Method of obtaining alkylaromatic monocarboxylic acids

FIELD: chemistry.

SUBSTANCE: claimed method of obtaining alkylaromatic monocarboxylic acids involves liquid phase oxidation of dialkyl-substituted aromatic hydrocarbons by oxygen-containing gas in the presence of catalyst at high temperature. Alkyltrimethylammonium bromide with alkyl C14-C16 or their mix at 0.3-0.5 wt % of hydrocarbon weight is used as catalyst. Process is performed at 90-120°C until mass ratio of alkylaromatic acid to alkylaromatic aldehyde in the mix reaches 1:1.3-3.0, then alkylaromatic acid is separated, and unreacted hydrocarbon and aldehyde are returned to the process.

EFFECT: possibility to perform mild partial oxidation of dialkyl-substituted aromatic hydrocarbons selectively by one alkyl group without adding transition metals.

2 cl, 8 ex

 

The invention relates to organic chemistry, and in particular to methods of preparation of aromatic acids by oxidation with molecular oxygen to alkyl substituted aromatic hydrocarbons, particularly xylenes and dialkylamino.

Aromatic acids are very important organic compounds and used as raw materials for a wide range of products and materials, such as toluylene acid are used as intermediate compounds in the production of dyes, many medicines, various materials used in optical instruments, and other

A common method of obtaining various aromatic acids in the present time is the liquid-phase oxidation of alkyl substituted aromatic hydrocarbons with molecular oxygen in acetic acid as solvent in the presence of transition metal salts (usually acetates of Co and Mn) at elevated temperature and pressure. For the first time such liquid-phase oxidation of alkylaromatic hydrocarbons was proposed in 1941 (US 2245528, NCI 562/417, MKI SS 63/26, 63/00, 63/06, 63/14, 63/04, 10.06.1941). A huge number of patents on various modifications of this method (see, for example, US 2833816, US 4354037, US 4398037, US 6476257, US 6562997, US 6649791, EN 2128641, EN 2171798). Research in this area continues at the present time.

A significant drawback of this method giacovazzo what about oxidation are hard conditions of the reaction - high temperature and pressure, which leads to complication of the process and increase its intensity, and stimulates the processes of destruction as starting compounds, and the resulting acids.

Source connection upon receipt by the method of liquid-phase oxidation Truelove acids are isomeric xylenes. It should be noted that the selectivity of the oxidation of xylenes by this method is low - Co/Mn-salt and an excellent oxidation catalyst and significantly increasing the speed of the process, you cannot stop the process at the stage of obtaining alkylaromatic monocarboxylic acid and, in addition, contribute to the destruction of the formed acid. The oxidation of xylenes in addition to Truelove acids are dicarboxylic (phthalic) acid, benzoic acid, Truelove aldehydes, Truelove alcohols and other by-products, so the big problem is getting a high-purity Truelove acids (EP 0398282, MKI SS 51/265, 51/44, 51/487, 22.11.1990). In the greatest number of all impurities typically are formed of phthalic acid, for example, p-Truelove acid (p-TC) is usually even get as a by-product of large-tonnage production of terephthalic acid from p-xylene(US 2833816, NCI 562/416, MKI SS 51/265, 51/16, 06.05.1958).

A method of obtaining alkylaromatic monocarboxylic acids (for example, receipt of the p-TC), described in GB 1005315, MKI B01J 23/75, SS 51/265, 51/16, 22.09.1965. The method consists in the oxidation of p-xylene with oxygen or air at a temperature of 200-240°in an autoclave under a pressure of 10 ATM in the presence as catalyst of cobalt oxide in the amount of 1.6 wt.%. The catalyst is insoluble in the hydrocarbon source and remains insoluble in the reaction mixture from the beginning to the end of the oxidation process. The transmission of oxygen or air is terminated by a sharp increase in the oxygen content in the exhaust gas, the autoclave is cooled and after reducing the pressure of the unload of the whole reaction mass. The reaction mass is then heated under reflux to boiling p-xylene and filtered hot. From the filtrate after removal of unreacted p-xylene and p-Truelove alcohol emit p-TC. The precipitate (after hot filtration) is mixed with 10%sodium hydroxide solution and the resulting solution was again filtered. The filter residue remains catalyst of cobalt oxide, it is rinsed from the alkali and return in the process. The alkaline solution is acidified with mineral acid and produce precipitated precipitated terephthalic acid. Xylene is oxidized to acids 93%. Output p-TC on unreacted xylene was 73,9%, the yield of terephthalic acid - 26,1%.

