"Typically, such feed streams would represent over about 90 mole percent, or more typically 92 to 95 mole percent or greater, of generally equal amounts of methane and carbon dioxide in the feed stream with lesser amounts of impurities, such as nitrogen and oxygen, and minor amounts of hydrogen, carbon monoxide, hydrocarbons, oxygenated hydrocarbons like ketones, halogenated hydrocarbons, together" . . . . .