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Abstract

A method of making a low-fluoride reactive PIB composition includes in one embodiment: a) providing an isobutylene-enriched C4 feedstock by way of blending a first mixed C4 feedstock with a second feedstock having a lower LB/IsoB index; (b) feeding the isobutylene-enriched C4 feedstock to a polymerization reactor with a catalyst complex comprising BF₃ and a modifier selected from alcohols, ethers and mixtures thereof; (c) polymerizing the isobutylene-enriched C4 feedstock in the reactor while maintaining the reactor at a temperature above −40° C. and most preferably above −15° C. and utilizing a residence time less than 45 minutes to produce a crude PIB composition in a polymerization mixture; and (d) recovering a purified PIB composition from the polymerization mixture having a molecular weight, Mn, from 250 to 5000 Daltons and an alpha vinylidene content of at least 50 mol %. The crude PIB composition suitably has a fluoride content of less than 100 ppm and the purified PIB composition has a fluoride content of less than 20 ppm. In another aspect, ammonium salts are used to neutralize the catalyst and fluoride salts are sublimed from the product at elevated temperatures.

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First Claim