Adsorbent bed with increased hydrothermal stability
Disclosed in certain embodiments are methods of removing water from a gas feed stream comprising hydrocarbons and water during an adsorption step of an adsorption cycle.
1. A method of removing water from a gas feed stream comprising hydrocarbons and water during an adsorption step of an adsorption cycle, the method comprising:
directing the gas feed stream having an initial water mole fraction toward an adsorbent bed, the adsorbent bed comprising:
a first adsorbent layer comprising an adsorbent that is preferentially selective for C6+ hydrocarbons and comprises one or more of an amorphous silica adsorbent, an amorphous silica-alumina adsorbent, or a high-silica zeolite adsorbent, wherein a weight percent (wt. %) of the first adsorbent layer with respect to the total weight of the adsorbent bed is greater than 50 wt. %; and
a second adsorbent layer downstream from the first adsorbent layer to remove remaining water, the second adsorbent layer comprising a zeolite,
wherein, after passing through the first adsorbent layer, the gas feed stream has a reduced water mole fraction that is less than or equal to 10% of the initial water mole fraction when the gas feed stream reaches the second adsorbent layer.
2. The method of claim 1 , wherein the reduced water mole fraction is less than or equal to about 100 ppm.
3. The method of claim 1 , wherein the first adsorbent layer comprises the high-silica zeolite adsorbent.
4. The method of claim 1 , wherein the second adsorbent layer comprises one or more of zeolite A, zeolite X, or zeolite Y.
5. The method of claim 1 , wherein the adsorbent bed further comprises a third adsorbent layer downstream from the second adsorbent layer, the third adsorbent layer comprising an amorphous silica adsorbent or an amorphous silica-alumina adsorbent.
6. The method of claim 1 , wherein the adsorbent bed further comprises a third adsorbent layer downstream from the second adsorbent layer, the third adsorbent layer comprising zeolite X or zeolite Y.
7. The method of claim 1 , wherein the adsorbent bed further comprises a third adsorbent layer downstream from the second adsorbent layer, the third adsorbent layer having a higher selectivity to n-pentane over methane.
8. The method of claim 1 , wherein the adsorbent bed further comprises a third adsorbent layer upstream from the first adsorbent layer, the third adsorbent layer comprising a water stable adsorbent.
9. The method of claim 1 , wherein the gas feed stream is a natural gas feed stream.
10. The method of claim 1 , wherein a final water mole fraction of the gas feed stream leaving the adsorbent bed is below 1 ppm or below 0.1 ppm.
11. The method of claim 1 , further comprising:
forming a liquefied natural gas product from the gas feed stream after leaving the adsorbent bed.
12. The method of claim 1 , further comprising:
forming a C2+ or C3+ natural gas liquid feed stream from the gas feed stream after leaving the adsorbent bed.
13. The method of claim 1 , wherein the method is performed as part of a thermal swing adsorption process having a cycle time of less than or equal to about 8 hours, about 7 hours, about 6 hours, about 5 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour.
14. The method of claim 1 , wherein one or more components of the hydrocarbons in the gas feed stream is reduced by 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or 5% on a molar basis relative to an initial concentration of that component in the gas feed stream, wherein the one or more components are selected from a group consisting of benzene, C9 hydrocarbons, C8 hydrocarbons, C7 hydrocarbons, C6 hydrocarbons, and C5 hydrocarbons.
15. The method of claim 1 , further comprising:
prior to directing the gas feed stream toward the adsorbent bed, retrofitting the adsorbent bed by removing and replacing at least a portion of a previously present adsorbent with one or more of the first adsorbent layer or the second adsorbent layer.