Patent Publication Number: US-2023159409-A1

Title: Conversion of hydrogen sulfide and carbon dioxide into hydrocarbons using non-thermal plasma and a catalyst

Description:
TECHNICAL FIELD 
     This disclosure relates to conversion of hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) into hydrocarbons. 
     BACKGROUND 
     Hydrogen sulfide and carbon dioxide exist in various gas streams, including natural gas. Oil or gas that contains significant amounts of sulfur compounds like hydrogen sulfide is considered “sour”, and oil refineries and gas processing plants utilize “sweetening” processes to remove such sulfur compounds. A typical sulfur recovery process includes liquid amine absorption and the Claus process. In liquid amine absorption, hydrogen sulfide and carbon dioxide are selectively removed from gas mixtures, and the hydrogen sulfide and carbon dioxide are flowed to the Claus process, which can convert the hydrogen sulfide into elemental sulfur. The Claus process utilizes oxygen to oxidize hydrogen sulfide into sulfur dioxide and water, and the sulfur dioxide reacts with hydrogen sulfide to produce elemental sulfur and water. The carbon dioxide, on the other hand, is typically released into the atmosphere without further use. 
     SUMMARY 
     Certain aspects of the subject matter described can be implemented as a method. A feed stream is flowed to a catalytic reactor. The catalytic reactor includes a non-thermal plasma and a catalyst. The feed stream includes hydrogen sulfide and carbon dioxide. The feed stream is contacted with the catalyst in the presence of the non-thermal plasma at a reaction temperature, thereby converting the hydrogen sulfide and the carbon dioxide in the feed stream to produce a product. The product includes a hydrocarbon and sulfur. The reaction temperature is in a range of from about 20 degrees Celsius (° C.) to about 900° C. The product is separated into a product stream and a sulfur stream. The product stream includes the hydrocarbon from the product. The sulfur stream includes the sulfur from the product. 
     This, and other aspects, can include one or more of the following features. In some implementations, the reaction temperature is in a range of from about 150° C. to about 250° C. In some implementations, the feed stream is contacted with the catalyst in the presence of the non-thermal plasma at a reaction pressure that is in a range of from about 1 bar to about 10 bar. In some implementations, the reaction pressure is about 1 bar. In some implementations, separating the product into the product stream and the sulfur stream includes condensing the sulfur, such that the sulfur stream is liquid. In some implementations, the catalyst includes a metal that includes at least one of molybdenum, cadmium, iron, cobalt, nickel, copper, zinc, chromium, palladium, or ruthenium. In some implementations, the catalyst includes a metal oxide that includes at least one of molybdenum oxide, cadmium oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, chromium oxide, aluminum oxide, titanium oxide, zirconium oxide, gallium oxide, or magnesium oxide. In some implementations, the catalyst includes a metal sulfide that includes at least one of molybdenum sulfide, cadmium sulfide, iron sulfide, cobalt sulfide, nickel sulfide, copper sulfide, zinc sulfide, or chromium sulfide. In some implementations, the catalyst includes a zeolite-based catalyst that includes at least one of Zeolite Socony Mobil-5 (ZSM-5), titanium silicalite (TS-1), silicoaluminophosphate zeolite (SAPO-34), UOP zeolite material (UZM), mordenite (MOR), beta zeolite (BEA), or faujasite (FAU). In some implementations, the product stream includes at least one of methane or ethane. In some implementations, the non-thermal plasma is generated by a corona discharge, a dielectric barrier discharge, or a gliding arc discharge. In some implementations, the catalytic reactor includes a high voltage electrode, a dielectric barrier surrounding the catalyst, and a grounding electrode surrounding the dielectric barrier. In some implementations, the catalyst surrounds the high voltage electrode. In some implementations, a volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream is about 1:1. 
     Certain aspects of the subject matter described can be implemented as a method. A first feed stream is flowed to a first catalytic reactor. The first catalytic reactor includes a first non-thermal plasma and a first catalyst. The first feed stream includes hydrogen sulfide and carbon dioxide. The first feed stream is contacted with the first catalyst in the presence of the first non-thermal plasma at a first reaction temperature, thereby converting the hydrogen sulfide and the carbon dioxide in the first feed stream to produce a first intermediate product. The first intermediate product includes hydrogen, carbon monoxide, water, and sulfur. The first reaction temperature is in a range of from about 20 degrees Celsius (° C.) to about 900° C. The first intermediate product is separated into a second intermediate product and a first sulfur stream. The second intermediate product includes the hydrogen, the carbon monoxide, and the water from the first intermediate product. The first sulfur stream includes at least a portion of the sulfur from the first intermediate product. The second intermediate product is separated into a second feed stream and a second sulfur stream. The second feed stream includes the hydrogen, the carbon monoxide, and the water from the second intermediate product. The second sulfur stream includes at least a portion of the sulfur from the second intermediate product. The second feed stream is flowed to a second catalytic reactor. The second catalytic reactor includes a second non-thermal plasma and a second catalyst. The second feed stream is contacted with the second catalyst in the presence of the second non-thermal plasma at a second reaction temperature, thereby converting the hydrogen and the carbon monoxide in the second feed stream to produce a product. The product includes a hydrocarbon. The second reaction temperature is in a range of from about 20° C. to about 900° C. 
