Chemistry of inorganic compounds – Zeolite – Organic compound used to form zeolite
Reexamination Certificate
1999-11-02
2002-01-08
Sample, David R. (Department: 1755)
Chemistry of inorganic compounds
Zeolite
Organic compound used to form zeolite
C423S708000, C423S709000, C095S090000
Reexamination Certificate
active
06337063
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel process for preparing zeolites with structure type EUO. Zeolites with structure type EUO synthesised using the process of the present invention include EU-1 and TPZ-3 zeolites. These zeolites generally have the following formula in the anhydrous form: 0 to 20 R
2
O: 0-10 T
2
O
3
: 100XO
2
where R represents a monovalent cation or 1
of a valency cation n, T represents at least one element selected from aluminum, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, and X represents silicon and/or germanium.
Zeolites with structure type EUO such as EU-1 and TPZ-3 zeolites are generally synthesised by mixing, in an aqueous medium, at least one source of silica and/or germanium and at least one source of at least one element selected from aluminium, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese in the presence of an organic compound comprising an alkylated polymethylene &agr;a-&ohgr; diammonium derivative, acting as a structuring agent. The mixture is generally maintained at a certain temperature until the zeolite crystallises.
The present invention also relates to a catalyst based on a zeolite with structure type EUO, said zeolite being obtained using the novel synthesis mode described above, and to a process for preparing said catalyst. The invention also relates to a process for isomerising aromatic compounds containing 8 carbon atoms also known as “aromatic C8 cuts” in the presence of this catalyst based on a zeolite with structure type EUO.
Isomerising ethylbenzene to xylenes requires the presence of a group VIII metal. Optimised formulations based on mordenite and a group VIII metal result in catalysts for which side reactions remain non negligible. Examples which can be cited are naphthene ring opening reactions followed or otherwise by cracking or dismutation and transalkylation of C8 aromatic compounds, which lead to the formation of undesirable aromatic compounds. The discovery of new, more selective catalysts is thus of particular importance.
PRIOR ART
The EU-1 zeolite with structure type EUO, which has already been described in the prior art, has a unidimensional microporous framework, with a pore diameter of 4.1×5.7 Å (1 Å=1 Angström=10
−10
m) (“Atlas of Zeolite Structure Types”, W. M. Meier and D. H. Olson, 4
th
edition, 1996). Further, N. A. Briscoe et al. stated in their article in the review Zeolites (1988, 8, 74) that such unidimensional channels have lateral pockets with a depth of 8.1 Å and a diameter of 6.8×5.8 Å. A method for synthesising EU-1 zeolite and its physico-chemical characteristics have been described in European patent EP-A-0 042 226. The synthesis mode comprises mixing a silicon and/or germanium oxide and an oxide of at least one element selected from aluminium, iron, gallium and boron in the presence of a structuring agent comprising at least one alkylated polymethylene &agr;-&ohgr; diammonium derivative with formula R
1
R
2
R
3
N
+
(CH
2
)
n
N
+
R
4
R
5
R
6
, the degradation products of said derivative or precursors of said derivative. The precursors of the alkylated derivative are the related diamine conjointly with alcohols or alkyl halides.
EP-A-0 051 318 relates to TPZ-3 zeolite which, according to the “Atlas of Zeolite Structure Types”, W. M. Meier and D. H. Olson, 4
th
edition, 1996, has the same EUO structure type as EU-1 zeolite. Preparation of the zeolite comprises mixing a soluble alkali metal compound, a 1,6-N,N,N,N′,N′,N′-hexamethythexamethylenediammonium compound, a compound which can provide silicon and a compound which can provide alumina, at a temperature of more than 80° C.
SUMMARY OF THE INVENTION
The present invention concerns a novel process for preparing a zeolitic material with structure type EUO in the presence of at least one precursor of an alkylated polymethylene &agr;-&ohgr; diammonium derivative acting as a structuring agent selected from monoamines. The present invention also concerns the use of said zeolite in a catalyst also comprising at least one element from group VIII of the periodic table and at least one binder. Said catalyst can be used in a process for isomerising aromatic compounds containing 8 carbon atoms.
IMPORTANCE OF THE INVENTION
The process of the invention can reduce the zeolite crystallisation time after forming the mixture, which reduces the costs. Further, the use of precursors of the structuring agent of the invention improves safety when synthesising the zeolite, said precursors being less dangerous than the structuring agent itself or than prior art precursors, and can also reduce the cost of the reactants, said precursors being cheaper than the structuring agent itself and than prior art precursors.
Thus, surprisingly, the Applicant has discovered that synthesis of a zeolite characterized by using specific precursors of the structuring agent can produce the advantages cited above, i.e., an advantage as regards time, safety and reactant costs.
DESCRIPTION OF THE INVENTION
The invention concerns a process for synthesising a zeolite material with structure type EUO comprising mixing, in an aqueous medium, at least one source of at least one element selected from silicon and germanium and at least one source of at least one element T selected from aluminium, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, in the presence of at least one precursor of an alkylated polymethylene &agr;-&ohgr; diammonium derivative acting as a structuring agent. The mixture is generally maintained at a certain temperature until the zeolite crystallises. The invention is characterized in that at least one precursor of the alkylated polymethylene &agr;-&ohgr; diammonium derivative selected from monoamines is used.
The alkylated polymethylene &agr;-&ohgr; diammonium derivative acting as a structuring agent has the following formula:
R
1
R
2
R
3
N
+
(CH
2
)
n
N
+
R
4
R
5
R
6
where n is in the range 3 to 14 and R
1
to R
6
, which may be identical or different, can represent alkyl or hydroxyalkyl radicals containing 1 to 8 carbon atoms; up to five R
1
to R
6
radicals can be hydrogen.
In addition to the precursor(s) of the structuring agent selected from monoamines in the process of the present invention, other structuring agent group(s) are generally introduced using any suitable precursor to obtain a quaternary amnmonium compound. These precursors are of F-R-F′ type where F and F′ are identical or different starting groups such as an alcohol function or a halide. As an example, an additional precursor can be selected which is at least one compound selected from alkanediols and alkane dihalides.
The precursors of the structuring agent of the invention and the other precursors can be pre-heated together in the reaction vessel or they can be mixed as they are with the other reactants. The precursors can be introduced at any moment of the zeolite preparation.
Preferably, the structuring agent precursors are introduced in solution before adding the other reactants necessary to synthesise the zeolite.
In one particular implementation, it may be advantageous to add seeds S of at least one zeolite to the reaction medium. Seeds with the EUO zeolite structure type or the structure type of other accessible and cheap zeolites such as zeolites with structure type LTA, FAU, MOR or MFI can be added. These seeds can accelerate crystallisation of the EUO zeolite from the reaction mixture. The seeds can be introduced at any point of the zeolite synthesis. Preferably, in the optional case where the EUO zeolite is synthesised using seeds, said seeds are added after at least partial homogenisation of the mixture containing the other reactants.
In a further particular implementation, independent or otherwise of the preceding implementation, it may be advantageous to add at least one alkali metal or amm
Alario Fabio
Kolenda Frederic
Lacombe Sylvie
Magne-Drisch Julia
Merlen Elisabeth
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Sample David R.
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