Method of producing fluorinated carbon from rice husk

Patent metadata

Field	Value
Publication number	US-11452986-B2
Application number	US-201916655914-A
Country	US
Kind code	B2
Filing date	Oct 17, 2019
Priority date	Oct 17, 2019
Publication date	Sep 27, 2022
Grant date	Sep 27, 2022

Abstract

A method for producing a fluorinated carbon adsorbent which involves digesting rice husk, sulfonating the digested rice husk, and fluorinating the sulfonated rice husk. The method yields a fluorinated carbon adsorbent material having an adsorption capacity for CO 2 of 1.6 to 2.5 mmol/g, an adsorption capacity for CH 4 of 0.4 to 0.8 mmol/g, and an adsorption capacity for N 2 of 0.1 to 0.4 mmol/g, at a temperature of 273 to 298 K and a pressure of 0.75 to 1.5 atm. Also disclosed is a method for separating a mixture of gases using the fluorinated carbon adsorbent.

First claim

The invention claimed is:

1. A method of making a fluorinated carbon adsorbent, the method comprising:
microwave irradiating a mixture of rice husk and aqueous sulfuric acid to a temperature of 100 to 300° C. to form a digested rice husk;
drying and milling the digested rice husk to form a powdered rice husk;
microwave irradiating the powdered rice husk in the presence of fuming sulfuric acid to form a sulfonated rice husk; and
microwave irradiating the sulfonated rice husk in the presence of hydrofluoric acid (HF) to a temperature of 50 to 150° C. thereby forming the fluorinated carbon adsorbent;
wherein the fluorinated carbon adsorbent has a carbon content of 60 to 75 wt %, an oxygen content of 14 to 34.5 wt %, a fluorine content of 5 to 9 wt %, a sulfur content of 0.5 to 2 wt %, and a silicon content of less than 0.5 wt %, each relative to a total weight of the fluorinated carbon adsorbent.

2. The method of claim 1 , wherein the aqueous sulfuric acid has a concentration of 1 to 4.2 M.

3. The method of claim 1 , wherein the mixture is microwave irradiated for 1 to 60 minutes.

4. The method of claim 1 , wherein the digested rice husk is dried at 30 to 90° C. for 1 to 24 hours.

5. The method of claim 1 , wherein the powdered rice husk is microwave irradiated for 1 to 60 minutes.

6. The method of claim 1 , wherein the sulfonated rice husk is microwave irradiated for 15 to 90 minutes.

7. The method of claim 1 , further comprising washing the fluorinated carbon adsorbent with distilled water and drying at 50 to 150° C. after forming.

8. The method of claim 1 , wherein the fluorinated carbon adsorbent has a surface area of 500 to 600 m 2 /g, a pore volume of 0.1 to 0.3 cm 3 /g, and a mean pore radius of 0.5 to 0.75 nm.

9. The method of claim 1 , wherein the fluorinated carbon adsorbent has an adsorption capacity for CO 2 of 1.6 to 2.5 mmol/g, an adsorption capacity for CH 4 of 0.4 to 0.8 mmol/g, and an adsorption capacity for N 2 of 0.1 to 0.4 mmol/g, at a temperature of 273 to 298 K and a pressure of 0.75 to 1.5 atm.

10. The method of claim 1 , wherein the fluorinated carbon adsorbent has a separation factor for CO 2 /CH 4 of 2 to 6 and a separation factor for CO 2 /N 2 of 6 to 16.

11. The method of claim 1 , wherein the fluorinated carbon adsorbent has reversible gas adsorption and is returned to a state with no adsorbed gas by exposure to a pressure of 0.0001 to 0.1 atm.

12. A fluorinated carbon adsorbent obtained by fluorinating a sulfonated rice husk, wherein the fluorinated carbon adsorbent has a surface area of 500 to 600 m 2 /g, a pore volume of 0.1 to 0.3 cm 3 /g, and a mean pore radius of 0.5 to 0.75 nm.

13. The fluorinated carbon adsorbent of claim 12 , which has a carbon content of 60 to 75 wt %, an oxygen content of 14 to 34.5 wt %, a fluorine content of 5 to 9 wt %, and a sulfur content of 0.5 to 2 wt %, and a silicon content of less than 0.5 wt %, each relative to a total weight of the fluorinated carbon adsorbent.

14. The fluorinated carbon adsorbent of claim 12 , which has an adsorption capacity for CO 2 of 1.6 to 2.5 mmol/g, an adsorption capacity for CH 4 of 0.4 to 0.8 mmol/g, and an adsorption capacity for N 2 of 0.1 to 0.4 mmol/g, at a temperature of 273 to 298 K and a pressure of 0.75 to 1.5 atm.

15. The fluorinated carbon adsorbent of claim 12 , which has a separation factor for CO 2 /CH 4 of 2 to 6 and a separation factor for CO 2 /N 2 of 6 to 16.

16. The fluorinated carbon adsorbent of claim 12 , which has reversible gas adsorption and is returned to a state with no adsorbed gas by exposure to a pressure of 0.0001 to 0.1 atm.

17. A method of separating a first gas from a gas mixture comprising the first gas and a second gas, the method comprising:
delivering the gas mixture into a feed side of a chamber comprising the fluorinated carbon adsorbent of claim 12 that divides the chamber into the feed side and a permeate side, such that at least a portion of the first gas permeates the fluorinated carbon adsorbent; and
recovering from the permeate side a stream depleted in the first gas compared to the gas mixture.

18. The method of claim 17 , wherein the first gas is CO 2 and the second gas is N 2 , CH 4 , or both.

19. The method of claim 17 , wherein the gas mixture and the chamber have a temperature of 223 to 348 K and the gas mixture is supplied to the feed side of the chamber at a pressure of 0.75 to 2 atm.

20. The method of claim 18 , which has a separation factor for CO 2 /CH 4 of 2 to 6 and a separation factor for CO 2 /N 2 of 6 to 16.

Assignees

• Univ King Fahd Pet & Minerals

Inventors

• Basheer Chanbasha
• Aljundi Isam H
• Bakdash Rashed Saed

Classifications

• B01J20/3078

  Thermal treatment, e.g. calcining or pyrolizing · CPC title

• B01D2253/304

  Linear dimensions, e.g. particle shape, diameter · CPC title

• B01D2253/102

  Carbon · CPC title

• B01D2253/311

  Porosity, e.g. pore volume · CPC title

• B01J20/28061

  being in the range 100-500 m2/g · CPC title