Method for producing and purifying 1,3-butadiene

Abstract

The invention relates to a method for producing butadiene that is fed with a butanediol feedstock, with said method comprising at least: a) An esterification step comprising: A reaction section; A separation section producing a butanediol diester effluent, a water effluent, and a carboxylic acid effluent; b) An esterification pyrolysis step; c) A separation step comprising at least: A cooling section producing a liquid pyrolysis effluent and a vapor pyrolysis effluent; A gas-liquid washing section that is fed at the top with a fraction of the carboxylic acid effluent that is obtained from the separation section of step a) and at the bottom with said vapor pyrolysis effluent and producing at the top a butadiene effluent and at the bottom a washing effluent; in which a carboxylic-acid-rich stream comprising at least a portion of the liquid pyrolysis effluent is recycled to step a); d) A separation step.

Claims

1. A method for producing butadiene from a butanediol feedstock, said method comprising: a) An esterification step comprising: feeding a reaction section said butanediol feedstock, a carboxylic-acid-rich stream that is obtained from step c), and at least one fraction of a carboxylic acid effluent that is obtained from a separation section of step a) said reaction section comprises an acid catalyst and is operated at a pressure of between 0.01 and 1.0 MPa, and at an MMH in the reaction section (molar flow rate of diol feeding said section with a catalyst mol number in said section) of between 0.05 and 25 h.sup.1 to produce a reaction section effluent comprising butanediol diester; separating in the separation section the reaction section effluent into at least one butanediol diester effluent, a water effluent, and the carboxylicacid effluent; b) A pyrolysis step comprising feeding a pyrolysis reactor with at least said butanediol diester effluent that is obtained from the esterification step a), said pyrolysis carried out at a temperature of between 400 and 650 C. to produce a pyrolysis effluent; c) A separating step for separation of said pyrolysis effluent that is obtained from step b), comprising at least: cooling said pyrolysis effluent in a cooling section to a temperature that is lower than 150 C. to produce a liquid pyrolysis effluent and a vapor pyrolysis effluent; feeding the top of a gas-liquid washing section with at least one fraction of the carboxylic acid effluent that is obtained from the separation section of step a) and at the bottom of the gas-liquid washing section with said vapor pyrolysis effluent to produce a butadiene effluent at the top and a washing effluent at the bottom; recycling at least a portion of the liquid pyrolysis effluent to step a) as the carboxylic-acid-rich stream; d) A purification step that is fed with the butadiene effluent that is obtained from step c) comprising at least: introducing a stream comprising water to the top of a second gas-liquid washing section and introducing at the bottom of the second gas-liquid washing section the butadiene effluent that is obtained from step c) and producing a hydrated butadiene effluent and at the bottom an aqueous washing effluent; eliminating water, butenes and light products comprised in the hydrated butadiene effluent in a final purification section to produce butadiene.

2. The method according to claim 1, in which said butanediol feedstock comprises at least 90% by weight of a butanediol that is selected from the group that consists of 2,3-butanediol, 1,4-butanediol, and mixture thereof.

3. The method according to claim 1, in which the carboxylic acid that is used is selected from the group that consists of formic acid, acetic acid, propanoic acid, butanoic acid, and benzoic acid.

4. The method according to claim 1, in which the ratio of the molar flow rates of butanediol and carboxylic acid at the inlet of said reaction section of said step a) is between 2 and 6.

5. The method according to claim 1, in which the carboxylic acid that is used is acetic acid.

6. The method according to claim 5, in which said separation section of said step a) comprises heterogeneous azeotropic distillation in the presence of a driver.

7. The method according claim 1, in which said cooling section of said step c) comprises quenching, with the quenching liquid being at least one fraction of said liquid pyrolysis effluent, cooled in advance.

8. The method according claim 1, in which said cooling section of said step c) comprises quenching, with the quenching liquid being at least one fraction of said washing effluent that is obtained from said washing section of said step c).

9. The method according to claim 7, in which said cooling section of said step c) is implemented in a quenching tower in which a first quenching liquid, comprising a fraction of said liquid pyrolysis effluent that is cooled in advance, is introduced at an intermediate position within the quenching tower, and a second quenching liquid, consisting of the washing effluent that is obtained from the washing section of said step c), is introduced at a position that is located above said first quenching liquid, along a vertical axis.

