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    1476436 Recovery of crystalline terephthalic acid STANDARD OIL CO 19 Aug 1974 [20 Aug 1973] 36449/74 Heading C2C A process for the recovery of crystalline terephthalic acid product having a maximum p-toluic acid content not exceeding 150 p.p.m. by weight from a liquid aqueous solution substantially saturated with terephthalic acid containing 500-6000 p.p.m. of p-toluic acid at a temperature in the range of 400‹ to 550‹ F., comprises continuously charging such aqueous solutions to the first of two or more stirred zones connected in series and each operated at a successively lower temperature wherein decreasing proportions of originally dissolved terephthalic acid are crystallized in at least the zones operated at a temperature within and below the range of 360-320‹ F., flash evaporated solvent is removed from each zone and the temperature of recovery of terephthalic acid product is the same as the temperature of the last zone.
    公开号:SU869554A3
    申请号:SU742055522
    申请日:1974-08-19
    公开日:1981-09-30
    发明作者:Арнольд Фишер Джей
    申请人:Стандарт Ойл Компани；
    IPC主号:
    专利说明:

    (54) OTISPSI TEPEFTAJSHBOY
    I
    Somewhat referred to as an improved method for terephthalic acid release (TPA), which is used for bulk fibers.
    A known method of purification of terephthalic acid by crystallization, in which Kpt-metalization is carried out by evaporating the solution to carry out the cooling necessary for precipitating crystalline terephthalic acid, provided that during the process of parity cooling the shock cooling solution is avoided, which could be in case of instantaneous spraying of the solution, since, as such, the dissolved minerals are co-precipitated, the contaminated product — the terephthalic} s schlot. To prevent the contaminating effect of such a shock cooling in this method, evaporative cooling is controlled by evaporating a uniform back pressure, for example, by throttling the release of steam 20 at equilibrium pressure. In fact, this is the effect of perfect cooling at a regular rate.
    According to the well-known method of kr $ 1 stallation by spontaneous cooling with 25 ACIDS
    This rate of speed is applied to the days of neiqiepba ny krtstallizacin, which are carried out in three consecutive combined stages with a 3-4 h drop in pace | pries from 276 to the chief stagat to 1M) ° C m of the third cTajoM {1.
    However, such a crystalline crystal, providing an average rate of cooling at 0.8 ° C for 1 hour, is not only excessively slow in terms of terephthalic solutions with 0.24% para-toluic acid content, but also gives a terephthalic terminal, containing 0.12% of para-toluic acid . Such a product is unacceptable. for direct reaction with ethylene glycol for polyester fiber production.
    The goal of the retention system is to increase the effectiveness of the protrusion and purity of the target.
    The goal is achieved by the fact that in the process of cleaning terephthalic acid with an aqueous solution, it has a primary temperature within 204-288 ° C, which is crystallized by cooling the specified solution in several boundaries. ““ I am waiting for myself the zones of the Krnstadlnasch, the latter of which has a temperature of 109-149 ° C, one of the crystallization zones has a temperature of 160182 ° C. The method allows to obtain TPA with a content of 0.015% by weight or less of paratoluyl acid from volokia, applicable to aqueous solutions of TPA containing 0.050, 6% by weight paratoluic acid, using almost instantaneous crystallization of portions of dissolved TPA in a small number, not less than two connected in series crystallization zones. Such continuous crystallization can be applied to aqueous solutions of nearly saturated TPA at 204–288 ° C and provided that at least the last zones operate at 182–160 ° C and below, it is preferable. All zones operate like, that smaller and smaller portions crystallize. originally dissolved TPA. The choice of the actual and effective number of consecutively mixed mixed crystallization zones using instant water evaporation is related to the concentration of para-toluic acid, calculated on TFA, and not from the concentration of para-toluic acid supplied to any zone, since the crystallization of each portion of TPA is almost instantaneous and to what extent does not depend on the technique of crystallization of TFA. For such dissolved TPA containing 0.05–0.6 wt.