Method for continuous production of 2,3-butanediol

Abstract

The present invention relates to a method for continuous production of 2,3-butanediol by hydrogenation of 3-hydroxybutanone with hydrogen in the presence of a heterogeneous hydrogenation catalyst filled in one or more fixed-bed flow tubular reactor systems comprising one or more tubes with an inner diameter from 1 mm to 6 mm.

Claims

1. A method for continuous production of 2,3-butanediol, by hydrogenation of 3-hydroxybutanone with hydrogen in the presence of a heterogeneous hydrogenation catalyst filled in one or more fixed-bed flow tubular reactor systems comprising one or more tubes, wherein the inner diameter of each tube is from 1 mm to 6 mm; wherein the method comprising feeding 3-hydroxybutanone and hydrogen into the one or more fixed-bed flow tubular reactor systems.

2. The method according to claim 1, wherein the number of tubes in each reactor system is from 1 to 25,000.

3. The method according to claim 1, wherein the one or more fixed-bed flow tubular reactor systems comprise two or more parallel tubes having the same lengths and internal diameters.

4. The method according to claim 1, wherein the inner diameter of each tube is from 1.5 mm to 4 mm.

5. The method according to claim 1, wherein the length of each tube is from 5 cm to 5 m.

6. The method according to claim 1, wherein the method comprises feeding 3-hydroxybutanone into the one or more fixed-bed flow tubular reactor systems as a liquid.

7. The method according to claim 1, wherein the method comprises feeding 3-hydroxybutanone into the one or more fixed-bed flow tubular reactor systems as a solution in a solvent selected from the group consisting of water, (C.sub.1-C.sub.4)-alkyl alcohol, and mixtures thereof.

8. The method according to claim 7, wherein the (C.sub.1-C.sub.4)-alkyl alcohol is selected from the group consisting of methanol, ethanol, propanol, 2-propanol, 1-butanol, 2-butanol, sec-butanol and tert-butanol.

9. The method according to claim 1, wherein the reaction temperature is from 75° C. to 275° C.

10. The method according to claim 1, wherein the reaction pressure is from 0.1 MPa to 5 MPa of hydrogen.

11. The method according to claim 1, wherein the contact time between reactants and the catalyst is from 0.5 s to 10 s.

12. The method according to claim 1, wherein the molar ratio H.sub.2/3-hydroxybutanone is from 1 to 5.

13. The method according to claim 1, wherein the catalyst is selected from group consisting of Raney Ni and a metal supported catalyst, wherein the metal is selected from the group consisting of Ru, Pt, Pd, and Rh, and the support is selected from the group consisting of carbon, graphite, graphene, graphene oxide, alumina and silica.

14. The method according to claim 1, wherein the method is carried out in more than one of the one or more fixed-bed flow tubular reactor systems and the one or more fixed-bed flow tubular systems are arranged in parallel or in series.

15. The method according to claim 14, wherein the method is carried out in more than one of the fixed-bed flow tubular reactor systems connected in series and the reaction conditions of pressure, temperature and contact time in each of the one or more fixed-bed flow tubular reactor systems are the same or different.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a fixed-bed flow multitubular reactor system comprising 16 tubes, each one 10 cm in length with an inner diameter of 1.75 mm.

DETAILED DESCRIPTION OF THE INVENTION

(2) All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the state of the art. Other more specific definitions for certain terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

(3) For purposes of the present invention, any ranges given include both the lower and the upper end-points of the range. Ranges given, such as temperatures, pressure, times, and the like, should be considered approximate, unless specifically stated.

(4) As it is mentioned above, the present invention relates to more productive method to produce continuously 2,3-butanediol by hydrogenation of 3-hydroxybutanone using one or more fixed-bed tubular reactor systems.

(5) The terms “2,3-BDO” or “2,3-butanediol” have the same meaning, and are used interchangeably.

(6) The terms “acetoin” or “3-hydroxybutanone” have the same meaning, and are used interchangeably.

(7) The terms “molecular hydrogen”, “hydrogen” or “H.sub.2” have the same meaning, and are used interchangeably.

(8) The term “acetoin conversion” refers to the amount of acetoin transformed into another chemical compound relative to the initial amount of acetoin. In the specific case of a continuous process, it refers to the amount of acetoin transformed into another chemical compound relative to the initial amount of acetoin after one pass into the reactor. In the context of the invention, the conversion is expressed as a percentage and it can be calculated by means of equation (1):
C(%)=(N.sub.f−N.sub.out)*100/N.sub.f  (1)
where C is the acetoin conversion, N.sub.f are the moles of acetoin/h in the feed into the reactor system and N.sub.out are the moles of acetoin/h at the outlet of the reactor system.

