An extractant for detecting inorganic chloride ions in oil products

Abstract

The present invention discloses an extractant for detecting inorganic chloride ions in oil products. The extractant comprises a solution A, a low-polymerization-degree polyoxyethylene fatty alcohol ether (L), and a strong base weak acid salt. The solution A is a mixture of water and ethanol or a mixture of water and isopropanol. The degree of polymerization of the low-polymerization-degree polyoxyethylene fatty alcohol ether (L) is 10-20. The strong base weak acid salt is sodium acetate. The extractant is weakly alkaline and has a pH of 8.5-9.0. This extractant for detecting inorganic chloride ions in oil products can resolve the emulsion layer phenomenon during extraction and centrifugation in inorganic chloride ion determination of some oil products. It also steadily increases the extraction rate of the current SY / T0536 method from approximately 95% to over 98%, and has a wider range of applicability for extracting inorganic chloride from oil products.

Description

Technical Field

[0001] The present invention relates to the field of analytical chemistry, and in particular to an extractant for detecting inorganic chloride ions in oil products. Background Art

[0002] In oil refining units, inorganic chloride ions in oil products are the primary corrosion factor in low-temperature areas. They can cause uniform corrosion of carbon steel, pitting corrosion of austenitic stainless steel, and chloride stress corrosion cracking, leading to serious corrosion problems in atmospheric and vacuum distillation units and subsequent processing units such as delayed coking and catalytic cracking units. The presence of chloride ions creates a tendency for cracking, and inorganic chloride ions are also the primary cause of ammonium salt scaling.

[0003] Testing for inorganic chloride ions in oil products requires extracting the inorganic chloride ions into a hydroalcoholic phase. Depending on the laboratory equipment, this is then analyzed using coulometric titration, potentiometric titration, conductivity measurement, or ion chromatography. The extraction solvents commonly used in standard analytical methods for inorganic chloride ion testing are mixed solutions of water and ethanol (isopropanol) or mixed solutions of water, ethanol (isopropanol), and acetone.

[0004] For example, the widely used method for determining inorganic chloride ions in crude oil (coulometric method) in SY / T 0536-2008 can be used to determine the inorganic chloride ion content in crude oil and its products. This method dilutes the oil in xylene to make it flowable, then adds a mixed polar solvent such as water and ethanol. Through heating and shaking, the aqueous alcohol solution can extract most of the inorganic chloride ions in the oil. After centrifugation, an appropriate amount of the clarified extractant at the bottom is drawn with a syringe and injected into the electrolytic titration cell. The inorganic chloride ions can then react with the silver ions in the electrolyte: Cl - +Ag + →AgCl↓, the result of this reaction is Ag + As the concentration decreases, the measuring-reference electrode pair will send the potential difference caused by the decrease in silver ion concentration into the microcoulomb amplifier, and the anode electrolyzes the silver electrode, thereby generating Ag + To replenish the Ag consumed in the previous reaction + , measure the replenishment of consumed Ag +The amount of electricity required can be used to calculate the chloride ion content in the crude oil based on Faraday's law. This method also requires that the extractant solution after centrifugation must be clear. Actual sample tests revealed that some crude oil, third-line oil, raw wax oil, and extracted solutions from refined wax oil were turbid. Almost all crude oil residue, fourth-line oil, heavy hydrogenation feedstock, catalytic feedstock, and cracking feedstock, when thoroughly oscillated and mixed with the aforementioned hydroalcoholic solution, exhibited an unclear interface between the organic and aqueous phases during extraction, exhibiting a certain degree of emulsification. This resulted in a severe emulsion layer, and even high-speed centrifugation failed to separate the two phases. Instead, a three-phase phenomenon of oil, emulsion, and hydroalcohol layer formed. Furthermore, the thickness, viscosity, and color of the emulsion layer varied depending on the source of the oil. The inorganic chloride ion extraction process is crucial for accurate subsequent testing. While the hydroalcoholic extractant used in standard analytical methods can extract approximately 90% of the inorganic chloride ions in oil, further improving the extraction rate of inorganic chloride ions in oil products would also facilitate more accurate testing. Therefore, it is necessary to develop an extractant for inorganic chloride ion detection in oil products that is highly efficient and emulsion-free. CN 112461628 A discloses an integrated batch pretreatment and sampling method for salt content in oil products. The invention discloses an acidic extracting solution, which stabilizes the extraction rate of inorganic salts such as chlorides and facilitates stratification. Experiments have shown that high-frequency shaking mixed extraction and centrifugal stratification result in poor demulsification of some heavy oil products, turbidity of the extractant solution, and decreased extraction rate of inorganic chlorine. Summary of the Invention

