Methods and systems for performing chemical separations

Abstract

The present disclosure provides a method for generating higher hydrocarbon(s) from a stream comprising compounds with two or more carbon atoms (C 2+ ), comprising introducing methane and an oxidant (e.g., O 2 ) into an oxidative coupling of methane (OCM) reactor. The OCM reactor reacts the methane with the oxidant to generate a first product stream comprising the C 2+ compounds. The first product stream can then be directed to a separations unit that recovers at least a portion of the C 2+ compounds from the first product stream to yield a second product stream comprising the at least the portion of the C 2+ compounds.

1 . A method for separating a product from a gas mixture, the method comprising:
 (a) at a first total pressure, directing a gas mixture comprising at least one impurity and a product gas into a pressure swing adsorption (PSA) vessel containing an adsorbent to adsorb the product gas on the adsorbent, wherein the product gas has a first partial pressure;   (b) at a second total pressure, directing a sweep gas into the PSA vessel to adsorb the sweep gas on the adsorbent and displace the product from the adsorbent to yield a displaced product, wherein the sweep gas has a second partial pressure that is greater than the first partial pressure of the product in the gas mixture; and   (c) desorbing the sweep gas from the adsorbent such that additional product is capable of adsorbing on the adsorbent.   
     
     
         2 . The method of  claim 1 , wherein (c) is performed at substantially the first total pressure. 
     
     
         3 . The method of  claim 1 , wherein an amount of the product that adsorbs on the adsorbent at the first partial pressure in (a) is substantially equivalent to the amount of sweep gas that adsorbs on the adsorbent at the second partial pressure in (b). 
     
     
         4 . The method of  claim 1 , wherein an amount of heat released by the adsorption of the product in (a) is substantially equivalent to an amount of heat released by the adsorption of the sweep gas in (b). 
     
     
         5 . The method of  claim 1 , wherein the displaced product is enriched relative to the concentration of the product in the gas mixture by a factor of at least about 2. 
     
     
         6 . The method of  claim 1 , wherein the displaced product includes at least some of the sweep gas. 
     
     
         7 . The method of  claim 6 , further comprising, following displacing the product from the adsorbent, separating the product from the sweep gas (e.g., by distillation). 
     
     
         8 . The method of  claim 1 , wherein the product is ethylene. 
     
     
         9 . The method of  claim 1 , wherein the sweep gas is ethane. 
     
     
         10 . The method of  claim 1 , wherein the gas mixture comprises at least 3 impurities. 
     
     
         11 . The method of  claim 1 , wherein the at least one impurity comprise carbon monoxide (CO), carbon dioxide (CO 2 ), methane, ethane, hydrogen (H 2 ), or any combination thereof. 
     
     
         12 . The method of  claim 1 , wherein the product has a concentration of less than about 30% in the gas mixture. 
     
     
         13 . The method of  claim 1 , wherein the adsorbent is a metal organic framework (MOF). 
     
     
         14 . The method of  claim 13 , wherein the MOF is M 2 (dobdc). 
     
     
         15 . The method of  claim 1 , wherein at the first pressure, a selectivity of the adsorbent for adsorbing the product as compared to the at least one impurity is at least about 5. 
     
     
         16 . The method of  claim 15 , wherein the at least one impurity is methane. 
     
     
         17 . The method of  claim 1 , wherein the gas mixture is derived from an effluent from an oxidative coupling of methane (OCM) reactor. 
     
     
         18 . The method of  claim 17 , further comprising recycling the at least one impurity to the OCM reactor following the adsorption of the product from the gas mixture. 
     
     
         19 . The method of  claim 18 , further comprising, prior to recycling the at least one impurity to the OCM reactor, converting carbon dioxide (CO 2 ), carbon monoxide (CO), and/or hydrogen (H 2 ) components of the at least one impurity to methane (CH 4 ). 
     
     
         20 . The method of  claim 1 , wherein following the adsorption of the product from the gas mixture, the gas mixture comprises a predetermined amount of a given impurity. 
     
     
         21 . The method of  claim 20 , wherein the given impurity is CO 2 . 
     
     
         22 . The method of  claim 20 , wherein the adsorbent comprises (i) a first material that adsorbs the product and the given impurity, and (ii) a second material that adsorbs the product but does not substantially adsorb the given impurity. 
     
     
         23 . The method of  claim 22 , wherein an amount of the first material relative to an amount of the second material is selected to achieve the desired amount of the desired impurity. 
     
     
         24 . The method of  claim 22 , wherein the first material is a CaX zeolite and the second material is a metal organic framework. 
     
     
         25 .- 40 . (canceled) 
     
     
         41 . A method for separating oxygen (O 2 ) from nitrogen (N 2 ), the method comprising:
 (a) at a first pressure, directing a mixture of O 2  and N 2  into a pressure swing adsorption (PSA) vessel containing an adsorbent to adsorb the O 2  on the adsorbent, wherein the adsorbent is a metal organic framework (MOF) that is selective for O 2 ; and   (b) at a second pressure that is less than the first pressure, desorbing the O 2  from the adsorbent with a purge gas.   
     
     
         42 .- 81 . (canceled) 
     
     
         82 . A method for generating compounds with two or more carbon atoms (C 2+  compounds), comprising:
 (a) directing oxygen (O 2 ) and methane (CH 4 ) into an oxidative coupling of methane (OCM) reactor having a catalytic section and a cracking section to produce an OCM product stream, which catalytic section reacts the O 2  and CH 4  to yield ethylene (C 2 H 4 ), ethane (C 2 H 6 ) and heat, which cracking section uses the heat to convert C 2 H 6  into C 2 H 4 , and which product stream comprises (i) C 2+  compounds including ethylene (C 2 H 4 ) and ethane (C 2 H 6 ) and (ii) C 1  compounds including un-reacted CH 4 ; 
 (b) directing the product stream into a separations unit containing a metal organic framework (MOF) that produces (i) a first stream comprising the C 2 H 4 , (ii) a second stream comprising the C 2 H 6  and (iii) a third stream comprising the C 1  compounds; 
 (c) directing the second stream into the cracking section; and 
 (d) directing the third stream into the catalytic section. 
 
     
     
         83 .- 111 . (canceled) 
     
     
         112 . An adsorbent, comprising:
 a. a first material that adsorbs (i) a product gas at a first heat of adsorption and (ii) a sweep gas at a second heat of adsorption; and   b. a second material that adsorbs the sweep gas at a third heat of adsorption,   wherein the first material and the second material are included in a mixed material in a relative proportion such that the mixed material has an average heat of adsorption for the sweep gas, and   wherein an absolute value of a difference between the first heat of adsorption and the average heat of adsorption is less than an absolute value of a difference between the first heat of adsorption and the second heat of adsorption.   
     
     
         113 .- 135 . (canceled)