Method for separating thiophene compounds from petroleum products and its application

Abstract

The application provides a method for separating thiophene compounds in petroleum oil products and application thereof, and the method comprises the following steps: S1: dissolving the petroleum oil product and an alkylating agent in a first solvent to obtain a dissolved oil sample; S2: loading a filler loaded with a catalyst into an adsorption column, transferring the dissolved oil sample into the adsorption column, standing, then sequentially eluting the adsorption column with a second solvent and a third solvent respectively, and collecting an eluent eluted by the third solvent; and S3: fully mixing the eluent with potassium iodide modified silica gel, filtering and collecting a filtrate, so that the thiophene compounds are separated. According to the method, the thiophene compounds in the petroleum can be separated with high purity and high yield, the operation condition of the method is mild, and the thiophene compounds in the petroleum oil products, especially in the high maturity crude oil, can be completely, efficiently and accurately separated.

Description

Technical Field

[0001] This invention relates to the field of petroleum separation technology, specifically to a method for separating thiophene compounds from petroleum products and its application. Background Technology

[0002] Thiophene compounds are chemically stable and are a class of organic sulfur-containing compounds commonly found in petroleum, especially in highly mature crude oils. During oil refining, residual organic sulfur compounds are typically short-chain thiophenes. Separating and enriching thiophene compounds in oil products helps reveal their transformation patterns during refining. Furthermore, in geochemistry, thiophene compounds are closely related to post-remediation processes such as thermal alteration and are widely used in oil-oil and oil-source correlation, containing important geochemical information.

[0003] Column chromatography and modified complexation column chromatography are currently the most common methods for separating thiophene compounds from oil products. However, the yield of thiophene compounds obtained by this method is not high, and interference from aromatic compounds is common. In addition, although high-purity separation and analysis of thiophene compounds can be achieved through chemical methods such as methyl derivatization and distributed reduction, these chemical reactions are very complex and the experimental cycle can take 3-4 days. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for separating thiophene compounds from petroleum products and its application. This method is simple to operate and can quickly and efficiently separate thiophene compounds from petroleum products.

[0005] To achieve the above objectives, the present invention provides a method for separating thiophene compounds from petroleum products, the method comprising the following steps:

[0006] S1: Dissolve petroleum products and alkylating agents in a first solvent to obtain a dissolved oil sample;

[0007] S2: The catalyst-supported packing is loaded into the adsorption column, the dissolved oil sample is transferred into the adsorption column, allowed to stand, and then the adsorption column is eluted sequentially with the second solvent and the third solvent, and the eluent eluted with the third solvent is collected.

[0008] S3: Mix the eluent thoroughly with potassium iodide-modified silica gel, filter and collect the filtrate to separate thiophene compounds.

[0009] In the above-described method for separating thiophene compounds from petroleum products, preferably, the alkylating agent includes iodomethane. Iodomethane has minimal steric hindrance, and the iodide ion is a good leaving group. Under the action of a catalyst, it can convert weakly polar sulfur-containing compounds into strongly polar methyl sulfonate salts, thereby creating a polarity difference with the petroleum matrix and enabling high-purity separation.

[0010] In the above-described method for separating thiophene compounds from petroleum products, preferably, the thiophene compounds include at least one of benzothiophene, dibenzothiophene, and benzonaphthothiophene, more preferably, 4,6-dimethyldibenzothiophene. The thiophene compounds can be any of all sulfides containing a thiophene ring.

[0011] In the above-described method for separating thiophene compounds from petroleum products, preferably, the catalyst comprises silver hexafluoroantimonate and / or silver tetrafluoroborate.

[0012] In the above-described method for separating thiophene compounds from petroleum products, preferably, the first, second, and third solvents each independently include at least one of n-hexane, dichloromethane, n-pentane, cyclohexane, acetonitrile, and methanol; wherein the first and second solvents may be the same or different, and the second and third solvents may be different.

