A method of obtaining a crude aromatic polycarboxylic acid
(57) Abstract:Proposed method-flow positive displacement aliphatic carboxylic acids with the number of carbon atoms from one to five of filter cakes aromatic polycarboxylic acid containing an aliphatic carboxylic acid, in which the uterine fluid, aromatic held in bicarbonate acid has a concentration of aliphatic carboxylic acids 5000 hours per million by weight or less, based on the weight of the present aromatic polycarboxylic acid. This method is suitable for the production of crude terephthalic acid, which after purification is used to produce polyesters used in the manufacture of fabrics, fibers and plastic bottles. 4 C.p. f-crystals, 5 PL. The invention relates to obtain a crude terephthalic acid by filtering and countercurrent washing with water to obtain an aqueous slurry suitable for further processing with the aim of obtaining purified terephthalic acid, where the concentration of acetic acid held in the washed filter cake is or is by weight less than 5000 hours on 1 million (ppmw). The aqueous slurry obtained takatof invention relates to obtaining an aqueous slurry of crude terephthalic acid, suitable for carrying out the recovery process in the presence of a metal catalyst of group VIII.In the event of another aspect of the present invention relates to a receiving water slurry of crude terephthalic acid suitable for carrying out the hydrogenation of crude terephthalic acid, where the crude terephthalic acid obtained by oxidation of p-xylene in the solvent comprising acetic acid, and acetic acid displace water by the method of positive displacement washing with water under pressure under conditions of countercurrent flooding.In the case of this method eliminates the need for a drying process used for removal of acetic acid by evaporating it from the crude terephthalic acid. This method of washing with water under pressure under conditions of countercurrent flooding crude terephthalic acid also allows you to lower the amount of wash water to reduce the content of residual impurities in the crude terephthalic acid, recycling and removing acetic acid and/or reduce the load below the equipment for processing of wastewater.In the event of another aspect of the invention field of technology to which it relates, cases is obtained by the oxidation of alkyl aromatics, such as p-KSIL, m-xylene, diisopropylbenzene, diethylbenzene and 2,6-dimethylnaphthalene, in the presence of aliphatic carboxylic acids with the number of carbon atoms from one to five, with an aliphatic carboxylic acid with the number of carbon atoms from one to five displaced water by countercurrent method than reduced content of impurities in the aqueous slurry of the crude polycarboxylic acid in the presence of a metal catalyst of group VIII and hydrogen, and aliphatic carboxylic acid with the number of carbon atoms from one to five can be extracted for the purpose of recycling upstream. The scope of the invention, relates to a method of obtaining crude terephthalic acid suitable for the recovery with the aim of obtaining purified terephthalic acid, which is achieved by carrying out the hydrogenation in aqueous medium in the presence of a metal catalyst of group VIII and hydrogen.Typically terephthalic acid is obtained by liquid-phase oxidation of p-xylene and/or p-Truelove acid in a solvent comprising an aliphatic carboxylic acid, such as acetic acid. Terephthalic acid is of great industrial importance and are widely used in the treatment of polyesters of terephthalic acid, in particular poly (ethylene terephthalate), includes a direct condensation of terephthalic acid with the corresponding polyhydric alcohol. For example, terephthalic acid is subjected to interaction with ethylene glycol, which is accompanied by the formation of bis ( -hydroxyethyl)terephthalate, kotori then undergoes the second stage polymerization. This method of direct condensation is simpler than other known methods, such as transesterification of dimethyl terephthalate with proper gilgulim.However, during the direct esterification may be desirable to use a high-purity terephthalic acid. To become suitable for receiving fibers from polyesters, terephthalic acid should be substantially free of any impurities that lower the melting temperature of the complex of the polyester and/or cause the coloring complex of the polyester. In fact, some impurities contained in the crude terephthalic acid are color-forming precursors. In addition, some impurities act as substances, breaking the circuit upon receipt of polyesters.All these impurities have not yet been identified, however, 4-carboxybenzene, what about the find in the crude terephthalic acid. It is known that the degree of the coloring complex of the polyester is below, if a low content of 4-carboxybenzene from terephthalic acid. Although pure 4-carboxybenzene and can contribute to staining during polymerization, this mixture is a convenient label when assessing the degree of purification of terephthalic acid. The process, which may decrease the content of 4-carboxybenzene from terephthalic acid, characterized by the ability to reduce the content of the dye precursors.From U.S. patent N 3584039 issued to Delbert, Meyer (Delbert H. Meyer) and incorporated herein by reference, it is known that the terephthalic acid of a purity suitable for receiving the fibers, can be prepared by purification of crude terephthalic acid with the use of the restore operation. The cleaning process involves the treatment of an aqueous solution of crude terephthalic acid with hydrogen in the presence of marked or nenalezena on a substrate of a metal catalyst of group VIII metal and the substrate are in the working conditions insoluble in the solution. In this manner due to the formation of the deleted products reduced military terephthalic acid is then removed by crystallization, filtering before the separation of the crystalline product and drying.As noted above, the oxidation of p-xylona is performed in the presence of aliphatic carboxylic acids, such as acetic acid, which acts as a solvent, however, the aliphatic carboxylic acid must be removed prior to hydrogenation of crude terephthalic acid. Aliphatic carboxylic acid may act as a poison in respect of the hydrogenation catalyst.In addition, methods have been proposed eviction or extraction of acetic acid with water from flowing wastewater oxidation process, for example in U.S. patent N 3839436 says about contacting sludge process, oxidation with water, in which water is introduced into the lower region of the zone of displacement, it provides communication with water flowing sewage oxidation process that occurs in the vertical chamber, which results in the precipitation of the acid obtained through the water column, and removing the aqueous slurry suitable for carrying out catalytic cleaning of the bottom of the column. In another example, European patent application with publication number EPO 321272 A1) described the way of exchange or dispersion medium, with the about acid in a multistage column in the upper part and the introduction of water in its lower portion for the formation of a multi-stage column of the upward flow of water providing the deposition of particles of terephthalic acid inside the multi-stage column, and remove the aqueous aliphatic carboxylic acid from the top of the multi-stage column, and an aqueous slurry of terephthalic acid from the bottom of the multistage column. In one of the examples is said about the content in the aqueous slurry of terephthalic acid 30000 hours 1 million (by weight) of acetic acid.All of these methods inherent drawback, namely, they include a positive displacement method of acetic acid from the slurry of crude terephthalic acid with acetic acid, and is based on the deposition or sedimentation of crude terephthalic acid through the column with water.Another way (international patent application number PCT/JP 89/00529, international publication WO 89/11323) is based on the washing of the crystals of terephthalic acid on a rotary vacuum filter, in which the slurry of terephthalic acid is subjected to filtration with suction, and the slurry and the filtrate is maintained at this pressure, at which temperature and pressure are such that excluded the saturation filtrate fluid and thereby clogging of the filtering part of the filter. When this is filtered with suction; the crystals of terephthalic acid rising