Claims
- 1. A chemical compound which, when dry, corresponds to formula (I):
- (EO.sub.4 M).(Imp)p (I)
- wherein
- E is selected from phosphorus, arsenic, antimony and bismuth;
- M is a metal or a mixture of metals such that:
- M=.alpha.M.sub.1.sup.+ +.beta.M.sub.2.sup.++ +.gamma.M.sub.3.sup.3+ +.delta.M.sub.4.sup.4+
- with the relationship .alpha.=2.beta.+3.gamma.+4.delta.=3;
- wherein M.sub.1 is selected from lithium, sodium, potassium, rubidium, cesium, francium and mixtures thereof;
- M.sub.2 is selected from divalent transition elements, alkaline earth metals and mixtures thereof;
- M.sub.3 is selected from trivalent transition elements, boron, aluminum, gallium, indium, thallium, the elements having an electron sub-shell f, and mixtures thereof;
- M.sub.4 is selected from tetravalent rare earths, titanium, hafnium, tin, germanium and silicon;
- .alpha. is a coefficient between 0 and 3;
- .beta. is a coefficient between 0 and 3/2;
- .gamma. is a coefficient between 0 and 1;
- .delta. is a coefficient between 0 and 3/4;
- Imp is different from EO.sub.4 M and corresponds to a basic impregnating compound selected from alkaline earth metals, alkali metals and mixtures thereof combined with a counter-anion to ensure electrical neutrality;
- the coefficient p is between 10.sup.-2 and 1/3; and .alpha.+p is less than or equal to 3.3 and greater than or equal to 10.sup.-2.
- 2. The chemical compound as claimed in claim 1, wherein E is phosphorus.
- 3. The chemical compound as claimed in claim 1, wherein the coefficient p is between 1/2.times.10.sup.-1 and 1/4.
- 4. The chemical compound as claimed in claim 1, wherein .alpha. is a coefficient from greater than 0.01 to 3.
- 5. The chemical compound as claimed in claim 1, wherein .beta. is a coefficient between 0 and 1/3.
- 6. The chemical compound as claimed in claim 1, wherein .gamma. is a coefficient between 1/3 and 1.
- 7. The chemical compound as claimed in claim 1, wherein .delta. is a coefficient between 0 and 1/3.
- 8. The chemical compound as claimed in claim 1, wherein .alpha. +p is between 0.05 and 1.
- 9. The chemical compound as claimed in claim 8, wherein .alpha. +p is between 0.05 and 1/2.
- 10. The chemical compound as claimed in claim 1, wherein M.sub.2 is selected from calcium, strontium, barium, and mixtures thereof.
- 11. The chemical compound as claimed in claim 1, wherein M.sub.3 is selected from metals having an electron sub-shell f, and mixtures thereof.
- 12. The chemical compound as claimed in claim 1 wherein M.sub.1 is selected from potassium, sodium, rubidium, cesium and mixtures thereof.
- 13. The chemical compound as claimed in claim 1 wherein M.sub.1 is selected cesium.
- 14. The chemical compound as claimed in claim 11, wherein said metal M.sub.3 is selected from yttrium, rare earths, and mixtures thereof.
- 15. The chemical compound as claimed in claim 14, wherein said rare earths are selected from lanthanum and lanthanides.
- 16. The chemical compound as claimed in claim 1, wherein the mixtures thereof.
- 17. The chemical compound as claimed in claim 16, wherein the alkali metal is cesium.
- 18. The chemical compound as claimed in claim 1, wherein said counter-anion is selected from an OH.sup.- ion, or a mixture containing OH.sup.- ion.