This known method has a high degree of conversion of xylene (93%) run out of luck and the th method of separation of p-Truelove and terephthalic acid, but, like all known methods of liquid-phase oxidation of xylenes in the presence of Co-containing catalysts, accompanied by the formation of terephthalic acid in considerable quantity, and is characterized by a harsh reaction conditions (high temperature and pressure), which complicates the process requires special equipment and increases the energy intensity of production.

A method of obtaining Truelove acids by liquid-phase oxidation with atmospheric oxygen isomer of xylene at 120°in the presence of a complex of cobalt with dicarboxylic cation exchange resin based on a copolymer of styrene with divinylbenzene as a catalyst (in an amount of 2.5 wt.% from xylene). According to GC in the oxidation of p-xylene was observed conversion of p-xylene 40-60%, the yield of (unreacted p-xylene) p-TC was 67-68%, p-Truelove aldehyde (p-TA) is 2-10%, p-Truelove alcohol - 0.3 to 5.5 percent (yield of terephthalic acid was not analyzed); the oxidation of o-xylene (conversion 32%) output on-Truelove acid was 69%, Truelove aldehyde - 2,7%, Truelove alcohol and 5.6% (yield of phthalic acid was not analyzed) (SU 789476, SS 27/12, SS 33/34, SS 63/04, SS 47/52, 23.12.1980).

This method involves carrying out the process in more mild conditions: at atmospheric pressure and a temperature of 120°, but get Truelove KIS is the notes contain all the by-products of the oxidation of xylene, that is quite dirty.

A method of obtaining m-Truelove acid by liquid-phase oxidation of m-xylene with oxygen of air at 118°in the presence as catalyst of naphthenate (in amount of 0.2 wt.%). Conversion of m-xylene 32%, the yield of m-Truelove acid 92-93% (unreacted m-xylene), the rest is isophthalic acid and the products of incomplete oxidation, from which m-Truelove acid purified by recrystallization (SU 666164, SS 63/04, SS 51/16, 05.06.1979; SU 1395625, SS 63/04, 15.05.1988).

The disadvantage of this known method are the low productivity of the process and the pollution of the received m-Truelove acid detachable hard impurities.

Closest to the present invention is a method of obtaining p-TC liquid-phase oxidation of p-xylene with oxygen or air in water as solvent (with the addition of p-TC) in the presence as catalyst of cobalt acetate, or mixtures thereof with cerium acetate or manganese. The reaction is carried out at a temperature of 130-190°and pressure of 5-20 kg/cm2within 5-10 hours the Amount of catalyst 5-160 mmol per 1 mol of p-xylene (1,2-38,4 wt.%). The number of p-TC - 0.1 to 1.5 mmol per 1 mol of p-xylene. The water should be at least 50-80% by weight of the reaction mass. p-TC after cooling, the reaction mixture precipitates, it is filtered and washed with toluene from unreacted XI is Ola. According to gas chromatography by conversion of p-xylene elm), 65-78% output p-TC was 77-90%, of terephthalic acid - 6-17%, p-TA - 2-5%, and other impurities 3.5% (everywhere mol %) (WO 2006103693, MKI SS 51/265, SS 63/04, 05.10.2006 - prototype).

Using the method prototype as solvent water slows down oxidation reaction, which increases the selectivity of the process, but does not completely eliminate the formation of the product of complete oxidation of p-xylene - terephthalic acid, and the resulting p-TC heavily polluted difficult to separate terephthalic acid, moreover, by reducing the rate of oxidation took large amounts of catalyst (examples of 16.7 wt.%). In addition, the disadvantages associated with the hard conditions of the process, is a complex technology and equipment, high energy consumption of the process - inherent in this method.

The present invention is to provide such a method of obtaining alkylaromatic monocarboxylic acids, which, through the use of fundamentally different oxidation catalyst compared to the cobalt containing catalysts, will ensure the complete elimination of the formation of the products of complete oxidation of xylenes or dialkylamino and will allow you to get under mild conditions (atmospheric pressure and a temperature not higher than 120° (C) easily allocated to the target product of the highest number is the notes.

