CN103360201B - The method of recycling vinyl benzene with abstraction distillation from hydrocarbon mixture - Google Patents

Abstract

A method for extracting and rectifying recovery of styrene from hydrocarbon mixtures, comprising extracting and rectifying the hydrocarbon mixtures in the presence of a polymerization inhibitor with a compound solvent to recover styrene, wherein the compound solvent includes 80 to 99 mass % main solvent, 0.01-19 mass % co-solvent and 0.1-2.0 mass % water, wherein the main solvent is selected from sulfone compounds, and the co-solvent is methoxy phenol or methoxy phenol and glycol monomethyl ether mixture, the polymerization inhibitor includes 40-80% by mass of nitroxide free radicals, 15-50% by mass of nitrophenol and its derivatives, and 5-30% by mass of N,N-diethylhydroxylamine, the polymerization inhibitor The dosage of the agent is 10-500 μg/g of the amount of hydrocarbon raw material. The composite solvent selected in the present invention cooperates with a high-efficiency polymerization inhibitor, which can reduce the amount of the polymerization inhibitor and significantly reduce the polymerization rate of styrene.

Description

Method for recovering styrene by extractive distillation from hydrocarbon mixture

technical field

The invention relates to a method for extracting and rectifying recovery of styrene from hydrocarbon mixtures, specifically, a method for extracting and rectifying recovery of styrene from hydrocarbon mixtures using a complex solvent.

Background technique

Styrene monomer is an important basic organic chemical raw material, and it is also widely used in coatings, pesticides, and medicine. According to statistics, the steam pyrolysis gasoline by-product of the ethylene cracking unit contains 3-5% styrene. Due to the difference in raw materials for a set of 1 million tons/year ethylene unit, the content of styrene in the pyrolysis gasoline is 20,000-30,000 tons/year . In the existing process for dealing with pyrolysis gasoline, this part of styrene is hydrogenated into ethylbenzene, which is stored in the _C8 fraction, and this _C8 fraction rich in ethylbenzene is not very good for supplying the downstream p-xylene unit as a raw material ideal. If ultra-rectification is used to separate ethylbenzene and then dehydrogenate it into styrene, the process will be long, the energy consumption will be high, and it is unreasonable.

In contrast, the direct separation of styrene from pyrolysis gasoline is an attractive technology. However, the composition of the C ₈ fraction of pyrolysis gasoline is very complex, and the boiling points of the components are very close. Among them, the most difficult components to separate from styrene are o-xylene and phenylacetylene. The difference between the boiling points of o-xylene and styrene is only 0.8°C, and the relative volatility between the two is only 1.04. It requires thousands of theoretical plates for ordinary rectification, so it is actually impossible to achieve.

The feasible way to separate styrene from unhydrogenated pyrolysis gasoline is to use extractive distillation. There are two key technical points in the extractive distillation process. One is the solvent. The properties of the solvent include selectivity, boiling point, thermochemical stability, and the polymerization inhibition performance of the solvent to styrene, etc., which have a vital impact on the technical and economic indicators of the process. The second is how to effectively inhibit the polymerization of styrene, which is related to whether the device can run stably for a long period of time. In order to inhibit the polymerization of styrene, the key is to screen high-efficiency polymerization inhibitors. In addition, the solvent regeneration process for removing high boiling point substances must also be solved.

GB1,038,606 proposes a method for separating styrene from hydrocarbon mixtures. The method uses fuller's earth to treat hydrocarbon raw materials, and then uses an aqueous solution of silver salt as a solvent for extraction and rectification. The silver salt is Silver nitrate, but the cost of the solvent is higher, and the industrial practical value is lower.

