阅读说明：本技术 一种采用卡尔费休容量法测定硫酸烷基化装置排出硫酸水含量的方法 (Method for measuring content of sulfuric acid water discharged from sulfuric acid alkylation device by adopting Karl Fischer volumetric method ) 是由 李国华 周茂森 于 2021-07-29 设计创作，主要内容包括：一种采用卡尔费休容量法测定硫酸烷基化装置排出硫酸水含量的方法,包括：(1)使硫酸烷基化装置排出硫酸样品酸烃分层,取下层酸样；(2)将密封好的两个玻璃瓶分别标明“空白”和“样品”,称重并记录玻璃瓶质量为M-(A)；向两个玻璃瓶中加入相同质量的吡啶,记录样品瓶质量为M-(B)；然后将两个玻璃瓶冷冻到冻结；在冻结的状态下,向样品瓶中加入酸样,然后让两个玻璃瓶在室温下自然解冻至液体状态,记录样品瓶质量为M-(C)；再向两个玻璃瓶加入相同质量的甲醇,记录样品瓶质量为M-(D)；将两个玻璃瓶震荡直到样品完全溶解；最后用卡尔费休水分仪测定空白瓶的水分,记作ω-(空白),测定样品瓶的水分,记作ω-(样品),代入公式求得酸样水含量,记作ω-(水),(A method for determining the content of sulfuric acid water discharged from a sulfuric acid alkylation device by adopting a Karl Fischer volumetric method comprises the following steps: (1) enabling sulfuric acid sample acid hydrocarbon discharged from a sulfuric acid alkylation device to be layered, and taking a lower-layer acid sample; (2) marking the two sealed glass bottles with blank and sample respectively, weighing and recording the mass of the glass bottle as M A (ii) a Adding pyridine with the same mass into two glass bottles, and recording the mass of the sample bottle as M B (ii) a Then freezing the two glass bottles until the two glass bottles are frozen; adding acid sample into the sample bottle in frozen state, naturally thawing the two glass bottles to liquid state at room temperature, and recording the mass of the sample bottle as M C (ii) a Adding methanol with the same mass into the two glass bottles, and recording the mass of the sample bottle as M D (ii) a Shaking the two glass bottles until the sample is completely dissolved; finally, the water content of the blank bottle is measured by a Karl Fischer moisture meter and is recorded as omega Blank space The water content of the sample bottle is measured and recorded as omega Sample (I) Substituting into formula to obtain water content of acid sample, and recording as omega Water (W) ，)

1. A method for measuring the content of sulfuric acid water discharged from a sulfuric acid alkylation device by adopting a Karl Fischer volumetric method comprises the following steps:

(1) pretreatment: fully standing a sulfuric acid sample discharged from a sulfuric acid alkylation device until acid hydrocarbon is layered, and taking a lower-layer acid sample;

(2) taking the acid sample obtained in the step (1) as an experimental object, taking a reagent blank as a contrast test, respectively marking a blank and a sample on two sealed glass bottles, weighing and recording the mass M of the glass bottles_A(ii) a Adding pyridine with the same mass into two glass bottles, weighing and recording the mass M of the sample bottle_B(ii) a Then freezing the two glass bottles until the two glass bottles are frozen; adding the acid sample obtained in the step (1) into a sample bottle in a frozen state, naturally thawing the two glass bottles to a liquid state at room temperature, wiping off water on the surfaces of the glass bottles, weighing and recording the mass M of the sample bottle_C(ii) a Methanol was then added to the two glass bottles, weighed and recordedSample bottle mass M_D(ii) a Placing the two glass bottles on a bottle shaking machine and shaking until the samples are completely dissolved; finally, the water content of the blank bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction), the water content of the sample bottle was measured and recorded as ω_{Sample (I)}(mass fraction) (%), and the acid-like water content was calculated by substituting the following equation, and the value was designated as ω_{Water (W)}(%, mass fraction),

the formula is:

wherein the volume ratio of the pyridine to the acid sample to the methanol is 15-20:5: 15-25.

2. The method of claim 1, wherein: the glass bottle is provided with a matched rubber plug, an aluminum plastic cover and an aluminum cover sealing device.

