A method for enriching and separating mercaptan-containing sulfur compounds in coking benzene hydrogenation xylene products

Abstract

The present invention belongs to the field of chemical engineering and specifically relates to a method for enriching and separating mercaptan-containing sulfur compounds in a xylene product produced by hydrogenation of coking benzene. The method comprises: oxidizing the xylene product with iodine or oxygen as an oxidant to convert the mercaptan compounds in the xylene product into disulfide compounds; utilizing the large difference in boiling points between the disulfide compounds and xylene, the majority of the xylene is separated by distillation, thereby achieving enrichment and separation of the mercaptan compounds. The method for enriching and separating the mercaptan-containing sulfur compounds is simple, low-cost, and well-suited for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a method for enriching and separating mercaptan-type sulfur-containing compounds in a coking benzene hydrogenation xylene product. Background Art

[0002] Hydrodesulfurization (HDS) is a key technology for the hydrorefining of petrochemical heavy oil fractions. While the hydrogenation conditions are relatively mild, while reducing the total sulfur content, the hydrogenation process generates secondary, large-molecule mercaptans (heavy mercaptans) and other sulfur-containing compounds. While mercaptans are present in low concentrations in the hydrogenated heavy fraction, they are highly stable and difficult to remove. The presence of these mercaptans can cause an odor in the oil product. The catalysts, hydrogenation equipment, and hydrogenation reaction parameters used in the coking benzene hydrogenation process closely resemble those used in the petrochemical HDS process. In actual production, the presence of mercaptans in the benzene hydrogenation-xylene product also produces an odor, which not only reduces product quality but also adversely affects the subsequent processing and use of the xylene product. However, due to the very low sulfur content (<1.0 ppm) in the benzene hydrogenation-xylene product, accurate analysis and determination of these mercaptans is difficult, necessitating the enrichment and separation of these mercaptans in the xylene product.

[0003] The enrichment and separation of mercaptan-containing sulfur compounds in petrochemical hydrotreated oil products is usually carried out by solvent extraction, which often requires a specific extractant (Analysis of the Structural Composition of Mercaptans in Hydrotreated Gasoline and Their Deodorization [D], China University of Petroleum, 2011), and the operation steps are relatively cumbersome. Due to the significant difference in composition between the xylene products produced by hydrogenation of coking benzene and petrochemical hydrotreated oil products, the enrichment and separation treatment methods for petrochemical hydrotreated oil products are not fully applicable to the xylene products produced by hydrogenation of coal coking benzene. No relevant literature has been reported on the enrichment and separation treatment methods for mercaptan-containing sulfur compounds in xylene products.

[0004] Therefore, the determination of the enrichment and separation method of mercaptan sulfur-containing compounds in xylene products can realize the accurate analysis and determination of mercaptan sulfur-containing compounds, which is of great significance to the improvement of product quality and subsequent processing and utilization. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above problems existing in the conventional technology and provide a method for enriching and separating mercaptan-type sulfur-containing compounds in the product of coking benzene hydrogenation xylene.

[0006] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0007] A method for enriching and separating mercaptan-type sulfur-containing compounds in a coking benzene hydrogenation xylene product comprises first oxidizing the mercaptan compounds into disulfide compounds using a weak oxidant, and then utilizing the large difference in boiling points between the disulfide compounds and xylene to separate most of the xylene by distillation, thereby completing the enrichment and separation of the mercaptan compounds.

[0008] Furthermore, the method for enriching and separating mercaptan-type sulfur-containing compounds in the coking benzene hydrogenation xylene product as described above comprises the following steps:

[0009] 1) taking an appropriate amount of xylene product and performing oxidation treatment with iodine or oxygen as an oxidant to obtain oxidized pretreated xylene;

[0010] 2) taking an appropriate amount of the oxidized pretreated xylene obtained in step 1) and placing it in a vacuum distillation apparatus, and performing distillation separation under the conditions of 1.3-2.0 kPa and 50-70° C., and ending the distillation when a certain amount of material remains at the bottom of the kettle, collecting and accurately measuring the volume of the collected distillation bottom at room temperature, wherein the collected distillation bottom is the enriched and separated thiol sulfur-containing compound sample.

[0011] Furthermore, in the above-mentioned method for enriching and separating mercaptan-type sulfur-containing compounds in the xylene product of coking benzene hydrogenation, in step 1), the xylene product is a xylene product obtained by hydrogenating coal coking benzene.

[0012] Furthermore, in the above-mentioned method for enriching and separating mercaptan-type sulfur-containing compounds in the coking benzene hydrogenation xylene product, in step 1), when the oxidant is iodine, the specific operation of the iodine oxidation treatment is: adding an iodine xylene solution with an iodine mass concentration of 20 to 40 wt% to an appropriate amount of xylene product, and after oxidation treatment at room temperature for 4 to 10 hours, obtaining iodine-oxidized pretreated xylene.

