Enhancement of the CO_(2)adsorption and hydrogenation to CH_(4)capacity of Ru–Na–Ca/γ–Al_(2)O_(3)dual function material by controlling the Ru calcination atmosphere

Integrated CO_(2)capture and utilization(ICCU)technology requires dual functional materials(DFMs)to carry out the process in a single reaction system.The influence of the calcination atmosphere on efficiency of 4%Ru-8%Na_(2)CO_(3)-8%CaO/γ-Al_(2)O_(3)DFM is studied.The adsorbent precursors are first co-impregnated onto alumina and calcined in air.Then,Ru precursor is impregnated and four aliquotes are subjected to different calcination protocols:static air in muffle or under different mixtures(10%H_(2)/N_(2),50%H_(2)/N_(2)and N_(2))streams.Samples are characterized by XRD,N_(2)adsorption-desorption,H_(2)chemisorption,TEM,XPS,H_(2)-TPD,H_(2)-TPR,CO_(2)-TPD and TPSR.The catalytic behavior is evaluated,in cycles of CO_(2)adsorption and hydrogenation to CH_(4),and temporal evolution of reactants and products concentrations is analyzed.The calcination atmosphere influences the physicochemical properties and,ultimately,activity of DFMs.Characterization data and catalytic performance discover the acccomodation of Ru nanoparticles disposition and basic sites is mostly influencing the catalytic activity.DFM calcined under N_(2)flow(RuNaCa-N_(2))shows the highest CH_(4)production(449μmol/g at 370℃),because a well-controlled decomposition of precursors which favors the better accomodation of adsorbent and Ru phases,maximizing the specific surface area,the Ru-basic sites interface and the participation of different basic sites in the CO_(2)methanation reaction.Thus,the calcination in a N_(2)flow is revealed as the optimal calcination protocol to achieve highly efficient DFM for integrated CO_(2)adsorption and hydrogenation applications.

Combining CO_(2) capture and catalytic conversion to methane

Considering the global objective to mitigate climate change,import efforts are made on decreasing the net emission of CO_(2) from gas effluents.On the one hand CO_(2) capture-for example by adsorption onto solid basic materials-allows to withdraw CO_(2) from the waste gas streams emitted by incinerators,cement manufacture plants,combustion plants,power plants,etc.On the second hand,CO_(2) can be converted to useful chemicals-e.g.hydrogenation to methane-using appropriate heterogene-ous catalysts.A relatively innovative strategy consists in combining both technologies by designing materials and processes which can switch between capture and methanation modes cyclically.This allows treating complex waste gas effluents by selectively and reversibly capturing CO_(2),and to perform the catalytic hydrogenation in appropriate reaction conditions.This short review presents the main strategies recently reported in the literature for such combined CO_(2) capture and methanation(CCCM)processes.We discuss the different types of reactor configurations and we present the formulations used in this context as adsorbent,as methanation catalysts,and as“dual functional materials”.