Search

CN-121988279-A - Preparation method of metal modified molecular sieve and application of metal modified molecular sieve in pressure swing adsorption purification of n-hexane

CN121988279ACN 121988279 ACN121988279 ACN 121988279ACN-121988279-A

Abstract

The invention provides a preparation method of a metal modified molecular sieve and application of the metal modified molecular sieve in pressure swing adsorption purification of n-hexane. The preparation method of the adsorption material comprises the steps of carrying out ion exchange reaction on the molecular sieve and the metal salt aqueous solution at a second preset temperature for a second preset time to obtain a metal modified molecular sieve suspension, and carrying out filtration, washing and drying treatment on the suspension to obtain the metal modified molecular sieve. According to the invention, a certain amount of metal ions are introduced into the molecular sieve framework, so that the modified molecular sieve forms a micro-mesoporous composite pore system. The structural optimization obviously improves the adsorption rate and the diffusion performance of the molecular sieve on the n-hexane, and obviously improves the separation efficiency. In the pressure swing adsorption purification process, the metal modified molecular sieve can realize high-selectivity adsorption and rapid diffusion of the n-hexane, and simultaneously can effectively remove trace or high-concentration isoparaffin in the n-hexane, thereby remarkably improving the purification efficiency of the n-hexane.

Inventors

  • XIAO JING
  • HU LEI
  • MIAO GUANG
  • WU ZHIKANG
  • LI XINXIN
  • CHEN SHIBIN
  • ZHOU XIAOYING

Assignees

  • 华南理工大学

Dates

Publication Date
20260508
Application Date
20260206

Claims (10)

  1. 1. The preparation method of the metal modified molecular sieve for n-hexane adsorption purification is characterized by comprising the following steps of: (1) Adding metal salt into the aqueous solution, and stirring for a first preset time at a first preset temperature to obtain a metal salt aqueous solution; (2) Adding 5A molecular sieve powder into a metal salt aqueous solution, stirring for a second preset time at a second preset temperature, and reacting to obtain a suspension; (3) Filtering, washing and drying the suspension to obtain the metal modified 5A molecular sieve.
  2. 2. The method according to claim 1, wherein in the step (1), the metal ion in the metal salt is one of Zn 2+ 、Co 2+ 、Ni 2+ 、Mn 2+ 、Mg 2+ 、Cu 2+ 、Sr 2+ 、Li + .
  3. 3. The process according to claim 1, wherein in step (1), The metal salt is one of nitrate, chloride, sulfate or acetate; the concentration of the metal salt aqueous solution is 0.005-1.0 mol/L; the first preset temperature is 20-50 ℃, and the first preset time is 5-60 minutes.
  4. 4. The process according to claim 1, wherein in step (2), The dosage of the 5A molecular sieve powder is 0.001-0.1 g/mL, namely 0.001-0.1 g of 5A molecular sieve powder is added into each mL of metal salt aqueous solution; the second preset temperature is 25-90 ℃, and the second preset time is 3-24 hours.
  5. 5. The method of claim 1, wherein in step (3), the drying operation comprises: And heating the filtered product to 95-105 ℃ at the speed of 2 ℃ per minute, keeping the temperature for 2 hours, heating to 190-210 ℃ at the speed of 2 ℃ per minute, keeping the temperature for 5 hours, and cooling to 20-40 ℃ at the speed of 5 ℃ per minute.
  6. 6. A metal modified molecular sieve obtainable by the process of any one of claims 1 to 5.
  7. 7. The use of the metal modified molecular sieve prepared by the preparation method of any one of claims 1 to 5 in pressure swing adsorption purification of n-hexane.
  8. 8. The use according to claim 7, wherein the adsorption temperature is 25-250 ℃.
  9. 9. The use according to claim 7, wherein the pressure swing adsorption unit consists of two fixed bed adsorption columns loaded with adsorbent, is a double column pressure swing adsorption process, comprising the steps of: (1) The hydrocarbon mixture raw material containing n-hexane continuously enters a fixed bed adsorption tower 1 loaded with an adsorbent at a certain feeding flow rate after being vaporized in a vaporization chamber, and n-hexane in the raw material is adsorbed by the adsorbent, and the other components are accumulated in a gas phase; (2) After the adsorption process of the adsorption tower 1 is finished, opening a valve at the top of the tower, and sweeping a fixed bed by using a feed gas flow to discharge gas-phase impurities accumulated in the previous step from the top of the tower, and simultaneously, further desorbing the gas-phase impurities by the adsorption tower 2 to obtain n-hexane from the bottom of the tower, wherein the n-hexane can be used as a high-purity n-hexane product; (3) After the adsorption tower 1 finishes the flushing process, the adsorption tower 1 and the adsorption tower 2 which finishes the desorption process are subjected to pressure equalizing, so that the adsorption tower 1 finishes the pre-depressurization, and the adsorption tower 2 finishes the pre-pressurization; (4) Simultaneously, the raw material of the hydrocarbon mixture containing the n-hexane continuously enters a fixed bed adsorption tower 2 loaded with an adsorbent at a certain feeding flow rate after being vaporized in a vaporization chamber, the n-hexane in the raw material is adsorbed by the adsorbent, and the rest components are accumulated in a gas phase; (5) Simultaneously, after the adsorption process of the adsorption tower 2 is completed, a valve at the top of the tower is opened, a fixed bed is purged by using a feeding airflow, and gas phase impurities accumulated in the previous step are discharged from the top of the tower; (6) The adsorption tower 1 which completes the desorption process and the adsorption tower 2 which completes the flushing process are subjected to pressure equalizing, so that the adsorption tower 1 completes the pre-pressurizing, the adsorption tower 2 completes the pre-depressurization, and thus, one pressure swing adsorption cycle process is completed, and the next pressure swing adsorption cycle process is ready to enter.
  10. 10. The use according to claim 9, wherein the n-hexane in the n-hexane-containing hydrocarbon mixture feedstock has a purity of 80% to 99%; The feeding flow rate is 0.05-10L/min/kg; the vaporization temperature of the vaporization chamber is 100-250 ℃, the temperature of the adsorption tower is 100-250 ℃, the absolute pressure of the adsorption process is 100-300 kPa, and the absolute pressure of the desorption process is 0.05-100 kPa; The adsorption time is 10-3600 s, the flushing time is 5-180 s, the pressure equalizing time is 5-600 s, and the desorption time is 10-3600 s; finally, the purity of the high-purity n-hexane is up to more than 99.9%.