[0013] Furthermore, in the above-mentioned method for enriching and separating mercaptan sulfur-containing compounds in the xylene product of coking benzene hydrogenation, the volume ratio of the iodine xylene solution to the xylene product is 2 to 4:100.

[0014] Furthermore, in the above-mentioned method for enriching and separating mercaptan-type sulfur-containing compounds in the coking benzene hydrogenation xylene product, in step 1), when the oxidant is oxygen, the specific operation of the oxygen oxidation treatment is: taking an appropriate amount of xylene product and treating it in an oxygen atmosphere at room temperature to 70°C for 4 to 10 hours, and then cooling it to room temperature to obtain oxygen-oxidized pretreated xylene.

[0015] Furthermore, in the above-mentioned method for enriching and separating mercaptan-type sulfur-containing compounds in the coking benzene hydrogenation xylene product, in step 2), the distillation separation is vacuum distillation.

[0016] Furthermore, in the above-mentioned method for enriching and separating mercaptan sulfur-containing compounds in the coking benzene hydrogenation xylene product, in step 2), the distillation is terminated when the volume ratio of the residual material at the bottom of the kettle to the oxidized pretreated xylene is 5-10:100.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention utilizes the fact that mercaptan compounds are easily oxidized by weak oxidants to form disulfide compounds. Since the xylene product obtained by hydrogenation of coal coking benzene is obtained by distillation separation, the boiling point of the mercaptan compounds contained therein is close to that of xylene. The disulfide compounds formed by oxidation of mercaptan compounds have a boiling point higher than not only mercaptan compounds but also xylene. By utilizing the large difference in boiling points between disulfide compounds and xylene, most of the xylene is separated by distillation, thereby completing the enrichment and separation of mercaptan compounds.

[0019] 2. The enrichment and separation of mercaptan-type sulfur-containing compounds of the present invention is simple, low-cost, and very suitable for industrial production.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] The relevant specific embodiments of the present invention are as follows:

[0023] Example 1

[0024] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., with specific composition shown in Table 1) was placed in a 500 ml three-necked flask, and 4.0 ml of a 40 wt% iodine-containing xylene solution was added. The mixture was oxidized at room temperature for 4 hours to obtain an iodine-oxidized pretreated xylene sample. 100 ml of the iodine-oxidized pretreated xylene was placed in a vacuum distillation apparatus at a pressure of 2.0 kPa and 70° C. for distillation separation. Distillation was terminated when 5 ml of material remained at the bottom of the kettle. The distillation bottoms were collected to obtain an enriched and separated mercaptan sulfur-containing compound sample. The sulfur content of the sample was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0025] Example 2

[0026] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., with specific composition shown in Table 1) was placed in a 500 ml three-necked flask, and 6.0 ml of a 30 wt% iodine-containing xylene solution was added. The mixture was oxidized at room temperature for 8 hours to obtain an iodine-oxidized pretreated xylene sample. 100 ml of the iodine-oxidized pretreated xylene was placed in a vacuum distillation apparatus at a pressure of 1.6 kPa and 60° C. for distillation separation. Distillation was terminated when 8 ml of material remained at the bottom of the kettle. The distillation bottoms were collected to obtain an enriched and separated mercaptan sulfur-containing compound sample. The sulfur content of the sample was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0027] Example 3

[0028] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., with specific composition shown in Table 1) was placed in a 500 ml three-necked flask, and 8.0 ml of a 20 wt% iodine-containing xylene solution was added. The mixture was oxidized at room temperature for 10 hours to obtain an iodine-pretreated xylene sample. 100 ml of the iodine-pretreated xylene was placed in a vacuum distillation apparatus at a pressure of 1.3 kPa and 50° C. for distillation separation. Distillation was terminated when 10 ml of material remained at the bottom of the kettle. The distillation bottoms were collected to obtain an enriched and separated mercaptan sulfur-containing compound sample. The sulfur content of the sample was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0029] Example 4

[0030] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., for specific composition, see Table 1) was placed in a 500 ml three-necked flask and oxidized with oxygen at 70°C for 4 hours to obtain an oxygen-oxidized pretreated xylene sample. 100 ml of the oxygen-oxidized pretreated xylene was then distilled and separated in a vacuum distillation apparatus at 1.3 kPa and 50°C until 10 ml of material remained at the bottom of the still. The distillation bottoms were collected to obtain an enriched and separated sample of mercaptan sulfur compounds. The sulfur content was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0031] Example 5

[0032] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., for specific composition, see Table 1) was placed in a 500 ml three-necked flask and oxidized with oxygen at 50°C for 8 hours to obtain an oxygen-oxidized pretreated xylene sample. 100 ml of the oxygen-oxidized pretreated xylene was then distilled and separated in a vacuum distillation apparatus at 1.6 kPa and 60°C until 8 ml of material remained at the bottom of the still. The distillation bottoms were collected to obtain an enriched and separated sample of mercaptan sulfur compounds. The sulfur content was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0033] Example 6

