CN112062737A - Method for extracting epichlorohydrin - Google Patents

Abstract

The invention discloses a method for extracting epoxy chloropropane, which is characterized by comprising the following steps: centrifugal extraction and tower extraction are connected in series, and an extraction oil layer separated after tower extraction enters centrifugal extraction. The method greatly shortens the extraction time, ensures that the oil-water phase is clear and has no entrainment, and solves the problem of separation of two materials with approximate density difference; the tower-type extraction oil layer (light phase II) can be recycled to the centrifugal extraction process, and the dosage of the extractant 3-chloropropene is reduced by more than 50%.

Description

Method for extracting epichlorohydrin

Technical Field

The invention belongs to the technical field of organic chemical industry, and relates to an extraction method of epoxy chloropropane in an aqueous phase, in particular to a method for recovering epoxy chloropropane in the aqueous phase by a composite extraction mode combining centrifugal extraction and tower extraction.

Background

Epichlorohydrin is an important basic chemical raw material and is mainly applied to the production of various products such as epoxy resin, epichlorohydrin rubber, glycerol, surfactants and the like. The existing industrial production method of epoxy chloropropane mainly comprises 2 methods: the chlorohydrin process and the glycerol process. The main reaction process of the chlorohydrination method comprises three steps of chlorination of propylene at high temperature to obtain chloropropene, hypochlorination of the chloropropene to obtain dichloropropanol, and saponification of the dichloropropanol to obtain epichlorohydrin. The chlorohydrin method has the disadvantages of severe corrosion of equipment and serious environmental pollution, and generates about 40 tons of salt-containing wastewater per ton of epichlorohydrin. The main reaction process of the glycerol method mainly comprises two steps of chlorination and saponification. The glycerol method has fewer byproducts and mild operation conditions, but the production capacity of the epichlorohydrin is greatly limited by the raw material glycerol.

The development of a clean production process of epoxy chloropropane has become an inevitable requirement of times development, and the use of hydrogen peroxide as a green oxygen source is a hot research point of olefin catalytic epoxidation in recent years. The process for synthesizing epichlorohydrin by using the titanium silicalite molecular sieve as the catalyst becomes a research hotspot due to the advantages of high selectivity, less ineffective decomposition of hydrogen peroxide and the like. The reaction liquid (separated catalyst) contains 3-chloropropene, methanol, epichlorohydrin, water and impurities, and the epichlorohydrin in the water phase is transferred to the oil phase by adopting an extraction method generally.

CN103772326B introduces a kettle-type epichlorohydrin synthesis method, wherein reaction liquid is extracted by double towers, chloropropene and water are respectively adopted as extracting agents to obtain an extraction phase rich in epichlorohydrin, but the consumption of chloropropene in the method is large, and in addition, the density difference of an extracted oil-water phase is very close to that of the chloropropene (less than 0.02g/mL) due to the density of 0.94g/mL, so that the method is easy to emulsify and difficult to delaminate, needs to be stood for a long time, and has low production efficiency; CN103420946A, also adopts tower extraction, adopts other extraction agents (such as halogenated ether compounds, halogenated ester compounds, halogenated carbonyl compounds, etc.), has improved the density difference of oil aqueous phase, is convenient for oil water layering, but the system introduces other substances, on the one hand increases the separation difficulty, on the other hand may bring other impurities or take place the side reaction, influence product quality.

The adoption of 3-chloropropene as an extracting agent is suitable, but a solution for solving the problems of small density difference, long treatment time, low production efficiency and the like needs to be found.

Disclosure of Invention

The invention aims to solve the problems of small oil-water phase density difference and difficult separation when 3-chloropropene is used as an extractant. The invention provides a composite extraction method combining centrifugal extraction and tower extraction to recover epoxy chloropropane in an aqueous phase, and the method has the advantages of fast layering and high extraction efficiency.

A method for extracting epichlorohydrin adopts centrifugal extraction and tower extraction in series, and an extraction oil layer separated after the tower extraction enters the centrifugal extraction. The method specifically comprises the following steps:

(1) pumping the phase to be extracted and a first extracting agent into a centrifugal extractor respectively by adopting two metering pumps, mixing and separating, and then obtaining a light phase I and a heavy phase I from light phase and heavy phase discharge ports respectively;

(2) pumping the heavy phase I obtained in the step (1) into a heavy phase inlet and a light phase inlet of an extraction tower respectively, flowing in the extraction tower from top to bottom, and carrying out countercurrent contact with a second extractant to obtain a light phase II and a heavy phase II from heavy phase outlets and light phase outlets;

(3) pumping the light phase II in the step (2) into a centrifugal extractor.

