NOVELTY - Oxidative coupling of methane (OCM) system comprises: (a) an OCM subsystem that (i) takes as input a feed stream comprising methane (CH4) and a feed stream comprising an oxidizing agent, and (ii) generates from the methane and the oxidizing agent a product stream comprising C2+ compounds and non-C2+ impurities; (b) separations subsystem downstream of, and fluidically coupled to, the OCM subsystem; and (c) an olefin to liquids subsystem downstream of the OCM subsystem.    USE - The OCM system and methods are useful for producing hydrocarbon products and liquid hydrocarbon products; for generating hydrocarbons; for generating catalyst; and for preventing coke formation on methanation catalyst in OCM and ETL process (all claimed).    ADVANTAGE - Efficient and commercially viable systems and methods are provided for converting ethylene to higher molecular weight hydrocarbons, including gasoline, diesel fuel, jet fuel, and aromatic chemicals.    DETAILED DESCRIPTION - Oxidative coupling of methane (OCM) system comprises: (a) an OCM subsystem that (i) takes as input a feed stream comprising methane (CH4) and a feed stream comprising an oxidizing agent, and (ii) generates from the methane and the oxidizing agent a product stream comprising C2+ compounds and non-C2+ impurities; (b) separations subsystem downstream of, and fluidically coupled to, the OCM subsystem, where the separations subsystem comprises a first heat exchanger, a de-methanizer unit downstream of the first heat exchanger, and a second heat exchanger downstream of the de-methanizer unit, where (i) the first heat exchanger cools the product stream, (ii) the de-methanizer unit accepts the product stream from the first heat exchanger and generates an overhead stream comprising portion of the non-C2+ impurities, and (iii) portion of the overhead stream is cooled in the second heat exchanger and is subsequently directed to the first heat exchanger to cool the product stream; and (c) an olefin to liquids subsystem downstream of the OCM subsystem, where the olefin to liquids subsystem is configured to generate higher hydrocarbon(s) from one or more olefins included in the C2+ compounds. INDEPENDENT CLAIMS are included for:    (1) a method of producing hydrocarbon products;    (2) a method of producing liquid hydrocarbon products;    (3) a processing system comprising: (a) OCM reactor system comprising an OCM catalyst, the OCM reactor system being fluidly connected at an input to a source of methane and a source of oxidant, where the OCM reactor system (i) takes as input the methane and the oxidant and (ii) generates from the methane and the oxidant a product stream comprising C2+ compounds; (b) at least a first catalytic ethylene conversion reactor systems and a second catalytic ethylene conversion reactor system downstream of the OCM reactor system, the first catalytic ethylene reactor system being configured to convert ethylene to a first higher hydrocarbon, and the second catalytic ethylene reactor system being configured to convert ethylene to a second higher hydrocarbon different from the first higher hydrocarbon; and (c) a selective coupling unit between the OCM reactor system and the first and second catalytic ethylene reactor systems, which selective coupling unit is configured to selectively direct portion of the product gas to each of the first and second catalytic ethylene reactor systems;    (4) a chemical production system, comprising: an OCM subsystem that includes an OCM reactor, where the OCM reactor (i) takes as input a feed stream comprising CH4 and a feed stream comprising an oxidizing agent and (ii) generates from the methane and the oxidizing agent C2+ compounds and non-C2+ impurities; and an ethylene-to -liquids (ETL) subsystem downstream of the OCM subsystem that includes an ETL reactor, where the ETL reactor converts portion of the C2+ compounds to a product stream comprising C3+ compounds, where C3+ compounds are generated at a single pass conversion of at least about 40%;    (5) a method for generating hydrocarbons;    (6) a method for generating a catalyst;    (7) a system for generating hydrocarbons, comprising ETL unit comprising one or more ETL reactors, where an individual ETL reactor accepts ethylene from a non-ETL process and generates a product stream comprising higher hydrocarbons through an oligomerization process, where at least some of the higher hydrocarbons are in liquid form at room temperature and atmospheric pressure; and separations unit downstream of, and fluidically coupled to, the ETL unit, where the separations unit separates the product stream into individual streams, each comprising a subset of the higher hydrocarbons;    (8) a catalyst for the conversion of ethylene to liquid hydrocarbon fuels, comprising: (a) a ZSM-5 base material; (b) a binder material; and (c) a dopant material; where the catalyst has a cycle lifetime of at least about 1 week when in contact with up to about 100 parts per million (ppm) acetylene, and where the catalyst has a replacement lifetime of at least about 1 year when in contact with up to about 100 ppm acetylene;    (9) a catalyst for hydrogenation of acetylene in OCM and ETL process comprising elemental metal, where the catalyst is capable of decreasing the concentration of acetylene to less than about 100 ppm in an OCM effluent prior to flowing the OCM effluent into an ETL process;    (10) a catalyst for converting carbon monoxide (CO) and/or carbon dioxide (CO2) into CH4 in OCM and ETL process, where the catalyst comprises elemental metal, and where the catalyst converts CO and/or CO2 into CH4 at a selectivity for the formation of methane that is at least about 10-fold greater than the selectivity of the catalyst for formation of coke in an ETL effluent; and    (11) a method for preventing coke formation on a methanation catalyst in OCM and ETL process.