USP3,763,015 discloses a method for separating styrene from pyrolysis gasoline using polymerization inhibitors and extractive distillation. The method carries out extractive distillation to pyrolysis gasoline in the presence of polar solvents and nitrogen-containing polymerization inhibitors. Then recover styrene from the solvent, react the recovered styrene with a sufficient amount of nitric acid to remove impurities in styrene, and obtain substantially colorless and pure styrene from the newly distilled styrene fraction after removing impurities. The polar solvent is selected from dimethylacetamide, dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide, etc., and the polymerization inhibitor used is sulfur, hydroquinone, p-tert-butylphthalene phenol. But preferred dimethylacetamide solvent is because boiling point (165 ℃) is on the low side, and toluene and styrene boiling point difference are too little, so process energy consumption is high.

USP4,596,655 discloses a method for separating styrene-based unsaturated hydrocarbons from hydrocarbon mixtures, using aminoethylpiperazine as a solvent for extractive distillation and a polymerization inhibitor, and 115 ~125 theoretical boards.

The method disclosed by CN1077560C for extracting and rectifying separation of styrene from pyrolysis gasoline proposes that the solvent for extracting and rectifying is divided into two parts, and the solvent is mainly selected from propylene carbonate, sulfolane, methyl carbitol, 1-methyl-2- Pyrrolidone, 2-pyrrolidone or their mixtures but not including the first part of water and the second part composed of water, the first part of solvent enters from the upper part of the extractive distillation column, and the second part of solvent is added from the bottom of the extractive distillation column.

_CN1962013A discloses a solvent for extracting and rectifying recovery of styrene from steam cracking C8 cuts, including 15-60% sulfone compounds and 40-45% nitrogen-containing compounds, and the sulfone compounds are selected from dimethyl methylene Sulfone or sulfolane, the nitrogen-containing compound is selected from succinonitrile, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 2-pyrrolidone, aminoethylpiperazine or N-formylmorpholine at least one. The solvent can make the pH value of the solvent about 7, and improve the relative volatility of o-xylene to styrene.

CN1962582A discloses a method for anti-styrene polymerization, adding a water-containing solvent-dissolved polymerization inhibitor greater than 50 ppm to the styrene aqueous system with a concentration of 5 to 99% by weight to prevent the polymerization of styrene, wherein the polymerization inhibitor The weight percent composition is as follows: a) 20%-80% of nitrite; b) 10%-50% of quinone compound; c) 1%-35% of nitrophenol, polynitrophenol or derivatives thereof.

CN101468938A discloses a composite solvent for extracting and rectifying separation of styrene, including 62-90% by mass of a main solvent and 10-38% by mass of a co-solvent, and the main solvent is selected from sulfone compounds, pyrrolidone compounds, glycols Compounds or a mixture of any two or three of them, the co-solvent is selected from C ₉ -C ₁₂ aromatic hydrocarbons, amides with 2-6 carbon atoms or their mixtures.

CN101955409A discloses a method for inhibiting the polymerization of vinyl aromatic compounds in the extractive distillation process, the inhibitor is 2-sec-butyl-4,6-dinitrophenol (DNBP), and the addition amount is at least vinyl 10,000 wtppm of the amount of aromatic compounds.

Cheng Wenwu disclosed that 4-hydroxyl-2,2,6,6-tetramethyl Composite polymerization inhibitor composed of piperidine nitroxide free radical (OH-TEMPO), hydroxylamine and DNBP, the induction period of the polymerization inhibitor is prolonged, and the slow polymerization effect after the induction period is over is also improved.

In the prior art, the solvent cannot take into account the contradiction between the selectivity of the key component o-xylene/styrene separation, the solubility of the polymer, and its own polymerization inhibition performance. Although sulfolane has good selectivity , but the solubility of polymers is low. Once polymers are produced during the process, they are easy to precipitate and block the equipment. The existing polymerization inhibitors have very high boiling points, and either their solubility is too low to easily precipitate, or they are used in large amounts and have poor polymerization inhibition effects, which affect the long-term stable operation of the entire device.

