Method for detecting waste acid water content in industrialized alkylation reaction for preparing isooctane

Abstract

The application discloses a method for detecting the content of waste acid water in the industrialized alkylation reaction for preparing isooctane, which comprises the following steps: 1) taking 2g of imidazole, covering the surface of the imidazole with 2g of sodium chloride, and adding 1g of a waste acid sample solution; 2) adding 10ml of anhydrous methanol solution to the mixed solution, fully oscillating and dissolving, standing to take supernatant, and adopting Karl Fischer water titration method to determine the supernatant to obtain a test result w1; 3) repeating steps 1) to 2) to perform a blank experiment without adding waste acid, and obtaining a blank result w2; and 4) calculating the water content in the waste acid sample. The method avoids contacting pyridine in operation, improves the working environment, effectively protects the safety of operators, and simultaneously adopts sodium chloride for pre-reaction in the sample adding process, so that the to-be-detected sample does not need to be cooled by freezing, and the detection time is effectively shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical analysis, in particular to a method for detecting water content in waste acid in industrial alkylation reaction for preparing iso-octane. BACKGROUND

[0002] The existing method for industrial production of iso-octane is to produce high-octane alkylation oil in a reactor by using sulfuric acid as a catalyst and isobutane and light olefins as raw materials. Waste acid is continuously discharged during the alkylation reaction. By detecting the acid concentration, water content and acid-soluble oil in the waste acid, the quality of the waste acid in the reaction system in the reactor can be determined to effectively control the reaction process and reduce the proportion of side reactions.

[0003] The existing method for detecting water content in waste acid is to react excess pyridine with sulfuric acid at low temperature to neutralize sulfuric acid in the sample. A large amount of sulfate is formed in the solution system after the reaction, which is dissolved in methanol. Finally, the Karl-Fischer method is used to titrate to determine the water content in the obtained solution sample.

[0004] During the operation of the above method, a large amount of pyridine is needed to neutralize sulfuric acid. Pyridine has strong volatility, strong irritation and high toxicity, which affects the laboratory environment and harms the health of the operator. When pyridine contacts sulfuric acid, the reaction is violent and a large amount of heat is released. At this time, the valve of the reaction sample bottle must be opened to vent to air to avoid explosion caused by excessive pressure in the reaction sample bottle. However, during the venting process, hot gas will carry away part of the water in the sample, causing loss of water content in the sample.

[0005] At the same time, pyridine vapor mixed with the surrounding air forms an explosive mixture, which is dangerous. Therefore, the operation process of the above detection method requires high safety awareness of the experimenters, and any carelessness may cause an explosion.

[0006] At the same time, the method needs to freeze pyridine to -30℃ to normally perform the detection. In order to ensure the detection effect, the reaction needs to be carried out after cooling each time, which takes a long time to cool, resulting in a long detection time. SUMMARY

[0007] The present application provides a method for detecting water content in waste acid in industrial alkylation reaction for preparing iso-octane, which does not need to add pyridine reagent during the determination process, improves the safety of the detection operation, reduces the operation requirements for the experimenters, does not produce steam to carry away water in the sample, effectively improves the accuracy of the detection result, is simple to operate, has a short detection period, and is especially suitable for rapid detection of a large number of samples.

[0008] The present application provides a method for detecting water content in waste acid in industrial alkylation reaction for preparing iso-octane, which includes the following steps:

[0009] 1) Take 2 g of imidazole, cover the surface of the imidazole with 2 g of sodium chloride, after adding 1 g of waste acid sample solution, shake the mixture after heating to dissolve the imidazole, obtain the mixed solution, the mass of each substance is accurate to 0.1 mg, and the mass of the added imidazole m1, the mass of the added sodium chloride m2, and the mass of the added waste acid m4 are recorded;

[0010] 2) Add 10 ml of anhydrous methanol solution to the mixed solution, and after fully dissolving by shaking, stand to take the supernatant, and use Karl Fischer water titration method to determine the test result w1 of the supernatant, take and record the mass of the added anhydrous methanol solution m3, and the mass of each substance is accurate to 0.1 mg;

[0011] 3) Repeat steps 1-2) without adding waste acid to perform a blank test, and obtain a blank result w2;

[0012] 4) The water content in the waste acid sample is calculated according to the following formula:

[0013] X1=(m1+m2×a1+m3+m4)×(w1-w2) / m4

[0014] In the formula: X1 is the water content in the waste acid, unit is %; m1 is the mass of added imidazole, unit is g; m2 is the mass of added sodium chloride, unit is g; m3 is the mass of added methanol, unit is g; a1 is the solubility of sodium chloride in methanol, 0.02, unit is g / ml; w1 is the water content of the sample to be tested, unit is %; w2 is the water content of the blank test sample, unit is %; m4 is the mass of the waste acid sample, unit is g.