% Para-toluic acid, the number of instantaneous vapors of the solvent will not exceed eight mixed crystallization zones. For example, two zones are available at a content of 0.05-0.1% para-toluic acid, three zones at 0.05-0.4% and from five to eight zones at a content of 0.2-0.6% para-toluic acid , cstu on the initial content of TFA in solution. However, the number of zones associated with the concentrations of para-toluic acid in TPA is not the only one. Each portion of the evaporated original with held water from each 2-8, more preferably 3-6 zones, instantaneous evaporation does not rotate at any stage of the process. The choice of operating temperature for instantaneous evaporation of the solvent can be made in a curve for the ultimate TPA; depending on the temperature so that the gradient of the teletterature of the whole process corresponds to this curve. The method of non-crystalline crystallization of TPA is based on the fact that contamination of the final TPA product by removing para-toluic acid from its unsaturated solution is more dependent on temperature than on cooling rate. Greater flexibility of the method is possible both with respect to the content in the initial aqueous solution of dissolved TPA and its content of 0.05-0.6% by weight of toluic acid, and in choosing the number of crystallization zones that are stirred and even the final quality of the TPA product. Temperature-dependent removal of para-toluic acid occurs after the temperature reaches 182-160 ° C. The crystallized initially dissolved TPA crystalline portions in each zone can be significant until reaching 182-160 ° C, and then each crystallized portion decreases, but is not limited to the critical limiting individual portions of initially dissolved TPA. The key factor for choosing a temperature gradient for crystallization zones from 182 to 160 ° C below, includes choosing a zone temperature such that each crystallized portion of TPA at each stage is progressively less than in the previous zone. This not only reduces the proportion of TFA crystallized below 171-160 ° C, but also reduces the contamination of para-toluic acid. Regarding the use of flash evaporation of the solvent by co-precipitating TFA crystals, controlling the final crystallization temperature and separating the product at 121-149 ° C or controlling the rate of crystallization of TFA is not applicable to limit the contamination with para-toluic acid obtained as a product of TFA. -. Example i (cf. Aqueous pactor of 20 wt.% TFA and 0.25% toluic acid (counting on TFA) at 268 ° C and pressure of 56.25 kg / cm is fed to a stirred crystallization zone operating at 149 ° C and 4.7 kg / cm through the flow control valve at the inlet to the mold. Steam generated by instantaneous evaporation of water from 268 to 149 ° C is removed; from the enclosure, condensed and discharged. The resulting suspension of TFA crystals is centrifuged at 149 ° C and a pressure of 4.7 kg / cm. Solid crystalline TPA is dried. The resulting TPA contains 0.12% by weight of para-paraic acid. PRI mme R 2. (comparative). The operations are repeated, similar to example 1, but the content of para-toluic acid in TPA is 0.05% by weight. The obtained dry TPA contains 0.025% by weight of para-toluic acid. PRI me R 3 (comparative). TPA, containing 0.25 wt.% Para-toluic acid, is dissolved in water at 277 ° C and 6.3 kg / cm pressure. Get a solution containing 20 wt.% TFA. For continuous operation, four zones of crystallization are connected in series. The temperature gradient was chosen so that equal portions of initially pacraopei TFA crystallized in each zone. The corresponding working temperatures (° C) and pressure (kg / cm) are: 261 and 42.7; 252 and 40.85; 237 and 31.43; 149 and 4.7. The solution is fed to the first zone at a rate of 45.4 kg / h. The amount of water vapor released in each zone, respectively, is kg / h: 14.3; 19.52; 14.5 and 31.9. Corresponding amounts of crystallizable TPA are as follows, kg / h: 12.86 11.34. 11.2; 10.38. The suspension flows out of the fourth zone at a rate of 159 kg / h and contains 45.17 kg of suspended solids and 116 kg of mother liquor. This suspension is centrifuged at 149 ° C and a pressure of 4.7 kg / cm. The resulting dried TPA contains 0.042% para-toluic acid. In the above work, there is an appropriate number of crystallized zones as shown later in examples 1-3, the final crystallization and separation temperature corresponds to the prior art, and the temperature gradient is logically acceptable from the previous velocity dependence. But the end product of TPA in these cases is of unacceptable quality (much more than 0.015% paratoluic acid), since the portion crystallized at 149 ° C is too large. The aqueous solution supplied to the first of 2-8, preferably 3-6, flash evaporation zones, when according to the invention the concomitant crystallization of TPA is almost instantaneous, can be an almost saturated aqueous solution at 204-288 ° C, which corresponds to a concentration of 0.002 TPA. -0.005 wt.% Per 100 hours of water. The content of para-toluic acid in this dissolved TPA is in the range of 0.05-0.6 wt.