[0005] The purpose of the present invention is to provide an extractant for detecting inorganic chloride ions in oil products, which can solve the emulsion layer phenomenon during extraction and centrifugation of inorganic chloride ions in different oil products and has a wider adaptability to oil product extraction.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Disclosed is an extractant for detecting inorganic chloride ions in oil products. The extractant comprises solution A, L low-polymerization-degree polyoxyethylene fatty alcohol ether, and a strong base weak acid salt. Solution A is a mixture of water and ethanol or a mixture of water and isopropanol. The degree of polymerization of the L low-polymerization-degree polyoxyethylene fatty alcohol ether is 10-20.

[0008] Preferably, the volume ratio of water to ethanol in the mixture of water and ethanol is 3:1.

[0009] Preferably, the volume ratio of water to isopropyl alcohol in the mixture of water and isopropyl alcohol is 3:1.

[0010] Preferably, the mass concentration of the L low-polymerization degree polyoxyethylene fatty alcohol ether is greater than or equal to 10 mg / L.

[0011] Preferably, the strong base weak acid salt is sodium acetate, and the concentration of the strong base weak acid salt is 0.05 to 0.2 mol / L.

[0012] Preferably, the pH of the extractant is 8.0-9.0.

[0013] Preferably, the pH of the extractant is adjusted by acetic acid or sodium hydroxide.

[0014] A method for preparing an extractant for detecting inorganic chloride ions in oil products comprises the following steps: weighing 4.1 g to 16.4 g of a strong base and a weak acid salt, adding not less than 0.5 mL of a L-low polymerization degree polyoxyethylene fatty alcohol ether stock solution, diluting the volume to 1 L with solution A, and adjusting the pH of the extractant to 8.5 to 9.0 with acetic acid or sodium hydroxide for standby use.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) Adding an appropriate amount of L low-polymerization degree polyoxyethylene fatty alcohol ether to the water-ethanol (isopropanol) solution eliminates the problem of thick emulsion layer and inability to separate samples when fully mixing oil and water to extract inorganic chloride ions in the SY / T0536-2008 method;

[0017] 2) The weakly alkaline extractant solution of the present invention includes sodium acetate. When the pH of the extractant is 8.5-9.0, it has a certain acid-base buffering capacity and has the best and most stable effect on the extraction rate of inorganic chloride ions from oil products. The inorganic chloride ion extraction rate is stably increased from about 95% in the SY / T0536-2008 method to more than 98%.

[0018] 3) The extractant solution of the present invention can separate the oil into two distinct phases after centrifugation, and the extract is transparent. The centrifuge tubes of different volumes and capacities are matched to lay the foundation for the precise detection of different inorganic chloride ions such as conductivity measurement, coulometric measurement, potentiometric titration, and ion chromatography. DETAILED DESCRIPTION

[0019] 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 part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0020] The present invention provides a weakly alkaline extractant for inorganic chlorine detection in oil products. Pre-detection extraction of inorganic chloride ions in oil products is performed according to the method steps of SY / T 0536-2008. The extractant solution comprises a water-ethanol or water-isopropanol solution in a volume ratio of 3:1, containing at least 10 mg / L of a low-polymerization polyoxyethylene fatty alcohol ether and 0.05-0.2 mol / L of sodium acetate. The extractant solution is weakly alkaline and has a pH of 8.5-9.0 (adjusted by acetic acid or sodium hydroxide). The oil product is first mixed with the diluent xylene, and then the extractant of the present invention is added. After constant temperature shaking and centrifugation to separate the layers, an appropriate amount of the extractant solution containing inorganic chloride ions in the lower layer is extracted. The inorganic chloride ion content is measured by coulometric (microcoulometric) measurement, potentiometric titration, or ion chromatography analysis, and the inorganic chloride ion content of the oil product, expressed in mgCl / L, is ultimately calculated according to the corresponding formula.

[0021] The technical solution of the present invention is further described in detail below through specific embodiments:

[0022] Example 1

[0023] An extractant for detecting inorganic chloride ions in oil products, comprising a water-ethanol solution in a volume ratio of 3:1, 0.1 mol / L of sodium acetate, and 25 mg / L of a polyoxyethylene fatty alcohol ether with a degree of polymerization of 10, wherein the pH of the extractant is 8.9.

