Materials, methods, and devices for siloxane contaminant removal
Adsorbent materials are disclosed, along with filter elements containing the adsorbent materials methods of using adsorbents to remove siloxane contaminants from a gas stream. The method includes providing an adsorbent material that has been washed with an acid and passing a gas through the adsorbent material so as to reduce siloxane levels in the gas. A filter element for reducing siloxane levels in a gas includes a first adsorbent material, the first adsorbent material comprising an acid-washed adsorbent; and a second adsorbent material, the second adsorbent material comprising an acid-impregnated adsorbent.
1. A method of reducing siloxane levels in a gas, the method comprising:
providing a first adsorbent material comprising activated carbon that has been washed with an acid;
passing a gas through the first adsorbent material so as to reduce siloxane levels in the gas;
providing a second adsorbent material comprising activated carbon impregnated with phosphoric acid; and
passing the gas through the second adsorbent material.
2. The method of claim 1 , wherein the gas is passed through the first adsorbent material and subsequently passed through the second adsorbent material.
3. The method of claim 1 , wherein the gas is passed through the second adsorbent material and subsequently passed through the first adsorbent material.
4. The method of claim 1 , further comprising providing an acid gas remover, wherein the ratio of first adsorbent to acid gas remover is from 3:1 to 1:3.
5. A filter element for reducing siloxane levels in a gas, the filter element comprising:
a first adsorbent material, the first adsorbent material comprising an activated carbon that has been acid-washed; and
a second adsorbent material, the second adsorbent material comprising an activated carbon impregnated with phosphoric acid.
6. The filter element of claim 5 , wherein the first adsorbent material comprises silica gel.
7. The filter element of claim 5 , wherein the acid of the acid-wash comprises a strong acid.
8. The filter element of claim 5 , wherein the acid of the acid-wash comprises nitric acid.
9. The filter element of claim 5 , wherein the acid-wash comprises an aqueous solution of at least 5 percent nitric acid.
10. The filter element of claim 5 , wherein the filter element is configured for a gas to first pass through the first adsorbent material and subsequently pass through the second adsorbent material.
11. The filter element of claim 5 , wherein the filter element is configured for a gas to first pass through the second adsorbent material and subsequently pass through the first adsorbent material.
12. The filter element of claim 5 , further comprising an acid gas remover.
13. The filter element of claim 12 , wherein the acid gas remover comprises an adsorbent impregnated with an impregnate selected from the group consisting of: potassium iodide, potassium carbonate, and combinations thereof.
14. The filter element of claim 12 , wherein the ratio of first adsorbent to acid gas remover is from 3:1 to 1:3.
15. A filtration system for reducing siloxane levels in a gas, the filtration system comprising:
a first filter element comprising a first adsorbent material, the first adsorbent material comprising an activated carbon that has been acid-washed;
a second filter element comprising a second adsorbent material, the second adsorbent material comprising an activated carbon impregnated with phosphoric acid; and
wherein the filter system is configured in a series for a majority of the gas to pass through the first filter element and the second filter element.
16. The system of claim 15 , wherein the first adsorbent material is selected from the group silica gel, activated alumina, zeolites, nanoporous supports, and combinations thereof.
17. The system of claim 15 , wherein the acid of the acid-washed adsorbent comprises nitric acid.