JP6065138B1 - Method for reducing corrosive ions in aromatic compound extraction solvents - Google Patents

Abstract

An object of the present invention is to reduce corrosive ions in an aromatic compound extraction solvent simply and efficiently in order to suppress the corrosion of an extraction apparatus caused by the corrosive ions contained in an aromatic compound extraction solvent in a circulation system. A method for reducing corrosive ions in an aromatic compound extraction solvent is provided. A method for reducing corrosive ions in an aromatic compound extraction solvent in a circulation system in which an aromatic compound extraction solvent circulates, wherein the corrosive ions are chloride ions, sulfate ions, and sulfite ions. A step of adding a corrosive ion scavenger, reacting the corrosive ions with the corrosive ion scavenger to form a non-volatile salt, and the salt containing the salt A method for reducing corrosive ions in an aromatic compound extraction solvent, comprising a step of removing the salt by concentrating the solvent. [Selection figure] None

Description

  The present invention is an aromatic compound extraction capable of preventing corrosion in a system in which a solvent for extracting an aromatic compound such as benzene, toluene and xylene from a hydrocarbon fluid circulates in a petroleum refinery or a coal chemical factory. The present invention relates to a method for reducing corrosive ions such as chloride ions, sulfate ions and sulfite ions in a solvent.

In oil refining and refining hydrocarbons at coal chemical factories, there has been a problem that corrosive ions such as chloride ions, sulfate ions, sulfite ions, etc. derived from various salts mixed in raw materials have caused corrosion of equipment. was there.
For this, a technique of adding an alkali to capture corrosive ions is known. However, the salt generated by the addition of alkali has a risk of causing serious troubles such as adhesion and deposition, adhesion deposition and clogging in the apparatus.

  Patent Document 1 describes a method for preventing corrosion caused by chlorides in a condensation system in an oil production process by mixing and using a plurality of amines such as monoethanolamine. Further, in Patent Document 2, a quaternary ammonium compound such as choline hydroxide (2-hydroxyethyltrimethylammonium hydroxide) is present in a fluid that can come into contact with the inside of an oil refinery or the like to generate hydrogen chloride. Preventing and performing metal corrosion protection is described.

Japanese Patent Laid-Open No. 7-180073 JP 2004-2111195 A

  However, in the conventional method, although chloride ions derived from salts contained in petroleum or the like are reduced, it has been difficult to completely remove them. Therefore, hydrocarbons such as naphtha obtained by refining petroleum are often mixed with chloride, chloride ions, sulfate ions, sulfite ions, and a system using this hydrocarbon mixture as a raw material. However, the problem of corrosion by corrosive ions still existed.

  On the other hand, a catalyst is used in a method of reforming a hydrocarbon mixture such as naphtha to obtain an aromatic compound such as benzene, toluene, or xylene. The catalyst is used continuously or recovered from the composition of the reaction product and reused. However, since the catalyst activity decreases with long-term use, the catalyst is regenerated. Chlorine compounds are often used for catalyst regeneration, and the hydrocarbon reformate supplied from the aromatic compound production equipment to the extraction equipment can only contain chloride ions mixed in the hydrocarbon mixture as the raw material. In addition, chloride ions derived from the chlorine compound used for the regeneration of the catalyst may also be mixed.

Further, the aromatic hydrocarbon oil or the like that is a hydrocarbon reformed product is subjected to an aromatic compound extraction process using an extraction solvent. In this extraction process, an aromatic hydrocarbon oil is dissolved in an extraction solvent, and an aromatic compound is extracted and separated by distillation. And a new raw material aromatic hydrocarbon oil is added to the solvent after extraction, and it distills again. Thus, the extraction solvent is circulated and used in the extraction apparatus from the viewpoints of cost reduction and prevention of environmental pollution.
As a result, corrosive ions contained in the raw material aromatic hydrocarbon oil that is sequentially supplied accumulate in the extraction solvent that is circulated. Increasing the concentration of corrosive ions in the extraction solvent causes rapid corrosion of the extraction device, coupled with the presence of trace amounts of water in the extraction solvent. On the other hand, even if the acid that generates corrosive ions in the extraction solvent is neutralized by adding a known alkali, salt accumulates in the circulation system of the extraction solvent. Conventionally, there has been no technical idea of capturing corrosive ions by adding an alkali.

