Propylene oxide process
View Patent ↗A process for making propylene oxide from propylene is disclosed. The process comprises reacting propylene, oxygen, and hydrogen in the presence of a catalyst, a solvent, and a buffer to produce a reaction mixture comprising propylene oxide. Separation of light components from the reaction mixture gives a heavy residue comprising the buffer. The buffer is precipitated from the heavy residue by a precipitating agent.
1. A process for producing propylene oxide comprising
(a) reading propylene, oxygen, and hydrogen in the presence of a catalyst, a solvent, and a buffer to produce a reaction mixture comprising propylene oxide;
(b) separating light components from the reaction mixture to produce a heavy residue comprising the buffer;
(c) adding a precipitating agent in the heavy residue to form a mixture of buffer precipitates and a mother liquor; and
(d) separating the buffer precipitates from the mother liquor;
wherein the step (c) is operated at a temperature in the range of −10 to 25° C.
2. The process of claim 1 wherein the buffer precipitates are recycled to the reaction step.
3. The process of claim 1 further comprising separating the precipitating agent from the mother liquor and recycling the separated precipitating agent to step (c).
4. The process of claim 1 wherein step (b) comprises a distillation step to recover the solvent and an evaporation step to concentrate the heavy residue.
5. The process of claim 4 wherein the evaporation is performed by a multi-effect evaporator.
6. The process of claim 1 wherein the buffer precipitates are separated from the mother liquor by filtration.
7. The process of claim 1 wherein the buffer has a solubility of less than 0.1 g per 100 g in the precipitating agent.
8. The process of claim 1 wherein the buffer has a solubility of less than 0.01 g per 100 g in the precipitating agent.
9. The process of claim 1 wherein the buffer comprises an ammonium ion and a phosphate ion in a molar ratio of from 1:1 to 3:1.
10. The process of claim 1 wherein the precipitating agent is selected from the group consisting of propylene oxide, methanol, acetone, and mixtures thereof.
11. The process of claim 1 wherein the precipitating agent is methanol.
12. The process of claim 1 wherein step (c) is operated at a temperature in the range of 0 to 10° C.
13. The process of claim 1 wherein the catalyst comprises a transition metal zeolite and a noble metal.
14. The process of claim 1 wherein the solvent is selected from the group consisting of methanol, water, and mixtures thereof.