Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Sulfur or compound containing same
Reexamination Certificate
2000-01-28
2001-12-04
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Sulfur or compound containing same
C502S222000, C502S223000, C502S325000, C502S339000, C502S349000
Reexamination Certificate
active
06326328
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a solid acid catalyst which exhibits a high activity in various acid-catalyzed reactions and is easily handleable and excellent in stability in service, and processes for the preparation of the same.
BACKGROUND ART
In the chemical industry there are many known reactions, such as alkylation, esterification and isomerization, etc., requiring an acid catalyst. Up to this time, such reactions have been conducted by the use of acid catalysts such as sulfuric acid, aluminum chloride, hydrogen fluoride, phosphoric acid and p-toluenesulfonic acid. However, these acid catalysts have the property of corroding metals, which make it indispensable to use an expensive corrosion-resistant material or to apply an anticorrosion treatment. Further, the acid catalysts have difficulty in separation from the reaction mixture and also had such a significant environmental problem that the use of the catalysts was indispensably accompanied with waste acid disposal, which involved alkali cleaning and other troublesome steps. Additionally, the catalysts were very difficult to re-use.
Solid acid catalysts containing a sulfate group have been proposed in order to solve the above problems, the catalysts being produced by bringing a hydroxide or hydrated oxide of a Group IV metal of the periodic table into contact with a solution containing a sulfureous component and calcining the hydroxide or hydrated oxide thus treated at 350 to 800° C.(Japanese Patent Publication No. 59-6181). These solid acid catalysts exhibit an acid strength higher than that of 100% sulfuric acid (Hammett acidity function H
0
: −11.93). These catalysts have high catalytic performance for various acid-catalyzed reactions by virtue of the high acid strength, and are advantageous in that the corrosiveness is low, that they are easily separable from the reaction mixture and can dispense with waste acid disposal, and that they can be re-used. Accordingly, these solid acid catalyst are expected to substitute for the acid catalysts of the prior art in various reactions.
Further, it has already been known to the public that a catalyst produced by calcining zirconia gel containing a sulfureous component and incorporating platinum into the resulting zirconia exhibits high activity in the isomerization of hydrocarbons (U.S. Pat. No. 3,032,599).
Modifications of the above process for the preparation of the metal oxide catalyst mainly used for isomerization and containing a platinum-group metal and a sulfureous component are disclosed in Japanese Patent Publication Nos. 5-29503, 5-29504, 5-29505 and 5-20506. They include a modification comprising omitting the step of calcining between the step of treatment with a sulfureous compound and the step of deposition of a platinum-group metal, another modification comprising conducting the treatment with a sulfureous compound and the deposition of a platinum-group metal in reverse order, and still another modification comprising varying the sulfureous compound to be used.
Meanwhile, it is also known that a solid acid catalyst prepared by adding a sulfureous compound to aluminum hydroxide or aluminum oxide and calcining the obtained mixture exhibits an acid strength higher than that of 100% sulfuric acid (Japanese Patent Laid-Open No. 5-96171, and Arata, “Trends in Physical Chemistry”, Vol.2, Section 1 (1991)).
Japanese Patent Publication No. 6-29199 discloses an isomerization catalyst prepared by incorporating both of at least one metal selected from among Ni, Ru, Rh, Pd and Pt and a sulfate group into a hydroxide or oxide of a Group IV metal selected from among Si, Ti, Zr and Sn and/or a hydroxide or oxide of aluminum. Further, a catalyst comprising a Zr(OH)
4
/Al(OH)
3
powder produced by coprecipitation and both of platinum and sulfuric acid supported on the powder is disclosed in Example 6 of this patent.
DISCLOSURE OF INVENTION
Although the above solid acid catalysts are generally powdery ones, a shaped catalyst, for example, a granular one having a diameter of about 1 mm is necessary for industrial chemical reactions. However, there has not been reported any process by which a shaped solid acid catalyst satisfying the performance requirements for a catalyst can be prepared.
The present invention has been made to solve the above problems, and aims at providing a solid acid catalyst containing a sulfureous component which, in spite of its being shaped, exhibits a sufficiently high activity and has a crushing strength high enough for practical use, and processes for the preparation of the same.
The inventors of the present invention have found that a shaped catalyst having a high catalytic activity beyond expectations can be prepared by adding pseudoboehmite as a binder to zirconium hydroxide as a solid acid precursor, adding ammonium sulfate, shaping the mixture thus obtained, and calcining the shaped material and that another catalyst prepared by making chloroplatinic acid additionally supported on this shaped catalyst and calcining the resulting catalyst exhibits contrary to our expectations a hydrocarbon-isomerizing activity higher than that of a powdery zirconia catalyst containing platinum and a sulfureous component. Further, they have also found that catalysts prepared by incorporating these catalysts with boron oxide and/or phosphorus oxide exhibit excellent activity. The present invention has been accomplished on the basis of these findings.
Our further studies have revealed that pseudoboehmite alumina contributes to the stabilization of tetragonal zirconia. For example, when noncrystalline zirconium hydroxide or hydrated zirconia was calcined at 600° C., it crystallizes and most of the zirconia thus formed was monoclinic. However, when a compound prepared by kneading such a zirconium hydroxide or hydrated zirconia with powdery pseudoboehmite was calcined at 600° C., the zirconia crystals formed with the progress of crystallization were tetragonal and no monoclinic crystals were found. Thus, the addition of pseudoboehmite alumina is effective in stabilizing tetragonal zirconia. One of the causes of this effect is thought to be that pseudoboemite powder present among the crystalline particles of zirconia hinders the crystal growth of zirconia, though most of the causes have not been elucidated as yet.
Besides pseudoboemite alumina, many compounds are known to be effective in stabilizing tetragonal crystals of zirconia. However, many of the compounds are basic and therefore unsuitable from the standpoint of the requirements for the catalyst, particularly acidity. As described above, a solid acid catalyst prepared by adding a sulfureous compound to aluminum hydroxide or aluminum oxide and calcining the obtained mixture exhibits an acid strength higher than that of 100% sulfuric acid, and pseudoboehmite alumina exhibits extremely excellent shapability. Accordingly, it is essential in the present invention that the compound to be mixed with zirconia is alumina, with pseudoboehmite being optimum. The high activity of the catalyst according to the present invention is thought to result from the effects of pseudoboehmite.
Thus, the present invention relates to a process for the preparation of a solid acid catalyst, which comprises
(a) kneading a hydroxide and/or hydrated oxide of aluminum, a hydroxide and/or hydrated oxide of zirconium, and a sulfureous compound,
(b) shaping the kneaded mixture, and
(c) calcining the shaped material at such a temperature as to give tetragonal zirconia,
or a process for the preparation of a solid acid catalyst, which comprises
(a) kneading a hydroxide and/or hydrated oxide of aluminum, a hydroxide and/or hydrated oxide of zirconium, and a sulfureous compound,
(b) shaping the kneaded mixture,
(c) calcining the shaped material at such a temperature as to give tetragonal zirconia,
(d) making a Group 8,9 or 10 metal component supported on the calcined material, and
(e) calcining the resulting material at 300 to 700° C.
In particular, it is preferable to use aluminum oxide hydrate having a boehmite structure as the hy
Flynn ,Thiel, Boutell & Tanis, P.C.
Griffin Steven P.
Ildebrando Christina
Japan Energy Corporation
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