Improved performance of magnetically recoverable Ce-promoted Ni/Al2O3 catalysts for aqueous-phase hydrogenolysis of sorbitol to glycols

The addition of cerium into Ni/Al2O3 catalysts afforded a remarkable promoting effect on catalytic performance of aqueous-phase hydrogenolysis of sorbitol to produce glycols (e.g., 1,2-propylene glycol and ethylene glycol). This effect was observed whether the catalysts were prepared through deposition–precipitation (DP) or co-precipitation (CP) methods. However, the Ce–Ni/Al2O3-DP catalyst went through rapid deactivation during the consecutive recycles. The Ce–Ni/Al2O3-CP catalyst was recovered easily by magnetic separation and reused over ten times. At a temperature of 513 K and pressure of 7.0 MPa, the Ce–Ni/Al2O3-CP catalyst maintained sorbitol conversion at above 90% and selectivity to glycols at 55–60% for 12 h. Characteristic studies indicate that the addition of cerium to the Ni/Al2O3 catalysts slightly lowered the reduction temperature of nickel oxide but considerably enhanced the H2-chemisorption amount. Furthermore, the co-precipitation method was conducive for preparing the catalyst with high thermal stability, which was shown by 20% Ni/Al2O3-CP being more stable in structure than 20% Ni/Al2O3-DP under higher temperatures. The catalyst deactivation was due to the agglomeration of Ni nanoparticles during hydrogenolysis process in aqueous-phase.