Thus, the increase in the concentration of corrosive ions in the extraction solvent is a problem peculiar to the extraction solvent in the circulation system, and a countermeasure with a higher corrosion inhibition effect is required than in the transient system.
In addition, if it is going to cope with a method as described in the said patent document 1 in a circulation system, it is necessary to prepare several amines so that it may become optimal for neutralization and precipitation, and also a circulation system by distillation. It will be easily discharged from the inside as a volatile component, and the corrosion inhibiting effect will be reduced. Depending on conditions, general alkanolamines and the like are easily discharged as volatile components from the circulation system by distillation and lack the ability to supplement corrosive ions.

  The present invention has been made under such circumstances, and in order to suppress corrosion of the extraction apparatus caused by corrosive ions contained in the aromatic compound extraction solvent in the circulation system, An object of the present invention is to provide a method for reducing corrosive ions in an aromatic compound extraction solvent, which can easily and efficiently reduce the corrosive ions.

  The present invention captures corrosive ions in an aromatic compound extraction solvent in a circulation system as a non-volatile salt and reduces the salt concentration in the system by concentrating the extraction solvent containing this salt in the facility. Further, it is based on the finding that corrosive ions in the circulating extraction solvent can be easily and efficiently reduced by discharging the concentrated salt.

That is, the present invention provides the following [1] to [11].
[1] A method for reducing corrosive ions in an aromatic compound extraction solvent in a circulation system in which an aromatic compound extraction solvent circulates, wherein the corrosive ions are chloride ions, sulfate ions, and sulfite ions. A step of adding a corrosive ion scavenger and reacting the corrosive ions with the corrosive ion scavenger to form a non-volatile salt, and the solvent containing the salt A method for reducing corrosive ions in an aromatic compound extraction solvent, which comprises a step of removing the salt by concentration.
[2] The aromatic compound extraction solvent is selected from sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol, N-methylpyrrolidone, dimethyl sulfoxide, morpholine, N-formylmorpholine, methyl carbamate, diglycolamine, furfural and phenol. The method for reducing corrosive ions in the aromatic compound extraction solvent according to the above [1], which is one or more selected from the group consisting of:
[3] The corrosive ion in the aromatic compound extraction solvent according to the above [1] or [2], wherein the corrosive ion scavenger is a quaternary ammonium compound represented by the following general formula (1): Reduction method.

(In the formula ^(1), R 1 ~R ³ are each independently a hydrocarbon group having 1 to 4 carbon atoms, n represents an integer of 1 to 10.)
[4] The aromatic compound extraction solvent according to any one of the above [1] to [3], wherein in the circulation system, any one or more selected from ammonia and neutralizing amines are used in combination. Corrosive ion reduction method.
[5] The method for reducing corrosive ions in the aromatic compound extraction solvent according to any one of the above [1] to [4], wherein the concentration is performed with a regenerator of the aromatic compound extraction solvent.
[6] Any of the above [1] to [5], wherein the corrosive ion scavenger is added based on the corrosive ion concentration in the circulating aromatic compound extraction solvent. The method for reducing corrosive ions in the aromatic compound extraction solvent according to item 1.
[7] Corrosion in the aromatic compound extraction solvent according to the above [6], wherein the corrosive ion scavenger is added so as to have a molar equivalent of 0.5 to 2 times the corrosive ion concentration. Negative ion reduction method.
[8] The corrosive ion scavenger is any one of the above [1] to [5], wherein the addition frequency and concentration are determined based on the metal ion concentration in the circulating aromatic compound extraction solvent. The method for reducing corrosive ions in the aromatic compound extraction solvent according to Item.
[9] The method for reducing corrosive ions in the aromatic compound extraction solvent according to [8], wherein the metal ions are iron ions.
[10] The aromatic compound extraction solvent according to any one of [1] to [9], wherein the aromatic compound is any one or more selected from benzene, toluene, and xylene. Corrosive ion reduction method.

[11] A method for extracting an aromatic compound using the method for reducing corrosive ions in the aromatic compound extraction solvent according to any one of [1] to [10].

