CN-117192026-B - Acid oxime ratio analysis method of solvent rearrangement reaction product in caprolactam production process

Abstract

The invention provides an acid oxime ratio analysis method of a solvent rearrangement reaction product in a caprolactam production process, which comprises the following steps of S1, detecting sulfuric acid content in the solvent rearrangement reaction product through potentiometric titration, S2, adding an extraction solvent to carry out mixed extraction with the solvent rearrangement reaction product, taking an extraction phase to measure inert organic solvent content in the extraction phase by adopting a gas chromatography, taking the water phase to measure inert organic solvent content in a water phase by adopting the gas chromatography, and S3, calculating the acid oxime ratio in the solvent rearrangement reaction product. According to the invention, the extraction solvent is adopted for extraction, the organic phase is extracted into the extraction solvent, then the content of the inert solvent in the extraction phase is tested, the interference of the inert solvent is eliminated in the acid oxime ratio analysis, the result is more accurate, the control of the effective conversion rate of rearrangement is facilitated, the rearrangement effect is accurately evaluated, the adjustment of the process working condition is facilitated, and the guiding basis is provided for production.

Inventors

• YIN YINHUA
• LI QINQIN
• CHEN ZHIXIA
• HE AIHUA
• XUE TING
• LI HUAN
• WANG ZHIYING

Assignees

• 湖北三宁化工股份有限公司

Dates

Publication Date

20260508

Application Date

20230724

Claims (5)

1. 1. An acid oxime ratio analysis method of a solvent rearrangement reaction product in a caprolactam production process is characterized in that the solvent rearrangement reaction product is obtained by dissolving cyclohexanone oxime in an inert organic solvent and carrying out Beckmann rearrangement reaction with fuming sulfuric acid, wherein the inert organic solvent is cyclohexane; The specific analysis method comprises the following steps: S1, detecting the sulfuric acid content H 2 SO 4 % in a solvent rearrangement reaction product by potentiometric titration; S2, adding an extraction organic solvent and water, carrying out mixed extraction with a solvent rearrangement reaction product, wherein the mixed extraction temperature is 40-60 ℃, taking an extraction phase, adopting a gas chromatography to measure the content of an inert organic solvent in the extraction phase, taking the water phase, adopting the gas chromatography to measure the content of the inert organic solvent in an aqueous phase, wherein the mass ratio of the extraction organic solvent to the water added during extraction is 1-3:10-15, the extraction organic solvent is n-butanol, and the mass ratio of a mixed solution of the extraction organic solvent and the water to the solvent rearrangement reaction product is 6:1-9:1; when the cyclohexane content was measured by gas chromatography, the chromatographic conditions were as follows: The temperature of the detector is 300 ℃, the temperature of a split non-split sample inlet is set to 300 ℃, the split ratio is 30:1, the nitrogen is 25mL/min, the hydrogen is 40mL/min, the air is 400mL/min, the flow rate of a chromatographic column is 1mL/min, and the temperature of a column box is raised to 240 ℃ by adopting a program; When the temperature is programmed, the initial temperature is 70 ℃ and kept for 5min, the temperature is raised to 150 ℃ in a 20 ℃/min step and kept for 3min, the temperature is raised to 220 ℃ for 9min in a 20 ℃/min step and kept for 3min in a 20 ℃/min step and kept for 240 ℃ in a 20 ℃/min step; s3, calculating an acid oxime ratio R in a solvent rearrangement reaction product, wherein the calculation formula is as follows: , , , 。
2. 2. The method of claim 1, wherein the sulfuric acid content is calculated by using a potentiometer and an aqueous phase pH electrode, a sodium hydroxide standard solution as a titrant, and a maximum jump point in the acid-base titration process as an end point when the potential is dropped in S1.
3. 3. The method of claim 2, wherein the concentration C NaOH of the sodium hydroxide standard solution is 0.5 to 1.0mol/L.
4. 4. The method according to claim 2, wherein the pH at the maximum jump point during the acid-base titration is 5.0.
5. 5. The method of claim 1, wherein the stirring speed is 400-600r/min and the stirring time is 10-15min in the process of mixing and extracting.

