IMPROVEMENT OF THE TECHNOLOGY OF OBTAINING ACETONE AND ACETYL VINYL ACETATE BY CATALYTIC HYDRATION OF ACETYLENE

ABSTRACT

Acetone and vinyl acetate take the leading place among the oxygenated compounds produced in the world today in petrochemical and basic organic synthesis industries. Today, the annual need for acetone in the world is 2 million tons, the annual need for vinyl acetate is 10 million tons, and in our Republic, the need for acetone is 10-15 thousand tons, and the need for vinyl acetate is 40-50 thousand tons. is enough. The influence of various factors (temperature, volume velocity, acetylene: water ratio, acetylene: acetic acid ratio, catalyst content, etc.) on the product yield and process selectivity in the catalytic hydration and acetylation reaction of acetylene was studied. An improved and low-waste, energy- and resource-saving technology for obtaining acetone and acetylated vinyl acetate by catalytic hydration of acetylene has been developed.

АННОТАЦИЯ

Ацетон и винилацетат занимают ведущее место среди кислородсодержащих соединений, производимых сегодня в мире в нефтехимической промышленности и органическом синтезе. Сегодня годовая потребность в ацетоне в мире составляет 2 миллиона тонн, годовая потребность в винилацетате - 10 миллионов тонн, а в нашей Республике потребность в ацетоне - 10-15 тысяч тонн, а потребность в винилацетате - 40 тысяч тонн. -50 тыс. т. достаточно. Изучено влияние различных факторов (температуры, объемной скорости, соотношения ацетилен: вода, соотношение ацетилен: уксусная кислота, содержание катализатора и др.) на выход продукта и селективность процесса в реакциях каталитической гидратации и ацетилирования ацетилена. Разработана усовершенствованная, малоотходная, энерго- и ресурсосберегающая технология получения ацетона и ацетилированного винилацетата каталитической гидратацией ацетилена.

Keywords: acetylene, water, acetone, catalyst, "wet" and suspension technology, keramzite, bentonite.

Ключевые слова: ацетилен, вода, ацетон, катализатор, «мокрая» и суспензионная технология, керамзит, бентонит.

INTRODUCTION

Acetone and vinyl acetate take the leading place among the oxygenated compounds produced in the world today in petrochemical and basic organic synthesis industries [1-2].

Acetone is a volatile liquid with a specific smell. An expensive industrial solvent. Due to its low toxicity, it is widely used in the production of varnishes, explosives and medicines. It is the starting compound in many chemical syntheses. In laboratory practice, acetone is used as a polar aprotic solvent for the preparation of cooling mixtures with dry ice and ammonia, as well as for washing chemical glassware.

Vinyl acetate is the most important monomer in the plastics industry. Polyvinyl acetate is a polymer with high adhesive properties, which is widely used in the production of adhesives, water-soluble latex paints. At the same time, polyvinyl acetate, polyvinyl alcohol is important in medicine, agriculture, in the creation of synthetic rubber, synthetic fibers, biologically active substances and other materials with unique properties [3-5].

Today, the annual need for acetone in the world is 2 million tons, the annual need for vinyl acetate is 10 million tons, and in our Republic, the need for acetone is 10-15 thousand tons, and the need for vinyl acetate is 40-50 thousand tons. is enough. Therefore, it is urgent to carry out scientific research work on the development and improvement of the technology of obtaining acetone and vinyl acetate with the participation of local catalysts [6-8].

EXPERIMENTAL PART

The effect of various factors (temperature, volume velocity, acetylene:water ratio, catalyst composition, etc.) on the product yield and process selectivity in the catalytic hydration reaction of acetylene was studied. Table 1 shows the effect of catalyst active components of the reaction products [9-10].

Table 1.

The effect of starting materials on catalyst activity in the catalytic hydration reaction of acetylene

Based on the above, we selected a catalyst with high activity, selectivity and productivity, high selectivity, and thermal stability based on local raw materials.

The catalytic activity of catalysts prepared from salts of d-elements in the catalytic acetylation reaction of acetylene in the vapor phase was studied.

Table 2.

Effect of starting materials on catalyst activity in the catalytic acetylation reaction of acetylene

As can be seen from the data presented in the table, the activity of ZnO:CdO:ZrO₂/keramzite is much higher.