[0024] Weigh 7.87 g of crude oil A into a 50 mL conical-bottom centrifuge tube with a cap, accurate to 0.01 g, and add 10 mL of xylene to mix thoroughly. Add 15 mL of the extractant solution of this example, followed by a few drops of hydrogen peroxide. Tighten the cap to seal the tube, and perform constant temperature shaking and centrifugation according to the SY / T 0536 standard method. The oil solution and the extract solution will separate into layers, and the extract will be transparent. Loosen the cap and extract an appropriate amount of the extract from the lower layer. Perform a coulometric (microcoulomb) measurement, and calculate the inorganic chlorine content of the oil (26.3 mgCl / L) according to the corresponding formula.

[0025] Example 2

[0026] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-isopropanol solution with a volume ratio of 3:1, the solution containing 0.2 mol / L of sodium acetate and 35 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 16, and the pH of the extractant being 8.6.

[0027] Weigh 5.05 g of desalted crude oil B into a 50 mL capped centrifuge tube, accurate to 0.01 g, and add 10 mL of xylene to mix thoroughly. Add 12 mL of the extractant solution of this example, and tighten the cap to seal. Centrifuge at a constant temperature with shaking according to the procedures of the SY / T 0536 standard method, allowing the oil solution and the extract solution to separate into layers, leaving the extract transparent. Loosen the cap, remove an appropriate amount of the extract from the lower layer, and activate the coulometric inorganic chloride analyzer application to measure the chloride ion content. Calculate the inorganic chlorine content of the oil in mgCl / L using the corresponding formula to obtain 1.90.

[0028] Example 3

[0029] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-ethanol solution with a volume ratio of 3:1, the solution containing 0.2 mol / L of sodium acetate and 53 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 15, and the pH of the extractant being 8.2.

[0030] 6.11 g of hydrogenated heavy oil was weighed into a 50 mL centrifuge tube with a cap, and 10 mL of xylene was added and mixed evenly; 12 mL of the extractant solution of the present invention was added, and the cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated, and the extract was transparent; the cap was loosened, an appropriate amount of the extract in the lower layer was extracted, and injected into the quantitative injection valve of the ion chromatograph, the application software was started, the inorganic chloride ion content was measured, and the inorganic chlorine content of the oil product expressed as 3.29 mgCl / L was finally calculated according to the corresponding formula.

[0031] Example 4

[0032] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-isopropanol solution with a volume ratio of 3:1, the solution containing 0.2 mol / L of sodium acetate and 53 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 20, and the pH of the extractant being 8.8.

[0033] 5.10 g of the raw wax oil was weighed into a 50 mL centrifuge tube with a cap, and 10 mL of xylene was added and mixed; 12 mL of the extractant solution of the present invention was added, and the cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated into layers, and the extract was transparent and clear; the cap was loosened, and an appropriate amount of the extract from the lower layer was extracted; 5 mL of the extract was taken and added to a titration cup, and the parameters and conditions were set according to the requirements of the GB / T 6532 method, and a potentiometric titrator was started to measure the chloride ion content. The inorganic chlorine content of the oil product expressed as mgNaCl / L was finally calculated according to the corresponding formula to be 12.7.

[0034] Example 5

[0035] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-isopropanol solution with a volume ratio of 3:1, the solution containing 0.05 mol / L of sodium acetate and 40 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 10, and the pH of the extractant being 9.0.

[0036] 4.90 g of catalytic raw oil was weighed into a 50 mL centrifuge tube with a cap, and 10 mL of xylene was added and mixed; 12 mL of the extractant solution of the present invention was added, and the cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated into layers, and the extract was transparent and clear; the cap was loosened, and an appropriate amount of the extract in the lower layer was extracted; 5 mL of the extract was taken and added to a titration cup, and the parameters and conditions were set according to the GB / T 6532 method requirements, and a potentiometric titrator was started to measure the chloride ion content. The inorganic chlorine content of the oil expressed as mgNaCl / L was finally calculated according to the corresponding formula.

[0037] Example 6

[0038] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-ethanol solution with a volume ratio of 3:1, the solution containing 0.15 mol / L of sodium acetate and 33 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 18, and the pH of the extractant being 8.0.

[0039] 5.00 g of three-line oil was weighed into a 50 mL centrifuge tube with a cap, and 10 mL of xylene was added and mixed evenly; 12 mL of the extractant solution of the present invention was added, and the cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated, and the extract was transparent and clear; the cap was loosened, and an appropriate amount of the extract in the lower layer was extracted; the extract was injected into the ion chromatograph injection valve, and the application software was started to measure the inorganic chloride ion content, and finally the inorganic chlorine 5.6 of the oil product expressed in mgNaCl / L was calculated according to the corresponding formula.

