Studies On The Catalytic Dehydration Of Bio-ethanol To Ethylene

The technical level of ethylene is a significant symbol for the level of a country’schemical industry. Generally, the naphtha cracking method is used to be the industrialmethod to produce ethylene at home or at abroad. However, along with theincreasingly global demand but gradually shortage of energy and resources, theprocess will face with sharp challenges. It has been received increasing attention forthe process which produces ethylene by the catalyzed dehydration method using thebio-ethanol obtained by fermentation of biomass as reactor.This project intends todevelop a series of high performance catalysts which use low concentration ethanol asreactor at low temperature. And we have made achievements at following researchaspects:(1)Develop a series of high performance catalyst.Successfully achieve highconversion of ethanol and high yield of ethylene at temperature low than290℃.Studythe influence factors of the reaction. The optimal catalysts are listed below: forFe-HZSM-5(25),the conversion of ethanol can reach to99.74%,and the yield ofethylene can reach to98.52%in the condition of260℃and Liquid-hourly spacevelocity (LHSV)0.47h-1; for Zr-HZSM-5(40),the conversion of ethanol can reach to100%,and the yield of ethylene can reach to95.11%in the condition of290℃andLiquid-hourly space velocity(LHSV)2.53h-1.(2)Use FT-IR, XRD and NH3-TPD techniques to characterize catalysts. Fortransition metal modified-ZSM-5catalysts, the metal ions were highly disperse on thesurface of zeolite or incorporation into the framework of zeolite by replace aluminum;the introduction of amorphous Si-Al sol can reconstruct the surface structure ofzeolites and repair the defects of surface of zeolites;Compared to parent H-ZSM-5(25),various metal modified–ZSM-5(25) catalysts had tiny-change of weak acid strengthand quantity, but exhibited weaker strong acid sites strength and less strong acid sitesquantity. The insertion of Fe3+and Zr4+can effectively modified the Br nsted acid ofcatalysts, which was benefit for the high yield of ethylene.(3)Amplified experiment was carried out in an amplificatory fixed bed usingFe-ZSM-5(25) as catalyst. At the conditions of260℃and LHSV0.47h-1,an high as99.43-99.90%conversion of ethanol and an as high as98.91%-99.40%yield ofethylene can be reached and remain unchanged for more than2500h oftime-on-steam. (4)Use FT-IR, XRD, AAS, NH3-TPD, O2-TPO and GC-MS to characterizede-active catalysts. The main reasons caused de-activation were both an aromatic typeof coke occupied acid sites and a loss of Fe3+.The regeneration of catalyst can beobtained by a proper complement of Fe3+after coke combust at650℃. Regeneratedcatalyst still has a good activity and stability and an as high as98.35%-99.02%ofethylene yield can be reached again.To sum up, a series of new efficient catalysts were invented which had manyadvantages:(1) a high ethylene yield can be reached for more than2550oftime-on-steam under mild conditions (2) the activity of de-active catalysts can beeasily restored. These results provide scientific evidences to further design anddevelopment of more excellent catalysts and to achieve industrialization.