阅读说明：本技术 一种环保型裂解c5馏分的分离方法 (Separation method of environment-friendly cracking C5 fraction ) 是由 景利娟 于芳洁 杨素青 杜梅慧 于 2021-06-09 设计创作，主要内容包括：本发明涉及一种环保型裂解C5馏分的分离方法,第一步采用萃取精馏分离出轻组分,分理处的轻组分中烯烃较少,可不做进一步处理,节约成本；第二步采用普通精馏重组分,得到高纯度及高回收率的异戊二烯、间戊二烯和环戊烯,投入进一步的工业生产；本发明涉及得C5馏分的分离方法中应用的萃取剂为N-甲基吡咯烷酮毒性较低且对C5混合物有良好的分离性和溶解性,本发明回收的异戊二烯、间戊二烯和环戊烯回收率高、纯度高,且回收过程中萃取剂循环利用,毒副作用小,对环境友好,整个流程能耗低。(The invention relates to a separation method of environment-friendly cracked C5 fraction, which comprises the following steps of separating light components by extractive distillation, wherein the light components are treated by separation with less olefin, so that no further treatment is needed, and the cost is saved; secondly, common rectification heavy components are adopted to obtain isoprene, piperylene and cyclopentene with high purity and high recovery rate, and the isoprene, the piperylene and the cyclopentene are put into further industrial production; the extractant used in the separation method for obtaining the C5 fraction has low toxicity of N-methyl pyrrolidone and good separability and dissolubility for a C5 mixture, the recovery rate and the purity of the recovered isoprene, piperylene and cyclopentene are high, the extractant is recycled in the recovery process, the toxic and side effects are small, the method is environment-friendly, and the energy consumption of the whole process is low.)

1. An environment-friendly separation method of cracking C5 fraction, which is characterized by comprising the following steps:

s1: adding a mixture of an extracting agent N-methyl pyrrolidone and water to the bottom of each rectifying tower and the tower kettle 1/2, and adding mixed carbon five fractions to the tower kettle 2/3;

s2: heating the tower kettle, respectively maintaining the temperature and the voltage of each section of the rectifying tower from bottom to top, and introducing condensed water;

s3: after each tower has reflux, the full reflux operation is kept;

s4: starting each feeding and discharging pump, continuously conveying materials into the tower, and keeping full reflux operation;

s5: when the conditions in the tower are stable, the tower top is refluxed;

s6: keeping each tower operating stably, recording temperature, sampling and measuring the discharge composition of each tower;

s7: stopping heating after the temperature of the whole tower and the composition of discharged materials are stable, discharging materials in each tower kettle when the materials are cooled to room temperature, stopping condensing water, and turning off power to obtain heavy components of the C5 distillate liquid with light components removed;

s8: and carrying out common rectification and extraction agent recovery on the heavy components of the obtained C5 distillate liquid without the light components to obtain isoprene, piperylene and cyclopentene.

2. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the weight of water in the extractant of step S1 is preferably 4% of the weight of N-methylpyrrolidone.

3. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the total reflux time in step S3 was 20 min.

4. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the pressure for separating pentane and pentene by ordinary rectification is 2atm, the theoretical plate number is 50, the extractant is fed from the 4 th plate, the C5 is fed from the 33 rd plate, the reflux ratio is 1.8, and the solvent ratio is 6.

5. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: in step S8, the pressure of the recovered extractant is 2atm, the theoretical plate number is 10, the 5 th plate is fed, and the reflux ratio is 1.

6. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the pressure is 2atm when isoprene is separated by ordinary rectification, the theoretical plate number is 90, the 45 th plate is fed, and the reflux ratio is 30.

7. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the pressure for separating piperylene and cyclopentene by ordinary rectification is 2atm, the theoretical plate number is 70, the 40 th plate is fed, and the reflux ratio is 30.

8. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the pressure for separating cyclopentene by ordinary rectification was 2atm, the theoretical plate number was 50, the extractant recovered in step S8 was fed from the 4 th plate, the C5 component was fed from the 26 th plate, the reflux ratio was 3.2, and the solvent ratio was 9.

9. The method for separating the environment-friendly cracked C5 fraction as claimed in claim 1, wherein: the pressure for ordinary rectifying separation of pentadiene is 2atm, the theoretical plate number is 10, the 5 th plate is fed, and the reflux ratio is 1.

Technical Field

The invention relates to the technical field of separation, in particular to a separation method of an environment-friendly cracking C5 fraction.

Background

The C5 fraction is a byproduct fraction containing 5 carbon atoms generated in the process of producing ethylene by petroleum cracking, and is an important chemical raw material with potential application value. The C5 fraction contains more than twenty components with close boiling points, wherein the utilization value is high and the content of 3 kinds of dienes such as Isoprene (IP), Cyclopentadiene (CPD) and Piperylene (PD) is more than 50% of the C5 fraction. The yield, composition and diolefin content of the cracked C5 fraction depend primarily on the composition of the cracked feedstock, with the lighter the cracked feedstock, the lower the C5 yield. The emphasis on the utilization of the C5 fraction is also mainly focused on the 3 dienes thereof. Isoprene is mainly used for synthesizing thermoplastic elastomers such as polyisoprene rubber and SIS. Currently, fine chemical products with high added value, which are made of isoprene as a raw material, are being developed, such as perfumes, synthetic rubbers, cosmetics, pharmaceuticals, insecticides, vitamins, and the like. Cyclopentadiene is mainly used for synthesizing C5 aliphatic petroleum resin, unsaturated polyester resin, ethylene propylene rubber second monomer, polydicyclopentadiene resin and the like, and the developed fine chemical products are medicinal products, flame retardants, optical materials and the like. Piperylene is mainly used in the production of C5 aliphatic petroleum resins and epoxy curing agents, and is being developed for use in butyl-pentyl rubber and latex. In addition, from the intermediate products, road marking paint, hot melt adhesive, printing ink, synthetic coating, adhesive, rubber compounding agent, waterproof treating agent, textile sizing agent, engineering plastic modifier, production solvent oil, gasoline blending component for vehicles and the like can be prepared. The C5 fraction has complex composition, the boiling points of the components are close, the relative volatility is small, azeotropes are easy to form among the components, and the diolefin is easy to polymerize, so that the separation of the diolefin product with high purity is difficult.

At present, a method combining thermal dimerization with azeotropic distillation or solvent extraction distillation is widely used in industry, namely, cyclopentadiene is dimerized into dicyclopentadiene (DCPD) by utilizing the characteristic that cyclopentadiene is easily dimerized compared with other C5 fractions, and dicyclopentadiene is separated from the C5 fraction by distillation by utilizing the characteristic that dicyclopentadiene has a boiling point significantly higher than that of other C5 hydrocarbons. While dicyclopentadiene can be conveniently depolymerized to yield cyclopentadiene. The C5 fraction without cyclopentadiene is separated by an azeotropic distillation method or a solvent extraction distillation method to obtain polymer-grade isoprene, and a crude product of piperylene can be obtained at the same time, but the loss of C5 fraction liquid is overlarge in the process, the investment cost and the operation cost are obviously higher, and the requirement on a regenerated solvent is higher.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an environment-friendly separation method for cracking C5 fraction, which has the advantages of high purity of recovered product, low requirement on operation process, low cost and no generation of toxic substances.

