电站锅炉的尾气在脱硫后含有微量的SO2,导致CO2吸附剂性能变差.根据电厂烟气的组分,采用模拟烟气在实验室条件下对K2CO3吸附剂的CO2吸附性能及SO2对CO2吸附的影响进行实验研究.结合XRD分析,利用密度泛函理论(density functional theory,DFT)对SO2 在K2CO3吸附剂上的影响及CO2吸附机理进行理论研究.结果表明,受SO2分子S原子活跃的s轨道影响,S的p轨道及O原子活性均增强,与 K2CO3 表面 O 原子价带顶能带简并,SO2 被优先吸附在K2CO3 表面的O顶位,并将CO2推离吸附剂表面,导致吸附剂活性位点虽有空余却无法吸附CO2.在实验中表现为:模拟烟气中 CO2 体积浓度为 10%时,气氛中体积浓度为0.007%的SO2会使吸附剂的吸附量由1.65 mmol/g降低至 1.01 mmol/g.提出CO2与H2O在K2CO3(001)表面的吸附机理,理论计算的反应活化能为 40.7 kJ/mol,反应热为-54.9 kJ/mol.
Experimental and DFT Mechanism Study on the Effect of SO2 on CO2 Adsorption Performance by K2CO3
The exhaust gas of power plant boiler contains trace SO2 after desulphurization,resulting in poor performance of CO2 adsorbent.In this paper,according to the composition of flue gas in power plant,CO2 adsorption performance of K2CO3 adsorbent and the effect of SO2 on CO2 adsorption are studied by using simulated flue gas under laboratory conditions.Combined with XRD analysis,density functional theory(DFT)is used to study the effect of SO2 on K2CO3 adsorbent and the mechanism of CO2 adsorption.The results show that under the influence of the active s orbital of S atom in SO2 molecule,the p orbital of S and O atom are both more active,which degenerated to the valence band maximum of O atom on the surface of K2CO3.SO2 is preferentially adsorbed on O top site of K2CO3 surface and pushes CO2 away from the adsorbent surface,resulting in the adsorbent's active site being free but unable to adsorb CO2.It shows up in the experiment as follows:when the volume concentration of CO2 in the simulated flue gas is 10%,SO2 with a volume concentration of 0.007%in the atmosphere will reduce the adsorption capacity of the adsorbent from 1.65mmol/g to 1.01mmol/g.The adsorption mechanism of CO2 and H2O on the surface of K2CO3(001)is proposed.The theoretically calculated reaction activation energy and reaction heat are 40.7kJ/mol and-54.9kJ/mol,respectively.
K2CO3 adsorbentCO2 captureSO2 influencedensity functional theory(DFT)mechanism research
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