This PTC patent has MANY interesting practical process development aspects.
The inventor impressively produced diazomethane in a solvent-free continuous PTC process in 92.7% yield. A previous PTC patent (US 5,817,778) used PTC to enhance the production rate of diazomethane, but that prior art used a solvent to prevent detonation of the diazomethane by maintaining the right material ratio in the vapor within safe limits. This current PTC process uses nitrogen to maintain the vapor ratios within safe limits. The new patent eliminates the need for a distillation to separate the solvent, which otherwise adds another unit operation that poses its own safety challenge.
The process was impressively demonstrated on a scale of 27 kg/hour feed of “Liquizald” (N-nitroso- beta-methylaminoisobutyl methyl ketone; reported to be advantageous over Diazald for cost, stability and availability). When using 2 mole% TBAB and adjusting the nitrogen flow rates (subsurface and into headspace), the inventor achieved no accumulation of Liquizald that had a half life of 8 minutes at 10 C at the feed rate of 27 kg/hr. The diazomethane product was obtained in a 10% (v/v) stream in nitrogen that was isolated with a gas-liquid separator and packed scrubber tower.
In addition, the mesityl oxide byproduct was recycled to Liquizald by the addition of methylamine, acidification by phosphoric acid (that does not contaminate the organic phase like acetic acid used in other patents) and treatment sodium nitrite.
Yet another interesting aspect of this patent is the reduction of the “induction time” to start this hydroxide ion initiated reaction at higher temperatures that was cited to be consistent with that first reported by me (Marc Halpern) in 1983 in J. Org. Chem. and in my Ph.D. thesis.
This PTC patent is an excellent example of a well-thought out process development project.
Now contact Marc Halpern of PTC Organics, the originator of the series of publications and Ph.D. thesis entitled “Hydroxide Ion Initiation Reactions Using Phase-Transfer Catalysis: Mechanism and Applications” in order to achieve the lowest cost, highest performance green chemistry for your company.
