Patent RU-2374219-C2 (RU)
Title: Stepped counterflow catalystic oxidation of disubstituted benzene
Inventor: BELMONT FREHNK G
IPC: C07C51/16
Filed: 2004-10-19
Granted: 2009-11-27
Abstract: FIELD: chemistry. ^ SUBSTANCE: invention relates to a continuous stepped counterflow method of catalytic oxidation in a solvent of at least one benzene compound, containing two substituting groups, which are selected from alkyl, hydroxyalkyl, aldehyde, carboxyl groups and their mixtures, which can be oxidised to the corresponding acid derivative, involving the following steps: (a) introducing a mixture of material into the first oxidation step, containing at least part of the total amount of each of: (i) solvent, which is an organic acid, (ii) at least one catalytically active metal, selected from manganese, cobalt, nickel, zirconium, hafnium, cerium and their mixtures, and (iii) bromine in molar ratio, in terms of all catalytically active metals, in the interval from 1:20 to 5:1 and from 7 to 60 wt % of the total amount of at least one disubstituted benzene, introduced at steps (a) and (d); (b) partial oxidation of at least one disubstituted benzene at the first oxidation step in the presence of a gas, containing molecular oxygen initially in amount of 3 to 20 vol. %, at temperature ranging from 121C to 205C and relative quantities of disubstituted benzene, catalytic metal, solvent and bromine, introduced at step (a), so that from 25 to 99.95 wt % disubstituted benzene, added at the first oxidation step, is oxidised with formation of a gaseous mixture, containing unreacted molecular oxygen, evaporated solvent and a first mixture of products, containing acid derivative, partially oxidised disubstituted benzene, unreacted disubstituted benzene and solvent, and at pressure from 8.96105 to 14.8105 Pa, sufficient for keeping disubstituted benzene, partially oxidised disubstituted benzene, acid derivative and solvent in liquid state or in form of a suspension of solid substance in a liquid, so that concentration of residual molecular oxygen in the remaining gaseous mixture ranges from 0.3 to 2 vol. %; (c) extraction of the obtained first product mixture after the first oxidation step and supplying at least part of the extracted first product mixture to the second oxidation step; (d) supplying gas to the second oxidation step, containing molecular oxygen and residue form total amount of disubstituted benzene, catalytic metal, solvent and bromine; (e) oxidation at the second oxidation step of partially oxidised disubstituted benzene and unreacted disubstituted benzene, supplied to the second oxidation step, with a gas containing molecular oxygen in amount of 15 to 50 vol. %, at temperature ranging from 175C to 216C and relative quantities of disubstituted benzene, partially oxidised disubstituted benzene, catalytic metal, solvent and bromine, introduced at step (a), so that from 96 to 100 wt % disubstituted benzene and partially oxidised disubstituted benzene is oxidised with formation of a gaseous mixture, which contains unreacted molecular oxygen, evaporated solvent and a second product mixture, containing acid derivative and solvent, and at pressure from 11.7105 to 16.2105 Pa so as to keep the acid derivative, partially oxidised disubstituted benzene and unreacted disubstituted benzene mainly in liquid state or in form of a suspension of solid substance in a liquid, so that concentration of residual molecular oxygen in the remaining gaseous mixture ranges from 3 to 15 vol. %; (f) extraction after the second oxidation step of the second product mixture, containing acid derivative; and (g) tapping gas which contains residual molecular oxygen after the second oxidation step and returning it to the first oxidation step. ^ EFFECT: method allows for maximum use of oxygen without reducing quality of the desired carboxylic acid using a stepped counterflow oxidation system. ^ 25 cl, 11 tbl, 29 ex, 3 dwg