CN100509727C - Method for separating purifying polyatomic alcohol - Google Patents

Abstract

The invention relates to a method for separating and purifying low-level polyols, the main step of which is to separate and purify low-level polyols using a reaction-extraction coupling method. The reactant used is C ₁ ~ C ₆ aliphatic aldehyde; the extractant used is a five-membered or six-membered aliphatic ring, or a five-membered or six-membered aliphatic ring substituted by C ₁ ~ C ₆ alkyl; the Said lower polyols are C ₂ -C ₆ dihydric or trihydric alcohols, or mixtures thereof. The present invention overcomes the existing problems in the prior art (a) in the whole separation and purification process, the amount of aldehyde compounds (reactants) is too large, and is easily oxidized into corresponding carboxylic acids, causing corrosion of production equipment; (b) water Aldehyde compounds in the phase need to be recovered, resulting in increased operating costs for separation and purification, and defects such as wall sticking and coking during the separation and purification process.

Description

Method for Separating and Purifying Polyols

technical field

The present invention relates to a method for separation and purification of polyalcohols, in particular to a method for separating and purifying low-level polyalcohols by means of a reaction-extraction coupling method in the fermentation broth or reaction liquid which continuously prepares low-level polyols by fermentation or chemical synthesis. Alcohol method.

Background technique

Low-level polyols such as ethylene glycol, propylene glycol, butanediol, etc. are widely used chemical basic raw materials. In particular, 1,3-propanediol (1,3-PDO) is a raw material for producing polytrimethylene terephthalate with excellent properties.

So far, the methods for preparing lower polyols include fermentation and chemical synthesis. Taking the preparation of 1,3-propanediol as an example, the chemical synthesis method uses ethylene oxide as a raw material, under the action of a catalyst, reacts with synthesis gas (CO/H ₂ ) to generate 3-hydroxypropionaldehyde, and then converts 3-hydroxypropanal Propionaldehyde is catalytically hydrogenated to produce 1,3-propanediol; the fermentation method uses glycerol or glucose as a substrate, and is passed through Klebsiella pneumoniae, Citrobacter freundii or Clostridium butyric acid Bacillus (Clostridium butyricum) and other strains are fermented to obtain 1,3-propanediol. Whether it is fermentation method or chemical synthesis method, the concentration of its product is all low (generally below 150g/L reaction solution), and also contains some by-products, such as monohydric alcohol, acid (chemical synthesis method) and bacteria and residual Medium, etc. (fermentation method). Therefore, how to efficiently and cost-effectively separate and purify low-level polyols from low-concentration solutions has become a research hotspot in this field.

ZL 200410038300.5 and CN1634823A disclose a method for separating and purifying 1,3-propanediol using a reaction-extraction coupling method. Its existing defects are: (a) Since the aldehyde compound used is both a reactant and an extractant, the amount used in the extraction process is large, and it circulates in the system for a long time, so it is easily oxidized into the corresponding carboxylic acid, causing production equipment susceptible to corrosion. (b) These aldehyde compounds used have a certain solubility in water and need to be recovered by rectification, which increases the production cost. In addition, the method disclosed in CN1634823A also has problems such as wall sticking and coking, which affect the efficiency of separation and extraction of 1,3-propanediol.

Contents of the invention

The purpose of the present invention is to provide a method for separating and purifying lower polyols from the reaction solution of polyols prepared by fermentation or chemical synthesis, so as to overcome the defects in the prior art. That is: (a) in the whole separation and purification process, the amount of aldehyde compounds is too large, and is easily oxidized into corresponding carboxylic acids, causing corrosion of production equipment; (b) the aldehyde compounds in the water phase need to be recovered, resulting in separation and purification The operating cost increases, and there are defects such as wall sticking and coking in the separation and purification process.

The method for separating and purifying low-level polyols in the fermented liquid or reaction liquid that continuously prepares polyols by fermentation or chemical synthesis method of the present invention comprises the following steps:

(1) First, put the fermentation liquid or reaction liquid (obtained by chemical synthesis) containing lower polyols in the reaction extractor, and adjust its pH value to 1-5, and then add the reactant to the reaction extractor and extractant, react at 10-60°C for 10 minutes to 3 hours to obtain a two-phase substance composed of organic phase and water phase; phase, and the presence of reactants (aldehydes) was hardly detected in the aqueous phase.