Contents of the invention

The purpose of the present invention is to provide a method for extracting and rectifying recovery of styrene from hydrocarbon mixtures. The composite solvent selected in this method cooperates with a multi-component polymerization inhibitor, which can reduce the amount of polymerization inhibitor and significantly reduce the polymerization of styrene. Rate.

The method for extracting and rectifying recovery of styrene from hydrocarbon mixtures provided by the present invention comprises carrying out extraction and rectification of hydrocarbon mixtures in the presence of a polymerization inhibitor with a compound solvent to recover styrene, wherein the compound solvent includes 80- 99% by mass of main solvent, 0.01-19% by mass of co-solvent and 0.1-2.0% by mass of water, wherein the main solvent is selected from sulfone compounds, and the co-solvent is methoxyphenol or methoxyphenol and glycol monomethyl A mixture of ethers, the polymerization inhibitor includes 30-80% by mass of nitroxide free radicals, 15-50% by mass of nitrophenol and its derivatives and 5-35% by mass of N,N-diethylhydroxylamine.

In the present invention, a co-solvent with a moderate boiling point, a good polymerization inhibition effect, and a large dissolving ability for polymers is added to the main solvent for extracting and rectifying styrene, and used in conjunction with a multi-component polymerization inhibitor, which can effectively reduce the concentration of the extraction essence. The temperature at the bottom of the distillation tower and the bottom of the solvent recovery tower can greatly reduce the amount of polymerization inhibitor, greatly reduce the polymerization of styrene, avoid polymer precipitation, and effectively prolong the stable operation period of the extraction and rectification recovery styrene unit.

Description of drawings

Fig. 1 is the schematic flow _sheet of extracting and rectifying recovery of styrene from pyrolysis gasoline C8 fraction with the inventive method.

detailed description

In the present invention, in the main solvent for extracting and rectifying styrene, methoxyphenol, which has a relatively large dissolving power for polymers and has polymerization-inhibiting properties, is added as a cosolvent. In addition, the cosolvent can also be methoxyphenol and methoxyphenol. Glycol monomethyl ether mixture. In the method of the present invention, the composite solvent comprising the co-solvent and the multi-component polymerization inhibitor are used together, which can reduce the amount of the polymerization inhibitor, reduce the temperature at the bottom of the extraction and rectification tower and the bottom of the solvent recovery tower, and prolong the life of the extraction and rectification device. stable running time.

The composite solvent of the present invention preferably includes 86-99 mass % of main solvent, 0.1-13.0 mass % of co-solvent and 0.1-1.0 mass % of water.

The main solvent in the composite solvent is selected from sulfone compounds, preferably one or more of sulfolane, dimethylsulfone and 3-methylsulfolane, more preferably sulfolane.

The co-solvent in the composite solvent is methoxyphenol, and in order to further increase the solubility of the styrene polymer, it may also be a mixture of methoxyphenol and glycol monomethyl ether. Described methoxyphenol is 4-methoxyphenol, 3-methoxyphenol or 2-methoxyphenol, and described ethylene glycol monomethyl ether is diethylene glycol monomethyl ether, triethylene glycol monomethyl ether ether, tetraethylene glycol monomethyl ether or their mixtures. If the auxiliary solvent is a mixture of methoxyphenol and ethylene glycol monomethyl ether, the mass ratio of ethylene glycol monomethyl ether to methoxyphenol is 5-1:1, preferably 3-1:1.

The polymerization inhibitor used in the method of the present invention contains multiple components, and the polymerization inhibitor preferably includes 30-65 mass % of nitroxide free radicals, 15-40 mass % of nitrophenol and its derivatives and 15-35 mass % % N,N-diethylhydroxylamine.

Nitroxide free radicals in the polymerization inhibitor used in the method of the present invention also include compounds containing oxygen nitrogen free radicals, selected from 4-hydroxyl-2,2,6,6-tetramethylpiperidine nitroxide free radicals, phosphorous acid tris (2,2,6,6-tetramethylpiperidine nitroxide) ester or a mixture thereof.