from the slurry, forming a filter cake as the rotation of the filtering part, and the slurry and the filtrate is located on the bottom of the filter. The filter cake is subjected in this case, the washing in the washing zienia collection. Wash solution is sprayed on the filter cake, is the refluxing solution in the zone the collection and remove it by suction. Positive pressure applied to the slurry and filtrate are relatively small, while in absolute value in the range of 0.5-5.5 kg/cm2. The temperature is in the range 90-150oC.This method of washing of filter cakes suffers from several problems related to the fact that filtration with suction or vacuum filtration tends to limit the pressure that can be applied in the way to atmospheric pressure. Rinsing spray is characterized by the tendency to the formation of channels in the filter cake with the weakening of penetration of the filter cakes under the influence of wash solution.For this reason, the purpose of the invention is to provide a method of displacement of acetic acid from the slurry of crude terephthalic acid in acetic acid environment, where acetic acid is displaced from the slurry of crude terephthalic acid by way of positive displacement with the use of filtration under pressure slurry of crude terephthalic acid, proeven over, filter cakes followed by the formation of a new slurry of crude terephthalic acid in an aqueous medium suitable for carrying out the recovery process in the presence of a metal catalyst of group VIII. The concentration of acetic acid held in the filter cake is by weight or less than 500 parts per million.The purpose of the invention is to provide a method of displacement of acetic acid from the slurry of crude terephthalic acid in acetic acid environment, where acetic acid is displaced from the slurry of crude terephthalic acid by way of positive displacement with the use of filtering the slurry of crude terephthalic acid, wherein the concentration of acetic acid held by the filter cake weight is equal to or less than 5000 hours on 1 million without the need for the drying process in order to remove acetic acid in the filter cake by evaporation with heat.Another objective of the invention is to provide an improved method of obtaining crude terephthalic acid by oxidizing alkyl aromatic substances in acetic acid medium, where the crude terephthalic acid, Posey less than 5000 hours per million, without the need of supplying heat to remove the withholding of acetic acid from the resulting crude terephthalic acid.In connection with the foregoing features a method of obtaining a crude terephthalic acid with a concentration of held-acetic acid, by weight equal to or less than 5000 hours per million (0.5 percent), in which the crude terephthalic acid is suitable for carrying out the recovery process with the aim of obtaining purified terephthalic acid. Crude terephthalic acid obtained by oxidation of alkyl aromatics in acetic acid medium. Recovery of crude terephthalic acid in order to obtain purified terephthalic acid is carried out in aqueous medium in the presence of a metal catalyst of group VIII and hydrogen. Crude terephthalic acid in acetic acid medium is filtered under pressure by way of positive counter-current displacement with water to displace acetic acid by washing with flooding water under the influence of the pressure gradient lying in the range of about from 0.5 and up to about 65 pounds per square inch (from about 3.5 to 448 kN/m2) relative activities what usnei acid, by weight equal to or less than 5000 hours on 1 million (0.5 percent). The washed filter cake is translated then into a water slurry going to the recovery process.The invention alkyl aromatic substance, such as p-xylene and/or p-tolarova acid, is subjected to oxidation in acetic acid medium with molecular oxygen in the presence of a catalytic system containing bromine and one or more heavy metals such as cobalt, manganese and the like. Although this method is well known in this technical field and used in the industry, the course of the oxidation reaction is accompanied by the appearance of impurities that must be removed or lack the ability to make coloring to terephthalic acid was suitable for production of fibers. The main use of related and unrelated terephthalic acid is reduced and limited to use in the production of high molecular weight polyesters, necessary for the production of fibers and films.From U.S. patent N 3584039 known that terephthalic acid with purity, suitable for receiving the fibers, can be prepared by purification of crude terephthalic acid by the process gorodom in the presence of marked or nenalezena on a substrate of a metal catalyst of group VIII, in which case the metal and the substrate are insoluble in the solution at the operating conditions. When carrying out this process is the restoration of intermediate oxidation products, such as 4-carboxybenzene and other coloring impurities present in the terephthalic acid, and education to be deleted or colorless products. Purified terephthalic acid is then extracted by crystallization and drying.Although the above procedure has various advantages, there are still problems, consisting in the fact that acetic acid used in the oxidation process must be largely removed from terephthalic acid prior to the hydrogenation. Acetic acid may play the role of poison in respect of the hydrogenation catalyst, which leads to reduced service life of the catalyst. Separation of acetic acid from terephthalic acid by centrifugation or filtration and drying may be accompanied by loss of acetic acid, if not only provides a system for retrieval of acetic acid.In the separation and hydrogenation of crude terephthalic acid from acetic acid (European patent application EPO, 321271 A1) one way, which was p the acid environment of the oxidation reaction through the use of multi-column dispersion of crystals of the crude acid in water to obtain water-watt-second terephthalic acid, containing by weight 0,03 including acetic acid, i.e. 30000 hours 1 million by weight. The aqueous slurry can be hydrogencarbon, which is achieved by contacting with hydrogen, resulting in improved solubility of the impurities and removes impurities by dissolving in a solvent. When carrying out the process according to this method, the residual content of acetic acid in the slurry by weight exceeds 5000 hours in a million.Despite the presence of the above described solutions for the separation of crude terephthalic acid from acetic acid, for effective separation of the crystals of crude terephthalic acid from acetic acid and obtain crystals of the crude acid in a form suitable for carrying out the hydrogenation may be necessary to conduct the process of filtration or centrifugation, the need for dewatering devices and the need for storage. Equipment costs can be significant, and each stage may be related hardware problems that cause the pressing need to simplify the process and lower equipment costs.By the way, conforming to the invention, the crude crystals terephthal the development with the formation of filter cakes a height of about 0.5 inch (12.7 mm), preferably a height of about 2-8 inches (50,8-293,2 mm), and the mother liquor recycle in the oxidation reactor. Upon receipt of the filter cakes with a preferred minimum height of approximately 2 inches (50.8 mm) and approximately 8 inches (203.2 mm), the flow of acetic acid slurry containing crystals of crude terephthalic acid, terminate and replace the countercurrent flow of water, making it under the influence of the pressure gradient established relative to the pressure in the system, which is sufficient to fill the tank with water above the level of a finding of filter cakes, and with the rise to such a height, at which is provided by coating the surface of the filter cakes preferably to a height of about 0.25 inches (6.35 mm). Applied positive pressure, specified relative to the pressure in the system may be a minimum positive pressure sufficient to displace acetic acid from filter cakes and water constituting at least about 0.5 pound per square inch (about 3.5 kN/m2). In the case of the method of the positive displacement, it is desirable that the flow of water when the displacement of acetic acid from the filter cakes of prikladyvat the>and up to about 65 psi (448 kN/m2). The system pressure can be atmospheric pressure or a pressure greater than or less than atmospheric pressure. Water washed