Preferably, the first extractant in step (1) comprises the light phase II in step (2).

Preferably, the mass ratio of the phase to be extracted to the first extractant feeding in the step (1) is 6-3: 1, preferably 4: 1.

preferably, the centrifugal extraction temperature in the step (1) is 0-50 ℃, and preferably 5-30 ℃.

Process for the extraction of epichlorohydrin according to claim 2, characterized in that: the retention time of the centrifugal extraction in the step (1) is 10-120 s, preferably 30-60 s.

Preferably, the rotation speed of the centrifugal extraction in the step (1) is 3000-4000 rpm.

Preferably, the mass ratio of the heavy phase I to the second extractant feed in the step (2) is 6-3: 1, preferably 4: 1

Preferably, the residence time of the tower extraction in the step (2) is 30-120 min, preferably 30-60 min.

Preferably, the method is characterized in that: the phase composition to be extracted comprises 0-10% of epoxy chloropropane, 0-30% of methanol, 0-8% of 3-chloro-1, 2-propylene glycol, 0-1% of 1-chloro-3-methoxy-2-propanol, 0-0.3% of 3-chloro-2-methoxy-1-propanol, 0-0.3% of 1, 2-epoxy-5-hexene and 0-0.05% of methyl glycidyl ether.

The invention has the beneficial effects that: (1) the extraction time is greatly shortened, the oil-water phase is ensured to be clear and has no entrainment, and the problem of separation of two materials with approximate density difference is solved;

(2) the tower-type extraction oil layer, namely the light phase II can be recycled to the centrifugal extraction process, and the dosage of the extractant 3-chloropropene is reduced by more than 50 percent.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

Fig. 1 is a flow chart of the extraction process of epichlorohydrin.

Detailed Description

The following detailed description further describes the present invention for the purpose of illustrating the technical solutions and objects of the present invention.

In the present invention, the heavy phase refers to a liquid phase with relatively high density in two phases formed after liquid-liquid separation, and the light phase refers to a liquid phase with relatively low density in two phases formed after liquid-liquid separation.

The method for extracting epichlorohydrin provided by the invention adopts a centrifugal extraction and tower extraction series connection, adopts two metering pumps to respectively pump a phase to be extracted and a first extractant into a centrifugal extractor, can also enter the centrifugal extractor through one metering pump after the phase to be extracted and the first extractant are mixed in advance according to a proportion, can obtain the material flow containing the first extractant and the phase to be extracted by mixing the phase to be extracted and the first extractant in various mixing devices commonly used in the field, and the mixing device can be a pipeline mixer or a stirring kettle, preferably a pipeline mixer. For convenience of operation, it is preferred to pump the centrifugal extractants separately and mix them.

The mass ratio of the phase to be extracted to the first extractant fed into the centrifugal extractor is 6-3: 1, preferably 4: 1, can also be 5: 1, the centrifugal extraction temperature is 0-50 ℃, preferably 5-30 ℃, particularly 10 ℃, 20 ℃, 30 ℃, 40 ℃ and 50 ℃, the retention time of the centrifugal extraction is 10-120 s, preferably 30-60 s, particularly 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s and 120s, and the rotational speed of the centrifugal extraction is 3000 plus 4000rpm, particularly 3000rpm, 3500rpm and 4000 rpm. After centrifugal extraction, mixing and separation, respectively obtaining a light phase I and a heavy phase I from light phase and heavy phase discharge ports;

in the invention, the first extractant in the centrifugal extractor is 3-chloropropane, wherein the 3-chloropropane in the first extractant during the first extraction is a commercially available product, and the brand and the source are not limited so as to meet the commercially available purity standard; after the tower-type extraction is finished, the light phase flowing out of the extraction tower is mainly 3-chloropropane, the light phase mainly refers to that the mass ratio of the 3-chloropropane in the light phase collected by the extraction tower accounts for more than 90%, if the light phase is repeatedly used, the mass ratio of the 3-chloropropane is reduced, or the mass ratio of methanol and the like is too high, the 3-chloropropane can be separated by adopting a fractionation or rectification process, the process is not limited, and any general process can be adopted for fractionation to recover the 3-chloropropane.

The light phase I is 3-chloropropene containing epichlorohydrin after centrifugal extraction; wherein, the epichlorohydrin accounts for 70-85% of the mass of the epichlorohydrin in the phase to be extracted, namely the extraction efficiency of centrifugal extraction is 70-85%, 15-30% of the epichlorohydrin still exists in the heavy phase I after the centrifugal extraction, and the rest is water, methanol and the like, and the part of the heavy phase I enters the tower extraction step.