     This, and other aspects, can include one or more of the following features. In some implementations, the first reaction temperature and the second reaction temperature are in a range of from about 150° C. to about 250° C. In some implementations, the first feed stream is contacted with the first catalyst in the presence of the first non-thermal plasma at a first reaction pressure that is in a range of from about 1 bar to about 10 bar. In some implementations, the second feed stream is contacted with the second catalyst in the presence of the second non-thermal plasma at a second reaction pressure that is in a range of from about 1 bar to about 10 bar. In some implementations, the first reaction pressure and the second reaction pressure are about 1 bar. In some implementations, separating the first intermediate product into the second intermediate product and the first sulfur stream includes condensing at least a portion of the sulfur from the first intermediate product, such that the first sulfur stream is liquid. In some implementations, separating the second intermediate product stream into the second feed stream and the second sulfur stream includes contacting the second intermediate product stream with a solvent or a sorbent. In some implementations, the product includes at least one of methane or ethane. In some implementations, the first non-thermal plasma is generated by a first corona discharge, a first dielectric barrier discharge, or a first gliding arc discharge. In some implementations, the second non-thermal plasma is generated by a second corona discharge, a second dielectric barrier discharge, or a second gliding arc discharge. In some implementations, the first catalytic reactor includes a first high voltage electrode, a first dielectric barrier surrounding the first catalyst, and a first grounding electrode surrounding the first dielectric barrier. In some implementations, the first catalyst surrounds the first high voltage electrode. In some implementations, the second catalytic reactor includes a second high voltage electrode, a second dielectric barrier surrounding the second catalyst, and a second grounding electrode surrounding the second dielectric barrier. In some implementations, the second catalyst surrounds the second high voltage electrode. 
     The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a schematic diagram of an example system for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). 
         FIG.  1 B  is a cross-sectional view of an example catalytic reactor that can be implemented in the system of  FIG.  1 A . 
         FIG.  1 C  is a flow chart of an example method for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). 
         FIG.  2 A  is a schematic diagram of an example two-stage system for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). 
         FIG.  2 B  is a flow chart of an example two-stage method for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes conversion of hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) into hydrocarbons. A feed stream including hydrogen sulfide and carbon dioxide is flowed to a reactor that includes a catalyst and non-thermal plasma. The feed stream contacts the catalyst in the presence of the non-thermal plasma at reaction conditions, thereby converting the hydrogen sulfide and the carbon dioxide to produce a product that includes hydrocarbon(s). Sulfur originating from the hydrogen sulfide can be separated from the product. The process can be implemented by a single-stage system or a multi-stage system. The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages. In comparison to the Claus process, the methods and systems described in this disclosure do not require the addition of oxygen. Further, the methods and systems described in this disclosure produce valuable products, such as hydrocarbons and hydrogen gas. Carbon monoxide and carbon dioxide (known greenhouse gases) are used as feedstock to produce the aforementioned valuable products (hydrocarbons and hydrogen gas). The hydrogen originating from the hydrogen sulfide is not simply oxidized to produce water (as it does in the Claus process). Instead, the hydrogen originating from the hydrogen sulfide is a source for producing the aforementioned valuable products (hydrocarbons and hydrogen gas). 
       FIG.  1 A  is a schematic diagram of an example system  100  for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). The system  100  includes a catalytic reaction unit  110 . The catalytic reaction unit  110  includes a catalytic reactor  111 . The catalytic reactor  111  includes a non-thermal plasma  113  and a catalyst  115 . A feed stream  102  flows to the catalytic reactor  111 . The feed stream  102  includes hydrogen sulfide and carbon dioxide. In some implementations, a volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream  102  is in a range of from about 9:1 to about 1:9. For example, the volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream  102  is about 1:1. The feed stream  102  can also include additional molecular compounds, such as water (H 2 O, in the form of water vapor) and hydrocarbon(s). For example, the feed stream  102  can include molecular compounds typically present in a Claus feed (that is, a feed stream entering a Claus process reactor). In some implementations, the hydrogen sulfide and the carbon dioxide in the feed stream  102  is sufficient to generate the non-thermal plasma  113 . In some implementations, the feed stream  102  also includes a gas that is used to facilitate generation of the non-thermal plasma  113 . For example, the feed stream  102  can include an inert gas (such as nitrogen, helium, neon, and argon) or oxygen. Within the catalytic reactor  111 , the feed stream  102  comes into contact with the catalyst  115  in the presence of the non-thermal plasma  113 . 
     The catalyst  115  is configured to accelerate reaction(s) involving conversion of the hydrogen sulfide and the carbon dioxide in the feed stream  102 . For example, the catalyst  115  can accelerate the conversion of hydrogen sulfide into hydrogen (H 2 ) and sulfur (S). For example, the catalyst  115  can accelerate the conversion of carbon dioxide into carbon monoxide (CO) and oxygen (O 2 ). In some implementations, the catalyst  115  is configured to shift the pathways of reaction(s) to selectively produce hydrocarbon(s) from carbon dioxide (from the feed stream  102 ), carbon monoxide (originating from the carbon dioxide from the feed stream  102 ), and hydrogen (originating from the hydrogen sulfide from the feed stream  102 ). For example, the catalyst  115  can accelerate reaction(s) between carbon dioxide and hydrogen to produce hydrocarbon(s) and water. For example, the catalyst  115  can accelerate reaction(s) between carbon monoxide and hydrogen to produce hydrocarbon(s) and water. In some implementations, the catalyst  115  is a supported metal-based catalyst. For example, the catalyst  115  can be a molybdenum-, cadmium-, iron-, cobalt-, nickel-, copper-, zinc-, chromium-, palladium-, or ruthenium-based catalyst supported on an aluminum oxide-, titanium oxide-, silicon oxide-, zirconium oxide-, lanthanum oxide-, cerium oxide-, magnesium oxide-, indium oxide-, or carbon-based support. In some implementations, the catalyst  115  is a metal oxide-based catalyst. For example, the catalyst  115  can be a molybdenum oxide-, cadmium oxide-, iron oxide-, cobalt oxide-, nickel oxide-, copper oxide-, zinc oxide-, chromium oxide-, aluminum oxide-, titanium oxide-, zirconium oxide-, gallium oxide-, or magnesium oxide-based catalyst. In some implementations, the catalyst  115  is a metal sulfide-based catalyst. For example, the catalyst  115  can be a molybdenum sulfide-, cadmium sulfide-, iron sulfide-, cobalt sulfide-, nickel sulfide-, copper sulfide-, zinc sulfide-, or chromium sulfide-based catalyst. In some implementations, the catalyst  115  is a zeolite-based catalyst. For example, the catalyst  115  can be a Zeolite Socony Mobil-5 (ZSM-5)-, titanium silicalite (TS-1)-, silicoaluminophosphate zeolite (SAPO-34)-, UOP zeolite material (UZM)-, mordenite (MOR)-, beta zeolite (BEA)-, or faujasite (FAU)-based catalyst. 