- 19. A catalyst for the solvolysis or dehydrohalogenation of a halogenated compound, which comprises at least partially of a chemical compound which, when dry, corresponds to formula (I):
- (EO.sub.4 M).(Imp)p (I)
- wherein
- E is selected from phosphorus, arsenic, antimony and bismuth;
- M is a metal or a mixture of metals such that:
- M=.alpha.M.sub.1.sup.+ +.beta.M.sub.2.sup.++ +.gamma.M.sub.3.sup.3+ +.delta.M.sub.4.sup.4+
- with the relationship .alpha.=2.beta.+3.gamma.+4.delta.=3;
- wherein M.sub.1 is selected from lithium, sodium, potassium, rubidium, cesium, francium and mixtures thereof;
- M.sub.2 is selected from divalent transition elements, alkaline earth metals and mixtures thereof;
- M.sub.3 is selected from trivalent transition elements, boron, aluminum, gallium, indium, thallium, the elements having an electron sub-shell f, and mixtures thereof;
- M.sub.4 is selected from tetravalent rare earths, titanium, hafnium, tin, germanium and silicon;
- .alpha. is a coefficient between 0 and 3;
- .beta. is a coefficient between 0 and 3/2;
- .gamma. is a coefficient between 0 and 1;
- .delta. is a coefficient between 0 and .delta.;
- Imp may be the same as or different from EO.sub.4 M and corresponds to a basic impregnating compound selected from alkaline earth metals, alkali metals and mixtures thereof combined with a counter-anion to ensure electrical neutrality;
- the coefficient p is between 10.sup.-2 and 1/3;
- and .alpha.+p is less than or equal to 3.3 and greater than or equal to 10.sup.-2.
- 20. The catalyst as claimed in claim 19, wherein said compound (I) is predominantly at the surface of said catalyst.
- 21. The catalyst as claimed in claim 20, wherein the remainder of said catalyst is produced from compounds selected from phosphates, hydrogen phosphates and compounds of the formula (II).
- EO.sub.4 M.
- 22. The catalyst as claimed in claim 19, wherein the catalyst consists entirely of said compound (I).
- 23. A process for the production of a catalyst as claimed in claim 19, which comprises the steps of:
- a) synthesizing a compound of formula (II), EO.sub.4 M; then;
- b) introducing an impregnating compound Imp as defined in claim 19 into the reaction mixture;
- c) separating any residual liquid from the reaction solid; and
- d) drying and calcining the solid at a temperature greater than 100.degree. C. to obtain the catalyst as claimed in claim 19.
- 24. A process for the synthesis of a compound as claimed in claim 1 which comprises the step of carrying out said synthesis of the compound in the presence of an alkali metal and a counteranion ensuring electrical neutrality.
- 25. The chemical compound as claimed in claim 1, wherein .alpha. is a coefficient from greater than 0.01 to 0.5.
- 26. The chemical compound as claimed in claim 1, wherein .alpha. is a coefficient between 0.05 and 0.2.
- 27. The chemical compound as claimed in claim 1, wherein the alkali metal is lithium.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 90 01264 |
Feb 1990 |
FRX |
|
Chemical Compounds for use as Catalysts and Process of Making
This application is a Continuation-In-Part of Ser. No. 547,079 filed Jul. 5, 1990, presently pending, which is a Continuation-In-Part of Ser. No. 07/388,936 filed Aug. 3, 1989, now U.S. Pat. No. 4,950,811. These applications are hereby incorporated by reference.
The present invention relates to new chemical compounds which can be used as catalysts for reactions such as the solvolysis of an alkyl halide, especially when the carbon carrying a halogen is in the vicinity of an attracting group or groups, such as the trifluoromethyl group.
The present invention also relates to new chemical compounds which can be used as catalysts for reactions such as dehydrohalogenation of alkyl halides.
The present invention further relates to a process for the solvolysis, preferably gas phase solvolysis, of an organic halide. For example, the invention relates to the preparation of trifluoroethanol by hydrolysis, in the gas phase, from 2,2,2-trifluoroethyl chloride.
There have been many difficulties in the conversion of 2,2,2-trifluoroethyl chloride to the corresponding alcohol by solvolysis wherein water is the solvent (hydrolysis). 2,2,2-trifluoroethyl chloride is an example of the alkyl halides for which solvolysis is ordinarily difficult.
2,2,2-trifluoroethanol (TFE) is a trifluorinated alcohol possessing very good thermal stability, which makes it suitable for a number of applications, in particular in the synthesis of fluorinated anesthetics, in pharmacology in general, and as a solvent.
The preparation of this alcohol either by hydrogenation of trifluoroacetic acid or its esters, or by hydrolysis of 2,2,2-trifluoroethyl acetate, in liquid phase in a solvent having hydroxyl groups, has been described in the prior art.
These various processes for the preparation of TFE are not research has been undertaken in order to find out if it would be possible to carry out a direct hydrolysis, in the gas phase, of 1-chloro-2,2,2-trifluoroethane.
