Acid gas compounds are removed from a process gas such as, for example, syngas or natural gas, by flowing a feed gas into a desulfurization unit to remove a substantial fraction of sulfur compounds from the feed gas and flowing the resulting desulfurized gas into a CO.sub.2 removal unit to remove a substantial fraction of CO.sub.2 from the desulfurized gas.

A method for production of renewable natural gas (RNG) from biogases containing volatile organic compounds (VOCs) combines temperature swing adsorption (TSA) for removal of VOCs, a form of pressure swing adsorption (PSA) for nitrogen separation, and membrane gas separation technology for carbon dioxide removal. TSA systems may improve removal of VOCs relative to PSA systems, may reduce RNG plant operating costs, and may simplify RNG plant operation. Methane recovery may be improved by using equilibrium PSA systems instead of dynamic PSA systems for methane separation.

A natural gas refining apparatus including a first separation membrane unit including a first separation membrane; and a second separation membrane unit provided in a subsequent stage of the first separation membrane unit. The second separation membrane unit includes a second separation membrane that allows an amine solution to circulate through the second separation membrane unit, and the natural gas refining apparatus refines raw natural gas containing CO.sub.2 by passing the raw natural gas through the first and second separation membrane units, separating CO.sub.2-rich gas with the first and second separation membranes, and absorbing CO.sub.2 with the amine solution circulating through the second separation membrane unit.

A composition for scavenging hydrogen sulphide and/or mercaptans in hydrocarbon streams includes a H2S scavenger selected from oxazolidine compounds, triazine and metal-based carboxylate compounds, and a synergistic additive allowing boosting the effect of the H2S scavenger compound.

Disclosed is an apparatus and method of preparing synthetic fuel using natural gas extracted from a stranded gas field on land or at sea as a raw material through a compact GTL process or a GTL-FPSO process. A parallel-type gas purification unit for controlling a molar ratio of synthetic gas and a concentration of carbon dioxide in the synthetic gas, in which a CO.sub.2 separation device and a bypass unit are disposed in parallel, is provided and, thus, the gas purification unit may prepare the synthetic gas by a steam carbon dioxide reforming (SCR) reaction using natural gas having different CO.sub.2 contents of various stranded gas fields and then supply the synthetic gas having an optimum composition suitable for a Fischer-Tropsch synthesis.

An integrated refinery process for removing mercaptans from a hydrocarbon stream containing mercaptans and converting by-product disulfide oil to useful products. The process includes introducing the hydrocarbon stream containing mercaptans into an extraction vessel containing an alkaline solution and passing the hydrocarbon stream through an extraction section of the extraction vessel which includes one or more liquid-liquid contacting decks for reaction to convert the mercaptans to alkali metal alkanethiolates. Further, the process includes withdrawing a hydrocarbon product stream free of mercaptans from the extraction vessel and recovering spent caustic containing alkali metal alkanethiolates from the extraction vessel. Additionally, the process includes subjecting the spent caustic containing alkali metal alkanethiolates to air oxidation to produce a by-product stream containing disulfide oils (DSO) and sulfides and processing the by-product stream in a steam cracking unit to produce a DSO free product stream.

There is an absorbent mixture usable for the removal of sour gases from gas mixtures. The mixture has at least one organic base having a pK.sub.b (in water) less than or equal to 3.2; at least one alcoholic solvent of general formula R(OH).sub.n having a boiling temperature above or equal to 100° C. at ambient pressure, wherein R is a linear or branched saturated alkyl group having a number of carbon atoms between 2 and 20 and n is a whole number varying between 1 and 20; an aprotic polar solvent having a dielectric constant E at 25° C. greater than or equal to 30, a viscosity μ at 25° C. less than or equal to 14 cP, preferably less than or equal to 12 cP; and a boiling temperature at normal pressure equal to or above 130° C. There is also a process for the removal of sour gases using the absorbent mixture.

A fuel cell system including a hydrocarbon fuel stream including a sulfur compound; a passive sorbent bed including a selective sulfur sorbent configured to remove the sulfur compound from the hydrocarbon fuel stream; a SCSO reactor, and an active sorbent bed comprising a sulfur oxide sorbent, wherein the active sorbet bed is configured to receive an effluent stream from the SCSO reactor and remove at least a portion of the sulfur oxides via the sulfur oxide sorbent. During start-up of the fuel cell system, the hydrocarbon fuel stream may be directed along a first flow pathway through the passive sorbent bed to remove the sulfur compound from the fuel stream during a first time period and then directed along a second flow pathway during a second time period that does not pass through the passive sorbent bed, e.g., once the SCSO reactor/active sorbent bed have reached operating temperature.

Disclosed is a process for regenerating a hybrid solvent used to remove contaminants from a fluid stream and to provide an improved yield of purified fluid. Said process comprises at least one purification unit (12) and at least one regeneration unit (40) wherein condensed water 62 from the regeneration unit is recycled back into the purification unit and none of the condensed water is reintroduced into the regeneration unit.

Treatment of hydrocarbon streams, and in one non-limiting embodiment refinery distillates, with high pH aqueous reducing agents, such as borohydride, results in reduction of the sulfur compounds such as disulfides, mercaptans and thioethers that are present to give easily removed sulfides. The treatment converts the original sulfur compounds into hydrogen sulfide or low molecular weight mercaptans that can be extracted from the distillate with caustic solutions, hydrogen sulfide or mercaptan scavengers, solid absorbents such as clay or activated carbon or liquid absorbents such as amine-aldehyde condensates and/or aqueous aldehydes.