Process for the production of glycols
A process for the production of glycols is provided, the process comprising the steps of: (i) contacting a saccharide-containing feedstock with a catalyst system in a reactor in the presence of a reaction medium, a buffer system for controlling the pH within the reactor, and hydrogen; (ii) withdrawing a reactor product stream from the reactor; (iii) separating the reactor product stream into at least a glycol product stream and a hydrocarbon heavies stream; and (iv) recycling the hydrocarbon heavies stream at least partially back to the reactor; wherein components of the buffer system withdrawn from the reactor in the reactor product stream separate with the heavies stream and are recycled therewith.
1. A process for the production of glycols comprising the steps of:
(i) contacting a saccharide-containing feedstock with a catalyst system in a reactor in the presence of a reaction medium, a buffer system for controlling the pH within the reactor, and hydrogen;
(ii) withdrawing a reactor product stream from the reactor;
(iii) separating the reactor product stream into at least a glycol product stream and a hydrocarbon heavies stream; and
(iv) recycling the hydrocarbon heavies stream at least partially back to the reactor;
wherein components of the buffer system withdrawn from the reactor in the reactor product stream separate with the heavies stream and are recycled therewith.
2. The process as claimed in claim 1 , wherein the buffer system comprises a heavy organic acid.
3. The process as claimed in claim 1 , wherein the buffer system comprises an organic acid with a pKa of from 3.0 to 4.5.
4. The process as claimed in claim 3 , wherein the buffer system comprises sodium lactate/lactic acid and/or sodium glycolate/glycolic acid.
5. The process as claimed in claim 1 , wherein buffer system in the reactor controls the pH within the range of 2.5 to 5.
6. The process as claimed in claim 1 , wherein the catalyst system comprises a first active catalytic component comprising one or more materials selected from tungsten, molybdenum, lanthanum, tin and compounds and complexes thereof and a second active catalyst component comprising one or more materials selected from transition metals from Groups 8, 9 or 10 or compounds thereof, with catalytic hydrogenation capabilities.
7. The process as claimed in claim 6 , wherein the first active catalyst component comprises one or more materials selected from the list consisting of tungstic acid, molybdic acid, ammonium tungstate, ammonium metatungstate, ammonium paratungstate, tungstate compounds comprising at least one Group I or II element, metatungstate compounds comprising at least one Group I or II element, paratungstate compounds comprising at least one Group I or II element, heteropoly compounds of tungsten, heteropoly compounds of molybdenum, tungsten oxides, molybdenum oxides and combinations thereof, and the second active catalyst component comprises of one or more of the group selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium and platinum.
8. The process as claimed in claim 1 comprising multiple reactors, wherein the buffer strength differs between reactors.
9. The process as claimed in claim 1 , wherein the amount of buffer supplied to the reactor is from 0.05 to 5 wt % based on the total weight of feedstock supplied to the reactor.
10. The process as claimed in claim 1 , wherein the glycols comprise monoethylene and monopropylene glycols.