     The non-thermal plasma  113  is a plasma that is not in thermodynamic equilibrium. The non-thermal plasma  113  is not in thermodynamic equilibrium because the temperature of the electrons in the non-thermal plasma  113  is much greater than the temperature of the heavy species, such as the ions and the neutrals in the non-thermal plasma  113 . The non-thermal plasma  113  is configured to promote dissociation of hydrogen sulfide and carbon dioxide. For example, the non-thermal plasma  113  can promote dissociation of hydrogen sulfide into hydrogen and sulfur. For example, the non-thermal plasma  113  can promote dissociation of carbon dioxide into carbon monoxide and oxygen. In some implementations, the non-thermal plasma  113  is generated by a corona discharge. In some implementations, the non-thermal plasma  113  is generated by a dielectric barrier discharge (DBD). In some implementations, the non-thermal plasma  113  is generated by a gliding arc discharge. A gliding arc discharge utilizes two diverging electrodes that are positioned such that their edges point toward each other to create a diverging discharge gap. In some implementations, the non-thermal plasma  113  is generated by an arc discharge. An arc discharge can generate the non-thermal plasma  113  between two electrodes with a similar or different geometry from the gliding arc discharge. An arc discharge is a low-current arc discharge, in contrast to a high-current thermal arc discharge. 
     The non-thermal plasma  113  and the catalyst  115  can operate synergistically within the catalytic reactor  111 . For example, the non-thermal plasma  113  can activate and/or promote the catalyst  115 . In some cases, the non-thermal plasma  113  can alter the adsorption/desorption equilibrium on a surface of the catalyst  115 , which can lead to increased adsorption capabilities. In some cases, the non-thermal plasma  113  exposes the catalyst  115  to a discharge, which can lead to the formation of nanoparticles. The increased surface-to-volume ratio of nanoparticles can improve performance of the catalyst  115 . In cases where the catalyst  115  is a metal oxide, the exposure of discharge from the non-thermal plasma  113  to the catalyst  115  can induce a reduction in the metal oxide of the catalyst  115 , which can improve catalytic activity. In some cases, the non-thermal plasma  113  can reduce the probability and/or rate of coke formation. Coke formation can poison and/or deactivate the catalyst  115 . Therefore, in such cases, the presence of the non-thermal plasma  113  can extend the operating life of the catalyst  115 . As mentioned previously, the non-thermal plasma  113  can promote disassociation reactions, which can result in the production of radicals. In some cases, radicals can exhibit high sticking coefficients for transfer of electrons on the catalyst  115 , thereby promoting catalytic activity. In some cases, the non-thermal plasma  113  contains photons which can potentially facilitate photocatalytic reactions in the presence of the catalyst  115 , when a suitable catalyst is used. In some cases, the non-thermal plasma  113  vibrationally or electronically excite the hydrogen sulfide and/or carbon dioxide gas molecules, which can decrease an energy of dissociation when the gas molecules adsorb on a surface of the catalyst  115  in comparison to the gas molecules in their non-excited ground state. In the absence of the catalyst  115 , the excited gas molecules may return to their ground state and emit the energy difference in the form of light. In some cases, the catalyst  115  can enhance the properties of the non-thermal plasma  113 . For example, particles of the catalyst  115  with high electric constants can enhance the electric field strength for the non-thermal plasma  113 . As another example, packing of the catalyst  115  can modify the nature of the discharge generating the non-thermal plasma  113  (such as changing the discharge from a microdischarge or streamer mode discharge to a more spatially confined, surface discharge). As another example, the chemical properties of the catalyst  115  can alter the non-thermal plasma  113  (such as, the catalyst  113  can have a high silicon to aluminum ratio, which can lead to a larger drop in electrical resistivity, thereby decreasing surface streamer propagation in the discharge generating the non-thermal plasma  113 ). As another example, in cases where the catalyst  115  is provided as a packed bed, the configuration of the packed bed within the electric field (which generates the non-thermal plasma  113 ) can generate local electric field enhancements due to inhomogeneity in the packed bed physical structure and/or surfaces of the catalyst  115 . The surface charge accumulation in the packed bed can improve the properties of the non-thermal plasma  113 . Similarly, the presence of random void spaces in the packed bed can also generate local electric field enhancements in the non-thermal plasma  113 . The high intensity of the electric field in a locale can lead to the production of certain species (for example, desired hydrocarbons) that may not be observed in the bulk. 
     In some implementations, an operating temperature within the catalytic reactor  111  (also referred to as a reaction temperature) is in a range of from about 20 degrees Celsius (° C.) to about 900° C. In some implementations, the reaction temperature is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, an operating pressure within the catalytic reactor  111  (also referred to as a reaction pressure) is in a range of from about 1 bar to about 10 bar. In some implementations, the reaction pressure is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the reaction pressure is about 1 bar (atmospheric pressure). 
     Bringing the feed stream  102  into contact with the catalyst  115  in the presence of the non-thermal plasma  113  within the catalytic reactor  111  at the reaction temperature and the reaction pressure results in conversion of the hydrogen sulfide and the carbon dioxide in the feed stream  102  to produce a product  104 . The product  104  includes a hydrocarbon and sulfur. In some implementations, the product  104  includes at least one of methane, ethane, or a hydrocarbon with more carbon atoms than ethane (such as propane and butane). The product  104  can also include additional molecular compounds, such as hydrogen, carbon monoxide, and water. In some cases, the product  104  also includes unreacted hydrogen sulfide and/or unreacted carbon dioxide from the feed stream  102 . 