Description

Preparation method of metal modified molecular sieve and application of metal modified molecular sieve in pressure swing adsorption purification of n-hexane Technical Field The invention belongs to the field of gas adsorption separation materials, and particularly relates to a preparation method of a metal modified molecular sieve and application of the metal modified molecular sieve in pressure swing adsorption purification of n-hexane. Background N-hexane (n-hexane) is an important chemical raw material and solvent, and has the characteristics of no color, transparency, non-polarity, high combustibility and the like. The application field of n-hexane varies depending on the purity. The n-hexane with medium and low purity is mainly used in the fields of vegetable oil extraction, daily chemical production, rubber synthesis and the like, and the n-hexane with high purity is widely used for synthesizing chemical reagents and medical intermediates. The n-hexane with ultra-high purity (99.99%) is also called electronic grade n-hexane, is often used as a cleaning agent in the electronic information industry, and can effectively remove organic impurities and particle pollution on the surfaces of precision devices such as semiconductor chips, electronic components, printed circuit boards, optical components and the like, thereby ensuring the accuracy of device test results and improving the stability and the yield in the production process of products. With the rapid development of informatization and semiconductor industry in China, the market demand of wet electronic chemicals is continuously increased, and the contradiction between supply and demand of electronic grade high-purity hexane is increasingly prominent. At present, the main method for industrially producing the normal hexane is that crude normal hexane is firstly obtained from reformed raffinate oil or straight-run naphtha by rectification and refining, and then the high-purity normal hexane is obtained by precision rectification, extractive rectification or molecular sieve adsorption and other methods. However, in this production process, various hexane isomer impurities such as 3-methylpentane, 2-dimethylbutane, methylcyclopentane, etc. are often formed concomitantly. These isomer impurities are very close to n-hexane in physical properties such as molecular size, polarizability and boiling point, making it difficult to achieve efficient separation by conventional rectification methods, resulting in limited product purity of n-hexane. The patent CN107586250B uses naphtha adsorption separation oil as raw material, and adopts four-tower sequential continuous rectification process to obtain n-hexane product with purity of >99% and recovery rate of >80% and n-heptane product with purity of >99% and recovery rate of > 78%. Although the purity can be improved by adopting a precise rectification or special rectification process, the defects of complex production flow, high cost, low yield, high energy consumption and the like still exist. In contrast, adsorption separation technology has the advantages of low energy consumption, simple operation, high product purity and the like, and is a hot spot for research in recent years. Patent CN104744196B proposes that potassium permanganate or peroxide is added into n-hexane as raw material for oxidation treatment, and then modified activated carbon is used for adsorption, so that high-purity hexane with purity more than or equal to 99% (wt) can be obtained. The patent CN101544531B takes n-hexane with the content of 95 percent as a raw material, utilizes a zeolite adsorbent to adsorb and remove impurities with the boiling point close to that of the n-hexane, and then obtains a chromatographic grade n-hexane product with the purity of more than or equal to 98 percent, the yield of more than or equal to 93 percent and the qualification rate of 92 percent through the rectification and purification of a molecular sieve drying agent. The patent CN 118373724B adopts analytical grade sulfuric acid to remove impurities in industrial grade normal hexane, and combines a steam modified molecular sieve and long wave ultraviolet light modified activated carbon adsorption treatment to realize the preparation of chromatographic grade high purity hexane with purity not less than 99.99 percent. The patent CN101148390B adopts optimized process conditions through a four-tower heating pressure swing adsorption process, and n-hexane products with the content of 95.0% -99.9% (wt) can be obtained through separation. Patent CN110898612a provides a two-stage PSA separation system, using macroporous modified faujasite and 5A or MFI molecular sieve as adsorbents, respectively, to separate n-hexane, methylcyclopentane, and cyclohexane with purity higher than 99.0% from C6 hydrocarbon mixtures of different sources. However, although the purification of n-hexane is realized by methods such as oxidation refining, modified activated carbon or m