Process for preparing terephthalic acid of high quality
US4877900A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 5, 1988 |
| Grant date | Oct 31, 1989 |
| Priority date | — |
| Expiry date | Apr 5, 2008 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C51/265
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
The present invention provides a process of preparing terephthalic acid of high quality which is characterized by: PA0 oxidizing p-xylene with molecular oxygen in an acetic acid solvent in the presence of a catalyst comprised of at least one heavy metal and bromine at a temperature of from 180.degree. to 230.degree. C. to convert at least 95 wt % of the p-xylene into terephthalic acid and, optionally, subjecting the resultant reaction mixture to low temperature post-oxidation with molecular oxygen at temperatures lower than the temperature of the first oxidation reaction, thereby obtaining a slurry containing terephthalic acid particles whose spectral reflectance defined below is not less than 70% and whose reflectance ratio (400/500) defined below is not less than 0.92; PA0 subjecting the slurry to high temperature post-oxidation with molecular oxygen at a temperature of from 235.degree. to 290.degree. C. and then to crystallization; and PA0 collecting the resultant terephthalic acid from the reaction mixture. Spectral reflectance=a spectral reflectance at 500 nm determined according to a white light illumination method. Reflectance ratio (400/500)=(spectral reflectance at 400 nm)…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.