Integrated process for production of glycerol carbonate (4-hydroxymethyl-2-oxo-1, 3-dioxolane) and urea

Abstract

Systems and methods for integrated glycerol carbonate and/or urea production. This disclosure pertains to development of a process for production of glycerol carbonate and/or urea from ammonia, carbon dioxide and glycerol. The process integrates glycerol carbonate production into a urea production process. The urea produced in the production facility may be used to produce glycerol carbonate by reacting urea with glycerol. The ammonia generated by glycerol carbonate production may be recycled back to urea production. Unreacted urea from the glycerol carbonate production may be separated and recycled to the urea product stream. The systems and methods can reduce the cost for urea production and increase product value of the excessive glycerol produced from other chemical plants.

Claims

1. A method of producing glycerol carbonate and/or urea, the method comprising steps as follows: (1) reacting carbon dioxide and ammonia to produce a first product stream comprising ammonium carbamate, unreacted ammonia, water and the urea; (2) heating the first product stream to decompose the ammonium carbamate to form a first decomposition product stream comprising ammonia and carbon dioxide, and a second product stream comprising urea and water; (3) subjecting the second product stream to a concentration process to produce a third product stream comprising concentrated urea; (4) subjecting the third product stream comprising the concentrated urea to a granulation process to produce granulated urea; (5) reacting at least some of the granulated urea with glycerol to form glycerol carbamate and ammonia; (6) decomposing the glycerol carbamate to form the glycerol carbonate and ammonia; (7) feeding at least some of the ammonia from step (5) and/or step (6) to step (1) for the reacting to form the first product stream; (8) transferring any unreacted granulated urea from step (5) to a urea product stream; and (9) flowing the glycerol carbonate from step (6) in a glycerol carbonate product stream; wherein the steps (5) and (6) comprise contacting the urea with the glycerol over a catalyst under reaction conditions sufficient to form the glycerol carbonate; and wherein the reaction conditions in step (5) comprise a reaction temperature in a range of 90° C. to 220° C. and a reaction pressure in a range of 2.0×10.sup.−3 to 2.0×10.sup.−1 MPa; and wherein the method is an integrated method for the production of glycerol carbonate and/or urea; wherein the catalyst comprises a metal as a catalytically active species; and wherein the metal is a single member selected from the group consisting of Zn++, Mg++, Mn++, Fe++, Ni++, Cd++, Ca++ and Li+, or is a combination of any two or more of Zn++, Mg++, Mn++, Fe++, Ni++, Cd++, Ca++ and Li+.

2. The method of claim 1, wherein the metal is Mg++.

3. The method of claim 1, wherein the metal is Mn++.

4. The method of claim 1, wherein the metal is Fe++.

5. The method of claim 1, wherein the metal is Ni++.

6. The method of claim 1, wherein the metal is Li+.

7. A method of producing glycerol carbonate and/or urea, the method comprising steps as follows: (1) employing carbon dioxide and ammonia in synthesizing the urea; (2) reacting at least some of the urea with glycerol to form glycerol carbamate and ammonia; (3) decomposing the glycerol carbamate to form the glycerol carbonate and ammonia; (4) feeding at least some of the ammonia from step (2) and/or step (3) to step (1) for the synthesizing; (5) transferring any unreacted urea from step (2) to a urea product stream; and (6) flowing the glycerol carbonate from step (3) in a glycerol carbonate product stream; wherein the urea and glycerol in step (2) reacts in a solvent; wherein the steps (2) and (3) comprise contacting the urea with the glycerol over a catalyst under reaction conditions sufficient to form the glycerol carbonate; and wherein the reaction conditions comprise a reaction temperature in a range of 90° C. to 220° C. and a reaction pressure in a range of 2.0×10.sup.−3 to 2.0×10.sup.−1 MPa; wherein the method is an integrated method for glycerol carbonate and/or urea; and wherein the solvent is selected from the group consisting of dichloromethane, nitro-benzene, methanol, and combinations thereof.

8. The method of claim 2, wherein the metal consists of Zn++.

9. The method of claim 1, wherein the reaction conditions comprise a reaction temperature in a range of 190° C. to 220° C.

