Study and kinetic analysis of calcined carbide slag doped with silicon nitride for cyclic CO2 capture

Using solid waste carbide slag (CS) as a calcium precursor and silicon nitride (Si 3 N 4 ) as a new inert dopant , a series of calcium oxide (CaO)-based adsorbents were prepared by a simple dry mixing method and high temperature CO 2 cyclic adsorption property was tested in a thermogravimetric analyzer (TGA). A lot of matters were studied in this work like the effects of Si 3 N 4 type, dopant content, pre-calcination conditions, CO 2 concentration and long-term cycles on CO 2 adsorption property. The phase composition, surface morphology and surface area of the adsorbents were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Nitrogen Physisorption analyses. The cyclic conversion experiments of three kinds of Si 3 N 4 such as α-Si 3 N 4 , β-Si 3 N 4 and the self-prepared Si 3 N 4 by sol-gel method showed that the adsorbents doped with the self-prepared Si 3 N 4 had a superior cyclic adsorption property (68.34% after 10 cycles). The calcined CS (CCS) doped with 5 wt% self-prepared Si 3 N 4 , pre-calcined at 850 °C for 4 h (CCS–Si 3 N 4 -5-4-850) exhibited a higher conversion (>70% after 10 cycles, 57.09% after 20 cycles). The incorporation of Si 3 N 4 inhibited the sintering between the adsorbent particles, which is in favor of enhancing the cyclic adsorption durability. The adsorption kinetics showed that the activation energies of CCS-Si 3 N 4 -5-4-850 chemisorption and diffusion were estimated to be 68.17 kJ/mol and 102.34 kJ/mol, respectively, which are consistent with the actual adsorption process .