Research On Novel CO₂ Sorbents Based On Self-Assembly Template Synthesis Method

Global warming and climate change caused by CO2 emission is to be a hot topic all over the world. CaO-based sorbents are widely used for CO2 capture in post-combustion process, however, the development of CaO-based sorbents is limited in following aspects: (1) the CaO-based sorbents suffer from rapid deactivation during successive cycles, which is also called loss-in-capacity, (2) the calcination of CaCO3 needs a lot of heat.This paper proposes a novel self-assembly template synthesis (SATS) method to prepare core-shell structured CaO/TiO2-Al2O3 and CaO-CuO/MgO-Al2O3 sorbents. Al2O3 as core structure undertake the main mechanical strength and enhance the sintering resistance, TiO2 or MgO as shell structure prevent the chemical reaction between core structure and active materials.As for the loss-in-capacity problem, three CaO-based sorbents are tested in thermogravimetric analyzer (TGA) environment and batch fluidized bed environment for compare their reactivity and stability, it is found CaO/TiO2-Al2O3 shows the best CO2 capture performance. In addition, the results of SEM-EDX, TEM and XRD tests confirm that CaO/TiO2-Al2O3 indeed has the core-shell structure.As for the heat requirement problem, this paper proposes a combined CaCu-based chemical looping cycle, the exothermic reduction of CuO can provide heat for the endothermic calcination of CaCO3 during combined cycle, thus realizing an internal heat balance to improve energy efficiency. Four CaCu-based samples made by different method are tested in TGA environment and batch fluidized bed environment for compare their reactivity and stability during combined cycles, the SATS-derived CaO-CuO/MgO-Al2O3 shows a high reactivity and stability when compared with other sorbents, in details, CaO-CuO/MgO-Al2O3 performs superior CO2 capture capacity and durable stability in TGA and fluidiezed bed. The results of heat analyse during reduction/calcination process shows the reduction reaction is faster than calcination reaction, and the heat provided by reduction reaction can meet the demand of calcination reaction.In addition, SEM-EDX, BET-BJH, XRD, TEM and other tests are used to analyze the fresh and used CaO-based sorbents and CaCu-based sorbents. According to the microscopic test results and macroscopic cyclic results, the SATS-derived sorbents performs high reactivity, thermal stability, mechanical strength, and resistance to agglomeration and sintering during cycles, which shows much better comprehensive performance than other sorbents.