     The product  104  is separated into a product stream  106  and a sulfur stream  108 . The product stream  106  includes the hydrocarbon from the product  104 . In cases where the product  104  includes multiple hydrocarbons, the product stream  106  includes the hydrocarbons from the product  104 . In cases where the product  104  includes unreacted hydrogen sulfide and/or unreacted carbon dioxide from the feed stream  102 , the product stream  106  includes the unreacted hydrogen sulfide and/or unreacted carbon dioxide from the product  104 . The sulfur stream  108  includes the sulfur from the product  104 . In some implementations, separating the product  104  into the product stream  106  and the sulfur stream  108  includes cooling the product  104 , such that a portion of the product  104  is condensed. For example, the catalytic reaction unit  110  can include a condenser (not shown), and the condenser can cool the product  104 , such that a portion of the product  104  is condensed and separated from a remaining gaseous portion of the product  104 . In such implementations, the condensed portion of the product  104  is the sulfur stream  108 , and the remaining gaseous portion of the product  104  is the product stream  106 . For example, the sulfur in the sulfur stream  108  can be liquid sulfur. In some implementations, the sulfur stream  108  includes additional condensable compounds in liquid form, such as water. 
       FIG.  1 B  is a cross-sectional view of an example of the catalytic reactor  111 . In some implementations, the catalytic reactor  111  includes a high voltage electrode  111   a  and a grounding electrode  111   b . The high voltage electrode  111   a  uses a voltage in a range of from about 1 kilovolt (kV) to about 50 kV and works with the grounding electrode  111   b  to generate an electric field. In some implementations, the catalytic reactor  111  includes a dielectric barrier  111   c . The dielectric barrier  111   c  can be included in between the electrodes  111   a  and  111   b  and serves as an electrically insulating material. The electrical discharge between the electrodes  111   a  and  111   b  separated by the dielectric barrier  111   c  (also referred to as a dielectric barrier discharge) interacts with the gas in the catalytic reactor  111  to generate the non-thermal plasma  113 . The catalyst  115  can be disposed within the catalytic reactor  111  in a region of the catalytic reactor  111  where the dielectric barrier discharge generates the non-thermal plasma  113 . For example (as shown in  FIG.  1 B ), the high voltage electrode  111   a  can be centrally located within the catalytic reactor  111 ; the dielectric barrier  111   c  can circumferentially surround the high voltage electrode  111   a ; the grounding electrode  111   b  can circumferentially surround the dielectric barrier  111   c ; and the catalyst  115  can be disposed in the annular region between the high voltage electrode  111   a  and the dielectric barrier  111   c . The annular region between the high voltage electrode  111   a  and the dielectric barrier  111   c  can also be the region in which the non-thermal plasma  113  is generated within the catalytic reactor  111 . In some implementations (as shown in  FIG.  1 B ), the catalyst  115  is provided within the catalytic reactor  111  in the form of a packed bed. 
       FIG.  1 C  is a flow chart of an example method  150  for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). The system  100  can implement the method  150 . At block  152  a feed stream (such as the feed stream  102 ) is flowed to a catalytic reactor (such as the catalytic reactor  111 ). As mentioned previously, the feed stream  102  includes hydrogen sulfide and carbon dioxide, and the catalytic reactor  111  includes the non-thermal plasma  113  and the catalyst  115 . In some implementations, a volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream  102  at block  152  is about 1:1. 
     At block  154 , the feed stream  102  is contacted with the catalyst  115  in the presence of the non-thermal plasma  113  within the catalytic reactor  111 . The feed stream  102  is contacted with the catalyst  115  in the presence of the non-thermal plasma  113  at block  154  at a reaction temperature that is in a range of from about 20° C. to about 900° C. Contacting the feed stream  102  with the catalyst  115  in the presence of the non-thermal plasma  113  at block  154  results in converting the hydrogen sulfide and the carbon dioxide in the feed stream  102  to produce a product (such as the product  104 ). As mentioned previously, the product  104  includes a hydrocarbon and sulfur. In some implementations, the reaction temperature at block  154  is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, an operating pressure within the catalytic reactor  111  (also referred to as a reaction pressure) at block  154  is in a range of from about 1 bar to about 10 bar. In some implementations, the reaction pressure at block  154  is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the reaction pressure at block  154  is about 1 bar (atmospheric pressure). 
     At block  156 , the product  104  is separated into a product stream (such as the product stream  106 ) and a sulfur stream (such as the sulfur stream  108 ). In some implementations, separating the product  104  into the product stream  106  and the sulfur stream  108  at block  156  includes cooling the product  104 , such that a portion of the product  104  is condensed. In such implementations, the condensed portion of the product  104  is the sulfur stream  108 , and the remaining gaseous portion of the product  104  is the product stream  106 . As mentioned previously, the product stream  106  includes the hydrocarbon from the product  104 . In cases where the product  104  includes multiple hydrocarbons, the product stream  106  includes the hydrocarbons from the product  104 . For example, the product stream  106  includes methane, ethane, or both methane and ethane. 
       FIG.  2 A  is a schematic diagram of an example two-stage system  200  for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). The two-stage system  200  shown in  FIG.  2 A  can be substantially similar to the system  100  shown in  FIG.  1 A . The two-stage system  200  includes a first catalytic reaction unit  210 . The first catalytic reaction unit  210  includes a first catalytic reactor  211 . The first catalytic reactor  211  can be substantially similar or substantially the same to the catalytic reactor  111  shown in  FIGS.  1 A and  1 B . The first catalytic reactor  211  includes a first non-thermal plasma  213  and a first catalyst  215 . The first non-thermal plasma  213  can be substantially similar or substantially the same as the first non-thermal plasma  113  shown in  FIGS.  1 A and  1 B . The first catalyst  215  can be substantially similar or substantially the same to the catalyst  115  shown in  FIGS.  1 A and  1 B . 
