Processes for making ethylene glycol and/or propylene glycol from aldose- and/or ketose-yielding carbohydrates with integrated tungsten catalyst recovery
Integrated processes are disclosed for the catalytic conversion of carbohydrate to ethylene glycol and/or propylene glycol using a homogeneous, tungsten-containing retro-aldol catalyst. In these processes, the carbohydrate is subjected to retro-aldol conversion and hydrogenation to provide a reaction product containing ethylene glycol and/or propylene glycol, other reaction process including organic acids, itols and tungsten species. Ethylene glycol and propylene glycol are separated from the reaction product for purification, and at least a portion of the remaining fraction is subjected to ion exclusion chromatography to provide an eluant containing tungsten species and a subsequent eluant containing organic acids and a substantially reduced concentration of tungsten species. At least a portion of the eluant containing tungsten species can be recycled for reuse directly or with intervening unit operations to enhance the catalytic activity of the tungsten species. The organic-containing fraction can be subjected to one or more unit operations to provide salable products or subjected to selective hydrogenolysis to lower glycols.
1. A catalytic process for producing a lower glycol comprising at least one of ethylene glycol and propylene glycol from a carbohydrate-containing feed that comprises at least one of aldose- and ketose-yielding carbohydrate, said process comprising:
(a) continuously or intermittently supplying the feed to a reaction zone having therein dissolved tungsten compounds at least one of which is homogeneous, tungsten-containing retro-aldol catalyst and at least one heterogeneous hydrogenation catalyst, said liquid medium being at catalytic conversion conditions including the presence of dissolved hydrogen, to produce a reaction product containing said lower glycol and one or more higher boiling point coproducts comprising sorbitol, erythritol, threitol and glycerin;
(b) continuously or intermittently withdrawing liquid medium that contains reaction product and dissolved tungsten compounds from the reaction zone;
(c) subjecting at least a portion of the withdrawn liquid medium to one or more unit operations to remove at least a portion of the lower glycol in a separated fraction and provide a retained liquid phase containing dissolved tungsten compounds and higher boiling point coproducts with a mass ratio of higher boiling coproducts to tungsten compounds calculated as the metal of greater than about 4:1; and
(d) contacting at least a portion of the retained liquid phase with an ionic resin for ion exclusion chromatography, to provide a first eluted fraction containing dissolved tungsten compounds and a mass ratio of higher boiling coproducts to tungsten compounds calculated as the metal of less than about 1:1, and contacting the ionic resin with sufficient solvent to provide at least one subsequent eluted fraction containing one or more higher boiling point coproducts and a lower concentration of tungsten compounds than that in the retained liquid phase.
2. The process of claim 1 wherein at least about 90 mass percent of the tungsten compounds contained in the retained liquid phase contacted with the ionic resin are in the first eluted fraction.
3. The process of claim 1 wherein the portion of the retained liquid phase contacted with the cationic resin is a purge stream.
4. The process of claim 1 wherein at least a portion of the first eluted fraction is recycled to step (a).
5. The process of claim 4 wherein the pH of the recycled, first eluted fraction is provided at between about 6.5 and 8 before being passed to step (a).
6. The process of claim 5 wherein at least a portion of the tungsten compounds in the recycled, first eluted fraction is half neutralized tungstic acid.
7. The process of claim 1 wherein at least a portion of the at least one subsequently eluted fraction containing one or more higher boiling point coproducts is subjected to hydrogenolysis conditions to provide at least one of ethylene glycol and propylene glycol.
8. The process of claim 1 wherein the ionic resin comprises cationic resin.
9. The process of claim 8 wherein the cationic resin comprises polystyrene sulfonate strong cation exchange resin.
10. The process of claim 1 wherein the ionic resin has a degree of crosslinking of at least 6 percent.
11. The process of claim 10 wherein the ionic resin has a degree of crosslinking of at least 8 percent.
12. The process of claim 1 wherein step (d) is conducted as a simulated moving bed.
13. The process of claim 1 wherein the one or more unit operations of step (c) comprise a vapor liquid separation.