NO_x Adsorption Mechanism of Coal-Based Activated Carbon Modified with Trace Potassium: In Situ DRIFTS and DFT Study

Abstract

A series of coal-based materials were prepared using a hydrothermal method combined with high-temperature CO2 activation. During sample preparation, K modification was performed to optimize the surface functional groups and pore structure. The NO x adsorption volume of each sample was evaluated in a simulated flue gas atmosphere. The physical and chemical parameters of the samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and temperature-programmed desorption of NO x and NO. In addition, the NO x adsorption mechanism of representative samples was explored by in situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations. The adsorption capacity of NO x and SO2 with NO x was also systematically investigated using cyclic adsorption and co-adsorption experiments, respectively. The results showed that the optimized KOH concentration is 0.4 g KOH/30 mL H2O. At this concentration, the material had a relatively good pore structure and abundant surface functional groups. The investigation of the mechanism revealed that pore structure optimization is important for increasing the NO x adsorption capacity on the surface of the coal-based materials, followed by functional group and then surface metal optimization. In addition, oxygen-containing active functional groups with moderately high C–O and R2CO contents can enhance the adsorption of NO to some extent. Optimizing the ratio of C–O to R2CO is critical for NO x adsorption. This study is significant for NO x adsorption removal technology.

Depicting the Nitric Oxide (NO) Chemical Sorption in Lithium Cuprate (Li2CuO2), through Thermokinetic and Spectroscopic Analyses

“…The first vibration band at 1260 cm −1 appeared at around 25 °C, reaching its maximum intensity at 100 °C, but disappearing at 275 °C, while the second one (1350 cm −1 ) was recorded from 275 to 500 °C. This low temperature band can be referred to bidentate nitrates, 41 while the high temperature band has been reported as monodentate nitrates. 42 These results match the NO-O 2 sorption process, followed by thermogravimetry (Figure 2).…”

Surface Effects of Trace CuMnCe Loading on Coal-Based Carbon Materials and Mechanisms of NOx Adsorption and Removal

“…The D-band reflects the disorder and lattice defects in the graphite crystal structure, while the G-band arises from the vibration mode of the sp 2 hybridized carbon atoms in the graphite lattice, corresponding to the E 2g symmetry . The intensity ratio of the D-band to the G-band ( I D / I G ) is commonly used to estimate the disorder and crystalline structure in carbon materials . With an increase in metal loading, the I D / I G ratio gradually decreases, indicating a reduction in surface defects and an enhancement in the degree of graphitization .…”

“…26 The intensity ratio of the D-band to the G-band (I D /I G ) is commonly used to estimate the disorder and crystalline structure in carbon materials. 27 With an increase in metal loading, the I D /I G ratio gradually decreases, indicating a reduction in surface defects and an enhancement in the degree of graphitization. 28 Research has indicated that a lower degree of graphitization indicates a higher proportion of disordered carbon structures in the catalyst, which supports the formation of porous carbon materials.…”

Review on Coal-Based Activated Carbon: Preparation, Modification, Application, Regeneration, and Perspectives

“…Wang et al 92 prepared AC from Zhundong coal using hydrochloric acid and nitric acid as activators and subsequently modified it with KOH. The results showed that the AC had the highest pore structure when the KOH content was 0.05 g KOH/ 30 mL H 2 O. Li et al 93 modified CAC by heat treatment, by sodium hydroxide impregnation, and by ammonia solution impregnation.…”