The solution of this problem is achieved by the proposed method of obtaining alkylaromatic monocarboxylic acids by liquid-phase oxidation dialkylamides aromatic hydrocarbons oxygen-containing gas in the presence of a catalyst at elevated temperature, in which the catalyst is used alkyltrimethylammonium bromide with alkyl, C14-C16or their mixture in an amount of 0.3 to 0.5 wt.% by weight of hydrocarbon, the process is carried out at 90-120°With, stop when reaching into the reaction mixture mass ratio alkylaromatic acid:alkylaromatics aldehyde of 1:1,3-3,0, separate alkylaromatic acid, and unreacted hydrocarbon and aldehyde return in the process.

The process is carried out in an environment of oxidized hydrocarbon.

The proposed method was developed on the basis of detailed studies of the processes of oxidation of various hydrocarbons in the presence as catalyst of surface-active substances (surfactants), conducted by the authors of the claimed invention since the early 90-ies (see, for example, an Orphan T.V., Kasaikina O.T. Influence of surfactants on the oxidation of paraffin hydrocarbons // Petrochemicals. 1994, t, No. 5, s; Orphan T.V., Evteeva NM, Kasaikina O.T. Influence of surfactants on the decomposition of hydroperoxides paraffin hydrocarbon /Petrochemical industry. 1996, T.36, No. 2, s; Kartasheva SS, Maksimova T.V. and Dr. who. Influence of surfactants on the oxidation of ethylbenzene // Petrochemicals. 1997, v.37, No.2, p.153;. 1997, v.37, №3, s; Maksimova T.V., Kasaikina O.T. and other Influence of surfactants on the oxidation of ethylbenzene // Petrochemicals. 2001, Vol.41, No. 5, s). It was, in particular, it was found that in the presence of surfactants not only changes the speed of the oxidation of hydrocarbons, but also the composition of the resulting reaction products, i.e. the direction of reaction. The nature of the influence is determined by the structure of the surfactant and the nature of the oxidizable hydrocarbon and is associated with properties of the joint microaggregates surfactants and intermediate oxidation products of hydrocarbons formed in the hydrocarbon environment. Such microaggregate called reversed micelles (they are concentrated polar components of the reaction mixture), and surfactant - catalysts phase transfer.

In recent years, catalytic properties of surfactants are attracted increasing attention (e.g., Csanyi L.J., Jaky K. Liquid-phase oxidation of hydrocarbons in presence of different types of phase-transfer reagents // J. Mol. Cat. A: Chemical. 1997, v.120, p.125 - we investigated the kinetics of oxidation of tetralin, cumene and cyclohexene to hydroperoxides; Holmberg K. Organic reactions in microemulsions // Europ.J. Org. Chem. 2007, v.5, p.731 - the article gives an overview of new catalytic systems with the participation of the surfactants in such organic reactions as reactions to the disclosure of the cycle, the reaction of synthesized and others).

The choice of a specific cationic surfactant for use in the proposed the m way as catalyst, the amount of catalyst, process conditions were determined object of the invention is to provide a high selectivity and sufficient oxidation rate at a relatively low temperature (not higher than 120°C) and atmospheric pressure without the need for additional socialization and promoters. As previously, it was found that in the two-phase system the catalytic activity of cationic surfactants is strongly reduced, the use of water as a solvent was removed, and the reaction was conducted in the environment of oxidizable aromatic hydrocarbon. Dialkyldimethyl aromatic hydrocarbon is first oxidized to alkylaromatic aldehyde intermediate oxidation product, and then to alkylaromatic monocarboxylic acid is the final oxidation product in the proposed method (unreacted hydrocarbon and aldehyde back in the process).

The need to stop the oxidation process when reaching into the reaction mixture mass ratio alkylaromatic acid:alkylaromatics aldehyde of 1:1,3-3,0 due to the peculiarities of crystallization and separation of target product of high purity directly from the reaction mixture.

GLC analysis of the reaction mixture in all the experiments showed the presence of only two oxidation products: alkylaromatic monocarboxylic acid is you and alkylaromatic aldehyde (when the duration of the oxidation of xylenes less hours was also observed traces Truelove alcohol) - dicarboxylic acid was absent.

Examples of a specific implementation of the method.

Example 1.

