Comparison of four catalysts in the catalytic dehydration of ethanol to ethylene

The aim of this study was to compare the activity and stability of γ-Al2O3, HZSM-5 (Si/Al = 25), silicoaluminophosphate (SAPO-34) and Ni-substituted SAPO-34 (NiAPSO-34) as catalysts in the dehydration of ethanol to ethylene. γ-Al2O3- and HZSM-5 were commercial catalysts. SAPO-34 and NiAPSO-34 molecular sieves had been synthesized with hydrothermal method in the laboratory, characterized with X-ray powder diffraction (XRD), Infrared Spectroscopy (FT-IR), H2 temperature-programmed reduction (H2–TPR) technique and NH3 temperature-programmed desorption (NH3–TPD) technique. The incorporation of Ni2+ into the SAPO-34 framework generated in NiAPSO-34 sample was proved by XRD, FT-IR and H2–TPR techniques. NH3–TPD study had revealed that substitution of Ni2+ for Al3+ in the SAPO-34 framework led to increase the weak and moderately strong acid strength and give rise to weak acid sites. Dehydration of ethanol was carried out over four catalysts and the results showed that conversion of ethanol and selectivity to ethylene decreased in the order HZSM-5 > NiAPSO-34 > SAPO-34 > γ-Al2O3. As to the stability of catalyst, NiAPSO-34 and SAPO-34 were better than other two catalysts. Considering the activity and stability of the four catalysts comprehensively, NiAPSO-34 was the suitable catalyst in the dehydration of ethanol.