[0013] In the above-described method for separating thiophene compounds from petroleum products, preferably, the first solvent includes at least one of n-pentane, n-hexane, and cyclohexane; the second solvent includes at least one of n-hexane, n-heptane, and cyclohexane; and the third solvent includes at least one of acetonitrile, dichloromethane, and methanol. The first solvent is used to dissolve the petroleum products, the second solvent is used to elute the weakly polar petroleum matrix from the petroleum products, and the third solvent is used to elute the strongly polar methylsulfonium salt.

[0014] In the above method for separating thiophene compounds from petroleum products, preferably, the volume ratio of the alkylating reagent to the petroleum product in S1 is 0.2-2:1.

[0015] In the above method for separating thiophene compounds from petroleum products, preferably, the volume ratio of the first solvent to the petroleum product in S1 is 10-100:1.

[0016] In the above method for separating thiophene compounds from petroleum products, preferably, the catalyst-supporting packing in step S2 is obtained by mixing a catalyst and packing in a mass ratio of 0.1-0.5:1-5; the mass ratio of the catalyst to the petroleum product is 0.1-0.5:1.

[0017] In the above method for separating thiophene compounds from petroleum products, preferably, the packing material is diatomaceous earth.

[0018] In the above method for separating thiophene compounds from petroleum products, preferably, the volume ratio of the second solvent to the petroleum product in step S2 is 50-200:1. The second solvent elution adsorption column is used to remove hydrocarbon matrix from the petroleum.

[0019] In the above method for separating thiophene compounds from petroleum products, preferably, S2 further includes: wetting the packing material in the adsorption column with the second solvent before allowing it to stand.

[0020] In the above method for separating thiophene compounds from petroleum products, preferably, the volume ratio of the third solvent to the petroleum product in step S2 is 10-100:1.

[0021] In the above method for separating thiophene compounds from petroleum products, preferably, the mass ratio of potassium iodide-modified silica gel to petroleum products in step S3 is 5-50:1.

[0022] In the above method for separating thiophene compounds from petroleum products, preferably, the silica gel in the potassium iodide modified silica gel in step S3 is silica gel that can pass through a 200-300 mesh sieve.

[0023] In the above method for separating thiophene compounds from petroleum products, preferably, the method for preparing potassium iodide modified silica gel in S3 is as follows: potassium iodide and silica gel are mixed in isopropanol to obtain a mixed system, the mixed system is washed with dichloromethane under hot reflux conditions, the obtained solid is separated and its solvent is removed to obtain the potassium iodide modified silica gel.

[0024] Preferably, in the preparation method of potassium iodide modified silica gel, the mass ratio of potassium iodide to silica gel is 0.1-1:10-20;

[0025] Preferably, in the method for preparing potassium iodide modified silica gel, the temperature of the hot reflux is 35-55℃ and the rinsing time is 0.5-1.5h.

[0026] Preferably, the preparation method of potassium iodide modified silica gel is as follows: 40 mL of saturated potassium iodide isopropanol solution is mixed with 20 g of silica gel, stirred for 5-10 min, and then the mixture is rinsed with 50 mL of dichloromethane under hot reflux conditions. After 1 h, the silica gel is taken out and the solvent is removed to obtain potassium iodide modified silica gel.

[0027] In the above method for separating thiophene compounds from petroleum products, preferably, the petroleum products are selected from one or more combinations of crude oil, diesel fraction, and vacuum gas oil fraction.

[0028] In the above method for separating thiophene compounds from petroleum products, preferably, the total sulfur content in the petroleum products is 0.1-10 wt% based on the total weight of the petroleum products.

[0029] In the above method for separating thiophene compounds from petroleum products, preferably, the amounts of petroleum products, methylating reagent, first / second / third solvent, and potassium iodide modified silica gel are in a proportional relationship, and more preferably, in a linear relationship of equal proportions.

[0030] In the above-described method for separating thiophene compounds from petroleum products, preferably, step S3 further includes concentrating the filtrate. The method for concentrating the filtrate can be a conventional concentration method in the art, such as using a rotary evaporator under reduced pressure to remove the third solvent. There are no special requirements for the specific degree of concentration in this invention; generally, most of the third solvent can be removed, depending on the needs of subsequent processes.