In a glass reaction vessel equipped with a reflux condenser with an outlet for condensed water and a device for ozonation oxygen-containing gas mixture, downloaded 34 g of p-xylene and 0.13 g (of 0.38 wt.% from xylene) cetyltrimethylammonium bromide - C16H31(CH3)3NBr (CTAB) (Serva), the vessel was placed in a thermostat at 100°and turned the current of air. After 2 hours, the ratio of p-TC:p-TA in the reaction mixture was 1:1,3 (according to GC). The reaction mixture was cooled to room temperature and was filtered crystalline precipitate of p-TC (0.7 g) (p-TC from the reaction mixture can be distinguished also by centrifugation). Then continued oxidation at 100°With mother liquor containing unreacted p-xylene, p-TA and remaining in solution p-TC. In the reaction mixture after a few minutes reappeared a suspension of crystals of p-TC. This means that the catalyst remained in the mother solution, and the oxidation of p-xylene and p-to THE n-TC can be continued. After 4 hours, the transmittance of the air in the mother liquor ratio p-TC:p-TA in the reaction mixture was 1:1,6. The reaction mixture was cooled to room temperature and was filtered crystalline precipitate of p-TC (2.4 g). The analysis of the received crystallize the coy p-TC by ion chromatography (Analytical center of Moscow state University) showed she is chromatographically pure. The total yield of chromatographically pure n-TC 3.1 g (35,9% unreacted p-xylene), the conversion of p-xylene to 20.1%. From the mother liquor after fractionated distillation under reduced pressure unreacted p-xylene and p-TA and washing water from the catalyst allocated 0.7 g of solid n-TC.

Example 2.

The same conditions as in example 1, but as the catalyst used was a mixture of alkyltrimethylammonium bromides, where the alkyl, C14-C16(MATAB) (Korea). After 2 hours, the ratio of p-TC:p-TA in the reaction mixture was 1:1,4. Filtered crystalline p-TC (0.68 g), the oxidation mother liquor was continued (at 100°). After 4 hours the ratio of p-TC:p-TA in the reaction mixture was 1:1,7. The reaction mixture was cooled to room temperature and was filtered crystalline precipitate of p-TC (2.6 g). The total yield of chromatographically pure n-TC 3.28 g (33,3% unreacted p-xylene), the conversion of p-xylene to 22.5%. The mother liquor returned to the stage of oxidation.

Example 3.

In a glass vessel described in example 1 was oxidized by the oxygen of air at 90°C for 6 hours and 43 g of p-xylene in the presence of 0.18 g (0,42 wt.%) MATAB to achieve the ratio of p-TC:p-TA in the reaction mixture 1:3. The reaction mixture was cooled to room temperature and filtered, the precipitated crystal is TC. The output of the chromatographic pure p-TC was 2.7 g (6,3% source xylene), 23% unreacted p-xylene, the conversion of p-xylene was 27.8%. The mother liquor (containing the catalyst, unreacted p-xylene, p-TA and remaining in solution p-TC) returned to the stage of oxidation.

From the above examples 1-3 shows that the oxidation of p-xylene, catalyzed the tetraalkylammonium bromides is selectively one of a methyl group with the formation of p-TC and p-TA. The process claimed to mass ratio of acid:aldehyde provides easy separation of the crystalline chromatographically pure n-TC from the reaction mixture by filtration or by centrifugation. The mother liquor is either returned to the stage oxidation (with the addition of p-xylene), or subjected to fractionated distillation under reduced pressure for separation of p-xylene, p-TA, which is valuable as a chemical product, and an additional quantity of less pure p-TC.

Example 4.

In a glass vessel described in example 1 was oxidized by the oxygen of air at 100°C for 6 hours and 43 g of o-xylene in the presence of was 0.138 g (0.32 wt.%) METAB. The ratio of TC:Oh-in THE reaction mixture 1:2,3. The reaction mixture was cooled in a freezer and filtered 1,43 g o-TC (unreacted o-xylene to 21.5%, the conversion of o-KSIL the La 12,1%). The mother liquor returned to the stage of oxidation.

Example 5.