(2) enter the rectifying tower by the organic phase of step (1) gained and separate, and the overhead fraction of rectifying tower enters extractant rectifying tower and separates again, and the tower top and tower still fraction of extractant rectifying tower Separate the reactant and extractant, which can be recycled; put the bottom fraction of the rectification tower in the hydrolysis reactor, and carry out the hydrolysis reaction under the condition of the presence of a strong acid ion exchange resin catalyst, and the reaction between water and lower polyols The molar ratio of the product (acetal) of the reagent reaction is (1-10): 1, the hydrolysis temperature is 80-150 ° C, the reactant (aldehyde compound) is exported from the upper part of the hydrolysis reactor, and returned to the reaction extractor for recycling; The product (lower polyol) is obtained after the product is separated by rectification;

Among them: the fermentation broth containing low-level polyols needs to be pretreated to remove bacteria before separation and purification (for example, flocculation or high-speed centrifugation can be used to remove bacteria); said low-level polyols are C ₂ ~ C ₆ binary or trihydric alcohol, or a mixture thereof; the reactant is a C ₁ to C ₆ aliphatic aldehyde; the extractant is a five-membered or six-membered aliphatic ring, or a C ₁ to C ₆ alkyl substituted Five- or six-membered aliphatic cycloalkanes.

In a preferred version of the present invention, the molar ratio of lower polyhydric alcohol and reactant is 1: (1～10), said reactant is _C3 ～ _C6 aliphatic aldehyde, better reactant is n-butyl Aldehyde, isobutyraldehyde, n-valeraldehyde or isovaleraldehyde;

In another preferred version of the present invention, the volume ratio of the extractant to the fermentation broth or reaction fluid (obtained by chemical synthesis) containing lower polyols is 1: (0.1 to 5), and the better volume ratio is 1: (1～5); said extractant is five-membered or six-membered aliphatic cycloalkane or six-membered aliphatic cycloalkane substituted by C ₁ ~C ₃ alkyl;

In yet another preferred version of the present invention, said lower polyols are C ₂ -C ₄ dihydric or trihydric alcohols, or mixtures thereof; more preferably lower polyols ethylene glycol, 1,2-propanediol , 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol or glycerol, or a mixture of two or more thereof.

In addition, in the present invention, the recommended reactive extractor is a sieve plate extraction tower, a pulse sieve plate extraction tower, a vibrating sieve plate extraction tower, a rotary disk extraction tower or a pulse packed tower with a mass transfer unit number of 3 to 10; it is recommended to use The hydrolysis reactor is a stirred tank reactor or a tubular reactor.

The polyhydric alcohol obtained by adopting the above-mentioned technical scheme has a purity of more than 99.5 wt%. The present invention can overcome the existing problems in the prior art (a) in the whole separation and purification process, the amount of aldehyde compounds is too large, and is easily oxidized into corresponding carboxylic acids, causing corrosion of production equipment; (b) aldehydes in the water phase The compound needs to be recovered (and in the present invention, the presence of the reactant (aldehyde compound) is hardly detected in the aqueous phase), which leads to an increase in the operating cost of separation and purification, and defects such as wall sticking and coking exist in the separation and purification process.

Description of drawings

Figure 1 is a schematic flow diagram of the continuous separation and purification of polyols from fermentation broth or chemical synthesis reaction fluid

Some symbols in Figure 1 are explained as follows:

5—reaction extractor, 6—acetal rectification tower, 9—extractant rectification tower, 13—hydrolysis reactor, 19—product rectification tower.

Detailed ways

Referring to accompanying drawing 1, the present invention is realized like this:

