Catalytic hydroreforming process

Details Catalytic hydroreforming process Catalytic hydroreforming process

2000-10-16

2001-11-13

Griffin, Walter D. (Department: 1764)

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Reforming

C208S138000, C208S134000, C502S506000, C502S514000, C502S513000

Reexamination Certificate

active

06315892

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application is related to commonly assigned application Ser. No. 08/238,856 filed May 6, 1994, entitled “PROCESS OF CATALYTIC HYDROGENATION,” by Fabienne Le Peltier et al., the disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
This invention pertains to a process for converting hydrocarbons by hydroreforming, in the presence of a catalyst that contains a carrier, at least one metal from the platinum family (since the presence of platinum is necessary, it can be combined with another element from Group VIII in the periodic table), at least one additional metal (referred to as metal M) selected from among germanium, tin, lead, gallium, indium, and thallium, and a halogen (or a halogen compound).
There are many patents and publications showing that adding catalyst promoters to a base metal improves the quality of the catalysts. These elements are added in different forms such as salts or organometallic compounds. This generally produces more active or more selective catalysts, sometimes more stable than with the base metal. The way in which these modifiers are added is significant since it greatly influences the properties of the catalysts.
Acidic catalysts containing, in addition to a carrier, a noble metal from the platinum family and at least one additional metal selected from among the group consisting of tin, germanium, and lead, (FR-A-2031984), gallium, indium, and/or thallium (U.S. Pat. No. 2,814,599) have long been known.
SUMMARY OF THE INVENTION
This invention provides a modification of a catalyst, hereinafter referred to as a “precatalyst”, by adding, under well controlled conditions, modifier elements directly into the reactor or prereactor where the use of the catalyst must be made. This approach has a number of practical advantages, but, surprisingly enough, it has been found that this means of production makes it possible to obtain considerably better-performing catalysts than those obtained by off-site preparation.
The process of catalytic hydroreforming as well as the catalytic process of producing aromatic hydrocarbons according to the invention are carried out at, for example, a temperature between 400° C. and 600° C. at an absolute pressure of between 0.1 and 3.5 MPa, and at an hourly rate of between 0.1 and 10 volumes of liquid charge per volume of catalyst, with the ratio of hydrogen to hydrocarbons being between 1 and 20. The catalysts that are prepared according to the invention make it possible especially to implement these two processes under harsh conditions. Thus, the use of these catalysts is applied, in particular, to reforming reactions to obtain a gasoline with a clear octane number equal to or greater than 102. More specifically, the severe conditions of the hydroreforming or catalytic hydroreforming reactions are as follows: a mean temperature of between approximately 480° C. and 580° C., a pressure of between 0.2 and 1.8 MPa, and preferably between 0.3 and 3 MPa, an hourly rate of between 1 and 10 volumes of liquid charge per volume of catalyst, and a recycling rate of between 1 and 6 mols of hydrogen per mol of charge. If the charge is unsaturated, i.e., if it contains monoolefins or polyolefins, it must first be stripped of them through complete hydrogenation. The charge is generally a direct-distillation naphtha, a pyrolysis gasoline, or a cracked gasoline, especially a vapor-reformed gasoline.
The carrier of the catalyst according to the invention comprises at least one refractory oxide which is generally selected from among the oxides of the metals of Groups II, III, or IV of the periodic system, such as for example the oxides of magnesium, aluminum, silicon, titanium, zirconium, or thorium, either by themselves or mixed together or mixed with other oxides of elements of the periodic system. It is also possible to use carbon. It is additionally possible to use zeolites or molecular sieves of the types X, Y, mordenite, faujasite, ZSM-5, ZSM-4, ZSM-8, etc., as well as mixtures of metallic oxides of groups II, III, and/or IV with zeolitic material.
For reactions involving reforming or the production of aromatic hydrocarbons, the preferred carrier is aluminum oxide, whose specific surface area is advantageously between 50 and 400 m
2
per gram, and preferably between 100 and 400 m
2
per gram.
The precatalyst is prepared from a preformed carrier according to standard methods that consist in impregnating the carrier with solutions of compounds of the elements that are desired to be introduced. Either a common solution of the metals that are present in the precatalyst or different solutions in some order are used. When several solutions are used, intermediate drying and/or calcination steps are carried out.
For example, the introduction of platinum (and possibly other metals from Group VIII and, for example, the elements of the platinum family) can be performed by impregnating the carrier with an aqueous solution of a halogen compound. Platinum is preferably introduced in the form of chloroplatinic acid.
After the introduction of the Group VIII metal, the product obtained is calcined, after an optional drying; calcination is preferably carried out at a temperature of between 400 and 700° C. and optionally in the presence of a halogenated organic compound. The halogenated organic compounds are selected, for example, from the group consisting of carbon tetrachloride, chloroform, dichloromethane, and dichloropropane, as described in FR-A-2,594,711.
In that same patent, the introduction of the additional metal(s) M is also described. Thus, after halogen is introduced, the additional metal(s) is (are) introduced into the precatalyst. Optionally before said metal M is introduced, reduction with hydrogen is carried out at a high temperature, for example, between 300 and 500° C. This reduction can consist of, for example, a slow rise in temperature under a stream of hydrogen up to a desired temperature of between 300 and 500° C., and preferably between 350 and 450° C., followed by a holding at this temperature under hydrogen for 1-6 hours.
The additional metal M is introduced in the form of at least one organometallic or alcoholate compound selected from the group consisting of complexes, especially the carbonylic and polyketonic complexes of metals M, and the hydrocarbyl metals of metal M such as alkyls, cycloalkyls, aryls, metal alkylaryls, and metal arylalkyls.
It is advantageous to introduce metal M by means of a solution in an organic solvent of the alcoholate or organo-metallic compound of said metal M. It is also possible to use organo-halogenated compounds of metals M. Compounds of metals M that can be mentioned include but are not limited to, in particular, tetrabutyl tin, tetramethyl tin, tetrapropyl germanium, diphenyl tin, tetraethyl lead, indium acetylacetonate, thallium acetylacetonate, thallium ethanolate, triethyl gallium, and a rhenium carbonyl.
The impregnation solvent is preferably from the group consisting of oxygenated organic solvents containing 2-8 carbon atoms per molecule and the paraffinic, naphthenic, or aromatic hydrocarbons containing essentially 6-15 carbon atoms per molecule and halogenated organic compounds containing 1-15 carbon atoms per molecule. Specific examples include but are not limited to ethanol, tetrahydrofuran, n-heptane, methyl cyclohexane, toluene, and chloroform. These solvents can be used by themselves or mixed together, as well as in the way described in the patent U.S. Pat. No. 4,548,918.
It has now been discovered that introducing additional metal M in situ produces unexpected results. A preferred method of introduction is characterized by said additional metal M being introduced by bringing at least one organic compound of the additional metal M (in pure form or optionally diluted with at least one hydrocarbon solvent) into contact under an inert atmosphere (for example, nitrogen) with the precatalyst that has been loaded into the reactor where the reaction charge(s) will be injected, i.e., the reactor where the hydrocarbons

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