     A first feed stream  202  flows to the first catalytic reactor  211 . The first feed stream  202  can be substantially similar or substantially the same to the feed stream  102  shown in  FIG.  1 A . The feed stream  202  includes hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ). In some implementations, a volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream  202  is in a range of from about 9:1 to about 1:9. For example, the volumetric ratio of the hydrogen sulfide to the carbon dioxide in the feed stream  202  is about 1:1. The first feed stream  202  can also include additional molecular compounds, such as water (for example, in the form of water vapor) and hydrocarbon(s). For example, the first feed stream  202  can include molecular compounds typically present in a Claus feed (that is, a feed stream entering a Claus process reactor). In some implementations, the hydrogen sulfide and the carbon dioxide in the feed stream  202  is sufficient to generate the non-thermal plasma  213 . In some implementations, the first feed stream  202  also includes a gas that is used to facilitate generation of the first non-thermal plasma  213 . For example, the first feed stream  202  can include an inert gas (such as nitrogen, helium, neon, and argon) or oxygen. Within the first catalytic reactor  211 , the first feed stream  202  comes into contact with the first catalyst  215  in the presence of the first non-thermal plasma  213 . 
     The first catalyst  215  is configured to accelerate reaction(s) involving conversion of the hydrogen sulfide and the carbon dioxide in the first feed stream  202 . For example, the first catalyst  215  can accelerate the conversion of hydrogen sulfide into hydrogen (H 2 ) and sulfur (S). For example, the first catalyst  215  can accelerate the conversion of carbon dioxide into carbon monoxide (CO) and oxygen (O 2 ). In some implementations, the first catalyst  215  is configured to shift the pathways of reaction(s) to selectively produce hydrocarbon(s) from carbon dioxide (from the first feed stream  202 ), carbon monoxide (originating from the carbon dioxide from the first feed stream  202 ), and hydrogen (originating from the hydrogen sulfide from the first feed stream  202 ). For example, the first catalyst  215  can accelerate reaction(s) between carbon dioxide and hydrogen to produce hydrocarbon(s) and water. For example, the first catalyst  215  can accelerate reaction(s) between carbon monoxide and hydrogen to produce hydrocarbon(s) and water. In some implementations, the first catalyst  215  is a supported metal-based catalyst. For example, the first catalyst  215  can be a molybdenum-, cadmium-, iron-, cobalt-, nickel-, copper-, zinc-, chromium-, palladium-, or ruthenium-based catalyst supported on an aluminum oxide-, titanium oxide-, silicon oxide-, zirconium oxide-, lanthanum oxide-, cerium oxide-, magnesium oxide-, indium oxide-, or carbon-based support. In some implementations, the first catalyst  215  is a metal oxide-based catalyst. For example, the first catalyst  215  can be a molybdenum oxide-, cadmium oxide-, iron oxide-, cobalt oxide-, nickel oxide-, copper oxide-, zinc oxide-, chromium oxide-, aluminum oxide-, titanium oxide-, zirconium oxide-, gallium oxide-, or magnesium oxide-based catalyst. In some implementations, the first catalyst  215  is a metal sulfide-based catalyst. For example, the first catalyst  215  can be a molybdenum sulfide-, cadmium sulfide-, iron sulfide-, cobalt sulfide-, nickel sulfide-, copper sulfide-, zinc sulfide-, or chromium sulfide-based catalyst. In some implementations, the first catalyst  215  is a zeolite-based catalyst. For example, the first catalyst  215  can be a Zeolite Socony Mobil-5 (ZSM-5)-, titanium silicalite (TS-1)-, silicoaluminophosphate zeolite (SAPO-34)-, UOP zeolite material (UZM)-, mordenite (MOR)-, beta zeolite (BEA)-, or faujasite (FAU)-based catalyst. 
     The first non-thermal plasma  213  is a plasma that is not in thermodynamic equilibrium. The first non-thermal plasma  213  is not in thermodynamic equilibrium because the temperature of the electrons in the first non-thermal plasma  213  is much greater than the temperature of the heavy species, such as the ions and the neutrals in the first non-thermal plasma  213 . The first non-thermal plasma  213  is configured to promote dissociation of hydrogen sulfide and carbon dioxide. For example, the first non-thermal plasma  213  can promote dissociation of hydrogen sulfide into hydrogen and sulfur. For example, the first non-thermal plasma  213  can promote dissociation of carbon dioxide into carbon monoxide and oxygen. In some implementations, the first non-thermal plasma  213  is generated by a corona discharge. In some implementations, the first non-thermal plasma  213  is generated by a dielectric barrier discharge. In some implementations, the first non-thermal plasma  213  is generated by a gliding arc discharge. In some implementations, the first non-thermal plasma  213  is generated by an arc discharge. Similar to the non-thermal plasma  113  and the catalyst  115  shown in  FIGS.  1 A and  1 B , the first non-thermal plasma  213  and the first catalyst  215  can operate synergistically within the first catalytic reactor  211 . 
     In some implementations, an operating temperature within the first catalytic reactor  211  (also referred to as a first reaction temperature) is in a range of from about 20° C. to about 900° C. In some implementations, the first reaction temperature is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, an operating pressure within the first catalytic reactor  211  (also referred to as a first reaction pressure) is in a range of from about 1 bar to about 10 bar. In some implementations, the first reaction pressure is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the first reaction pressure is about 1 bar (atmospheric pressure). 
     Bringing the first feed stream  202  into contact with the first catalyst  215  in the presence of the first non-thermal plasma  213  within the first catalytic reactor  211  at the first reaction temperature and the first reaction pressure results in conversion of the hydrogen sulfide and the carbon dioxide in the first feed stream  202  to produce a first intermediate product  204 . The first intermediate product  204  includes hydrogen, carbon monoxide, water, and sulfur. In some implementations, the first intermediate product  204  includes a hydrocarbon. In some implementations, the first intermediate product  204  includes at least one of methane, ethane, or a hydrocarbon with more carbon atoms than ethane (such as propane and butane). The first intermediate product  204  can also include additional molecular compounds, such as unreacted hydrogen sulfide and unreacted carbon dioxide from the first feed stream  202 . 
