0 g of hexamethylenetetraamine (urotropin).

 The amount of sulfuric acid corresponds to 0.50 wt.% Calculated on its 100% concentration.

 The molar ratio of isoprene to thiophene is 1.1: 1.0.

 The amount of urotropine introduced as a phase transfer catalyst is 0.0001 wt.% Calculated on benzene.

Cleaning is carried out for 1 minute with stirring at a speed of 900 rpm./min, at a temperature of 6.0 ^o C.

 Refined benzene does not contain thiophene.

 The yield of benzene is 99.50 wt.%.

 The content of the main substance in the purified product is 99.90 wt.%.

 The amount of bottoms after treatment with reagents is 0.55 wt. % per benzene, bottoms are sent to the storage tank, then to the regeneration of sulfuric acid.

 Example 3

 In the apparatus of example 1 load 1000 kg of benzene brand "for nitration" containing 0.01 wt.% Thiophene, 99.94 wt.% The main substance.

With stirring, 40 g of water (0.004 wt.% Calculated on benzene), 9.42 kg (4.98 l) of industrial sulfuric acid containing 104.16 wt. % H ₂ SO ₄ , 76.20 g cyclohexadiene, 5.0 g N, N-tetra-methyl-methylene-bisamine (bisamine).

 The amount of sulfuric acid in terms of 100% concentration is 0.80 wt.% Calculated on benzene.

 The molar ratio of cyclohexadiene to thiophene is 0.80: 1.0.

The purification is carried out at 12 ^° C. for 8 minutes at a stirring speed of 800 rpm.

 Refined benzene does not contain thiophene.

 The yield of benzene is 99.60 wt.%.

 The content of the main substance in the purified product is 99.95 wt.%. The yield of bottoms ("acid tar") is 0.82 wt.% Calculated on benzene.

 Example 4

 In the apparatus of example 1 load 1000 kg of benzene brand "for nitration" containing 0.02 wt.% Thiophene, 99.88 wt.% The main substance. With stirring, 30 g of water (0.003 wt.% Calculated on benzene), 11.77 kg (6.23 l) of industrial sulfuric acid (GOST 2184-77) containing 104.16% sulfuric acid, 155.80 are introduced into benzene g of a mixture of isoprene, piperylene and cyclohexadiene (in molar amounts, respectively, of 0.64, 0.64 and 0.86 mol), 10 g of N, N-benzyldiethylamine.

 The amount of sulfuric acid in terms of 100% concentration is 1.0 wt.% To benzene. The molar ratio of the mixture of diene hydrocarbons to thiophene is 0.9: 1.0.

 The amount of phase transfer catalyst - N, N-benzyldiethylamine is 0.001 wt.%.

The purification is carried out with stirring at a speed of 1000 rpm. at a temperature of 15 ^o C for 10 minutes.

 Purified benzene contains 0.00005 wt.% Thiophene.

 The benzene yield is 99.20 wt.%, The content of the basic substance is 99.90 wt.%. The yield of bottoms after purification ("acid tar") is 1.02 wt.% Calculated on benzene.

 Examples 5, 6, 7, 8, 9, 10.

In the apparatus of example 1, load 1000 kg of benzene in example 3, containing 0.01 wt.% Thiophene and 99.94 wt.% Of the main substance. The purification is carried out under the conditions of example 3, introducing into benzene as a phase transfer catalyst:
N, N-benzyldiisopropylamine according to example 5;
a mixture of N, N-benzyldibutylamine and N, N-benzyldiisoamylamine in a mass ratio of 1.0: 1.0 - according to example 6;
a mixture of N, N-benzyldiheptylamine and N, N-benzyldipropylamine in a ratio of 1.0: 1.0 (wt.) - according to example 7;
N, N-benzyl didecylamine according to Example 8;
a mixture of N, N-benzyldiundecylamine and N, N-benzyldihexylamine in a mass ratio of 1.0: 1.0 according to Example 9;
N, N-benzyldidodecylamine - as in Example 10.

 The results of benzene purification are presented in the table.

 Example 11 (prototype).

 In the apparatus of example 1 load 1000 kg of benzene in example 3.

With stirring, 110 kg of 94% sulfuric acid, 12 kg of a pyrolysis resin fraction having a boiling point of 82-82.5 ^° C, a temperature at 95% distillation of 153-154 ^° C, and a boiling point of 185 ^° C are introduced into benzene.

 The content of unsaturated hydrocarbons (a mixture of styrene, dicyclopentadiene, vinyl toluene, indene, methylcyclohexene, methylcyclohexadiene, dimethylhexenes and cyclohexene) in the taken fraction of the pyrolysis resin is 8.25 wt. % The mass ratio of unsaturated hydrocarbons to thiophene is 9.96: 1.0.

 The amount of sulfuric acid is 10.35 wt.% Calculated on its 100% concentration.

 The amount of unsaturated hydrocarbons introduced is ≈0.10 wt.% Calculated on benzene.

The purification is carried out with stirring at a speed of 1000 rpm. at a temperature of 20 ^o C for 20 minutes.

 At the end of the purification, the reaction mixture is defended, the "acid resin" is drained, the amount of which is 4.3 wt.% Per benzene, the benzene is washed with a 5% NaOH solution, then with water at a volume ratio of washing reagent to benzene of 1.2: 1 , 0.