3. The method of claim 1, wherein: the titrant used in the determination process is commercial single-component Karl Fischer titration solution, and the solvent is mixed solution of methanol and imidazole in a volume ratio of 5:2-5: 3.

4. The method of claim 1, wherein: the titrant used in the determination process is commercial single-component Karl Fischer titration solution, and the solvent is mixed solution of methanol and imidazole in a volume ratio of 5: 2.

5. The method of any of claims 1-4, wherein: the volume ratio of the pyridine to the sulfuric acid sample to the methanol is 15-20:5: 20-25.

6. The method of claim 5, wherein: the volume ratio of pyridine to sulfuric acid sample to methanol was 15:5: 20.

(I) technical field

The invention relates to a method for measuring the content of sulfuric acid water discharged from an alkylation device by a sulfuric acid method.

(II) background of the invention

The alkylate oil is a high-octane gasoline blending component produced by an alkylation device, the main component is trimethylpentane, and isobutane and butylene generate under the action of a catalyst. The alkylate oil has the advantages of high octane number, good sensitivity, low vapor pressure, no olefin and aromatic hydrocarbon, clean combustion and the like. At present, the catalyst of the alkylation device in China is concentrated sulfuric acid. When sulfuric acid is used as a catalyst, its quality is critical. The presence of a certain amount of water facilitates the dissociation of concentrated sulfuric acid, thereby providing the hydrogen protons needed for the alkylation reaction. However, the water content cannot be increased at once, and the presence of water reduces the concentration of concentrated sulfuric acid on the one hand, and the increase in water content increases the corrosiveness of concentrated sulfuric acid on the other hand. Therefore, the water content of the sulfuric acid discharged from the reactor is one of the important indexes for achieving the process stability.

The Karl Fischer method is the most specific and accurate method for water in various chemical methods for measuring the moisture of substances, and is listed as a standard method for measuring the moisture in various substances. The Karl Fischer reaction is carried out under alkaline conditions, and if sulfuric acid is added directly, the pH of the solution is lowered, so that the reaction rate is lowered. Further, sulfuric acid promotes intermolecular dehydration reaction of the methanol solvent, making the measured value high.

Disclosure of the invention

The invention aims to provide a method for measuring the content of sulfuric acid water discharged from a sulfuric acid alkylation device by adopting a Karl Fischer volumetric method.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for measuring the content of sulfuric acid water discharged from a sulfuric acid alkylation device by adopting a Karl Fischer volumetric method comprises the following steps:

(1) pretreatment: fully standing a sulfuric acid sample discharged from a sulfuric acid alkylation device until acid hydrocarbon is layered, and taking a lower-layer acid sample;

(2) taking the acid sample obtained in the step (1) as an experimental object, taking a reagent blank as a contrast test, respectively marking a blank and a sample on two sealed glass bottles, weighing and recording the mass M of the glass bottles_A(ii) a Adding pyridine with the same mass into two glass bottles, weighing and recording the mass M of the sample bottle_B(ii) a Then freezing the two glass bottles until the two glass bottles are frozen; in the state of being frozen, the liquid is,adding the acid sample obtained in the step (1) into a sample bottle, naturally thawing the two glass bottles to a liquid state at room temperature, wiping off water on the surfaces of the glass bottles, weighing and recording the mass M of the sample bottle_C(ii) a The same mass of methanol was then added to both glass bottles, weighed and the sample bottle mass was recorded as M_D(ii) a Placing the two glass bottles on a bottle shaking machine and shaking until the samples are completely dissolved; finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction), the moisture of the "sample" bottle was measured and recorded as ω_{Sample (I)}(mass fraction) (%), and the acid-like water content was calculated by substituting the following equation, and the value was designated as ω_{Water (W)}(%, mass fraction),

the formula is:

wherein the volume ratio of the pyridine to the acid sample to the methanol is 15-20:5: 15-25.

Preferably, the glass bottle is a glass bottle provided with a matched rubber plug, an aluminum plastic cover and an aluminum cover sealing device.

