Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Gas or vapor treating
Patent
1997-10-10
1998-12-29
Straub, Gary P.
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Gas or vapor treating
502 20, 502 34, B01J 2034, B01J 3804, B01J 3830
Patent
active
058541616
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This is the national stage of International Application No. PCT/US96/05688 filed Apr. 24, 1996.
The present invention relates to a process for treating a catalyst used in a process for the preparation of maleic anhydride by oxidizing a hydrocarbon having four carbon atoms in a reactor, particularly in a fluidized bed reactor, when the activity of the catalyst has decreased during use.
BACKGROUND OF THE INVENTION
It has been known that maleic anhydride is prepared by oxidizing a hydrocarbon having four carbon atoms using a vanadium-phosphorus oxide catalyst, often called a V-P-O catalyst, in a fluidized bed reactor. In this process, a problem is that the catalytic activity decreases with time. Then, if the reaction temperature is raised to maintain the same level of conversion, the yield of maleic anhydride decreases. Accordingly, various processes have been tried for the regeneration of the catalyst. For example, the known methods include increasing the valence of the vanadium to 3.9 to 4.6 using sulfur trioxide, by which the catalytic activity is partly regenerated (U.S. Pat. No. 4,123,442); removing inactive vanadium from the catalyst using the action of a halogen or an organic halide (U.S. Pat. No. 4,020,174); treating the catalyst with a reducing gas such as hydrogen, carbon monoxide, etc. (UK Patent No. 1,439,489); bringing the catalyst into contact with aqueous ammonia or an amine (UK Patent No.1,512,305); and adding a phosphorus compound to the catalyst (U.S. Pat. Nos. 3,296,282 and 3,474,041 and UK Patent No. 1,291,354). However, these methods are unsatisfactory. For instance, when a phosphorus compound is added, the selectivity is improved but the activity is reduced requiring a higher reaction temperature.
Japanese Patent Application Laid-Open No. Hei-5-329381 discloses a method where the catalyst particles used in a fluidized bed reactor are de-agglomerated or a method where the surface of the catalyst particles in a fluidized bed reactor is re-exposed, wherein a high speed gas is blown onto the catalyst particles while they are in a fluidized state in a fluidized bed reactor whereby the surface of the particles is polished due to the collision of the particles. In Japanese Patent Application Laid-Open No. Hei-4-316567, a method is disclosed where the catalyst is taken out of a fluidized bed reactor and then crushed to expose the active surface of the catalyst which is then put back into the reactor.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide an improved process for the efficient regeneration of a V-P-O type catalyst to improve conversion, yield and selectivity. The present invention provides a process for improving the activity of a catalyst used in a process for the preparation of maleic anhydride by oxidizing a hydrocarbon having four carbon atoms, wherein the catalyst comprises oxide compounds of vanadium and phosphorus, and wherein at least a part of the catalyst particles are removed from the reactor and a deteriorated and inactive layer on the surface of the catalyst particles is removed by the use of a gas flow which causes collisions between the catalyst particles and usually between the particles and an impact surface with sufficient force to cause the inactive layer to be removed. This may involve the use of a gas stream, such as air, of sufficient force in a pneumatic classifier, the use of a high pressure gas flow jetted from a nozzle in a jet mill to cause collision with a baffle or by subjecting the particles to a high speed gas flow which is jetted into the particles to form a jetted bed whereby the particles collide to polish and remove the inactive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 are photomicrographs which show the structure of several catalyst particles before the present regeneration.
FIG. 4 is a photomicrograph which shows the structure of the catalyst particles after being subjected to regeneration in a pneumatic classifier.
FIG. 5 is a photomicrograph which shows the
REFERENCES:
patent: 2833699 (1958-05-01), Dicks et al.
patent: 5120691 (1992-06-01), Pontier et al.
Asami Masayuki
Hamashima Nagato
Ichiki Tatsumi
Nakamura Teiji
Suzuki Sadakatsu
ABB Lummus Global Inc.
Ghyka Alexander G.
Lonza Societa Per Azioni
Straub Gary P.
Tonen Chemical Corporation
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