In a glass vessel described in example 1 was oxidized by the oxygen of air at 100°C for 6 hours and 43 g of m-xylene in the presence of 0,164 g (of 0.38 wt.%) METAB. The ratio of m-TC m-ONE in the reaction mixture of 1:2,5. The reaction mixture was cooled in a freezer and filtered 0.25 g m-TC (unreacted m-xylene 21,3%, the conversion of m-xylene and 2.5%). The mother liquor returned to the stage of oxidation.

The given examples show that the relative ability to oxidation of isomeric xylenes under catalytic action of surfactants increases in the transition from metaisomer to ortho - and parisiorum.

Example 6.

In a glass vessel described in example 1, with bubbling air at 100°C for 6 hours was oxidized to 2 g of 1,2-dimethylnaphthalene (1,2 Naf) in the presence as catalyst 0,0107 g (0.53 wt.%) a mixture of alkyltrimethylammonium bromides METAB. The ratio methylnaphthalene acid:methylnaphthalenes aldehyde in the reaction mixture was 1:1,3. From the reaction mixture was filtered 0,007 g monobasic methylnaphthalene acid (0,35% compared to the original substance). The mother liquor returned to the stage of oxidation.

Example 7.

In the conditions of example 6 was oxidized 1.8 g 1.8-dimethylnaphthalene (1,8 Naf) with 0,0082 g (of 0.45 wt.%) of the catalyst. 1,8-Dimethylnaphthalene at room temperature the e is a solid (TPL 60° (C), the oxidation was carried out in the melt (at 100° (C) to methylnaphtalene acid:methylnaphthalenes aldehyde in the reaction mixture of 1:2. The resulting acid was vongolas from the melt and condense in the upper part of the oxidation vessel. Got 0,0465 g monobasic methylnaphthalene acid (2,6% compared to the original substance). Unreacted hydrocarbon and aldehyde can be used for re-oxidation.

Example 8.

In the conditions of example 6 was oxidized to 1 g of 1,6-dimethylnaphthalene (1,6 Naf) 0,004 grams (0.4 wt.%) of the catalyst. The ratio methylnaphthalene acid:methylnaphthalenes aldehyde in the reaction mixture was 1:2,1. Received by centrifuging the cooled reaction mixture) 0.005 g monobasic methylnaphthalene acid (to 0.65 wt.% in relation to the original substance). Unreacted 1,6 Naf and the aldehyde was used for re-oxidation.

Example 6-8 shows that the oxidation of dimethylnaphthalenes, catalyzed the tetraalkylammonium bromides, also occurs selectively at one of a methyl group with the formation of the corresponding monocarboxylic acids. The relative ability of oxidation of isomeric naftalina can be expressed by the following relation: 1,2 Naf:1,6 Naf:1,8 Naf=1:1,85:7,4.

Thus, the method for obtaining alkylaromatic monocarboxylic acids, is which without additives transition metal is soft partial oxidation dialkylamides aromatic hydrocarbons selectively one alkyl group with the formation of acid and aldehyde, while monocarboxylic acid is the final oxidation product. The process is carried out at moderate temperatures and atmospheric pressure, the desired product is easily detected from the reaction mixture and is of high purity.

1. The method of obtaining alkylaromatic monocarboxylic acids by liquid-phase oxidation dialkylamides aromatic hydrocarbons oxygen-containing gas in the presence of a catalyst at elevated temperature, characterized in that the catalyst used, alkyltrimethylammonium bromide with alkyl, C14-C16or their mixture in an amount of 0.3 to 0.5% by weight of hydrocarbon, the process is carried out at 90-120°With, stop when reaching into the reaction mixture mass ratio alkylaromatic acid: alkylaromatics aldehyde of 1:1,3-3,0, separate alkylaromatic acid, and unreacted hydrocarbon and aldehyde return in the process.

2. The method according to claim 1, characterized in that the process is carried out in an environment of oxidized hydrocarbon.



 

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EFFECT: improved method of synthesis.

20 cl, 2 tbl, 5 ex

FIELD: chemical industry; petrochemical industry; methods of extraction of the unreacted xylene from the acetic acid at production of the terephthalic or isophthalic acid.

