Catalytic Performance Of Ethanol Dehydration Reaction Over H-ZSM5 And γ-Al₂O₃ Supported Catalysts

Ethylene production via ethanol dehydration over solid acid catalysts recently attracted much more attentions owing to the advantages of environmental benign, sustainable and mild operation conditions in comparison with hydrocarbon decomposition routine. Aiming of producing ethylene through ethanol dehydration, this thesis modifiedγ-Al₂O₃ and ZSM5 Zeolite using metal oxides dopants or ion exchange method, and then studied the ethanol conversion and the ethylene selectivity over these synthesized catalysts; Effects of operation conditions on the catalytic activity were studied and the on-time spans of several catalysts were measured. Characterization of XRD,TG,NH3-TPD,IR,XPS and BET were used to study the influence of the catalyst structure and surface acid property on the ethanol dehydration reaction.H-ZSM5 molecule sieve was modified by oxides dopants, and effects of oxides content, calcined temperature and calcined time on the prepared catalysts were investigated using the orthogonal experiment method. The results showed that the addition of tungsten oxide enhanced the acidity of the catalyst, and the WO3-doped catalyst showed higher activity of ethanol dehydration; the calcined time affected the catalyst activity obviously among the prepared conditions. The activity test results showed that H-ZSM5 calcined at 500℃for 2 hours with 10wt% WO3 exhibited the best dehydration activity(GHSV=462h-1, Reaction temp.=225℃, both of ethanol conversion and ethylene selectivity reached 100%).γ-Al₂O₃ was the most popular industrial dehydration catalyst. This thesis prepared F- or Cl- modifiedγ-Al₂O₃ catalyst through impregnation of alumina into NH4F and NH4Cl, and the performance of these catalysts was tested for ethanol dehydration reaction. The results showed thatγ-Al₂O₃ impregnated by NH4F and NH4Cl had better catalytic activity, the activity increased as the concentration of NH4Cl solution increased. It changed rarely as the concentration of NH4Cl more than 0.2 mol/L(GHSV=3695h-1,Reaction temp.=350℃, Ethylene yield were 44.8%, 85.0%, 78.0%, 95.4% and 95.7% overγ-Al₂O₃,γ-Al₂O₃ treated by 0.1mol/L NH4F, 0.1mol/L NH4Cl, 0.2mol/L and 0.3mol/L NH4Cl, respectively).