A patent just issued last month to Sachem, one of the most veteran manufacturers of high purity quaternary ammonium phase-transfer catalysts, that describes how to inhibit color formation of quat hydroxides in non-aqueous solvents (glycols). Sachem has been a leader in the commercial supply of quat hydroxides, especially those used in the manufacture of semiconductors.
Quat hydroxides that contain at least one ethyl or higher alkyl group, can undergo Hofmann Elimination. Quat hydroxides are relatively stable to this decomposition at room temperature, though decomposition is possible with extended shelf life if not stored in a cool environment. It is speculated that the amine liberated by this quat decomposition mechanism can oxidize when exposed to air over time and create color compounds.
Sachem inventors found that the addition of small amount of hydantoin (10-5000 ppm) to non-aqueous solutions of quat hydroxide (20 wt%-50 wt%) containing less than 0.5 wt% water, can effectively inhibit color formation. Engel, T.; Van Lier, A.; (Sachem) US Patent 9,944,853, 17-Apr-2018
It is important to note that hydantoin (imidazolidine-2,4-dione) has two active N-H bonds, so if the quat hydroxide is being used to perform base-promoted alkylations or other reactions that may be affected by active N-H groups, small amounts of impurities may be formed by the reaction of hydantoin with reaction components unless the hydantoin is removed prior to the reaction.
Now contact Marc Halpern of PTC Organics if your company needs expert input for choosing the optimal phase-transfer catalyst for your commercial PTC application.