The Karl Fischer moisture meter comprises: a common commercial volumetric method moisture meter, such as a Switzerland 915KF Ti-touch full-automatic moisture titrator. The titrant is common commercial single-component Karl Fischer titration liquid, the effective components are iodine, sulfur dioxide, pyridine and methanol, and the titre is 5 mg/ml. The solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5:2-5:3, preferably 5: 2.

Preferably, the volume ratio of pyridine to acid to methanol is 15-20:5:20-25, most preferably 15:5: 20.

The method has the technical effects that under the condition of measuring moisture by a conventional Karl Fischer method, the content of sulfuric acid water discharged from an alkylation device by a sulfuric acid method is measured by freezing pyridine and preparing methanol and imidazole solvents, accurate results are obtained by regulating and controlling the adding amount of the pyridine, the sulfuric acid and the methanol and the ratio of the methanol and the imidazole, and the accuracy of the test is improved by a reagent blank control test. In the experimental process, the used test instrument is simple and the related chemical reagents are common and easy to obtain. In the production process of the sulfuric acid alkylation device, the method has a great application prospect in the quality control of the catalyst concentrated sulfuric acid.

(IV) detailed description of the preferred embodiments

The invention is further illustrated with reference to the following specific examples, without limiting the scope of the invention thereto.

Example 1

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 10ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then using a disposable screw syringe and a matching screw needle to add 25ml of methanol to the two glass bottles (if the pressure in the bottles is too high, the air can be discharged by inserting a new syringe needle), weighing and recording the mass of the sample bottle as M_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 3. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). In the sample determination process, the Karl Fischer moisture meter has too long reaction time and is difficult to reach equilibrium.

Example 2

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 20ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then using a disposable screw syringe and a matching screw needle to add 25ml of methanol to the two glass bottles (if the pressure in the bottles is too high, the air can be discharged by inserting a new syringe needle), weighing and recording the mass of the sample bottle as M_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 3. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). The results are shown in Table 1 below:

TABLE 1

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results	73.1582	92.0205	100.5605	120.2209	0.244	0.855	3.37

Example 3

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass vials were labeled "blank" and "sample", respectively, andsealing the rubber plug with a matched rubber plug, an aluminum plastic cover and an aluminum cover sealing machine. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then using a disposable screw syringe and a matching screw needle to add 25ml of methanol to the two glass bottles (if the pressure in the bottles is too high, the air can be discharged by inserting a new syringe needle), weighing and recording the mass of the sample bottle as M_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 3. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). The results are shown in Table 2 below:

TABLE 2

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results	75.2041	90.7869	99.7994	119.6815	0.218	0.916	3.44

Example 4

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using disposable syringe with screw and matched screw needle to suck sulfuric acidAdding 5ml acid sample into the sample bottle in frozen state, naturally thawing the glass bottle to liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing, and recording the mass M of the sample bottle_C. Then using a disposable screw syringe and a matching screw needle to add 25ml of methanol to the two glass bottles (if the pressure in the bottles is too high, the air can be discharged by inserting a new syringe needle), weighing and recording the mass of the sample bottle as M_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 2. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). The results are given in Table 3 below:

TABLE 3

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results	80.1051	94.5390	102.7815	121.9273	0.221	0.862	3.25

Example 5

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then 20ml of methanol was added to the two glass bottles using a disposable screw-in syringe and a mating screw needle (if the pressure in the bottles was too great, venting was possible by inserting a new syringe needle), the sample bottles were weighed and the mass M of the sample bottles was recorded_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 3. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). The results are given in Table 4 below:

TABLE 4

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results	77.8451	92.9173	102.0523	118.5534	0.195	0.920	3.23

Example 6

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then 20ml of methanol was added to the two glass bottles using a disposable screw-in syringe and a mating screw needle (if the pressure in the bottles was too great, venting was possible by inserting a new syringe needle), the sample bottles were weighed and the mass M of the sample bottles was recorded_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, and the titrant is a common commercial single-component Karl Fischer titration solution (the effective components are iodine, sulfur dioxide, pyridine and methyl)Alcohol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 2. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). The results are given in Table 5 below:

TABLE 5

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results	79.2572	95.0854	104.4129	120.8745	0.189	0.905	3.19

Example 7

The sulfuric acid discharged from the sulfuric acid alkylation device is kept still for more than 20min to achieve acid hydrocarbon stratification. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle to absorb a lower-layer acid sample of a sulfuric acid sample, adding 5ml of the acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then 20ml of methanol was added to the two glass bottles using a disposable screw-in syringe and a mating screw needle (if the pressure in the bottles was too great, venting was possible by inserting a new syringe needle), the sample bottles were weighed and the mass M of the sample bottles was recorded_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 1. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction). In the sample determination process, the Karl Fischer moisture meter has too long reaction time and is difficult to reach equilibrium.