10. The method according to claim 1, in which said carboxylic-acid-rich stream that is recycled to step a) comprises, in addition to at least a portion of the liquid pyrolysis effluent, at least one fraction of said washing effluent that is obtained from the washing section of said step c).

11. The method according claim 1, in which the carboxylic-acid-rich stream comprises purified liquid pyrolysis effluent.

12. The method according to claim 7, in which a fraction of purified liquid pyrolysis effluent is used to feed the cooling section of said step c) as a quenching liquid.

13. The method according claim 1, in which said carboxylic-acid-rich stream comprises non-purified liquid pyrolysis effluent from step c).

14. The method according to claim 1, in which an addition of carboxylic acid from a source that is external to the method is fed in a mixture with the carboxylic-acid-rich stream that is obtained from step c) and/or the fraction of the carboxylic acid effluent that is obtained from the separation section of step a).

15. The method according to claim 1, in which the stream comprising water that feeds the gas-liquid washing section of said step d) comprises the water effluent that is obtained from the separation section of said step a).

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 presents a diagrammatic view of an arrangement of the method according to the invention.

(2) FIG. 2 has an arrangement of step c) according to the invention. The numbering is identical between FIGS. 1 and 2.

(3) FIG. 3 has a particular arrangement of step d) according to a variant of the invention. The numbering is identical between FIGS. 1, 2, and 3.

(4) In FIG. 1, the butanediol feedstock (1) undergoes a first esterification step a) with a carboxylic-acid-rich stream (8) and an addition of carboxylic acid (2) for producing, on the one hand, a butanediol diester effluent (5), and, on the other hand, a water effluent (3) and a by-product effluent (3bis) that are eliminated from the method. A carboxylic acid effluent (4) that feeds the separation step c) is also produced.

(5) The butanediol diester effluent (5) feeds a pyrolysis step b) that produces a pyrolysis effluent (6) that feeds a separation step c).

(6) The separation step c) is fed with a fraction of the carboxylic acid effluent that is produced by the separation section of step a) and by the pyrolysis effluent that is obtained from step b). The residual fraction of the carboxylic acid effluent that is produced by the separation section of step a) feeds the reaction section of said step a) (not shown). The separation step c) produces a carboxylic-acid-rich effluent (8) that is recycled to the esterification step a), a butadiene effluent (7) that feeds a purification step d), and a by-product effluent (8bis) that is eliminated from the method.

(7) The purification step d) is fed with a water-rich effluent (9), with the butadiene effluent (7) that is obtained from the separation step c), and optionally with an addition of solvent (14). Step d) produces an aqueous washing effluent (10) that is advantageously recycled to the separation section of step a), an aqueous effluent (13) that is eliminated from the method, an effluent of incondensable gases (11), a draw-off of solvent that is to be purified (15), and optionally an effluent of liquid impurities (16) that are eliminated from the method. Step d) thus produces a purified butadiene (12).

(8) During the pyrolysis step b), a small fraction of carboxylic acid can be cracked. The cracking products are eliminated from step d) in the effluent of incondensable gases (11). The addition of carboxylic acid (2), optional and preferred, introduced in step a) compensates for the losses of carboxylic acid in step b).

(9) FIG. 2 has an arrangement of step c) according to the invention. The numbering is identical between FIGS. 1 and 2.

(10) In FIG. 2, pyrolysis effluent (6) is introduced at the bottom of a quenching tower (C1). This quenching tower is fed with two separate quenching liquids, numbered (41) and (64). The feeding of the quenching liquid (41) is at a position that is higher than that of the quenching liquid (64). This quenching tower produces a vapor pyrolysis effluent (61) that feeds a gas-liquid washing column (C2) and a liquid pyrolysis effluent (62) that feeds an optional purification section (X). This purification section (X) produces a by-product effluent (8bis) that is eliminated from the method, and a purified liquid pyrolysis effluent (63), of which a fraction (64) is cooled before being recycled to the quenching tower (C1). The other fraction of the purified liquid pyrolysis effluent constitutes the carboxylic-acid-rich stream (8) that is recycled to step a) of the method.

(11) The vapor pyrolysis effluent (61) is introduced at the bottom of the gas-liquid washing column (C2), which is fed at the top with a carboxylic acid effluent fraction (4) that is produced by the separation section of step a) of the method. Said gas-liquid washing column (C2) produces at the top a butadiene effluent (7) that feeds step d) for purification of butadiene and at the bottom a liquid effluent (41) that is cooled before being sent back to the top of the quenching tower (C1).