[0015] The determination method is as follows: in the reaction sample bottle, first add imidazole as the lower layer and sodium chloride as the upper layer as the neutralizing agent, and record the mass of the added imidazole and sodium chloride, then accurately weigh a certain amount of waste acid sample into the reaction sample bottle, after the waste acid and sodium chloride are preliminarily reacted, immediately seal the reaction sample bottle, and place the reaction sample bottle in an oven at 105℃, at which time the imidazole is dissolved to obtain an imidazole solution, which reacts with the remaining sulfuric acid and a small amount of hydrogen chloride gas in the reaction sample bottle, after the reaction is complete, a certain amount of methanol solution is added to dissolve the generated sulfate, finally a Karl Fischer water titrator is used to titrate the water content in the sample, and the water content of each reagent used is blank determined, the reagent water content in the measurement result is removed, and the water content in the sample can be calculated according to the formula. By laying sodium chloride on the upper layer of imidazole, the water overflow caused by too violent reaction can be prevented, and the detection result accuracy can be effectively improved.

[0016] The method has high accuracy, does not need to use toxic pyridine, improves detection safety, omits the pyridine freezing link, effectively shortens the detection time, and improves the detection efficiency.

[0017] (1)Imidazole does not generate water when it reacts with waste acid, effectively improving the accuracy of the test results.

[0018] (2) Since imidazole, like pyridine, releases a large amount of heat when it reacts with waste acid, the water in the sample is lost during the sample addition process. The solution to this technical problem is to react the sodium chloride in the upper layer of the reaction system with the waste acid before the imidazole reacts with the waste acid. This reaction does not release heat and does not generate additional water, and this process will not cause water loss in the sample.

[0019] (3) In a sealed environment, imidazole solution can react completely with the remaining acid in the reaction sample bottle, thereby avoiding the interference of acidic substances on the water content test results.

[0020] Preferably, to avoid water evaporation in high-temperature samples, causing test errors, the reaction sample bottle is sealed immediately after the waste acid reacts with sodium chloride in step 1).

[0021] Preferably, the heating operation in step 1) is to heat the resulting mixture at 105°C for 5 minutes, and after the heating is completed, the reaction sample bottle is shaken while hot to allow the acidic substances in the reaction sample bottle to react completely with imidazole.

[0022] Preferably, step 2) further includes the operation of cooling the reaction sample bottle to room temperature before adding methanol to reduce errors and improve the accuracy of the test results.

[0023] Preferably, in step 2), the sulfate is dissolved by shaking to improve the accuracy of the test results.

[0024] Preferably, the standing operation in step 2) is 3 minutes.

[0025] Preferably, in step 3), the mass of imidazole, the mass of sodium chloride, and the mass of anhydrous methanol taken in the blank experiment are close to the mass of imidazole m1, the mass of sodium chloride m2, and the mass of anhydrous methanol m3 in steps 1-2). By following this operation, the water content in each reagent can be accurately obtained, and the accuracy of the test results can be improved.

[0026] Specifically, the specific steps of the determination method are:

[0027] (1) In the reaction sample bottle, add 2g of imidazole, cover the surface of the imidazole with 2g of sodium chloride, and accurately weigh the imidazole and sodium chloride to 0.1mg, and record the mass m1 and m2 respectively.

[0028] (2) Accurately weigh 1g of waste acid to 0.1mg, record the mass m4, and immediately cover the sample cover.

[0029] (3) Put the reaction sample bottle into a 105℃ oven and heat for 5 minutes, and shake the reaction sample bottle while it is hot to make the acid in the reaction sample bottle fully react with the imidazole.

[0030] (4) Cool the reaction sample bottle in the third step to room temperature, add 10ml of anhydrous methanol solution, record the mass of the methanol as m3, shake the reaction sample bottle thoroughly to dissolve the sulfate salt in the reaction sample bottle.

