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CN-118079855-B - VOCs adsorption material and preparation method thereof

CN118079855BCN 118079855 BCN118079855 BCN 118079855BCN-118079855-B

Abstract

The invention relates to a VOCs adsorption material and a preparation method thereof, wherein a lithium modified 5A molecular sieve is adopted, and then a Li-Ti-5A adsorption material is obtained through titanium modification, wherein the content of Li is 0.65% -4.2% and the content of Ti is 0.15% -0.85% by weight of the total mass of the adsorption material. The adsorption material prepared by the method of the invention takes the 5A molecular sieve as a matrix, and the Li-Ti-5A adsorption material obtained by modification has the advantages of good adsorption effect of low-carbon hydrocarbon, good thermal stability and the like, and particularly has better adsorption effect on propane.

Inventors

  • WANG PENG
  • LIU SIJIA
  • WANG XUEHAI
  • ZHAO LEI

Assignees

  • 中国石油化工股份有限公司
  • 中石化（大连）石油化工研究院有限公司

Dates

Publication Date
20260505
Application Date
20221118

Claims (20)

  1. 1. The adsorption material for adsorbing and separating low-carbon hydrocarbon in VOCs is characterized in that a lithium modified 5A molecular sieve is adopted, and then a Li-Ti-5A adsorption material is obtained through titanium modification, wherein the content of Li is 0.65% -4.2% and the content of Ti is 0.15% -0.85% based on the total mass of the adsorption material, micropores in the adsorption material account for more than 80%, and the sum of volumes of pores with pore diameters distributed between 4-6A is more than 65% of the total pore volume; The preparation method of the adsorbing material comprises the following steps of (1) immersing a 5A molecular sieve in a lithium salt solution for treatment at a temperature of 60-90 ℃, taking out, washing, drying and roasting to obtain a Li-5A molecular sieve, and (2) immersing the Li-5A molecular sieve in a titanium salt solution for treatment, taking out, washing, drying and roasting to obtain the Li-Ti-5A adsorbing material.
  2. 2. The adsorbent material of claim 1, wherein the Li-Ti-5A adsorbent material has a specific surface area of 480 to 540m 2 /g and a pore volume of 0.26 to 0.3cm 3 /g.
  3. 3. The adsorbent material according to claim 1, wherein the 5A molecular sieve in the step (1) has a specific surface area of 400-550 m 2 /g, a pore volume of 0.2-0.5 cm 3 /g, an average pore diameter of 1-3 nm, and an average particle diameter of 1-3 mm.
  4. 4. The adsorbent material according to claim 3, wherein the specific surface area of the 5A molecular sieve in the step (1) is 500-550 m 2 /g and the pore volume is 0.28-0.35 cm 3 /g.
  5. 5. The absorbent material of claim 1, wherein the lithium salt solution in step (1) is at least one of LiCl solution, lithium nitrate solution, and lithium sulfate solution.
  6. 6. The absorbent material of claim 5, wherein the lithium salt solution in step (1) is LiCl solution.
  7. 7. The absorbent material according to claim 1, 5 or 6, wherein the concentration of the lithium salt solution in the step (1) is 0.25 to 1.8mol/L.
  8. 8. The absorbent material according to claim 7, wherein the concentration of the lithium salt solution in the step (1) is 0.4 to 1.25mol/L.
  9. 9. The adsorption material according to claim 1, 5 or 6, wherein the mass-to-volume ratio of the 5A molecular sieve to the lithium salt solution in the step (1) is 1 g:3-10 mL.
  10. 10. The adsorption material according to claim 1, wherein the 5A molecular sieve in the step (1) is immersed in a lithium salt solution for 1-5 hours at a temperature of 70-80 ℃.
  11. 11. The adsorption material according to claim 1, wherein deionized water is used for washing in the step (1) until no lithium ions are detected, the drying condition is that the drying temperature is 70-120 ℃, the drying time is 2-10 h, and the roasting condition is that the roasting temperature is 450-600 ℃ and the roasting time is 1-10 h.
  12. 12. The adsorbent material of claim 11, wherein the drying temperature is 80-100 ℃, the drying time is 2-5 hours, the roasting temperature is 500-550 ℃, and the roasting time is 2-6 hours.
  13. 13. The absorbent material of claim 1, wherein the titanium salt in step (2) is a soluble titanium salt.
  14. 14. The adsorbing material according to claim 13, wherein the titanium salt in the step (2) is at least one of titanium tetrachloride, titanyl sulfate and titanium oxalate.
  15. 15. The method according to claim 14, wherein the titanium salt in the step (2) is titanium tetrachloride.
  16. 16. The absorbent material according to claim 1 or 13, wherein the titanium content in the titanium salt solution in the step (2) is 0.03 to 0.4mol/L.
  17. 17. The adsorption material according to claim 16, wherein the titanium content in the titanium salt solution in the step (2) is 0.15-0.25 mol/L.
  18. 18. The adsorption material according to claim 1 or 13, wherein the mass-to-volume ratio of the Li-5A molecular sieve to the titanium salt solution in the step (2) is 1 g:10-20 mL.
  19. 19. The adsorption material according to claim 1, wherein in the step (2), the Li-5A molecular sieve is immersed in a titanium salt solution at room temperature for 1-5 hours.
  20. 20. The adsorption material according to claim 19, wherein in the step (2), the Li-5A molecular sieve is immersed in a titanium salt solution at 15-30 ℃ for 1-2 hours.