(12) FIG. 3 has a particular arrangement of step d) according to a variant of the invention. The numbering is identical between FIGS. 1, 2, and 3.

(13) In FIG. 3, the butadiene effluent (7) that is obtained from step c) is introduced at the bottom of a gas-liquid washing column (D1), which is fed with a water-rich effluent (9) that is external to the method or that comes from the separation section a) (3). The gas-liquid washing column (D1) produces at the bottom an aqueous washing effluent (10) that is advantageously recycled to the separation section of step a) and a hydrated butadiene effluent (71) that feeds an extractive distillation section, composed of a first extractive distillation column (D2), also fed with recycled solvent (72) and an addition of solvent (14).

(14) This column (D2) produces at the top an incondensable gas effluent (11) that is eliminated from the method and at the bottom a purified butadiene effluent (73). This effluent feeds a distillation column (D3) that makes it possible to recover at the bottom the solvent (72) that is recycled to the column (D2) and at the top the purified butadiene without solvent (74). A draw-off of solvent is possible via the stream (15). A last distillation column (D4) makes it possible to eliminate from the method the possible traces of heavy impurities by separating the purified butadiene without solvent (74) into a purified butadiene (12) with the required specifications drawn off at the top and an effluent (16) with heavy impurities drawn off at the bottom.

EXAMPLE

(15) This example shows that the concatenation of the steps of esterification, pyrolysis, separation, and purification, with, on the one hand, the recycling of the liquid pyrolysis effluent to the esterification step and to the separation step of butadiene and, on the other hand, the recycling of the carboxylic acid effluent to the steps for purification of butadiene, leads to the production of 150 kt/year of 1,3-butadiene with more than 99.9% by weight of purity and with very small losses of reagents (operating period of 8,000 hours per year). There is thus synergy between the esterification/pyrolysis concatenation and the recycling of the liquid pyrolysis effluent and the concatenation of separation and purification steps fed with the pyrolysis effluent.

(16) The following example is based on method simulations taking into account the recycling of streams and integrating thermodynamic data based on literature and data points (binary liquid-vapor balance data). In each of the examples, the feedstock flow rate is adjusted in such a way as to obtain an annual production of 150 kt/year of a butadiene having a purity of between 99.5 and 100% by weight (in adaptation with the current use of the product), with an annual operating period of the method of 8,000 hours.

(17) The overall yield of the simulated method is 48.9% expressed in terms of one ton of butadiene per ton of 2,3-butanediol for a theoretical yield of the reaction of 60%. Its efficiency, or the ratio of the overall yield to the theoretical yield, is therefore 81.6%. The butadiene fraction at the outlet of the simulated method is 99.98% by weight of butadiene.

(18) Step a) for Esterification

(19) A butanediol feedstock that consists of 2,3-butanediol and an acetic-acid-rich stream (88.5% by weight) feed an esterification step by reactive distillation (molar ratio of 3) to produce a butanediol diester effluent comprising 2,3-butanediol diacetate and a carboxylic acid distillate. The acetic-acid-rich stream is obtained from, on the one hand, the separation step c) (recycling of the liquid pyrolysis effluent) and, on the other hand, the acetic acid/water separation column by heteroazeotropic distillation that makes it possible to eliminate the by-products that are formed by dehydration, the organic impurities, the water that is produced by the reaction, and the acetic acid.

(20) This carboxylic acid distillate that is obtained from the reactive distillation contains 52.6% by weight of carboxylic acid, 30.4% by weight of water, and 16.9% of impurities. It feeds a distillation column comprising 25 theoretical stages and making it possible to eliminate at the top 100% of the impurities that are formed by dehydration. The residue from the column, consisting of 64.1% by weight of acetic acid and 35.9% by weight of water, feeds, with the aqueous washing effluent that is obtained from the gas-liquid washing column of section c), the acetic acid/water separation column by heteroazeotropic distillation with a heterogeneous driver.

(21) The water stream exiting from this column is used in part for the gas-liquid washing of the butadiene effluent of section c). The acetic acid stream at the bottom is directed toward the acetic acid washing column and toward the reactive distillation section.

(22) Step b) for Pyrolysis

(23) The butanediol diester effluent that is obtained from the esterification step a) is preheated from 235 C. to 400 C. and then introduced into a pyrolysis furnace that operates at 595 C. and 0.11 MPa. The conversion rate of the diester is 99.4% with a selectivity of the butadiene in relation to the diester of 81.7 mol %.