[0031] (5) Let the reaction sample bottle in the above fourth step stand for 3 minutes, take the supernatant, and inject it into the Karl Fischer water titrator to obtain the test result w1

[0032] (6) Perform a blank test according to the above steps 1-5 to obtain the result w2 (when performing the blank test, the masses of m1, m2, and m3 should be as close as possible to those when testing the reaction sample bottle)

[0033] (7) Calculate X1 = (m1 + m2 x a1 + m3 + m4) x (w1 - w2) / m4

[0034] In the formula, X1 is the water content in the waste acid, in %; m1 is the mass of added imidazole, in g; m2 is the mass of added sodium chloride, in g; m3 is the mass of added methanol, in g; a1 is the solubility of sodium chloride in methanol, 0.02 g / ml; w1 is the water content of the sample to be tested, in %; w2 is the water content of the blank test sample, in %; and m4 is the mass of the waste acid sample, in g.

[0035] The beneficial effects that can be produced by the present application include:

[0036] 1) The industrialized alkylate reaction for producing isooctane waste acid water content detection method provided by the present application uses sodium chloride and imidazole instead of pyridine, imidazole does not generate water when reacting with waste acid, effectively improving the accuracy of the test results, and by reacting with sodium chloride in the upper layer of the reaction system before the waste acid reacts with imidazole, the reaction does not release heat and does not generate additional water, solving the problem of water loss in the sample due to high temperature during the sampling process. Imidazole solution can fully react with the remaining acid in the reaction sample bottle.

[0037] 2) The industrialized alkylate reaction for producing isooctane waste acid water content detection method provided by the present application avoids contact with pyridine during operation, improves the working environment, and effectively protects the safety of the operator. At the same time, this method uses sodium chloride for pre-reaction during the sampling process, eliminating the pyridine freezing step, effectively shortening the detection time. The method provided by the present application takes about 1.0 hours for the entire determination, which is half the time of the original method, improving the detection efficiency.

[0038] 3) The method for detecting the content of waste acid water in the industrial alkylation reaction for preparing isooctane provided by the application, the sample treated by the method is verified by adding standard recovery to pure water, the recovery rate of pure water is between 95.5% and 96.7%, the RSD of the method for detecting the same waste acid sample for multiple times is only 1.48%, which shows that the detection result of the method is accurate and has good reproducibility. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application.

[0040] The technical means not described in detail in the application and not used to solve the technical problems of the application are set according to the common knowledge in the art, and various common knowledge setting modes can be implemented.

[0041] EMBODIMENT

[0042] The materials and instruments used in the following embodiments are commercially available products unless otherwise specified.

[0043] The instruments and reagents used in the following embodiments are as follows:

[0044] Karl Fischer water titrator, drying oven, electronic balance (precision 0.0001 g), electronic constant temperature oscillator, imidazole (analytical pure), sodium chloride (analytical pure), reaction sample bottle (Agilent headspace bottle 20 ml; item number: 5182-0837), anhydrous methanol (analytical pure), Karl Fischer reagent 4 mg / L (volumetric method).

[0045] The method for obtaining the titer of Karl Fischer solution used when Karl Fischer method is used to measure in the following embodiments is as follows:

[0046] Calibration of Karl Fischer reagent: using pure water as a standard substance, calibration for four times in succession, and taking the average value as the titer of Karl Fischer solution, and the result is 3.9182 mg / L.

[0047] The sodium solubility test used in the following embodiments is as follows: 10 ml of methanol is taken into a reaction sample bottle, 0.025 g of pure water is added, the amount of pure water added is referred to the water content in the sample bottle during actual test, at this time, the water content in the methanol is about 0.3%, 2.0 g of sodium chloride is added, after sufficient oscillation, G4 sand core crucible is used for filtration, constant weight, and the measured sodium solubility a1 is 0.02 g / ml.

[0048] Example 1: Method for detecting the content of waste acid water in the industrial alkylation reaction for preparing isooctane

[0049] (1) In the reaction sample bottle, 2 g of imidazole is added, 2 g of sodium chloride is covered on the surface of the imidazole, the mass of the imidazole and sodium chloride is accurate to 0.1 mg, and each mass is recorded as m1 and m2.

[0050] (2) 1 g of waste acid solution is accurately weighed, accurate to 0.1 mg, the mass of the waste acid solution is recorded as m4, and the sample cover is immediately covered.

[0051] (3) The reaction sample bottle is placed in a 105°C oven and heated for 5 min, and the reaction sample bottle is shaken while hot to fully react the acidic substances in the reaction sample bottle with the imidazole.

[0052] (4) The reaction sample bottle in step 3) is cooled to room temperature, 10 ml of anhydrous methanol solution is added, the mass of the added methanol is recorded as m3, the reaction sample bottle is fully shaken, and the sulfate salt in the reaction sample bottle is dissolved.

