The Synthesis And Properties Of The Fe-based Catalyst For The Hydrogenation Of Carbon Dioxide To Hydrocarbons

With the development of human society, abundant fossil fuels are being used so that the content of CO2in the air is more and more. This not only aggravates the greenhouse effects, but also it is a great waste for carbon sources. If we can transform CO2into high value-added products, it must have a great significance for improving the living environment and solving the energy crisis. Now, replacing CO as carbon sources, the study on hydrogenation of CO2to hydrocarbons is becoming hot. Here, some Fe-based catalysts were synthesized and the paper sheds some lights on the reaction of conversion of CO2to hydrocarbons.The Fe-based catalysts were first synthesized by impregnation method and lnyrogenation of carbon dioxide over the catalysts were tested in the fixed bed. The results indicated that the conversion of the CO2over15wt.%Fe10wt.%K-HY or-γ-Al2O3catalysts could reach50.0%, with the selectivity of C2+about57.0%under the pressure of3MPa, the reaction temperature of673K, the space velocity of3600h-’and the molar ratio of H2/CO2of3.6. With HY being exchanged with K, the molar ratio of light olefin/paraffin in the products increased from1.5to2.4. Also the conversion of CO2was promoted by12%when the HY support was modified by removing some aluminum and silica. The effects of dopants are obvious:0.5wt.%Ag or Cd improved the reducibility of the catalyst and had a positive effect on the distribution of products; La,Mn,Ru or Cr had a strong hydrogenation ability so that inhibited the activity of catalyst.Combining with the urea co-precipitation-gelation,the mechanical mixing and impregnation method, another Fe-based catalyst can be attained. Under the some conditions, the effects of Fe, K and other additives were investigated. Moderate amounts of K can modulate the competitive adsorptive capacities of C and H species; Suitable contents of Fe supply more active sites and improve the conversion of CO2. The results indicated that over the15wt.%Fe10wt.%K/γ-Al2O3catalyst, the conversion of CO2could reach to51.3, with the selectivity of C2+hydrocarbons of62.6and light olefin/paraffin of3.6.1.1wt.%Cu improved the dispersity and reducibility of the catalyst. The additive of Si inhibited the activity while the selectivity of C2+is increased with Cd added and Mn exacerbated the methanation.The supports and preparation conditions are also important for catalysts. γ-Al2O3is the most favorable support for its high CO2conversion and hydrocarbons selectivity. Y-zeolite aggravates the methanation and CeO2leads to more CO and paraffin products. The selectivity of light olefins increased with more aging times and the lower precipitation temperature is helpful to get smaller particle catalysts and higher molar ratio of olefin/paraffin products.The reaction temperature and the molar ration of H2/CO2in feed gas also have some important effects. The conversion of CO2is higher with the reaction temperature and the molar ratio of H2/CO2increasing:The catalyst shows the highest hydrocarbons selectivity of75.7%at300℃and the favorable molar ratio of H2/CO2is about3-4.