cake of crude terephthalic acid overload then filter in the slurry tank in which sludge add a further amount of water. The temperature of the system in a typical case is high, being in the range of from about 65,5oC (150oF) and approximately 191oC (375oF). Raw terephtalate acid is then subjected to hydrogenation in the presence of a metal catalyst of group VIII and hydrogen, thus obtaining purified terephthalic acid.It was found that when conducting counter-flow positive displacement acetic acid in the filter cake when using water as the displacing medium in the loop filter can effectively replace acetic acid solvent used at the stage of carrying out the oxidation reaction, on the environment, including water as a main component, ensuring the extraction of the crude acid from a slurry consisting of acetic acid and terephthalic acid. When positive salaty and replacing acetic acid with water.The amount of aqueous acetic acid solvent, which may remain in the filter cake of crude terephthalic acid before carrying out countercurrent rinsing, may, by weight, is from about 8 and about 20%, considering the total weight of the filter cake; in a typical case may be, by weight, in the area from approximately 9 to approximately 12%, of which by weight 90 are acetic acid and the remaining 10 on the water.Because of the size of the crystals of crude terephthalic acid and trends from terephthalic acid found in the filter cake, to keep the acetic acid typical methods of filtering are not suitable for the complete removal of residual acetic acid from the filter cake, whereby there arises the need to include the stages of drying. Although the problem size, and can be overcome by using a filter cloth with the transmission of particles of appropriate size, filtration and washing with water are typically ineffective for the removal of acetic acid, when using a vacuum or when conducting filtration under pressure without the use of the method of washing with a piston flow, the sludge is of the channels in the wafer, and water washing does not capture the entire cake.In the case of the method proposed in the invention, it was found that unexpected efficiency of removal of acetic acid can be achieved by carrying out countercurrent washing with displacement under pressure from filter cakes comprising crude terephthalic acid. The content of acetic acid in the crude terephthalic acid can be weight reduced to 5000 h at 1 million or less. When using incremental stages rinse counterflow displacement under the pressure decreases the amount of water required, which is a consequence of using the technique countercurrent washing.Countercurrent washing is defined as the flushing sequence of cells of the filter containing filter cake, whereby each cell of the filter washed sequentially in the reverse order of the degree of contamination.For example, the addition of water during the process method-flow positive displacement you can lower the levels of acetic acid held by the cake, to the content of acetic acid in 1000 hours on 1 million the Amount of water necessary to obtain the level held acetic who Ipotechniy washing, moreover, the incremental water is recycled than decreases the total quantity of water added. Thus, in the case of using only a single stage of leaching with a positive displacement determined that for lower levels of acetic acid in the cake to the value of 1,000 hours per million (0.1 per cent) is only required 0,567 lb (257 g) water recycled to the stage of oxidation per pound (453,6 g) of the crude terephthalic acid. In the case of countercurrent recycle wash water is substantially lowered, as shown below, the amount of water required to lower levels of acetic acid (US) in dry cake up to the value 1000 hours at 1 million (table. 1)
As shown, the concentration of acetic acid in the filter cake can be reduced by using the minimum amount of water introduced into the process through the use of additional stages positive water displacement. For example, the addition of 0.133 lb (60,3 g) of water to one pound (453,6 g) of the crude terephthalic acid at three stages of washing with counter-flow positive displacement it is possible to reduce the concentration of acetic acid up to 1000 hours in a million. When added two stages of washing with counter-flow positive in a million (5,910-3%). Similarly, with the introduction of the process of 0.133 lb (60,3 g) of water to one pound (453,6 g) of the crude terephthalic acid with a decrease in the number of stages of washing with counter-flow positive displacement three to one concentration of acetic acid remains at the level of 22587 including 1 million (2,2587%); but with the introduction of the process of 0.133 lb (60,3 g) of water to one pound (453,6 g) of the crude terephthalic acid in terms of using more stages of washing with counter-flow positive displacement concentration of acetic acid in the cake is the following:
22587 including 1 million acetic acid after stage 1;
4541 including 1 million acetic acid after 2 stages;
1000 hours on 1 million acetic acid after 3 stages;
242 including 1 million acetic acid after 4 stages;
59 PM 1 million acetic acid after 5 stages.For this reason, the essential point is choosing the appropriate number of stages of washing with counter-flow positive displacement, that provides the opportunity to minimise the total amount of water used for washing preemptive. In accordance with the foregoing, when implementing the method, responsive to the invention, for a positive displacement of uksosn the supply level, average of 5000 (0.5%) or less parts per million in the cake obtained by the filtration, a multistage countercurrent filtration of crude terephthalic acid.Acetic acid slurry containing crystals of the crude terephthalic acid is injected into one or more consecutive filtering cells that are physically located so that there was a formation of filter cakes of the desired thickness upon receipt of the stream of slurry of crude terephthalic acid. The flow of the slurry of crude terephthalic acid is then interrupted and replaced by a flow of water, allowing the water to the required level. The flow of water serves under pressure, producing replacement of acetic acid in the mother liquor retained in the filter cake, under the influence of positive pressure. After passing through the water surface (reservoir) through the filter cake filter cake removed from the filter proper ways and the cycle is repeated. The washed filter cake being removed from the filter, can be converted back into water in the sludge with the formation of an aqueous solution suitable for cleaning by hydrogenation.Acceptable is the height of the pellet of tereta the raised area about 2 inches (50.8 mm) and approximately 8 inches (203.2 mm).It is necessary that the filter cake had a thickness sufficient to provide an aqueous media, i.e., the filter cake should be of such thickness at which the solution containing the dissolved substance may be effectively removed by pressure washing. When the thickness of the pellet is less than approximately 0.5 inch (12.7 mm) may be holding acetic acid filter cake, despite the supply of wash water, which is associated with a channel for wash water through the filter cake. Because of the loss of efficiency in the way pressure washing of filter cakes with water to remove the solution containing the dissolved substance, it is useful to form a filter cake of purified terephthalic acid with a minimum height of about 0.5 inch (12.7 mm). As shown in example 18, the washing efficiency increases with the thickness of the pellet.While it is desirable that the height of liquid above the surface of the pellet was minimal, but at the same time such as to ensure pressure washing. This height should be sufficient to fully cover the surface of the pellet liquid. If the surface of the pellet on which yasneniya uterine fluid from the interior of the pellet. Due to the roughness of the surface of the pellet, it is desirable that the minimum height of the liquid above the surface of the pellet was approximately 1/4 inch (6.35 mm).Equipment needed to implement the desired cycle may include a sequence of filter cells, which occupy the proper position at which there is the possibility of flooding by water filtration cells. Acceptable equipment may include a rotary drum filter with multiple filter cells; this filter is equipped with means for removing the washed filter cakes from the filter cells. In