As we teach in our 2-day course “Industrial Phase-Transfer Catalysis,” benzyl trimethyl ammonium chloride, BTMAC, was one of the first phase-transfer catalysts used in large scale commodity chemicals. BTMAC has been used in quantities of more than 500 metric tons per year since the 1980’s in the manufacture of aryl glycidyl ethers (such as bisphenol A diglycidyl ether) for epoxy resins. When I spoke with the chief scientist of an epoxy resin manufacturer in 1987 and I noted that BTMAC is likely not the optimal catalyst for such glycidyl etherifications, he said that they knew that however, it would be impractical to requalify the epoxy resin products used by thousands of customers just to optimize the structure of the phase-transfer catalyst.
BTMAC is extremely easy and inexpensive to produce. Simply mix an aqueous solution of trimethylamine with benzyl chloride and after a sufficient reaction time and temperature, distill off the water to meet the specification and ship what’s left in the reactor.
Last week, a patent was issued that cited BTMAC as the catalyst to produce the triglycidyl ether of 1,2,3-trihydroxybenzene. Unlike the early Dow Chemical patents using BTMAC for the reaction of bisphenol A (deprotonated with NaOH) with epichlorohydrin (long since expired), the reaction shown in the diagram used the chloride of BTMAC to catalyze the formation of the ring opened chlorohydrin followed by a separate reaction using NaOH to perform the ring closing. The 2-step process of ring opening of epichlorohydrin by a nucleophile followed by ring closing to the epoxide using base, is used for aliphatic glycidyl ethers.
Phosphonium salts are used as phase-transfer catalysts to build molecular weight of epoxy resins. In other words, two different phase-transfer catalysts are used in the epoxy resin industry.
If your company needs to develop optimized low-cost high-performance green chemistry processes for the manufacture of epoxy resins or for any nucleophilic substitutions, now contact Marc Halpern of PTC Organics to integrate 4.5 decades of highly specialized expertise in industrial phase-transfer catalysis with your commercial goals.