Unpublished French application number 88/10,813 which corresponds to U.S. Ser. No. 07/388,936 by the Applicants, now U.S. Pat. No. 4,950,811, constitutes a significant advance. The process for the preparation of trifluoroethanol by hydrolysis of trifluorochloro-ethane, according to the French application, comprises contacting a mixture of 1-chloro-2,2,2-trifluoroethane and water with a solid catalyst comprising at least one phosphate, or hydrophosphate, or one oxide of a di- or trivalent metal, at a temperature greater than 350.degree. C. and preferably between 400 and 500.degree. C. Hydrolysis is a type of solvolysis wherein water is used as the solvent. The success of the hydrolysis in this application is surprising because it is known to those skilled in the art that the electro-attractive power of the CF.sub.3 group of the 1-chloro-2,2,2-trifluoroethane molecule reduces, or at least renders difficult, the possibility of attacking, with a nucleophilic compound, the carbon atom which is linked to the chlorine of this molecule.
It is an object of the present invention to provide catalysts which introduce a better selectivity and good yields in the above solvolysis processes. chemical compounds which, when used as catalysts, lead to good selectivity and to good yields during reactions such as that of solvolysis, for example hydrolysis, of alkyl halide(s).
Another object of the present invention is to provide a process for the production of such chemical compounds.
Another object of the present invention is the reaction such as that of a solvolysis, for example hydrolysis, of alkyl halides using the above-mentioned catalysts.
Another objective of the present invention is to provide chemical compounds which can be used as catalysts in dehydrohalogenation reactions.
Another object of the present invention is to prepare trifluoroethanol by hydrolysis, in the gas phase, of chloro-trifluoroethane.
These objects and others which will become apparent below.
Chemical compounds useful as catalysts have, when dry, the formula:
M is a metal or a mixture of metals such that:
M.sub.1 is selected from lithium, sodium, potassium, rubidium, cesium, francium and mixtures thereof, and is preferably one of the alkali metals. Preferred among the alkali metals are potassium, rubidium, cesium and mixtures thereof. More preferred are potassium, cesium and mixtures thereof.
M.sub.2 is selected from the divalent transition elements, and alkaline earth metals and mixtures thereof. The transition elements can include zinc and cadmium. Preferably, M.sub.2 consists predominately or totally of alkaline earth metal(s). The preferred alkaline earth metals are calcium, strontium and barium mixtures thereof and mixtures containing them.
M.sub.3 is selected from the trivalent transition elements, boron, aluminum, gallium, indium, thallium, the elements having an f electron subshell and the like, and mixtures thereof. Preferably M.sub.3 consists predominantly or totally of elements having a subshell f. Preferred metals containing a sub-shell f are atrium and rare earth metals, such as, lanthanum, and lanthanides, preferably lanthanum, mixtures thereof and mixtures containing them.
M.sub.4 is selected from the tetravalent rare earths, titanium, hafnium and tin. M.sub.4 can also be germanium or silicon.
.alpha. is a coefficient between 0 and 3, preferably from greater than 0.01 to 3, more preferably from greater than 0.01 to not more than 0.5, and most preferably between 0.05 and 0.2.
.beta. is a coefficient between 0 and 3/2 and preferably between 0 and 1/3 or 1.+-.0.1.
.gamma. is a coefficient between 0 and 1, preferably from at least 1/3 to 1, and more preferably 1/2.
.delta. is a coefficient between 0 and 3/4, preferably between 0 and 1/3 and more preferably between 0 and 1/6.
Imp corresponds to an impregnating compound selected from metal selected from alkaline earth metals, alkali metals and mixtures thereof, such as discussed above, and preferably, potassium, rubidium, sodium, cesium and mixtures thereof and more preferably cesium. Lithium is preferable for dehydrohalogenation. The metals are combined with a counter-anion to ensure electrical neutrality.
Imp is preferably different from impregnant MEO.sub.4, especially when the impregnant is an alkaline earth metal compound. The impregnant may be described as basic because, in the majority of cases, the impregnant is a proton-acceptor, particularly after having been conditioned at a temperature close to that of the solvolysis reaction.
The initial counteranion(s), i.e. before thermal conditioning, is (are) preferably selected from halides, preferably fluoride, and mixtures containing the halides, OH.sup.- and mixtures containing OH.sup.-, preferably mixtures containing predominately OH.sup.-, and derivatives of the EO.sub.4.sup.3- class such as phosphates and hydrogen phosphates and those which become these after pyrolysis, such as, for example, phospho- or phosphinate, and mixtures of such derivatives. Some examples of phosphates are dihydrogeno phosphate, monohydrogeno phosphate, trianionic phosphate (PO.sub.4.sup.3-).