addition, means shall be provided to management, allowing you to enter a thread formed crude terephthalic acid in acetic acid environment, to interrupt the flow order flow of water flooding of the filter cake, to apply pressure to the flow of water necessary to ensure a positive substitution of acetic acid in the mother liquor, held crude terephthalic acid to produce the re-flooding of the filter cake, if there are multiple counter flow required to achieve the minimum concentration of acetic acid in filtroval is acceptable rotary drum filter, which can meet the requirements of the proposed method is working under pressure BHS-FEST (trade mark), firm BHS-WERK, Sonthofen, D-8972, Sonthofen, West Germany, although can be used and other filters to implement the desired process cycle. In addition, there may be used a belt filter, of the type manufactured by the firm "Pannevis", Utrecht, the Netherlands.In the case of filter BHS-FEST (TM) rotating the drum contains a series of filter cells located on the periphery of the rotating drum. When spin on filter cells comes acetic acid slurry of crude terephthalic acid and the filter cake built up to the desired height. When the spin cycle continues interrupt raw stream and replacing it with a stream of water flowing under pressure to flooding of the filter cakes on the desired depth. Upon further rotation of the drum, the pressure applied to the water, forcing the water to pass through the filter cake, resulting in the displacement of acetic acid held crude terephthalic acid. Upon further rotation of the drum washing is repeated on the pellet, then the filter cake discharged from the drum, the feeding pressure of the inert gas.Unloaded pellet, containing by weight up to 5000 hours per million (0.5%) or less of acetic acid in the crude terephthalic acid is converted into an aqueous slurry, forming a solution in which the crude terephthalic acid is subjected to hydrogenation in the presence of hydrogen and a metal catalyst of group VIII, as it follows from the U.S. patent N 3584039 included here with reference to illustrate the possibility of obtaining purified terephthalic acid from the crude terephthalic acid containing by weight of 5000 hours per million (0.5%) or less of acetic acid.Although in the above description, the method according to the invention and refers to the multistage counter-flow positive displacement acetic acid from the mother liquor, in relation to the receipt of an aqueous solution of crude terephthalic acid, the proposed method can be extended to the displacement of any of the aliphatic monocarboxylic acids with carbon atoms of 1 to 5 out of the sludge formed by the crude polycarboxylic acid where the above-mentioned crude polycarboxylic acid was obtained by the oxidation of alkyl aromatic compounds. acid and 2,6-natalijagolosova acid.The following examples illustrate the way that meets the invention, but they are not intended to limit the scope of the present invention.Example 1. The example illustrates a single-stage pressure washing water directed to the removal of acetic acid from the sludge formed by the crude terephthalic acid.Laboratory filtration experiments were performed using a cylindrical glass funnel 350 ml, which was done under vacuum. At the bottom of the funnel was placed 80-micron coarse sintered disk. The diameter of the funnel was 3.25 inch. The crude terephthalic acid used with an average particle size of 145 microns.The slurry of crude terephthalic acid and solvent consisting by weight to 90% glacial acetic acid and 10% water was applied to the funnel, then put the vacuum value 560 mm RT.article and the liquid was allowed to drain. The slurry was added continuously, resulting in a free liquid level was maintained above the pellet formed in the funnel. After the cake to the desired height and removal of free liquid from the surface of the pellet vacuum was applied additionally for 20 s, and then the pumping was stopped. To eliminate the possibility is whether in the funnel, forming over the surface of the layer of free fluid. The filter paper was removed and re-applied vacuum. The wash liquid was applied continuously to keep the free layer of liquid over the cake. After the final disappearance of the wash liquid from the surface of the pellet vacuum was maintained for another 20 C. the Pumping is then stopped and the contents of the funnel were weighed and homogenized. The samples were analyzed for solids content, humidity (percentage of liquid) and the content of acetic acid in the cake.The concentration of the sludge was by weight 41%. The pressure difference between vacuum and ambient pressure was in the range of 10.5 - 10.9 psi (72,4 to 75.2 kN/m2). When this simulated version with a three-stage countercurrent washing, for what each stage was kept flowing liquid and used for subsequent leaching. Details are given in table. 2.Example 10. The example illustrates a multi-stage pressure washing water directed to the removal of acetic acid from the sludge formed by the crude terephthalic acid.Polusovetskaya filtration experiments were performed, the IP is STTM. Complete square filter was 0.12 m2. The raw stream is supplied to the filter, represented the sludge formed from the crude terephthalic acid and mixtures of acetic acid with water. Used crude terephthalic acid was characterized by an average particle size of 175 μm.The solids content in the formed slurry comprised by weight of 43%. Uterine fluid to 90% by weight consisted of acetic acid. Initial residual content of acetic acid on the cake, as it was established by calculation, was by weight 1193000 hours per million calculated on a dry cake of terephthalic acid. The slurry in an amount of about 200 gallons (757,08 l) was heated to 190oF (87, 78oC) in a vessel with stirring. Sliding flow from a path covering the pump was sent to the pilot filter. The pressure in this stream supported by the back pressure regulator.The slurry was admitted to the filter BHS-FESTTMand the cake was left on the Cup filter, and uterine fluid passed through the filter fabric in the collection. The resulting pellet was characterized by a height of about 20 mm. filter Elements containing wet cake, and then rotated sequentially through first with the Yu dry zone. The height of water above the surface was 0.5 inch (12.7 mm). Leaching was carried out using the pump discharge displacement when used in each washing with distilled water, heated to 190oF (87, 78oC). Drying was performed using the mass flow controllers when using dry nitrogen. Costs when washing or drying in each zone were set independently. After passing the third dry zone pellet was unloaded, at the same time inflating it from the other side and acting knife spring-action. The remains of the pellet in the cell, and then removed by washing the fabric with distilled water. Each filter cell is then rotated, moving in the power zone, in which the whole process would start again.Unloaded pellet was subjected to gas chromatographic analysis, the result of which was determined by the residual content of acetic acid in the cake, and the moisture content of the pellet (percentage of liquid). Details are given in table. 3.Example 18. The example illustrates the influence of the height of the pellet on the efficiency of the leaching of acetic acid.Filtration experiments were performed on test equipment sheet is steel. The cylinder was equipped with a shirt than was provided the opportunity to conduct experiments at elevated temperatures. The cylinder was manufactured in such a way that it could create pressure.The experiments were conducted, feeding into the apparatus 43% by weight slurry of terephthalic acid in acetic acid. The slurry was allowed to warm up to 190oF (87,78oC). In the initial experiment, the valve located on the two instruments, opened and lowered uterine fluid, forming a cake. The filter is then dumped the pressure in the filter have introduced a certain amount of flush water. Using a putty knife, directing the water on the side surface of the filtration apparatus than has eliminated the possibility of damaging the surface of the pellet. The amount of water used was 1/3 of the height of the wet pellet. The filter was then raised the pressure to the same magnitude at which there was a formation of the pellet, and the wash liquid was removed from the pellet. The pellet was then purged so that it becomes dry, and the purge were in a period of time equal to the duration of education cakes.Then the pellet was analyzed by defining it to a residual content of acetic acid, when EA height of the pellet. Details are given in table. 