Abstract
Two major commercial processes are in practice today to produce propylene oxide: The uncatalyzed chlorohydrin process, and the molybdenum catalyzed peroxide epoxidation. Between 1980-1990, a number of catalyst and process improvements were developed and implemented in the molybdenum-catalyzed process. At least a dozen plants exist worldwide at 8 separate locations, including Houston(2), Bayport(3), Rotterdam(2), Marseilles(2), Ulsan, Japan, Spain, and China. Together, they represent over sixty percent of the worlds production of propylene oxide. Downsteam processes associated with these plants include propylene glycols, solvents, polyethers, MTBE, styrene monomer, polystyrene, polyurethane, propylene carbonate, allyl alcohol, gamma butyrolactone, tetrahydrofaran, N-methyl pyrrolidone, and butanediol.
Process improvements include regeneration and recycle of catalysts, packed column distillation of reactive styrene monomer, development of a new, volatile molybdenum catalyst complex, discovery and elimination of isotactic polyoxypropylene, impurities caused by cationic iron catalysts, elimination of odor bodies formed from propylene oxide over catalyst scrubbers, prevention of hydrolysis during caustic wash, and identification and minimization of catalyst heavies molecules. Process contributions contributed by the author will be discussed in detail, along with commentary on the future direction of epoxidation process and catalyst technology.
Many efforts have shown promise of a new process using heterogeneous molybdenum, tungsten, and titanium for propylene oxidation. Catalysts which promote direct air oxidation of propylene have been developed, and the development of a new commercial process based on these technologies is anticipated. Extension of this technology to asymmetric epoxidation using chiral catalysts via Sharpless, Jacobsen, and Julia-Collona Technology will be briefly discussed, along with chiral separations and measurements, and application to drug intermediates.