Cobalt-lanthanum catalyst precursors for ammonia synthesis: determination of calcination temperature and storage conditions

A thermal decomposition of a cobalt-lanthanum catalyst precursor containing a mixture of cobalt and lanthanum compounds obtained by co-precipitation were studied using thermal analysis coupled with mass spectrometry (TG-MS). Studies revealed that the calcination in air at 500°C is sufficient to transform the obtained cobalt precipitate into Co₃O₄, but it leads to only partial decomposition of lanthanum precipitate. In order to obtain Co/La catalyst precursor containing La₂O₃ the calcination in air at the temperature about 800°C is required. However, it is unfavorable from the point of view of textural properties of the catalyst precursor. A strong effect of storage conditions on the phase composition of the studied cobalt-lanthanum catalyst precursor, caused by the formation of lanthanum hydroxide and lanthanum carbonates from La₂O₃ when contacting with air, was observed.