4.Example 26. The example illustrates a multi-stage countercurrent pressure washing water held in order to remove acetic acid from the sludge formed by the crude terephthalic acid.The slurry, containing by weight 43% of the crystallized solid terephthalic acid and mother liquor, served in working under pressure rotary filter type BHS-FEST(TM)with a speed of 6.1 lb/min (2767 g/min) at a pressure of 30 pounds per square inch (206,8 kN/m2and when 198oF (92,22oC). Filter type BHS-FEST(TM)was used to separate the solids from the mother liquor, countercurrent washing of solids in three stages of drying to remove excess moisture and unloading of solids at atmospheric pressure. The filter housing is divided into seven chambers designed to hold five different operations, which include education cakes, counterflow pressure washing (3 cameras), drying the pellet, unloading cakes and washing of the filter cloth. The drum filter, operating at a rate of 0.5 rpm, divided into twenty-filter cells. The total surface area of the filter fabric available on the drum, prinia cakes, counterflow pressure washing, drying the pellet, unloading cakes and washing of the filter cloth) are performed simultaneously. The filter described in the example flow of operations in a single filter cell.The filter cell is rotated in the chamber education tortillas. Raw sludge containing about 43% by weight of solid terephthalic acid with a temperature of 198oF (92,22oC) and about 90% by weight of acetic acid in the mother liquor, continuously pumped into the chamber at a pressure of 30 pounds per square inch (206,8 kN/M2). As the rotation of the filter cells moving through the chamber, the solids accumulate on the filter fabric, forming a cake thickness of 1 inch (25.4 mm). Uterine fluid passes through the filter cloth, entering into the inner tube of the filter. The pressure of the mother liquor in this inner tube is approximately equal to atmospheric pressure. The mother liquid is subjected to a reverse recirculation return in the process, which is achieved by pumping.The filter cell containing the now formed pellet leaves the chamber education cakes and rotates, consistently getting three wash pressure chamber, working is the second wash chamber. The second wash chamber is used for washing fluid, which is pumped from the third washing chamber. The third wash, the camera uses pure water, which is pumped into it continuously. The flushing liquid is discharged from the first wash chamber is recycled to return to the process by pumping, or it may be provided in the riser column for the separation of water and acetic acid, and acetic acid is then subjected to recirculation back into the process. The temperature of each of the washing chamber is approximately equal to 200oF (93,33oC). The drum filter is heated by steam, which ensures temperature uniformity during leaching. The pressure at each flushing the entrance is located in the region from 8 to 15 pounds per square inch (55,16 to 103,43 kN/m2) relative to the ambient pressure and is therefore, what is necessary for the formation of flow of the discharged washing liquid from the preceding stage to the subsequent stage. Reset with each washing stage is effectively carried out at atmospheric pressure. Clean water coming into the third stage, is used again at the previous two stages and, given the effectiveness of pressure is awasa in the filtration cell, leaves the chamber pressure washing and enters the drying chamber of the pellet. In the drying chamber continuously served the compressed inert gas being at a pressure of about 20 psi (137,9 kN/m2), which ensures the removal of excess water from the filter cake. Excess water is connected with the discharged liquid emerging from the third washing chamber, and used to wash second wash chamber.The filter cell is rotated, moving from the drying chamber into the chamber unloaded pellet. The cake discharged from the filter using spring scraper with blade edge, making it at a flow rate of about 3 lb/min (1360 g/min). The final pellet has a concentration of acetic acid, which can be carried out further purification. The final levels of acetic acid depends on the relative amount of added water or from the relationship of the amount of water being recirculated return in the oxidation process, the amount of terephthalic acid in the cake, prepared for further purification. The amount of clean water used in the third washing chamber is in direct communication with the relative number of EXT is in the flushing chamber of the filter fabric, it ensures the removal of all traces, remaining tortillas. Filter the cell then enters the chamber education cakes, and the whole process repeats.The results of the experiments are given in table. 5. 1. A method of obtaining a crude aromatic polycarboxylic acid by oxidation of the corresponding alkylaromatic hydrocarbon in the presence of aliphatic carboxylic acids C1- C5obtaining crude polycarboxylic acid containing an aliphatic carboxylic acid held in the mother liquor, in which the concentration of the aliphatic carboxylic acid based on the weight of the crude polycarboxylic acid, 5000 hours 1 million by weight or less, after oxidation, the flow of sludge crude aromatic polycarboxylic acid in the mother liquor containing aliphatic carboxylic acid, C1- C5served on the filter, which produce a filter cake which was washed with water under pressure to displace aliphatic carboxylic acid, with subsequent discharge of the target product, characterized in that the filter use the filter cell or a series of filter cells whose location on the Oia sludge in each filter cell, after the formation of filter cakes stream of sludge interrupt, then enter the flow of water in each filter cell with the formation of a water reservoir having a depth sufficient to flooding filter cakes and covering its surface, the pressure under which the washed filter cake is 3.5 - 448 kN/m2and unloading of the target product is carried out of the filter cell or a series of filter cells.2. The method according to p. 1, characterized in that alkylaromatics hydrocarbon selected from the group consisting of p-xylene or m-xylene, or diisopropylbenzene, or diethylbenzene, or 2,6-dimethylnaphthalene.3. The method according to p. 1, characterized in that the introduction of water flow and displacement of aliphatic carboxylic acids of the filter cakes for lowering the concentration of aliphatic carboxylic acid in the cake up to 5000 hours 1 million or less by weight based on the weight of available crude polycarboxylic acids perform a counter-current manner in which each of the filter cake washed sequentially in reverse order of the degree of pollution.4. The method according to p. 1, characterized in that alkylaromatics ugg, the crude aromatic polycarboxylic acid is a crude terephthalic acid.5. The method according to PP. 1 and 4, characterized in that the height of the filter cakes is 51.8 is 203.2 mm
FIELD: crystal growing.
SUBSTANCE: invention relates to adipic acid crystals and treatment thereof to achieve minimum crystal caking. Crystals are prepared by crystallization of adipic acid from aqueous medium or between treating it with aqueous solution. Crystals are then subjected to ripening stage, that is crystals are held at temperature between 10 and 80°C until content of exchangeable water in crystals falls below 100 ppm, while using an appropriate means to maintain ambient absolute humidity at a level of 20 g/m3. Renewal of ambient medium is accomplished by flushing crystal mass with dry air flow having required absolute humidity. Means to maintain or to lower absolute humidity contains moisture-absorption device placed in a chamber. Content of exchangeable water in crystals is measured for 300 g of adipic acid crystals, which are enclosed in tightly sealed container preliminarily flushed with dry air and containing 2 g of moisture absorbing substance. In chamber, temperature between 5 and 25°C is maintained for 24 h. Content of water will be the same as amount of water absorbed by absorbing substance per 1 g crystals. Total content of water exceeds content of exchangeable water by at least 20 ppm.
EFFECT: minimized caking of crystals and improved flowability.
13 cl, 5 ex
FIELD: organic chemistry, chemical technology.
