Sol–Gel Preparation of Samaria Catalysts for the Oxidative Coupling of Methane

Abstract

A new sol–gel synthesis route for alumina–samaria mixed aero- and xerogel catalysts based on the so-called epoxide addition method and the use of these systems as catalysts for the oxidative coupling of methane (OCM) is reported. As precursors simple chloride or nitrate salts can be used. The mesoporous materials are X-ray amorphous even after calcination to 800 °C and show an intimate mixing of Al and Sm on the nanoscale. In the case of the xerogels derived from chlorides, C2 yields comparable to pure samaria can be achieved under OCM reaction conditions with 100 % O2 conversion. Even at lower O2 conversions the activity of the xerogel is competitive with a pure samaria reference catalyst taking the lower samaria content of 20 % into account. Accordingly, the approach is suitable to reduce the costs associated with the rare earth oxide. In addition to the preparation of aerogel and xerogel particles, the presented synthesis also allows the fabrication of xerogel films which can be coated on a suitable (monolithic) support. First results of such films are presented.