(9) The term “selectivity to 2,3-BDO formation” refers to the number of moles of 2,3-BDO obtained relative to the moles of acetoin converted. In the context of the invention, the selectivity is expressed as a percentage and it can be calculated by means of equation (2):
S(%)=N.sub.BDO*100/(N.sub.f−N.sub.out)  (2)
where S is the 2,3-BDO selectivity, N.sub.BDO are the moles of 2,3-BDO/h at the outlet of the reactor system and N.sub.f and N.sub.out are as previously defined.

(10) The number of tubes in a reactor system will depend on the desired productivity of the process. In an embodiment, the method is carried out in one or more fixed-bed flow tubular reactor systems comprising from 1 to 25,000 tubes. In an embodiment, the method is carried out in one or more fixed-bed flow tubular reactor systems which comprises two or more parallel tubes having the same lengths and internal diameters, through which the feed rate is evenly distributed. In an embodiment, the inner diameter of each tube is from 1.5 mm to 4 mm. In an embodiment, the length of each tube is from 5 cm and 5 m; preferably from 8 cm and 1 m. In an embodiment, the method is carried out in more than one reactor system and the systems are arranged both in parallel or in series. In an embodiment, the method is carried out in more than one reactor system connected in series and the reaction conditions of pressure, temperature and contact time in each reactor are the same. In another embodiment, the method is carried out in more than one reactor system connected in series and the reaction conditions of pressure, temperature and contact time in each reactor are different. In a particular example, a tubular reactor system comprising 16 tubes, each one 10 cm in length with an inner diameter of 1.75 mm is depicted in FIG. 1. Using the experimental conditions of the example 2 of the present invention, this small reactor system of lab size that fits inside a hand is able to produce 0.942 kg/day of 2,3-BDO. An arrangement in parallel of 100 reactor systems of this type affording for 1600 tubes will produce 94.2 kg/day, i.e. 31.4 tons/y operating during 8000 h/y. The 100 reactor systems can be contained in a small room of 3.5 m×0.15 m×0.05 cm, 0.02625 m.sup.3. The total effective volume of the 1600 tubes is 3.85.Math.10.sup.−4 m.sup.3, resulting in a productivity of 10.20 ton/h/m.sup.3.

(11) The process of the present invention can yield an acetoin conversion equal to or higher than the following percentages: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, and 100%. In addition, the process of the present invention can yield a selectivity to 2,3-BDO formation equal to or higher than the following percentages: 95%, 96%, 97%, 98%, 99% and 100%.

(12) In an embodiment, the method comprises feeding pure molten 3-hydroxybutanone into the reactor system. In an embodiment, the method comprises feeding 3-hydroxybutanone into the reactor system as a solution in a solvent selected from the group consisting of water, (C.sub.1-C.sub.4)-alkyl alcohol, and mixtures thereof. In an embodiment, the method comprises feeding 3-hydroxybutanone into the reactor system as a solution in water. In an embodiment, the method comprises feeding 3-hydroxybutanone into the reactor system as a solution in an (C.sub.1-C.sub.4)-alkyl alcohol selected from the group consisting of methanol, ethanol, propanol, 2-propanol, 1-butanol, 2-butanol, sec-butanol and tert-butanol.

(13) In an embodiment, the method is carried out at a reaction temperature from 75° C. to 275° C., preferably from 100° C. to 250° C.

(14) In an embodiment, the method is carried out at a reaction pressure from 0.1 MPa to 5 MPa of hydrogen preferably from 0.1 MPa to 2.5 MPa of hydrogen.

(15) In an embodiment, the method is carried out at a contact time between the reactants and catalyst from 0.5 s to 10 s, preferably from 1 s to 8 s.

(16) In an embodiment, the method is carried out at a H.sub.2/acetoin molar ratio from 1 to 5, preferably from 1.5 to 3.

(17) The catalyst can be any one of the hydrogenation catalysts typically used to reduce ketones to alcohols. Non limitative examples of hydrogenation catalysts are Raney Ni, and metal supported catalysts wherein the metal is selected from the group consisting of Ru, Pt, Pd, and Rh, and the support is selected from the group consisting of carbon, graphite, graphene, graphene oxide, alumina and silica. In an embodiment, the catalyst is a metal supported catalyst wherein the metal is Ru and the support is carbon, silica or alumina.

(18) Throughout the description and claims the word “comprise” and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Furthermore, the word “comprise” encompasses the case of “consisting of”. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples and drawings are provided by way of illustration, and they are not intended to be limiting of the present invention. Furthermore, the present invention covers all possible combinations of particular and preferred embodiments described herein.

