Chemistry of inorganic compounds – Zeolite – Organic compound used to form zeolite
Patent
1996-05-03
1997-11-04
Bell, Mark L.
Chemistry of inorganic compounds
Zeolite
Organic compound used to form zeolite
423705, 423DIG27, C01B 3902
Patent
active
056836732
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP94/02458.
This invention relates to a process for the manufacture of a zeolite, especially to one suitable for use as an absorbent or catalyst, to the zeolite produced by the process, and to organic reactions, especially oxidations of hydrocarbons, catalysed thereby.
Zeolite Beta is a large pore, high silica zeolite material first described in 1967, in U.S. Pat. No. 3,308,069. Because of its large pore size, based on 12-membered rings, it is useful as a catalyst for reactions involving larger organic molecules than can be accommodated in the pore of the more commonly used ZSM-5, 10-membered ring, zeolite catalysts.
The previously proposed processes for the manufacture of the catalyst have all employed synthesis mixtures containing cations of an alkali metal; indeed, in an article by Camblor et al, Zeolites, 1991, 202 to 210, it is suggested that the presence of alkali metal cations is essential for the formation of the zeolite. Certainly, in the existing processes yields in the absence of alkali metal cations are very low.
The presence of alkali metal cations in the synthesis mixture is, however, disadvantageous, especially when the zeolite is to be used as an acidic catalyst, since any necessary post-calcination treatment is made longer by the presence of substantial alkali metal concentrations.
The present invention is based on the observation that if ethene is present in contact with a Beta-forming synthesis mixture during the hydrothermal treatment Beta zeolite is obtained in good yields.
The present invention accordingly provides in a first aspect a process for the manufacture of a Beta zeolite in which at least a part of a hydrothermal treatment of a Beta zeolite-forming synthesis mixture is carried out under an ethene-containing atmosphere at a pressure of at least 20 bar and advantageously under an ethene partial pressure of at least 5 bar.
In a second aspect, the invention provides a process for the manufacture of a Beta zeolite in which at least a part of a hydrothermal treatment of a Beta zeolite forming synthesis mixture is carried out in the presence of at least 0.1 mole of ethene per mole of tetraethylammonium cations. Advantageously, the mole ratio of ethene:tetraethylammonium is in the range 0.1 to 1:1.
As a Beta forming synthesis mixture, there is typically used a mixture comprising a source of silicon, a source of aluminium, water, and a source of tetraethylammonium cations. The aluminium may, however, be replaced wholly or in part by other cations, for example gallium, boron, or iron.
The synthesis mixture is advantageously substantially free from alkali metal cations; by substantially free is meant the absence of more alkali metal than is inevitably present in commercial supplies of the essential components. If alkali metal ions, e.g., sodium or potassium ions, are present, they are advantageously present in a molar proportion of SiO.sub.2 :M.sup.+ of 1: at most 0.5.
Advantageously, the synthesis mixture has a molar composition within the following ranges: SiO.sub.2 (1); Al.sub.2 O.sub.3 (0.0005 to 0.1); H.sub.2 O (10 to 100) and TEAOH (0.01 to 1).
Advantageously, the Si:Al molar ratio is within the range of from 50 to 200:1.
Preferred sources of the components are: for silicon, colloidal silica, advantageously a colloidal silica substantially free from alkali metal cations, or a tetraalkylammonium orthosilicate; and for aluminium, aluminium powder. If the aluminium is replaced by other cations, suitable sources are, for example; gallium nitrate or oxide, boric acid or an alkoxide thereof, e.g., B(OC.sub.2 H.sub.5).sub.3, or ferric nitrate. The tetraethyl ammonium cations are advantageously provided by TEAOH.
If desired or required to assist dissolution of any reactants, hydrogen peroxide may be present in the synthesis mixture.
Advantageously, especially if it contains hydrogen peroxide, the synthesis mixture is aged between its formation and the hydrothermal treatment. Ageing may be carried out at room temperature or at elevated temperatures, for exa
REFERENCES:
patent: 3308069 (1967-03-01), Wadlinger et al.
patent: 4847055 (1989-07-01), Chu
patent: 4916097 (1990-04-01), Chu et al.
patent: 4923690 (1990-05-01), Valyocsik et al.
Buskens Philip Luc
Martens Luc Roger Marc
Mathys Georges Marie Karel
Bell Mark L.
Exxon Chemical Patents Inc.
Sample David
Sherer Edward F.
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