ADVANTAGE OF THE INVENTION According to this invention, the corrosive ion in the aromatic compound extraction solvent of a circulation system can be reduced simply and efficiently.
Therefore, the corrosion of the extraction apparatus due to the corrosive ions contained in the aromatic compound extraction solvent in the circulatory system can be suppressed, and the aromatic compound can be extracted efficiently.

It is a system | strain schematic diagram of an example of an aromatic compound extraction apparatus.

The method for reducing corrosive ions in an aromatic compound extraction solvent of the present invention is a method applied to a circulation system in which an aromatic compound extraction solvent circulates, and chloride ions, sulfate ions and sulfite ions, that is, corrosive ions. Is reduced. The step includes adding a corrosive ion scavenger, reacting the corrosive ions with the corrosive ion scavenger to form a non-volatile salt, and concentrating the solvent containing the salt to Removing the salt.
In this way, the corrosive ions in the aromatic compound extraction solvent in the circulation system are converted into non-volatile salts, and the extraction solvent containing this is concentrated to cause corrosion in the solvent causing the extraction device to corrode. Ionic ions can be reduced easily and efficiently.

[Circulating system]
The method of the present invention is applied to a circulation system containing at least one of chloride ion, sulfate ion and sulfite ion, in which the aromatic compound extraction solvent is a corrosive ion. For example, in the refining of hydrocarbon oil such as petroleum, a system in which a solvent is circulated and used in the process of extracting an aromatic compound from the aromatic hydrocarbon oil can be used.
The aromatic hydrocarbon oil contains, for example, an aromatic compound obtained by reforming. Specifically, the aromatic compound contains benzene, toluene or xylene, and a mixture of any of these. To do.

[Aromatic compound extraction solvent]
As the aromatic compound extraction solvent, those commonly used in the purification of hydrocarbon oils can be used. For example, sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol, N-methylpyrrolidone, dimethyl sulfoxide, morpholine, N-formylmorpholine, methyl carbamate, diglycolamine, furfural, phenol and the like can be mentioned. These solvents may be used alone or in combination of two or more. Of these, sulfolane is preferably used. Sulfolane may be gradually decomposed by use or may contain sulfuric acid as an impurity, and may produce sulfate ion or sulfite ion. However, according to the method of the present invention, sulfolane-derived sulfate ion and sulfite ion are also present. There is no problem because it can be reduced.

[Corrosive ion scavenger]
The corrosive ion scavenger is a compound that can form a salt with corrosive ions, and one that does not volatilize in the circulation system to be added is used. Preferably, if it is strongly basic, the salt formed with the corrosive ions becomes a neutral salt, and the corrosion of the extraction apparatus can be further suppressed.
Examples of such corrosive ion scavengers include quaternary ammonium compounds represented by the following general formula (1). In addition, super strong base compounds such as 1,8-diazabicyclo [5.4.0] undecene-7 and inorganic strong alkalis such as sodium hydroxide are also included. The addition of the inorganic alkali is preferably a quaternary ammonium compound as described above from the viewpoint of an increase in the ash content in the circulating solvent and from the viewpoint of handleability.

In formula (1), R ^{1 to} R ³ are each independently a hydrocarbon group having 1 to 4 carbon atoms, and n is an integer of 1 to 10. Specific examples of R ^{1 to} R ³ include linear groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. Examples thereof include a branched alkyl group.
Specific examples of such quaternary ammonium compounds include hydroxymethyltrimethylammonium hydroxide, hydroxymethyltriethylammonium hydroxide, choline hydroxide, 2-hydroxyethyltriethylammonium hydroxide, 3-hydroxypropyltrimethylammonium hydroxide, and the like. Is mentioned. These may be used alone or in combination of two or more.

Preferably, R ^{1 to} R ³ are each independently a hydrocarbon group having 1 to 3 carbon atoms, and n is an integer of 1 to 4. When the quaternary ammonium compound has such a low molecular weight, it is excellent in solubility in water and exhibits a sufficient effect as a corrosive ion scavenger even in a low addition amount, which is an effect of the present invention. Corrosion suppression effect becomes higher. Among these, choline hydroxide (also known as choline) in which R ^{1 to} R ³ are all methyl groups and n is 2 is particularly preferable.