SUBSTANCE: invention relates to the improved method for isolating crystalline terephthalic acid comprising less 150 mas. p. p. per million (ppm) of p-toluic acid with respect to weight of terephthalic acid. Method involves the following steps: (1) preparing a solution containing from 10 to 35 wt.-% of dissolved terephthalic acid wherein from 150 to 1100 ppm of p-toluic acid is dissolved with respect to mass of terephthalic acid at temperature from 260°C to 320°C and under pressure providing maintaining the solution in liquid phase; (2) charge of solution from step (1) to crystallization zone comprising multitude amount of associated crystallizers wherein the solution is subjected for cooling at evaporation at the controlled rate by the moderate pressure and temperature reducing resulting to crystallization of terephthalic acid and wherein the solution pressure at the end of crystallization zone is equal to atmosphere pressure or lower; (3) condensation of solvent evaporated from crystallizers and recovering the condensed solution to the crystallization zone to place of descending flow from crystallizer wherein solvent is removed by evaporation, and (4) isolation of solid crystalline terephthalic acid comprising less 150 ppm of p-toluic acid with respect to the terephthalic acid mass by separation of the phase liquid-solid substance under atmosphere pressure. The advantage of method is preparing the end product in improved crystalline form and carrying out the process under atmosphere pressure or pressure near to atmosphere pressure.
EFFECT: improved method of crystallization.
3 cl, 1 dwg, 1 tbl, 2 ex
FIELD: chemical industry; methods of production of the purified crystalline terephthalic acid.
SUBSTANCE: the invention is pertaining to the improved method of production and separation of the crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid. The method provides for the following stages: (1) loading of (i) para- xylene, (ii) the water reactionary acetic-acidic medium containing the resolved in it components of the oxidation catalyst, and (iii) the gas containing oxygen fed under pressure in the first zone of oxidation, in which the liquid-phase exothermal oxidization of the para-xylene takes place, in which the temperature and the pressure inside the first being under pressure reactor of the oxidization are maintained at from 150°С up to 180°С and from 3.5 up to 13 absolute bars; (2) removal from the reactor upper part of the steam containing the evaporated reactionary acetic-acidic medium and the gas depleted by the oxygen including carbon dioxide, the inertial components and less than 9 volumetric percents of oxygen in terms of the non-condensable components of the steam; (3) removal from the lower part of the first reactor of the oxidized product including (i) the solid and dissolved terephthalic acid and (ii) the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (4) loading of (i) the oxidized product from the stage (3) and (ii) the gas containing oxygen, into the second being under pressure zone of the oxidation in which the liquid-phase exothermal oxidization of the products of the non-complete oxidization takes place; at that the temperature and the pressure in the second being under pressure reactor of the oxidization are maintained from 185°С up to 230°С and from 4.5 up to 18.3 absolute bar; (5) removal from the upper part of the second steam reactor containing the evaporated water reactionary acetic-acidic medium and gas depleted by the oxygen, including carbon dioxide, the inertial components and less, than 5 volumetric percents of oxygen in terms of the non-condensable components of the steam; (6) removal from the lower part of the second reactor of the second oxidized product including (i) the solid and dissolved terephthalic acid and the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (7) separation of the terephthalic acid from (ii) the water reactionary acetic-acidic medium of the stage (6) for production the terephthalic acid containing less than 900 mass ppm of 4- carboxybenzaldehyde and the p-toluene acid; (8) dissolution of the terephthalic acid gained at the stage (7) in the water for formation of the solution containing from 10 up to 35 mass % of the dissolved terephthalic acid containing less than 900 mass ppm of the 4- carboxybenzaldehyde and the p-toluene acid in respect to the mass of the present terephthalic acid at the temperature from 260°С up to 320°С and the pressure sufficient for maintaining the solution in the liquid phase and introduction of the solution in contact with hydrogen at presence of the catalytic agent of hydrogenation with production of the solution of the hydrogenated product; (9) loading of the solution of the stage (8) into the crystallization zone including the set of the connected in series crystallizers, in which the solution is subjected to the evaporating cooling with the controlled velocity using the significant drop of the temperature and the pressure for initiation of the crystallization process of the terephthalic acid, at the pressure of the solution in the end of the zone of the crystallization is atmospheric or below; (10) conduct condensation of the dissolvent evaporated from the crystallizers and guide the condensed dissolvent back into the zone of the crystallization by feeding the part of the condensed dissolvent in the line of removal of the product of the crystallizer, from which the dissolvent is removed in the form of the vapor; and (11) conduct separation of the solid crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid by separation of the solid material from the liquid under the atmospheric pressure. The method allows to obtain the target product in the improved crystalline form.
EFFECT: the invention ensures production of the target product in the improved crystalline form.
8 cl, 3 tbl, 2 dwg, 3 ex
SUBSTANCE: invention pertains to the perfection of the method of regulating quantities of dissolved iron in liquid streams during the process of obtaining aromatic carboxylic acids or in the process of cleaning technical aromatic carboxylic acids, characterised by that, to at least, part of the liquid stream for regulating the quantity of dissolved iron in it, at least one peroxide with formula R1-O-O-R2 is added. Here R1 and R2 can be the same or different. They represent hydrogen or a hydrocarbon group, in quantities sufficient for precipitation of the dissolved iron from the liquid. The invention also relates to the perfection of the method of obtaining an aromatic carboxylic acid, through the following stages: A) contacting the crude aromatic material which can be oxidised, with molecular oxygen in the presence of an oxidising catalyst, containing at least, one metal with atomic number from 21 to 82, and a solvent in the form of C2-C5 aliphatic carboxylic acid in a liquid phase reaction mixture in a reactor under conditions of oxidation with formation of a solid product. The product contains technical aromatic carboxylic acid, liquid, containing a solvent and water, and an off-gas, containing water vapour and vapour of the solvent; B) separation of the solid product, containing technical aromatic carboxylic acid from the liquid; C) distillation of at least part of the off gas in a distillation column, equipped with reflux, for separating vapour of the solvent from water vapour. A liquid then forms, containing the solvent, and in the upper distillation cut, containing water vapour; D) returning of at least, part of the liquid from stage B into the reactor; E) dissolution of at least, part of the separated solid product, containing technical aromatic carboxylic acid, in a solvent from the cleaning stage with obtaining of a liquid solution of the cleaning stage; F) contacting the solution from the cleaning stage with hydrogen in the presence of a hydrogenation catalyst and under hydrogenation conditions, sufficient for formation of a solution, containing cleaned aromatic carboxylic acid, and liquid, containing a cleaning solvent; G) separation of the cleaned aromatic carboxylic acid from the solution, containing the cleaning solvent, which is obtained from stage E, with obtaining of solid cleaned aromatic carboxylic acid and a stock solution from the cleaning stage; H) retuning of at least, part of the stock solution from the cleaning stage, to at least, one of the stages B and E; I) addition of at least, one peroxide with formula R1-O-O-R2, where R1 and R2 can be the same or different, and represent hydrogen or a hydrocarbon group, in a liquid from at least one of the other stages, or obtained as a result from at least one of these stages, to which the peroxide is added, in a quantity sufficient for precipitation of iron from the liquid.
