PEI-impregnated microporous carbon materials obtained from cellulosic low-cost precursors for CO2 adsorption and conversion

MATIAS LANUS MENDEZ ELIZALDE; FABIANA C GENNARI; AURELIEN GASNIER

Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

AAIQ Asociacion Argentina de Ingenieros Quimicos

CO2 capture and storage technology is a blooming field for mitigating the environmental impact of fossil fuel combustion. While polyethylenimine(PEI)-impregnated silica matrixes display impressive results[1], the matrixes´ cost and the system´s lack of reversibility hinder their application. Thus, low-cost carbon-based capture materials are of great interest[2]. The storage of industrial amounts of CO2 entails high operational costs, but CO2 conversion to higher-value derivatives (CH4) might solve this issue.This work presents the synthesis of microporous matrixes from cellulosic waste surpluses (agro-industrial and urban) such as cigarette filters, peanut shells, almond shells, and poplar seed tufts. Typically, the rough materials were grounded and subjected to hydrothermal treatment at 220 °C; the obtained hydrochars were then activated with KOH at 800 °C in a horizontal furnace under nitrogen.The systematic characterization of the matrixes aimed at deciphering the structure-property relationship of our materials. Morphology and structure were studied by electron microscopy and X-ray diffraction. The composition was analyzed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Nitrogen adsorption isotherms afforded the evolution of textural parameters with filling values. The free matrixes exhibited high surface area (1180–2020 m2/g) and large micropores volume (0.56–0.89 cm3/g) with negligible meso/macroporous content. The microporous matrixes were loaded with PEI according to the pore volume to prevent clogging in the presence or absence of metals. Then, the materials´ CO2 capture capacity was evaluated with a thermogravimetric balance and related to the surface area of each material. For a 25 %wt PEI loading on activated cigarette filters, the CO2 capture capacity reached 2 mmol/g, of which 30 % was related to physisorption and 70 % to chemisorption. Moreover, the optimal CO2 capture temperature was determined to be 85 °C. At that temperature, the capture reactions reach a compromise between diffusion through PEI (kinetic) and CO2 capture/release equilibrium (thermodynamic). These results make the impregnated matrixes auspicious for tandem CO2 reduction.In conclusion, the microporous matrices were easy to synthesize using low-cost precursors. The rational analysis of their textural/chemical properties allowed us to optimize PEI filling to improve the CO2 capture capacity. Therefore, the obtained amine-functionalized carbon materials are promising candidates to be implemented in CO2 adsorbents and further conversion.