Chemistry of hydrocarbon compounds – Aromatic compound synthesis – Having alkenyl moiety – e.g. – styrene – etc.
Reexamination Certificate
1999-11-04
2001-04-24
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
Having alkenyl moiety, e.g., styrene, etc.
C585S445000, C502S338000, C502S344000, C502S330000
Reexamination Certificate
active
06222085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, to a method for producing it, and to a method of using it for producing vinyl-aromatic hydrocarbons.
2. Description of the Related Art
Heretofore, vinyl-aromatic hydrocarbons such as styrene have been produced through dehydrogenation of alkyl-aromatic hydrocarbons in the presence of a catalyst, for which generally used is an iron oxide-type catalyst as the catalyst (catalyst for dehydrogenation).
Up to now, various attempts have been made for improving the capabilities of the catalyst for dehydrogenation, for example, by adding thereto various catalyst components thereby to enhance the dehydrogenation activity of the catalyst and to prolong the life thereof. In addition, known are methods of pre-treating the catalyst for improving its capabilities.
Regarding these, we, the present applicant have disclosed a catalyst for dehydrogenation in Japanese Patent Laid-Open No. 178340/1995, which is produced by reducing an iron oxide-type catalyst that comprises iron oxide and potassium oxide added thereto, with hydrogen at a temperature falling between 350 and 600° C.
The catalyst is favorable to production of vinyl-aromatic hydrocarbons, as its initial activity is high and its life is long. However, it has become known that the catalyst generates heat when exposed to air and therefore must be carefully handled so as to evade its exposure to air when filled into reactors.
The present invention is to solve the problems in the related art as above, and its object is to provide a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, which has high activity and good selectivity for the intended dehydrogenation and has a long life and which can be handled with no difficulty, and also to provide a method for producing it.
Another object of the invention is to provide a method of using the catalyst for producing vinyl-aromatic compounds, in which the catalyst exhibits high activity and good selectivity while maintaining its capabilities for a long period of time and can be handled with no difficulty.
SUMMARY OF THE INVENTION
We, the present inventors have assiduously studied so as to solve the problems in the related art as above. As a result, we have found that a catalyst to be prepared by reducing a potassium component-containing iron oxide composition with hydrogen at a relatively low temperature followed by oxidizing it with a vapor that contains oxygen molecules has extremely good capabilities for dehydrogenation of alkyl-aromatic hydrocarbons, that the life of the catalyst is extremely long, and that the catalyst is stable in oxygen-containing vapors such as air. On the basis of these findings, we have completed the present invention.
Specifically, the gist of the invention is summarized as follows:
(1) A catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, which is a solid catalyst containing a potassium component and an iron oxide component and which is characterized in that the ratio of the pore volume of pores therein having a diameter of from 20 to 100 nm to that of pores therein having a diameter of up to 100 nm falls between 0.7/1 and 0.9/1 and that the catalyst is stable to oxygen.
(2) A method for producing a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons, which comprises reducing a potassium component-containing iron oxide composition with hydrogen at a temperature falling between 350 and 600° C., followed by oxidizing it with a vapor that contains oxygen molecules at a temperature falling between 250 and 500° C.
(3) The method for producing a catalyst for dehydrogenation of alkyl-aromatic hydrocarbons as in above (2), wherein the oxygen molecules-containing vapor is air.
(4) A method for producing vinyl-aromatic hydrocarbons by dehydrogenating alkyl-aromatic hydrocarbons in the presence of a catalyst, in which is used the catalyst of above (1), or the catalyst as produced according to the method of above (2) or (3).
REFERENCES:
patent: 5824831 (1998-10-01), Shiraki et al.
patent: 0086100 (1995-07-01), None
patent: 07178340A (1995-07-01), None
Honjo Fumitaka
Kawamura Kichinari
Shiraki Yasushi
Dang Thuvan D.
Griffin Walter D.
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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