Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By double-bond-shift isomerization
Reexamination Certificate
2000-06-06
2001-07-17
Wood, Elizabeth D. (Department: 1755)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By double-bond-shift isomerization
C585S664000, C585S671000
Reexamination Certificate
active
06262326
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for preparing a spherically shaped microcomposite comprising a perfluorinated ion-exchange polymer containing pendant sulfonic acid groups and/or pendant carboxylic acid groups entrapped within and highly dispersed throughout an inorganic oxide network. Due to their high surface area and acid functionality, these spherically shaped microcomposites possess wide utility as improved solid acid catalysts.
A microcomposite comprising perfluorinated ion-exchange polymers containing pendant sulfonic acid groups and/or pendant carboxylic acid groups entrapped within and highly dispersed throughout a metal oxide network and its preparation are disclosed in WO95/19222. The microcomposites described therein are irregular shaped particles which can be subject to attrition. Attrition can lead to fines which can cause problems in certain filtering processes and columns, such as clogging, pressure build up and the generation of friction. Fines can also find their way into a final product in certain applications which is undesirable.
Canadian Patent Application No. 2,103,653 describes shaped organosiloxane polycondensates in the form of macroscopic spherical particles. The polycondensates described contain no perfluorinated ion exchange polymer.
It is an object of the present invention to provide a shaped microcomposite that possesses high catalytic activity, high attrition resistance, and better handling characteristics.
SUMMARY OF THE INVENTION
The present invention provides a process for the preparation of at least one spherically shaped porous microcomposite which comprises a perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of inorganic oxide, wherein the weight percentage of the perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to about 90 percent, and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm; said process comprising the steps of:
(a) combining a water-miscible inorganic oxide network precursor system, a water-miscible liquid composition comprising a perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups, and an organic liquid to form a two phase liquid system;
(b) agitating the two phase liquid system sufficiently to sustain a dispersion of the water-miscible phase in the shape of spheres in the organic phase;
(c) allowing the inorganic oxide network precursor system to form a network of inorganic oxide to yield at least one spherically shaped porous microcomposite having the above-described properties; and
(d) recovering the at least one spherically shaped porous microcomposite.
DETAILED DESCRIPTION
This invention is directed to a process for preparing at least one spherically shaped porous microcomposite having a diameter of about 0.1 to about 1.0 mm, a specific surface area of about 10 to about 800 m
2
/g, and a specific pore volume of about 0.2 to about 3.0 cc/g. The at least one spherically shaped microcomposite comprises a perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of inorganic oxide, wherein the weight percentage of the perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to about 90 percent. The size of the pores in the microcomposite is about 0.5 nm to about 75 nm. Preferably, the pore size is about 0.5 to about 50 nm, most preferably about 0.5 to about 30 nm.
In step (a) of the process of the present invention, a water-miscible inorganic oxide network precursor system is combined with a water-miscible liquid composition comprising a perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups, and an organic liquid to form a two phase liquid system. Although the sequence of combining the components of the two phase liquid system is not critical, preferably the water-miscible components are contacted with each other first followed by contact with the organic liquid.
The water-miscible inorganic oxide network precursor system comprises an inorganic oxide network precursor, water and optionally a catalyst.
The “inorganic oxide” signifies metallic, semimetallic or other inorganic oxide compounds, including, for example, alumina, silica, titania, germania, zirconia, alumino-silicates, zirconyl-silicates, chromic oxides, germanium oxides, copper oxides, molybdenum oxides, tantalum oxides, zinc oxides, yttrium oxides, vanadium oxides, and iron oxides. Alumina, silica, titania and zirconia are preferred, and silica is most preferred. The term “inorganic oxide network precursor” refers to an inorganic oxide precursor or an inorganic oxide initially used in the present process to yield a network of inorganic oxide in the resultant at least one spherically shaped microcomposite. Most inorganic oxide network precursors will hydrolyze and condense into the network of inorganic oxide during the course of the present process. Other inorganic oxide network precursors exist initially as an inorganic oxide, such as colloidal silica.
In the case of silica, for example, a range of silicon alkoxides can be hydrolyzed and condensed to form the network of inorganic oxide. Such inorganic oxide network precursors as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and any compounds under the class of organic alkoxides which in the case of silicon is represented by Si(OR)
4
, where R, which can be the same or different, includes methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl can be used. Also included as an inorganic network precursor is silicon tetrachloride. Further inorganic oxide network precursors comprise organically modified silica, for example, CH
3
Si(OCH
3
)
3
, PhSi(OCH
3
)
3
,where Ph is phenyl, and (CH
3
)
2
Si(OCH
3
)
2
. Other inorganic oxide network precursors include metal silicates, for example, potassium silicate, sodium silicate and lithium silicate. As an alternative to using as is, the potassium, sodium or lithium ions of these metal silicates can be removed using a DOWEX® cation exchange resin (sold by Dow Chemical, Midland, Mich.), which generates polysilicic acid which gels at slightly acid to basic pH. The use of LUDOX® colloidal silica (E. I. du Pont de Nemours and Company, Wilmington, Del.) and fumed silica (CAB-O-SIL® sold by Cabot Corporation of Boston, Mass.) which can be gelled by altering pH and adjusting the concentration of the silicon species in solution will also yield a network of inorganic oxide in the spherically shaped microcomposite of the present invention. Preferred inorganic oxide network precursors for silica are tetramethoxysilane, tetraethoxysilane and sodium silicate; and a preferred inorganic oxide network precursor for alumina is aluminum tri-secbutoxide Al(OC
4
H
9
)
3
.
The amount of water used in the inorganic oxide network precursor system of the present process is at least sufficient for the complete hydrolysis and condensation of those inorganic oxide network precursors that are not already hydrolyzed and/or condensed. Preferably, an excess amount of water is used as compared with the stoichiometrically required amount. The amount of water required for hydrolysis depends on the rate of hydrolysis of each inorganic oxide network precursor used. Generally, hydrolysis takes place more rapidly with increasing amounts of water. Hydrolysis can begin upon contact of the inorganic oxide network precursor with the water.
The amount of water needed in the inorganic oxide network precursor system when inorganic oxides, such as colloidal silica, are used as the inorganic oxide network precursor is that which is sufficient to provide a water-miscible system upon its contact with the inorganic oxide network precursor.
Optionally, the water-miscible inorganic oxide precursor system may further comprise a catalyst. Representative examples of suitable catalysts a
Harmer Mark Andrew
Sun Qun
E. I. Du Pont de Nemours and Company
Wood Elizabeth D.
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