Nano-lanthanum Oxyhalide Prepared by Nonaqueous Sol-Gel for Oxidative Coupling of Methane

Abstract

LaOX (X = Cl, Br) nanoparticles with tetragonal crystal structure were successfully prepared via sol-gel approach with non-aqueous solvents. Characterizations by X-ray powder diffraction and scanning electronic microscopy show that the LaOX nanoparticles are regularly in shape and highly uniform in size with an average diameter of about 47 nm. For oxidative coupling of methane (OCM), the nanosize LaOX catalysts have higher methane conversion and C(2) selectivity than the LaOX catalysts with conventional size and show good stability in activity and selectivity during the catalyst life test at 650 degrees C. At conventional size, the methane conversion and C(2) selectivity for OCM over the LaOBr catalyst are higher than that over the LaOCl catalyst, and at nanosize, there is not so much difference in methane conversion between LaOBr and LaOCl. However, the C(2) selectivity for OCM reaction over LaoBr is significantly higher than that over LaOCl, especially at low temperature.