[0040] Example 7

[0041] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-ethanol solution with a volume ratio of 3:1, the solution containing 0.12 mol / L of sodium acetate and 40 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 18, and the pH of the extractant being 8.8.

[0042] 3.10 g of coking feedstock oil was weighed into a 25 mL centrifuge tube with a cap, and 6 mL of xylene was added and mixed; 8 mL of the extractant solution of the present invention was added, and the cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated, and the extract was transparent and clear; the cap was loosened, and an appropriate amount of the extract in the lower layer was extracted; the extract was injected into the ion chromatograph injection valve, and the application software was started to measure the inorganic chloride ion content, and finally the inorganic chlorine ion content of the oil product expressed in mgNaCl / L was calculated according to the corresponding formula. 10.3.

[0043] Example 8

[0044] An extractant for detecting inorganic chloride ions in oil products, the extractant comprising a water-isopropanol solution with a volume ratio of 3:1, the solution containing 0.08 mol / L of sodium acetate and 30 mg / L of polyoxyethylene fatty alcohol ether with a degree of polymerization of 12, and the pH of the extractant being 8.7.

[0045] 2.03 g of cracking raw oil was weighed into a 15 mL centrifuge tube with a cap, and 4 mL of xylene was added and mixed evenly; 6 mL of the extractant solution of the present invention was added, and the tube cap was tightened and sealed; after constant temperature shaking and centrifugation according to the steps of the SY / T 0536 standard method, the oil solution and the extract solution were separated, and the extract was transparent and clear; the tube cap was loosened, and an appropriate amount of the extract in the lower layer was extracted; the extract was injected into the ion chromatograph injection valve, and the application software was started to measure the inorganic chloride ion content, and finally the inorganic chlorine 1.1 of the oil product expressed in mgNaCl / L was calculated according to the corresponding formula.

[0046] The experimental platform of the present invention includes a 930 intelligent integrated ion chromatograph with a Metrosep A Supp 5-250 / 4.0 anion chromatography column, a 905 automatic potentiometric titrator, an 848 automatic sample changer, and a composite silver electrode (6.0450.100) filled with KNO3 (sat.), all manufactured by Metrohm, Switzerland. An LC-6Y microcoulometric (coulometric) inorganic chlorine analyzer was manufactured by Taizhou Jiangyan Analytical Instrument Factory. General laboratory reagents and materials were also used.

[0047] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. An extractant for detecting inorganic chloride ions in oil products, characterized by: The extractant includes solution A, L low-polymerization degree polyoxyethylene fatty alcohol ether, and strong base weak acid salt. The solution A is a mixture of water and ethanol or a mixture of water and isopropanol. The polymerization degree of the L low-polymerization degree polyoxyethylene fatty alcohol ether is 10-20.

2. The extractant for detecting inorganic chloride ions in oil products according to claim 1, characterized in that: The volume ratio of water to ethanol in the mixed liquid of water and ethanol is 3:

1.

3. The extractant for detecting inorganic chloride ions in oil products according to claim 1, characterized in that: The volume ratio of water to isopropyl alcohol in the mixed liquid of water and isopropyl alcohol is 3:

1.

4. The extractant for detecting inorganic chloride ions in oil products according to claim 1, characterized in that: The mass concentration of the L low-polymerization degree polyoxyethylene fatty alcohol ether is greater than or equal to 10 mg / L.

5. The extractant for detecting inorganic chloride ions in oil products according to claim 1, characterized in that: The strong base weak acid salt is sodium acetate, and the concentration of the strong base weak acid salt is 0.05-0.2 mol / L.

6. The extractant for detecting inorganic chloride ions in oil products according to claim 1, characterized in that: The pH value of the extractant is 8.5-9.

0.

7. The extractant for detecting inorganic chloride ions in oil products according to claim 6, characterized in that: The pH of the extractant is adjusted by acetic acid or sodium hydroxide.

8. A method for preparing an extractant for detecting inorganic chloride ions in oil products according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: weighing 4.1 g to 16.4 g of a strong base weak acid salt, adding no less than 0.5 mL of a L-low polymerization degree polyoxyethylene fatty alcohol ether stock solution, diluting the volume to 1 L with solution A, and adjusting the pH of the extractant to 8.5 to 9.0 with acetic acid or sodium hydroxide for later use.