Showing papers by "Abd El-Aziz A. Said published in 1987"
TL;DR: Oxidative coupling of CH4 forming C 2H6 and C2H4 proceeded smoothly upon contact with Na2O2, BaO2 and SrO2 at low temperatures below 673 K, indicating that O22− ions are very reactive for activation of CH 4.
Abstract: Oxidative coupling of CH4 forming C2H6 and C2H4 proceeded smoothly upon contact with Na2O2, BaO2, and SrO2 at low temperatures below 673 K. This indicates that O22− ions are very reactive for activation of CH4. O2− ions contained in the peroxides did not activate CH4.
63 citations
TL;DR: In this article, the contribution of lattice oxygen atoms of Sm2O3 catalysts in the oxidative coupling of methane has been examined by comparing the distributions of products and reactivities of the catalysts observed in the presence and absence of oxygen in the gas phase.
10 citations
TL;DR: In this article, the contribution of lattice oxygen atoms of Sm2O3 catalysts in the oxidative coupling of methane has been examined by comparing the distributions of products and reactivities of the catalysts observed in the presence and absence of oxygen in the gas phase.
Abstract: The contribution of lattice oxygen atoms of Sm2O3 catalysts in the oxidative coupling of methane has been examined by comparing the distributions of products and reactivities of the catalysts observed in the presence and absence of oxygen in the gas phase. The products of the reaction of CH4 with lattice oxygen atoms (without oxygen in the gas phase) at 873–998 K were H2, CO, C2H4 and H2O without a trace of C2H6. The main products H2 and CO were speculated to be produced from HCHO as the reaction intermediate. The amount of C2H4 did not depend on the reaction temperatures. Direct formation of C2H4 from CH4 suggested the formation of CH2=groups on special active sites on the surface. In contrast, the reation of CH4 with the adsorbed oxygens (in the presence of gaseous oxygen) gave C2H6, C2H4, CO2, CO and H2O. The selectivity to C2-compounds (C2H6 + C2H4) was remarkably high compared to that observed for the lattice oxygen atoms. Thus the adsorbed oxygens are better oxidants for oxidative coupling of CH4. The main products observed in the reactions of C2H6 and C2H4 with lattice oxygen atoms were CO, H2 and CH4. CO2 was not produced at temperatures below 973 K. In contrast, the reactions with adsorbed oxygens in the presence of gaseous oxygen produced only CO2, CO and H2O without any H2 or CH4. The reactivity of the adsorbed oxygen for converting CH4 was more than three orders of magnitude greater than that of the lattice oxygen atoms. Thus, oxidative coupling of CH4 in the presence of gaseous oxygen can be ascribed to the role of adsorbed oxygens.