After pretreatment (such as flocculation, high-speed centrifugation, etc.), the polyol fermentation liquid or chemical synthesis reaction liquid enters the reaction extractor 5 through the pipe 1, and the recovered aldehyde reactant enters from the middle of the reaction extractor 5, and the recovered extractant enters from the middle of the reaction extractor 5. The lower part of the reaction extractor 5 enters. The extracted organic phase (containing extractant, cyclic acetal and aldehyde reactants generated by the reaction) flows out from the top of the reactive extractor and enters the acetal rectification tower 6, and the raffinate (substantially free of polyhydric alcohol and aldehyde reactants) matter) flows out from the bottom of the reaction extractor 5 through the pipe 3, and goes to the sewage treatment system. In the acetal rectification tower 6, normal pressure rectification, the reflux ratio is 0.5～10, the aldehyde reactant and the extractant come out from the top of the tower, and enter the extractant rectification tower 9 through the pipe 8; the bottom of the tower is a cyclic acetal, Enter the hydrolysis reactor 13 through the pipe 7. In the extractant rectifying tower 9, the aldehyde reactants and the extractant are separated, and the aldehyde reactants are discharged from the top of the tower, and the aldehydes produced by the pipe 10 and the hydrolysis reactor 13 are combined, and returned to the reaction extractor 5 through the pipe 11; The tower still of extractant rectifying tower 9 is extractant, returns in reaction extractor 5 through pump 12, pipe 4. In the hydrolysis reactor 13, the strong acidic resin is pre-entered as a catalyst, and the replenished water (with a cyclic acetal molar ratio of 1) enters the hydrolysis reactor 13 from the pipe 16, and the aldehyde reactant produced by the reaction passes from the pipe 14, After passing through the condenser 15, it is combined with the tube 10. The hydrolyzate enters the product rectifying tower 19 through the pump 18 from the pipe 17, and carries out rectification under reduced pressure at a pressure of 1 to 40 kPa and a reflux ratio of 1 to 20; Kettle polyol product exits via line 21.

Below by embodiment this is done further elaboration, and its purpose is only to better understand content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention:

Example 1

Composition of pretreated fermented liquid (production of 1,3-propanediol by fermentation method): 1,3-propanediol 62g/L, 2,3-butanediol 15g/L, ethanol 5g/L, soluble protein 0.5g/L, OD value 6.0, pH 7.0.

(1) Adjust the pH of the pretreated fermentation broth to 4.0 with sulfuric acid or hydrochloric acid.

(2) The fermented liquid enters from the upper part of the reactive extractor, and the reactant n-butyraldehyde (including replenished and recovered) enters from the middle of the reactive extractor. The amount of reactant n-butyraldehyde and the mol ratio of polyalcohol in the feed liquid are 2.0: 1.0, and the extractant methylcyclohexane enters from the bottom of the reaction extractor, compared to 0.5 (extractant and feed liquid volume ratio (0.2 ～3.0:1), the organic phase flows out from the top of the reaction extractor, and the temperature in the reaction extractor is 30～40°C. The reaction extractor adopts a rotary disk extraction tower, and 5-stage extraction. 1,3-propanediol, 2,3-butane The conversion rate of diol is all above 99%, the recovery rate of acetal in the organic phase is above 98%, only 0.04% of butyraldehyde in the water phase, and does not contain methylcyclohexane.

(3) Put the organic phase in the step (1) into the ring-shaped acetal rectification column continuously, with wire mesh packing inside, the number of trays is 20, the reflux ratio is 0.4, the temperature at the top of the tower is 85°C, and the reactant butyraldehyde is discharged from the top of the tower and toluene, the bottom of the tower is a cyclic acetal with a content of more than 99%.

(4) Put the top material in step (2) into the extraction agent rectification tower, with wire mesh packing inside, rectification at atmospheric pressure, with a theoretical plate number of 50, a reflux ratio of 2.0, a top temperature of 77°C, and distillate from the top of the tower The n-butyraldehyde, the tower kettle is methylcyclohexane, which is returned to the reaction extractor for recycling.

(5) Put the cyclic acetal in step (2) into the hydrolysis reactor continuously, add 1:1 water (molar ratio of water to dioxane), and enter together with the circulating water (2:1) In the hydrolysis reactor, the hydrolysis reactor adopts a stirred tank type, the residence time is 1h, and a strong acid ion exchange resin (HD-8) is used as a catalyst in the hydrolysis reactor, and the hydrolysis temperature is 120°C. The butyraldehyde produced by hydrolysis comes out from the top of the reaction kettle, and returns to the reaction extractor after being condensed. The hydrolysis conversion rate of the cyclic acetal is over 99%.

(6) The hydrolyzate in the step (4) enters the product rectifying tower continuously from the middle, with wire mesh packing inside, the number of trays is 50, rectification under reduced pressure, the pressure is 1 ~ 40kPa, the reflux ratio is 5, and the tower top temperature is 43 ℃. Water is discharged from the top of the tower, and the bottom of the tower is a mixture of 1,3-propylene glycol and 2,3-butanediol. After being separated by a subsequent rectification tower, 2,3-butanediol product with a purity of 99.5wt% is discharged from the top of the tower, and 1,3-propanediol product with a purity of 99.7wt% or more is produced at the bottom of the tower.

