GB670700A - Treatment of acid hydrocarbon gas mixtures - Google Patents

Abstract

Gaseous hydrocarbons such as natural and refinery gases are freed from acidic impurities, viz. H2S,SO2 and CO2 by contacting with a solution containing a liquid "aliphatic" amine, water, and an organic water soluble diluent of lower viscosity than the amine, and heating and regenerating the rich solution for re-use. "Aliphatic" amines are defined as those having the NH2 attached to CH2 which may be attached to aliphatic groups or to a saturated or unsaturated ring as in benzylamine. Primary, secondary, and tertiary as well as mono-, di-and tri-amines are included. Ethanolamines are particularly suitable. Polyhydric alcohols or glycols or ethers thereof may also be included in the solutions. The diluent, which must be selected to have a lower viscosity than the amine or polyhydric alcohol or ether if present and preferably has mutual solubility therewith, may be a monohydric aliphatic alcohol, preferably of 4 or less carbon atoms, a phenyl substituted derivative thereof, e.g. benzyl or phenylethyl alcohol, an aromatic, alicyclic or heterocyclic monohydric alcohol, e.g. furfuryl or tetrahydrofurfuryl alcohol, a monoether of a polyhydric alcohol or glycol, e.g. carbitols, and "Cellosolves" (Registered Trade Mark), a multiple ether of a polyhydric alcohol such as dimethoxytetraglycol, or an aromatic or other cyclic nitrogen base such as aniline or pyridine. The viscosities of typical solutions containing mono- or di-ethanolamine, water, and diethylene glycol, both with and without butyl carbitol as diluent are given. The percentage of diluent is preferably sufficient to give a viscosity of the rich solution of below 60 centistokes at 91 DEG F. with solutions containing monoethanolamine and diethylene glycol, and below 90 centistokes where diethanolamine replaces mono. The diluent preferably boils at 350-550 DEG F. Typical solutions are 60 per cent benzyl alcohol, 35 per cent diethanolamine, 5 per cent water; and 20 per cent monoethanolamine, 25 per cent diethylene glycol, 50 per cent butyl carbitol, 5 per cent water. Gas to be purified may pass up through an absorber counter-current to the solution, and the enriched absorbent passed to a vent tank, from which liberated gas may pass to the base of a still and aid in stripping the down-flowing absorbent. The extent of dehydration is controlled by regulating the temperature. U.S.A. Specification 2,177,068 is referred to.