The nitrophenol and its derivatives are preferably 2,6-dinitro-p-cresol, 2-sec-butyl-4,6-dinitrophenol or 2,4-dinitrophenol.

The mass ratio of the total amount of the polymerization inhibitor to the hydrocarbon mixture, that is, the raw material for extraction and rectification, is 10-500 μg/g, preferably 30-300 μg/g.

When using the method of the present invention to reclaim styrene by extractive distillation, the hydrocarbon mixture is introduced from the middle of the extractive distillation tower, the composite solvent is introduced from the top of the extractive distillation tower, the polymerization inhibitor is fed from the extractive distillation tower, and the extractive distillation tower The bottom or the top of the solvent recovery tower is introduced. After extractive distillation, the raffinate is discharged from the top of the extractive distillation tower. The rich solvent rich in styrene is discharged from the bottom of the extractive distillation tower and enters the solvent recovery tower. The styrene is discharged from the solvent The recovery tower is discharged from the top, and the composite solvent is discharged from the bottom of the solvent recovery tower, preferably returned to the extractive distillation tower for recycling.

The number of theoretical plates of the extractive distillation tower is preferably 60 to 90, the mass ratio of the composite solvent to the hydrocarbon mixture is 3 to 6, the top reflux ratio is 1 to 3, and the temperature at the bottom of the tower is 120 to 135°C. The top pressure is 8-20kPa.

The number of theoretical plates of the solvent recovery tower is preferably 20-40, the reflux ratio at the top of the tower is 0.5-2.5, the temperature at the bottom of the tower is 130-145° C., and the pressure at the top of the tower is 8-20 kPa.

The hydrocarbon mixture of the present invention is preferably the C8 fraction of pyrolysis gasoline, wherein the styrene content is ₂₅ to 70 mass%, the C8 aromatics and non-aromatics content is ₂₈ to 70 mass%, and the other carbon number aromatics content is 0.01 to 70 mass%. 5.0% by mass.

The present invention will be described in detail below in conjunction with the accompanying drawings.

In Fig. 1, the hydrocarbon mixture containing styrene enters from the pipeline 1, and enters the extractive distillation column 102 from the middle part through the pipeline 2 after heat exchanger 101 heat exchange, and the composite solvent enters the extractive distillation column 102 from the top through the pipeline 15, The polymerization inhibitor is injected into line 1 by a metering pump. After extraction and rectification, the styrene-free components are discharged from the top line 3 of the extractive distillation tower and enter the reflux tank 103, and part of the raffinate flowing out of the reflux tank flows back into the top of the extractive distillation tower 102 through the pipeline 4 , the other part is discharged from the pipeline 5, and the moisture is discharged from the pipeline 6. The rich solvent rich in styrene is discharged from the bottom of the extractive distillation tower, enters the solvent recovery tower 104 from the middle through the pipeline 7, styrene and water are discharged from the tower top pipeline 8, enters the reflux tank 105, and the styrene discharged from the reflux tank 105 A part flows back into the solvent recovery tower through the pipeline 9, and the other part is discharged from the pipeline 10 as a product, and the poor compound solvent not containing styrene is discharged from the bottom pipeline 13 of the solvent recovery tower, enters the pipeline 14 after heat exchange by the heat exchanger 106, and then passes through the Heat exchanger 101 enters line 15 . After the water discharged from the pipeline 11 is combined with the water discharged from the pipeline 6, after exchanging heat with the composite solvent from the bottom of the solvent recovery tower 104 in the heat exchanger 106, the water is vaporized and enters the bottom of the solvent recovery tower 104 through the pipeline 12 as stripping medium.

The following examples further illustrate the present invention in detail, but the present invention is not limited thereto.