RESULTS AND DISCUSSION

(99.8%) Acetylene (1) is delivered from the tank (2) to the upper part of the reactor (hydrolysis unit) for hydration through the compressed acetylene pipeline under a pressure of 0.18 MPa through the compressor. For the safe transportation of compressed acetylene, steam is supplied to the acetylene pipeline, and it is heated to a temperature of 270°C in a heating furnace. To prevent local overheating of the steam acetylene mixture at the point where the transport steam is introduced, the acetylene pipeline is equipped with a shutter for cooling the mixture with circulating water.

The superheater (3) is a rectangular chambered firebox with a stack of steel tubes inside. When the temperature exceeds 350-400°C, catalyst dust starts to come out. Steam heated to 500°C in a heating furnace to reduce catalyst expulsion and (2) acetylene from the compressor are mixed in a ratio (1:4) in a mixer (4) installed at the top of the reactor. Reactor (5) is a vertical apparatus, inside which 10 layers of ZnO·Fe₂O₃·Cr₂O₃·MnO₂·V₂O₅/HSZ catalyst are placed and 10 plates are installed above the catalyst layer of each layer.

The process of acetylene hydration is carried out at a temperature of 425-430°C. At the beginning of the reaction period, the temperature is maintained at 425ºC. As the activity of the catalyst decreases, the temperature of the hydration process gradually increases to 435°C.

Contact gases formed as a result of the reaction from the lower part of the reactor (6) are cooled to a temperature of 185°C in a steam boiler.

After the steam boiler, the gases enter the cooler of the refrigerator (7), where they are cooled by circulating water to a temperature of 100°C and sent to the next cooler (8). Here they are cooled again with circulating water to a temperature of 75°C. In this case, the main part of acetone, acetic acid and crotonic acid dissolved in water in the condenser is condensed. Non-condensable gases at a temperature of 75°C enter the aftercooler (9) where they are cooled with cold water to a temperature of 35°C. The obtained acetone water is condensed in coolers (7), (8), (9) and sent to tank (11).

Gas mixture washed from acetone and reaction products, flue gases containing carbon dioxide (CO₂), nitrogen (N₂), oxygen (O₂), methane (CH₄), carbon monoxide (CO) are released into the atmosphere through a chimney (10) 40 meters high.

Figure 1. Technological scheme of obtaining acetone from acetylene and water

1-acetylene; 2, 12th pump; 3-water; 4-evaporator; 5th reactor; 6, 14 and 20-heater; 7, 8 and 9- coolers; 10-gas processing tower; 11th collector; 13, 19-rectification column; 15 and 23-small cooler; 16, 17, 21 and 22 deflegator; Collector 24

Aqueous acetone (up to 3-7% acetone, 0.1% croton aldehyde, 0.01% acetic aldehyde) collected in tank (11) with a temperature of 50-70°C is supplied from the upper part of the rectification column (12) through pump (13). In the lower part of the rectification column (14), the temperature is heated up to 130°C with the help of steam. The temperature in the upper part of the column is 115-120°C. The fusel water (15) from the lower part of the column is cooled to 40-45°C through the cooler and goes to BXO. The main function of this rectification column is to separate acetone from aqueous acetone.

Acetone (16) in a par form from the top of the column is cooled with circulating water through the dephlegmator and fed as phlegm (saturation) from the top of the column. Gases that have not turned into liquid are cooled by cooled water in the next (17) dephlegmator. In dephlegmators (16-17), a part of the cooled acetone is given as phlegm to saturate the column, and the rest is passed through a 40% NaOH solution in (18). The temperature in Mishalka is 56-60°C. Acetaldehyde is resinified under the action of alkali, designed for the process of saponification of esters in acetone with alkali.      

Acetone vapors (19) at 45-50°C purified from acetaldehyde are sent to the lower part of the rectification column. This is heated to a temperature of 80-82°C using a heater in the lower part of the rectification column (20). The temperature at the top of the column is 55-58°C. Acetone vapors in the upper part of the column are cooled and condensed in reflux condensers through a dephlegmator installed in series (21-22). Part of the technical acetone is returned to the top of the column as phlegm. The remaining part (23) is cooled in a cooler and (24) is pressed with nitrogen into the collector.

According to this technology, it is possible to obtain high purity acetone, i.e. not less than 99.5%.

Synthesis of vinyl acetate is carried out in a continuous method in a contact apparatus with a pseudo-boiling catalyst layer. Acetylene (99.9%) is transferred from the generator (6 shop) to the cleaner (15) at a rate of 11.3 m3/h under a pressure of 0.5 kg s/cm2. Purified acetylene comes to the evaporator (16).

