Process for converting glycerin into propylene glycol
A process to convert glycerin into propylene glycol and purifying the produced propylene glycol is described. The glycerin-based propylene glycol production requires only one process step compared to petroleum/natural gas-based propylene glycol production requires multiple process steps, and thus represents a cost savings.
1. A process for converting glycerin into propylene glycol comprising the steps of:
preheating a feed mixture comprising glycerin, hydrogen and methanol in a reactant heater;
passing the heated feed mixture to a reactor;
separating the reactor effluent into a vapor phase stream and a liquid phase stream;
condensing the vapor phase stream into a condensed liquid;
recycling the condensed liquid to the reactor; and
distilling the liquid phase stream to obtain purified propylene glycol.
2. The process according to claim 1 , wherein the reactor is a fixed bed reactor.
3. The process according to claim 1 , wherein the reactor is operated at a temperature of 150° C.-240° C.
4. The process according to claim 1 , wherein the reactor is operated at a pressure of 20-80 atmospheres.
5. The process according to claim 1 , further comprising hydrogenating the heated feed mixture in the reactor.
6. The process according to claim 5 , wherein the hydrogenating is carried out by a supported catalyst in the fixed bed reactor.
7. The process according to claim 6 , wherein the supported catalyst is a metal or metal oxide catalyst.
8. The process according to claim 7 , wherein the supported catalyst comprises copper.
9. The process according to claim 1 , further comprising mixing the condensed liquid with a glycerin feed.
10. The process according to claim 1 , wherein the liquid phase stream is depressurized and cooled prior to distilling.
11. The process according to claim 1 , wherein the liquid phase stream is distilled in multiple distillation columns.