The Research Of Bio-ethanol Dehydration To Ethylene Over Modified HZSM-5 Molecule Sieve Catalyst

Petroleum resource is unrenewable and drying up gradually, which brings great challenge for the ethylene industry, so it should explore other raw materials to compensate the petroleum resource.But ethylene can produced by ethanol dehydration. Ethanol can produced from large amounts of biomass by fermentation, so it is a good chance for the technology that ethanol dehydration to ethylene to develop. So it is quite promising for ethylene get from ethanol that can gain from biomass by fermentation. In this paper, I have researched the condition of modification and got the ZnMnZSM-5 catalyst with benign activity. The activity of modified catalyst was tested with ethanol and bio-ethanol, it showed good catalytic activity, and optimized the condition of modification and dehydration. Under the optimum dehydration technology condition, detected the life time of ZnMnZSM-5 catalyst. At last, did some tests about dynamics for ethanol dehydration.This technics has some advantages, such as save energy, equipment can be controlled easily and so on, it is base for the technology of bio-ethanol dehydration to ethylene and industrialisation, so it is an important direction for biomass industry.The results of catalyst modification showed that when the Si/Al ratio of HZSM-5 was 25, modified temperature was 60°C, the concentrations of Zn(NO3)2 and MnCl2 were 2% and 4% respectivly, the modified time was 1.5h, and the calcination temperature was 550°C, the catalytic activity of modified HZSM-5 was better. The conversion rate of material and selectivity of product were over 99% and 93% respectively.The results of dehydration condition that when the concentration of ethanol was 5% 95%, the Si/Al ratio of HZSM-5 was 25, WHSV were 2.3lh₁ and 2.64h-1 respectively, reaction temperature was 250°C, carrier gas velocity was 0.5L/min, both of the conversion rate and selectivity were over 99%. After used 72h consecutively, the catalytic activity decreased about 50%, it also decreased after used five times. It also showed benign catalytic activity after calined.The HZSM-5 and ZnMnZSM-5 were characterized by XRD, BET, SEM and FT-IR techniques. The result indicated that Zn2+ and Mn2+ were located in the zeolite frame, and the crystal structure of the modified zeolites were not changed, in addition B acid sites was decreased slightly and L acid sites was increased greatly,which were favorable to catalytic dehydration of ethanol to ethylene. The deactived slightly ZnMnZSM-5 was characterized by NH3-TPD and IR techniques, it showed that the strong acidity bites and weak acdity bites were decreased, and the carbonaceous material may be polyethylene and esters. The results of macro-dynamics demonstrated that the dynamic equations were different during 230-240°C and 250-270°C, the macro-dynamics equations are as follows respectively:Rm = 7.31exp(3.759xl04/T)C1.2m, Rm = 7.31exp(3.759xl04/T)CO.6m. and the average active energy was -312.5KJ/mol .maybe it happened two steps reaction in the low temperature zone, but it dehydrates directly in high terperature zone, the mechanism of dehydration on ZnMnZSM-5 will be analyzed furtherly.