Production of liquid ortho-phthalic acid and its conversion to high purity phthalic anhydride
US4215052A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 29, 1979 |
| Grant date | Jul 29, 1980 |
| Priority date | — |
| Expiry date | Aug 29, 1999 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C51/56
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
Phthalic anhydride of commercially acceptable quality can be produced continuously in yields of from about 80 up to about 83 mole percent (% of theoretical) through a combination of steps starting with the neat oxidation of liquid o-xylene with air in the presence of the catalysis provided by cobalt, manganese and bromine. Said oxidation is conducted in two steps wherein the first step is conducted under mild conditions and short residence time to provide a liquid effluent containing 8 to 40 weight percent o-phthalic acid and 6 to 30 weight percent o-xylene and the second step oxidizes such liquid effluent composition under more vigorous conditions including higher reaction temperature and longer residence time until substantially all of the o-xylene and precursors of o-phthalic acid have been converted to o-phthalic acid. Thereafter the second liquid oxidation effluent is subjected to simultaneous rapid dehydration and phthalic anhydride evaporation followed by contact of the resulting mixture of vapors first with a noble metal catalyst to remove bromine contamination and then with a reflux liquid in a fractionation system to remove water as part of a top fraction and provide a li…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.