In the invention, the heavy phase I and the second extractant obtained in the step (1) are respectively pumped into a heavy phase inlet and a light phase inlet of an extraction tower, and the mass ratio of the heavy phase I to the second extractant is 6-3: 1, when the ratio of the heavy phase I and the second extractant is outside the above range, liquid-liquid separation is difficult to achieve in the extraction column. From the viewpoint of further increasing the extraction rate of epichlorohydrin and further reducing the methanol content in the finally obtained liquid phase containing epichlorohydrin, the ratio of 4: 1. the purity of 3-chloropropene as second extractant may be conventionally selected, and in general, the purity of 3-chloropropene as second extractant may be from 95 to 100% by weight, preferably from 97 to 99% by weight.

In the invention, the heavy phase I enters from a heavy phase inlet of the extraction tower, usually the heavy phase inlet is arranged at the upper end of the extraction tower, and the heavy phase I flows from top to bottom after entering the extraction tower; the second extractant enters from a light phase inlet of the extraction tower, the light phase inlet is usually arranged at the lower end of the extraction tower, the second extractant is in countercurrent contact with the heavy phase I from bottom to top, and the retention time of tower extraction is 30-120 min, preferably 30-60 min. Flows from top to bottom in the extraction tower, and is in countercurrent contact with a second extractant, and a light phase II and a heavy phase II are obtained from heavy phase and light phase outlets.

According to the extraction method provided by the invention, the temperature of the countercurrent contact in the extraction tower can be selected conventionally in the field, so that the effect of extraction and separation can be realized, and the probability of side reaction of the epoxy chloropropane in the extraction and separation process can be reduced to the minimum. In general, it can be carried out at a temperature of from-10 ℃ to 50 ℃. From the viewpoint of convenience in operation and economy, the reaction can be carried out at a temperature of 10 to 40 ℃.

The light phase II obtained by tower extraction can be pumped into a liquid storage tank and used as a supplement of a first extracting agent in the centrifugal extraction process; and in the centrifugal extraction process, the light phase II after tower extraction is used limitedly, and when the quantity of the light phase II is not enough to match the mass ratio requirement of the first extractant and the phase to be extracted in the centrifugal extraction, 3-chloropropene is added from the outside to meet the mass ratio requirement of the first extractant and the phase to be extracted.

The light phase II obtained by tower extraction is used as the first extractant of centrifugal extraction, 3-chloropropene is recycled, the total consumption of 3-chloropropene is greatly saved, and about 50% is saved.

And (3) the heavy phase II after tower extraction contains less than 0.03% of epichlorohydrin.

The extraction column according to the extraction method of the present invention may be any of various apparatuses capable of performing an extraction function, such as a sieve plate column, a packed column, a rotating disc column or a float valve column, which are generally used in the art, and is preferably an empty column without a member.

The phase composition to be extracted comprises 0-10% of epoxy chloropropane, 0-30% of methanol, 0-8% of 3-chloro-1, 2-propanediol, 0-1% of 1-chloro-3-methoxy-2-propanol, 0-0.3% of 3-chloro-2-methoxy-1-propanol, 0-0.3% of 1, 2-epoxy-5-hexene and 0-0.05% of methyl glycidyl ether.

According to the extraction process of the present invention, the source of the solution containing epichlorohydrin, methanol, 3-chloropropene and water is not particularly limited, and can be obtained by various conventional processes for producing epichlorohydrin. For example, hydrogen peroxide and 3-chloropropene may be contacted in methanol in the presence of a titanium silicalite under epoxidation conditions to provide the solution comprising epichlorohydrin, methanol, 3-chloropropene, and water.

According to the extraction process of the invention, the light phase I can be subjected to distillation, using methods conventional in the art, in order to separate epichlorohydrin and 3-chloropropene. The separated 3-chloropropene can be sent to an epoxy reaction unit to be used as a raw material for epoxidation reaction, and can also be sent to a first extraction tower to be used as a second extractant; the separated epichlorohydrin can be directly output or sent into a refining unit for further refining and then output. The conditions for distilling the light phase I are not particularly limited in the present invention, and may be selected conventionally in the art, and are not described herein again.

In the following examples and comparative examples, the content of epichlorohydrin in the light phase I and the light phase II was determined as the solution containing epichlorohydrin, methanol, 3-chloropropene and water as the extract to be extracted by means of a chromatographic analysis method.

