SU536163A1 - Method for preparing naphthalene-2,6-dicarboxylic acid - Google Patents

Description

To prevent moisture from entering the reaction zone, the feedstock is thoroughly dried before loading into the reactor, since in the presence of moisture

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A number of methods are known for binding water released by reaction (2-4). For example, substances that bind water but do not affect the main reaction, in particular carbides, nitrides or bromides of alkali or alkaline earth metals, or alkaline carbonates, are added to the initial mixture of reagents in significant quantities - 50-80 wt. % of the original naphthalene junokarbono; howl Kislota 2.

There is also known a method for preparing 2, .6-naphthalene dicarboxylic acid Disp: roping by drying potassium naphthoate at C-130 ° C (38 h) at C in the presence of a catalyst O | V disP | p | Op; cadmium compounds (CdCla), filter, in an inert gas or carbon dioxide atmosphere at an appropriate pressure with a yield of -72% 3.

However, in connection with the expansion of the production of 2,6-naphthalene dicarboxylic acid, there is a need to develop continuity in the implementation of this process, as well as to reveal all its features to ensure efficiency and high productivity.

To simplify the process, the proposed method (Conducted in a continuous stream of carbon dioxide or inert gas containing 0, .00001-0.1 wt.% Moisture.

This eliminates the need for thorough drying of the feedstock, i.e., the moisture content in it can preferably be 1-4 wt. %

According to research carried out according to the proposed method, for stripping naphthalene. In a continuous process, the amount of carbon dioxide, as compared to the batch process, increases thousands of times, so the moisture content of inert or carbon dioxide begins to play a significant role. Thus, the moisture content in the gas to 1% reduces the yield of the main product (2.6 NDK) by; 50% (see graph).

The implementation of a continuous process with a counter-flow of reagent and carbon dioxide eliminates the need for pre-drying to a constant weight of the original feed, since the feedstock with a very low thermal conductivity gets into the reactor of any design and warms up slowly, i.e. if the zone of low temperatures and at 100-125 ° C loses water, which is carried away from the reactor together with the exhaust gases and does not enter the reaction zone, the decarbonate salt of monocarboxylic acid is decanted to naphthalene (reaction 6), :

+ K2COz CO (6)

high temperatures at which decarboxylation occurs but reaction 6.

The proposed method is that the preformed mixture of the raw material without

the previous drying to a constant weight (such a mixture usually contains 1--4 wt.% moisture) is not heated, and the fish is loaded through the sludge dispensers into a continuous reacting vessel, i. The pressure of the gas and the temperature in the reaction zone are maintained through the engine. A countercurrent to the feedstock to the reactor is continuously fed carbon dioxide or inert gas with a moisture content of not more than 0.1%, which

first passes through the reaction zone, and then through a low temperature zone, in which preliminary heating and supply of the initial raw material occurs, and together with naphthalene and water vapor are continuously removed from the reactor through a throttle valve, by means of which it is regulated and maintains the required pressure in the reactor. The feedstock, passed the reaction zone, in the form of reaction products in the solid state

continuously discharged from the reactor through airlock chambers. The residence time of solid reactants in the reaction zone (30-45 minutes) is regulated by the speed of the transporting devices inside the reactor.

From the solid reaction products, the end product is isolated — 2,6-N.D.C. by known methods, for example, by acidification. The yield of 2,6-NDK 73-74%.

Example 1. A 10 g tableted mixture consisting of 93.2% potassium salt of 2-Na.toic acid, 4.8% cadmium oxide, 2% wlate is loaded into a laboratory reactor, and the reactor is closed from a balloon through a desiccant filled with silica gel, m, carbonate

gas with a pressure of 20 atm and a humidity of 0.88%. With the help of the throttle valve, located after the aftalin H trap, a CO2 flow is created through the reactor at a rate of 0.5-1 l / min. Gas consumption is measured with a gas clock.

The reactor is heated with an electric helix to 430-440 ° C and the reaction can be kept at this temperature for 30-40 minutes. Then the reactor is cooled to

40 C. C. 6.1 g of product is obtained in disproportionation with a content of 2,6-NDK of 58.3%. The output of 2,6-NDK 73,47% of theoretical.

PRI mme R 2. 10 g of the initial mixture consisting of 95% potassium is loaded into the reactor.

salts of 2-naphthoic acid and 5% cadmium oxide. The disproportionation reaction is carried out in the presence of carbon dioxide, the humidity of which is 0.08%. The reactor is heated to 430-440 ° C, (the reaction mixture is kept at this temperature for a minimum. The reactor is cooled and 6.1 g of product are obtained with a content of 2,6-NDC 59.2%. Output 2,6-NDC 74.63% of theoretical.

Claims (3)

1. A method of producing naphthal. N-2,6-dicarboxylic acid by disproportionating a potassium salt of naphthalene monocarboxylic acid or a mixture of this acid with potash in the presence of a catalyst for disproportionation, such as cadmium, at a temperature of 350-500 ° C and pressure in an inert or carbon dioxide atmosphere with the subsequent isolation of the target product, characterized in that, in order to simplify the process, the latter is carried out in a continuous stream of carbon dioxide or inert gas containing 0.00001-0.1 weight. % moisture. 2. A method according to claim 1, characterized in that the process uses a potassium salt of naphthalene monocarboxylic acid containing 1-4% moisture. Sources of information taken into account in the examination: 1. Patent of Germany No. 1247,290, cl. 12, 14, 1967. 2. US patent No. 2823231, cl. 260-515, 1958. 3. Japanese patent number 7737, cl. 16 D 416, 1970 (prototype). ; N.C (YOGS. ° / a)