Example 8

Analytical pure sulfuric acid was used as an experimental sample for the determination of Karl Fischer moisture and the determination of sulfuric acid content. Two 60mL glass bottles were labeled "blank" and "sample" respectively and sealed with a mating rubber stopper, aluminum plastic cap and aluminum cap sealer. Weigh and record the sample bottle mass as M_A. Adding 15ml pyridine into two glass bottles by using a disposable syringe with a screw and a matched screw needle (if the pressure in the bottles is too high, air can be exhausted by inserting a new syringe needle), weighing and recording the mass M of the sample bottle_BThen both vials were frozen to freeze. Using a disposable syringe with a screw and a matched screw needle head to absorb and analyze pure sulfuric acid, adding 5ml of sulfuric acid sample into a sample bottle in a frozen state, naturally thawing the glass bottle to a liquid state at room temperature, wiping off water on the surface of the glass bottle, weighing and recording the mass M of the sample bottle_C. Then 20ml of methanol was added to the two glass bottles using a disposable screw-in syringe and a mating screw needle (if the pressure in the bottles was too great, venting was possible by inserting a new syringe needle), the sample bottles were weighed and the mass M of the sample bottles was recorded_D. Two glass bottles were placed on a shaker for more than 30 minutes with shaking until the sample was completely dissolved. Finally, the water content of the 'blank' bottle is measured by a Karl Fischer moisture meter and is recorded as omega_{Blank space}(%, mass fraction); the moisture content of the "sample" bottle was measured and recorded as omega_{Sample (I)}(%, mass fraction). The Karl Fischer moisture meter is a common commercial volumetric method moisture meter, the titrant is common commercial single-component Karl Fischer titration solution (effective components are iodine, sulfur dioxide, pyridine and methanol), the titer is 5mg/ml, the solvent is a mixed solution of methanol and imidazole, and the volume ratio is 5: 2. Substitution formulaThe water content of the sulfuric acid is determined and recorded as omega_{Water (W)}(%, mass fraction).

Meanwhile, the content of the sulfuric acid sample is determined by adopting the GB/T625-2007 standard and the accuracy of the method is verified. 2g of sample (exactly 0.0001g) was weighed into a stoppered light conical flask containing 50mL of water, cooled, 2 drops of methyl red indicator (1g/L) were added, and the solution was titrated with sodium hydroxide standard titration solution [ c (NaOH) ═ 1.0mol/L ] until the solution was yellow.

Mass fraction of sulfuric acid "omega_{Sulfuric acid}"numerical values are in"% "and are calculated according to formula (1):

in the formula:

v-number of volumes of standard titration solutions of sodium hydroxide in milliliters (mL);

c, standard value of the concentration of the sodium hydroxide standard titration solution, wherein the unit is mol per liter (mol/L);

m-number of molar masses of sulfuric acid, in grams per mole (g/mol)

m is the value of the mass of the sample in grams (g).

Tables 6 and 7 show the results of Karl Fischer moisture determination and sulfuric acid content determination based on GB/T625-2007 standard in two repeated experiments, respectively, wherein results 1 and 2 correspond to the results of the two repeated experiments, respectively.

TABLE 6

Item	MA	MB	MC	MD	ωBlank space	ωSample (I)	ωWater (W)
								Results 1	81.5273	96.8548	105.9133	122.7865	0.180	0.879	3.18
Results 2	83.1352	98.8456	108.3799	124.6672	0.180	0.888	3.08

[ Note ] results 1 and 2 use the same blank

TABLE 7

Item	m	c	V	ωSulfuric acid
					Results 1	2.1254	1.053	39.91	96.97
Results 2	2.2411	1.053	42.10	97.01