Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Utility Patent
1999-09-21
2001-01-02
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S168000, C502S402000, C502S407000, C502S158000
Utility Patent
active
06169053
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns catalysts comprising chemically modified perfluorinated ion-exchange microcomposites, processes for their preparation and their use as catalysts in chemical processes.
TECHNICAL BACKGROUND
K. A. Mauritz et al., Polym. Mater. Sci. Eng. 58, 1079-1082 (1988), in an article titled “Nafion-based Microcomposites: Silicon Oxide-filled Membranes”, discuss the formation of micro composite membranes by the growth of silicon oxide microclusters or continuous silicon oxide interpenetrating networks in pre-swollen “NAFION®” sulfonic acid films. NAFION® is a registered trademark of E. I. du Pont de Nemours and Company.
U.S. Pat. No. 4,038,213 discloses the preparation of catalysts comprising perfluorinated ion-exchange polymers containing pendant sulfonic acid groups on a variety of supports.
The catalyst utility of perfluorinated ion-exchange polymers containing pendant sulfonic acid groups, supported and unsupported has been broadly reviewed: G. A. Olah et al., Synthesis, 513-531 (1986) and F. J. Wahler, Catal. Rev.-Sci. Eng., 1-12 (1986).
WO 95/19222 describes a porous microcomposite comprising a perfluorinated ion-exchange microcomposite containing pendant sulfonic acid and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide. These catalysts are differentiated from NAFION® supported catalysts in that by virtue of the preparation of the microcomposite catalyst, the polymer becomes intimately mixed with a metal oxide precursor in solution, and thus becomes thoroughly entrapped and highly dispersed throughout a resulting network of metal oxide. With the polymer being mechanically entrapped within the metal oxide network and not merely on the surface of a support, as is the case in supported catalysts, the catalytic activity of these microcomposite catalysts is significantly increased.
P. J. Stang, M. Hanack and L. R. Subramian, “Perfluoroalkanesulfonic Esters: Methods of Preparation and Applications in Organic Chemistry”, Synthesis, 1982, 85-126, discuss the utility of perfluoroalkanesulfonic esters, for example, trimethylsilyl trifluoromethanesulfonate (TMSOTf), as homogeneous catalysts for a range of reactions. P. A. Procopiou, S. P. D. Baugh, S. S. Flack and G. G. A. Inglis, J. Chem. Soc., Chem. Comm., 1996, 2625 disclose the utility of TMSOTf as an effective homogeneous catalyst for the acylation of alcohols with acid anhydrides.
Although a variety of reactions can be beneficially catalyzed by the compounds and the composites cited above, there is still a need for heterogeneous catalysts of increased activity and selectivity and broader applications.
SUMMARY OF THE INVENTION
The present invention provides a silylated porous microcomposite, comprising: a perfluorinated ion-exchange polymer containing pendant groups selected from the group consisting of: sulfonic acid groups, silyl sulfonate groups, and a combination of said groups, wherein the polymer is entrapped within and highly dispersed throughout a network of inorganic oxide, said network having a plurality of silylated species bonded thereto.
The present invention also provides a process for the preparation of a silylated porous microcomposite, comprising the steps of: contacting a porous microcomposite comprising a perfluorinated ion-exchange polymer containing pendant sulfonic acid groups or pendant metal sulfonate groups, wherein said polymer is entrapped within and highly dispersed throughout a network of inorganic oxide, with a silylating agent under silylating conditions for a time sufficient to convert a plurality of hydroxyl groups of the inorganic oxide network to a silylated species and a portion of the sulfonic acid groups or metal sulfonate groups to silyl sulfonate groups.
The present invention also provides an improved method for the acylation of an alcohol with an acid anhydride, the improvement comprising using an effective amount of a catalyst composition comprising a silylated porous microcomposite comprising a perfluorinated ion-exchange polymer containing pendant groups selected from the group consisting of: sulfonic acid groups, silyl sulfonate groups, and a combination of said groups, wherein the polymer is entrapped within and highly dispersed throughout a network of inorganic oxide, said network having a plurality of silylated species bonded thereto.
DETAILED DESCRIPTION OF THE INVENTION
It is believed that key features of the present invention include the modification of a plurality of the residual hydroxyl groups of the inorganic oxide network to silylated species and optional modification of all or a portion of the pendant sulfonic acid groups of a perfluorinated ion-exchange polymer of a porous microcomposite to silyl sulfonate groups.
The present invention concerns the silylation of a porous microcomposite. By “porous microcomposite” is meant a composition comprising a perfluorinated ion-exchange polymer (PFIEP) containing pendant sulfonic acid groups, wherein said polymer is entrapped within and highly dispersed throughout a network of inorganic oxide. The PFIEP may optionally further comprise pendant carboxylic acid groups. The percentage of the perfluorinated ion-exchange polymer in the microcomposite is from 0.1 to about 90% by weight and the size of the pores in the microcomposite is about 1 nm to about 75 nm, and the microcomposite optionally further comprises pores having a size in the range of about 75 nm to about 1000 nm. Such microcomposites are described in U.S. application Ser. No. 08/574,751, filed Dec. 19, 1995 incorporated by reference herein and in the corresponding PCT publication WO 95/19222. The microcomposite can be in any size or shape to be utilized in the present invention, such as ground into particles or shaped into spheres. The PFIEP is preferably, a sulfonated NAFION® PFIEP. The weight percentage of PFIEP preferably ranges from about 5% to about 80%, most preferably from about 10% to about 15%. The inorganic oxide of the network is preferably silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide, iron oxide, or mixture thereof; most preferably silica.
The inorganic oxide network of the present modified porous microcomposite has a plurality of silylated species bonded thereto. By “having a plurality of silylated species bonded thereto” is meant that a portion of the hydroxyl groups of the inorganic oxide network, preferably at least 50% of the hydroxyl groups, most preferably at least 80% of the hydroxyl groups, are converted to a silylated species via reaction with a silylating agent, and this silylated species remains bonded to the inorganic oxide network. As is known, after formation of an inorganic oxide network, there are nunerous residual hydroxyl groups. This is because during network formation each of the inorganic atoms become constituents of a network structure via bonds to other inorganic atoms through oxygen but condensation to form these crosslinks does not go to 100% completion; there are residual, uncrosslinked hydroxyl groups. For example, in the present case where the inorganic oxide of the network is silica, silanol (Si—OH) groups can be found as part of the network, and it is a plurality of the hydroxyl (—OH) groups of these silanols that are converted to silylated species which remain bonded to the network.
By “silylated species” is meant a group having the formula —O)
q
Si(R
1
)
4-q
, wherein oxygen is bonded to the inorganic oxide network, each R
1
is independently selected from the group consisting of chloride, and a monovalent hydrocarbon radical, preferably C
1
to C
12
alkyl or aryl, such as methyl, ethyl, propyl, butyl, and phenyl; most preferably methyl; and q is 1, 2 or 3. Thus, silylated species also include those instances where bridging and/or crosslinking has occurred during silylation of the precursor hydroxyl groups.
The pendant groups of the PFIEP of the silylated porous microcomposite can be sulfonic acid groups, silyl sulfonate groups, or a combination of these two groups. The sulfonic acid groups a
Harmer Mark Andrew
Sun Qun
E. I. Du Pont de Nemours and Company
Wood Elizabeth D.
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