Removal of mercaptan from natural gas condensate using N-doped carbon nanotube adsorbents: Kinetic and DFT study

Nitrogen-doped carbon nanotube (N-CNT) adsorbents were prepared through the chemical vapor deposition method at 1000 °C by using camphor and urea. The desulfurization of liquid stream by using CNT and N-CNTs was investigated. The effects of various adsorption parameters, including time, temperature, adsorbent loaded mass, and initial concentration of tertiary butyl mercaptan (TBM), on adsorptive desulfurization were studied. N-CNTs were characterized by field emission scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, elemental analysis (CHN), and N adsorption/desorption. Kinetic studies were carried out, and kinetic data were fitted using a pseudo-second-order model. The adsorption equilibrium data and their isotherm models were in good agreement with the Freundlich model. The sulfur concentration after adsorption was evaluated using a total S analyzer. Finally, this study demonstrated that the incorporation of N into the CNT structure resulted in an adsorption capacity of approximately 63.1 mg/g, which was 45% higher than that of pristine CNT. Density functional theory calculations were also performed to understand the effects of TBM adsorption on the N-CNTs.