Examples 1-5

(19) Following the general operation mode above described, a 50 wt % aqueous solution of acetoin (purity 98%) solution in water was fed into a fixed-bed flow (multi)tubular reactor system consisting of a tube 10 cm in length fully filled with a commercial catalyst of carbon-supported Ru with a Ru load of 5 wt % (Ru(5%)/C) under the experimental conditions given in Table 1. The catalyst bulk density was 0.50 g.Math.mL.sup.−1. Tube inner diameters and results are also given in Table 1. Conversions and selectivities were calculated according equations (1) and (2), in which N.sub.BDO and N.sub.out were calculated from the concentrations of acetoin and 2,3-BDO on the condensed fraction liquid at the outlet of the reactor system as determined by HPLC.

(20) As it can be seen in Table 1, 100% selectivities are achieved in all cases with conversions ranging between 90% and 99% for contact times 5.2 s.

(21) Outstanding 2,3-BDO productivities are obtained. For instance, a 2,3-BDO productivity of 2.89 ton/h/m.sup.3 is achieved under experimental conditions of example 4. Using the process according to WO2016012634 A1 (example 37) a 74.5-fold lower 2,3-BDO productivity of 0.04 ton/h/m.sup.3 is obtained at 125° C. but with the penalty of a higher hydrogen pressure of 5 MPa, 10-fold higher. No data about the dimensions of the tubular reactor used in the process described by Duan et al. are given. However, taking the lower contact time of 0.5 h used and the best value of 2,3-BDO yield (90.1%) reported at 150° C. by these researchers, a 2,3-BDO productivity 562.5-fold lower than that obtained in example 3 of the present invention can be estimated. The process of the present invention has a productivity surprisingly huge in comparison with those of the current state of the art.

(22) TABLE-US-00001 TABLE 1 Reaction conditions Con- Results Q.sub.f tact P.sup.f Di.sup.a T P.sub.H2 (ton/ time C.sup.d S.sup.e (ton/ Ex. (mm) (° C.) (MPa) h/m.sup.2).sup.b MR.sup.c (s) (%) (%) h/m.sup.3) 1 4 250 5 2.006 2.3 2.1 90 100 8.23 2 1.75 250 5 1.995 2.3 2.1 100 100 10.20 3 4 150 0.5 0.400 2.3 3.2 90 100 1.85 4 4 150 0.5 0.600 2.3 2.1 97 100 2.98 5 4 125 1.5 0.600 2.3 5.2 96 100 2.95 .sup.aInner diameter of the tubular reactor .sup.bSpecific feed rate of a 50 wt % aqueous solution of acetoin, relative to the cross-sectional area of the tube .sup.cH.sub.2/acetoin molar ratio .sup.dAcetoin conversion .sup.e2,3-Butanediol selectivity .sup.f2,3-BDO productivity

Example 6

(23) This example shows that the process of the present invention can be effectively carried out at a hydrogen pressure as low as 0.1 MPa. Following the general operation mode above described, a 50 wt % acetoin solution in water was fed into a reactor system consisting of 6 tubes 10 cm in length arranged in series. The inner diameter of each tube was 1.75 mm. All tubes were operated at 150° C. and were fully filled with the same catalyst than in the previous examples. The feed flow rate was 1.047 ton/h/m.sup.2 relative to the cross-sectional surface of a tube. The H.sub.2/acetoin molar ratio was 2.3 with a hydrogen pressure of 0.1 MPa. Results are given in Table 2. Conversions and selectivities were determined by HPLC as described in examples 1-5. As it can be seen, a 96.6% conversion and a 100% selectivity are achieved with a total contact time of 9 s.

(24) It is apparent for a skilled in the art that a 100% conversion could be achieved by increasing the number of tubes, by increasing the contact time sequentially from the first to the last tube, or by increasing in the same way the temperature in each tube, or by a combination of both. It is also apparent for a skilled in the art that a 100% conversion could be achieved with a number of tubes lower than those used in these examples by increasing sequentially from the first to the last tube the contact time and/or the temperature in each tube.

(25) TABLE-US-00002 TABLE 2 Contact time.sup.a C.sup.b S.sup.c Tube (s) (%) (%) 1 1.5 40.0 100 2 3.0 74.8 100 3 4.5 84.4 100 4 6.0 90.6 100 5 7.5 94.4 100 6 9.0 96.6 100 .sup.aAccumulated contact time .sup.bAccumulated acetoin conversion .sup.cAccumulated 2,3-BDO selectivity

REFERENCES CITED IN THE APPLICATION

(26) 1. The PCT patent application WO2016097122 2. The PCT patent application WO2016012634 3. H. Duan, et al. “Vapor-phase hydrogenation of acetoin and diacetyl into 2,3-butanediol over supported metal catalysts”. Catalysis Communications, 2017. Vol. 99, pp. 53-56).