In the following examples and comparative examples, the extraction rate of epichlorohydrin was calculated using the following formula:

the extraction rate (%) of epichlorohydrin is (weight of epichlorohydrin in the light phase/weight of epichlorohydrin contained in the phase to be extracted) × 100%.

Example 1

(1) A first extractant # and a phase to be extracted (3.57 percent of epoxy chloropropane, 19.64 percent of methanol, 0.68 percent of 3-chloro-1, 2-propanediol, 0.47 percent of 1-chloro-3-methoxyl-2-propanol and the like) are respectively pumped into a light phase inlet and a heavy phase inlet of a CTL-350 type centrifugal extractor by two metering pumps, the weight ratio of a feed oil phase to a water phase is 1/4, the rotating speed is adjusted to 3000rpm, the retention time is 60s, and the light phase I # and the heavy phase I # obtained from a light phase extraction outlet and a heavy phase extraction outlet at the jacket temperature of 30 ℃ are clear and transparent without entrainment. Heavy phase I # composition: 0.67% of epichlorohydrin, 20.63% of methanol, 0.68% of 3-chloro-1, 2-propanediol, 0.42% of 1-chloro-3-methoxy-2-propanol and 81% of centrifugal extraction efficiency.

(2) The heavy phase I # is extracted in a tower type by adopting an extraction tower (with a built-in structured packing), the extraction temperature is 30 ℃, the retention time is 60min, and the heavy phase I # is: 3-chloropropene ═ 4: 1 (weight ratio), the raffinate 2# is obtained from the bottom of the tower, the components are 0.03 percent of epoxy chloropropane, 20.17 percent of methanol, 0.65 percent of 3-chloro-1, 2-propanediol and 0.3 percent of 1-chloro-3-methoxyl-2-propanol, the extraction efficiency of the tower type extraction is about 18.3 percent, and the total efficiency of the combined extraction is 99.3 percent.

Example 2

(1) The first extractant # and the phase to be extracted (6.57% of epichlorohydrin, 29.21% of methanol, 1.28% of 3-chloro-1, 2-propanediol, 0.23% of 1-chloro-3-methoxy-2-propanol and the like) are respectively pumped into the light phase inlet and the heavy phase inlet of a CTL-350 type centrifugal extractor by two metering pumps, the weight ratio of the feeding oil phase to the water phase is 1/3, the rotating speed is adjusted to be 3200rpm, the retention time is 30s, and the light phase I # and the heavy phase I # obtained from the light phase extraction outlet and the heavy phase extraction outlet at the jacket temperature of 40 ℃ are clear and transparent without entrainment. Heavy phase I # composition: 0.87 percent of epichlorohydrin, 30.63 percent of methanol, 1.37 percent of 3-chloro-1, 2-propanediol, 0.21 percent of 1-chloro-3-methoxy-2-propanol and 84.2 percent of centrifugal extraction efficiency.

(2) The heavy phase I # is extracted in a tower type by adopting an extraction tower (with a built-in structured packing), the extraction temperature is 40 ℃, the retention time is 30min, and the heavy phase I # is: 3-chloropropene ═ 3: 1 (weight ratio), the raffinate 2# is obtained from the bottom of the tower, the components are 0.09% of epoxy chloropropane, 30.17% of methanol, 1.25% of 3-chloro-1, 2-propanediol and 0.28% of 1-chloro-3-methoxy-2-propanol, the extraction efficiency of the tower extraction is about 14.4%, and the total efficiency of the combined extraction is 98.6%.

Example 3

(1) The first extractant # and the phase to be extracted (epichlorohydrin 1.52%, methanol 10.29%, 3-chloro-1, 2-propanediol 0.54%, 1-chloro-3-methoxy-2-propanol 0.38%, etc.) are respectively pumped into the light phase inlet and the heavy phase inlet of a CTL-350 type centrifugal extractor by two metering pumps, the weight ratio of the feed oil phase to the water phase is 1/6, the rotation speed is adjusted to 3500rpm, the retention time is 120s, and the light phase I # and the heavy phase I # obtained from the light phase outlet and the heavy phase outlet at the jacket temperature of 25 ℃ are clear and transparent without entrainment. Heavy phase I # composition: 0.33 percent of epichlorohydrin, 10.62 percent of methanol, 0.49 percent of 3-chloro-1, 2-propanediol, 0.32 percent of 1-chloro-3-methoxy-2-propanol and 78.3 percent of centrifugal extraction efficiency.

