Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Reexamination Certificate
1997-12-15
2001-03-20
Dunn, Tom (Department: 1754)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
C502S068000
Reexamination Certificate
active
06204423
ABSTRACT:
A catalytic compound is described, comprising a mixture of Y zeolite and a smectite containing alumina pillars together with a process for the alkylation of aromatic hydrocarbons by means of long-chain linear olefins which uses this composition.
Alkylaromatic compounds have numerous industrial applications. Among these the most important relate to their use in the preparation of biodegradable synthetic detergents. Processes for the preparation of aromatic compounds using Friedel-Crafts type catalysts such as for example AlCl
3
, BF
3
, H
2
SO
4
and HF, have been known for some time. These catalysts however obviously have considerable disadvantages not only because they create problems of corrosion of the materials used, but also because of the environmental problems associated with eliminating the waste products.
It was subsequently found that some solid catalysts can be used to carry out the alkylation of aromatic hydrocarbons with olefins giving a production of a similar quality to the above but without the problems of environment and corrosion. Both zeolites and clays suitably treated have therefore been used for this purpose. In the U.S. Pat. No. 2,904,607, for example, for the alkylation of aromatic hydrocarbons with olefins a metallic alumino-silicate is used with pores of 6‥15 Å. U.S. Pat. No. 3,251,897 describes alkylation with exchanged zeolites in a protonic form or with rare earths. U.S. Pat. No. 3,417,148 relates to the alkylation of an aromatic compound, for example benzene, toluene or xylenes, with an olefin, catalyzed by a crystalline aluminosilicate chemically combined with metallic fluorides.
In particular, the Journal of Catalysis, 5, 81-98, (1966), by P. B. Venuto et al., describes the use of the Y zeolite for the alkylation of aromatic substrates with a wide variety of alkylating agents among which are olefins. In the Journal of Catalysis, 26, 303-312, (1972), by T. Yashima et al., a Y zeolite, exchanged with alkaline cations, is used for the alkylation of toluene with methanol and formaldehyde. Y zeolites are also used in the transalkylation of alkylaromatics, as described for example in the Journal of Catalysis, 140, 384-394, 1993.
Other materials known as alkylation catalysts are natural or synthetic clays exchanged with metallic cations. In U.S. Pat. No. 4,046,826, for example, a natural trioctahedric clay or synthetic clay exchanged with metallic cations is used for the alkylation of benzene with long-chain olefins. Patent U.S. Pat. No. 4,499,319 claims the use of clays stratified with a lamellar structure, such as montmorillonite, exchanged with metallic cations such as chromium and aluminium, for the alkylation of aromatic compounds with alkylating agents containing less than 6 carbon atoms. Synthetic clays exchanged with cations and then suitably activated, useful for the alkylation of aromatic compounds, are described in U.S. Pat. No. 4,075,126.
In EP 353813, natural or synthetic zeolites, amorphous silico-aluminas, clays, or their mixtures, possibly subjected to ion exchange with aluminium salts, chromium or rare earths, are used for the catalytic alkylation of aromatic hydrocarbons with olefins.
Clays exchanged with metallic cations however have proved to have a limited thermal stability. Modified clays called “pillared clays” which, compared to the above materials, are stable even at high temperatures, were subsequently used as alkylation catalysts.
These materials are prepared starting from synthetic or natural clays, such as smectites, vermiculites or bentonites. The clays consist of layers of semi-crystalline aluminosilicates bound to each other by Van der Waals electrostatic forces. The anion charges on the silica layers are neutralized by cations, situated in the interlamellar spaces. These cations, normally Na
+
and Ca
2+
, can be exchanged with monomeric, oligomeric or polymeric species deriving from metal hydroxides such as hydroxo-polymer cations [Al
13
O
4
(OH)
24
(H
2
O)
12
]
7+
or [Zr(OH)
2
H
2
O]
4
8+
. These cations act as a separation system of the crystalline silicoaluminate layers, or as a pillaring system. Patent EP 83970 describes the use of a clay in which pillars of alumina are anchored inside the laminar structure for the alkylation of benzene with light olefins. In patent U.S. Pat. No. 5,034,564 a pillared clay containing a metal oxide selected from Al, Zr, La, Ce and Ti as a spacing element of the crystalline layers, coextruded with a binder, is used in alkylation reactions of aromatic hydrocarbons.
In Applied Catal., 14, 69-82 (1985) by M. L. Occelli, a Na-montmorillonite stratified with a system of clusters of aluminium oxide is compared to other types of catalysts in the ethylation reaction of toluene.
U.S. Pat. No. 4742033 describes a cracking catalyst consisting of a pillared clay pretreated with suitable inorganic reagents. This catalyst, possibly mixed with a zeolite, is compared, among others, to a catalyst consisting of 10% by weight of Y zeolite and 90% by weight of a pillared clay, where the clay is bentonite, in the cracking process of hydrocarbons.
It has now been surprisingly found that it is possible to carry out the alkylation of aromatic hydrocarbons with long-chain olefins operating in the presence of a catalytic composition comprising a mixture of a Y zeolite and a suitable pillared clay. This catalytic composition allows better results than those obtained either using each of the elements individually or using a mixture consisting of a Y zeolite and a clay. These better results relate to both the catalyst activity and its duration and also to the selectivity to linear alkylbenzenes.
The present invention therefore relates to a catalytic composition comprising a mixture of Y zeolite and a smectite containing pillars of alumina, with a weight ratio between Y zeolite and smectite with alumina pillars of between 0.1 and 10, excluding the ratio 1:9 when the smectite is bentonite.
In the catalytic mixture the weight ratio between Y zeolite and smectite with alumina pillars is preferably between 0.3 and 1.5.
The Y zeolite which can be used in the present invention is in acid form and is described in U.S. Pat. No. 3,130,007.
Smectites containing pillars of aluminium oxide which can be used in the catalytic composition of the present invention are those which can be obtained by the treatment of a clay of the group of smectites with a solution containing polyoxoaluminium ions, followed by the calcination of the resulting solid, as described for example in the patents U.S. Pat. No. 4,216,188 and U.S. Pat. No. 4,176,090. The smectite is preferably selected from bentonite, montmorillonite and beidellite.
As a typical example, the solution of polyoxoaluminium ions is prepared by adding, at a temperature of between 25 and 100° C., a solution of NaOH to a solution of AlCl
3
, so that the molar ratio between the reagents is between 1 and 2.5. The resulting mixture is maintained under stirring, at a temperature of between 25 and 100° C., for 1-10 hours. A suspension in water of a clay belonging to the group of smectites, heated to a temperature between 25 and 50° C. is then put in contact with the previously prepared aqueous solution of polyoxoaluminium ions, also known as Kegging ions. The weight ratio between clay and AlCl
3
previously used to prepare the solution of polyoxoaluminium ions is between 2 and 5. The mixture thus obtained is maintained under stirring at a temperature of between 25 and 100° C. for 1-60 hours. The pH of the solution is between 3 and 7.
The resulting solid, isolated for example by centrifugation, consists of a clay belonging to the group of smectites inside whose laminar structure the polyoxoaluminium ions have substituted the metallic cations naturally present. This humid material is subjected to calcination at a temperature of between 200 and 700° C., for a period of between 2 and 10 hours, to decompose the polyoxoaluminium ions to give pillars of alumina.
The material resulting from the calcination is therefore a smectite containing a
Amarilli Stefano
Bellussi Giuseppe
Colombo Giovanni
Perego Carlo
Dunn Tom
Enichem Augusta Industriale s.r.l.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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