[0053] (5) The reaction sample bottle in the above fourth step is left to stand for 3 min, the upper clear liquid is taken and injected into a Karl Fischer water titrator to obtain a test result w1;

[0054] (6) According to the above steps 1-5, only in step 2) no waste acid sample is added to perform a blank test, and a result w2 is obtained. (When performing the blank test, the masses of m1, m2, and m3 weighed above should be as close as possible to those when testing the reaction sample bottle.)

[0055] The parameters obtained in the above operations are substituted into: X1=(m1+m2×a1+m3+m4)×(w1-w2) / m4

[0056] In the formula: X1 is the water content in the waste acid, unit is %; m1 is the mass of added imidazole, unit is g; m2 is the mass of added sodium chloride, unit is g; m3 is the mass of added methanol, unit is g; a1 is the solubility of sodium chloride in methanol, unit is g / ml; w1 is the water content of the sample to be tested, unit is %; w2 is the water content of the blank test sample, unit is %; m4 is the mass of the waste acid sample, unit is g.

[0057] The waste acid generated in the production of isooctane by Rumes CDAlky technology is treated according to the above steps and detected, and the detection results are shown in Table 1.

[0058] Example 2 Reproducibility verification of the waste acid water content detection method in the industrial alkylation reaction for producing isooctane

[0059] 1. Preparation of the reaction sample bottle: 2 g of imidazole and 2 g of sodium chloride are weighed into the reaction sample bottle in turn.

[0060] 2. Precision test: according to the test steps, eight parallel experiments are respectively performed on the same waste acid sample, and the parameters and results of each parallel experiment are shown in Table 1.

[0061] Table 1

[0062]

[0063] From Table 1, the RSD of each detection result is only 1.48%, which indicates that the method has good repeatability.

[0064] Example 3: Spiked recovery test of the method for detecting the content of waste acid water in the industrial alkylation reaction for preparing isooctane

[0065] Five reaction sample bottles (one of which is blank) were prepared, 1 g of waste acid was quantitatively weighed (repeated 4 times) in the reaction sample bottles, 10 mg of pure water was added to each sample, and the water content in each sample was detected according to the steps in Example 1. The mass of each substance was accurately weighed to 0.1 mg.

[0066] The results are shown in Table 2, for example.

[0067] Table 2: Results of spiked recovery test

[0068]

[0069] From Table 2, the average spiked recovery rate of the water content in the waste acid sample detected by the method provided in the application is 96.4%, which indicates that the method has good reliability and accuracy.

[0070] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting the content of waste acid water in the industrialized alkylation reaction for producing isooctane, characterized in that, Comprising the following steps: (1) In the reaction sample bottle, add 2 g of imidazole, cover the surface of the imidazole with 2 g of sodium chloride, and record the mass of the imidazole and sodium chloride as m1 and m2, respectively, with the mass accurate to 0.1 mg; (2) Accurately weigh 1 g of the waste acid solution, accurate to 0.1 mg, record the mass of the waste acid solution as m4, and immediately cover the sample cover; (3) Place the reaction sample bottle in a 105℃ oven and heat for 5 min, then shake the reaction sample bottle while hot to fully react the acidic substances in the reaction sample bottle with the imidazole; (4) Cool the reaction sample bottle in step (3) to room temperature, add 10 ml of anhydrous methanol solution, record the mass of the added methanol as m3, and fully shake the reaction sample bottle to dissolve the sulfate salt in the reaction sample bottle; (5) Place the reaction sample bottle in step (4) for 3 min, take the upper clear liquid, and inject it into the Karl Fischer water titrator to obtain the test result w1; (6) Perform the blank test according to steps (1)-(5), except that no waste acid sample is added in step (2), and obtain the result w2. The masses m1, m2, and m3 obtained in the above operations should be as close as possible to those obtained when testing the reaction sample bottle; Substitute the parameters obtained in the above operations into: X1= (m1+m2×a1+m3+m4)×(w1- w2) / m4 In the formula: X1 is the water content in the waste acid, with the unit of %; m1 is the mass of imidazole added, with the unit of g; m2 is the mass of sodium chloride added, with the unit of g; m3 is the mass of methanol added, with the unit of g; a1 is the solubility of sodium chloride in methanol, with the unit of g / ml; w1 is the water content of the sample to be tested, with the unit of %; w2 is the water content of the blank test sample, with the unit of %; m4 is the mass of the waste acid sample, with the unit of g.

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