Example 2

Composition of the pretreated fermentation broth (production of 2,3-butanediol by fermentation): 84 g/L of 2,3-butanediol, 10.5 g/L of 3-hydroxybutanone, 18 g/L of glucose, pH 7.0.

(1) Adjust the pH value of the pretreated fermentation broth to 3.0 with sulfuric acid or hydrochloric acid.

(2) The fermented liquid enters from the upper part of the reactive extractor, and the reactant n-butyraldehyde (including replenished and recovered) enters from the middle of the reactive extractor. The amount of reactant n-butyraldehyde and the mol ratio of polyalcohol in the feed liquid are 2.0: 1.0, and the extractant methylcyclohexane enters from the bottom of the reaction extractor, compared to 0.5 (extractant and feed liquid volume ratio (0.2 ～3.0: 1), the organic phase flows out from the top of the reaction extractor, and the temperature in the reaction extractor is 30～40 ℃. The reaction extractor adopts a rotating disk extraction tower, and 5 stages of extraction. The conversion rate of 2,3-butanediol is The recovery rate of the cyclic acetal in the organic phase is above 99%, the recovery rate of the cyclic acetal is above 98%, and there is only 0.05% of butyraldehyde in the water phase and does not contain methylcyclohexane.

(3) Put the organic phase in step (1) into the ring-shaped acetal rectification column continuously, with wire mesh packing inside, the number of trays is 20, the reflux ratio is 0.4, the temperature at the top of the tower is 80°C, and the reactant butyraldehyde is discharged from the top of the tower and extractant toluene, the bottom of the tower is a cyclic acetal with a content of more than 99%.

(4) Put the top material in the step (2) into the extraction agent rectification tower, with wire mesh packing inside, rectification at atmospheric pressure, the number of theoretical plates is 60, the reflux ratio is 2.0, the temperature at the top of the tower is 77 ° C, and the top of the tower is distilled The n-butyraldehyde, the tower kettle is methylcyclohexane, which is returned to the reaction extractor for recycling.

(5) Continuously pour the cyclic acetal in step (2) into the hydrolysis reactor, add 1:1 water (the molar ratio of water to cyclic acetal), together with the circulating water (2:1) Into the hydrolysis reactor, the hydrolysis reactor is a stirred tank type, the residence time is 1h, there is a strong acid ion exchange resin (D72) as a catalyst, and the hydrolysis temperature is 110°C. The butyraldehyde produced by hydrolysis comes out from the top of the reaction kettle, and returns to the reaction extractor after being condensed. The hydrolysis conversion rate of the cyclic acetal is over 99%.

(6) The hydrolyzate in the step (4) is continuously entered into the polyol rectification tower from the middle, with wire mesh packing inside, the number of trays is 50, rectification under reduced pressure, the pressure is 1 ~ 40kPa, the reflux ratio is 5, and the tower top temperature 43°C. Water is discharged from the top of the tower, and the bottom of the tower is 2,3-butanediol with a purity of more than 99.7 wt%.

Example 3

1,3-propanediol solution (containing 10.5 wt% of 1,3-propanediol) synthesized by chemical method.

(1) The 1,3-propanediol dilute solution synthesized by the chemical method is adjusted to a pH value of 2.5 with sulfuric acid or hydrochloric acid.

(2) The 1,3-propanediol dilute solution enters from the upper part of the reaction extractor, and the reactant isobutyraldehyde (including replenished and recovered) enters from the middle part of the reaction extractor. The amount of reactant n-butyraldehyde and feed liquid, the mol ratio of 1,3-propanediol is 2.0: 1.0, and extraction agent hexanaphthene enters from the bottom of reaction extractor, is 0.6 (extraction agent and feed liquid volume ratio ( 0.2～3.0: 1), the organic phase flows out from the top of the reaction extractor, and the temperature in the reaction extractor is 30～40 ℃.The reaction extractor adopts the rotary disk extraction tower, 6 grades of extractions. The conversion rate of 1,3-propanediol is all in More than 98%, the recovery rate of cyclic acetal in the organic phase is more than 98%, only 0.03% of isobutyraldehyde and 0.01% of cyclohexane in the water phase.

(3) The organic phase in step (1) is continuously poured into the circular acetal rectification column, with wire mesh packing inside, the number of trays is 30, the reflux ratio is 1.0, the temperature at the top of the tower is 75°C, and the reactant isobutylate is discharged from the top of the tower Aldehyde and extractant cyclohexane, the bottom of the tower is a cyclic acetal with a content of more than 99%.