(24) Step c) for Separation

(25) In a first step, the pyrolysis effluent undergoes cooling from 595 C. to 170 C. in a quenching column, with this fast cooling making it possible to prevent the polymerization of butadiene, and consequently to stop the pyrolysis reactions. At the end of this cooling, a vapor pyrolysis effluent and a liquid pyrolysis effluent are recovered. This cooling is carried out by quenching with a fraction of the liquid pyrolysis effluent that was cooled in advance to a temperature of 35 C.

(26) The composition of the liquid pyrolysis effluent is indicated in Table 1.

(27) TABLE-US-00001 TABLE 1 Composition by mass and molar composition of the liquid pyrolysis effluent. % by Mass Mol % AA 83.44% 90.76% MVCA 6.73% 3.85% MEKEA 2.03% 1.16% CA 3.88% 2.22% MAA 2.03% 1.16% AA = acetic acid, MVCA = methyl vinyl carbinol acetate, MEKEA = methyl ethyl ketone enol acetate, CA = crotyl acetate, MAA = methyl acetyl acetone

(28) A fraction (approximately 66%) of the liquid pyrolysis effluent is used for the quenching of the pyrolysis effluent. The remaining reaction is sent to an adsorption column before being recycled to the esterification section as a carboxylic-acid-rich stream.

(29) The top of the quenching column, called a vapor pyrolysis effluent and consisting primarily of butadiene (92.2% by weight), methane (1.8% by weight), CO2 (5% by weight), and several oxidized impurities, is compressed to 0.3 MPa, which makes it possible to increase the temperature of this stream to 53 C. This stream then feeds a washing column with acetic acid comprising 5 theoretical stages. The acetic acid that is used is obtained from the bottom of the water/acetic acid separation column by heteroazeotropic distillation. Its composition is therefore 99.99% by weight of acetic acid and 0.01% by weight of diester. This washing makes it possible to eliminate more than 97% of the organic compounds entrained in the vapor pyrolysis effluent, or 125 kg/h of impurities such as the pyrolysis intermediate compounds and by-products formed during the pyrolysis step. The bottom of the column contains butadiene (7.2% by weight), which is therefore recycled to the quenching column. The loss of 1,3-butadiene is insignificant in this separation step. A butadiene effluent is drawn off at the top of the column.

(30) Step d) for Purification

(31) The butadiene effluent that is obtained from the acetic acid washing column and that consists of 90.4% by weight of butadiene is washed with water in a gas-liquid water washing column comprising 10 theoretical stages, so as to eliminate the remaining 3% by weight of acetic acid. The water-rich effluent that is used for the washing comes from the step for separation by heteroazeotropic distillation of the acetic acid and water. The aqueous washing effluent that is drawn off at the bottom of the column, consisting primarily of acetic acid (43% by weight) and water (55% by weight), is recycled to the column for separation by acetic acid/water heteroazeotropic distillation so as to reduce the addition of acetic acid at the butanediol esterification section.

(32) The top of the butadiene-rich column at 92.1% is dried on a sieve and purified by the extractive distillation methods in order to produce a butadiene fraction with a purity of 99.9%.

(33) Assessment of Butadiene Losses

(34) Exiting from the pyrolysis furnace, the series of separation steps implemented so as to purify the butadiene of the oxidized compounds and to recover the acetic acid for its recycling leads to a 99.98% butadiene recovery level. The butadiene losses are noted in the following streams and represent less than 1% of the final butadiene production:

(35) TABLE-US-00002 Loss of Butadiene Exiting Streams (kg/h) Bottom of gas-liquid water washing column (step d) 8.62 Purification by extractive distillation (step d) 168.7 TOTAL 177.4
Assessment of Acetic Acid Losses

(36) An addition of acetic acid is necessary for the esterification reaction because of acetic acid reaction losses. The loss of acetic acid (except for reaction losses) noted in the stream that eliminates the organic compounds such as MEK, CA, and MVCA remains insignificant (0.8 kg/h).

(37) The acetic acid losses at the pyrolysis furnace come from parasitic reactions. The MEK itself is not an acetic acid loss since the MEKEA releases a second acetic acid in transforming into MEK. The acetic acid also transforms into CO2 and CH4 that are found at the top of the butadiene purification section by cryogenic distillation or extractive distillation. Overall, the acetic acid reaction loss is 5,355 kg/h.