Description

Acid oxime ratio analysis method of solvent rearrangement reaction product in caprolactam production process Technical Field The invention belongs to the technical field of analysis, and particularly relates to an acid oxime ratio analysis method of a solvent rearrangement reaction product in a caprolactam production process. Background Caprolactam is one of important organic chemical raw materials, and is mainly used for producing polyamide slices through polymerization and further processing into nylon fibers, engineering plastics and plastic films. The main technological process of producing caprolactam includes hydrogenating benzene to produce cyclohexane, oxidizing cyclohexane to produce cyclohexanone, oximating cyclohexanone hydroxylamine to produce cyclohexanone oxime, beckmann rearrangement of cyclohexanone oxime to produce caprolactam, and refining to obtain caprolactam product. The Beckmann rearrangement of cyclohexanone oxime is one of the most important reactions in caprolactam production, and the quality of the reaction effect has direct influence on process control and caprolactam product quality. At present, the rearrangement effect is generally reflected by measuring the acid-oxime ratio and other data of the heavy liquid discharge, so as to adjust the process working condition. The existing rearrangement reaction technology is a rearrangement reaction of molten pure cyclohexanone oxime in the presence of fuming sulfuric acid, is a strong exothermic reaction, has high reaction speed and intense reaction, and can cause a large amount of impurities to influence the quality of a final product due to poor control of a process system. The Beckmann rearrangement reaction using a solvent can remove the reaction heat by vaporization of the solvent, and the rest of the reaction heat is taken away by a circulating water cooler. The solvent rearrangement reaction process is mild in reaction and stable in temperature control due to the existence of the solvent, so that quality fluctuation generated by local overheat reaction is avoided. In the solvent rearrangement reaction product, due to the existence of the solvent, only two substances of fuming sulfuric acid and caprolactam exist in reactants after rearrangement by default, caprolactam is a one-to-one product generated after cyclohexanone oxime rearrangement reaction, the ratio of the sulfuric acid to the caprolactam is calculated to obtain an acid oxime ratio, which can lead to a lower analysis result of the acid oxime ratio, in addition, the Beckmann rearrangement reaction is carried out under a strong acid condition, and the reacted material is a strong acid liquid material (hereinafter referred to as rearrangement liquid). The strong acidity corrodes the gas chromatography system, and the component analysis cannot be directly performed by gas chromatography. The accurate analysis data of the acid-oxime ratio of the re-liquid is particularly important for evaluating the rearrangement effect of the rearranged cyclohexanone oxime. Disclosure of Invention The invention provides an acid-oxime ratio analysis method of a solvent rearrangement reaction product in a caprolactam production process, which can accurately measure the acid-oxime ratio of heavy liquid discharge and provides a guiding basis for production. The technical scheme of the invention is that the acid oxime ratio analysis method of a solvent rearrangement reaction product in the caprolactam production process is obtained by dissolving cyclohexanone oxime in an inert solvent and carrying out Beckmann rearrangement reaction with fuming sulfuric acid, and the specific analysis method comprises the following steps: S1, detecting the sulfuric acid content H 2SO4% in a solvent rearrangement reaction product by potentiometric titration; S2, adding an extraction organic solvent and water, and carrying out mixed extraction with a solvent rearrangement reaction product, wherein the content of the inert organic solvent in the extraction phase is measured by adopting a gas chromatography; s3, calculating an acid oxime ratio R in a solvent rearrangement reaction product, wherein the calculation formula is as follows: m inert organic solvent for extraction phase ＝m Extract phase ×(100-H2 O%) x the inert organic solvent of the extract phase, M Aqueous inert organic solvent ＝m Aqueous phase ×(100-H2 O%) x aqueous phase inert organic solvent%. Further, the solvent rearrangement reaction product is obtained by dissolving cyclohexanone oxime in an inert solvent and carrying out Beckmann rearrangement reaction with fuming sulfuric acid. Further, the inert solvent is cyclohexane, n-heptane or n-octane. Further, when the potential is dropped in the S1, a potentiometer and an aqueous phase pH electrode are used, a sodium hydroxide standard solution is used as a titrant, and the maximum jump point in the acid-base titration process is used as an end point, so that the sulfuric acid content is calculated. Fu