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.

An adsorbent separates methanol and other alcohols from gas and liquid oxygenates and hydrocarbon streams with a low silica faujasite (LSX) in a mono-, bi, or tri-cation alkali and/or alkaline-earth metal forms. The LSX has silicon to aluminum ratio from about 0.9 to about 1.15 and an ion exchange degree for each alkali or alkaline-earth metal in the range of about 10 to about 99.9% equiv. The gas streams for treatment include natural gas, individual hydrocarbons, or vaporized alkyl esters of carboxylic acids, or methyl tert-alkyl ethers and their mixtures with hydrocarbons. The liquid streams include liquefied natural gas (LNG), liquefied petroleum gas (LPG), natural gas liquid (NGL), individual hydrocarbons C.sub.3-C.sub.5, and monomers, alkyl esters of carboxylic acids including methyl acetate, methyl, ethyl, butyl acrylates and methacrylate, methyl tert-alkyl ethers including methyl tert-butyl ether (MTBE) and methyl tert-amyl ether (TAME). The adsorbent is especially suited for temperature swing or pressure swing adsorption processes.

A still/stahl column includes a still section, a primary stahl section, the primary stahl section positioned beneath the still section, and a polishing stahl section, the polishing stahl section positioned beneath the primary stahl section. A process also includes feeding a water rich glycol still feed stream to the still section and feeding a stripping gas feed stream to the polishing still section. The process includes withdrawing a reboiler draw stream from the still section and heating the reboiler draw stream in a reboiler to form a reboiler inlet stream. The process includes injecting the reboiler inlet stream into the primary stahl section, stripping water from the water rich glycol with the stripping gas, and withdrawing a still stripping gas stream from a top portion of the still section. A lean glycol polishing discharge stream is withdrawn from a bottom portion of the polishing stahl section.

An absorbent for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide, wherein the absorbent contains an aqueous solution, comprising: a) an amine or a mixture of amines of the general formula (I) wherein R.sup.1 is C.sub.1-C.sub.5-alkyl; R.sup.2 is C.sub.1-C.sub.5-alkyl; R.sup.3 is selected from hydrogen and C.sub.1-C.sub.5-alkyl; x is an integer from 2 to 10; and b) an ether or a mixture of ethers of the general formula (II): R.sup.4—[O—CH.sub.2—CH.sub.2].sub.y—OH; wherein R.sup.4 is C.sub.1-C.sub.5-alkyl; and y is an integer from 2 to 10; wherein R.sup.1 and R.sup.4 are identical; wherein the mass ratio of b) to a) is from 0.08 to 0.5. The absorbent is suitable for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide. The absorbent has a reduced tendency for phase separation at temperatures falling within the usual range of regeneration temperatures for the aqueous amine mixtures and is easily obtainable. ##STR00001##

A method for production of a biodiesel is described herein. The method for production of a biodiesel comprises (a) separating solids from a waste oil composition to provide a clarified oil composition; (b) acidifying the clarified oil composition to produce an acidified oil composition including free fatty acids derived from the waste oil; (c) converting at least a portion of the free fatty acids in the acidified oil composition to glycerides to provide a glyceride composition; and (d) reacting at least a portion of the glycerides in the glyceride composition with methanol to form fatty acid methyl ester to provide a biodiesel composition.

Processes for oligomerizing olefins to produce diesel. The oligomerization zone temperature is controlled to counteract catalyst deactivation caused by coking, by contaminants such as cyclo C5 and/or cyclo C6 hydrocarbons, or both. The temperature is increased in increments to ensure that that the oligomerization zone is producing product at a target product yield with a target product quality, which may be measured by a product cetane number. The target product yield is at least 50 wt % and a target product cetane number may be at least 35.

Disclosed is an improved process for recovering condensable components from a gas stream, in particular, hydrocarbons from a gas stream such as natural gas. The present process uses solid adsorbent media to remove said hydrocarbons wherein the adsorbent media is regenerated in a continuous fashion in a heated continuous counter-current regeneration system, wherein said heated regenerated adsorbent media is cooled prior to reuse.

Described is a process for treatment of a fluid comprising an oxidizable contaminant selected from one or both of a sulfide and a thiol, the process comprising the step of contacting the fluid with a first complex of ferric iron and a polyphosphate to oxidize the oxidizable contaminant and generate a second complex of ferrous ion and the polyphosphate.

The rate of recovery of a purification target gas from a gas purification apparatus that uses a PSA device is improved, and both a high purity and a high recovery rate are achieved with good power efficiency. The present invention is directed to a gas purification method using the PSA method, in which a carbon molecular sieve having a pore volume, at a pore diameter of 0.38 nm or more, of not exceeding 0.05 cm.sup.3/g and a pore volume, at a pore diameter of 0.34 nm, of 0.15 cm.sup.3/g or more, in a pore diameter distribution measured by the MP method is used as an adsorbent, and, in an adsorption step, a miscellaneous gas is adsorbed from a source gas by bringing the source gas into contact with the adsorbent for 10 seconds or more and 6000 seconds or less so as to obtain a concentrated methane.