Investigation Of CO₂ Hydrogenation To Hydrocarbons With Al₂O₃ As Supports

With the significant development of industrialization, the emissions of CO2 have increased rapidly and leaded to a series of ecological and environmental problems. At the same time, the shortage of non-regenerated energy resources is more and more serious and it is time to explore new routes to produce renewable energy resources. The hydrogenation of CO2 to high value-added chemicals can not only make use of CO2, but also relieve the pressure coming from the shortage of energy.Here, we selected and prepared Al2O3 with different properties for iron based catalysts and the catalysts were used for catalytic CO2 hydrogenation in a fixed-bed reactor. The followings gave the results of the effects of Al2O3 properties.1. The effects of supports'acid-base properties to catalytic performance. Two kinds of Al2O3 with different acid-base properties were used as supports for catalytic CO2 hydrogenation. The acid-base properties influenced the interaction between loaded metal and supports and the catalyst supported with Al2O3-Acidic showed poor reduction ability. The catalyst supported with Al2O3-Alkaline performed more weaker H2 adsorption capacity than others, which promoted its selectivity of C5+ and C2-C4=, reaching 19.8% and 22.9% respectively.2. Effects of supports'morphology to catalytic performance. Alumina materials with different morphology have been synthesized via hydrothermal synthesis method using AlC13·6H2O as a precursor. The different ratio of n(OH-):n(Al3+) leaded to different morphology of Al2O3 showing different leading crystal face groups. The ability of catalysts supported on Al2O3 with different morphology to adsorb CO2 and CO differed from each other. It showed that the morphology of Al2O3 had no significant effects on CO2 conversion, while it was not the same case for products selectivity. The catalysts supported with flake-like Al2O3-3.0 showed the best selectivity of C5+ and C2-C4=, reaching 18.5% and 18.9 respectively, and in addition, the selectivity of C2+ reached 51.5%.3. Effects of supports'calcined temperature to catalytic performance. A kind of commercial pseudo-boehmite were calcined at different temperature to prepare Al2O3-T. It was showed that ?-Al2O3 appeared when the calcined temperature rose to 700?. The reduction property was affected by the calcined temperature and the catalysts showed low reduction ability supported on Al2O3 calcined at 900?. The CO2 conversion reached 42.4% with the catalyst supported on Al2O3 calcined at 500?. When the calcined temperature was 400?, the catalysts showed better products selectivity, the selectivity of CO coming to the lowest at about 29.0% and the selectivity of C5+ and C2+ reaching the highest at about 28.5% and 61.4% respectively.4. Effects of SiO2 additive into alumina to catalytic performance. Alumina materials with different SiO2 content have been synthesized via the evaporation induced self-assembly (EISA) approach using TEOS as a precursor. The SiO2 additive influenced the interaction between support and loaded metal, and reduced the reduction ability of catalysts. In addition, the SiO2 reduced the adsorption ability of catalysts for CO2 and CO. The SiO2 addtive into Al2O3 couldn't improve the catalytic performance for catalysts on CO2 hydrogenation.