(2) The heavy phase I # is extracted in a tower type by adopting an extraction tower (with a built-in structured packing), the extraction temperature is 25 ℃, the retention time is 120min, and the heavy phase I # is: 3-chloropropene ═ 6: 1 (weight ratio), the raffinate 2# is obtained from the bottom of the tower, the components are 0.02 percent of epoxy chloropropane, 10.17 percent of methanol, 0.52 percent of 3-chloro-1, 2-propanediol and 0.28 percent of 1-chloro-3-methoxy-2-propanol, the extraction efficiency of the tower extraction is about 20.4 percent, and the total efficiency of the combined extraction is 98.7 percent.

Examples 4 to 8

The reaction procedure was as in example 1, and the influence of different conditions on the reaction results was examined

Comparative example 1 kettle extraction

Adding 500kg of 3-chloropropene and 1000kg of reaction water (3.57% of epoxy chloropropane, 19.64% of methanol, 0.68% of 3-chloro-1, 2-propylene glycol, 0.47% of 1-chloro-3-methoxy-2-propanol and the like) into a 2000L reaction kettle, heating and stirring (300rpm) to 30 ℃, preserving heat and mixing for 60min, then entering a delayer to stand and stratify, obtaining a clear oil layer and an emulsified water layer after 30min, separating the emulsified water layer, standing for 30min, gradually clearing the emulsified water layer, taking out the lower water layer to analyze the content of the epoxy chloropropane to be 1.08%, and extracting the efficiency to be 70%.

Comparative example 2 column extraction

A12 m extraction tower is adopted, the height-diameter ratio is about 10, structured packing is filled in, 1000kg of reaction water (3.57% of epoxy chloropropane, 19.64% of methanol, 0.68% of 3-chloro-1, 2-propylene glycol, 0.47% of 1-chloro-3-methoxy-2-propanol and the like) and 500kg of 3-chloropropene are pumped by two metering pumps from the middle upper part and the middle lower part respectively, and the retention time is 120 min. And respectively extracting an extraction oil layer and a raffinate water layer from the top and the bottom of the extraction tower. The raffinate layer was slightly turbid, with 0.44% epichlorohydrin and 84.8% extraction efficiency.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A method for extracting epichlorohydrin is characterized in that: centrifugal extraction and tower extraction are connected in series, and an extraction oil layer separated after tower extraction enters centrifugal extraction.

2. Process for the extraction of epichlorohydrin according to claim 1, characterized in that: the method comprises the following steps:

(1) respectively putting the phase to be extracted and a first extracting agent into a centrifugal extractor, and respectively obtaining a light phase I and a heavy phase I after mixing and separating;

(2) enabling the heavy phase I obtained in the step (1) to flow from top to bottom in an extraction tower and to be in countercurrent contact with a second extractant to obtain a light phase II and a heavy phase II;

(3) pumping the light phase II in the step (2) into a centrifugal extractor.

3. Process for the extraction of epichlorohydrin according to claim 2, characterized in that: the first extractant in the step (1) comprises the light phase II in the step (2).

4. Process for the extraction of epichlorohydrin according to claim 3, characterized in that: in the step (1), the mass ratio of the phase to be extracted to the feeding material of the first extractant is 6-3: 1, preferably 4: 1.

5. process for the extraction of epichlorohydrin according to claim 2, characterized in that: the centrifugal extraction temperature in the step (1) is 0-50 ℃, and preferably 5-30 ℃.

6. Process for the extraction of epichlorohydrin according to claim 2, characterized in that: the retention time of the centrifugal extraction in the step (1) is 10-120 s, preferably 30-60 s.

7. Process for the extraction of epichlorohydrin according to claim 2, characterized in that: the rotation speed of the centrifugal extraction in the step (1) is 3000-4000 rpm.

8. Process for the extraction of epichlorohydrin according to claim 2, characterized in that: the mass ratio of the heavy phase I to the second extractant feeding in the step (2) is 6-3: 1, preferably 4: 1.

9. process for the extraction of epichlorohydrin according to claim 2, characterized in that: the residence time of the tower extraction in the step (2) is 30-120 min, preferably 30-60 min.

10. Process for the extraction of epichlorohydrin according to any one of claims 2 to 8, characterized in that: the phase composition to be extracted comprises 0-10% of epoxy chloropropane, 0-30% of methanol, 0-8% of 3-chloro-1, 2-propylene glycol, 0-1% of 1-chloro-3-methoxy-2-propanol, 0-0.3% of 3-chloro-2-methoxy-1-propanol, 0-0.3% of 1, 2-epoxy-5-hexene and 0-0.05% of methyl glycidyl ether.

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