10. The method of claim 7, wherein the solvent is dichloromethane, methanol, or a combination thereof.

11. A method for producing glycerol carbonate, the method comprising steps of: loading granulated urea into a reaction vessel via a solid loading conveyor connected to the reaction vessel, wherein the reaction vessel contains glycerol, to form a reaction mixture; agitating and thermally treating the reaction mixture in the reaction vessel to produce a product stream comprising the glycerol carbonate, unreacted urea and glycerol carbamate; feeding the product stream to a solids removal filtration facility; and collecting the glycerol carbonate in a storage tank or recycling the glycerol carbonate to the reaction vessel.

12. The method of claim 11, wherein a solvent, a catalyst or both are added to the reaction vessel.

13. The method of claim 11, wherein product stream is fed through a solids removal filtration facility.

14. The method of claim 11, wherein ammonia produced in the reaction vessel is removed from the reaction vessel via a vacuum pump.

15. The method of claim 14, wherein a condenser is installed before the vacuum pump to condense glycerol carbonate vapor drawn by the vacuum pump.

16. The method of claim 14, wherein the ammonia is scrubbed in a water scrubber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a flowchart for a method of producing glycerol carbonate and/or urea, according to embodiments of the invention.

(3) FIG. 2 is a schematic diagram for a reactor system used for producing glycerol carbonate and/or urea, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) A method has been discovered for production of glycerol carbonate and/or urea. By integrating the process of glycerol carbonate production into a urea production process, ammonia generated during glycerol carbonate production is re-used to produce urea, thereby reducing production cost for urea and providing a use for glycerol, thus, increasing its product value.

(5) Glycerol carbonate has garnered a lot of commercial interest mainly due to its reactivity and wide range of applications. Because it can be produced from glycerol, glycerol carbonate can be a valuable product that helps absorb the current glycerol glut, and potentially increase profit margin of existing chemical plants that produce glycerol. However, none of the currently available methods of glycerol carbonate production are integrated into a chemical production process (e.g., urea production process) and fully take advantage of cheap feedstock readily available from common chemical plants. The discovered method, according to embodiments of the invention, may remedy these deficiencies.

(6) As shown in FIG. 1, the embodiments of the present invention may employ carbon dioxide and ammonia in synthesizing urea via urea synthesis process 101. The synthesizing may comprise two main reactions:
2NH.sub.3+CO.sub.2.Math.NH.sub.2COONH.sub.4(ammonium carbamate)  (i)
NH.sub.2COONH.sub.4.Math.H.sub.2O+NH.sub.2CONH.sub.2(urea)  (ii)
In embodiments of the invention, the synthesizing of the urea may comprise reacting the ammonia with the carbon dioxide to form ammonium carbamate and decomposing the ammonium carbamate to form water and the urea. Thus, ammonium carbamate may be formed as a byproduct in urea synthesis process 101. First product stream 11 from urea synthesis process 101 may comprise urea, excess ammonia, ammonium carbamate, and water. In embodiments of the invention, first product stream 11 may comprise about 18 to 20 wt. % ammonia, about 50 to 52 wt. % ammonium carbamate, and about 30 to 35 wt. % urea.

(7) First product stream 11 may be fed to ammonium carbamate decomposition process 102. In ammonium carbamate decomposition process 102, the ammonium carbamate in first product stream 11 may be decomposed into ammonia and carbon dioxide. In embodiments of the invention, ammonium carbamate decomposition process 102 may comprise heating the ammonia, ammonium carbamate and urea from first product stream 11 to a sequence of step wise decomposition temperatures of 200° C., 160° C., and 138° C., respectively. The ammonia and carbon dioxide generated from ammonium carbamate decomposition process 102 may form stream 12. Stream 12 may be fed back to urea synthesis process 101 in stream 13. The urea and water exiting the decomposition forms second product stream 14.