EFFECT: controlled reduction of the formation of suspension of iron oxide during production of technical aromatic acid.
19 cl, 1 dwg, 6 ex, 4 tbl
SUBSTANCE: invention relates to an improved method, by which the carboxylic acid/diol mixture, that is suitable as the initial substance for the manufacture of polyester, obtained from the decolourised solution of carboxylic acid without actually isolating the solid dry carboxylic acid. More specifically, the invention relates to the method of manufacturing a mixture of carboxylic acid/diol, where the said method includes the addition of diol to the decolourised solution of carboxylic acid, which includes carboxylic acid and water, in the zone of the reactor etherification, where diol is located at a temperature sufficient for evaporating part of the water in order to become the basic suspending liquid with the formation of the specified carboxylic acid/diol mixture; where the said carboxylic acid and diol enter into a reaction in the zone of etherification with the formation of a flow of a complex hydroxyalkyl ether. The invention also relates to the following variants of the method: the method of manufacture of the carboxylic acid/diol mixture, where the said method includes the following stages: (a) mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of damp carboxylic acid; where the said carboxylic acid is selected from the group, which includes terephthalic acid, isophthatic acid, naphthalenedicarboxylic acid and their mixtures; (b) discolourisation of aforesaid solution of damp carboxylic acid in the zone for reaction obtaining the decolourised solution of carboxylic acid; (c) not necessarily, instantaneous evaporation of the said decolourised solution of carboxylic acid in the zone of instantaneous evaporation for the removal of part of the water from the decolourised solution of carboxylic acid; and (d) addition of diol to the decolourised solution of carboxylic acid in the zone of the reactor of the etherification, where the said diol is located at a temperature, sufficient for the evaporation of part of the water in order to become the basic suspending liquid with the formation of the carboxylic acid/diol mixture; where the aforesaid carboxylic acid and diol then enter the zone of etherification with the formation of the flow of complex hydroxyalkyl ether; and relates to the method of manufacture of carboxylic acid/diol, where the said method includes the following stages: (a) the mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of carboxylic acid; (b) discolourisation of the said solution of damp carboxylic acid in the reactor core with the formation of the decolourised solution of carboxylic acid; (c) crystallisation of the said decolourised solution of carboxylic acid in the zone of crystallisation with the formation of an aqueous suspension; and (d) removal of part of the contaminated water in the aforesaid aqueous solution and addition of diol into the zone of the removal of liquid with the obtaining of the said carboxylic acid/diol mixture, where diol is located at a temperature sufficient for evaporating part of the contaminated water from the said aqueous suspension in order to become the basic suspending liquid.
EFFECT: obtaining mixture of carboxylic acid/diol.
29 cl, 4 dwg
SUBSTANCE: method of separating multi-atom alcohols, for instance, neopentylglycol and sodium formiate, includes evaporation and cooling of reaction mixture, addition of organic solvent, crystallisation of sodium formiate, separation of sodium formiate from saturated solution of multi-atom alcohol, for instance, by filtration, and crystallisation of multi-atom alcohol. Reaction mixture is evaporated until two liquid layers are formed, which are separated into light phase - water-multi-atom alcohol and heavy phase -water-salt, separated water-salt fraction of solution is cooled until sodium formiate contained in it in form of cryslallohydrate is crystallised, sodium formiate crystals are separated, and remaining mother-solution is returned to process head, to evaporation stage, then separated light phase - water-multi-atom alcohol is additionally evaporated until 70% of contained in it sodium formiate is crystallised, then cooled to 25-30°C and subjected to processing with organic solvent from line of single-atom saturated alcohols, for instance, methane, for removal of remaining admixtures, with further crystallisation of multi-atom alcohol from remaining mother-solution.
EFFECT: reduction of amount of used organic solvent, elimination of high-temperature stage of extraction, preservation of yield of pure target products.
2 cl, 2 dwg, 1 ex
SUBSTANCE: method of obtaining product - purified carboxylic acid, includes: (a) oxidation of aromatic initial materials in primary oxidation zone with formation of raw carboxylic acid suspension; where raw carboxylic acid suspension contains terephthalic acid; where said oxidation is carried out at temperature within the range from 120°C to 200°C; (b) withdrawal of admixtures from raw suspension of carboxylic acid, removed at temperature from 140°C to 170°C from stage of oxidation of paraxylol in primary oxidation zone and containing terephthalic acid, catalyst, acetic acid and admixtures, realised in zone of solid products and liquid separation with formation of mother liquid flow and product in form of suspension; where part of said catalyst in said suspension of raw carboxylic acid is removed in said mother liquid flow; and where into said zone of solid products and liquid separation optionally additional solvent is added; (c) oxidation of said product in form of suspension in zone of further oxidation with formation of product of further oxidation; where said oxidation is carried out at temperature within the range from 190°C to 280°C; and where said oxidation takes place in said zone of further oxidation at temperature higher than in said primary oxidation zone; (d) crystallisation of said product of further oxidation in crystallisation zone with formation of crystallised product in form of suspension; (e) cooling of said crystallised product in form of suspension in cooling zone with formation of cooled suspension of purified carboxylic acid; and (i) filtration and optionally drying of said cooled suspension of purified carboxylic acid in filtration and drying zone in order to remove part of solvent from said cooled suspension of carboxylic acid with obtaining of said product - purified carboxylic acid.
EFFECT: purified carboxylic acid with nice colour and low level of admixtures, without using stages of purification like hydration.
8 cl, 1 tbl, 1 dwg, 1 ex
SUBSTANCE: proposal is given of a method of removing impurities from a water mixture or purified water mixture through extraction of the water mixture or purified water mixture using an extractive solvent in the extraction zone with formation of a stream of extract and a stream of raffinate and, optionally, separation of the extract stream and the solvent rich stream in the separation zone with formation of a stream of organic impurities with high boiling point and a stream of extractive solvent.
EFFECT: provision for extracting metallic catalyst in active form, reusable at the paraxylene recycling stage.
29 cl, 2 dwg, 1 tbl
SUBSTANCE: invention relates to a thermal separation method using fractional condensation of a product-gas mixture, obtained through heterogeneous catalysed partial oxidation of propene and/or propane in gaseous phase to acrylic acid, for separating at least one mass flow, concentrated with acrylic acid, from a product-gas mixture containing acrylic acid, which involves continuous static operation of at least one device for thermal separation, containing at least one effective separation chamber with a fractionation column which has mass-transfer trays as built-in separating elements, in which the product-gas mixture is loaded, containing acrylic acid as at least one mass flow, and from which at least one mass flow containing acrylic acid is unloaded under the condition that, the overall mass flow loaded into the effective separation chamber and obtained from combining separate mass flows loaded into the separating chamber, contains X wt % components distinct from acrylic acid, the mass flow which is unloaded from the effective separation chamber with the largest content of acrylic acid, contains Y wt % components distinct from acrylic acid, ratio X:Y is ≥5, effective separation chamber, except the loading and unloading place, is bordered by a solid phase and contains, besides the mass-exchange trays as built-in separating elements in the fractionation column, at least one circulating heat exchanger, and total volume of the chamber, filled with liquid phase, is ≥1 m3, wherein temperature of the liquid phase is at least partially ≥80°C, when the effective separation chamber is divided into n separate volume elements, wherein the highest and lowest temperature of liquid phase in a separate volume element differ by not more than 2°C, and the volume element in the effective separation chamber is solid, total dwell time ttotal.
