Fast catalytic conversion of diethylene glycol to morpholine over thermally stable Zn promoted Cu-NiO/Al2O3 catalyst prepared via combustion approach

摘要

Highly active and thermally stable M-Cu-NiO/Al2O3 catalysts (M represents Al/La/Mg/Zn) were prepared by combustion method and applied in diethylene glycol (DEG) conversion to morpholine (Mp). Copper species preserved relatively small crystallite size (19 nm), high dispersion (40.3%) and high surface area (272 m(2)/g) in M-Cu-NiO/Al2O3 catalysts. High dispersion and intimate contact of copper with Al and La/Mg/Zn synergistically enhanced DEG conversion and Mp selectivity. Addition of promoter i.e. La, Mg, or Zn facilitated the formation of surface defects and isolated species to inhibit migration and aggregation of Cu moities during calcination as well as in high temperature DEG conversion reaction. Compared to other catalysts, Zn-Cu-NiO/Al2O3 combusted catalyst exhibited the highest DEG conversion of 99% (55% higher than impregnated catlayst) and Mp selectivity (95%), even at a high DEG space velocity of 0.8 mL g(-1) h(-1). Moreover, Zn-Cu-NiO/Al2O3 exhibited excellent thermal stability i.e. less than 2% decrease in initial DEG conversion after 80 h of reaction. The catalysts followed an overall activity order of: Zn-Cu-NiO/Al2O3 Mg-Cu-NiO/Al2O3 La-Cu-NiO/Al2O3. The catalysts were characterized by XRD, BET surface area, SEM and XPS techniques. The present study, credited to its cost-effective nature, simplicity of operation and high efficiency, can be effectively applied for DEG conversion to Mp on industrial level.