SUBSTANCE: the invention is pertaining to the field of production of the terephthalic or isophthalic acid by oxidation of the corresponding alkyl benzene, in particular, to the stage of separation of the reaction mixture including the acetic acid in the capacity of the dissolvent. The method is intended for extraction of the unreacted para-xylene or meta-xylene at the regeneration of the acetic acid using isobutyl acetate as the azeotropic agent for dehydration of the acetic acid. From the azeotropic distillation column at the temperature of 94-100°С separate the fraction containing the para-xylene or meta-xylene, which is fed into the run-down tank, where separate the aqueous phase from the organic phase. In the azeotropic section of the azeotropic distillation column determine the ratio of the para-xylene or meta-xylene and the isobutyl acetate in the stored fraction of the organic phase and periodically remove the accumulated part of the organic phase until the mass ratio of the concentrations of the para-xylene or meta-xylene and the azeotropic agent attains the interval from 0.5 up to 6. As the version of realization of the method route the circulation of the part of the accumulated fraction of the organic phase from the run-down tank to the azeotropic column. The technical result of the invention is upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

EFFECT: the invention ensures the upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

8 cl, 4 tbl, 5 dwg

FIELD: method and composition for selective removal of iron solvent oxide from surface of titanium parts without damaging them.

SUBSTANCE: method comprises steps of adding to distillation tower organic acid such as alkyl mono-carboxylic acid having 2 - 6 C atoms or benzoic acid or their mixture at first temperature range 30 -125°C; passing said organic acid through distillation tower at absence of molecular oxygen; adding to organic acid of first temperature and without molecular oxygen aqueous solution of hydro-halide acid whose temperature is less that said first temperature for preparing aqueous solution of solvent composition at second temperature that is less than first temperature; providing contact of titanium part and solvent composition in distillation tower at absence of molecular oxygen.

EFFECT: possibility for selective removal of iron oxide from surface of titanium parts without damage of said parts.

18 cl, 1 dwg, 6 tbl, 14 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

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a continuous method for preparing highly pure terephthalic acid. Method involves oxidation of p-xylene with oxygen-containing gas in acetic acid medium in the presence of catalyst comprising heavy metal salts, such as cobalt and manganese and halide compounds under increased pressure and temperature up to the definite degree of conversion of para-xylene to terephthalic acid at the first step and the following two-step additional oxidation of prepared reaction mixture and isolation of the end product. Mixing time of reagents is <25 s, oxidation at the first step is carried out at temperature 180-200°C up to conversion degree of p-xylene 95%, not above, oxidation at the second step is carried out at temperature 175-185°C and before feeding to the third step of oxidation the reaction mass is heated to 200-260°C, kept for 8-12 min and oxidized at temperature 180-200°C in the presence of catalyst comprising Ni and/or Zr salts additionally. As halide compounds method involves using XBr or XBr + XCl wherein X is H, Na, Li followed by isolation of solid products of oxidation after the third step and successive treatment with pure acetic acid and water in the mass ratio terephthalic acid : solvent = 1:3. Invention provides intensification of process and to enhance quality of terephthalic acid.

EFFECT: improved method for preparing.

1 tbl, 1 dwg, 14 ex

FIELD: industrial organic synthesis.

SUBSTANCE: aromatic carboxylic acid is obtained via liquid-phase oxygen-mediated oxidation of initial aromatic mix containing benzene bearing two or three oxidizable substituents in its ring or naphthalene bearing at least one oxidizable substituent in its ring in reaction medium containing initial aromatics, promoter, heavy metal-based catalyst, and solvent containing benzoic acid and about 5 to about 60 wt % water, percentage of solvent in reaction medium ranging from 1 to 40 wt %. Oxidation proceeds in reaction zone of double-phase stream reactor under reaction conditions to produce high-pressure emission gas at 160-230°C in first part of reaction zone and at 180-260°C in second part of reaction zone, while at least part of aromatic acid produced crystallizes from reaction medium in reaction zone. According to second embodiment of invention, aromatic carboxylic acid production process comprises (i) providing reaction mixture containing initial aromatic compound, heavy metal-based catalyst, bromine source, and solvent containing benzoic acid and water, initial aromatic compound being benzene bearing two oxidizable alkyl substituents in m- and/or p-positions of its ring or naphthalene bearing oxidizable alkyl substituents in its ring, percentage of solvent in reaction medium ranging from 1 to 40 wt %; (ii) bringing at least part of reaction medium into contact with oxygen-containing gas in first continuously stirred mixing reactor at 160-230°C to form first high-pressure gas stream and product containing crystalline aromatic dicarboxylic acid in liquid medium containing the same, heavy metal-based catalyst, bromine, water, benzoic acid, intermediate oxidation products, and by-products; and (iii) sending thus obtained product to second continuously stirred mixing reactor, wherein second high-pressure gas stream is formed and at least part thereof contacts with oxygen-containing gas at 180 to 260°C to produce aromatic dicarboxylic acid.

