Process for manufacturing propylene oxide
View Patent ↗A process for the recovery of molybdenum catalyst from the epoxidation reaction product of olefins with organic hydroperoxides. The active form of the glycol-molybdate epoxidation catalyst is removed from the process stream with an anion ion exchange resin. The ion exchange resin can be either a weak base or strong base type. The preferred embodiment of the invention produces a concentrated epoxidation catalyst in the “ammonium” form that is suitable for recycle to the catalyst preparation vessel. The ammonia form is converted into the active form by evaporating the water and ammonia from the recovered catalyst in the presence of a glycol. The preferred configuration of the ion exchange process is a “Lead-Lag” system. Two vessels will be in service while the third is in the regeneration mode recovering the epoxidation catalyst. A fourth polishing vessel can also be included as a “guard bed” to prevent leakage of the molybdate catalyst into the process stream. Since the ion exchange kinetics are slow compared to an aqueous system, the preferred embodiment uses a fractal fluid distribution system.
1. In a process for the manufacture of propylene oxide by the epoxidation reaction in a tertiary butyl alcohol stream (TBA) of propylene with tertiary butyl hydroperoxide (TBH) in the presence of a molybdenum catalyst in the form of a glycol-molybdate complex to produce a reaction product stream comprising unreacted propylene, propylene oxide, tertiary butyl alcohol, unreacted TBH, molybdenum catalyst in the form of a glycol-molybdate complex and impurities, the improvement comprising the steps of:
(a) separating the reaction product stream into a recycled propylene stream, a propylene oxide stream, and a TBA process stream;
(b) passing the TBA process stream through an ion exchange process comprising a weak base anion ion exchange resin to remove substantially all the molybdenum catalyst; and
(c) regenerating the ion exchange resin with ammonium hydroxide, whereby the molybdenum catalyst is regenerated from the anion ion exchange resin in the ammonium form.
2. The improved process of claim 1 , comprising the additional steps following step (c) of converting the molybdenum catalyst in the ammonium form to the active form by evaporating water and ammonia in the presence of a glycol to produce a glycol-molybdate complex and recycling the glycol-molybdate catalyst to the epoxidation reaction.
3. The improved process of claim 2 wherein the glycol is selected from the group consisting of ethylene glycol and propylene glycol.
4. The improved process of claim 1 wherein the ion exchange process of step (a) is configured in a lead-lag configuration.
5. The improved process of claim 1 wherein the ion exchange process comprises a fractal fluid distribution system for distributing the TBA process stream into the anion ion exchange resin.