Such a quaternary ammonium compound is generally preferably used as an aqueous solution in terms of handling, and the concentration thereof is not particularly limited, but is preferably 5 to 50% by mass.
Since ammonia, other amines, and the like are weakly basic, the salt formed by these alkalis and corrosive ions is an acid salt, and even a trace amount causes corrosion when water is present. On the other hand, since the quaternary ammonium compound as described above is strongly basic, the salt formed with the corrosive ions is a neutral salt and hardly corrodes even in the presence of water.
In addition, the salt formed by the quaternary ammonium compound and corrosive ions has deliquescence and fluidity, so that it is difficult to stick, and there is no possibility of adhesion or clogging inside the circulation system.

  The salt formed by the corrosive ion scavenger and corrosive ions of the present invention has a high boiling point and is a non-volatile salt in the circulation system. For this reason, in the distillation purification process of aromatic hydrocarbon oil etc., the salt is hardly mixed in the aromatic compound extracted by evaporation, and separation from the extraction solvent can also be performed by concentration by distillation, It can be removed as a distillation residue.

The corrosive ion scavenger is preferably a quaternary ammonium compound as described above, and even by itself, it can exhibit a sufficient corrosive ion scavenging effect, but in order to further enhance the corrosive ion scavenging effect, As other chemicals, ammonia, neutralizing amine or the like may be used in combination.
Examples of the neutralizing amine include monoethanolamine, cyclohexylamine, morpholine, diethylethanolamine, monoisopropanolamine, 3-methoxypropylamine, 2-amino-2-methyl-1-propanol and the like.

If the corrosive ion scavenger addition amount can predict or measure the corrosive ion concentration in the extraction solvent in the circulation system, the addition frequency and concentration can be determined based on the corrosive ion concentration. . The corrosive ion concentration can be measured with an absorptiometer, ion chromatograph, capillary electrophoresis apparatus or the like.
From the viewpoint of the addition effect, the concentration of the corrosive ion scavenger is preferably added so as to be 0.5 to 2 times the molar equivalent of the corrosive ion concentration, and a more stable corrosive ion scavenging effect is obtained. From a viewpoint, it is more preferable that it is 1-2 times molar equivalent.

Further, as a means for indirectly detecting the corrosive ion concentration, the metal ion concentration in the extraction solvent in the circulation system may be measured. When corrosion of the extraction device proceeds with an increase in the corrosive ion concentration in the circulating extraction solvent, the metal ion concentration in the circulation system increases. For this reason, it is also possible to detect the increase in the corrosive ion concentration by the increase in the metal ion concentration. The metal ion concentration can be measured with an absorptiometer, an inductively coupled plasma emission spectrometer (ICP-AES), an inductively coupled plasma mass spectrometer (ICP-MS), or the like.
In this case, it is preferable to obtain a correlation between the metal ion concentration to be measured and the corrosive ion concentration in the circulation system in advance. Thereby, the addition frequency and density | concentration of a corrosive ion trapping agent can be determined based on the metal ion density | concentration of a circulation system.
Specifically, the metal ions to be measured are preferably iron ions that are easily eluted due to corrosion of the apparatus.

  When extracting aromatic compounds in the circulatory system, the method of the present invention as described above is used as a method for reducing the corrosive ions in the extraction solvent, resulting in corrosive ions contained in the circulatory extraction solvent. Therefore, it is possible to effectively suppress the corrosion of the extracting device, and thus it is possible to perform efficient extraction.

Hereinafter, an apparatus and a processing mechanism to which the method of the present invention is applied will be described with an example. FIG. 1 shows a system outline diagram of an example of an aromatic compound extraction apparatus to which the method of the present invention is applied.
In the system flow shown in FIG. 1, the raw aromatic hydrocarbon oil supplied continuously or intermittently from feed 1 is desalted by chlortritor 2 and then mixed with an aromatic compound extraction solvent in extraction tower 3. Then, aromatic compounds such as benzene, toluene and xylene are extracted. Components insoluble in the solvent are withdrawn from the top of the column, washed with the washing column 4 and then the raffinate 9 is separated.
On the other hand, the aromatic compound extracted in the extraction solvent is extracted from the bottom of the extraction tower 3 together with the extraction solvent. Then, it is separated into an aromatic compound and an extraction solvent by distillation in the stripper column 5 and the recovery column 6 to obtain an aromatic compound.

