Prevention of gel formation during use of and preserving/regenerating activity of nafion-type polymerization catalyst

摘要

A method of suspending the manufacture of diesters of polytetramethylene ethers by polymerizing THF or the like in a reactor utilizing a solid catalyst containing sulfonic acid groups in a liquid reaction medium containing a carboxylic acid with carboxylic acid anhydride (e.g., acetic acid/acetic anhydride) as molecular weight control agents involving the stopping of the addition of reactant THF and carboxylic acid anhydride and simultaneously increasing the concentration of carboxylic acid in said reactor to sustain and preserve catalyst activity. Also, a spent solid acid catalyst containing sulfonic acid catalytic reactive sites deactivated from sustained use during such ring-opening polymerization of THF can be regenerated by contacting the spent catalyst with a solution of THF and carboxylic acid for a time sufficient to convert any alkylated sulfonic acid reactive site to the reactive sulfonic acid site. In both the suspending of polymerization and regeneration of spent catalyst, a 7 weight percent or greater solution of acetic acid in THF has been found to be effective in preserving/restoring catalyst activity.