PROCESS FOR PRODUCING CRUDE AROMATIC DICARBOXYLIC ACID TO BE FED TO HYDROGENATION PURIFICATION

摘要

FIELD: chemistry.;SUBSTANCE: invention relates to an improved method of producing crude terephthalic acid for use at a hydrogenation purification step via liquid-phase oxidation with an oxygen-containing gas in an oxidation reactor fitted with a mixer, using as the starting material para-xylene in a solvent - acetic acid, in the presence of a metal-containing catalyst which contains cobalt (Co), manganese (Mn) and bromine (Br) as an oxidation promoter, where the oxidation reaction temperature is controlled such that is lies in the interval from 185 to 197°C, average dwell time of the starting mixture in the reactor for liquid-phase oxidation ranges from 0.7 to 1.5 hours, content of water in the reaction solvent is controlled such that it ranges from 8 to 15 wt %, and the composition of the catalyst in the solvent is controlled in a range defined depending on the reaction temperature such that it includes: (1) a catalytically active metal (Co+Mn) in amount of 2650 ppm or less and in amount equal to or more than a value determined by the following relationship: (Co+Mn) = -0.460(t-185)³+18.4(t-185)²-277.5(t-185)+2065, in which (Co+Mn) is the content of (Co+Mn) in ppm, t is the reaction temperature (°C) (temperature range from 185 to 200°C), (2) weight ratio Mn/Co is controlled in a range from 0.2 to 1.5, preferably from 0.2 to 1; (3) content of Br is equal to or less than 1.7, if represented by a value Br/(Co+Mn) in form of weight ratio, and in amount equal to or greater than a value given by the equation: Br/Mn = -0.00115(t-185)³+0.0362(t-185)²-0.5803(t-185)+5.18, in which Br/Mn is weight ratio Br/Mn (wt/wt), and t is reaction temperature (°C) (temperature range from 185 to 200°C), and crude terephthalic acid is obtained with content of 4-carboxybenzaldehyde in amount from 2000 to 3500 ppm as an intermediate product of liquid-phase oxidation. The method provides cheap production of crude terephthalic acid for use in hydrogenation purification and use of a controlled amount of oxidation catalyst, which does not have undesirable effect on the life of a hydrogenation purification catalyst, as well as conditions for carrying out the corresponding reaction.;EFFECT: obtaining terephthalic acid during liquid-phase oxidation of the corresponding dialkylated aromatic hydrocarbon using a solvent, acetic acid, carried out by reducing the oxidised amount of acetic acid lost during oxidation, limiting formation of ash in the obtained terephthalic acid, and enabling control of the composition of the oxidation catalyst depending on reaction temperature.;12 tbl, 7 dwg, 15 ex