Preparation Of Mesoporous Silica And Mesoporous Carbon Materials And Their Application For CO₂ Adsorption

Because of the large-scale use of fossil fuels, such as coal, petroleum, and natural gas, the atmospheric CO2 concentration is gradually increasing. It is a worldwide issue of the CO2 concentration rise, so developing a kind of technologies of capturing CO2 is very important.This paper using P123 as a template and 1,2-bis (trimethoxysilyl) ethane (BTME) as a silica source to synthesize mesoporous ethane-silica nanotubes (E-SNTs). E-SNTs were modified with polyethylenimine (PEI) as sorbents for CO2 adsorption. The F127 as the template, TEOS as a silica source to synthesize order mesoporous silica (OMS) with different pore size (5.6 nm and 7.6 nm); KTT-6-CN was synthesized by nano-replication using carbon tetrachloride and ethylenediamine as precursors, and KIT-6 with cubic Ia3d symmetry as a hard template. The three new materials were using to capture CO2. These new composite sorbents were characterized by transmission electron microscopy, nitrogen adsorption/desorption and thermal gravimetric analysis.1. Preparation of silica nanotubes and their application for CO2 adsorptionA series of E-SNTs with loading different amount of amine were preparation, they were used in capture of CO2. The results show that, E-SNTs with a 50% (w) PEI loading (E-SNTs-50) exhibited a higher CO2 adsorption capacity (3.32 mmol/g) than the other materials. The unoccupied space is beneficial for higher CO2 uptake because the mass transfer limitation can be exhibited the some extent and the interaction between CO2 and PEI may be easier. Additionally, CO2 uptake was further enhanced to 3.75 mmol/g in the presence of moisture. Cyclic CO2 adsorption-desorption test results indicated that the composite sorbents are stable and can be regenerated.2. The preparation of amine-modified ordered masoporous silica and CO2 capture performanceThe new sorbents were prepared by OMS and amine, then used to capture CO2. The results show that the adsorption of CO2 of OMS-7.6 were better than the OMS-5.6, because the materials of OMS-7.6 have large pore size. According to the result of the MS, the sorbents which have larger pore size, then the diffusion resistance becomes smaller, and lead to the better adsorption ability when they modified the same amount if amine.3. Synthesis of nitrogen-doped carbon with three-dimensional mesostructures for CO2 captureKIT-6-CN was preparation by the KIT-6 with cubic laid symmetry as a hard template. CO2 adsorption-desorption isotherms indicate that this nitrogen-doped material has relatively high CO2 capture capacities of 2.11 mmol/g at 25℃ and 3.09 mmol/g at 0℃, which are superior to those of the pure carbon material (KIT-6-C), with ananlogous mesostructures. Cyclic CO2 sorption-desorption tests demonstrated the stability of the sorbent. Thus, the new sorbent can potentially be a good candidate for CO2 capture. Proven by XPS analyses, it has been known that the nitrogen-doped atoms can change the chemical state of carbon materials, and it’s good for the CO2 capture.