Lewis Acids have been widely used as catalysts in carbocationic polymerization processes to catalyze the polymerization of monoolefins. Examples of Lewis Acid catalysts include AlCl.sub.3, BF.sub.3, BCl.sub.3, TiCl.sub.4, Al(C.sub.2 H.sub.5).sub.3, Al(C.sub.2 H.sub.5).sub.2 Cl, and Al(C.sub.2 H.sub.5)Cl.sub.2. Such carbocationic polymerization catalysts have many advantages, including high yield, fast reaction rates, good molecular weight control, and utility with a wide variety of monomers. However, conventional carbocationic polymerization processes typically employ Lewis Acid catalysts in unsupported form. Hence, these catalysts, typically, cannot be recycled or reused in a cost effective manner.
In a typical carbocationic polymerization process, such as the carbocationic polymerization of isobutylene, a catalyst feedstream in a liquid or gaseous form and a monomer feedstream are fed simultaneously into a conventional reactor. In the reactor, the streams are intermingled and contacted under process conditions such that a desired fraction of the monomer feedstream is polymerized. Then, after an appropriate residence time in the reactor, a discharge stream is withdrawn from the reactor. The discharge stream contains polymer, unreacted monomer and catalyst. In order to recover the polymer, the catalyst and unreacted monomer must be separated from this stream. Typically, there is at least some residue of catalyst in the polymer which cannot be separated. After separation, the catalyst is typically quenched and neutralized. The quenching and neutralization steps tend to generate large quantities of waste which must typically be disposed of as hazardous waste.
The recycling or reuse of Lewis Acid catalysts used in polymer processes is difficult because of the chemical and physical characteristics of these catalysts. For example, most Lewis Acid catalysts are non-volatile and cannot be distilled off. Other catalysts are in a solid particulate form and must be separated from the polymer stream by physical separation means. Some Lewis Acid catalysts are gaseous, such as BF.sub.3. The gases can be recycled and reused, but with considerable difficulty, by utilizing gas-liquid separators and compressors.
There have been several attempts made to support Lewis Acid catalysts on the surface of inorganic substrates such as silica gel, alumina, and clay. Although these approaches are somewhat successful in recycling the Lewis Acid catalysts, there are several disadvantages associated with their use. One particularly strong disadvantage is that these approaches to supported catalysts generally produce only low molecular weight oligomers. Another disadvantage is that the catalysts (supported on inorganic substrates) typically leach out during the reaction since the catalysts tend to not be firmly fixed to the supporting substrates.
Attempts to support Lewis Acid catalysts can be characterized as falling into two basic classes; namely, those which rely on physical adsorption and those wherein the Lewis Acid chemically reacts with the support.
U.S. Pat. No. 3,925,495 discloses a catalyst consisting of graphite having a Lewis Acid intercalated in the lattice thereof.
U.S. Pat. No. 4,112,011 discloses a catalyst comprising gallium compounds on a suitable support such as aluminas, silicas and silica aluminas.
U.S. Pat. No. 4,235,756 discloses a catalyst comprising porous gamma alumina impregnated with an aluminum hydride.
U.S. Pat. No. 4,288,449 discloses chloride alumina catalysts.
U.S. Pat. Nos. 4,734,472 and 4,751,276 disclose a method for preparing functionalized (e.g., hydroxy functionalized) alpha-olefin polymers and copolymers derived from a borane containing intermediate.
U.S. Pat. No. 4,167,616 discloses polymerization with diborane adducts or oligomers of boron-containing monomers.
U.S. Pat. No. 4,698,403 discloses a process for the preparation of ethylene copolymers in the presence of selected nickel-containing catalysts.
U.S. Pat. No. 4,638,092 discloses organo-boron compounds with strong aerobic initiator action to start polymerizations.
U.S. Pat. No. 4,342,849 discloses novel telechelic polymers formed by hydroborating diolefins to polyboranes and oxidizing the polymeric boranes to form the telechelic dehydroxy polymer. No use of the resulting polymer to support Lewis Acid catalysts is disclosed.
U.S. Pat. No. 4,558,170 discloses a continuous cationic polymerization process wherein a cocatalyst is mixed with a monomer feedstream prior to introduction of the feedstream to a reactor containing a Lewis Acid catalyst.
U.S. Pat. Nos. 4,719,190, 4,798,190 and 4,929,800 disclose hydrocarbon conversion and polymerization catalysts prepared by reacting a solid adsorbent containing surface hydroxyl groups with certain Lewis Acid catalysts in halogenated solvent. The only disclosed adsorbents are inorganic; namely, silica alumina, boron oxide, zeolite, magnesia and titania.
U.S. Pat. No. 4,605,808 discloses a process for producing polyisobutene using a complex of boron trifluoride and alcohol as catalyst.
U.S. Pat. No. 4,139,417, discloses amorphous copolymers of monoolefins or of monoolefins and nonconjugated dienes with unsaturated derivatives of imides. In the preparation of the polymer the imide is complexed with a Lewis Acid catalyst.
Japanese Patent Application No. 188996/1952 (Laid Open No. J59080413A/1984) discloses a process for preparing a copolymer of an olefin and a polar vinyl monomer which comprises copolymerizing an olefin with a complex of the polar vinyl monomer and a Lewis acid.
European Patent Application No. 87311534.9 (Publication No. EPA 0274912) discloses polyalcohol copolymers made using borane chemistry.
T. C. Chung and D. Rhubright, Macromolecules, Vol. 24, 970-972, (1991) discloses functionalized polypropylene copolymers made using borane chemistry.
T. C. Chung, Journal of Inorganic and Organometallic Polymers, Vol. 1, No. 1, 37-51, (1991) discloses the preparation of polyboranes and borane monomers.
U.S. Pat. No. 4,849,572 discloses a process for preparing polybutenes having enhanced reactivity using a BF.sub.3 catalyst. Polybutene is produced which has a number average molecular weight in the range of from 500 to 5,000. The polymer has a total terminal double-bond content of at least 40% based on total theoretical unsaturation of the polybutene. The polybutene contains at least 50% by weight isobutylene units based on the polybutene number average molecular weight. The process is accomplished by contacting a feed supply comprising at least 10% by weight isobutylene based on the weight of the feed with a BF.sub.3 catalyst under conditions to cationically polymerize the feed in liquid phase to form polybutene. The polymer is immediately quenched with a quench medium sufficient to deactivate the BF.sub.3 catalyst.
There has been a continuous search for catalysts having high efficiency which can be recycled or reused in cationic polymerization processes. The present invention was developed pursuant to this search.