     The first intermediate product  204  is separated into a second intermediate product  206  and a first sulfur stream  208 . The second intermediate product  206  includes the hydrogen, the carbon monoxide, and the water from the first intermediate product  204 . In cases where the first intermediate product  204  includes hydrocarbon(s), the second intermediate product  206  includes the hydrocarbon(s) from the first intermediate product  204 . In cases where the first intermediate product  204  includes unreacted hydrogen sulfide and/or unreacted carbon dioxide from the first feed stream  202 , the second intermediate product  206  includes the unreacted hydrogen sulfide and/or unreacted carbon dioxide from the first intermediate product  204 . The first sulfur stream  208  includes at least a portion of the sulfur from the first intermediate product  204 . In some cases, the second intermediate product  206  includes a remaining portion of the sulfur from the first intermediate product  204  that is not separated into the first sulfur stream  208 . For example, the second intermediate product  206  may include trace amounts of sulfur. In some implementations, separating the first intermediate product  204  into the second intermediate product  206  and the first sulfur stream  208  includes cooling the first intermediate product  204 , such that a portion of the first intermediate product  204  is condensed. For example, the first catalytic reaction unit  210  can include a first condenser (not shown), and the first condenser can cool the first intermediate product  204 , such that a portion of the first intermediate product  204  is condensed and separated from a remaining gaseous portion of the first intermediate product  204 . In such implementations, the condensed portion of the first intermediate product  204  is the first sulfur stream  208 , and the remaining gaseous portion of the first intermediate product  204  is the second intermediate product  206 . For example, the sulfur in the first sulfur stream  208  can be liquid sulfur. In some implementations, the first sulfur stream  208  includes additional condensable compounds in liquid form, such as water. 
     The two-stage system  200  can include a sulfur removal unit  220 . The second intermediate product  206  can flow to the sulfur removal unit  220 . The second intermediate product  206  is separated into a second feed stream  212  and a second sulfur stream  214 . The second feed stream  212  includes the hydrogen, the carbon monoxide, and the water from the second intermediate product  206 . In cases where the second intermediate product  206  includes hydrocarbon(s), the second feed stream  212  includes the hydrocarbon(s) from the second intermediate product  206 . In cases where the second intermediate product  206  includes unreacted hydrogen sulfide and/or unreacted carbon dioxide from the first intermediate product  204 , the second feed stream  212  includes the unreacted hydrogen sulfide and/or unreacted carbon dioxide from the second intermediate product  206 . The second sulfur stream  214  includes at least a portion of the sulfur from the second intermediate product  206 . In some cases, the second sulfur stream  214  includes substantially all of the sulfur from the second intermediate product  206 . For example, the second feed stream  212  includes zero sulfur/sulfur-containing compounds or a negligible amount of sulfur/sulfur-containing compounds. In some implementations, separating the second intermediate product  206  into the second feed stream  212  and the second sulfur stream  214  includes cooling the second intermediate product  206 , such that a portion of the second intermediate product  206  is condensed. For example, the sulfur removal unit  220  can include a second condenser (not shown), and the second condenser can cool the second intermediate product  206 , such that a portion of the second intermediate product  206  is condensed and separated from a remaining gaseous portion of the second intermediate product  206 . In such implementations, the condensed portion of the second intermediate product  206  is the second sulfur stream  214 , and the remaining gaseous portion of the second intermediate product  206  is the second intermediate product  212 . For example, the sulfur in the second sulfur stream  214  can be liquid sulfur. In some implementations, the second sulfur stream  214  includes additional condensable compounds in liquid form, such as water. In some implementations, separating the second intermediate product  206  into the second feed stream  212  and the second sulfur stream  214  includes contacting the second intermediate product  206  with a solvent capable of dissolving sulfur compounds (extractive desulfurization). For example, the second intermediate product  206  can be contacted with polyethylene glycol (PEG) to preferentially solvate the sulfur from the second intermediate product  206 . For example, the second intermediate product  206  can be contacted with an organic solvent through a low pressure drop packed column. Liquid sulfur can be extracted from the organic solvent by heating slightly hotter than the melting point of sulfur. In some implementations, separating the second intermediate product  206  into the second feed stream  212  and the second sulfur stream  214  includes contacting the second intermediate product  206  with a solid desulfurization sorbent (for example, a zinc oxide-based sorbent) to absorb, adsorb, or both absorb and adsorb sulfur from the second intermediate product  206 . 
     The two-stage system  200  includes a second catalytic reaction unit  230 . The second catalytic reaction unit  230  includes a second catalytic reactor  231 . The second catalytic reactor  231  can be substantially similar or substantially the same to the catalytic reactor  111  shown in  FIGS.  1 A and  1 B . In some implementations, the second catalytic reactor  231  is substantially similar or substantially the same as the first catalytic reactor  211 . The second catalytic reactor  231  includes a second non-thermal plasma  233  and a second catalyst  235 . The second non-thermal plasma  233  can be substantially similar or substantially the same as the first non-thermal plasma  113  shown in  FIGS.  1 A and  1 B . In some implementations, the second non-thermal plasma  233  is substantially similar or substantially the same as the first non-thermal plasma  213 . The second catalyst  235  can be substantially similar or substantially the same to the catalyst  115  shown in  FIGS.  1 A and  1 B . In some implementations, the second catalyst  235  is substantially similar or substantially the same as the first catalyst  215 . 