Here, the corrosive ion scavenger is added as an aqueous solution from the injection facility 10 provided at any position in the circulation system of the extraction solvent such as the top system of the stripper column 5.
The extraction solvent is regenerated by distillation again in the recovery column 6, dehydrated by the process water stripper 8, returned to the extraction tower 3, and recycled.
The recovered extraction solvent from the recovery column 6 contains a non-volatile salt generated by the reaction of the corrosive ion scavenger and the corrosive ions in the extraction solvent. The recovered extraction solvent containing such a salt is concentrated by distillation with a bypass regenerator 7. The concentrated residue is separated and removed, and the fraction is returned to the recovery column 6, whereby the regenerated solvent with reduced corrosive ions is provided to the circulation system.

Although the corrosive ion scavenger may be added at any position in the circulation system, for example, in the above apparatus, the injection provided in the tower top system of the stripper column 5 that is a stage after the aromatic compound extraction tower 3. It can be added from the facility 10.
The temperature of the extraction solvent circulation system including the regenerator 7 is 180 ° C. or less from the viewpoint of preventing the corrosive ion scavenger from volatilizing and promoting the corrosive ion scavenging effect of the regenerator 7. It is preferable.

  As described above, since the salt formed by the corrosive ion scavenger and the corrosive ion is a non-volatile salt in the circulation system, it is discharged to the extract side by distillation or the like for extraction of aromatic compounds. However, it can be separated as a distillation residue of solvent concentration at a specific location such as the regenerator 7 for solvent regeneration provided in the circulation system. Furthermore, the salt may be removed out of the circulation system by providing a means for discharging the residual residue containing the salt.

  Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following examples.

[Test 1] Laboratory level confirmation test (Test 1-1)
In a 500 mL round bottom flask, 100 mL of xylene, 96 mL of sulfolane, and 4 mL of pure water were added. To this, hydrochloric acid and an aqueous choline hydroxide (choline) solution were added, and a sample solution was prepared so that the chloride ion concentration was 100 mg / L and the choline concentration was 340 mg / L.
This sample solution was distilled to remove water. The residual liquid (sulfolane and xylene) remaining in the round bottom flask was extracted twice with 200 mL of pure water.

(Test 1-2)
The sample solution of Test 1-1 has the same chloride ion concentration and choline concentration, and a sample solution to which monoethanolamine (MEA) is added to a concentration of 172 mg / L is prepared. Distillation and extraction were performed in the same manner as in 1-1.

(Test 1-3)
The sample solution in Test 1-1 was the same in chloride ion concentration, and a sample solution to which choline hydroxide (choline) was not added was prepared. Otherwise, distillation and extraction were performed in the same manner as in Test 1-1. .

(Test 1-4)
The sample solution of Test 1-2 was the same in chloride ion concentration and MEA concentration, and a sample solution to which choline hydroxide (choline) was not added was prepared. Otherwise, distillation and extraction were performed in the same manner as in Test 1-2. Went.

  With respect to the first and second extraction liquids in the above tests, the respective concentrations of chloride ion, choline hydroxide and MEA were measured with a capillary electrophoresis analyzer. These measurement results are shown in Table 1.

As can be seen from the results shown in Table 1, the chloride ion concentration in the extract was 20 times higher when choline hydroxide was added (Test 1-1) than when it was not added (Test 1-3). The above was also high, and the improvement of the corrosive ion trapping effect in the aromatic compound extraction solvent was confirmed.
In addition, when choline hydroxide is added (Test 1-1), the chloride ion concentration in the extract is at least 15 times higher than when only MEA is added (Test 1-4), and aromatics are added. It was confirmed that the corrosive ion scavenging effect in the compound extraction solvent was more excellent.
When choline and MEA are added (Test 1-2), it can be said that the chloride ion concentration in the extract is further increased, and the corrosive ion trapping effect in the aromatic compound extraction solvent is further improved.

