The method of purification of benzene from thiophene

 

(57) Abstract:

The invention relates to the field of production of high-purity benzene, namely, to clean it from thiophene. The content of thiophene in benzene, used in the syntheses of metal-containing catalysts is not more than 0,00005 wt. %. Purification of benzene from thiophene carried out by treatment with methenamine in the amount of from 1.5 to 3.0 mol per 1 mol of benzene in the presence of catalytic amounts of sulfuric acid. The technical result - the reduction of losses of benzene when cleaning from thiophene, reducing reagent consumption per unit of product.

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

Thiophene is an impurity, detrimental in most refining processes, primarily as a catalytic poison.

The most sensitive to the content of thiophene in raw materials, the process of catalytic hydrogenation of benzene. When the content of thiophene in benzene is 0.0002% of the speed of hydrogenation on Nickel-chromium catalysts is reduced by half. No less sensitive to the thiophene and platinum hydrogenation catalysts.

The content of thiophene in benzene, going to gig also forms nitro-derivatives, which reduce the quality of the products of nitrobenzene reduction, reduce stability during storage.

Impurities of thiophene harmful by direct catalytic reduction of nitrobenzene to aniline on copper catalysts, in the chlorination of benzene in the presence of ferric chloride in the alkylation of benzene on the number of catalysts, etc.

Thus, the task of cleaning benzene from thiophene very relevant for the petrochemical industries that use benzene.

Widely used in industry methods of cleaning products from impurities is clear rectification using high-performance columns, azeotropic distillation using different solvents in extractive distillation - do not allow to achieve a deep level of cleaning of benzene from thiophene.

The most effective is a catalytic Hydrotreating under pressure at a temperature of 380 - 500oC, the method provides deep cleaning of benzene from thiophene (up to 0,00005% wt.) [Composition and processing of liquid pyrolysis products in the domestic installations. Thematic review., M, Niitehim, 1977, S. 76 - 77].

However, this cleaning process is very energy intensive, is justified only in large Eskim reasons.

Thiophene from benzene it is impossible to allocate any regular or fractionated crystallization, as it forms benzene mixed crystals [C. M. Kravchenko. Russian journal of applied chemistry, 1950, I. 23, N 3, S. 288 - 298].

The proximity of the adsorption properties of thiophene and benzene do not allow them to be divided into conventional absorbents [S. Y. Elovich, O., Larionov. Russian journal of applied chemistry, 1961, T. 34, N 9, S. 2067 - 2073].

Complete removal of thiophene achieved on the active clays at the process temperature of 150 - 250oC, a pressure of 2.0 - 2,08 ATA [A. D. Berens and other Processing of liquid products of pyrolysis. M, Chemistry, 1985, S. 216]. However, the method is limited to the upper content of thiophene in raw material 3 million-1high consumption of adsorbent per unit of raw materials and the need for disposal of the spent adsorbent.

A known method of purification of benzene from thiophene and uncertain connection, combining in a single process of adsorption and catalytic purification [C. A. Dynin and other Fine purification of benzene fraction of pyrolysis condensate fraction from olefins and thiophene. Refining and petrochemicals, 1988, N 9, p. 19-21]. The method allows of cleaning products containing thiophene 5.5 to 22 million-1followed by distillation to isolate benzene, meets the requirements of GOST 9572-77 on the benzene brand "high clear what method are the loss of benzene due to its partial alkylation, the relatively high cost of the cleanup process.

For deep cleaning of benzene from thiophene, especially when a small content in the purified benzene, widely used methods of chemical binding of thiophene with separation of the formed products of the interaction of benzene. The use of reagents of acid nature (aluminum chloride, ferric chloride, hydrogen fluoride, boron TRIFLUORIDE and other) does not provide the necessary depth cleanup [,Century, Keglevich and other coke and chemistry, 1933, No. 7, S. 55; B. A. Volkov. Coke and chemistry, 1957, No. 1, S. 53]. In addition, these processes are lengthy, multistage, require a large consumption of reagent, careful dehydration of raw materials.

The most widespread in the industry has found a way of purification of benzene from thiophene sulfuric acid [J. A. Pustovit, coke and chemistry, 1960, No. 10, S. 44] . Remove thiophene thus based on the difference of the speeds of sulfonation of benzene and thiophene.

