Process for preparing a zeolite with structure type EUO

Details Process for preparing a zeolite with structure type EUO Process for preparing a zeolite with structure type EUO

1999-11-02

2002-01-29

Sample, David R. (Department: 1755)

Chemistry of inorganic compounds

Zeolite

Seed used

C423S708000

Reexamination Certificate

active

06342200

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, TPZ-3 zeolite and ZSM-50 zeolite and 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, X represents silicon and/or germanium, T represents at least one element selected from aluminium, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese.
Zeolites with structure type EUO 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 nitrogen-containing compound acting as a structuring agent, or corresponding degradation products or precursors. The mixture is generally maintained at a certain temperature until the zeolite crystallises.
The present invention also relates to a process for preparing a catalyst based on a zeolite with structure type EUO, said zeolite being obtained using a novel synthesis mode. 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 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, a degradation product of that derivative or precursors of that derivative.
The synthesis of EU-1 zeolite from silicalite or EU-1 seeds has been described in the literature (Casci, J. L.; Whittam, T. V.; Lowe B. M., Proc. Int. Zeolite Conf., 6
th
(1984), Meeting Date 1983, 984-904, Editors Olson, David, Bisio, Allilio; publisher: Butterworth, Guildford (UK).
U.S. Pat. No. 4,640,829 concerns a ZSM-50 zeolite which according to the “Atlas of Zeolite Structure Types”, W. M. Meier and D. H. Olson, 4
th
Edition, 1996, has structure type EUO. That patent describes a mode of synthesising ZSM-50 comprising mixing a source of alkali metal ions, dibenzyldimethylammonium ions or precursors thereof, silicon oxide, aluminium oxide and water.
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′-hexamethylhexamethylenediammonium 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 process for preparing a zeolite with structure type EUO comprising at least one element X selected from silicon and germanium and at least one element T selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, characterized in that seeds of at least one zeolitic material comprising at least one element X′ selected from silica and germanium and at least one element T′ selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese is used, said seeds being different from the zeolite with structure type EUO which is prepared. The zeolite seeds used have an X′/T′ ratio of less than 200. The present invention also concerns the use of the EUO zeolite as a catalyst, said catalyst also comprising at least one element from group VIII of the periodic table and which can be used in a process for isomerising aromatic compounds containing 8 carbon atoms per molecule.
IMPORTANCE OF THE INVENTION
The process of the invention can reduce the crystallisation time of the EUO zeolite after forming the mixture, to achieve a maximum yield of pure product, which reduces the costs. The reaction medium composition can have a wider range, which increases flexibility.
Thus, the Applicant has discovered that synthesis of a zeolite with structure type EUO characterized by using seeds of at least one zeolitic material different from the material to be synthesised can achieve the advantages cited above, i.e., an advantage as regards time, pure product yield and flexibility in reaction mixture composition.
DESCRIPTION OF THE INVENTION
The invention concerns a process for preparing a zeolitic material with structure type EUO comprising at least one element X selected from silicon and germanium and at least one element T selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, characterized in that seeds of at least one zeolitic material comprising at least one element X′ selected from silica and germanium and at least one element T′ selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese is used, said seeds being different from the zeolite with structure type EUO which is prepared. The zeolite seeds used have an X′/T′ ratio of less than 200.
The different between the zeolite with structure type EUO which is to be synthesised and the zeolitic material introduced as seeds lies either in the difference in structure type, or in the difference in chemical composition of the crystalline framework, or in the difference in structure type and the difference in chemical composition of the crystalline framework.
The preparation process of the invention comprises mixing, in an aqueous medium, at least one source of at least one element X selected from silicon and germanium, 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, at least one nitrogen-containing organic compound Q selected from alkylated polymethylene &agr;-&ohgr; diammonium derivatives, dibenzyldimethylammonium salts, an amine degradation product corresponding to said organic compound Q, or corresponding precursors of said organic compound Q, and seeds S of a zeolitic material. The invention is characterized in that the seeds used comprise at least one zeolitic material different from the EUO zeolite which is to be prepared. The mixture reaction is maintained until the zeolite crystallises.
The alkylated polymethylene &agr;-&ohgr; diammonium derivative acting as a structuring agent, used more particularly for the synthesis of EU-1 zeolite or TPZ-3 zeolit

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