Influence of calcination temperature on the performance of Ni/La(III) catalyst in the hydrogenolysis of sorbitol to low-carbon glycols

Nanorod-shaped La(OH)₃ support was prepared by hydrothermal method, over which the supported Ni/La(III) catalysts were obtained through wet impregnation method; the influence of calcination temperature on the performance of Ni/La(III) catalyst in the hydrogenolysis of sorbitol to low-carbon glycols was then investigated by means of XRD, SEM/EDS, BET, H₂-TPR-MS, CO/CO₂-TPD-MS, ICP-AES and TG. The results revealed that the Ni/La(III) catalysts are highly active for sorbitol hydrogenolysis; the yield of low-carbon glycols reaches 53% after reaction at 220℃ and 4 MPa H₂ for 1.5 h. The catalyst calcined at low temperature (500℃) is mainly in the form of NiO/La₂O₂CO₃, which may transform into La₂NiO₄-La₂O₃ with the increase of calcination temperature. The basicity is a crucial factor for the hydrogenolysis activity; high calcionation temperature may enhance the basicity of the catalysts and then improve their hydrogenolysis activity, whereas the calcination temperature has little effect on the products selectivity. However, NiO/La₂O₂CO₃ exhibits better hydrothermal stability than La₂NiO₄-La₂O₃ for sorbitol hydrogenolysis. The deactivation of catalysts can be attributed to the separation of active Ni particles from the support and the agglomeration of the active species, which may reduce the amount of the active metal sites and destroy the catalyst structure.