Furthermore, the initial counteranion(s) can be selected from volatile or decomposable anions such as carbonate(s), nitrate, sulfate(s), carboxylates and sulfonates which can be decomposed under the conditions of the reaction, e.g. solvolysis, or thermal conditioning. The anions that are either obtained under these conditions (e.g. oxygenated anions such as O.sup.-2 or OH.sup.-, or those, such as halides, that are part of the reaction phase which are substituted to the initial anion or the oxygenated anions) or that remain unchanged provide for good catalysts.
It has been discovered that the best catalysts are those in which the impregnation is carried out on a matrix (MEO.sub.4) which has a structure containing holes (pores), preferably channels. The size (diameter) of the holes is preferably between 0.2 and 0.5 nm, structure of the matrix may be of a hexagonal type, a monoclinic type or other types.
Especially when 7 is higher than 1/2, preferably higher than 2/3, the best catalysts for the solvolysis reactions are those whose matrix (ME04) is of hexagonal or monoclinic structure, preferably those whose matrix has, at least at low temperature, a hexagonal structure (that is to say with a C.sub.6 symmetry axis parallel to the zeolitic channels, the system of channels being one-dimensional and not interconnected, structural defects being, of course, not taken into account). More preferably it has been shown that the best catalysts are those in which the impregnation is carried out on a matrix which has at least partially a structure of a hexagonal type. However, direct impregnation of monoclinic structures also provide good catalysts.
Finally, it is also preferable that, on heating, the hexagonal structure of the matrix should be capable of being converted into a monoclinic structure. Further that, after impregnation, the compound according to the invention should be subjected to conditions which ensure the hexagonal-monoclinic conversion.
Although this explanation should not be taken to imply any limit, it would appear that the good catalytic power observed in the case of the hexagonal structures might be correlated with the filling of the channels, or holes, of the hexagonal structure with the alkali-metal or alkaline-earth metal material and that this is so even though no detectable trace remains when the hexagonal structure is investigated by the usual means.
The selectivity of the reaction is also dependent on the alkali-metal or alkaline-earth metal material. The higher the ranking of the period to which it belongs, the more the solvolysis reaction is promoted; on the other hand, the lower the ranking, the more the dehydrohalogenation reaction is promoted.
In general, the compounds according to the invention which give mediocre selectivities in solvolysis give results of opposite quality in dehydrohalogenation. In other words, everything takes place as if the substrates had the choice between the two main possible routes (solvolysis or dehydrohalogenation) and as if by choosing the catalysts (according to the above directing principles) it was possible to promote either of the reactions.
The coefficient p represents the ratio between the impregnating compound expressed in gram equivalent and the impregnated compound (EO.sub.4 M) expressed in mole. The coefficient p is between 10.sup.-2 and 1/3, preferably between 0.05 and 1/4 and more preferably between 1/2.times.10.sup.-1 and 1/5.
Moreover, .alpha.+p is less than or equal to 3.3 and greater than or equal to 10.sup.-2, preferably between 0.05 and 1 and more preferably between 0.05 and 1/2.
These compounds can be produced by impregnating a compound to the formula:
The process for the synthesis of a compound of formula I comprises,
General techniques for the production of phosphates are discussed in Pascal P., Nouveau Traite De Chimie Minerale, Vol. X: 821-823 (1956), and Gmelins Handbuch Der Anorganischen Chemie (8th ed.), Vol. 16 (C): 202-206 (1965), wherein two main routes for access to the phosphates can be distinguished. One technique is the precipitation of a soluble salt of the metal (chloride, nitrate) by ammonium hydrogen phosphate and a finishing treatment with ammonia followed by completion of the neutralization. Another technique is the reaction of the metal oxide with phosphoric acid under hot conditions and a finishing treatment with an alkali metal hydroxide.
Within the framework of the present invention, the second procedure enables the cation of the hydroxide employed in the finishing phase to be introduced and impregnated into the final product (I).
According to the present invention, these chemical compounds, (EO.sub.4 M) (Imp).sub.p, can be used as catalysts for the solvolysis of a halogenated compound. Further, these catalysts may be used for dehydrohalogenation. The catalysts according to the present invention can be catalytic bodies the surfaces of which will be formed at least in part by a chemical compound (I) according to produced entirely of chemical compounds (I).
