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 and a solvent to produce a reaction mixture comprising propylene oxide. Separation of propylene, oxygen, hydrogen, and propylene oxide from the reaction mixture results in a residual mixture comprising methanol. A portion of the residual mixture is recycled to the reaction. A portion of the residual mixture is distilled to generate a distilled methanol stream, which is recycled to the reaction.
1. A process for producing propylene oxide comprising
(a) reacting propylene, oxygen, and hydrogen in the presence of a catalyst and methanol to produce a reaction mixture comprising propylene oxide;
(b) separating propylene, oxygen, hydrogen, and propylene oxide from the reaction mixture to generate a residual mixture comprising methanol:
(c) recycling from 10 to 30 wt % of the residual mixture to step (a);
(d) separating a portion of the residual mixture to generate a methanol stream; and
(e) recycling the methanol stream to step (a);
wherein the reaction mixture comprises methanol and water with a methanol to water weight ratio greater than 7:3.
2. The process of claim 1 wherein the methanol stream comprises at least 95 wt % methanol.
3. The process of claim 1 wherein the methanol stream comprises at least 98 wt % methanol.
4. The process of claim 1 wherein the reaction mixture comprises methanol and water with a methanol to water weight ratio greater than 8:2.
5. The process of claim 1 wherein step (a) is performed in the presence of a buffer.
6. The process of claim 5 wherein the buffer comprises an ammonium ion and a phosphate ion with an ammonium to phosphate molar ratio of from 1:1 to 3:1.
7. The process of claim 1 wherein the catalyst comprises a transition metal zeolite and a noble metal.
8. The process of claim 7 wherein the transition metal zeolite is titanium silicalite-1.
9. The process of claim 7 wherein the noble metal is selected from the group consisting of palladium, platinum, gold, rhenium, silver, and mixtures thereof.