Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1998-10-30
2001-08-28
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S325000, C502S330000, C502S333000, C502S334000, C502S339000, C502S340000, C502S224000, C502S226000, C502S227000, C502S229000, C502S230000, C502S216000, C502S222000, C502S223000
Reexamination Certificate
active
06281160
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel process for preparing a catalyst comprising at least one support, at least one metal from group VIII of the periodic table, and at least one additional element M selected from germanium, tin, lead, rhenium, gallium, indium and thallium. The catalyst can also contain a further metal selected from the group formed by alkali or alkaline-earth metals and/or a metalloid such as sulphur and/or any other chemical element such as a halogen or a halogen-containing compound.
BACKGROUND OF THE INVENTION
Patents and publications demonstrating that the addition of promoters to a base metal improves the quality of catalysts exist in large numbers. Such elements are added in different forms such as mineral salts or organometallic compounds. In general, more active or more selective catalysts are obtained which are sometimes also more stable than the corresponding monometallic catalyst. The manner in which such modifying agents are introduced is not unimportant as it dictates the properties of the catalyst to a great extent.
Thus catalyst formulations used in hydrocarbon conversion processes have been the subject of a very large number of studies. Supported metallic catalysts have been described, in particular in U.S. Pat. No. 3,998,900 and French patent FR-A-2 495 605. They contain a metallic phase based on platinum, modified by an additional metal M such as tin, supported on refractory inorganic oxides such as alumina. Metal M is advantageously introduced using an organometallic compound of that metal M. Such a method of introducing metal M has already been described in patents U.S. Pat. No. 3,531,543 and U.S. Pat. No. 4,548,918.
The processes cited above describe the production of a catalyst using at least one organometallic compound of metal M. Metal M is introduced in the form of at least one organometallic compound selected from the group formed by complexes, in particular carbonyl or polyketone complexes of metals M, and metal hydrocarbyls of metal M such as alkyls, cycloalkyls, aryls, metal alkylaryls and metal arylalkyls.
Introducing the additional element M in the form of an organometallic compound leads to more effective catalysts but necessitates the use of an organic solvent. The impregnating solvent described in U.S. Pat. No. 4,548,918 is selected from the group formed by oxygen-containing solvents containing 2 to 8 carbon atoms per molecule, paraffin, naphthene or aromatic hydrocarbons essentially containing 6 to 15 carbon atoms per molecule, and halogen-containing oxygen-containing organic compounds containing 1 to 15 carbon atoms per molecule. Such solvents can be used alone or mixed together.
SUMMARY OF THE INVENTION
In the present invention we have discovered that particularly effective catalysts can be prepared by introducing metal M in the form of an organometallic complex which is soluble in an aqueous solvent. This represents a considerable advance as regards ease of use during production of the catalyst. Using industrial quantities of organic solvents has many disadvantages as regards safety (flammability, toxicity) and as regards costs.
The support for the catalyst of the invention comprises at least one refractory oxide which is generally selected from oxides of metals from groups IIA, IIIA, IIIB, IVA or IVB of the periodic table such as oxides of magnesium, aluminium, silicon, titanium, zirconium or thorium, used alone or mixed together or mixed with oxides of other elements from the periodic table. Charcoal can also be used. X, Y, mordenite, faujasite, ZSM-5, ZSM-4 or ZSM-8 type zeolites or molecular sieves can also be used, as well as mixtures of oxides of group IIA, IIIA, IIIB, IVA or IVB metals with a zeolitic material.
For hydrocarbon transformation reactions, alumina constitutes the preferred support, the specific surface area of which is advantageously in the range 5 to 400 m
2
per gram, preferably in the range 50 to 350 m
2
per gram. When transforming organic functions, silica, charcoal and alumina are the preferred supports.
In addition to a support, the catalyst of the invention includes:
a) at least one group VIII metal selected from iridium, nickel, palladium, platinum, rhodium and ruthenium. Platinum and palladium are preferred metals for hydrocarbon conversion reactions. Rhodium and ruthenium are preferred metals for transforming functional molecules. The percentage by weight is in the range 0.1% to 10%, preferably in the range 0.1% to 5%, for example.
b) at least one additional element M selected from the group formed by germanium, tin, lead, rhenium, gallium, indium and thallium. Tin and germanium are preferred elements. The percentage by weight is in the range 0.01% to 10%, preferably in the range 0.02% to 5%. In some cases, at least two of the metals from this group can advantageously be used at once.
Depending on the application, the catalyst can optionally also contain 0.1% to 3% by weight of a halogen or halogen-containing compound. It can also contain 0.1% to 3% by weight of an alkali or alkaline-earth metal. Optionally, it can also contain 0.01% to 2% by weight of an element such as sulphur.
The catalyst can be prepared using different procedures for impregnating the support and the invention is not limited to any specific impregnation procedure. When several solutions are used, intermediate drying and/or calcining steps can be carried out.
The additional element M can be introduced during production of the support. One method, for example, consists of blending the moist powdered support with catalyst precursors and then forming and drying.
The group VIII metal, additional metal M, optional halogen or halogen-containing compound, optional alkali or alkaline-earth metal, and optional metalloid, can be introduced simultaneously or successively, in any order. In accordance with the invention, the characteristic feature of contact with the organometallic element M is that it is introduced in an aqueous solvent.
In a further method, the additional metal M can be introduced during synthesis of the support using a sol-gel type technique. As an example, for a support containing alumina, a mixed metal M—alumina gel can be obtained by hydrolysing an organic solution of Al(OR′)
3
in a solvent such as ROH or R′OH using an aqueous solution of an organometallic compound of metal M. R and R′ represent a methyl, ethyl, isopropyl, n-propyl or butyl type alkyl group or a heavier group such as n-hexyl. The alcoholic solvent must be highly dehydrated before introducing the aluminium alcoholate. After hydrolysis, heat treatment of the gel obtained carried out at a temperature in the range 200° C. to 800° C., preferably in the range 300° C. to 700° C., and more preferably in the range 400° C. to 500° C., ensures complete reaction of the hydrosoluble organometallic compound of metal M with the gel, which causes formation of the mixed oxide Al
2
O
3
—MO
x
.
In a still further method, metal M can be added to an alumina sol. U.S. Pat. No. 3 929 683 describes introducing tin in the form of a salt, for example SnCI
2
, into an alumina sol. In the present invention, it is possible to add a hydrosoluble organometallic compound of metal M to an alumina hydrosol obtained, for example, by precipitating an acid solution of AlCl
3
at pH 4-5, then encouraging the compound of metal M to react with the alumina hydrosol, for example using heat or a base.
The precursor of element M can be selected from the group formed by halogen-containing compounds, hydroxides, oxides, carbonates and carboxylates of organometallic compounds of element M, this list not being limiting. These compounds comprise at least one carbon-M bond. As an example, the precursor of element M can be selected from trimethyl halides Me
3
MX, dimethyl dihalides Me
2
MX
2
, trimethyl hydroxides Me
3
MOH, dimethyl dihydroxides Me
2
M(OH)
2
, triethyl halides Et
3
MX, diethyl dihalides Et
2
MX
2
, triethyl hydroxides Et
3
MOH, isopropyl dihalides iPr
2
MX
2
, or bis-tributyl oxides [Bu
3
M]
2
O, where X represents a halogen
Basset Jean-Marie
Bentahar Fatima
Candy Jean-Pierre
Clause Olivier
Didillon Blaise
Institute Francais du Petrole
Millen White Zelano & Branigan P.C.
Wood Elizabeth D.
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