Adsorbent bed for mercaptan removal with increased hydrothermal stability

1 . A method of removing water and mercaptans 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 mercaptans mole fraction and an initial water mole fraction toward an adsorbent bed, the adsorbent bed comprising:

a first adsorbent layer to remove water and mercaptans from the gas feed stream, the first adsorbent layer comprising one or more of an amorphous silica adsorbent, an amorphous silica-alumina adsorbent, or a high-silica zeolite adsorbent; and

a second adsorbent layer downstream from the first adsorbent layer to remove remaining water, the second adsorbent layer comprising a zeolite that is less hydrothermally stable than the adsorbent of the first adsorbent layer and selected from one or more of zeolite A or zeolite X,

wherein a weight percent (wt %) of the first adsorbent layer with respect to a total weight of the first adsorbent layer and the second adsorbent layer, is greater than 50 wt %,

wherein the gas feed stream has a reduced mercaptans mole fraction and a reduced water mole fraction when the gas feed stream reaches the second adsorbent layer, wherein the reduced mercaptans mole fraction is maintained for at least 90% of the duration of the adsorption step, and

wherein the reduced mercaptans mole fraction is less than or equal to about 90% of the initial mercaptans mole fraction, and wherein the reduced water mole fraction is less than about 20% of the initial water mole fraction.

2 . The method of claim 1 , wherein the reduced mercaptans mole fraction and/or the reduced water mole fraction is/are maintained for at least 99% of the duration of the adsorption step.

3 . The method of claim 1 , wherein the reduced water mole fraction is less than or equal to about 1 ppm, and wherein the reduced mercaptans mole fraction is less than or equal to about 5 ppm.

4 . The method of claim 1 , wherein the first adsorbent layer comprises the amorphous silica adsorbent and/or the amorphous silica-alumina adsorbent.

5 . The method of claim 1 , wherein the first adsorbent layer comprises the high-silica zeolite adsorbent, and wherein the high-silica zeolite adsorbent comprises ZSM-5, zeolite Y, or beta zeolite.

6 . The method of claim 1 , wherein the zeolite comprises one or more of zeolite 3A, zeolite 4A or zeolite 5A.

7 . The method of claim 1 , wherein the zeolite is exchanged with an element selected from Li, Na, K, Mg, Ca, Sr, or Ba.

8 . The method of claim 1 , wherein the adsorbent bed further comprises a third adsorbent layer downstream from the second adsorbent layer to remove remaining mercaptans, the third adsorbent layer comprising one or more of zeolite 3A, zeolite 4A, zeolite 5A, zeolite X, or zeolite Y.

9 . 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.

10 . 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, and wherein the water stable adsorbent is an amorphous silica or amorphous silica-alumina adsorbent.

11 . The method of claim 1 , wherein the gas feed stream is a natural gas feed stream.

12 . The method of claim 11 , further comprising:

forming a liquefied natural gas product from the gas feed stream after leaving the adsorbent bed.

13 . The method of claim 11 , further comprising:

forming a C2+ or C3+ natural gas liquid feed stream from the gas feed stream after leaving the adsorbent bed.

14 . A natural gas adsorption system adapted to perform the method of claim 1 .

15 . A thermal swing adsorption method to perform mercaptan removal and water removal in a single adsorbent bed, the method comprising:

directing a gas feed stream having an initial mercaptans mole fraction and an initial water mole fraction toward the adsorbent bed, the adsorbent bed comprising:

a first adsorbent layer to remove mercaptans and water from the gas feed stream, the first adsorbent layer comprising one or more of an amorphous silica adsorbent, an amorphous silica-alumina adsorbent, or a high-silica zeolite adsorbent;

and

a second adsorbent layer downstream from the first adsorbent layer to remove remaining mercaptans and/or water from the gas feed stream, the second adsorbent layer comprising a zeolite that is less hydrothermally stable than the adsorbent of the first adsorbent layer and selected from one or more of zeolite A or zeolite X,

wherein a weight percent (wt %) of the first adsorbent layer with respect to a total weight of the first adsorbent layer and the second adsorbent layer, is greater than 50 wt %, and

wherein the gas feed stream has a reduced mercaptans mole fraction when the gas feed stream reaches the second adsorbent layer that is maintained for at least 90% of the duration of each adsorption step of an adsorption cycle.

16 . A natural gas adsorption system adapted to perform the method of claim 15 .

17 . A method of removing water and mercaptans 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 mercaptans mole fraction and an initial water mole fraction toward an adsorbent bed, the adsorbent bed comprising:

a first adsorbent layer to remove water and mercaptans from the gas feed stream, the first adsorbent layer comprising one or more of an amorphous silica adsorbent or an amorphous silica-alumina adsorbent; and

a second adsorbent layer downstream from the first adsorbent layer to remove remaining water, the second adsorbent layer comprising a zeolite that is less hydrothermally stable than the adsorbent of the first adsorbent layer and selected from one or more of zeolite A or zeolite X,

wherein a weight percent (wt %) of the first adsorbent layer with respect to a total weight of the first adsorbent layer and the second adsorbent layer, is greater than 50 wt %, and

wherein the gas feed stream has a reduced mercaptans mole fraction and a reduced water mole fraction when the gas feed stream reaches the second adsorbent layer, wherein the reduced mercaptans mole fraction is maintained for at least 90% of the duration of the adsorption step, and

wherein the reduced mercaptans mole fraction is less than or equal to about 90% of the initial mercaptans mole fraction, and wherein the reduced water mole fraction is less than about 10% of the initial water mole fraction.