The purpose of the invention is realized by the following technical scheme:

an environment-friendly separation method of cracking C5 fraction comprises the following steps:

s1: adding a mixture of an extracting agent N-methyl pyrrolidone and water to the bottom of each rectifying tower and the tower kettle 1/2, and adding mixed carbon five fractions to the tower kettle 2/3;

s2: heating the tower kettle, respectively maintaining the temperature and the voltage of each section of the rectifying tower from bottom to top, and introducing condensed water;

s3: after each tower has reflux, the full reflux operation is kept;

s4: starting each feeding and discharging pump, continuously conveying materials into the tower, and keeping full reflux operation;

s5: when the conditions in the tower are stable, the tower top is refluxed;

s6: keeping each tower operating stably, recording temperature, sampling and measuring the discharge composition of each tower;

s7: stopping heating after the temperature of the whole tower and the composition of discharged materials are stable, discharging materials in each tower kettle when the materials are cooled to room temperature, stopping condensing water, and turning off power to obtain heavy components of the C5 distillate liquid with light components removed;

s8: and carrying out common rectification and extraction agent recovery on the heavy components of the obtained C5 distillate liquid without the light components to obtain isoprene, piperylene and cyclopentene.

In the first step of the invention, light components such as n-pentane, isopentane, 1-pentene, 3-methyl-1-butene, 2-methyl-2-butene and the like are separated by extractive distillation, and the light components subjected to fractionation have less olefin and can be used as fuel without further treatment, so that the cost is saved; secondly, common rectification is adopted to separate heavy components such as trans-1, 3-pentadiene, cis-1, 3-pentadiene, cyclopentene and C6, so as to obtain isoprene, piperylene and cyclopentene with high purity and high recovery rate, and the isoprene, piperylene and cyclopentene are put into further industrial production; the invention relates to a separation method for obtaining C5 fraction, wherein the extractant used in the separation method is N-methyl pyrrolidone with 4% water content, which has low toxicity and good separability and dissolubility to C5 mixture, and simultaneously according to the influence factors of rectification: the solvent ratio, reflux ratio, feeding position, pressure, theoretical plate number of the recovery tower and feeding position are optimized to obtain the optimal separation condition, so that the recovery rate and purity of the recovered isoprene, piperylene and cyclopentene are high, and the extractant is recycled in the recovery process, has small toxic and side effects and is environment-friendly.

The weight of water in the extractant in the step S1 is preferably 4% of the weight of the N-methylpyrrolidone, the extractant under the condition has a good extraction effect, the using amount of the extractant is small, and the cost is saved.

The total reflux time in the step S3 is 20 min; when pentane and pentene are separated by ordinary rectification, the pressure is 2atm, the theoretical plate number is 50, an extracting agent is fed from the 4 th plate, C5 is fed from the 33 th plate, the reflux ratio is 1.8, and the solvent ratio is 6; in the step S8, the pressure of the recovered extractant is 2atm, the theoretical plate number is 10, the 5 th plate is fed, and the reflux ratio is 1; when isoprene is separated by ordinary rectification, the pressure is 2atm, the theoretical plate number is 90, the 45 th plate is fed, and the reflux ratio is 30; when the piperylene and the cyclopentene are separated by common rectification, the pressure is 2atm, the theoretical plate number is 70, the 40 th plate is fed, and the reflux ratio is 30; the pressure is 2atm when cyclopentene is separated by ordinary rectification, the theoretical plate number is 50, the extractant recovered in the step S8 is fed by the 4 th plate, the C5 component is fed by the 26 th plate, the reflux ratio is 3.2, and the solvent ratio is 9; when the ordinary rectification separation of the piperylene is carried out, the pressure is 2atm, the theoretical plate number is 10, the 5 th plate is fed, the reflux ratio is 1, and the rectification effect can be influenced by the solvent ratio, the reflux ratio, the feeding position, the pressure, the theoretical plate number of the recovery tower and the feeding position, so that the recovery rate and the purity of the separated isoprene, piperylene and cyclopentene are highest.