[0031] In the method for separating thiophene compounds in petroleum products according to the present invention, in order to shorten the overall separation time, the eluent can be directly received in a container containing potassium iodide modified silica gel while eluting with the third solvent in S2. The mixing and contact of the eluent and potassium iodide modified silica gel is completed when the elution is finished.

[0032] In the method for separating thiophene compounds from petroleum products according to the present invention, the eluent of the second solvent in S2 and the filtrate in S3 can be routinely analyzed by those skilled in the art. For example, a mixed standard sample containing sulfur-containing compounds with non-reacting n-alkanes as internal standards can be prepared, and gas chromatography-tandem mass spectrometry (GC-MS) analysis can be performed on the test solution with a concentration of 10 mg / mL (calculated based on the concentrated mixture as the solute) before and after separation. In some specific embodiments, the yield of dibenzothiophene was found to be 99.8%, and the yield of dimethyl-substituted dibenzothiophene was 96.4%.

[0033] The present invention also provides the application of the above-described method for separating thiophene compounds from petroleum products in the detection of thiophene compounds in petroleum products.

[0034] The technical solution provided by this invention has the following beneficial effects:

[0035] The method for separating thiophene compounds from petroleum products provided by this invention can separate thiophene compounds from petroleum with high purity and high yield. The method operates under mild conditions and can completely, efficiently and accurately separate thiophene compounds from petroleum products, especially from highly mature crude oil. Attached Figure Description

[0036] Figure 1 The images show the GC-SCD chromatogram of the catalytic cracked diesel oil in Example 1, and the GC-MS total ion chromatogram of the thiophene compounds separated from the catalytic cracked diesel oil.

[0037] Figure 2The total ion chromatogram and selected ion spectra of thiophene compounds obtained from crude oil separation in Example 2 are shown in the figure.

[0038] Figure 3 The GC-SCD chromatograms of the two groups of filtrates in Experiment Example 1 are shown below.

[0039] Figure 4 The total ion chromatograms were obtained by GC-MS analysis of a mixed standard sample of different sulfides with n-alkanes as internal standards in Experiment Example 2, and the thiophene component separated from it. Detailed Implementation

[0040] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0041] The potassium iodide-modified silica gel used in the embodiments of this invention was prepared by the following method:

[0042] Mix 40 mL of saturated potassium iodide isopropanol solution with 20 g of silica gel, stir for 10 min, and then rinse the mixture with 50 mL of dichloromethane under reflux at 50 °C. After 1 h, remove the silica gel and remove the solvent to obtain potassium iodide modified silica gel.

[0043] Example 1

[0044] This embodiment provides a method for separating thiophene compounds from diesel fuel, the specific steps of which are as follows:

[0045] 100 mg of catalytic cracked diesel sample (total sulfur content 1.02 wt%) and 0.3 mL of iodomethane were added to a 2 mL chromatographic bottle, followed by 0.5 mL of n-hexane. The sample bottle was shaken to completely dissolve the sample, resulting in a dissolved oil sample. Diatomaceous earth loaded with silver hexafluoroantimonate (containing 3 g of diatomaceous earth and 200 mg of silver hexafluoroantimonate) was packed into an adsorption column. The resulting dissolved oil sample was transferred to the adsorption column, and a small amount of n-hexane was added to wet the packing material. The column was allowed to stand for 2 hours. Initial elution was performed with 30 mL of n-hexane, and the eluent was discarded. A second elution was performed with 30 mL of dichloromethane. This eluent was collected in a beaker containing 2.0 g of potassium iodide-modified silica gel. After elution, the mixture in the beaker was filtered. The filtrate was the thiophene component. The solvent in the filtrate was removed to separate the thiophene compounds.

