Dehydration reaction of bio-ethanol to ethylene over modified SAPO catalysts

Mn modified SAPO-11 (Mn-SAPO-11), Zn-SAPO-11, Mn-SAPO-34 and Zn-SAPO-34 were first synthesized with hydrothermal method in the laboratory. Dehydration of ethanol to ethylene over SAPO-11, SAPO-34 and four materials above as catalysts was carried out and Mn-SAPO-34 exhibited the best conversion and selectivity (99.35% and 98.44%, respectively) at 340 °C. The introduction of Mn2+ or Zn2+ into the SAPO channel generated in Mn-SAPO or Zn-SAPO samples was proved by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption. NH3-TPD study revealed that modification of Mn2+ or Zn2+ in the SAPO framework led to increase the weak acid strength and give rise to weak acid sites. The effects of operation parameters, such as loading amount, modification methods, reaction time, reaction temperature, mass space velocity and concentration of ethanol have also been investigated experimentally.