It has been found, surprisingly, that the first few minutes and up to ten minutes generally give less than optimum results with regard to the selectivity of the solvolysis. It is generally only after the catalyst has been modified by the passage of the reactants for a period which can vary from ten minutes up to 2 hours under the solvolysis conditions that the catalyst will play its role of selective catalyst to the full.
The catalyst or catalytic body can be of any shape known per se for solid catalysts which can be used in the gas phase.
The remainder of a catalytic body, that is the part which mixture, can be of any material or materials provided that it is inert under the conditions of use. For reasons of ease of production, the remainder can be made of compounds selected from phosphates, hydrogen phosphates and mixture thereof. The specific surface-area of the pure catalysts or catalytic body, ranges from at least 1 m.sup.2 /g, preferably at least 10 m.sup.2 /g and most preferably between 10 and 100 m.sup.2 /g.
The present invention also relates to a solvolysis process using the above catalysts. This process relates more particularly to the alkyl halides in which the alkyl term corresponds to the definition given in the chemical dictionary "Presse Scientifique, Paris VI, 1959" (Ed. Duval). As described below, the alkyl halide is reacted with a solvent-reactant.
Preferably, the alkyl radical corresponding to the alkyl halide has one or more of the following characteristics:
The alkyl halide preferably has the formula:
R in formula (III) preferably represents a fluorinated or perfluorinated alkyl or a halogen. The R group is such that the boiling point is at a pressure of 10.sup.4 Pa, preferably at a pressure of 10.sup.5 Pa, at most equal to the reaction temperature. Preferably R contains at most 50 carbon atoms, preferably at most 25 carbon atoms and more preferably at most 10 carbon atoms.
In the same formula (III), each X preferably represents a fluorine atom. The remaining halogen, Y, preferably represents chlorine for economic reasons, or fluorine, which is very selective, although not very efficient, for the solvolysis
The solvolysis reaction preferably takes place in the gas phase. The solvolysis temperature is preferably between about 200 and 800.degree. C., and more preferably between about 400 and 600.degree. C.
Although carrying out the reaction at pressures of atmospheric pressure or lower can be envisaged, it has been found, surprisingly, that it is preferably worthwhile to operate at a pressure higher than normal pressure, i.e., between about 1 and 100 atmospheres (10.sup.5 to 10.sup.7 Pa) and more preferably from about 1 to 20 atmospheres (10.sup.5 to 2.times.10.sup.8 Pa).
The molar ratio between solvent-reactant and substrate (alkyl halide) is between 1:1 and 100:1 and preferably between 2:1 and 10:1.
To obtain good results, the catalytic flow rate, expressed in grams of substrate per gram of catalyst (per hour), is between 0.05:1 and 10:1 h.sup.-1 and preferably between 0.5:1 and 5:1 h.sup.-1.
The apparent density of the catalyst is preferably between 0.3 and 2 and more preferably between 0.8 and 1.5.
A carrier gas is optional and is usually a gas, or a mixture of gases, which is not reactive under the operating conditions (for example N.sub.2, air, H.sub.2, He and the rare gases; N.sub.2 and H.sub.2 are preferred). The ratio by volume with the substrate varies from 10.sup.-2 :1 to 50:1, preferably 0.5:1 to 30:1 and more preferably 0.5:1 to 10:.
The solvent-reactant preferably has a pressure at the temperature of the reaction of at least 10.sup.5 Pa, preferably 10.sup.6 Pa. The solvent-reactant used for the solvolysis is preferably a protic polar nucleophilic solvent which does not give rise to a significant parasitic reaction under the operating conditions.
Solvent-reactants giving the best results include primary or secondary amines, including anilines, and alcohols, including phenols. Water also gives particularly good results.
When a dehydrogenation reaction is desired, it is preferable to reduce the solvent or use no solvent at all. If a solvent is used, the solvent is preferably water.
The following non-limiting examples illustrate the invention..
US Referenced Citations (6)
Foreign Referenced Citations (3)
| Number |
Date |
Country |
| 0228898 |
Jul 1987 |
EPX |
| 2192083 |
Feb 1974 |
FRX |
| 474452 |
Jun 1969 |
CHX |
Continuation in Parts (2)
|
Number |
Date |
Country |
| Parent |
547079 |
Jul 1990 |
|
| Parent |
388936 |
Aug 1989 |
|
Patent Grant
5118651
