Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Patent
1992-08-20
1994-09-27
McFarlane, Anthony
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
4233281, 4233291, 423703, 423706, B01J 2906
Patent
active
053507223
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a novel MTW-type zeolite and to a process for preparing said zeolite.
Due to their geometrical selectivity and ion exchange properties, zeolites are industrially used on a considerable scale, both in adsorption (e.g. drying gases, separating straight and branched-chain paraffins, separation of aromatic compounds, etc.) and in catalysis (e.g. catalytic cracking, hydrocracking, isomerization, oligomerization, etc.).
The chemical composition of the zeolites containing in their skeleton the elements Si and Al can be represented by the following approximate formula: earth or organic cation, which case the zeolite is a microporous silica.
Although numerous aluminosilicate-type zeolites exist naturally, the search for products having novel properties has led over the last few years to the synthesis of a large number of such zeolitic structure aluminosilicates. A novel zeolite, without any known natural equivalent and discovered in the early 1970's is the ZSM-12 zeolite (U.S. Pat. No. 3,832,449). This zeolite is also known under the names CZH-5 (GB-A-2079735), Nu-13 (EP-A-0059059), Theta-3 (EP-A-0162719) and TPZ-12 (U.S. Pat. No. 4,557,919). The zeolite structure carrying these different names is referred to as of the MTW structural type (R. B. LaPierre et al, Zeolites, 5, p. 346, 1985). These MTW-type zeolites are still synthesized in the presence of sodium cations and a very limited number of organic structuring agents. To obtain the MTW zeolite, it is necessary to start with a reaction mixture containing Na.sup.+ cations and an organic structuring agent, which can e.g. result from the reaction of triethyl amine and diethyl sulphate.
All MTW-type zeolites have hitherto been synthesized in a conventional medium, i.e. in an alkaline medium at a pH generally exceeding 9, in which the silica mobilizing agent is OH.sup.-. Another zeolite synthesis medium has recently been discovered and is in fact the fluoride medium, in which the silica mobilizing agent is the F.sup.- anion. In this medium, the pH is generally below 10 (cf. e.g. J. L. GUTH, H. KESSLER and R. WEY, Proc. Int. Zeolite Conf., Tokyo, Aug. 17-22, 1986, p. 121). The synthesis of a limited number of zeolytic structures has already successfully taken place in this novel medium, such as e.g. MFI (French patent application 88/09631) and ferrierite (French patent application 86/16362).
Compared with the alkaline synthesis medium (OH.sup.-), the fluoride medium has a certain number of very significant advantages. Thus, in an alkaline medium, most synthesized zeolites are metastable. Thus, during synthesis more stable solid phases may appear and undesired phases are precipitated. This difficulty increases when the quantities to be prepared increase, i.e. on passing from the laboratory to the industrial stage. Moreover, these metastable zeolites in the basic reaction medium are only obtained by a significant supersaturation of active species in the medium, which leads to a rapid nucleation and consequently to crystals of approximately 1 micrometer. However, in certain applications, it may be of interest to have crystals of a larger size, so as to e.g. maintain the thermal stability of the solid.
Numerous applications, particularly in acid catalysis, require zeolites in a proton form completely free from their alkali metal or alkaline earth compensation cations introduced during synthesis. It is possible to obtain the proton form by carrying out repeated, long exchanges with NH.sub.4.sup.+ cations, followed by calcination in order to decompose the said cations into protons. These ion exchange stages could be avoided if it was possible to entirely replace the alkali metal or alkaline earth cations by cations decomposable during synthesis, i.e. NH.sub.4.sup.+ and/or organic cations. It is not possible to introduce NH.sub.4.sup.+ cations into the solid during synthesis in the basic medium because the pH is too high and then NH.sub.4.sup.+ would be transformed into NH.sub.3. In addition, syntheses carried out at pH-values where the NH.sub.4.sup
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Journal of the Chemical Society, Chemical Communications, No. 14, Jul. 15, 1988, pp. 920-921, Ed. The Royal Society of Chemistry, Cambridge, GB; M. E. Davis et al.: "Synthesis of gmelinite and ZSM-12 zeolites with a polymer template".
Journal of the Chemical Society, Chemical Communications, No. 19, Oct. 1, 1990, pp. 1313-1314, Ed. The Royal Society of Chemistry, Cambridge, GB; Z. Daging et al.: "Synthesis of large single crystals of pentasil-type silica zeolites from non-alkaline medium".
New Developments in Zeolite Science and Technology, Proceedings of the 7th International Zeolite Conference, Tokyo; Aug. 17-22, 1986, pp. 121-128, Kodansha, Tokyo, JP; J. L. Guth et al.: "New route to pentasyl-type zeolites using a non-alkaline medium in the presence of fluoride ions".
Baron Jacques
Caullet Philippe
Faust Anne-Catherine
Guth Jean-Louis
Joly Jean-Francois
Institut Francias Du Petrole
McFarlane Anthony
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