The effect of the PbO loading in the oxidative coupling of methane over PbO/SiO2 catalysts

Abstract

This chapter discusses the effects of the PbO loading and the CH 4 /O 2 ratio on the oxidative coupling of methane (OCM) over PbO/SiO 2 catalysts. At any CH 4 /O 2 ratio, 10% PbO/SiO 2 catalyst was very different from the 2% and 6% PbO/SiO 2 catalysts. It had a very low activity for the oxidation of CH 4 to CO 2 and was selective for the generation of C 2 hydrocarbons. By doubling the amount of catalyst, the amount of reacted methane doubled, while the selectivity remained almost constant. The chapter explains the effect of the PbO loading and the CH 4 /O 2 ratio on the oxidative coupling of methane (OCM) over PbO/SiO 2 catalysts. Special emphasis was made in the interpretation of the product distribution in the gas phase and its relationship with the nature of the catalyst surface. The methodology of the investigation involves incorporation of variable mounts of PbO to the SiO 2 to examine the product distribution for both low and high lead oxide loadings. Temperature-programmed reduction (TPR) reveals the surface changes of PbO. Methane conversion was performed in a conventional fixed-bed continuous flow reactor operated under atmospheric pressure. The reactor consisted of quartz, U type tube of 9 mm internal diameter. The amount of catalyst used for a test run was about 0.25 g that was held in place by quartz wool plugs.