     The second feed stream  212  flows to the second catalytic reactor  231 . Within the second catalytic reactor  231 , the second feed stream  212  comes into contact with the second catalyst  235  in the presence of the second non-thermal plasma  233 . The second catalyst  235  is configured to accelerate reaction(s) involving conversion of the hydrogen sulfide and the carbon dioxide in the second feed stream  212 . For example, the second catalyst  235  can accelerate the conversion of hydrogen sulfide into hydrogen (H 2 ) and sulfur (S). For example, the second catalyst  235  can accelerate the conversion of carbon dioxide into carbon monoxide (CO) and oxygen (O 2 ). In some implementations, the second catalyst  235  is configured to shift the pathways of reaction(s) to selectively produce hydrocarbon(s) from carbon dioxide (for example, from the first feed stream  202 ), carbon monoxide (originating from the carbon dioxide from the first feed stream  202 ), and hydrogen (originating from the hydrogen sulfide from the first feed stream  202 ). For example, the second catalyst  235  can accelerate reaction(s) between carbon dioxide and hydrogen to produce hydrocarbon(s) and water. For example, the second catalyst  235  can accelerate reaction(s) between carbon monoxide and hydrogen to produce hydrocarbon(s) and water. In some implementations, the second catalyst  235  is a supported metal-based catalyst. For example, the second catalyst  235  can be a molybdenum-, cadmium-, iron-, cobalt-, nickel-, copper-, zinc-, chromium-, palladium-, or ruthenium-based catalyst supported on an aluminum oxide-, titanium oxide-, silicon oxide-, zirconium oxide-, lanthanum oxide-, cerium oxide-, magnesium oxide-, indium oxide-, or carbon-based support. In some implementations, the second catalyst  235  is a metal oxide-based catalyst. For example, the second catalyst  235  can be a molybdenum oxide-, cadmium oxide-, iron oxide-, cobalt oxide-, nickel oxide-, copper oxide-, zinc oxide-, chromium oxide-, aluminum oxide-, titanium oxide-, zirconium oxide-, gallium oxide-, or magnesium oxide-based catalyst. In some implementations, the second catalyst  235  is a metal sulfide-based catalyst. For example, the second catalyst  235  can be a molybdenum sulfide-, cadmium sulfide-, iron sulfide-, cobalt sulfide-, nickel sulfide-, copper sulfide-, zinc sulfide-, or chromium sulfide-based catalyst. In some implementations, the second catalyst  235  is a zeolite-based catalyst. For example, the second catalyst  235  can be a Zeolite Socony Mobil-5 (ZSM-5)-, titanium silicalite (TS-1)-, silicoaluminophosphate zeolite (SAPO-34)-, UOP zeolite material (UZM)-, mordenite (MOR)-, beta zeolite (BEA)-, or faujasite (FAU)-based catalyst. In some implementations, the second catalyst  235  is substantially similar or substantially the same as the first catalyst  215 . 
     The second non-thermal plasma  233  is a plasma that is not in thermodynamic equilibrium. The second non-thermal plasma  233  is not in thermodynamic equilibrium because the temperature of the electrons in the second non-thermal plasma  233  is much greater than the temperature of the heavy species, such as the ions and the neutrals in the second non-thermal plasma  233 . The second non-thermal plasma  233  is configured to promote dissociation of hydrogen sulfide and carbon dioxide. For example, the second non-thermal plasma  233  can promote dissociation of hydrogen sulfide into hydrogen and sulfur. For example, the second non-thermal plasma  233  can promote dissociation of carbon dioxide into carbon monoxide and oxygen. In some implementations, the second non-thermal plasma  233  is generated by a corona discharge. In some implementations, the second non-thermal plasma  233  is generated by a dielectric barrier discharge. In some implementations, the second non-thermal plasma  233  is generated by a gliding arc discharge. In some implementations, the second non-thermal plasma  233  is generated by an arc discharge. Similar to the non-thermal plasma  113  and the catalyst  115  shown in  FIGS.  1 A and  1 B , the second non-thermal plasma  233  and the second catalyst  235  can operate synergistically within the second catalytic reactor  231 . In some implementations, the second non-thermal plasma  233  is substantially similar or substantially the same as the first non-thermal plasma  213 . 
     In some implementations, an operating temperature within the second catalytic reactor  231  (also referred to as a second reaction temperature) is in a range of from about 20° C. to about 900° C. In some implementations, the second reaction temperature is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, the first reaction temperature within the first catalytic reactor  211  and the second reaction temperature within the second catalytic reactor  231  are substantially the same. In some implementations, an operating pressure within the second catalytic reactor  231  (also referred to as a first reaction pressure) is in a range of from about 1 bar to about 10 bar. In some implementations, the second reaction pressure is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the second reaction pressure is about 1 bar (atmospheric pressure). In some implementations, the first reaction pressure within the first catalytic reactor  211  and the second reaction pressure within the second catalytic reactor  231  are substantially the same. 
     The selection of the first catalyst  215  and the second catalyst  235  can be decided based on various factors. For example, the first catalyst  215  may be selected to be a catalyst that resists sulfur poisoning (such as a supported or unsupported metal sulfide-based catalyst), and the second catalyst  235  may be selected to be a catalyst that better enhances hydrogenation reactions of carbon monoxide and carbon dioxide to produce hydrocarbons in comparison to the first catalyst  215  but may be sensitive to sulfur poisoning (such as a metal-based catalyst). The first reaction temperature and first reaction pressure can be selected to optimize the desired reactions in the first catalytic reactor  211  based on the selected first catalyst  215 . Similarly, the second reaction temperature and second reaction pressure can be selected to optimize the desired reactions in the second catalytic reactor  231  based on the selected second catalyst  235 . 
     Bringing the second feed stream  212  into contact with the second catalyst  235  in the presence of the second non-thermal plasma  233  within the second catalytic reactor  231  at the second reaction temperature and the second reaction pressure results in conversion of the hydrogen sulfide and the carbon dioxide in the second feed stream  212  to produce a product  216 . The product  216  includes hydrocarbon(s). In some implementations, the product  216  includes at least one of methane, ethane, or a hydrocarbon with more carbon atoms than ethane (such as propane and butane). The product  216  can also include additional molecular compounds, such as unreacted carbon dioxide from the second feed stream  212 , carbon monoxide, hydrogen, and water (for example, in the form of water vapor). In some implementations, the product  216  includes zero sulfur/sulfur-containing compounds or a negligible amount of sulfur/sulfur-containing compounds. 
