RESUMO
Solid adsorbents with precise surface structural chemistry and porosity are of immense interest to decode the structure-property relationships and maintain an energy-intensive path while achieving high activity and durability. In this work, we reported a series of amine-modified zeolites and their CO2 capture efficiencies. The amine impregnated molecular zeolite compounds were characterized and systematically investigated for CO2 adsorption capacity through thermogravimetric analysis for the occurrence of atmospheric pure CO2 gas at 75 °C with diethylenetriamine (DETA), ethylenediamine (EDA), monoethanolamine (MEA), and triethanolamine (TEA)-loaded zeolite 13X, 4A, and 5A adsorbents. The kinetics of the adsorption study indicated that the adsorption capacity for CO2 adsorption was improved with amine loading up to a certain concentration over 13X-DETA-40, showing an adsorption capacity of 1.054 mmol of CO2 per gram of zeolite in a very short amount of time. The result was especially promising in terms of the initial adsorption capacity of zeolite, which adsorbed approximately 0.8 mmol/g zeolite within the first two minutes of experimentation. A detailed flow chart that includes a brief look into the process adopted for adsorption was included. Lagergren pseudo-first- and pseudo-second-order models of 40 wt % DETA zeolite 13X gave CO2 adsorption capacities of 1.055 and 1.058 mmol/g and also activation energies of 86 and 76 kJ/mol, respectively. The CO2 adsorption capacity of 13X-DETA-40 in a lab-scale reactor was found to be 1.69 mmol/g. A technoeconomic study was conducted for the solid amine zeolites to understand the investment per ton of CO2 adsorbed. This study was used as a basis to improve cost estimates from a microscale to a lab-scale reactor. The cost of investment for 13X-DETA-40 was reduced by 84% from $49,830/ton CO2 adsorbed in a microscale reactor to $7,690/ton of CO2 adsorbed in a lab-scale reactor.
RESUMO
A class of high molecular weight polyethylenimine (PEI)-modified zeolite 13X adsorbents were synthesized by varying the concentration of imines and screened for preliminary investigation of CO2 capture studies. The impregnated molecular amine zeolite composite was characterized and CO2 adsorption performance was investigated through TGA in the presence of atmospheric pure CO2 gas at 25, 50, 75, and 100 °C, respectively, using 20-80 wt % of PEI-loaded zeolite 13X adsorbents. This paper reports on the effects of temperature and amine (PEI) loading on CO2 adsorption capacity and estimated kinetic parameters through modeling of selected models which represent the reaction rate and diffusion rate models. The studied adsorbents showed the highest adsorption capacity at 75 °C with 60 wt % PEI loading. Thus, the optimum temperature of 75 °C and optimal loading of 60 wt % was observed from the current studies for CO2 capture. From modeling study, it was found that Avrami's fractional order and dual kinetic models (DKM) described well the adsorption behavior of CO2 on PEI-impregnated zeolite 13X at all temperatures accurately and up to 75 °C, respectively. Besides, intraparticle diffusion was found to be the rate-limiting step when compared with the film diffusion model.