(8) In embodiments of the invention, second product stream 14 comprising urea and water goes through urea concentration process 103 to produce molten urea of about 99.6 or 99.7 wt. % to 99.8 wt. %. The molten urea exiting urea concentration process 103 may form third product stream 15. In embodiments of the invention, urea concentration process 103 may comprise evaporating urea of 71 to 83.5 wt. % from stream 14 at 0.34 atmosphere absolute pressure. The evaporating process may comprise heating the urea and the water from second product stream 14 to a temperature of 110° C. to 130° C. In embodiments of the invention, the water generated in urea concentration process 103 may form stream 16. Stream 16 may be recycled back to urea synthesis process 101 in stream 13. Urea granulation process 104 may be performed on the urea from third product stream 15 to produce granulated urea 20.

(9) With continued reference to FIG. 1, at least some of the urea produced from urea granulation process 104 may be loaded into a reactor system via stream 17. The reactor system contains glycerol that is loaded via stream 18. The urea and glycerol reacts under sufficient reaction conditions to produce glycerol carbonate via glycerol carbonate synthesis process 105. Generally, glycerol carbonate synthesis process 105 may comprise two main reactions:
urea+glycerol.fwdarw.glycerol carbamate+ammonia  (iii)
glycerol carbamate.fwdarw.glycerol carbonate+ammonia  (iv)

(10) In reaction (iii), the urea reacts with glycerol to form glycerol carbamate and ammonia. The glycerol carbamate is then decomposed to form glycerol carbonate and ammonia in reaction (iv).

(11) In embodiments of the invention, the reaction conditions for glycerol carbonate synthesis process 105 may include a reaction temperature of about 90° C. to about 220° C., and all ranges and values there between including 90 to 100° C., or 100 to 110° C., or 110 to 120° C., or 120 to 130° C., or 130 to 140° C., or 140 to 150° C., or 150 to 160° C., or 160 to 170° C., or 170 to 180° C., or 180 to 190° C., or 190 to 200° C., or 200 to 210° C., or 210 to 220° C. The reaction conditions for glycerol carbonate synthesis process 105 may comprise a reaction pressure of about 2.0×10.sup.−5 to 2.0×10.sup.−1 MPa, and all ranges and values there between including 2.0×10.sup.−5 to 2.0×10.sup.−4 MPa, 2.0×10.sup.−4 to 2.0×10.sup.−3 MPa, 2.0×10.sup.−3 to 2.0×10.sup.−2 MPa, 2.0×10.sup.−2 to 2.0×10.sup.−1 MPa. In embodiments of the invention, the reaction conditions for glycerol carbonate synthesis process 105 may include a batch time (or residence time in the cases of non-batch reactors) of about 1 to about 48 hours depending on the catalyst used for the reaction and all ranges and values there between including 1 to 3 hours, 3 to 5 hours, 5 to 7 hours, 7 to 9 hours, 9 to 11 hours, 11 to 13 hours, 13 to 15 hours, 15 to 17 hours, 17 to 19 hours, 19 to 21 hours, 21 to 23 hours, 23 to 25 hours, 25 to 27 hours, 27 to 29 hours, 29 to 31 hours, 31 to 33 hours, 33 to 35 hours, 35 to 37 hours, 37 to 39 hours, 39 to 41 hours, 41 to 43 hours, 43 to 45 hours, or 45 to 48 hours.

(12) In embodiments of the invention, a catalyst may be used in glycerol carbonate synthesis process 105. More specifically, the catalyst may comprise a metal as a catalytically active species. Exemplary metals may include, but are not limited to, one of Zn++, Mg++, Mn++, Fe++, Ni++, Cd++, Ca++, Li+, or combinations thereof. In embodiments of the invention, the metal may be present in sulfate, phosphate, stearates, carboxylates, derivative of natural fatty acids form or combinations thereof. The catalyst may be used in this reaction after calcination. Additionally or alternatively, the catalyst used in this reaction may comprise a metal oxide as a catalytically active species. Examples of the metal oxide may include, but are not limited to, one of ZnO, Co.sub.3O.sub.4, CaO, La.sub.2O.sub.3, MgO, ZrO.sub.2, or combinations thereof. Additionally or alternatively, the catalyst used in this reaction may comprise a metal alkoxide based catalytic system. The metal alkoxide based catalytic system may include one or more titanium alkoxides, one or more aluminum alkoxides, one or more zirconium alkoxides, or combinations thereof. Additionally or alternatively, the catalyst used in this reaction may comprise a alkyl tin based catalytic system. The alkyl tin based catalytic system may include dibutyltin oxide, dibutyltin dimethoxide, triphenyltin chloride, or combinations thereof. In embodiments of the invention, the metal oxide (catalytically active species) may be supported by a matrix. This matrix may be one of silica, alumina, hydrotalcite, polymers thereof, or combinations thereof. In embodiments of the invention, a solvent may be used in glycerol carbonate synthesis process 105. Exemplary solvents may include, but are not limited to, one of dimethylformamide, dimethyl sulfoxide, dichloromethane, nitro-benzene, dimethylacetamide, methanol, or combinations thereof.

