Method for preparing catalyst for refining of crude terephthalic acid

Abstract

This is a kind of producing method of catalyst used for refining coarse terephthalic acid (CTA). The catalyst makes grains or molding active carbon as carrier, the content of loading active component metal Pd is 0.2 - 4wt%. It orderly includes: have acid wash to carrier active carbon; wash carrier active carbon with water to neutral; have soakage with watery solution containing nitrite ion to carrier active carbon; dry carrier active carbon to get rid of water; prepare Pd solution with water-soluble Pd compound, a kind of complexing agent and water to infuse or insufflate the carrier active carbon; the content of Pd compound in the Pd solution counted by Pd is 15 - 20wt%; the mol proportion of complexing agent and Pd is (0.01 - 1) : 1, the complexing agent is got from anyone of 8-hydroxyquinoline, 2, 3, 4-trihydroxyl-4-sulfonic azobenzol, o-phenanthroline, o-Aminophenol, o-hydroxybenzoic sodium or o-hydroxybenzaldehyde oxime; after aginged, have deoxidizing treatment with reducing agent to get activator products.

Description

technical field [0001] The invention relates to a preparation method of a supported palladium / carbon catalyst for hydrogenation reaction, in particular to a preparation method of a supported palladium / carbon catalyst for refining crude terephthalic acid through selective hydrogenation reaction. Background technique [0002] The supported palladium / carbon catalyst is mainly used for the selective hydrogenation of unsaturated organic matter, especially for the purification of crude terephthalic acid. Impurities such as p-carboxybenzaldehyde (4-CBA) in crude terephthalic acid are After the hydrogen is transformed into other compounds, it can be separated and purified by crystallization. Because the palladium / carbon catalyst usually adopts a single active component, its improvement research has always focused on the structure of the support and the distribution of metal Pd on the support in the prior art, and this will indeed have a great impact on the performance of the catalys...

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Problems solved by technology

However, because hydrogen peroxide itself is also oxidizing, it can oxidize the surface groups of activated carbon, which will change the surface physical and chemical properties of the support, that is, change the surface group structure of the support, which has a strong uncertain negative impact and will damage the catalyst. Other properties, such as palladium loading strength, catalyst life, selectivity, etc.

U.S. Patent No. 4,476,242 proposes to use organic solvents such as methanol or pyridine to prepare impregnation solutions containing Pd compounds. It is said that this is also very effective in preventing the migration of Pd and grain growth, but the production process uses methanol or pyridine, which is harmful to the human body. Harmful organic compounds are unfavorable in terms of environmental protection or labor protection

In addition, there is a patent report that by adjusting the pH value, the chloropalladium acid solution is converted into a palladium colloid, which is said to prevent the reducing groups on the surface of the activated carbon from directly reducing Pd ions to zero-valent metal Pd, but the colloid has poor stability. It is difficult to distribute evenly on the carrier activated carbon, which will also affect the dispersion of Pd

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