Comparing nickel and cobalt perovskites for steam reforming of glycerol

Catalytic steam reforming of glycerol, a by-product of biodiesel production, to form hydrogen was carried out over nickel and cobalt generated in-situ ex perovskite nano-crystallites, LaNiO3 and LaCoO3, respectively. These materials were prepared using a reverse microemulsion. The glycerol conversion over these materials was modelled as a 1st order reaction and has a lower activation energy (28 kJ/mol) over the sample ex LaNiO3 than the glycerol conversion over the sample ex LaCoO3 (40 kJ/mol). The hydrogen selectivity increases with increasing temperature as expected from a thermodynamic analysis and is higher in the glycerol conversion over LaNiO3 (106.5H-% implying some conversion of water as well) compared to LaCoO3 (80H-%) The obtained distribution of organic product compounds is rationalized based on the higher rate of C-C bond cleavage relative to the rate of C-O bond cleavage for nickel in comparison to cobalt. It is further noted that cobalt ex LaCoO3 is more stable than nickel ex LaNiO3 possibly due to the lower tendency to form carbon deposition over the former sample.