≤20 h, where A = (Ti-To)/10°C, To= 100°C, Ti = arithmetic mean value of the highest and lowest temperature of the ith volume element in the liquid phase in °C, msi = total mass of acrylic acid in the volume of the liquid phase of the ith volume element, mi = total liquid phase mass unloaded from the ith volume element, and is the sum of all volume elements i, under the condition that, volume elements i with liquid phase mass mi and as volume elements with a dead zone are also not included in the sum of all volume elements i, as well as volume elements i, which do not contain liquid phase, and total amount of liquid phase contained in volume elements with a dead zone is not more than 5 wt % of the total amount of liquid phase contained in the effective separation chamber.
EFFECT: separation of mass flow concentrated with acrylic acid.
10 cl, 12 dwg, 2 ex, 2 tbl
SUBSTANCE: sodium hydroxide solution is added to a technical mixture of benzoic and cinnamylic acid, obtaining a precipitate. Water is added to obtain a homogeneous solution. The obtained technical mixture of sodium salts of benzoic and cinnamylic acid with composition ranging from 2:1 to 1:2 and overall concentration ranging from 3 to 5 M is then mixed with sulphuric acid with concentration ranging from 3 to 5 M. Addition of sulphuric acid is stopped at pH of the medium between 8 and 9, and the precipitated complex of cinnamylic acid with its sodium salt is filtered from the reaction mixture, dissolved in excess amount of water to dissolve sodium salt of cinnamylic acid. Cinnamylic acid precipitates, and is further treated with sulphuric acid with concentration ranging from 3 to 5 M to pH between 1 and 2. The precipitated crystals of cinnamylic acid are separated; the reaction mixture remaining after separation of the complex is mixed with a solution of sulphuric acid with concentration ranging from 3 to 5 M until pH between 1 and 2. As a result, crystalline benzoic acid forms.
EFFECT: formation of complexes of carboxylic acids with their sodium salts for separating components of a mixture of carboxylic acids with similar chemical and physico-chemical properties.
FIELD: process engineering.
SUBSTANCE: invention relates to processing waste gases in production of aromatic dicarboxylic acid by liquid phase oxidation of aromatic dialkyl hydrocarbon, an initial substance, using acetic acid as a solvent, in the presence of metallic catalyst containing, as a promoter, cobalt, manganese and bromine at reactor temperature of 185 to 205°C and using oxygen-containing gas, that comprises the following stages: oxidation reaction waste gas is cooled down and separated. After condensation, waste gas condensing components are separated at high pressure. Obtained waste gas is subjected to wet cleaning at 40°C or lower temperature in high-pressure absorption columns by rinsing fluid into two stages to reduce concentration of components contained therein. Said waste gas at 12.0-16.0 kg/cm2(surplus) is forced through two-stage pressure turbines after heating of said gas fed to turbine first and second stage by steam at pressure of approx. 5 kg/cm2 (surplus) to 140°C - 150°C. Note here that two-stage turbines are used with second stage-to-first stage power ratio varying from 1 to 1.4 to obtain heat- and waste-gas-generated power in compliance with the formula below: (T2/T1)γ=(P2/P1)(γ-1), where γ = Cp/Cv = 1.4, T1, P1 are temperature and pressure at inlet side, T2, P2 are those at outlet side, γ is relation between specific heat capacity at constant pressure Cp to specific heat capacity at constant volume Cv.
EFFECT: efficient process and system.
6 cl, 9 tbl, 3 dwg
SUBSTANCE: invention relates to a method and a mixture for oxidising an alkyl aromatic compound. The mixture contains: an alkyl aromatic compound, a solvent, a bromine source, a catalyst and ammonium acetate; wherein the solvent includes a carboxylic acid having 1-7 carbon atoms and optionally water, and the catalyst substantially consists of at least one metal selected from cobalt, titanium, manganese, chromium, copper, nickel, vanadium, iron, molybdenum, tin, cerium and zirconium, present in form of acetates or hydrates thereof.
EFFECT: present invention enables to obtain products of higher purity which enables to eliminate or minimise purification costs.
10 cl, 1 tbl, 3 ex
SUBSTANCE: invention relates to a mixture for oxidation of an alkylaromatic compound, containing: an alkylaromatic compound, a solvent, a brome source and a catalyst, with the solvent containing carboxylic acid, containing from 1 to 7 carbon atoms, as well as a ionic liquid, selected from the group, consisting of an imidazole ionic liquid, pyridine ionic liquid, phosphonium ionic liquid, tetraalkylammonium ionic liquid and their combinations, and, optionally, water; with the solvent being characterised by a ratio of the ionic liquid to carboxylic acid, being in the range from 1:10 to 10:1 by weight; and the catalyst contains, at least, one of the group: cobalt, titanium, manganese, chrome, copper, nickel, vanadium, iron, molybdenum, tin, cerium and zirconium.
EFFECT: application of the method makes it possible to regulate the amount of admixtures in the solid product of oxidation.
9 cl, 1 tbl, 9 ex
SUBSTANCE: invention relates to a method of recovering an aromatic carboxylic acid and an oxidation catalyst from an output stream from a process of producing aromatic polycarboxylic acids via liquid-phase oxidation of the corresponding aromatic precursor, the method comprising: (a) blowing off at least a portion of the mother solution of the process of producing an aromatic polycarboxylic acid into a solvent extraction system to obtain a concentrate containing organic compounds along with a catalyst as a residual stream; (b) separating the residual stream into a dicarboxylic acid rich stream, a catalyst and tricarboxylic acid rich stream, and a monocarboxylic acid rich stream via simultaneous extraction of the residual stream with two liquid phases using water and an organic solvent, followed by filtering; (c) separating benzoic acid and para-toluic acid and/or one of the isomers thereof from the monocarboxylic acid rich stream, extracting benzoic acid, extracting para-toluic acid and/or one isomer thereof; (d) separating terephthalic acid and isophthalic acid from the dicarboxylic acid rich stream, extracting terephthalic acid, extracting isophthalic acid; (e) separating trimellitic acid from the catalyst and tricarboxylic acid rich stream and extracting trimellitic acid; (f) separating a cobalt salt and a manganese salt from the catalyst and tricarboxylic acid rich stream.
EFFECT: enabling recovery of valuable chemical substances from a purge stream.
12 cl, 1 dwg