Description

VOCs adsorption material and preparation method thereof Technical Field The invention belongs to the technical field of air pollution control, and particularly relates to a VOCs adsorption material and a preparation method thereof. Background Volatile Organic Compounds (VOCs) are one of the main atmospheric pollutants, are one of important reactants participating in the generation of photochemical smog and haze, and the excessive amount of the VOCs brings serious harm to human health and ecological environment. Among VOCs discharged in the chemical industry, ethane and propane are VOCs molecules with smaller sizes, have weaker polarity and are often difficult to remove. The VOCs adsorption separation technology is suitable for low-concentration VOCs waste gas treatment, and the key of adsorption purification efficiency is an adsorption material. The adsorption material has high specific surface area and proper pore structure, and can retain VOCs pollutant through chemical adsorption or physical adsorption, thus realizing waste gas purification. The types of VOCs are complex, wherein the higher the molecular weight is, the stronger the polarity is, the easier the VOCs are adsorbed, and the lower hydrocarbon, especially ethane and propane, are VOCs with smaller size, the weaker the polarity is, the conventional adsorption material is difficult to realize efficient adsorption. CN201410207034.8 discloses an activated carbon propane adsorbent, a preparation method and application thereof, wherein coconut shell activated carbon is soaked in hydrofluoric acid solution with the concentration of 5-22mol/L, the coconut shell activated carbon is placed in a hydrothermal reaction kettle, and is subjected to hydrothermal treatment at 120-180 ℃ for 1-7 days, and the activated carbon propane adsorbent is obtained after washing and drying. The purifying material has higher purifying efficiency on low-concentration hydrocarbon, and the highest purifying efficiency of the material at normal temperature and normal pressure can reach more than 99 percent under the conditions that the concentration of propane is 20ppm and the airspeed is 50000 mL/(g.h). However, the adsorption capacity of the material only reaches 2.0ml of C 3H8/gAC, the adsorption capacity is required to be improved, and the temperature rise in the adsorption process of the carbon material is at risk, so that the safety utilization is not facilitated. In the multi-type molecular sieve, the effective aperture of the 5A molecular sieve in the LTA structure is about 0.51nm, the kinetic diameter of ethane is 0.4nm, the kinetic diameter of propane is about 0.43nm, and the pore channel window size of the molecular sieve accords with the kinetic screening of ethane and propane molecules, so that the molecular sieve can effectively adsorb ethane and propane molecules into the pore channel. In addition, the 5A molecular sieve synthesized by the traditional method only has a micropore canal structure, and the slow molecular diffusion rate and the long molecular diffusion path in micropores lead to low utilization rate of activity in the molecular sieve crystal, greatly limit the rate of the adsorption/desorption process and limit the adsorption capacity. For small-molecular alkanes such as ethane and propane in VOCs, the adsorption effect is limited to the effect of Van der Waals force to a large extent due to the weak polarity, the acting force is weak, and the adsorption effect is poor. CN202210619764.3 discloses a preparation method of modified 5A molecular sieve, comprising 1) fully contacting 5A molecular sieve with sucrose water solution under ultrasonic condition, then drying and roasting under inert gas atmosphere, 2) treating the material obtained in step 1) with glycol water solution, filtering and drying, 3) thermally activating the material obtained in step 2) with high temperature water to obtain modified 5A molecular sieve. The modified material not only has high adsorption capacity, but also has excellent adsorption and separation effects on the kerosene-diesel fraction n-isoparaffin, and the modified material is suitable for adsorption of n-hexane and the like due to the characteristics, so that the selective adsorption effect on lower hydrocarbons below C4 is poor. CN201310516673.8 discloses a 5A molecular sieve adsorbent and its preparation method, the method comprises rolling ball forming of powder containing 4A molecular sieve and binder source, drying, roasting to obtain matrix pellets, prewetting the matrix pellets, and then carrying out crystal transformation, calcium exchange, drying and roasting to make the prepared 5A molecular sieve adsorbent have advantages of large adsorption capacity of normal alkane (such as n-hexane), high adsorption efficiency, good strength, etc. However, the adsorption material has characteristics such that it is suitable for adsorption of normal hexane, and therefore, the adsorption effect on lower hydrocarbons having