Preparation of mesostructured barium sulfate and its application in methane activation

Barium sulfate with lamellar and tubular microstructure was developed through a surfactant templating route under different synthesis conditions. Lamellar barium sulfate was synthesized through direct combination of Ba2+ and SO42− in an aqueous solution containing sodium dodecyl benzene sulfonate (SDBS). Agglomerate barium sulfate nanotubes were obtained by the reaction of Ba2+ and CaSO4 in the SDBS aqueous solution. Preparation of regular single barium sulfate nanotubes was achieved by the controlled hydrolysis of dimethyl sulfate in an aqueous solution containing Ba2+ and SDBS. As revealed by transmission electron microscopy characterization, the tube wall thickness was 7–8 nm, and the inner diameter was about 6 nm. When such mesostructured barium sulfate was loaded with VOSO4 and sulfuric acid (100%), it performed excellently in catalyzing oxidative conversion of methane to methanol using molecular oxygen. The conversion proceeded at a relatively lower temperature (under 250 °C) than over general solid catalysts, and the selectivity to methanol remained high when methane conversion increased to an acceptable level. When the reaction proceeded stably, the one-pass conversion of methane was about 30%, and the selectivity to methanol could reach 50%.