Physically mixed ZnO and skeletal NiMo for one-pot reforming-hydrogenolysis of glycerol to 1,2-propanediol

Abstract

The one-pot aqueous phase reforming (APR) and hydrogenolysis of glycerol to 1,2-propanediol (PDO) was catalyzed by physically mixed skeletal NiMo and zinc oxide catalysts in a continuous flow fixed-bed reactor without the aid of added H2. The skeletal NiMo catalyst alone is highly active towards glycerol but the selectivity for 1,2-PDO is only moderate. Physically mixing of MgO, SiO2, Al2O3, HZSM-5, TiO2, ZrO2, or CeO2 as a cocatalyst with skeletal NiMo was detrimental to the conversion of glycerol and yield of 1,2-PDO. However, physically mixing with ZnO gave an advantageous promoting effect on both the catalytic activity and selectivity for 1,2-PDO, and gave a 1,2-PDO yield of 52.0%, which is higher than that obtained with noble metal catalysts for the APR-hydrogenolysis of glycerol. The synergistic effect between physically mixed ZnO and skeletal NiMo was attributed to in situ enhancement of the Lewis acidity of ZnO by chemisorbed CO2 from the APR of glycerol on skeletal NiMo, which benefited both the dehydration of glycerol to acetol on ZnO and the hydrogenation of acetol to 1,2-PDO on skeletal NiMo. 以骨架NiMo以及与氧化物物理混合, 考察了其在连续固定床反应器中无外加氢气条件下的丙三醇一锅法重整–氢解制1,2-丙二醇(1,2-PDO)的性能. 研究发现, 骨架NiMo自身催化活性高, 但对1,2-PDO的选择性一般. 当将其与MgO, SiO2, Al2O3, HZSM-5, TiO2, ZrO2或CeO2机械混合时, 丙三醇转化率和1,2-PDO选择性均发生下降. 但当与ZnO物理混合时, 催化活性和选择性均有所提高, 1,2-PDO得率可达52.0%, 优于贵金属催化剂在该一锅法反应中得到的结果. 物理混合的ZnO与骨架NiMo之间这种独特的协同作用, 归因于重整过程中产生的CO2在ZnO上发生化学吸附, 原位增强了ZnO的路易斯酸性. 这不仅促进了丙三醇在ZnO上脱水生成中间产物丙酮醇, 也促进了丙酮醇在骨架NiMo上加氢生成1,2-PDO.