Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By isomerization
Reexamination Certificate
2000-03-31
2002-07-02
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By isomerization
C585S480000, C585S906000
Reexamination Certificate
active
06414208
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing petrochemicals, using as a metallosilicate catalyst whose main cavity is defined by a ten-oxygen-membered ring.
2. Background Art
Since metallosilicates—“metallosilicates” is herein a general term for aluminosilicates and their analogues in which aluminum atoms contained in the aluminosilicate framework are replaced with other metals—have solid acidity. For that reason, they have conventionally been used as catalysts for hydrocarbon conversion reactions such as catalytic cracking, hydrocracking, disproportionation and isomerization, and various chemical reactions such as chemical synthesis reactions. A metallosilicate is present as a crystal having stereoregular structure in which oxygen atom is shared by a SiO
4
tetrahedron and an MO
4
(M is Al or any other metal atom) tetrahedron to form a three-dimensional network. In such a crystal, a ring composed of Si, O and M atoms, characteristic of the above linkage forms a cavity.
Metallosilicates show various solid acidities depending upon, for example, the type of metallosilicate and the coexisting cation, and have their own characteristic cavities. Moreover, the particle diameters of metallosilicates are controllable, and various modifications of metallosilicates are possible. Therefore, metallosilicates suitable as catalysts for specific chemical reactions have respectively been developed and used. For instance, among metallosilicates in which M is aluminum, that is, aluminosilicates, X- or Y-type aluminosilicate called faujasite is used, for example, as a catalyst for catalytic cracking or hydrocracking in petroleum refining; mordenite is used, for example, as a disproportionation or isomerization catalyst; and ZSM-5 is used as a catalyst for the synthesis of gasoline from methanol, or for various chemical synthesis reactions. Further, metallosilicates in which M is a metal atom other than aluminum are used as catalysts, for example, for the aromatization of light naphtha.
On the other hand, there is a demand for zeolite catalysts that show great specificity and high selectivity in specific chemical reactions. 2,6-Dimethylnaphthalene, for instance, can be produced by the isomerization reaction of a dimethylnaphthalene. It has been known that, although the isomerization of a dimethylnaphthalene, where methyl group is transferred from the &agr;-position to the adjacent &bgr;-position and vice versa, can readily be attained, it is difficult to conduct isomerization of other types (Fries rule). It has therefore been difficult to isomerize a dimethylnaphthalene included in one of the following four groups of (1)-(4) to one included in any of the other groups:
(1) the group of 2,6-dimethylnaphthalene: 2,6-dimethylnaphthalene, 1,6-dimethylnaphthalene and 1,5-dimethylnaphthalene;
(2) the group of 2,7-dimethylnaphthalene: 2,7-dimethylnaphthalene, 1,7-dimethylnaphthalene and 1,8-dimethylnaphthalene;
(3) the group of 1,4-dimethylnaphthalene: 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene and 2,3-dimethylnaphthalene; and
(4) the group of 1,2-dimethylnaphthalene: 1,2-dimethylnaphthalene.
Various methods for isomerizing a dimethylnaphthalene have been proposed so far: for instance, a method in which a dimethylnaphthalene included in one of the above described four groups is isomerized to one included in the same group by using, as a catalyst, mordenite-type zeolite (e.g., Japanese Patent Laid-Open Publications No. 47020/1980 and No. 298675/1994); and a method in which a dimethylnaphthalene included in the group of 2,6-dimethylnaphthalene is isomerized to one included in this group by using, as a catalyst, faujasite-type zeolite represented by Y-type zeolite (e.g., Publication No. 500052/1991 of Japanese Translation of PCT Patent Application).
Further, a method using a pentasil-type crystalline aluminosilicate catalyst, the entrance of the main cavity of this aluminosilicate being defined by a ten-oxygen-membered ring, has been proposed as a method for isomerizing a dimethylnaphthalene included in the group of 2,7-dimethyl-naphthalene to one included in the group of 2,6-dimethylnaphthalene (e.g., Japanese Patent Laid-Open Publication No.88433/1984). There has also been proposed, as a method for isomerizing a dimethylnaphthalene included in the group of 2,3-dimethylnaphthalene to one included in the group of 2,7-dimethylnaphthalene or of 2,6-dimethylnaphthalene, a method in which a pentasil-type crystalline aluminosilicate composed of particles containing 50% by volume or more of such particles whose secondary particles have diameters smaller than 5 &mgr;m is used as a catalyst in order to increase the efficiency of isomerization between two dimethylnaphthalenes included in different groups (e.g., Japanese Patent Laid-Open Publication No. 255139/1993).
Furthermore, there is a report on the studies in the relationship between the particle diameters of crystals and catalytic performance, in the correlation between the distribution of acid centers present on the internal or external surfaces of crystals and shape selectivity, and in the shape-selective isomerization of dimethylnaphthalenes (“Effects of Particle Diameters of Crystals of H-ZSM-5 Catalyst on the Isomerization of Dimethylnaphthalenes”, 78th CATSJ Meeting Abstracts: Vol. 38, No. 6, 1966, No. 4, B05, 474-477 (1996)). In addition, a process for rapidly producing a zeolite catalyst has been reported (T, Inui, “Mechanism of Rapid Zeolite Crystallization and Its Applications to Catalyst Synthesis”, Zeolite Synthesis, ACS Symp. Series, 398, Chapter 33, 1989, American Chemical Society).
With respect to poisoning of zeolite catalysts on the external surfaces of their crystals and in their internal cavities, there is a report on poisoning of HZSM-5 by quinolines on its external surface (S. Namba, et al., Journal of Catalysis, 88, 505-508(1984)).
SUMMARY OF THE INVENTION
We found the following: a metallosilicate catalyst that comprises a metallosilicate having a main cavity defined by a ten-oxygen-membered ring, that is in the form of aggregates of fine crystals of the metallosilicate, the external surface area of the aggregate being in a specific range, and that has been treated to inactivate acid centers present on the external surfaces of the fine crystals until the rate constant basic value becomes a predetermined value shows great reaction specificity and high shape selectivity in various chemical reactions, and achieves high reaction efficiency and high degrees of conversion to remarkably increase the yields of desired products. The present invention.,is based on this finding.
An object of the present invention is therefore to provide a process for producing petrochemicals, using a metallosilicate catalyst that comprises a metallosilicate having a main cavity defined by a ten-oxygen-membered ring and that can increase the activity of various chemical reactions.
One aspect of the present invention is a process for producing 2,6-dimethylnaphthalene by subjecting 2,7-dimethylnaphthalene to an isomerization reaction, wherein the isomerization reaction is carried out by the use of a metallosilicate catalyst that comprises a metallosilicate having a main cavity defined by a ten-oxygen-membered ring, that is in the form of aggregates of fine crystals of the metallosilicate, the external surface area of the aggregate as calculated from t-plot analysis made in the nitrogen adsorption method being 25 m
2
/g or more, and that has been treated to inactivate acid centers present on the external surfaces of the fine crystals until the rate constant basic value N becomes 0.5 or less.
DETAILED DESCRIPTION OF THE INVENTION
Metallosilicate Catalyst
The metallosilicate catalyst for use in the present invention is a metallosilicate catalyst that comprises a metallosilicate having a main cavity defined by a ten-oxygen-membered ring, that is in the form of aggregates of fine crystals of the metallosilicate, the external surface area of the aggregate as calculated from t-plot analysis made in the
Inui Tomoyuki
Kubota Osamu
Pu Shu Bin
Tsutsui Toshio
Wakabayashi Masataka
Dang Thuan D.
Fuji Oil Company Ltd.
Wenderoth Lind & Ponack LLP
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