Process for removing hydrogen sulfide from sour gases with ZIF-67 supported on mixed metal oxides

1. A method for removing hydrogen sulfide (H 2 S) from a H 2 S-containing gas composition, comprising:

charging an aqueous media to a reactor under continuous agitation;

dispersing particles of a composite in the aqueous media to form a composite mixture;

continuously agitating the composite mixture;

introducing the H 2 S-containing gas composition to the reactor containing the composite mixture under continuous agitation and passing the H 2 S-containing gas composition through the composite mixture; and

adsorbing and removing H 2 S from the gas composition by the composite mixture to form a purified gas composition,

wherein the composite comprises:

a CuMnAl mixed metal oxide (MMO); and

zeolitic imidazolate framework-67 (ZIF-67) nanoparticles,

wherein the ZIF-67 nanoparticles are dispersed between layers of the CuMnAl MMO, and

wherein the composite is made by a method comprising:

preparing a CuMnAl layered triple hydroxide (LTH);

calcining the CuMnAl LTH to form a CuMnAl MMO; and

mixing the CuMnAl MMO with precursors of the ZIF-67 to form the composite.

2. The method of claim 1 , wherein the CuMnAl MMO has a molar ratio of Cu to Mn to Al of 1-10 to 1-10 to 1-10.

3. The method of claim 1 , wherein the CuMnAl MMO has a molar ratio of Cu to Mn to Al of 1 to 2 to 1.

4. The method of claim 1 , wherein the composite comprises 30-70 wt. % of the CuMnAl MMO and 30-70 wt. % of the ZIF-67 nanoparticles, based on a total weight of the composite.

5. The method of claim 1 , wherein the ZIF-67 nanoparticles have an average size of 1-100 nm.

6. The method of claim 1 , wherein the ZIF-67 nanoparticles have a spherical shape.

7. The method of claim 1 , wherein the ZIF-67 nanoparticles are further dispersed on top of layers of the CuMnAl MMO.

8. The method of claim 1 , wherein the composite has a Langmuir specific surface area of 100-150 m 2 /g.

9. The method of claim 1 , wherein the composite has a BET specific surface area of 90-130 m 2 /g.

10. The method of claim 1 , wherein the composite has a specific pore volume of 0.05-0.2 m 3 /g.

11. The method of claim 1 , wherein the composite has a pore size of 20-25 nm.

12. The method of claim 1 , wherein the composite has a zeta potential of 10-30 mV at a pH of 4 to 9.

13. The method of claim 1 , wherein the gas composition further comprises at least one of methane, carbon dioxide, and nitrogen, and

wherein the composite selectively adsorbs the H 2 S.

14. The method of claim 1 , wherein the H 2 S is present in the gas composition at a concentration in a range of 10 to 200 parts per million by volume (ppmv) based on a total volume of the gas composition.

15. The method of claim 1 , wherein the H 2 S-containing gas composition is introduced to the reactor at a rate of 0.4 to 2.0 milliliters per minute (mL/min) per milligram of the composite.

16. The method of claim 1 , wherein the composite is present in the aqueous media at a concentration in a range of from 0.5 to 2 milligrams per milliliter (mg/mL).

17. The method of claim 1 , wherein the composite is present in the aqueous media at a concentration of 1 mg/mL,

wherein the composite is in contact with the gas composition comprising 100 ppmv of H 2 S at a rate of 80 mL/min in the stirred tank reactor,

wherein the composite has a breakthrough time of from 11-15 hours, and a saturation time of from 35-40 hours.

18. The method of claim 17 , wherein the composite has a saturation scavenging capacity 100-130 mg of hydrogen sulfide per gram of composite in the reactor.

19. The method of claim 1 , wherein the composite is supported on a support selected from the group consisting of carbon nanotubes, activated carbon, metal organic frameworks (MOFs), and other zeolitic imidazolate frameworks (ZIFs).