Preparation,Characterization And CO₂Adsorption Performance Of Al₂O₃Supported DBU

In the recent years, greenhouse effect has become a global climate problem. In a variety of greenhouse gas, carbon dioxide (CO2) plays a decisive role. Furthermore, coal-fired power plants ought to bear mostly liability accounting for about30%CO2emissions. Thus, how to capture CO2efficiently and economically has a long-term significance for achieving CO2emissions reduction as well as sustainable development of coal-fired power plants in China. In this article, DBU-GAA adsorbents with different load ratio prepared by supporting1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) on granular Al2O3were applied to adsorp CO2. Characterization of the absorbent were characterized by scanning electron microscope (SEM), nitrogen adsorption and thermogravimetric analyzer. Fixed-bed adsorption experiment was carried out under atmospheric pressure to study the adsorption behavior of CO2by Al2O3supported DBU absorbent. On the basis of investigating the influence of load ratio, flow rate, water vapor ratio, inlet CO2concentration, regeneration temperature, adsorbent cycle number, acid gasesand other factors on CO2adsorption by applying adsorption breakthrough curve and adsorption capacity, the CO2adsorption experimental data and laws could be achieved and explored.Load data of prepared adsorbent revealed that DBU could be effectively loaded on Al2O3. The load ratio was increased with increasing the added DBU; on the contrary, the utilization rate was decreased. This was verified by the SEM results either. Determination of characteristic pore structural indicated that with the rising of DBU load ratio, specific surface area of adsorbent was decreased, and pore size became larger; blocking effect of DBU on the mesopores and macropores of Al2O3Supported DBU was relatively weak and total blocking effect was slightly inferior to that on granular activated carbon (GAC); the load of A12O3Supported DBU didn’t have a strong influence on pore structure. Al3O3supported DBU adsorbent had a better thermal stability at less than140℃. precipitation amount of DBU raised in the range of140℃to200℃.Fixed-bed adsorption experiment demonstrated that under the present experimental conditions, when DBU load ratio raised from0.00%(A-0) to11.75%(A-7), the breakthrough time was prolonged9min, and saturated adsorption capacity presented a significant increasing trend; breakthrough time of A-8were drastically shorter and slighter than A-6and A-7, its saturated adsorption capacity decreased neither. Speed up of flow rate by50mL/min could shorten breakthrough time, but the saturated adsorption capacity was not large if flow rate was relatively small (50mL/min,100mL/min); flow rate150mL/min guaranteed the breakthrough time in addition to saturated adsorption capacity. On condition that water vapor ratio15%, inlet CO2concentration15%, DBU and CO2had a sufficient reaction, the breakthrough time was long and saturated adsorption capacity was great. When regeneration temperature was80℃, comparing with60℃and100℃, regeneration result was satisfying and there’s not much DBU fleeing from supporter on account of high temperature. Besides, A-2and A-10adsorbents could still maintain a desirable adsorption property after10cycles.Adsoption data of simulated flue gas (acid gases included) on Al2O3supported DBU adsorbent implied that breakthrough time and saturated adsorption capacity of CO2on adsorbent A-3diminished at higher acid gases concentration. Consistently, lower acid gases content has little consequence on adsorption property. Under current condition, A12O3supported DBU adsorbent could also react with SO2and NO, and SO2could be adsorpted more in same case. Subsequently, under suitable regeneration temperature, CO2in flue gas could be removed combined with SO2and NO. Under the premise of containing SO2and NO, at flow rate150mL/min, both breakthrough time and saturated adsorption capacity were better comparing with100mL/min and200mL/min; at regeneration temperature80℃, the long breakthrough time and the enormous saturated adsorption capacity of regenerated adsorbents were acquired. Determining of pore structure characterization of regenerated adsorbents disclosed that adsorbing simulated flue gas containing0.5%NO or0.5%SO2and regenerated at80℃would not have a great impact on pore structure characterization. The results of thermogravimetric analysis validated the conclusion that Al2O3supported DBU adsorbent could react with SO2and NO.