Creviced titanate nanotube modified with stearyl trimethyl ammonium bromide as a support for amine-based CO2 sorbent

Abstract

In this paper, a series of protonated titanate nanotubes (PTNTs) modified by stearyl trimethyl ammonium bromide (STAB) were prepared as supports for Polyethyleneimine (PEI)-based sorbents. The CO2 adsorption performance was evaluated in a self-assembled fixed bed reactor. The typical sorbents were characterized by XRD, EDS, SEM, HR-TEM, N2 adsorption-desorption, FT-IR and TGA. Results indicate that the modification significantly improves CO2 adsorption capacity of the sorbents. The maximum CO2 adsorption amount of 2.22 mmol/g was obtained over the modified PEI-based sorbent in 2% CO2/air. Based on the characteristic analysis, the formation of creviced nanotubes, instead of intact nanotubes, is testified because of the modification. Such unique nanotubes possess the higher BET surface area and larger pore volume, which enables more PEI to uniformly distribute on the surface of modified PTNT supports. Especially, it is easier for PEI to enter the inner pores through the crevice than from tube orifices, avoiding pore blockage and facilitating CO2 diffusion in pores. The abundant amine-sites and small internal diffusion resistance endow the modified sorbent with large CO2 adsorption capacity. In addition, the PEI/PTNT adsorbent displays good thermal stability and reusability.