Study On Ni Catalytic Hydrogenation Of Carbon Dioxide For Methane

Although the increase of carbon dioxide in the atmosphere bring a series of environmental problems, for example, Sea level rise, glaciers melt and so on, it is the most abundant carbon resources in the world. Therefore, technologies including utilization of carbon dioxide will be a key response strategy for protecting the environment. Undoubtedly, chemical recycling of CO2 is much attractive, such as methanation of carbon dioxide was a meaningful hot task now, This thesis mainly studied the reaction of CO2 hydrogenation to methane on Ni Catalyst which were immobilized on the functional support in miniature fixed bed.To add the second modification of the Ni/γ-Al2O3 was studied, the results show that adding the second component of Ce on the catalytic role of carbon dioxide hydrogenation reaction of methane more, the modified catalyst than a single-component nickel-based catalysts have a stronger catalytic activity. On this basis, the modified catalyst of the system, including the carrier, preparation methods, thermostability and reaction conditions on the catalytic activity. The surface functional groups microstructures of the supporters, the γ-Al2O3 and catalyst were characterized by TG, FI-TR, BET, XRD、H2-TPR. The results as follows:1、The results of thermodynamic calculations for CO2 hydrogenation to methane showed that:the CO2 equilibrium conversion increases along with the increasing of pressure and the mole ratio of H2 and CO2. But raise temperature to the disadvantage of reaction.2、On the same conditions, the results indicate that some Ni catalysts supported on inorganic oxide show high activities. The different catalysts over various supports follow the active order:Ni/TiO2> Ni/γ-Al2O3> Ni/MgO> Ni/SiO2.3、The γ-Al2O3 was prepared by NaAlO2 with lager specific surface area than the γ-Al2O3 was prepared by Al2(SO4)3,and it was benefited to increase Carrier surface area to washing the precipitate with mixture of ethanol and acetone; the best load ofNi was 10% and this result was further verified by XRD;4、The y-Al2O3 was prepared by NaA102 with lager specific surface area than the、The influences of preparation method (wet impregnation and ultrasonic impregnation) on the activity of catalysts have been investigated. The results showed that, compared with the catalyst prepared by impregnation method, the catalyst prepared by ultrasonic impregnation method performed higher activity, benefit for increase Carrier surface area and Ni autonomous disperse in surface of y-Al2O3. In addition to, the right impregnation time was 25 min.5、The influences of reaction temperature, space velocity, pressure, ratio of H2 and CO2 on activity of Ce-Ni/y-Ak2O3 catalyst have been investigated. The optimal reaction conditions was that:400℃, space velocity was 7,200h-1,0.1MPa and ratio of H2 and CO2 was 4. In addition to, By plotting Arrhenius figure, the activation energy of Ce-Ni/y-Al2O3 and ware calculated respectively, the results show that the activation energy of was more lower.6、The thermal stability of Ce-Ni/y-Al2O3 catalyst was studied. Within 72 hours, methane selective was remained above 93%, and carbon dioxide conversion has a little change within 24 h reaction and slightly down after 24 hours.7、Auxiliary Ce addition can significantly increase the activity of catalyst and the optimum adding amount was 2.5%. The catalysts were characterized by BET,TG and H2-TPR, it was revealed to Ce which is benefit for Ni autonomous disperse in surface ofy-Al2O3, enhance catalyst Ni/y-Al2O3 resistance to carbon deposition effect and mechanical strength, reduce NiO reduction temperature.