       FIG.  2 B  is a flow chart of an example two-stage method  250  for converting hydrogen sulfide and carbon dioxide into hydrocarbon(s). The two-stage system  200  can implement the method  250 . At block  252  a first feed stream (such as the first feed stream  202 ) is flowed to a first catalytic reactor (such as the first catalytic reactor  211 ). As mentioned previously, the first feed stream  202  includes hydrogen sulfide and carbon dioxide, and the first catalytic reactor  211  includes the first non-thermal plasma  213  and the first catalyst  215 . In some implementations, a volumetric ratio of the hydrogen sulfide to the carbon dioxide in the first feed stream  202  at block  252  is about 1:1. 
     At block  254 , the first feed stream  202  is contacted with the first catalyst  215  in the presence of the first non-thermal plasma  213  within the first catalytic reactor  211 . The first feed stream  202  is contacted with the first catalyst  215  in the presence of the first non-thermal plasma  213  at block  254  at a first reaction temperature that is in a range of from about 20° C. to about 900° C. Contacting the first feed stream  202  with the first catalyst  215  in the presence of the first non-thermal plasma  213  at block  254  results in converting the hydrogen sulfide and the carbon dioxide in the first feed stream  202  to produce a first intermediate product (such as the first intermediate product  204 ). As mentioned previously, the first intermediate product  204  includes a hydrogen, carbon monoxide, water, and sulfur. In some implementations, the first reaction temperature at block  254  is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, an operating pressure within the first catalytic reactor  211  (also referred to as a first reaction pressure) at block  254  is in a range of from about 1 bar to about 10 bar. In some implementations, the first reaction pressure at block  254  is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the first reaction pressure at block  254  is about 1 bar (atmospheric pressure). 
     At block  256 , the first intermediate product  204  is separated into a second intermediate product (such as the second intermediate product  206 ) and a first sulfur stream (such as the first sulfur stream  208 ). As mentioned previously, the first sulfur stream  208  includes at least a portion of the sulfur from the first intermediate product  204 . In some cases, the second intermediate product  206  includes a remaining portion of the sulfur from the first intermediate product  204  that is not separated into the first sulfur stream  208 . For example, the second intermediate product  206  may include trace amounts of sulfur. In some implementations, separating the first intermediate product  204  into the second intermediate product  206  and the first sulfur stream  208  at block  256  includes cooling the first intermediate product  204 , such that a portion of the first intermediate product  204  is condensed. In such implementations, the condensed portion of the first intermediate product  204  is the first sulfur stream  208 , and the remaining gaseous portion of the first intermediate product  204  is the second intermediate product  206 . As mentioned previously, the second intermediate product  206  includes the hydrogen, the carbon monoxide, and the water from the first intermediate product  204 . In cases where the first intermediate product  204  includes hydrocarbon(s), the second intermediate product  206  includes the hydrocarbon(s) from the first intermediate product  204 . For example, the second intermediate product  206  includes methane, ethane, or both methane and ethane. 
     At block  258 , the second intermediate product  206  is separated into a second feed stream (such as the second feed stream  212 ) and a second sulfur stream (such as the second sulfur stream  214 ). As mentioned previously, the second feed stream  212  includes the hydrogen, the carbon monoxide, and the water from the second intermediate product  206 . The second feed stream  212  can also include unreacted carbon dioxide from the first feed stream  202 . As mentioned previously, the second sulfur stream  214  includes at least a portion of the sulfur from the second intermediate product  206 . 
     At block  260 , the second feed stream  212  is flowed to a second catalytic reactor (such as the second catalytic reactor  231 ). As mentioned previously, the second catalytic reactor  231  includes the second non-thermal plasma  233  and the second catalyst  235 . 
     At block  262 , the second feed stream  212  is contacted with the second catalyst  235  in the presence of the second non-thermal plasma  233 . The second feed stream  212  is contacted with the second catalyst  235  in the presence of the second non-thermal plasma  233  within the second catalytic reactor  231  at block  262  at a second reaction temperature that is in a range of from about 20° C. to about 900° C. In some implementations, the second reaction temperature at block  262  is in a range of from about 100° C. to about 300° C., in a range of from about 150° C. to about 250° C., or in a range of from about 150° C. to about 200° C. In some implementations, an operating pressure within the second catalytic reactor  231  (also referred to as a second reaction pressure) at block  262  is in a range of from about 1 bar to about 10 bar. In some implementations, the second reaction pressure at block  262  is in a range of from about 1 bar to about 10 bar or in a range of from about 1 bar to about 5 bar. In some implementations, the second reaction pressure at block  262  is about 1 bar (atmospheric pressure). 
     Contacting the second feed stream  212  with the second catalyst  235  in the presence of the second non-thermal plasma  233  at block  262  results in converting the hydrogen and the carbon monoxide in the second feed stream  212  to produce a product (such as the product  216 ). As mentioned previously, the product  216  includes hydrocarbon(s). In some implementations, the product  216  includes at least one of methane, ethane, or a hydrocarbon with more carbon atoms than ethane (such as propane and butane). The product  216  can also include additional molecular compounds, such as unreacted carbon dioxide from the second feed stream  212 , carbon monoxide, hydrogen, and water (for example, in the form of water vapor). In some implementations, the product  216  includes zero sulfur/sulfur-containing compounds or a negligible amount of sulfur/sulfur-containing compounds. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     As used in this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. 
     As used in this disclosure, the term “about” or “approximately” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. 
     As used in this disclosure, the term “substantially” refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more. 
     Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%, as well as the individual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “X, Y, or Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise. 
     Particular implementations of the subject matter have been described. Other implementations, alterations, and permutations of the described implementations are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. In certain circumstances, multitasking or parallel processing (or a combination of multitasking and parallel processing) may be advantageous and performed as deemed appropriate. 
     Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products. 
     Accordingly, the previously described example implementations do not define or constrain the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure.