Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Treating with a liquid or treating in a liquid phase,...
Patent
1998-04-21
2000-08-01
Bos, Steven
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Treating with a liquid or treating in a liquid phase,...
549507, 502 24, 502 31, 502 32, 502155, 502164, 203 45, 203 46, B01J 2034, B01J 3848, B01J 3868, B01J 3856, B01J 3854
Patent
active
060966734
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a process for the separation of oligomers of vinyl oxirane from an isomerization catalyst, in order to recover the catalyst for the isomerization of vinyl oxirane to 2,5-dihydrofuran, essentially comprising an onium iodide, a halide of zinc, tin, cobalt, or bismuth, and optionally a donor ligand, the catalyst contaminated with oligomers being mixed with a non-polar hydrocarbon extracting agent or chlorinated hydrocarbon extracting agent, the phases formed being separated and the extracting agent then being removed, by distillation, from the phase containing the catalyst. The catalyst can then be recycled to the isomerization reaction.
The isomerization of vinyl oxirane to 2,5-dihydrofuran is described in numerous patent specifications, eg U.S. Pat. No. 5,082,956, EP 0,412,366, WO 93/10111, and DE-A 4,424,219.
During isomerization, oligomeric by-products are formed which accumulate in the reaction mixture when the product dihydrofuran is continuously separated. It is therefore necessary to remove part of the catalystloligomer mixture in order not to exceed a specified maximum concentration of oligomers in the reaction mixture. Since the catalyst removed cannot be discarded for economical reasons, it must be recovered from the mixture removed in a form making it possible to recycle it to the isomerization phase without loss of activity.
With this aim in view U.S. Pat. No. 5,238,889 describes the separation of oligomeric byproducts formed during isomerization of vinyl oxirane to 2,5-dihydrofuran catalyzed using tetraalkylphosphonium iodides and triphenyltin iodide or tri-n-octyltin iodide, by the addition of a non-polar solvent, separation of the oligomeric byproducts undissolved in the solvent as second phase and removal by distillation of the solvent.
A drawback of combining the isomerization with separation of byproducts as described in U.S. Pat. No. 5,238,889, on an industrial scale, is the use of the said expensive organotin iodides, which are not available in gross quantities, as catalyst components.
Another disadvantage is that organotin halides are readily decomposed by water or other protic reactants. Thus there is the danger of traces of water in the vinyl oxirane used for the isomerization leading to deactivation of the catalyst as a result of the reactions: ##STR1##
Two equivalents of the organotin iodide are here converted by one equivalent of water to form a catalytically inactive organotin' oxide.
As little as 0.,1% of water in the vinyl oxirane used for the isomerization involves the risk of economically unacceptable losses of organotin compound.
Other suitable Lewis acids for the isomerization of vinyl oxirane to 2,5-dihydrofuran are zinc halides (EP 412,366 and WO 93/10111), which are available in industrial quantities at low cost. When use is made of the process described irk U.S. Pat. No. 5,238,889 for the deposition of 6ligomeric by-products by the addition of a non-polar solvent to a catalyst mixture comprising an onium iodide and zinc chloride, bromide, or iodide it would be expected that the zinc halide would accumulate in the polar oligomer phase on account of its salt-like properties, particularly in consideration of the fact that zinc halides do not dissolve in hydrocarbons. Surprisingly the very reverse is true:
The zinc salt is concentrated together with the onium iodide in the non-polar phase, so that the oligomers can be depleted with out appreciable losses of catalyst.
Accordingly, the invention relates to a process for the separation of a catalyst from a mixture containing oligomers of vinyl oxirane, as is formed during isomerization to 2,5-dihydrofuran and from which virtually all of the low boilers have been removed, by distillation, in which the mixture of the oligomers with a catalyst, consisting essentially of or iodide of cobalt, bismuth, tin or zinc and containing from 5 to 14 carbon atoms, phases and
The separating process can be carried out continuously or batchwise and integrated in the isomerization process. The isomerization of
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BASF - Aktiengesellschaft
Bos Steven
Shurtleff John H.
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