However, practically sulfuric acid cleaning is always accompanied by partial sulfonation of benzene, the higher the degree of purification, the greater the loss of benzene [L. J. of Colander. Obtaining pure benzene for synthesis, M., metallurgy, 1966, S. 111].

Nedostatkama organic impurities in the waste sulfuric acid, the lack of selectivity.

The efficiency and selectivity of the process of purification of benzene from thiophene sulfuric acid is increased in the presence of unsaturated compounds or industrial additives - waste containing [L. M. Cherkasova, L. K. Gorin. Coke and chemistry, 1963, No. 1, S. 44 - 46; A. P. Kolesov and other coke and chemistry, 1965, No. 11, S. 34 - 37]. The products of the interaction of thiophene with the utmost compounds are separated by distillation. The residual content of thiophene in benzene - 0,00005% wt. However, problems persist consumption of sulfuric acid, although lower concentrations (93 - 94%), the need for pre-drying of raw materials, regeneration of waste acids, waste disposal, separation of the purified benzene unsaturated compounds.

Closest to the claimed method according to technical essence is a method of purification of benzene from thiophene with formaldehyde in the presence of sulfuric acid [L. M. Cherkasova, L. K. Gorin. Coke and chemistry, 1963, No. 1, S. 44].

The amount of formaldehyde 0,52% wt. to purify benzene of 92.5 mol per 1 mol of thiophene), the quantity of sulfuric acid with a concentration of 94% by weight. - 10,9% wt. to benzene. The source contains benzene 0,056% wt. thiophene. The cleaning temperature - 80,0oC. 20% to HUF the donkey feeder acid, followed by stirring for 40 minutes.

The resulting mixture of benzene, reagent and powdered products of the condensation of thiophene with formaldehyde defend for 45 minutes. Reagent settled with the condensation products down. The purified benzene does not contain thiophene. The yield of purified benzene and about 96 wt.%. from the original.

Disadvantages of the process is the high consumption of reagent - 114,5 kg per 1 ton of benzene, large losses of benzene when cleaning, the need for reagent not subject to regeneration.

The aim of the invention is the reduction of losses of benzene in the process of cleaning, reducing reagent consumption.

This goal is achieved by the fact that the purification of benzene from thiophene spend urotropine (hexamethylentetramine) in the presence of catalytic amounts of sulfuric acid. The number of urotropine is from 1.5 to 3.0 mol per 1 mol of thiophene in purified benzene. The quantity of sulfuric acid (based on 100%) - 0.1 to 1.0 wt.%. in terms of benzene. Cleaning is performed at a temperature of 20.0 - 80,0oC under vigorous stirring (stirring speed 800 - 1200 rpm./min) for 30 - 60 minutes.

From the products of condensation of thiophene with urotropine (gel formation of a light yellow color which does not exceed 0,00005% wt. (depending on the time of contact of the purified benzene reagent). The purified benzene corresponds to the content of thiophene with the requirements of GOST 9572-77 on the benzene petroleum grade "high purity" and GOST 8448-78 on the benzene coal and shale of the highest category cleanup.

The process is carried out in the apparatus of intensive mixing, as very low concentrations of thiophene and reagent in benzene. The distillation of benzene is carried out in a distillation column efficiency 30 practical plates (so so ), with a reflux ratio (PL. h) is 1.0, the temperature of the top of the column 80,0oC Cuba - 84,5oC.

The yield of benzene 99,50 - 99,60% wt

CBM product distillation columns - formirovanii product with thiophene and ammonium sulfate periodically taken for incineration.

Below are examples of the practical implementation benzene purification by the present method.

Example 1.

In the apparatus intensive mixing load 1000 kg of benzene oil brand "synthesis" of the first class containing the basic substance 99,50%, thiophene - 0,00035% wt. injected cent to 8.85 g of methenamine (0,063 mol) and 6100 g of 98% sulfuric acid (0.6% of wt. relative to benzene). The molar ratio of urotropine:thiophene costaki 1000 rpm./min 30 min Then the reaction mixture from the mixing apparatus serves in a distillation column efficiency 30th Ave so, FL.h. - 1,0, ttop0- 80,0oC, tcube0- 84,5oC.

The purified benzene does not contain thiophene. The yield of benzene 99,55% wt. in the calculation of the original.

