Effect of pore size, aminosilane density and aminosilane molecular length on CO2 adsorption performance in aminosilane modified mesoporous silica

Abstract

Mesoporous silicas with different pore size were modified by aminosilanes with different molecular length. CO2 adsorption capacity was improved by all aminosilane modification, and the CO2 adsorption capacity was further improved with increasing the aminosilane density. However, CO2 adsorption capacity and the amine efficiency of (3-trimethoxysilylpropyl)diethylentriamine (TA) modified mesoporous silicas with small pores such as MCM-41(2.9 or 3.1 nm) and SBA-15(6.2 or 7.1 nm) were significantly decreased at high aminosilane density. In contrast, TA modified SBA-15 with a large pore (10.6 nm) exhibited further improvement of CO2 adsorption capacity and amine efficiency. N2 adsorption desorption measurements suggested that the pore plugging occurred at high aminosilane density in TA modified mesoporous silicas with small pores. In situ FT-IR spectra and the half-value period of CO2 equilibrium adsorption capacity clearly shows the CO2 adsorption kinetics in these adsorbents with small pores were significantly lower than that in the adsorbent with large pores. To develop the CO2 adsorbents with high adsorption performance, the correlation between aminosilane molecular length, pore size of mesoporous silica and aminosilane density should be considered.