(13) In embodiments of the invention, the molar ratio of urea to glycerol provided in process 105 may include about 0.33 to about 1.2, and all ranges and values there between, including 0.33 to 0.40, 0.40 to 0.50, 0.50 to 0.60, 0.60 to 0.70, 0.70 to 0.80, 0.80 to 0.90, 0.90 to 1.00, 1.00 to 1.10, or 1.10 to 1.20. In embodiments of the invention, the molar ratio of urea to glycerol in process 105 may include 0.33 to 0.40, or 0.40 to 0.50, 0.50 to 0.60, 0.60 to 0.70, 0.70 to 0.80, 0.80 to 0.90, 0.90 to 1.00, 1.00 to 1.10, or 1.10 to 1.20, and all ranges and values there between.

(14) In embodiments of the invention, the ammonia produced from glycerol carbonate synthesis process 105 may be recycled back to the urea synthesis reaction via stream 19. In embodiments of the invention, ammonia from streams 12 and 19, carbon dioxide from stream 12, and water from stream 16 may be recovered via recovery process 106, and subsequently fed back to urea synthesis process 101 via stream 13. The recovery process 106 may comprise cooling the ammonia from streams 12 and 19, the carbon dioxide from stream 12 and the water from stream 16 via cooling tower, chiller, or a combination thereof.

(15) In embodiments of the present invention, unreacted urea from glycerol carbonate synthesis process 105 may be separated from the glycerol carbonate via separation process 107. The separated, unreacted urea may be collected and returned to second product stream 14 via stream 21. Alternatively or additionally, the separated, unreacted urea may be collected and directly returned to urea concentration process 103. The unreacted urea may be further concentrated via urea concentration process 103, and granulated via urea granulation process 104. In embodiments of the invention, separation process 107 may include one or more of filtration, vacuum distillation, carbon bed adsorption, or combinations thereof. Alternatively, the urea from glycerol carbonate synthesis process 105 may be substantially fully reacted and may not be recycled back to second product stream 14. In embodiments of the invention, the glycerol carbonate may be collected via fifth product stream 22 after separation process 107.

(16) As shown in FIG. 2, the reactor system for production of glycerol carbonate may comprise solid loading conveyor 201 connected to reaction vessel 202. Granulated urea can be loaded into reaction vessel 202 through solid loading conveyor 201. Once the granulated urea comes into contact with the glycerol in reaction vessel 202, agitation and thermal treatment may be applied to the mixture. Solvents and/or catalyst described above may be applied in reaction vessel 202 for glycerol carbonate synthesis 105.

(17) The product stream comprising glycerol carbonate, unreacted urea, and/or glycerol carbamate exiting the reaction vessel may go through solids removal filtration facility 203. The liquid glycerol carbonate may be either recycled back to the reaction vessel through liquid recycle pump 204 or collected as the product having 90 to 94 wt. % glycerol carbonate in storage tank 205. The ammonia generated in glycerol carbonate process 105 may be removed using vacuum pump 206. To avoid the glycerol carbonate entering the vacuum line, condenser 207 may be installed before vacuum pump 206. Glycerol carbonate vapor drawn by vacuum pump 206 may be condensed and returned to reaction vessel 202. The ammonia removed from reaction vessel 202 by vacuum pump 206 may be scrubbed in water scrubber 208, where it is absorbed and then transferred to ammonia solution tank 209. The ammonia solution is then transferred to ammonia recovery unit 210. The recovered ammonia may be recycled back to urea synthesis process 101.

(18) Although embodiments of the present invention have been described with reference to blocks of FIG. 1, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 1. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 1.

(19) Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.