%. For economic reasons, it is preferable that the solutions supplied to the first zone contain 10-30 hours of TPA per 100 parts of water. The corresponding saturation temperatures for TFA are 24-271 ° C. However, to prevent premature crystallization of TFA for the time of transfer to the first zone (from purification by catalytic hydrogelling {isation into the first zone), it is preferable that these solutions containing 10-30 hours TFA per 100 hours. were at a temperature of at least 5-10 ° C higher than the saturated temperature and preferably at 250-280 ° C. In addition, the crystalline magma obtained is easily separated by centrifugation, despite the fact that instantaneous crystallization of TFA from solution gives crystalline This magma contains crystals of a sufficiently small size for driving sediment pressed on a centrifuge and makes continuous industrial separation of a liquid and a solid by centrifugation impossible during industrial operation. The following examples illustrate the expedient implementation of the proposed method with the use of TFA solutions of various concentrations of various concentrations of para-tolunic acid in the range of 0.05-0.6%, mixed 1xX of instant evaporation - crystallization of TFA within 2-8, and various The temperatures dp of the final crystallization of TPA are even lower than 100 ° C. In all examples, the solution, counted on TPA, is fed into the first one. these zones with a speed of kg / h. The TPA is separated by continuous centrifugation, washed with fresh water to separate the adhering mother liquor, and then dry. Aqueous washing of the product by centrifuging TPA reduces the content of para-toluic acid in TPA only on the amount of it remaining dissolved in the adhering small amount of mother liquor. In each of the following three examples, the solutions supplied to the first zone contain 20 wt.% TFA with 0.0025% para-toluic acid. Such a solution is maintained at 268 ° C (3 ° C above the saturation temperature) and a pressure of 56.2 kg / cm to maintain the water in a decar state. There are stages of flash evaporation of the solvent 3.5 and 6. Examples 1-3. For 3.5 and 6 zone flash evaporation and crystallization, the above solution is fed to the first zone. Magma (crystals plus solution) obtained in the first stirred zone is successively fed to each subsequent zone. The magma obtained in the last zone is continuously fed to the centrifuge. In all three cases, the last stirred zone and centrifuge are operated at 149 ° C and a pressure of 4.7 kg / cm. The temperature and pressure for each stage of crystallization and centrifuge operation at 3.5 and 6 successively connected stirred zones, as well as the content of para-toluic acid in otfugovannom cake of these processes are presented in table. 1. Examples 4-6. The process is repeated as in Examples 1-3. The use of feed solutions, the number of mixed zones, temperatures and pressures used in fepax 4-6, are presented in table. 2. In example 5, the temperature difference between the supply between the first zone and the next is almost dinac. In this work, smaller amounts of crystallized PC are obtained, but 83.4, 13.7 and 2.45% of initially dissolved TPA in zones 1, 2 and 3 are obtained. Example 7 The feed solution contains 20% by weight TPA with with a content of 0.161% para-moon acid and most preferably tartrate of 276 ° C, pressure 60.7 kg / cm to maintain the water in a liquid state. This solution is continuously fed at a rate of 45.3 kg / h (counting on FC) to the first of six zones. The conditions of operation in each zone, the percentage of crystallized TPA per hour, the temperature and pressure during centrifuge operation, the percentage of TPA extracted and the content of {unwashed para-toluic acid in it are shown in Table. 3. From table. 3, it can be seen that almost equal amounts of TPA crystallize in zones 1 and 2, and the total amount of crystalline TPA is 93% by weight of that contained in the feed solution. The TPA obtained in Example 7 is unique in terms of particle size distribution. This product has some sort of particle distribution from 0 to 450 microns, a large particle size has a particle size of 250 microns and there are two peaks in the particle size distribution. Such a particle size distribution is characteristic of a bimodal distribution, rather than the normal distribution of particles from conventional crystallization. Thus, the procedure of Example 7 indicates the path to a unique crystalline TFA for the fiber. Such a bimodal crystalline product can be obtained by crystallization of 75-95% of the total TPA in almost equal proportions in the first two of 3-6 successively connected stirred zones, according to the proposed method. Example 