Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Halogen or compound containing same
Reexamination Certificate
1999-09-10
2001-02-27
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Halogen or compound containing same
C502S203000, C502S207000, C502S227000, C502S228000, C502S229000, C502S230000, C502S231000
Reexamination Certificate
active
06194345
ABSTRACT:
This invention relates to a new process for activating solid halogenated catalysts, and more particularly, supported catalysts with Lewis type sites.
We know that catalysts with an aluminum halide can be used in many processes of hydrocarbon treatment such as processes for the isomerization of paraffins, or processes for the alkylation of aromatic hydrocarbons or isobutane.
Such catalysts have been described in literature, for example in the French patents 2 320 775, 2 206 124, 2 201 128, 1 546 658 or the English patent 952 348.
In general, these catalysts contain a support, which can be an alumina, a silica, an alumina silica, an aluminosilicate or a mixture of these compounds. From among these catalysts, we can name those that contain acid sites of the Lewis acid type, obtained by a deposit of a metallic halide such as an aluminum, boron, gallium, zirconium, molybdenum, tungsten or titanium halide, and, more particularly, an aluminum chloride on the surface of the support, where these acid sites are susceptible of being transformed into activated acid sites, most likely of the Brönstedt type (because they are similar to those that result from the AlCl
3
/HCl association of catalysts of the Friedel and Crafts type), by action of a strong acid such as a halohydrous acid.
Among these catalysts, it has already been established (see French patent 2 649 989, of which the applicants are a joint holders) that the so-called “bimetallic” catalysts, in other words which contain a metal belonging to the platinum group metals associated with Lewis type sites, consisting in particular, in addition to the aluminum halides, of the halides of a metal called “promoter”, such as zirconium, molybdenum, tungsten or titanium, show an improved catalytic activity when subjected to an activation phase under specific conditions, between the actual preparation phase of these catalysts and the utilization phase of the latter in reactors where the reaction to be catalyzed is carried out.
Still according to the prior technique, we know that the activity of these catalysts increases considerably when the Lewis type acid sites are transformed into activated acid sites of the Brönstedt type by reaction with a halohydrous acid, usually hydrochloric acid, at a high temperature, meaning above a temperature of approximately 200° C. and preferably above 350° C., provided one proceeds in a non-oxidizing or reducing environment, meaning in the presence of a gas that can, at least partially, contain hydrogen. In this case, we have a direct reaction of the Lewis type sites with the hydrochloric acid, so as to create activated acid sites. However, in order to correctly promote these activated sites and ensure a good activity of the catalyst, the reaction must be carried out at high temperatures, at least equal to 400° C., and increasingly higher as the final desired activity is stronger.
Of course, such a temperature, along with the acidity of the environment, causes unavoidable corrosion problems of the material being used, and possibly contributes to a pollution of the catalyst, which is translated by significant investment costs.
In continuing her work in this field, the applicant has highlighted the fact that it is possible to obtain a considerable improvement of the activity by using a path of activation that is different from those of the prior art, meaning less costly and less polluting.
The applicant has indeed noticed, surprisingly so, that by incorporating a substantial quantity of a paraffin-base hydrocarbon to the acid environment of the reaction, one can activate the catalyst under milder conditions, at much more moderate temperatures, in the 150° C. range, and that this in consequence results in manufacturing costs that are much lower.
Therefore, the object of this invention is a process for activating a supported acid catalyst that contains Lewis acid type acid sites deposited on a solid support, by transforming, in an acid and non-oxidizing environment, said sites into activated acid sites, this process has an activation phase in an environment that contains a halohydrous acid or a halohydrous acid precursor, and is characterized by the fact that said activation phase is carried out in the presence of at least one hydrocarbon or one hydrocarbon derivative, preferably paraffin-based, with a halogen to hydrocarbon ratio that is greater than 0.001, at a temperature that is greater than 20° C. and, preferably, ranging between 100° C. and 250° C., at a pressure ranging between 10
5
and 5.10
6
Pa, for a period of time that is sufficient to obtain the transformation into activated acid sites.
In the rest of this description, we will refer in particular to the hydrochloric acid and its precursors, such as halohydrous acid, but the invention is of course, not limited to this acid.
The activation method as set forth in the invention is therefore very different from the methods described in the prior art. Indeed, according to the invention, the hydrocarbon that is introduced in the reaction environment seems to react with the Lewis type acid sites in order to create a complex on which will later react the halohydrous acid, in particular the hydrochloric acid. Contrary to the usual methods of activation, there does not seem to be, in this case, a direct chemical reaction between the Lewis type sites and the hydrochloric acid. This has the advantage of avoiding problems related to corrosion and resistance to materials encountered previously when the activation temperature was higher, along with well known problems tied to the use of hydrochloric acid at a high temperature.
The hydrocarbon contained in the environment in which said activation phase in carried out belongs to the C4 and C8 hydrocarbon family, preferably C5 and C6 hydrocarbons, and that of their halogenated derivatives.
Advantageously, the non oxidizing or reducing acid environment used in the activation phase of the process as set forth in the invention will contain a halohydrous acid or a halohydrous acid precursor.
Preferably, the halohydrous acid is hydrochloric acid and the halohydrous acid precursor is preferably carbon tetrachloride.
The Lewis site type acid sites of the activated catalyst as set forth in the invention are metallic halides of the type obtained by deposit of a metallic halide (preferably chlorine or bromine) such as an aluminum, boron, gallium or zirconium halide, or more particularly an aluminum halide or mixtures thereof on the support surface.
The catalyst supports as set forth in the invention contain heat-resistant substances have a sufficient specific surface and pore volume, and in addition have superficial chemical functions. These supports can be an alumina, a silica, an alumina silica, an aluminosilicate or a mixture of the latter, magnesia, zirconia, or gallium, titanium, thorium, boron oxides or a mixture of these oxides. Aluminas that are particularly suitable are the gamma-alumina and the eta-alumina. These aluminas serve as support for the other components of the catalyst and must therefore preferably be, for the most part, sodium free.
The most advantageous catalysts are those whose content in platinum group metals (that is to say metals chosen from among platinum, ruthenium, rhodium, palladium and iridium), in relation to the weight of the support, ranges between 0.02% and 2% by weight, preferably between 0.05% and 0.8% by weight. These catalysts can be bimetallic or trimetallic. This then makes it possible to profit from the advantages obtained by a catalyst that contains platinum and zirconium, which was not possible in the prior technique, because of the high temperature that was required.
In order to obtain satisfactory catalytic properties, the content in platinum group metals is preferably greater than 0.10%, but, because of the cost of metal, it is preferably limited to 0.80%. The deposit on the support takes place through means known in themselves, for example through impregnation using solutions that contain the metals being used, either in anionic form, or in cationic form. The support can then, als
Mangnus Peter
Milan Alain
Szabo Georges
Sughrue Mion Zinn Macpeak & Seas, PLLC
Total Raffinage Distribution , S.A.
Wood Elizabeth D.
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