Continuous loop flow process for polyether polyol production
The present disclosure relates, according to some embodiments, to compositions, apparatus, methods, and systems that may be used to produce polyols, for example, polyether polyols with a narrow range of molecular weights, with little if any unsaturated byproducts, in a sustained and/or continuous reaction, with efficient heat transfer, and/or at high production rates. For example, in some embodiments, teachings of the disclosure may be used to produce polyether polyols in a continuous loop flow process. A continuous loop flow process may be practiced such that heat is effectively transferred and/or product properties (e.g., range of molecular weights) are controllable. For example, a continuous loop flow process may use one or more continuous flow loops comprising a heat exchanger, a means to move material around each loop, inlets for catalyst, monomer, initiator or starter, and an outlet for polyol product.
1. An alkoxylation process comprising:
continuously contacting a compound comprising at least one active hydrogen, a compound comprising an alkene oxide, and a double metal cyanide catalyst in a continuous flow loop under conditions that permit formation of a polyether polyol at least in part by alkoxylation;
continuously maintaining the spread in flow loop temperature equal to or less than about 5° C.; and
continuously maintaining the spread in unreacted alkene oxide concentration in the continuous flow loop at no more than about 2 weight percent.
2. A process according to claim 1 , wherein the continuously maintaining the spread in flow loop temperature equal to or less than about 5° C. further comprises continuously maintaining the spread in flow loop temperature equal to or less than about 2° C.; and
wherein the continuously maintaining the spread in unreacted alkene oxide concentration in the continuous flow loop at no more than about 2 weight percent further comprises continuously maintaining the spread in unreacted alkene oxide concentration in the continuous flow loop at no more than about 1 weight percent.
3. A process according to claim 1 , wherein the compound comprising an alkene oxide comprises a compound selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and mixtures thereof.
4. A process according to claim 1 , wherein the compound comprising at least one active hydrogen comprises a polymer of a material selected from the group consisting of ethylene glycol, propylene glycol, glycerine, 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trihydroxybutane, pentaerythritol, xylitol, arabitol, mannitol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol sucrose, sorbitol, an alkyl glucoside, and combinations thereof, the polymer having a molecular weight of from about 30 to about 900 daltons.
5. A process according to claim 1 , wherein the double metal cyanide catalyst comprises at least one metal selected from the group consisting of potassium, zinc, cobalt, iron, chromium, platinum, iridium, and combinations thereof.
6. A process according to claim 1 , wherein the double metal cyanide catalyst comprises zinc hexacyanocobaltate Zn 2 [Co(CN) 6 ] 2 .
7. A process according to claim 6 , wherein the continuously maintaining the spread in flow loop temperature equal to or less than about 5° C. further comprises continuously removing the heat of reaction from at least a portion of the continuous flow loop at a thermal energy removal rate of at least about 400 Btu/hour-cubic foot·° F.; and
wherein the continuously maintaining the spread in unreacted alkene oxide concentration in the continuous flow loop at no more than about 2 weight percent further comprises continuously recycling at least a portion of (1) the compound comprising at least two active hydrogens, (2) the compound comprising an alkene oxide, (3) the double metal cyanide catalyst, and (4) the polyether polyol through the flow loop at a recycle ratio of at least 10.
8. A process for producing a polyether polyol, the process comprising:
providing a reactor having a reactor volume equal to or greater than about 1 cubic meter, the reactor comprising
at least one continuous flow loop operable to permit the continuous flow of at least a portion of a reaction stream,
at least one monomer inlet in fluid communication with the at least one flow loop,
at least one initiator inlet in fluid communication with the at least one flow loop,
at least one catalyst inlet in fluid communication with the at least one flow loop,
at least one heat exchanger in fluid communication with the at least one flow loop and operable to remove heat of reaction from the reaction stream, and
at least one product outlet in fluid communication with the at least one flow loop and downstream of the at least one catalyst inlet;
providing a reaction stream flowing in the continuous flow loop;
admitting a monomer into the reaction stream through the at least one monomer inlet;
admitting an initiator into the reaction stream through the at least one initiator inlet;
admitting a double metal cyanide catalyst into the reaction stream through the at least one catalyst inlet under conditions that permit formation of a polyether polyol;
contacting the reaction stream with the heat exchanger under conditions that permit thermal energy to be removed from the reaction stream at a thermal energy removal rate of at least about 400 Btu/hour-cubic foot·° F.;
removing a portion of the reaction stream through the at least one product outlet; and
recirculating the remaining portion of the reaction stream around the flow loop, wherein the recycle ratio is at least about 10, the spread in monomer concentration may be equal to or less than about 5%, and the spread in flow loop temperature may be equal to or less than about 5° C.
9. A process according to claim 8 , wherein the monomer comprises a monomer selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and mixtures thereof.
10. A process according to claim 8 , wherein the initiator comprises a polymer of a material selected from the group consisting of ethylene glycol, propylene glycol, glycerine, 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trihydroxybutane, pentaerythritol, xylitol, arabitol, mannitol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, sucrose, sorbitol, an alkyl glucoside, and combinations thereof, the polymer having a molecular weight of from about 300 to about 900 daltons.
11. A process according to claim 8 , wherein the double metal cyanide catalyst comprises at least one metal selected from the group consisting of potassium, zinc, cobalt, iron, chromium, platinum, iridium, and combinations thereof.
12. A process according to claim 8 , wherein the double metal cyanide catalyst comprises zinc hexacyanocobaltate Zn 2 [Co(CN) 6 ] 2 .
13. A process according to claim 12 , wherein (a) the thermal energy removal rate is at least about 400 Btu/hour-cubic foot·° F., (b) the recycle ratio is at least about 10, (c) the spread in monomer concentration may be equal to or less than about 2%, and (d) the spread in flow loop temperature may be equal to or less than about 5° C.
14. A process according to claim 8 , wherein the reactor volume is equal to or greater than about 12 cubic meters.
15. A process according to claim 8 , wherein the providing a reaction stream flowing in the continuous flow loop further comprises providing a reaction stream flowing in the continuous flow loop with a Reynold's number of from about 1,000 to about 1,000,000.