Modificação de peneiras moleculares do tipo MCM-41 por deposição de carbono e lavagem ácida aplicadas na adsorção de CO2

Abstract

The present work aimed to evaluate the modification of mesoporous materials of the MCM-41 type through carbon deposition and acid washing for use as an adsorbent in the capture of CO2. In order to obtain structures with different textural properties (pore diameter, specific area, pore volume, among others), two synthesis routes were used: the first of pure silica (Si-MCM-41) and the second containing aluminum (Al-MCM-41), obtained through hydrothermal synthesis in autoclaves under autogenous pressure at 150 °C for 24 h. The post-synthesis treatment took place in two stages: carbon deposition using commercial glucose and then acid washing with a 0.2 M hydrofluoric acid solution at 65 °C for 2 h. The samples were characterized by X-ray diffractometry, energy dispersion X-ray spectroscopy, nitrogen adsorption-desorption, Fourier transform infrared spectroscopy, CO2 desorption at programmed temperature, thermal analysis and scanning electron microscopy. The CO2 adsorption tests were performed on a thermogravimetric scale at 40 ° C under atmospheric pressure. The results obtained showed that the carbon deposition led to a significant reduction in the values of surface area and pore volume for the MCM-41 samples, due to deposits of carbonaceous species blocking part of the mesoporous. After the acid wash, part of these deposits were removed, as well as the occurrence of structural leaching of silicon atoms. Thus, the post-synthesis treatment allowed the generation of structures with a pore bimodal system (micro-mesopores), providing a substantial increase in the CO2 adsorption capacity compared to the synthesized mesoporous materials (approximately 66% for Si-MCM-41 and 44% for Al-MCM-41), representing a significant improvement in the performance of these adsorbents in the CO2 capture process.