A very interesting patent was issued to Dow Corning that compares a variety of phase-transfer catalysts for esterification performed at 120 C. The inventors were justifiably concerned by the thermal stability of conventional phase-transfer catalysts such as TBAB, so they screened more stable catalysts such as HEG Cl (see figure). As can be seen in the reaction profile graph, HEG Cl did not improve reactivity (possibly due to a co-catalysis effect of bromide from TBAB).
The inventors then screened several quaternized polyazabicyclics, such as those derived from DBU and MTBD (see structure diagram). They found that these new phase-transfer catalysts (in the bromide form) performed better than TBAB and HEG Cl.
Changing from sodium acrylate to potassium acrylate further increased reactivity. If the physical system is a PTC solid-liquid reaction, then it is possible that the potassium salt enhances the possibility of removing the acrylate anion from the solid surface more than the sodium salt.
This patent has additional interesting aspects and it is worthwhile to read it in detail.
If your company wants to improve process performance and profit using phase-transfer catalysis, now contact Marc Halpern of PTC Organics Inc to explore integrating highly specialized expertise in industrial PTC with your commercial process development goals and to increase your profit of existing PTC and non-PTC processes in production.
About Marc Halpern
Dr. Halpern is founder and president of PTC Organics, Inc., the only company dedicated exclusively to developing low-cost high-performance green chemistry processes for the manufacture of organic chemicals using Phase Transfer Catalysis. Dr. Halpern has innovated PTC breakthroughs for pharmaceuticals, agrochemicals, petrochemicals, monomers, polymers, flavors & fragrances, dyes & pigments and solvents. Dr. Halpern has provided PTC services on-site at more than 260 industrial process R&D departments in 37 countries and has helped chemical companies save > $200 million. Dr. Halpern co-authored five books including the best-selling “Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives” and has presented the 2-day course “Practical Phase-Transfer Catalysis” at 50 locations in the US, Europe and Asia.
Dr. Halpern founded the journal “Industrial Phase-Transfer Catalysis” and “The PTC Tip of the Month” enjoyed by 2,100 qualified subscribers, now beyond 130 issues. In 2014, Dr. Halpern is celebrating his 30th year in the chemical industry, including serving as a process chemist at Dow Chemical, a supervisor of process chemistry at ICI, Director of R&D at Sybron Chemicals and founder and president of PTC Organics Inc. (15 years) and PTC Communications Inc. (20 years). Dr. Halpern also co-founded PTC Interface Inc. in 1989 and PTC Value Recovery Inc. in 1999. His academic breakthroughs include the PTC pKa Guidelines, the q-value for quat accessibility and he has achieved industrial PTC breakthroughs for a dozen strong base reactions as well as esterifications, transesterifications, epoxidations and chloromethylations plus contributed to more than 100 other industrial PTC process development projects.
Dr. Halpern has dedicated his adult life to his family and to phase-transfer catalysis (in that order!).