[Test 2] Test at an actual machine level In the apparatus shown in FIG. 1, an aromatic hydrocarbon oil containing benzene, toluene and xylene and sulfolane (chloride ion content concentration is 70 mg / L) are circulated. The following tests were conducted.
A choline hydroxide (choline) aqueous solution was added to the vicinity of the top outlet of the stripper column 5 once a week. The amount of choline hydroxide added was the same molar equivalent as the chloride ion in sulfolane. Chloride ions were extracted twice with 50 mL of pure water and the concentration was measured with an ion chromatograph.
After operating the apparatus for a predetermined number of days, 1 L of sulfolane was recovered from the bottom of the recovery column 6 and the chloride ion concentration in the sulfolane was measured. Table 2 shows the measurement results.

As can be seen from the results shown in Table 2, it was confirmed that the chloride ion concentration in the sulfolane recovered from the bottom of the recovery column 6 decreased as the integrated concentration of choline hydroxide increased. It was also confirmed that choline remained in the recovered sulfolane.
The chloride ion accumulation rate at the bottom of the regenerator 7 was 23 mg / (L · day) when no choline hydroxide was added, but 60 mg / (L when the choline hydroxide was added.・ Sun), about 3 times faster.
From these, it can be said that a good corrosive ion scavenging effect can be obtained by choline hydroxide in the actual machine.

DESCRIPTION OF SYMBOLS 1 Feed 2 Chloritoreter 3 Extraction tower 4 Washing tower 5 Stripper column 6 Recovery column 7 Regenerator 8 Process water stripper 9 Raffinate 10 Injection equipment (corrosive ion scavenger addition position)

Claims (11)

In a circulation system in which an aromatic compound extraction solvent circulates, a method of reducing corrosive ions in the aromatic compound extraction solvent,
The corrosive ion is at least one of chloride ion, sulfate ion and sulfite ion;
Adding a corrosive ion scavenger and reacting the corrosive ions with the corrosive ion scavenger to form a non-volatile salt; and concentrating the solvent containing the salt to remove the salt And a method for reducing corrosive ions in an aromatic compound extraction solvent.   The aromatic compound extraction solvent is selected from sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol, N-methylpyrrolidone, dimethyl sulfoxide, morpholine, N-formylmorpholine, methyl carbamate, diglycolamine, furfural and phenol. The method for reducing corrosive ions in the aromatic compound extraction solvent according to claim 1, which is at least one of them. The method for reducing corrosive ions in an aromatic compound extraction solvent according to claim 1 or 2, wherein the corrosive ion scavenger is a quaternary ammonium compound represented by the following general formula (1).

(In the formula ^(1), R 1 ~R ³ are each independently a hydrocarbon group having 1 to 4 carbon atoms, n represents an integer of 1 to 10.)   Corrosion ion reduction in the aromatic compound extraction solvent according to any one of claims 1 to 3, wherein any one or more selected from ammonia and neutralizing amines are used in combination in the circulation system. Method.   The method of reducing corrosive ions in an aromatic compound extraction solvent according to any one of claims 1 to 4, wherein the concentration is performed with a regenerator of the aromatic compound extraction solvent.   The fragrance according to any one of claims 1 to 5, wherein the corrosive ion scavenger has an addition frequency and an addition concentration determined based on a corrosive ion concentration in a circulating aromatic compound extraction solvent. Of reducing corrosive ions in extraction solvents for group compounds.   The method for reducing corrosive ions in an aromatic compound extraction solvent according to claim 6, wherein the corrosive ion scavenger is added so as to have a molar equivalent of 0.5 to 2 times the corrosive ion concentration. .   The aromatic compound according to any one of claims 1 to 5, wherein the corrosive ion scavenger has an addition frequency and a concentration determined based on a metal ion concentration in a circulating aromatic compound extraction solvent. A method for reducing corrosive ions in extraction solvents.   The method for reducing corrosive ions in an aromatic compound extraction solvent according to claim 8, wherein the metal ions are iron ions.   The method for reducing corrosive ions in an aromatic compound extraction solvent according to any one of claims 1 to 9, wherein the aromatic compound contains at least one selected from benzene, toluene and xylene.   The extraction method of an aromatic compound using the corrosive ion reduction method in the aromatic compound extraction solvent of any one of Claims 1-10.