Easily-synthesized and low-cost amine-functionalized silica sol-coated structured adsorbents for CO2 capture

Abstract

One reason for the slow development of adsorption-based carbon capture technologies is the inefficient fabrication of adsorbents with both promising adsorption performance and granular strength. In this work, an easy, low-cost, and environmentally friendly one-pot method is proposed to prepare structured adsorbents for post-combustion CO2 capture. Different from the traditional method that uses powdered silica gel as the support, branched polyethyleneimine (PEI) was mixed with colloidal silica and was then coated onto a ceramic fiber honeycomb monolith. Scanning electron microscopy (SEM) provided evidence that the amine molecules dispersed uniformly onto the porous silica films after vacuum drying. The optimal adsorption temperature, humidity, and PEI loading of the adsorbents were then determined using isotherms, adsorption rate curves, and breakthrough curves. The results showed that the 50 wt% PEI-impregnated silica sol had the highest capacity (1.719 mmol/g), which was comparable to that prepared with silica gel powders. On this basis, the manufacturing process of the structured adsorbents was optimized by referring to the capacity, kinetics, and mechanical strength. In addition, the use of the 80 wt% PEI soaking solution to soak the ceramic fiber honeycomb twice was recommended. The structured adsorbents exhibited capacities up to 1.025 mmol/g in simulated flue gas and had very stable performance in humid conditions, showing little degradation after 50 adsorption/desorption cycles