[0046] In this embodiment, the sulfur chemiluminescence gas chromatogram (GC-SCD chromatogram) of the catalytic cracking diesel sample and the total ion chromatogram of the separated thiophene component by gas chromatography-mass spectrometry (GC-MS) are shown below. Figure 1As shown in the figure, gas chromatography-sulfur chemiluminescence detector (GC-SCD) only responded to organic sulfides in the sample, while gas chromatography-mass spectrometry (GC-MS) responded to all organic compounds. The results indicate that catalytic cracking diesel contains abundant benzothiophene and dibenzothiophene series compounds, and the distribution of the separated thiophene compounds is almost identical to the distribution in the GC-SCD chromatogram of the diesel sample. This demonstrates that the above method achieves high purity separation of thiophene compounds in diesel samples and can efficiently separate different thiophene compounds. Furthermore, the entire separation process is short, completed within 3 hours.

[0047] Example 2

[0048] This embodiment provides a method for separating thiophene compounds from highly mature crude oil, the specific steps of which are as follows:

[0049] Add 70 mg of highly mature crude oil (total sulfur content 4.13 wt%) and 0.3 mL of iodomethane to a 2 mL chromatographic vial, then add 0.5 mL of n-hexane. Shake the vial to completely dissolve the sample. Load diatomaceous earth (containing 4 g of diatomaceous earth and 250 mg of silver hexafluoroantimonate) onto an adsorption column. Transfer the dissolved oil sample to the adsorption column. Add a small amount of n-hexane to wet the packing material and let it stand for 2 hours. Perform initial elution with 30 mL of n-hexane and discard the eluent. Perform secondary elution with 30 mL of dichloromethane. This time, collect the eluent in a beaker containing 2.5 g of potassium iodide-modified silica gel. After elution, filter the mixture in the beaker. The filtrate is the thiophene component. Remove the solvent from the filtrate to separate the thiophene compounds.

[0050] In this embodiment, the GC-MS total ion chromatogram of the separated thiophene component and the selected ion spectrum of the thiophene compounds are shown below. Figure 2 As shown in the figure, the results indicate that benzothiophene, dibenzothiophene, and benzonaphthothiophene compounds in highly mature crude oil can all be separated using the above method. Furthermore, comparison of the total ion chromatogram and the selected ion spectrum of thiophene compounds shows that the above method achieves high purity separation of thiophene compounds with minimal interference from non-thiophene compounds. The entire process is quick, taking only 3 hours to complete.

[0051] Experimental Example 1

[0052] This experimental example compares the thiophene compounds in the two elution fractions in Example 2.

[0053] Collect the eluent obtained from elution with 30 mL of n-hexane and the eluent obtained from elution with 30 mL of dichloromethane in Example 2. Receive the two sets of eluents separately in beakers containing 2.5 g of potassium iodide-modified silica gel. After elution, filter the mixture in the beakers, concentrate both filtrates to the same volume, and perform GC-SCD analysis under the same conditions. The GC-SCD spectra are shown below. Figure 3 As shown.

[0054] GC-SCD only responds to organic sulfides. Among them, the dichloromethane eluent (thiophene fraction) has significant thiophene compound distribution characteristics, while the n-hexane eluent does not have characteristic peaks of thiophene compounds. This further illustrates that the above method can efficiently and with high purity enrich thiophene compounds in crude oil.

[0055] Experiment Example 2

[0056] This experimental example is used to test the selectivity and yield of the method for separating thiophene compounds from petroleum products according to the present invention.

[0057] This experimental example provides a method for separating thiophene compounds from model sulfides and calculating the yield of thiophene compounds. The specific steps are as follows:

[0058] Add 0.1 g of a mixed standard (dibenzothiophene, 4,6-dimethyldibenzothiophene, C24 sulfide, and n-C16 alkanes, all at a concentration of 0.01 mmol / mL) and 0.2 mL of iodomethane to a 2 mL chromatographic vial, then add 0.5 mL of n-hexane and shake the vial to mix thoroughly. Add the mixture to a diatomaceous earth column loaded with silver hexafluoroantimonate (containing 2 g of diatomaceous earth and 150 mg of silver hexafluoroantimonate), then add a small amount of n-hexane to the adsorption column to just wet the packing material. Let it stand for 2 hours. Elute sequentially with 20 mL of n-hexane and 30 mL of dichloromethane. Collect the eluents from both solvents in a beaker containing 2 g of potassium iodide-modified silica gel. After elution, filter the mixture in the beaker. The filtrate is the thiophene component containing the internal standard (n-C16 alkanes).