Example 1

_The C8 fraction of pyrolysis gasoline is used as the raw material, and its composition is listed in Table 1. According to the flow process shown in Figure 1, the raw material is extracted and rectified, and the styrene in it is reclaimed. The composite solvent used contains 99% by mass of the main solvent sulfolane, 0.5% by mass of co-solvent 4-methoxyphenol and 0.5% by mass % water. The polymerization inhibitor is 4-hydroxyl-2,2,6,6-tetramethylpiperidine nitroxide free radical (OH-TEMPO) of 55 mass %, 4,6-dinitro-2-secondary of 25 mass % Butylphenol (DNBP) and 20% by mass of N,N-diethylhydroxylamine. The mass ratio of the total amount of polymerization inhibitor to the raw material for extraction is 100 μg/g.

The number of theoretical plates of the extractive distillation column is 70, the top pressure of the column is 15kPa, the mass ratio of composite solvent/raw material is 3.8, and the reflux ratio is 2.0.

The number of theoretical plates of the solvent recovery tower is 28, the top pressure of the tower is 15kPa, and the reflux ratio is 1.0.

Table 2 shows the extraction and rectification results under the condition that the styrene purity is 99.7% by mass and the recovery rate is 95% by mass.

Example 2

According to the method of example ₁ , reclaim styrene from pyrolysis gasoline C cut, difference is that the cosolvent of use is 3-methoxyphenol, under the condition that styrene purity is 99.7 mass %, recovery rate is 95 mass %, The extractive distillation results are shown in Table 2.

Example 3

According to the method of example ₁ , reclaim styrene from pyrolysis gasoline C cut, difference is that the cosolvent of use is 2-methoxyphenol, under the condition that styrene purity is 99.7 mass %, recovery rate is 95 mass %, The extractive distillation results are shown in Table 2.

Example 4

Reclaim styrene from pyrolysis gasoline C cut by the method for example ₁ , difference is that used composite solvent contains the main solvent sulfolane of 88 mass %, the 2-methoxyphenol of 5 mass %, the triethylene glycol of 6.5 mass % Monomethyl ether and 0.5% by mass of water, the mass ratio of the total amount of polymerization inhibitor to the raw material for extraction is 150 μg/g. Table 2 shows the extraction and rectification results under the condition that the styrene purity is 99.7% by mass and the recovery rate is 95% by mass.

Example 5

Reclaim styrene from pyrolysis gasoline C cut by the method for example ₁ , difference is that the polymerization inhibitor used is three (2,2,6,6-tetramethylpiperidine nitroxide free radicals of phosphorous acid) of 40 mass % ) ester, 30 mass % of 2,6-dinitro-p-cresol (DNPC) and 30 mass % of N, N-diethylhydroxylamine, the mass ratio of the inhibitor total amount to the extraction raw material is 150 μg/g, Table 2 shows the extraction and rectification results under the condition that the styrene purity is 99.7% by mass and the recovery rate is 95% by mass.

Comparative example 1

According to the method of example ₁ , reclaim styrene from pyrolysis gasoline C cut, the difference is that the composite solvent used is sulfolane of 99.5 mass % and the water of 0.5 mass %, and the polymerization inhibitor is prepared by the method of CN1962582A, and the polymerization inhibitor contains 65 The sodium nitrite of mass %, the benzoquinone of 20 mass % and the DNBP of 15 mass %, the mass ratio of polymerization inhibitor total amount and extraction raw material is 600 μ g/g, in styrene purity is 99.7 mass %, recovery rate is 95 mass % %, the extractive distillation results are shown in Table 2.

Comparative example 2

Reclaim styrene from pyrolysis gasoline C cut by the method for example ₁ , difference is that the composite solvent that uses is the water of sulfolane of 99.5 mass % and 0.5 mass %, and the polymerization inhibitor consumption is 200 μ g/g. Table 2 shows the extraction and rectification results under the condition that the styrene purity is 99.7% by mass and the recovery rate is 95% by mass.