Acetic acid (99.5%) is sent to the evaporator (16) from (7 shops). The gas-steam mixture consisting of acetylene and acetic acid obtained in the evaporator is heated to 55-60°C, and acetylene and acetic acid in a ratio of 4:1 go to the reactor (17). The material of the reactor is made of carbon steel (height 15.5 m, diameter 3 m). The contact apparatus is a system of reactor tubes in which the reaction mixture is distributed. When the temperature rises to 180-185°C, catalyst dust starts to come out. Steam-gas mixture is sent from the top of the reactor in order to reduce the driving of the catalyst. The reactor is a tube-shaped device, this tube is filled with a catalyst, and a heat carrier is placed in the spaces between the tubes (to dissipate the reaction heat). The tube is filled with ZnO·CdO·ZrO₂/keramzite nanocatalyst (volume 16 m3, height 2.3 m). The capacity of one unit for vinyl acetate is 22,000 tons per year. In order to return heat, it is possible to use the method of evaporation of aqueous condensate with steam extraction in the space between the tubes, or, if necessary, to evaporate the liquid diphenyl mixture for heat loss. The diphenyl mixture cools the aqueous condensate in the heat exchanger due to evaporation.

The reactor gas leaves the bottom of the reactor and is sent to the water cooler through the heat exchanger. Reaction products (17) leave the reactor (50-55% vinyl acetate, 40-45% acetic acid, 0.2-0.7% acetaldehyde, 0.01-0.03% acetone, 0.2-0.4% croton aldehyde and dissolved acetylene) (18) are sent through the trap to coolers (8-10) connected in series. Refrigerant (8) is water-cooled, (9) is cooled to -15oC with (NaCl) brine, and (10) is cooled to -40°C with brine. Unreacted acetylene is sent to (6).

Figure 2. Technological scheme of production of vinyl acetate from acetylene and acetic acid by vapor phase method

1-container for vinyl acetate; 2.11-rectification column, 3.5-deflegmator; 4,8,10,12,18,19-coolers, 6-acetylene generator; 7-acetic acid; 9-saline solution; 13,20-collector, 14-cleaner; 15-evaporator; 16- reactor; trap 17; 21st capacity

Vinyl acetate condenses in coolers (19-20) and goes to tank (1). Vinyl acetate is sent from the pressure tank (1) to the lower part of the absorption-rectification column (the rectification device consists of 5 columns and 60 plates and is 21.5 m high and 1.8 m in diameter) (2). A heater is placed below the column (3) and it is heated with steam up to 65-70°C. In the upper part of the column, light volatile components are separated at 20-25°C and they are cooled by circulating water through the dephlegmator and given as phlegm (saturation) from the upper part of the column. is collected.

Liquid products are sent from the column (2) to the condensation-rectification column (11). A heater is placed below the column (12) and heated to 80-90°C. In the upper part of the column, the temperature is 70-75°C, where vinylacetate vapors are separated. The rectified product contains vinyl acetate (0.003% acetic acid and 0.06% acetaldehyde). The vinyl acetate vapors at the top of the column are cooled and (13) condensed in reflux condensers through a dephlegmator. A portion of the technical vinyl acetate is returned to the top of the column as phlegm. The rest is condensed in the cooler (14) and collected in the collector (22). Acetic acid comes out from the lower part of the column (11) and it is collected in the container (23) and sent to the collector (section 7) with the help of a pump.

Vinylacetate is purified from unreacted acetic acid and by-products by absorption method (reactor steam-gas mixture condensate can be used as an adsorbent for acetic acid, or xylene is used as an external adsorbent).

According to this technology, it is possible to obtain vinyl acetate with a high purity of not less than 99.9%.

CONCLUSIONS

A new nanocatalyst consisting of ZnO·Fe₂O₃·Cr₂O₃·MnO₂·V₂O₅/HSZ and ZnO·CdO·ZrO₂/keramzite with high efficiency and selectivity was created for the process of hydration of acetylene with water and acetylation with acetic acid. Texture and physico-chemical properties of the nanocatalyst with high catalytic activity created for catalytic hydration and acetylation of acetylene were determined. An improved and low-waste, energy- and resource-saving technology for obtaining acetone and acetylated vinyl acetate by catalytic hydration of acetylene has been developed.

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