Novel Au/La1-xSrxMnO3 and Au/La1-xSrxCrO3 composites: catalytic activity for propane partial oxidation and reforming

This work describes the low temperature synthesis of novel nanosized Au/La1-xSrxMnO3 (x ~ 0.4) and Au/La0.85Sr0.15CrO3 composites and investigates their potential as anodic catalysts for propane reforming. The pristine La1-xSrxMnO3 (x ~ 0.4) and La0.85Sr0.15CrO3 were prepared by a modified nitrate–citrate Pechini method and the process was optimized in order to obtain high surface area perovskite powders. These materials with nanometric or sub-micrometric grain size have been isolated as a single-phase and used for the preparation of the composite. A homogenous distribution of nanosized gold particle (<5 nm) was deposited on the perovskite powders surface by an ultrasound-driven synthesis. The catalytic behavior of these inorganic composites was investigated for the following propane reforming processes, i.e. steam reforming, partial oxidation and autothermal reforming. Good propane conversions in the partial oxidation conditions were detected for sub-hundred nanometer La1-xSrxMnO3 perovskite and the role of gold as a promoter for this process was assessed. In particular, nanosized gold on La1-xSrxMnO3 resulted in an increase of the perovskite stability under all catalysis conditions. The influence of water steam in the feeding gas stream was also tested. The low influence of gold presence in catalytic tests of Au/La0.85Sr0.15CrO3 suggested poor gold catalytic activity in the tested conditions but a presumable role of gold on the stabilization of the Mn mixed oxidation state in the case of the manganites.