Table 1

Table 2

As can be seen from Table 2, under the conditions of identical styrene purity (99.7 mass %) and recovery rate (95 mass %), adopt composite solvent of the present invention, because it is good to the dissolubility of polymerization inhibitor, polymerization inhibitor consumption Compared with the comparative example, the polymerization rate of styrene is significantly reduced, and there is no polymerized suspended matter in the poor solvent. What is more prominent is that the continuous operation time to reach the specified purity and recovery rate is significantly longer than that of the comparative example.

Claims (8)

1. the method for a recycling vinyl benzene with abstraction distillation from hydrocarbon mixture, comprise and hydrocarbon mixture is carried out extracting rectifying recovery vinylbenzene wherein with double solvents under stopper exists, described double solvents comprises the main solvent of 80 ~ 99 quality %, the solubility promoter of 0.01 ~ 19 quality % and the water of 0.1 ~ 2.0 quality %, wherein main solvent is selected from sulfone compound, solubility promoter is the mixture of methoxyphenol or methoxyphenol and glycol monomethyl ether, described stopper comprises the nitroxyl free radical of 30 ~ 80 quality %, the N of the nitrophenol of 15 ~ 50 quality % and derivative and 5 ~ 35 quality %, N--diethyl hydroxylamine,

Described sulfone compound be selected from tetramethylene sulfone, dimethyl sulfone and 3-methyl sulfolane one or more;

Described methoxyphenol is 4-methoxyphenol, 3-methoxyphenol or 2-methoxyphenol, and described glycol monomethyl ether is diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, Tetraglycol 99 monomethyl ether or their mixture;

Described nitroxyl free radical is 4-hydroxyl-TEMPO, tricresyl phosphite (TEMPO) ester or its mixture;

Described nitrophenol and derivative thereof are selected from 2,6-dinitro-p-cresol, 2-sec-butyl-4,6-dinitrophenol or 2,4-DNP.

2. in accordance with the method for claim 1, it is characterized in that described double solvents comprises the water of the main solvent of 86 ~ 99 quality %, the solubility promoter of 0.1 ~ 13.0 quality % and 0.1 ~ 1.0 quality %.

3., in accordance with the method for claim 1, when it is characterized in that solubility promoter is the mixture of methoxyphenol and glycol monomethyl ether, the mass ratio of glycol monomethyl ether and methoxyphenol is 5 ~ 1: 1.

4. in accordance with the method for claim 1, it is characterized in that described stopper comprises the N of the nitroxyl free radical of 30 ~ 65 quality %, the nitrophenol of 15 ~ 40 quality % and derivative and 15 ~ 35 quality %, N-diethyl hydroxylamine.

5. in accordance with the method for claim 1, it is characterized in that the total amount of described stopper and the mass ratio of hydrocarbon mixture are 10 ~ 500 μ g/g.

6. in accordance with the method for claim 1, when it is characterized in that recycling vinyl benzene with abstraction distillation, the middle part of hydrocarbon mixture from extractive distillation column is introduced, double solvents is introduced from extracting rectifying tower top, stopper at the bottom of extractive distillation column charging, extractive distillation column or solvent recuperation tower top introduce, after extracting rectifying, raffinate is discharged from the top of extractive distillation column, the rich solvent of rich in styrene is discharged at the bottom of extractive distillation column, enter solvent recovery tower, vinylbenzene is discharged from solvent recuperation tower top, and double solvents is discharged at the bottom of solvent recovery tower.

7. in accordance with the method for claim 6, it is characterized in that the theoretical plate number of described extractive distillation column is 60 ~ 90, the mass ratio of double solvents and hydrocarbon mixture is 3 ~ 6, and trim the top of column ratio is 1 ~ 3, column bottom temperature is 120 ~ 135 DEG C, and tower top pressure is 8 ~ 20kPa.

8. in accordance with the method for claim 6, it is characterized in that the theoretical plate number of described solvent recovery tower is 20 ~ 40, the reflux ratio of tower top is 0.5 ~ 2.5, and column bottom temperature is 130 ~ 145 DEG C, and tower top pressure is 8 ~ 20kPa.