The removal of nitrogen from coal tar pitch (CTP) through the hydrodenitrogenation (HDN) of CTP and its molecular behavior were evaluated in the presence of NiMo/γ-alumina and CoMo/γ-alumina catalysts. Fourier transform ion cyclotron resonance mass spectrometry with atmospheric pressure photoionization was used to analyze the complicated chemical classes and species of CTP and the treated products at the molecular level. Nitrogen species were qualitatively analyzed before and after hydrotreatment. A single-stage hydrotreatment with an HDN catalyst resulted in a high sulfur removal performance (85.6–94.7%) but a low nitrogen removal performance (26.8–29.2%). Based on relative abundance analyses of nitrogen and binary nitrogen species, C_cH_h-N_nS_s was the most challenging species to remove during HDN treatment. Furthermore, prior hydrodesulfurization was combined with HDN treatment, and the dual hydrotreatments yielded a significantly improved nitrogen removal performance (46.4–48.7%).

The hydrodeoxygenation (HDO) of biomass pyrolysis oil (BPO) was evaluated in the presence of two commercial alumina-supported transition metal catalysts, NiMo/alumina-1 (NM1) and NiMo/alumina-2 (NM2). The study explored two characteristic aspects: how HDO reaction conditions affected the oxygen content, density, and boiling point distribution of BPO with varying temperature and HDO reaction time, and the roles of catalysts. Characterizations of HDO-treated oils included elemental analysis, GC-MS, SIMDIS, ¹³C NMR, and ¹H NMR, and characterizations of catalysts included NH₃-TPD, XRF, and TPO-MS analysis. The results show that both NM1 and NM2 catalysts removed oxygenated compounds effectively, which led to decreases in density and shifts toward higher boiling point distributions of BPO. Compared to the NM1 catalyst, NM2 had a higher acidity and enhanced HDO activity. The best HDO reaction performance was achieved in the presence of the NM2 catalyst at 300 °C. Furthermore, HDO reactions showed a significant amount of CO₂, CH₄, C₂H₆, and C₃H₈, which suggests that HDO reactions proceeded via a series of reactions of decarboxylation, water–gas shift, and methanation. In addition, hydrocarbon fraction tests suggested a favorable potential for the blending of HDO-treated biomass pyrolysis oil (HDO-BPO) with petroleum-derived fractions.

Acetaldehyde (CH₃CHO) in the atmosphere is associated with adverse health effects. Among the various options for use in removing CH₃CHO, adsorption is often employed because of its convenient application and economical processes, particularly when using activated carbon. In previous studies, the surface of activated carbon has been modified with amines to remove CH₃CHO from the atmosphere via adsorption. However, these materials are toxic and can have harmful effects on humans when the modified activated carbon is used in air-purifier filters. Therefore, in this study, a customized bead-type activated carbon (BAC) with surface modification options via amination was evaluated for removing CH₃CHO. Various amounts of non-toxic piperazine or piperazine/nitric acid were used in amination. Chemical and physical analyses of the surface-modified BAC samples were performed using Brunauer–Emmett–Teller measurements, elemental analyses, and Fourier transform infrared and X-ray photoelectron spectroscopy. The chemical structures on the surfaces of the modified BACs were analyzed in detail using X-ray absorption spectroscopy. The amine and carboxylic acid groups on the surfaces of the modified BACs are critical in CH₃CHO adsorption. Notably, piperazine amination decreased the pore size and volume of the modified BAC, but piperazine/nitric acid impregnation maintained the pore size and volume of the modified BAC. In terms of CH₃CHO adsorption, piperazine/nitric acid impregnation resulted in a superior performance, with greater chemical adsorption. The linkages between the amine and carboxylic acid groups may function differently in piperazine amination and piperazine/nitric acid treatment.