CBM product as it accumulates output periodically to burning.

Example 2.

In the apparatus intensive mixing load 1000 kg of benzene coke production brand "synthesis" of the first class containing the basic substance 99,0% wt., thiophene - 0,0004% wt.. enter 20 g of methenamine and 1020 g of 98% sulfuric acid (0.1% wt. based on benzene).

The ratio (molar) methenamine:thiophene is 3:1.

Mixing is carried out at a temperature of 20oC under the conditions of example 1.

After 30 minutes stirring the contents of thiophene in benzene is 0,00005% wt. , after 60 minutes of mixing the purified benzene does not contain thiophene.

Separation of benzene from the products of condensation of thiophene with urotropine is carried out in the conditions of example 1.

The yield of benzene 99,60% wt. to the original.

Example 3.

In the apparatus of example 1 load 1000 kg of benzene esta - 99,70% wt., enter 8.0 g of methenamine and 10200 g of 98% sulfuric acid (1.0% wt. based on benzene).

The ratio of urotropine:thiophene - 2,4:1 (molar).

Temperature under stirring to 50oC.

After 25 minutes of mixing the benzene contains 0,00005% wt. thiophene, after 60 minutes of stirring thiophene in benzene is missing.

Separation of benzene from the products of condensation of thiophene with urotropine lead in the conditions of example 1. The yield of benzene - 99,50% wt

Example 4 (the prototype).

In the autoclave with stirrer load of 1000 g of benzene in example 1, enter of 3.56 g of formalin 28% concentration, stirred for 10 minutes, enter 109 g 94% sulfuric acid, and 15.0 g of 28% aqueous formalin.

The mixing speed is 900 rpm./minutes

The mixture in the autoclave is stirred for 40 minutes at a temperature 80,0oC. After the termination of stirring, the reaction mixture defend for 45 minutes. The bottom layer of the reaction products of the condensation of thiophene with formaldehyde is drained. Benzene content in it to 3.67%, condensation products of formaldehyde with benzene - 0,43% wt

The top product is purified benzene does not contain thiophene.

Thus, the claimed method of purification of the A.

However, loss of benzene in the claimed method are at the level of 0.50% wt. in terms of the initial benzene (about 4.0% by weight. in a known way).

Consumption of urotropine is on the level of consumption of formaldehyde to 1 mol of thiophene and consumption of sulfuric acid is reduced to the order and more (1,0 - 10,0 kg, compared to 102 kg in recalculation on 100% acid 1.0 t benzene). In the reaction mixture did not find products of sulfonation of benzene or products of the reaction of interaction of sulfuric acid with thiophene. Obviously, the role of sulfuric acid in the inventive process consists in the implementation of the interphase transfer in the systems benzene - thiophene, methenamine - thiophene.

When using + the number of < 1.5 mol per 1 mol of thiophene is not achieved complete removal of benzene; more than 3 mol per 1 mol of thiophene, use is impractical because it does not improve the quality of cleaning and the reaction mixture is free methenamine.

When the amount of sulfuric acid is less than 1.0 kg 1.0 tonnes of benzene (in recalculation on 100% acid), the process proceeds more slowly, the time of contact of the reagent with the purified benzene to achieve the necessary depth cleaning from thiophene increased the cleaning process or improving treatment and creates unnecessary load on the system.

Temperature cleaning mode does not affect its quality, increasing some of its intensity with increasing temperature, but not very much.

Used methenamine corresponds to GOST 1381-73. Sulphuric acid technical - GOST 2184-77.

The method of purification of benzene from thiophene processing chemical reagent in the presence of sulfuric acid, followed by separation of the pure product, characterized in that as methenamine reagent is used in an amount of from 1.5 to 3.0 mol per 1 mol of thiophene, and sulfuric acid in a catalytic amount.

 

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FIELD: chemistry of aromatic compounds, organic chemistry, chemical technology.

SUBSTANCE: method involves purification of benzene from thiophene in the presence of diene compounds, water and urotropin by its treatment with sulfuric acid solution at 20-40°C in cascade of mixing units and with fractional (distributed) feeding sulfuric acid solution in mixing units. Method provides simplifying the process and enhanced yield of benzene.

EFFECT: improved method for treatment.

3 cl, 3 tbl, 6 dwg, 7 ex

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