Catalyst for selective hydrogenation of highly unsaturated hydro

Details Catalyst for selective hydrogenation of highly unsaturated hydro Catalyst for selective hydrogenation of highly unsaturated hydro

1999-04-15

2000-07-04

Griffin, Walter D.

Chemistry of hydrocarbon compounds

Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...

Hydrocarbon is contaminant in desired hydrocarbon

585259, 208143, 208144, 502333, 502339, C10G 4540, B01J 2344, C07C 503

Patent

active

060841400

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
Various olefin compounds used as base material sin petrochemical industries are usually produced by a steam cracking of naphtha. The olefin compounds thus produced contain highly unsaturated hydrocarbon compounds which must be removed from the olefin compounds in order to use them as materials in high molecular weight chemical industries.
The methods for removing the highly unsaturated hydrocarbon compounds include a method comprising selectively reacting these compounds with hydrogen in the presence of a catalyst, a method by means of solvent extraction and the like. The catalyst according to the present invention is applicable to the former method for obtaining high purity of olefin compounds by selective hydrogenation of the highly unsaturated hydrocarbon compounds.
2. Prior Art
It has been known that various kinds of metals have an activity for a hydrogenation reaction of highly unsaturated hydrocarbon compounds. In the case of a hydrogenation reaction carried out in petrochemical industries in order to purify olefin compounds, highly selective catalysts are required for preventing loss of olefins caused by a side reaction through hydrogenation of olefin compounds, and palladium-based catalysts have been used as such a catalyst that satisfies the requirement.
The palladium-based catalysts used in the selective hydrogenation reaction are not only highly selective but also are excellent in its activity. Thus, the reaction is initially carried out at a lower temperature and, when the activity of the catalyst is decreased to lower the reaction efficiency due to deposition of carbonaceous substances onto the surface of the catalyst caused by another side reaction, the reaction temperature is gradually raised while preventing unreacted highly unsaturated hydrocarbon compounds from remaining in the products. When the temperature is raised as high as near the critical temperature at which hydrogenation of olefin compounds are activated, the reaction is interrupted and the catalyst is then regenerated for re-use.
When reactivity of olefin compounds and acetylene compounds in the presence of a palladium catalyst are compared, acetylene compounds have significantly higher reactivity than olefin compounds have. However, since the amount of olefin compounds usually present in a reaction system is much higher than that of acetylene compounds, hydrogenation of the olefin compounds is accompanied by hydrogenation of the acetylene compounds. It is therefore preferably, in view of yield of the compounds of interest, that the catalyst to be used in the reaction is such catalyst that causes hydrogenation of the olefin compounds as a side reaction as less as possible. In addition, deposition of carbonaceous substances on the catalyst occurs due to polymerization of the highly unsaturated compounds as another side reaction, which decreases activity of the catalyst, makes long-term stable operation of the selective hydrogenation reaction difficult, and require increased frequency of a regeneration of the catalyst. Thus it is preferable that the catalyst used therein leads to deposition of the carbonaceous substance as less as possible.
In order to decrease the action of the palladium catalysts on these two kinds of the side reactions, many methods for improving selectivity of the catalysts or their use have been proposed. The methods for improving selectivity by improving the catalysts, which have been known in the art can be roughly classified into two method, one comprising addition of a co-catalyst and the other comprising improvement of a physical property of the catalysts.
As the method for improving selectivity by adding a co-catalyst to a palladium catalyst, for example, European Patent No. 722776 gazette and U.S. Pat. No. 5,489,565 gazette disclose a method for adding silver and an alkaline fluoride to a palladium-alumina catalyst; European Patent No. 689872 gazette discloses a method for preparing a catalyst by adding silver to a palladium-alumina catalyst and then subjecting the resu

REFERENCES:
patent: 4686314 (1987-08-01), Wood et al.

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