Feasibility of Ethylene Synthesis via Oxidative Coupling of Methane

摘要: Abstract Shortages of prime feedstocks for ethylene manufacture have spawned numerous attempts to use alternate raw materials. Methane 1s one such material that the most abundant component natural gas, usually comprising up ∼90 mole % hydrocarbon fraction. Thus, methane represents a considerably more source than ethane/propane, two widely used Dehydrogenative coupling requires temperatures in excess 800°C practical conversions along with high endothermic heat 53 Kcal/g mol – quite difficult generate at >800°C. Oxidative removes thermodynamic barrier straight dehydrogenative and heat-of-reaction problem. The primary objective early Union Carbide study was uncover selective catalysts form C 2 's, principally ethylene. Synthesis (and some ethane) has been demonstrated by catalytic oxidative atmospheric pressure 500–1000°C. A great number metal oxides, supported on an alpha-alumina support, screened activity selectivity normal, concurrent feeding mode reactants, as well as, sequential or feed programming mode. experiments gave low selectivities 0–20%, while ∼50%. In latter case, however, stainless steel reactor became catalytically active burning carbon oxides. Although work reported here, quartz found be inert. -formation were oxides Mn, Pb, Sn, Sb, Bi, Ti, Cd, Li, Mg, Zn, Zr, Mo, Fe, Cr, W, Cu, Ag, Pt, Ce, V, B Al showed little no activity. -forming Pt Ce may due secondary s walls. This also makes it quantify metals seem exhibit common characteristic: they can cycle between least oxidation states. there are differences formation, correlation seems exist free-energy changes possible mechanism from is proposed. There other reports recently (for example, several patents issued Jones, Leonard, Sofranko U.S. 4, 443,644, -645, -647, -648, -649) synthesis 2+ hydrocarbons over Mn 3 O 4 , Sb PbO, GeO . Samarium oxide “as is”, after alkali modification Otsuka, et.al. even catalyst previously known, However, all systems to-date require either frequent regenerations unsteady state operation. feasibility process shall depend on: (I) higher activity/selectivity permit lower temperature operation range 400–600°C. Such minimize potential loss (II) scaleability though advantage separating air effluent. These hurdles must overcome before this conceptually attractive route considered viable alternative conventional routes.