METHOD FOR PREPARING ISOPHTHALIC ACID OF HIGH PURITY DEGREE Russian patent published in 2005 - IPC

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