[0059] In this embodiment, the GC-MS total ion chromatogram of the mixed standard and the thiophene component containing the internal standard obtained by separation is shown below. Figure 4 As shown. The results indicate that the enriched thiophene fraction was free from interference from other types of sulfides, demonstrating that the separation method of this invention exhibits high selectivity for thiophene compounds. Using internal standard compounds as references, the yields of benzothiophene and 4,6-dimethyldibenzothiophene were determined to be 99.8% and 96.4%, respectively. The above method demonstrates high purity and high conversion efficiency (the percentage of separated standard sample relative to the original standard sample).

Claims

1. A method for separating thiophene compounds from a petroleum oil product, comprising the steps of: S1: dissolving the petroleum oil product and the alkylating agent in a first solvent to obtain a dissolved oil sample; wherein, the alkylating agent comprises methyl iodide, and the first solvent comprises at least one of n-pentane, n-hexane, and cyclohexane; S2: loading a packing material carrying a catalyst into an adsorption column, the catalyst comprising silver hexafluoroantimonate and / or silver tetrafluoroborate, transferring the dissolved oil sample into the adsorption column, standing, and then sequentially eluting the adsorption column with a second solvent and a third solvent, respectively, and collecting the eluate eluted by the third solvent; wherein the second solvent comprises at least one of n-hexane, n-heptane, and cyclohexane, and the third solvent comprises at least one of acetonitrile, dichloromethane, and methanol; the packing material carrying the catalyst is obtained by mixing the catalyst and the packing material at a mass ratio of 0.1-0.5:1-5, the mass ratio of the catalyst to the petroleum oil product is 0.1-0.5:1, and the packing material is diatomite; the volume ratio of the second solvent to the petroleum oil product is 50-200:1, and the volume ratio of the third solvent to the petroleum oil product is 10-100:1; S3: mixing the eluate with potassium iodide-modified silica gel, filtering, and collecting the filtrate, thereby separating thiophene compounds, the thiophene compounds comprising at least one of benzothiophene, dibenzothiophene, and benzonaphthothiophene; wherein the mass ratio of the potassium iodide-modified silica gel to the petroleum oil product is 5-50:1; the method for preparing the potassium iodide-modified silica gel comprises: mixing potassium iodide and silica gel at a mass ratio of 0.1-1:10-20 in isopropyl alcohol to obtain a mixed system, eluting the mixed system with dichloromethane under the condition of thermal reflux at 35-55°C for 0.5-1.5 h, separating the obtained solid and removing the solvent therefrom, and obtaining the potassium iodide-modified silica gel.

2. The method of separating thiophenic compounds from a petroleum oil product of claim 1, wherein, In S1, the volume ratio of the alkylating agent to the petroleum oil product is 0.2-2:

1.

3. The method of separating thiophenic compounds from petroleum oil products according to claim 1, wherein, In S1, the volume ratio of the first solvent to the petroleum oil product is 10-100:

1.

4. The method of separating thiophenic compounds from petroleum oil products according to claim 1, wherein, S2 further comprises: before standing, wetting the packing material in the adsorption column with the second solvent.

5. The method of separating thiophenic compounds from petroleum oil products according to claim 1, wherein, The silica gel in the potassium iodide-modified silica gel is silica gel capable of passing through a 200-300 mesh screen.

6. The method of separating thiophenic compounds from petroleum oil products according to claim 1, wherein, The petroleum oil product is selected from one or a combination of two or more of crude oil, diesel distillate, and vacuum gas oil distillate.

7. The method of separating thiophenic compounds from petroleum oil products according to claim 1, wherein, The total sulfur content in the petroleum oil product is 0.1-10 wt% based on the total weight of the petroleum oil product.

8. Use of the method for separating thiophene compounds from a petroleum oil product according to any one of claims 1-7 in detecting thiophene compounds in a petroleum oil product.

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