MgO-Based Granular Sorbent Pelletized by Using Ordered Mesoporous Silica as Binder for Low-Temperature CO₂ Capture

Cyclic CO2 adsorption by using MgO as a sorbent at low temperatures is considered a promising route for postcombustion CO2 capture. However, most MgO-based sorbents are in the form of fine powder and cannot be used in a fluidized bed reactor, and at the same time, suffer from a rapid loss in CO2 uptake capacity due to the decrease of surface area aroused by pore shrinking and grain sintering. In this study, mesoporous silicas with highly ordered pore structures have been used as binders, for the first time, to fabricate MgO-based sorbent pellets via a simple and scalable extrusion–spheronization approach. The obtained MgO-based pellets exhibit high porosity attributed to the nature of the mesoporous binder, leading to a significantly increased stability and CO2 uptake capacity. Especially for the low-concentration CO2 that is comparable to the flue gas from a coal-fired power plant, the results show that the ordered mesoporous silica binder provides a remarkable promotion effect and excellent stability in the capture performance. The CO2 uptake capacity of the best-performing sorbent, 20-KIT-6–100, displays a small decline of 6.86% (from 1.02 mmol of CO2/g in the first cycle to 0.95 mmol of CO2/g in the 10th cycle). It is envisaged that mesoporous materials hold great potential to be used as binders in reinforcing the metal oxide-based sorbents for flue-gas CO2 capture in practical applications