(4) Put the top material in the step (2) into the extraction agent rectification tower, with wire mesh packing inside, rectification at atmospheric pressure, the number of theoretical plates is 60, the reflux ratio is 2.0, the temperature at the top of the tower is 66 ° C, and the top of the tower is distilled Isobutyraldehyde, the tower kettle is cyclohexane, and returns to the reaction extractor for recycling.

(5) Continuously pour the cyclic acetal in step (2) into the hydrolysis reactor, add 1:1 water (the molar ratio of water to cyclic acetal), together with the circulating water (2:1) Into the hydrolysis reactor, the hydrolysis reactor is a stirred tank type, the residence time is 1h, there is a strong acid ion exchange resin (Amberlyst15) as a catalyst, and the hydrolysis temperature is 100°C. The isobutyraldehyde produced by hydrolysis comes out from the top of the reaction kettle, and returns to the reaction extractor after being condensed. The hydrolysis conversion rate of the cyclic acetal is above 99.5%.

(6) The hydrolyzate in the step (4) is continuously entered into the polyol rectification tower from the middle, with wire mesh packing inside, the number of trays is 50, rectification under reduced pressure, the pressure is 1 ~ 40kPa, the reflux ratio is 4, and the tower top temperature 43°C. Water is discharged from the top of the tower, and the bottom of the tower is 1,3-propanediol with a purity of more than 99.8 wt%.

Embodiment 4～10

Different products were separated and purified with different reactants and extractants (the separation and purification conditions were the same as in the examples except the reactants and extractants). The results of the separation and purification are shown in Table 1.

Table 1

Claims (8)

1. A method for separating and purifying low-level polyols from fermented liquid or reaction liquid that continuously prepares polyols by fermentation or chemical synthesis, is characterized in that said method comprises the following steps: (1) First, place the fermented liquid or reaction liquid containing lower polyols in a reaction extractor, and adjust its pH value to 1 to 5, then add reactant and extractant to the reaction extractor, at 10°C React at ~60°C for 10 minutes to 3 hours to obtain a two-phase product consisting of an organic phase and an aqueous phase; (2) enter the rectifying tower by the organic phase of step (1) gained and separate, and the overhead fraction of rectifying tower enters extractant rectifying tower and separates again, and the tower top and tower still fraction of extractant rectifying tower They are respectively reactant and extractant, which can be recycled; the bottom fraction of the rectification tower is placed in the hydrolysis reactor, and the hydrolysis reaction is carried out under the condition of the presence of a strong acidic ion exchange resin catalyst, water and lower polyols and The molar ratio of the reaction product of the reactant is (1-10): 1, the hydrolysis temperature is 80°C-150°C, the reactant is exported from the upper part of the hydrolysis reactor, and returned to the reaction extractor for recycling; the hydrolyzate is separated by rectification to obtain product; Among them: the fermentation broth containing low-level polyols needs to be pretreated to remove bacteria before separation and purification; the low-level polyols are dihydric or trihydric alcohols of C ₂ ~ C ₆ ; the reactant is C ₁ ~C ₆ aliphatic aldehyde; said extractant is five- or six-membered aliphatic cycloalkane, or five- or six-membered aliphatic cycloalkane substituted by C ₁ -C ₆ alkyl. 2. The method according to claim 1, wherein the molar ratio of the lower polyol to the reactant is 1: (1-10). 3. The method according to claim 1 or 2, wherein said reactant is C ₃ -C ₆ aliphatic aldehyde. 4. The method of claim 3, wherein said reactant is n-butyraldehyde, isobutyraldehyde, n-valeraldehyde or isovaleraldehyde. 5. The method according to claim 1, wherein the volume ratio of the extractant to the fermentation liquid or reaction liquid containing lower polyols is 1: (0.1-5). 6. The method according to claim 1 or 5, wherein said extractant is a six-membered aliphatic cycloalkane or a six-membered aliphatic cycloalkane substituted by a C ₁ -C ₃ alkyl group. 7. The method according to claim 1, 2 or 5, characterized in that said lower polyhydric alcohol is a C ₂ -C ₄ dihydric or trihydric alcohol. 8. The method according to claim 7, wherein said lower polyols are ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3 - butanediol, 2,3-butanediol or glycerol.

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