8 and Example 4 (comparative). Example 4 is similar to example 8, but there is no crystallization zone operating at 166 ° C and crystallizing at 13 a proportion of the starting TPA equal to the sum of portions crystallized in example 8 in the zones operating at 166 and 13 5 ° C. The feed solutions have a temperature 276 ° C and a pressure of 60.4 kg / cm to keep the water in a liquid state and contain 18% by weight TFA containing 0.2% para-toluene acid. Such solutions are fed to the first of a series of successively connected crystallization zones at a rate of 45.3 kg of TFA per hour. The conditions of operation in the zones (temperature and pressure) fi in the centrifuge, the weight percent of TFA crystallized in each zone, the total pro, cent crystallized TFA, and the content of para-toluic acid in the resulting TFA product are shown in Table. 4. PRI me R 9. A simple rinsing of the centrifuge cake is performed with fresh water at 93396 ° C. As a result, the content of para-toluic acid in the washed and dried product is reduced to less than 0.0150%. Washing of the product of Comparative Example 4 does not give such a content of para-toluic acid. Analysis of the product after the third crystallization zone of Example 4 shows the content of para-toluic acid is greater than 0.02%. Therefore, the work of example 4 should be avoided. Examples 10, 11 and 12. The feed solutions contain 20% TFA with different content of para-toluic acid, have the same temperature of 276 ° C and pressure of 60.2 kg / cm and maintain water in a liquid state and are fed at a rate of 45.3 kg / h TPA in the first zone. Continuous evaporation of the solvent and crystallization of TPA are presented in Table. 5, PRI me R 13. The aqueous solution is fed to the first of eight stirred zones at a rate of 45.3 kg of TPA per hour. The solution is maintained at 276 ° C and a pressure of 60.3 kg / cm so that the water is in a liquid state and contains 20 wt.% TFA with 0.25% para-toluic acid. A total of 76.9 kg was instantly evaporated. The working conditions of each zone, the cumulative percentage of crystallized TPA and the content of para-toluic acid in it are listed in Table. 6. The maximum content of para-toluic acid in the extracted final product of TPA does not exceed 0.015%. However, the product can be extracted from the magma of the first six crystallization stages without degrading the yield with a content of about 0.0089% para-toluyl acid, which is comparable with the product n {1 5, containing 0.0087% para-toluic acid. The product of example 13, due to the temperature gradient for a portion of TPA, crystallized below 182-1bO ° C, compared with the gradient of example 4, is obtained of higher quality (0.053l% versus 0.015% para-toluyl acid) than by the process of example 4.
    Continuation of table 2
    Pere1 | Yeshivaem
    First h
    kg / cm
    Second
    ° С
    kg / cm
    Third
    kg / cm
    Fourth ° C
    kg / cm
    Sixth ° C
    kg / cm
    Paratoluic acid in oil cake,%
    Note. The content of para-toluic acid in the product is 0.0102%.
    143Not applied
    Not applied
    4.7
    4.7
    0,0087
    0.015
    Table 4
    Table 5
    17
    权利要求:
    Claims (1)
    [1]
    869554 Formula of the Invention of Grid Terephthalic Acid Purification from Waco paciBopa, which has an initial temperature in the range of 204-288 ° C, followed by crystallization by cooling the solution in several bonded areas between the crystallization zones, the last of which is 109-149 ° C, 18 Table that, in order to improve the efficiency of the process and the purity of the target product, one of the crystallization zones has a temperature of 160-182 ° C. Sources of information taken into consideration by the expert 1. England patent N 1152575, class C 2 C, i pub. 1969.
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    同族专利:
    公开号 | 公开日
    YU41043B|1986-10-31|
    TR18050A|1976-09-23|
    EG11555A|1977-08-15|
    FR2241529A1|1975-03-21|
    IN142341B|1977-06-25|
    GB1476436A|1977-06-16|
    DE2437846C2|1989-12-28|
    NL7409866A|1975-02-24|
    FR2241529B1|1978-08-11|
    JPS5049248A|1975-05-01|
    JPS5324057B2|1978-07-18|
    DE2437846A1|1975-03-06|
    DD115109A5|1975-09-12|
    CS198150B2|1980-05-30|
    BR7406531D0|1975-06-03|
    IT1018896B|1977-10-20|
    US3931305A|1976-01-06|
    YU224174A|1982-05-31|
    RO66116A|1980-03-15|
    PL100195B1|1978-09-30|
    HU180065B|1983-01-28|
    BG31071A3|1981-10-15|
    BE818228A|1975-01-29|
    ES429400A1|1976-09-01|
    CA1019342A|1977-10-18|
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    申请号 | 申请日 | 专利标题
    US05/389,717|US3931305A|1973-08-20|1973-08-20|Terephthalic acid recovery by continuous flash crystallization|
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