METHOD FOR PREPARING INTRAMOLECULAR TRIMELLITIC ACID ANHYDRIDE Russian patent published in 2005 - IPC

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