Study On Sodium-based CO₂ Sorbent Based On Mesoporous Al₂O₃ Carrier And Its Decarbonization Performance Impact

With the large amount of CO₂ emissions,the resulting hazards are becoming more and more serious.In order to achieve CO₂ emission reduction targets,the development of feasible CO₂capture technologies for major single-point emission sources of coal-fired power plants has become an important issue in the international community.Among the many CO₂ capture technologies,the alkali metal-based solid sorbent cryogenic sorption technology has attracted much attention due to its low regeneration energy consumption and good adcompatibility.And using sodium-based sorbent for CO₂ capture will have high industrial application potential because of its high theoretical sorption capacity,cheap price and low regeneration energy consumption,However,there is still a gap in kinetic performance of sodium-based sorbent compared with potassium-based sorbents.Studies have shown that the use of mesoporous materials with high specific surface area and high pore volume as a carrier can effectively improve the CO₂ sorption performance of the sorbent.But there are few studies on the influence of carrier surface parameters on the sorbent’s CO₂ sorption capacity,especially the lack of research on the influence of carrier pore size distribution on the CO₂ sorption capacity,which makes the choice of carrier morphology lack theoretical guidance during the development of sodium-based sorbents.In this paper,a series of mesoporousγ-Al₂O₃ was synthesized and used as a carrier to prepare sodium-based sorbents.The influence of the surface parameters of the carrier on the sorption performance of CO₂ was studied,and the influence of preparation methods on the sorbent was further explored.The specific content is as follows:Using different templates,mesoporous Al₂O₃ with high specific surface area and concentrated pore size distribution was prepared by the sol-gel method,and the influence of synthetic raw materials and preparation conditions on the morphology and structure of mesoporous Al₂O₃was deeply studied.Studies have shown that the type,amount,stirring temperature,calcination temperature,stirring time and other factors of the template have varying degrees of influence on the surface parameters such as the specific surface area of the mesoporous Al₂O₃.Among them,the type of template and the calcination temperature have a greater impact.Glucose and sucrose are both sugar small molecule templating agents,and the pore size distribution of the synthesized mesoporous Al₂O₃.Samples are relatively similar,concentrated around 5 nm,with sucrose as the templating agent synthesized mesoporous Al₂O₃.having a larger specific surface area.The pore size of mesoporous Al₂O₃.synthesized with non-ionic surfactants as templating agents is larger,with the pore size around 8-12 nm.A loaded sodium-based sorbent was prepared using the synthesized mesoporousγ-Al₂O₃.as a carrier.The effect of impregnation process on the surface parameters and pore structure was investigated,and the influence of specific surface area and pore size on the CO₂ sorption performance of the sorbent was explored.The specific surface area and pore size of the carrier have effect on the sorption performance of the sorbent,and the sorption performance increases with the increase of the specific surface area or pore size of the carrier.In the range of pore sizes examined,the effect of pore size on sorption performance was greater than that of specific surface area.At the pore size distribution of about 5 nm,the specific surface area of the carrier decreased significantly after loading and the original pore size was blocked by Na₂CO₃,and only the active components on the surface were involved in the reaction,and the carrier did not substantially promote the hydrocarbonation reaction of the sorbent.When the pore size distribution was around 12 nm,the specific surface area of the carrier also decreased after loading,with a relatively small decrease,and retained some original pore structure,and the sorption performance was improved,indicating that the carrier had a certain promotion effect on the deepening of the hydrocarbonation reaction of the sorbent and the increase of the reaction rate at this time.A series of sodium-based sorbents were prepared by changing the impregnation method,loading amount and ion doping.The effect of the preparation method on the surface and the physical phase was investigated.The effect on the CO₂ sorption performance was further studied.A suitable preparation method for the sodium-based sorbents was selected.Equivalent impregnation has effect on the pore size distribution and pore shape of the sorbent due to the different impregnation processes,and the sorption rate of the prepared sorbent decreases.Therefore,over-impregnation is more suitable for the preparation of sorbents with the previously screened carriers.The CO₂ sorption capacity and sorption rate of the sorbent obtained by increasing the loading amount were significantly increased,but the increased loading amount caused the pore size blockage of the sorbent to intensify,so that the active components inside the sorbent could not participate in the reaction,and the degree of hydrocarbonation reaction was significantly decreased.Mg²⁺doping contributes to the deepening of the reaction degree of the sorbent,but decreases the rate of hydrocarbonation in the pre-reaction period.In addition,the doping procedure for Mg²⁺is more tedious and difficult to achieve batch preparation.K⁺doping will not change the pore structure of the sorbent,and has an enhancing effect on the ion diffusion of the active component.The degree of K⁺-doped sorbent was deepened,and the rate of hydrocarbonation in the pre-reaction period was significantly enhanced.At the same time,the preparation process with K⁺doping is relatively simple.