Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1995-01-23
1998-12-08
Barts, Samuel
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562116, C07C 5116
Patent
active
058472037
DESCRIPTION:
BRIEF SUMMARY
This application was filed under U.S.C. 371 of PCT/GB93/00992 filed May 14, 1993.
This invention relates to the oxidation of substituted aromatic compounds to aromatic carboxylic acids using a catalyst which comprises bromine or a bromine-containing compound. The invention has particular application in the production of terephthalic acid.
Aromatic carboxylic acids such as terephthalic acid have commonly been produced by the oxidation of substituted aromatic compounds such as p-xylene by means of molecular oxygen in a lower aliphatic monocarboxylic acid solvent (preferably having from 2 to 8, and more preferably from 2 to 6, carbon atoms, for example acetic acid) and in the presence of a catalyst comprising one or more heavy metal compounds and bromine or a bromine-containing compound.
It is widely recognised that the chemicals involved in this chemical reaction are particularly corrosive especially under the conditions of temperature and pressure usually employed to realise high yields. This necessarily leads to the extensive use of suitable corrosion resistant materials for construction of the reactor vessel and associated items of plant. Accordingly, expensive titanium and titanium alloys have figured extensively as construction materials in plant for effecting oxidation of for example p-xylene to terephthalic acid especially in circumstances where the oxidation reaction is carried out using a lower aliphatic monocarboxylic acid solvent in the presence of bromine or a bromine-containing compound. Thus, to quote from U.S. Pat. No. 4,330,676 (Column 4, lines 47 to 54): "Where the catalyst contains a bromide a material must be used capable of withstanding the resulting highly corrosive reaction mixture, for example titanium, but in the absence of bromide less expensive materials such as stainless steels are suitable".
With a view to allowing the use of less expensive materials of construction such as stainless steels, proposals have been made from time to time involving modification of the reaction conditions, i.e. the materials employed in the oxidation reaction and/or parameters such as temperature and pressure under which the oxidation reaction is carried out. For instance, U.S. Pat. No. 4,278,810 and GB-A-2094800 disclose processes for the production of terephthalic acid in which bromine is deliberately excluded from the oxidation reaction, water is used as a substitute for acetic acid and the reaction is carried out under relatively low temperature conditions.
According to one aspect of the present invention there is provided plant for the production and processing of an aromatic carboxylic acid (preferably terephthalic acid) wherein the aromatic carboxylic acid is produced by the liquid phase oxidation of a substituted aromatic compound such as paraxylene in an aqueous, lower aliphatic monocarboxylic acid reaction medium in the presence of a catalyst system comprising cobalt, manganese and bromine, characterised in that at least some of those plant components which, in use, are exposed to the reaction medium (especially those exposed at elevated temperatures and pressures in excess of 180.degree. C. and 8 bara respectively) are fabricated from duplex stainless steel.
By duplex steel, we mean a stainless steel composed of ferritic and austenitic phases, usually containing about equal parts of austenite and ferrite.
Components of the plant which are exposed to the reaction medium under the defined conditions include the reactor vessel in which said liquid phase oxidation reaction is carried out and also a first stage crystallisation vessel forming part of a series of crystallisation stages in which controlled crystallisation of the aromatic carboxylic from mother liquor is effected. The conditions prevailing in both of these vessels are particularly severe and, hitherto, it has been necessary to employ titanium and titanium alloys as the materials of construction for these vessels.
Preferably said components are fabricated from a nitrogen alloyed grade of duplex stainless steel having a molybdenum const
REFERENCES:
patent: 4798635 (1989-01-01), Bernhardsson
patent: 5004830 (1991-04-01), Park et al.
patent: 5063023 (1991-11-01), Sridhar
patent: 5145656 (1992-09-01), Gallup et al.
patent: 5238508 (1993-08-01), Yoshitake et al.
Japanese Abstracts JP 5371026, 1978.
Pennington Alan
Smith Robert Francis
Barts Samuel
E. I. Du Pont de Nemours and Company
Krukiel Charles E.
LandOfFree
Bromine catalysed oxidation processes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bromine catalysed oxidation processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bromine catalysed oxidation processes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-179210