EFFECT: minimized toxic methyl bromide formation.

26 cl, 2 dwg

FIELD: organic chemistry of polymers, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing trimellitic acid anhydride. Method for preparing intramolecular trimellitic acid anhydride is carried out by liquid phase oxidation of pseudocumene with air oxygen for a single stage at increased temperature and pressure under conditions of countercurrent of oxygen-containing gas and reaction products in the presence of a catalyst comprising heave metal salts and halide compounds followed by distilling off a solvent and thermal dehydration of mellitic acid up to its intramolecular anhydride. Oxidation of pseudocumene is carried out in reaction volume separated for three zones wherein hydrogen bromide acid is added to each reaction zone by distributed feeding to provide the discrete increase of the HBr concentration up to [HBr] ≥ 0.052% in the first (upper) zone, [HBr] ≤ 0.09% in the middle (second) zone, and [HBr] ≤ 0.111% in the bottom third) zone. The composition of catalyst is maintained as constant in all zones in the ratio of its components in the limit Co : Mn : Ni = (0.28-0.66):1:0.04, respectively, and the process is carried out in the temperature range 160-205°C by its step-by-step increase in zones in the range: 160-180°C in the upper (first) zone, 180-190°C in the middle (second) zone, and 195-205°C in the bottom (third) zone. Invention provides improving the technological process of oxidation of pseudocumene, to improved quality of the end product and to enhance specific output of the reaction volume. Trimellitic acid anhydride is used broadly in preparing high-quality plasticizers, insulating varnishes, high-temperature polyimidoamide coatings and other polymeric materials.

EFFECT: improved preparing method.

2 tbl, 3 dwg, 16 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention elates to a method for preparing pure isophthalic acid. Method involves step-by-step oxidation of m-xylene with oxygen-containing gas in acetic acid medium in the presence of catalyst comprising heavy metal salts and halide compounds under increased pressure and temperature up to the definite degree of conversion of m-xylene to isophthalic acid and the following isolation of the end product. Oxidation of m-xylene is carried out for tree steps at discrete change of temperature by steps to side of decreasing and with the following increasing, or increasing with the following decreasing by the schedule: T1 > T2 < T3 or T1 < T2 > T3 in the temperature range 180-200°C in the presence of manganese-cobalt-bromide catalyst modified with additives of zinc and/or nickel salts in the following ratio of metals Mn : Co : Ni = 1:(0.5-2):(0.005-0.01):(0.005-0.01), respectively, in the total concentration of metals 490 p. p. m. in the reaction mass in the equimolar ratio of the amount of bromine with respect to metals and mixing time of reagents added to the reagents zone <10 s. Then oxidized compound from the 3-d step is subjected for cooling, crystalline isophthalic acid is isolated and treated successively by washing out with acetic acid at temperature 80-100°C in the mass ratio isophthalic acid : CH3COOH = 1:(2-2.5) to remove catalyst and with water at increased temperature 150-230°C in the ratio isophthalic acid : water = 1:(2-3) to remove acetic acid. Then the washed out product is isolated and dried by known procedures to obtain highly pure isophthalic acid. Method provides simplifying the process and to improve quality of isophthalic acid.

EFFECT: improved preparing method.

2 tbl, 1 dwg, 10 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing dimethyl-1,5-naphthalene dicarboxylate that is used in preparing polymers based on thereof and articles made of these polymers. The economic and effective method involves the following stages: (1) dehydrogenation of 1,5-dimethyltetraline to yield 1,5-dimethylnaphthalene; (2) oxidation of 1,5-dimethylnaphthalene prepared at dehydrogenation stage to yield 1,5-naphthalene dicarboxylic acid being without accompanying isomerization stage, and (3) esterification of 1,5-naphthalene dicarboxylic acid prepared at oxidation stage in the presence of methanol to yield the final dimethyl-1,5-naphthalene dicarboxylate.

EFFECT: improved preparing method.

9 cl, 3 dwg, 5 ex

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