Studies On Catalysts And Technology For Catalytic Dehydration Of Ethanol To Ethylene And Aromatics

As the important staple chemicals, Ethylene and arenes are mostly produced from petroleum, coal and natural gas in industry, which are not reproducible going with the pollutions to environment. Therefore it is so necessary to develop green ways to produce ethylene and arenes, while the biomass as a reproducible resource attracts more and more attention. During the exploitation of biomass, bio-ethanol for its broad feed and cheapness are paid close attention to in academia and industry. According to literatures reported, ethylene can be obtained from ethanol by suited catalysts, but there are some common disadvantages such as rigorous reaction condition, low yield of ethylene and short using cycle of catalysts. That aromatic hydrocarbons directly produced from ethanol hasn't been reported by recent. In our research, series new catalysts have been prepared showing excellent performance in the production of ethylene and aromatic hydrocarbons from ethylene. The main progress was as follows:(1)The catalysts were prepared through the modifying of HZSM-5 powder with the Fe,Zn,Zr,La ions and/or amorphous Si-Al gel. The factors during preparation of catalysts and catalytic conversion of ethanol to ethylene and arenes had been investigated. In the catalytic dehydration of ethanol to ethylene, it profited the high yield of ethylene at lower temperature with lower feed input speed or at higher temperature with higher feed input speed over the catalysts with lower Si/Al ratio, while over the catalysts with higher Si/Al ratio, the reaction needed to operate at the condition of higher temperature with lower feed input speed to get high yield of ethylene.During the catalysts, the best catalyst in catalytic dehydration to produce ethylene was Zr-HZSM-5(40) which was tested at 290℃,ethanol LHSV 2.35 h-1, by which the transformation ratio of ethanol could reach 98.25% while the space-time yield of ethylene was up to 1.36 g/(g·h); In the catalytic conversion of ethanol to aromatic hydrocarbons, it profited the production of arenas at higher temperature with lower feed input speed. The best catalyst in catalytic reaction to produce arene was La-HZSM-5(40) which was tested at 380℃,feed LHSV 0.895 h-1, by which the yield of liquid products could reach 99.40% while the yield of aromatic hydrocarbons was up to 79.41% equaling to space-time yield 0.234 g/(g·h).(2) The catalysts were characterized by FT-IR and XRD. Known from the results, the framework of HZSM-5 zeolite remained well after modifying with active metal ions and/or amorphous Si-Al gel but the surface formed some new micro units that might come of the interaction between metal ions and/or amorphous Si-Al gel with hydroxyl groups on the flaws during zeolte. Thus, the new micro units might change the distribution of acid sites bringing on the enhancement of the catalytic performance.(3) Through the thermodynamics calculations and kinetics analyses, the mechanisms about productions of ethylene and arenas from ethanol were discussed, and the correlative possible reaction paths had been proposed.Through the research, effective catalysts used in catalytic converting bio-ethanol to ethylene and aromatic hydrocarbons and corresponding optimized technology have been found, which have the characteristics of wide input feed concentration, mild reaction condition and high yield of ethylene and arenes. These researchs provide helpful scientific bases for the design and exploitation of catalysts during the realization of bio-ethanol's green conversion to ethylene and aromatics in industry.