Over the past 15 years, PTC has been used in the quest to achieve low-sulfur diesel as regulations across the globe call for lower and lower sulfur levels. A patent was recently issued to Yen and Wan at University of Southern California for work funded by the US Navy that uses phase-transfer catalysis and hydrogen peroxide in a portable desulfurization unit.
The major sulfur components are methylated benzothiophenes and methylated dibenzothiophenes. Iron-based “Fenton” catalysts are best for desulfurization of crude oil while tungsten-based catalysts were reported to be best for desulfurization of diesel.
Similar to the oxidation discussed in the PTC Tip of the Month above, agitation appears to play an important role in this oxidative desulfurization. The inventors employed ultrasound in a continuous flow reactor that is portable.
One of the most interesting aspects from our standpoint is a comparison of phase-transfer catalysts, shown in the diagram. The inventors found that more carbon atoms on the PTC quat are better than less carbon atoms. Thus, (C18H37)4N Br > Oct4N Br > Bu4N Br. However, replacing the bromide counterion with fluoride gave a bigger effect than adding 40 extra carbons (10 X 4 chains). So, the preferred phase-transfer catalyst was reported to be tetraoctyl ammonium fluoride. These catalysts are EXTREMELY expensive and the patent notes that their recovery is crucial, including the transition metals (“The commercial viability of UAOD processes that uses transition metal catalysts depends on the efficiency of catalyst recovery. “)
If you or your company can benefit from achieving higher process performance in a shorter development time for this PTC reaction or any other reaction, by having access to the best PTC expertise available, NOW CONTACT Marc Halpern to inquire about using phase-transfer catalysis to achieve low-cost high-performance green chemistry. Remember, PTC excels in thousands of reactions in more than 30 reaction categories including strong base reactions, nucleophilic substitutions, oxidations and reductions
If you’re not sure if PTC can help your reaction, now fill out the PTC Project Evaluation Form and E-mail a scanned copy to Marc Halpern or send it by fax to Dr. Halpern at +1 856-222-1124. If your company does not have a secrecy agreement with PTC Organics Inc. already in place, please use “R-groups” instead of the exact chemical structures.
