Process for the removal of heavy metals from gases
View Patent ↗A composition, containing vanadium and a support, wherein at least a portion of the vanadium has crystallite sizes of less than about 100 Å as determined by an analytical method such as X-Ray Diffraction, is disclosed. A method of preparing such composition is also disclosed. The composition is employed in a process to remove a heavy metal from a gaseous feed stream which can optionally include a separate mercury adsorption stage.
1. A process comprising:
a) contacting, in a contacting zone, a gaseous feed stream comprising a heavy metal and oxygen with a composition prepared by the method of:
a) incorporating a vanadium compound onto, into, or onto and into a support selected from the group consisting of: 1) amorphous silica-alumina; 2) a zeolite; 3) a material comprising meta-kaolin, alumina, and expanded perlite; 4) alumina; and 5) combinations thereof, in the presence of an oxidizing agent and a solvent, to thereby form a vanadium incorporated support; and
b) calcining said vanadium incorporated support at a calcination temperature; wherein said calcination temperature is sufficient to volatilize and remove substantially all of the solvent; and wherein said calcination temperature is below the temperature which would result in the conversion of greater than about 90 weight percent of the vanadium to vanadium-and-oxygen-containing crystallites greater than about 100 Å in size, to thereby form said composition; and
b) withdrawing a gaseous product stream from said contacting zone.
2. A process as recited in claim 1 wherein said gaseous product stream contains less heavy metal than said gaseous feed stream.
3. A process as recited in claim 1 wherein said gaseous feed stream further comprises a compound selected from the group consisting of sulfur oxides, CO 2 , water, nitrogen oxides, HCl, and combinations of any two or more thereof.
4. A process as recited in claim 1 wherein said gaseous feed stream is a combustion gas.
5. A process as recited in claim 1 wherein said gaseous feed stream is a stack gas derived from the combustion of coal.
6. A process as recited in claim 1 wherein said contacting of step a) is carried out at a temperature in the range of from about 100 to about 275° C.
7. A process as recited in claim 1 wherein said contacting of step a) is carried out at a temperature in the range of from about 125 to about 225° C.
8. A process as recited in claim 1 wherein said heavy metal comprises a metal selected from the group consisting of arsenic, beryllium, lead, cadmium, chromium, nickel, zinc, mercury, barium, and combinations of any two or more thereof.
9. A process as recited in claim 8 wherein said heavy metal is mercury.
10. A process as recited in claim 9 wherein said composition converts at least a portion of said mercury in said gaseous feed stream from a zero oxidation to a +1 or a +2 oxidation state.
11. A process as recited in claim 9 wherein said mercury is present in said gaseous feed stream in an amount in the range of from about 0.1 to about 10,000 μg/m 3 .
12. A process as recited in claim 9 wherein said mercury is present in said gaseous product stream in an amount in the range of from about 1 to about 800 μg/m 3 .
13. A process as recited in claim 9 wherein said mercury is present in said gaseous product stream in an amount in the range of from about 3 to about 700 μg/m 3 .
14. A process as recited in claim 9 wherein said gaseous product stream contains less than about 80 weight % of the mercury contained in said gaseous feed stream.
15. A process as recited in claim 9 wherein said gaseous product stream contains less than about 90 weight % of the mercury contained in said gaseous feed stream.
16. A process as recited in claim 9 wherein said gaseous product stream contains less than about 95 weight % of the mercury contained in said gaseous feed stream.
17. A process as recited in claim 1 wherein said gaseous product stream is contacted, in an adsorption zone, with an adsorbent selected from the group consisting of a zeolite, amorphous carbon, and combinations thereof.
18. A process as recited in claim 17 wherein said composition oxidizes at least a portion of said heavy metal in said gaseous feed stream to an elevated oxidation state.
19. A process as recited in claim 17 wherein said heavy metal is mercury and wherein said composition oxidizes at least a portion of said mercury in said gaseous feed stream from a zero oxidation state to a +1 or a +2 oxidation state.
20. A process as recited in claim 17 wherein a treated gaseous product stream is withdrawn from said adsorption zone, and wherein said treated gaseous product stream contains less than about 95 weight % of the heavy metal contained in the gaseous feed stream.