[0034] 200 ml of xylene (benzene hydrogenated xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., for specific composition, see Table 1) was placed in a 500 ml three-necked flask and oxidized with oxygen at room temperature for 10 hours to obtain an oxygen-oxidized pretreated xylene sample. 100 ml of the oxygen-oxidized pretreated xylene was then distilled and separated at 2.0 kPa and 70°C in a vacuum distillation apparatus until 5 ml of material remained at the bottom of the still. The distillation bottoms were collected to obtain an enriched and separated sample of mercaptan sulfur compounds. The sulfur content was analyzed using a JF-TSN-3000 sulfur-nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0035] Comparative Example

[0036] 100 ml of xylene (benzene hydrogenation xylene product from Anhui Magang Chemical Energy Technology Co., Ltd., specific composition is shown in Table 1) was placed in a vacuum distillation apparatus at a pressure of 2.0 kPa and 70° C. for distillation separation. The distillation was terminated when 5 ml of material remained at the bottom of the kettle. The distillation bottoms were collected to obtain an enriched and separated sample of mercaptan sulfur-containing compounds. The sulfur content was analyzed using a JF-TSN-3000 sulfur and nitrogen analyzer (Jiangsu Jiangfen Electronic Analytical Instrument Co., Ltd.). The sulfur content test results are shown in Table 2.

[0037] Table 1 Main components of xylene products

[0038]

[0039] The results in Table 2 show that the enrichment and separation method of the present invention for mercaptan sulfur-containing compounds has a good enrichment and separation effect. In the comparative example, the total sulfur content of the distilled raw material and the sample after enrichment and separation is 0.8ppm and 0.9ppm, respectively, and the sulfur content is substantially unchanged, indicating that mercaptan sulfur-containing compounds cannot be effectively enriched and separated without oxidation treatment. Both iodine oxidation and oxygen oxidation can achieve the enrichment and separation of mercaptan sulfur-containing compounds. After iodine oxidation treatment in Example 1, the total sulfur content of the 5ml sample obtained by enrichment and separation reaches 21.4ppm. After oxygen oxidation treatment in Example 4, the total sulfur content of the 10ml sample obtained by enrichment and separation reaches 10.8ppm, both of which are significantly improved compared with the 0.9ppm of the sample obtained by enrichment and separation in the comparative example. The enrichment and separation of mercaptan sulfur-containing compounds of the present invention is simple, low-cost, and very suitable for industrial production.

[0040] Table 2 Sulfur content of enriched and separated samples in different embodiments

[0041]

[0042] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for enriching and separating mercaptan-type sulfur-containing compounds in a coking benzene hydrogenation xylene product, characterized in that: The method comprises the following steps: firstly, mercaptan compounds are oxidized by a weak oxidant to be converted into disulfide compounds; then, by utilizing the large difference in boiling points between disulfide compounds and xylene, most of the xylene is separated by distillation, thereby completing the enrichment and separation of the mercaptan compounds; The steps include: 1) taking an appropriate amount of xylene product and performing oxidation treatment with iodine or oxygen as an oxidant to obtain oxidized pretreated xylene; the xylene product is a xylene product obtained by hydrogenation of coal coking benzene; 2) taking an appropriate amount of the oxidized pretreated xylene obtained in step 1) and placing it in a vacuum distillation apparatus, and performing distillation separation under the conditions of 1.3-2.0 kPa and 50-70° C., wherein the distillation separation is vacuum distillation, and the distillation is terminated when the volume ratio of the residual material at the bottom of the kettle to the oxidized pretreated xylene is 5-10:100, collecting and accurately measuring the volume of the collected distillation bottom at room temperature, wherein the collected distillation bottom is the enriched and separated thiol sulfur-containing compound sample.

2. The method for enriching and separating mercaptan sulfur-containing compounds in the coking benzene hydrogenation xylene product according to claim 1, characterized in that: In step 1), when the oxidant is iodine, the specific operation of the iodine oxidation treatment is: adding an iodine-xylene solution with an iodine mass concentration of 20 to 40 wt% to an appropriate amount of xylene product, and oxidizing it at room temperature for 4 to 10 hours to obtain iodine-oxidized pretreated xylene.

3. The method for enriching and separating mercaptan sulfur-containing compounds in the coking benzene hydrogenation xylene product according to claim 2, characterized in that: The volume ratio of the iodine-xylene solution to the xylene product is 2 to 4:

100.

4. The method for enriching and separating mercaptan sulfur-containing compounds in the coking benzene hydrogenation xylene product according to claim 1, characterized in that: In step 1), when the oxidant is oxygen, the specific operation of the oxygen oxidation treatment is: taking an appropriate amount of xylene product and treating it in an oxygen atmosphere at room temperature to 70°C for 4 to 10 hours, and then cooling it to room temperature to obtain oxygen-oxidized pretreated xylene.

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