 Refined benzene does not contain thiophene and meets the requirements of GOST 8448-78 for benzene grade "highest quality category".

 The benzene yield is 97.8 wt.%, The content of the basic substance is 99.92 wt.%.

 Analysis of the cleaning results of benzene from thiophene according to the claimed and known methods shows that the same cleaning result is achieved in the claimed method with significantly lower amounts of sulfuric acid (0.50-1.0 wt.% Based on benzene compared to 9.4-10 , 6 wt.% - in a known manner) based on its 100% concentration.

 When cleaning benzene according to the claimed method, its losses are reduced to 0.40-0.80 wt.% Compared with 2.2% in the known method.

 The amount of waste after treatment with benzene reagent (the amount of "acid tar") is reduced to 0.50-1.10 wt.% (4.3 wt.% In the known method) based on benzene.

 The method requires a single-stage water washing of the benzene processed during purification, while benzene after purification according to the known method requires washing with a 5% NaOH solution, then with water, that is, it requires additional alkali costs, which is associated with the appearance of additional waste.

 After purification by the present method, foreign impurities do not appear in benzene, the content of the basic substance in it does not decrease compared to the starting benzene, in contrast to benzene purified by the known method.

 Thus, the inventive method allows to reduce the consumption of sulfuric acid, the amount of waste, to improve the quality of purified benzene, to reduce the loss of benzene during cleaning.

 The method is most effective if the water concentration in the purified benzene is 0.002-0.005%, the cleaning efficiency decreases sharply if the benzene is deeply dried or the amount of dissolved water is more than 0.005 wt.%.

The cleaning process according to the claimed method is most effective at temperatures of 6-15 ^o C. At a temperature below 6 ^o C, benzene passes into the solid phase, and at a temperature above 15 ^o C selectivity decreases, the efficiency of the process. Obviously, this is due to the increasing role of autopolymerization of diene.

 It is practically determined that the method is effective with a limited contact time of the catalyst and promoters with benzene. When the contact time is less than 1 minute, the required degree of purification of benzene from thiophene is not achieved, and with a longer contact time (more than 10 minutes) the selectivity decreases, sulfonation of the target product is observed.

 When the content of the phase transfer catalyst is less than 0.0001 wt.% Based on benzene, the cleaning speed slows down, its quality decreases, the amount of catalyst more than 0.001 wt.% Is impractical to use, since this does not improve the quality of purification.

 In the inventive method, diene hydrocarbons are used - isoprene, cyclohexadiene, piperylene, isolated from light fractions associated with coke or petrochemical production.

Used cyclohexadiene has a boiling point of 80.5 ^o C, contains 90-92 wt. % of the main substance, the rest is paraffinic C ₆ -hydrocarbons. Isoprene meets the requirements of TU 38.103659-88 with rev. 1, 2, 3, piperylene - TU 38.103300-83 as amended. 1, 2, 3.

 Practice shows that the use of precisely these diene hydrocarbons allows the purification of benzene from thiophene with a minimum amount of sulfuric acid. The use of olefinic hydrocarbons, styrene, indene, as well as other diene hydrocarbons (cyclopentadiene, methylcyclohexadiene, cycloheptadiene and its methyl derivatives) requires a significantly larger amount thereof with respect to thiophene and a several-fold increase in the concentration of sulfuric acid relative to benzene.

 Technical sulfuric acid complies with GOST 2184-77.

Used as catalysts for the phase transfer of N, N-benzyldialkylamines (C ₁ -C ₁₂ alkyl), benzylamine is alkylated with the corresponding alcohols at a temperature of 170-200 ^o C in the presence of H ₂ SO ₄ followed by distillation of by-products [N. N. Lebedev. Chemistry and technology of basic organic and petrochemical synthesis. M .: Chemistry, 1971, p. 380].

N, N-benzyldialkylamines are oily liquids whose viscosity increases with an increase in the alkyl radical from C ₁ to C ₁₂ .

N, N-tetramethylene bisamine (bisamine) is obtained by passing gaseous dimethylamine through formalin at ordinary temperature, followed by distillation of the fraction 82-83 ^o C. A product is obtained containing 98% of the basic substance, with a density of 0.747 g / cm ³ , with a boiling point of 82.5 -83.0 ^o C [Obtaining paraminophenol and its derivatives. Technical regulations. Sterlitamak, ZAO "SNKhZ", shop N-13, N-14, approved. Technical Director 09/23/96 Section 3.3.5, p. fifteen].

 The urotropin used as a phase transfer catalyst corresponds to GOST 1381-73.

Claims (2)

 1. The method of purification of benzene from thiophene by treatment with sulfuric acid in the presence of unsaturated hydrocarbons, characterized in that the purification is carried out in the presence of 0.002-0.005 wt.% Water, at a concentration of sulfuric acid 0.05-1.10 wt. % calculated on benzene and a molar ratio of unsaturated hydrocarbons to thiophene equal to 0.80-1.10: 1.00, with the introduction of a phase transfer catalyst. 2. The method according to p. 1, characterized in that as the catalyst for phase transfer using N, N-benzyldialkylamines, where alkyl is C ₁ -C ₁₂ ; N, N-tetramethyl-methylenebisamine, hexamethylenetetraamine, and as unsaturated hydrocarbons - isoprene, piperylene, cyclohexadiene.

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