Adsorption Characteristics of Gas Molecules (H2O, CO2, CO, CH4, and H2) on CaO-Based Catalysts during Biomass Thermal Conversion with in Situ CO2 Capture

Abstract

Biomass thermochemical conversion with in situ CO2 capture is a promising technology in the production of high-quality gas. The adsorption competition mechanism of gas molecules (H2O, CO2, CO, CH4, and H2) on CaO-based catalyst surfaces was studied using density functional theory (DFT) and experimental methods. The adsorption characteristics of CO2 on CaO and 10 wt % Ni/CaO (100) surfaces were investigated in a temperature range of 550–700 °C. The adsorption energies were increased and then weakened, reaching their maximum at 650 °C. The simulation results were verified by CO2 temperature-programmed desorption (CO2-TPD) experiments. By the density of states and Mulliken population analysis, CaO doped with Ni caused a change in the electronic structure of the Osurf atom and decreased the C–O bond stability. The molecular competition mechanism on the CaO-based catalyst surface was identified by DFT simulation. As a result, the adsorption energies decreased in the following order: H2O > CO2 > CO > CH4 > H2. The increase of CO2 adsorption energy on the 10 wt % Ni/CaO surface, compared with the CaO surface, was the largest among those of the studied molecules, and its value increased from 1.45 eV to 1.81 eV. Therefore, the 10 wt % Ni/CaO catalyst is conducive to in situ CO2 capture in biomass pyrolysis.

Hydrogen Production from Catalytic Pyrolysis of Phenol as Tar Model Compound in Magnetic Field

“…In contrast, the production of CH 4 and CO 2 underwent little change, only exhibiting slight modifications. Due to the marginal improvement in the yield of H 2 and conversion of phenol at 700 • C in comparison with that at 650 • C, alongside observing the highest content of H 2 volume at 650 • C, it was concluded that the most appropriate temperature for catalytic pyrolysis of phenol to hydrogen is 650 • C. This finding is consistent with preceding research [29,30].…”

Catalytic Aldol Condensation of 5‐Hydroxymethylfurfural and its Synthesis from Concentrated Feed of Carbohydrates

“…The basicity of both catalysts was measured by CO 2 -TPD (Figure 5). CaO exhibits a desorption band at 604 °C with a CO 2 uptake of 63.4 μmol CO2 /g cat ascribed to strong basic sites as reported in the literature [34]. BaO exhibits two desorption bands centered at 400 °C and 603 °C, pointing out a combination of sites with moderate and strong basicity.…”

CO2 adsorption on Miscanthus × giganteus (MG) chars prepared in different atmospheres

“…The N2 adsorption data showed that the SBET, Vtotal, and Vmicro of He-600J and He-800J were significantly lower than those of N2-J and CO2-J prepared at the same temperature, but the difference in CO2 adsorption capacity was small. The main reason was that inert gas He has a strong protective effect, resulting in the surface of He-J chars were rich in hydroxyl, amino and other functional groups, which could improve their adsorption capacity through chemical adsorption [41][42][43][44]. To understand the CO2 adsorption process on MG chars, it was not only necessary to determine the optimal char production atmosphere/temperature but also to investigate the effect of high-temperature desorption on the cyclic regeneration of the products.…”