Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1992-10-16
1994-08-16
McFarlane, Anthony
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
4233291, 423332, 502 61, 502 64, C01B 3326, B01J 2906
Patent
active
053385250
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a novel MFI-type zeolite and to a process for preparing said zeolite.
As a result of their geometrical selectivity and ion exchange properties, zeolites are industrially used on a wide scale, both in adsorption (e.g. gas drying, separation of straight and branched-chain paraffins) and in catalysis (e.g. catalytic cracking, hydrocracking, isomerization and oligomerization).
All the MFI-type zeolites containing Al and/or Ga prepared up to now have been synthesized either in an alkaline medium (pH generally above 9) in the presence or absence of organic agents, or in a fluoride medium (pH generally below 10) in the presence of organic agents.
The fluoride synthesis medium can be used for obtaining the MFI zeolite (FR-A-2567868, 2607128). All the syntheses of MFI zeolites in a fluoride medium according to the prior art are characterized by the presence in the reaction medium of an organic agent, e.g. tetrapropyl ammonium (TPA.sup.+) or tetrapropyl phosphonium. The proton form of the zeolite is then obtained by calcination. From an economic standpoint, it would be advantageous to be able to synthesize the MFI zeolite in the absence of an organic structuring agent. Compared with the alkaline synthesis medium (OH.sup.-) the fluoride medium has a certain number of very significant advantages (cf. e.g. J. L. Guth, H. Kessler and R. Wey, Proc. 7th Int. Zeolite Conf., Tokyo, Aug. 17-22, 1986, p.121). Thus, in the alkaline medium, most synthesized zeolites are metastable, so that during synthesis more stable solid phases may appear and undesired phases may be precipitated. This difficulty is increased when the quantities to be prepared increase, i.e. on passing from the laboratory to the industrial scale.
A supplementary advantage of syntheses carried out in a fluoride medium compared with those carried out in a conventional OH.sup.- medium is that solids are obtained, whose acid and ion exchange properties are of different natures. The acid catalysts prepared from the solids obtained in the fluoride medium have improved catalytic properties. At this level it is very important to point out that the crystallographic structure of a solid is not sufficient to entirely define its properties and more particularly its acid properties, which play a vital part in catalysis.
SUMMARY OF THE INVENTION
Unlike in the case of their homologs prepared in a basic medium in the absence of an organic agent according to the prior art, the MFI-type zeolites according to the invention contain fluorine after synthesis. As will be shown hereinafter, fluorine gives the MFI zeolites according to the invention special acid and ion exchange properties. Unlike the MFI zeolites synthesized in the fluoride medium according to the prior art, the MFI zeolites according to the invention are prepared in the complete absence of an organic structuring agent.
The invention therefore relates to a novel synthetic crystalline zeolite of the MFI type, as well as a synthesis process in a fluoride medium and in the absence of an organic agent and which also gives the zeolites according to the invention improved properties and in particular acid properties. The MFI zeolite according to the invention can be used in adsorption and in catalysis.
DETAILED DESCRIPTION OF THE INVENTION
The synthetic crystalline zeolite of the MFI type according to the invention is characterized by: ].sup.(x+y).sup.- a proton, x being a number between 0 and 24, y a number between 0 and 24, (x+y) a number between 0.64 and 24 and preferably between 1.88 and 19.2, description, 2.0% by weight, preferably between approximately 0.02 and 1.0% by weight.
It is also characterized in that it was synthesized in a fluoride medium and in the absence of an organic agent.
The invention also relates to a process for the preparation of said MFI-type zeolite and which in particular comprises: approximately 9 and containing water, at least one silica source, at least one aluminium source, at least one gallium source, at least one mobiliz
REFERENCES:
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patent: 4806699 (1989-02-01), Smith et al.
patent: 4868146 (1989-09-01), Chu et al.
patent: 5034363 (1991-07-01), Petit et al.
patent: 5202513 (1993-04-01), Kanai
Chemical Abstract, vol. 104, No. 10, Mar. 10, 1986, Columbus, Ohio US; Abstract No. 75827Z; Zhao, Zhenhua: "Synthesis of ZSM-5 Zeolite with a New Method", p. 449; column G; & Hunan Shifan Daxue Xuebac, Zirhan Kexueban 1985, 8(3), 60-66.
Chemical Abstracts, vol. 105, No. 18, Nov. 3, 1986, Columbus, Ohio US; Abstract No. 155556W, "Direct Synthesis of ZSM-5 Zeolite" p. 149 column G; & CN 85100463 (Feb. 10, 1986).
Brunard Nathalie
Caullet Philippe
Faust Anne-Catherine
Guth Jean-Louis
Joly Jean-Francois
Institut Francais du Pe'trole
McFarlane Anthony
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