The invention has the following advantages: the isoprene, the piperylene and the cyclopentene which are separated and recovered by the method have high recovery rate and high purity; the operation condition is simple, the requirement is low, the consumption of the extracting agent is low, the extraction effect is good, and the cost is reduced; the loss of C5 distillate is low.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

Examples

An environment-friendly separation method of cracking C5 fraction comprises the following steps:

s1: adding an extracting agent (N-methyl pyrrolidone with the water content of 4%) to 1/2 of the bottom of each rectifying tower, and adding mixed carbon five fractions to 2/3 of the tower;

s2: heating the tower kettle, respectively maintaining the temperature and the voltage of each section of the rectifying tower from bottom to top, and introducing condensed water;

s3: after each tower has reflux, the full reflux operation is kept;

s4: starting each feeding and discharging pump, continuously conveying materials into the tower, and keeping full reflux operation for 20 min;

s5: when the conditions in the tower are stable, the tower top is refluxed;

s6: keeping each tower operating stably, recording temperature, sampling and measuring the discharge composition of each tower;

s7: stopping heating after the temperature of the whole tower and the composition of discharged materials are stable, discharging materials in each tower kettle when the materials are cooled to room temperature, stopping condensing water, and turning off power to obtain heavy components of the C5 distillate liquid with light components removed;

s81: carrying out common rectification and extraction agent recovery on the heavy component of the obtained C5 fraction liquid without the light component under the conditions that the pressure is 2atm, the number of theoretical plates is 50, the extraction agent is fed from the 4 th plate, the C5 is fed from the 33 th plate, the reflux ratio is 1.8, the solvent ratio is 6, carrying out common rectification separation to obtain pentane and pentene, and carrying out extraction agent recovery on the residual component;

s82: recovering the extractant for later use under the conditions that the pressure is 2atm, the number of theoretical plates is 10, the 5 th plate is fed, and the reflux ratio is 1, and continuously rectifying the residual components after the extractant is recovered;

s83: under the conditions that the pressure is 2atm, the theoretical plate number is 90, the 4 th plate is fed, and the reflux ratio is 30, isoprene with the purity of 99.8 percent is obtained by common rectification separation;

s84: under the conditions of pressure of 2atm, theoretical plate number of 70, 40 th plate feeding and reflux ratio of 30, the mixture of piperylene and cyclopentene is separated by ordinary rectification;

s85: adding the recovered extractant into a mixture of piperylene and cyclopentene, feeding the extractant from the 4 th plate and the C5 component from the 26 th plate under the pressure of 2atm and the theoretical plate number of 50, feeding the extractant from the S8, feeding the C5 component from the 26 th plate, performing common rectification separation under the conditions of reflux ratio of 3.2 and solvent ratio of 9 to obtain cyclopentene with the purity of 99.5%, and continuing rectification of the rest components;

s86: under the conditions of pressure of 2atm, theoretical plate number of 10, 5 th plate feeding and reflux ratio of 1, the piperylene with purity of 99.7% can be obtained by ordinary rectification separation.

The invention firstly adopts extractive distillation to separate light components such as n-pentane, isopentane, 1-pentene, 3-methyl-1-butene, 2-methyl-2-butene and the like, heavy components such as trans-1, 3-pentadiene, cis-1, 3-pentadiene, cyclopentene, C6 and the like are left in C5 distillation liquid, no azeotrope is formed, common distillation is directly adopted for separation, the requirements on a device are reduced, the cost is saved, isoprene, cyclopentene and m-pentadiene with higher purity are obtained, and the specific purity is shown in Table 1.

Table 1: purity of separated product isoprene, cyclopentene and piperylene

Item	Isoprene (I)	Cyclopentene	Piperylene of piperylene
				GPI method	99.5％	94％	70％
The invention	99.8％	99.5％	99.7％

The separation method of C5 distillation liquid related by the invention recovers the obtained isoprene, piperylene and cyclopentene under the conditions of optimal solvent ratio, reflux ratio, feeding position, pressure, theoretical plate number of the recovery tower and feeding position, and the product isoprene, piperylene and cyclopentene have high purity; the operation condition is simple, the requirement is low, and the heat load of a condenser and a reboiler in the whole rectification process is low; the extractant is low in consumption, can be recycled, has a good extraction effect and reduces the cost; the loss of C5 distillation liquid is low, and the recovery rate is high.