Catalytic composition, method for manufacturing thereof and method for the purification of terephthalic acid
Patents
| Language: |
Английский |
| Type: |
Patent request |
| Number |
EP 1205241 A1 |
| Request number: |
99964805.8 |
| Request date: |
Dec 9, 1999 |
| patent.field.start_date: |
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| Registration date: |
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| patent.field.request_publication_date: |
May 15, 2002 |
The present invention relates to catalyst compositions for purifying terephthalic acid, based on Group VIII metals, to methods for preparing thereof, and to a method of purifying terephthalic acid suitable for the subsequent synthesis of polyester polymers and copolymers used in the manufacture of textile fibers. The present invention solves the problem of providing selective and stable catalysts and processes wherein crude terephthalic acid with a high initial content of p-carboxybenzaldehyde should be selectively hydrogenated into p-toluic acid or/and decarbonylated into benzoic acid with a low residual content of p-carboxybenzaldehyde. Said problem is solved by using in a method for the purification of terephthalic acid a catalyst composition comprising crystallites of catalytically active palladium or of palladium and at least one metal of Group VIII of the Periodic Table of Elements, applied to the surface of a carbon material, wherein a mesoporous graphite-like material with the average mesopore size in the range of from 40 to 400 ANGSTROM , the proportion of the mesopores in the total pore volume of at least 0.5, and the degree of graphite-similarity of at least 20% is used as the carbon material, in which metal crystallites are distributed in the volume of the carbon material granules in such a manner that the distribution peaks of these crystallites should be at a distance from the outer surface of the granule corresponding to 1-30% of its radius. The catalyst composition comprises crystallites of palladium and rhodium or of palladium and ruthenium, or of palladium and platinum, the total content of the metals varying within 0.1 to 3.0 percent by weight and the weight ratio of palladium to other metals varying within 0.1 to 10.0.