Study On CO₂ Adsorption Performance Of Mixed Amine Functionalized Solid Adsorbent

With the continuous development of society,a series of problems needed to be concerned.These problems were even worrying,such as climate change,global warming and environmental pollution.One of the main factors causing these negative changes on earth was the increase of carbon dioxide（CO₂）concentration in the atmosphere.Fossil fuel combustion was the main source of the rapid increase of CO₂emissions in thermal power plants.So the realization of CO₂emission reduction in the flue gas of coal-fired power plants had become the key to solve the problem.There were other impurities such as sulfur dioxide（SO₂）in the flue gas of thermal power plants.The existence of SO₂had a competitive and adverse effect on the CO₂adsorption of adsorbent.Therefore,it was necessary to improve the selectivity of adsorbent for CO₂.At present,the CO₂absorption process using organic amine solution as the scrubber was the most advanced and had been widely used in industry.However,this process had some unavoidable disadvantages,such as equipment corrosion,high energy consumption of regeneration,large solvent loss.In order to overcome these limitations,solid amine adsorbents had been widely used for CO₂capture due to their advantages of large adsorption capacity,good stability,high renewable performance and fast adsorption rate.The key to the innovation and high efficiency of solid amine adsorbent lied in the selection of amine,carrier and preparation method.Preparation of adsorbents with low cost and good performance had become a major challenge in the field of carbon capture.In this paper,solid amine adsorbents with excellent properties were prepared and a series of studies were carried out.The main conclusions were as follows:（1）A mixed amine functional adsorbent for CO₂capture was developed by impregnating PEHA and AEEA onto MCM-41.The adsorbent was characterized by FT-IR,TGA,SEM,TEM and solid-state NMR.when PEHA and AEEA were loaded with 30%,the maximum CO₂adsorption capacity of P30%-A30%/MCM-41 adsorbent was 4.16 mmol/g at 50℃.In 10 cyclic adsorption/desorption tests,the adsorption capacity of P30%-A30%/MCM-41 decreased from 4.16 mmol/g to 3.86 mmol/g,only about 7.21%,which verified that P30%-A30%/MCM-41 had excellent cyclic regeneration performance.（2）The adsorption and desorption kinetics of P30%-A30%/MCM-41 for CO₂were studied by Avrami kinetic model.P30%-A30%/MCM-41 had a lower CO₂desorption activation energy（8.96 k J/mol）for the adsorbent,indicating that the addition of AEEA not only greatly improved the CO₂capture capacity of the single functional adsorbent,but also improved the desorption efficiency,reduced the regeneration energy consumption,and thus reduced the cost of CO₂capture.The reaction mechanism of mixed amine functionalized adsorbent was investigated by FT-IR and solid-state NMR.FT-IR and ¹³C solid-state NMR proved that the main product of the reaction of mixed amine functionalized adsorbent with CO₂was carbamate;The two-dimensional ¹H-¹³C heteronuclear correlation spectra showed that the carbonyl oxygen in the carbamate ion and the hydroxyl hydrogen in AEEA form hydrogen bonds.The addition of AEEA made the formation of hydrogen bonds between the products,and the hydrogen bonds stabilized the carbamate ions of the products,thus promoting the adsorption capacity of the adsorbent and improving the adsorption efficiency.（3）The ionic liquid[PEHA][NO₃]was prepared by modifying PEHA with nitric acid,glycol diglycidyl ether（EGDE）was used to conduct simple chemical crosslinking of sodium alginate and PEHA and added calcium chloride solution to further crosslink it into hydrogels.A new cheap ionic liquid functionalized alginate adsorbent was prepared.The adsorption performance and CO₂selectivity of the adsorbent were studied.And the ionic liquid functionalized sodium alginate adsorbent was characterized by FT-IR and thermogravimetry.When the molar ratio of PEHA to nitric acid was 1.5,nitrate had the best inhibition effect on SO₂reaction.When the water vapor content was 10%,the CO₂adsorption capacity and selectivity of SA-[PEHA][NO₃]-1.5 were the highest,which were 1.97 mmol/g and 1.08,respectively.The results of CO₂and SO₂kinetics of SA-[PEHA][NO₃]-1.5 showed that the fitting curve of Avrami model was in good agreement with the experimental data at 40℃,50℃,60℃and 70℃,with R²greater than 0.99.The results showed that physical and chemical adsorption occurred simultaneously in the adsorption process of CO₂and SO₂on SA-[PEHA][NO₃]-1.5 adsorbent.