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
1995-03-17
1998-04-21
Caldarola, Glenn
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,...
502 27, 502 22, 502319, 502307, B01J 2034, B01J 2300
Patent
active
057417482
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for the removal of fluoride (F.sup.-) from spent chromium-based fluorination catalysts, and to a process for the recovery of hydrated chromium oxide from a spent chromium-based fluorination catalyst including the step of removing fluoride from the spent catalyst. The invention relates in a further aspect to a process for the production of chromium-based fluorination catalysts from deactivated or spent chromium-based fluorination catalysts including the step of removing fluoride from the spent catalyst, and to a process for the production of fluorinated hydrocarbons by the catalysed reaction of halogenated hydrocarbons with hydrogen fluoride in the presence of a fluorination catalyst so produced. The invention relates in particular to a process for the removal of fluoride from a spent chromia, halogenated chromia or chromium oxyfluoride fluorination catalyst, to a process for the recovery of hydrated chromium oxide from a spent chromia, halogenated chromia or chromium oxyfluoride fluorination catalyst including the step of removing fluoride, and to a process for the production of a chromia, halogenated chromia or chromium oxyfluoride fluorination catalyst from the hydrated chromium oxide so recovered.
BACKGROUND OF THE INVENTION
The production of fluorinated hydrocarbons, which may also contain halogen atoms other than fluorine, by the catalysed vapour-phase fluorination of halogenated hydrocarbons with hydrogen fluoride is well known and numerous catalysts have been proposed for use in such a process. Catalysts containing, and typically based on chromium, and in particular chromia, are frequently employed in the known processes. Thus, for example chromia, chromium oxyfluoride or a halogenated chromia may be used in the vapour-phase reaction of trichloroethylene with hydrogen fluoride to produce 1-chloro-2,2,2-trifluoroethane as described in GB Patent 1,307,224 and in the vapour-phase reaction of 1-chloro-2,2,2-trifluoroethane with hydrogen fluoride to produce 1,1,1,2-tetrafluoroethane as described in GB Patent 1,589,924. The same catalyst may be used for the fluorination of chlorodifluoroethylene to 1-chloro-2,2,2-trifluoroethane, for example in a process for the removal of chlorodifluoroethylene impurity from 1,1,1,2-tetrafluoroethane as also described in GB Patent 1,589,924.
A problem with chromium-based fluorination catalysts is that their activity decreases with time whilst they are used in hydrofluorination processes in contact with hydrogen fluoride. One reason for this deactivation is that the catalyst becomes coked due to deposition of carbon upon the surface of the catalyst. Thus it has already been proposed to reactivate or regenerate the catalyst by removing the carbon, for example by contacting the catalyst with air and hydrogen fluoride, as described for example in our co-pending published European Patent Application No. 0 475 693 or air mixed with inert gases, for example nitrogen, or mixtures thereof in order to burn off the carbon. However, such processes provide only short term reactivation for the catalysts and eventually the catalyst is deactivated to such an extent that it may no longer be usefully employed as a catalyst in such hydrofluorination processes. Such reduction in catalyst activity reaches a level at which it is no longer efficient or practical to keep on using the catalyst since the reactant conversion is reduced and attempts to increase the conversion by, for example increasing the temperature etc. lead to by-product formation and unacceptable reductions in product selectivity necessitating increased purification procedures and disposal.
In the past such deactivated or "spent" catalysts, in particular those which are based on chromium, for example chromia, halogenated chromia or chromium oxyfluoride, have been disposed of in land-fill sites.
We have now realised that these deactivated catalysts need not be wastefully disposed of, but may be recycled and we have developed a process for the recovery of chromium-ba
REFERENCES:
patent: 3755477 (1973-08-01), Firth et al.
patent: 4578369 (1986-03-01), Muller et al.
Encyclopedia of Chemical Technology; Four edition; vol. 6; pp. 267-269, 1979.
Encyclopedia of Chemical Technology; Third edition; vol. 6; pp. 87-88, 1993.
Ullmann's Encyclopedia of Industrial Chemistry, 1986.
Ullman's Encyclopedia of Industrial Chemistry, fifth edition Encyclopedia of Chemical Technology, Fourth edition, Kirh-Othmer.
Allen John Graham
Legg Daniel Howard
Caldarola Glenn
Dang Thuan D.
Imperial Chemical Industries plc
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