Structure and activity of unsupported NiWS2 catalysts for slurry phase hydrocracking of vacuum residue: XAFS studies

BC6N Monolayer as a Potential VOC Adsorbent in Mitigation of Environmental Pollution: A Theoretical Perspective

Rapid economic growth has led to severe air pollution, which poses threats to both the environment and public health. Among the major contributors to this issue are volatile organic compounds (VOCs), the abatement methods of which have received considerable attention from the research community. Recently, an adsorption technology employing two-dimensional monolayers has emerged as a promising strategy for VOC control. In the current investigation, we examined the adsorption behaviors of three prevalent VOCs, namely, acetone, benzene, and tetrachloromethane, on both pristine and Pd-doped BC6N monolayers. Through first-principles calculations based on density functional theory, it was revealed that pristine BC6N adsorbs acetone, benzene, and tetrachloromethane with modest adsorption energies of -0.003, -0.036, and -0.017 eV, respectively. These weak interactions make the adsorbate-adsorbent systems especially unstable, causing the VOCs to desorb from the pristine monolayer under increased ambient temperature or other environmental disturbances. The introduction of an interstitial Pd dopant has induced a significant improvement in the adsorption performance of the BC6N monolayer. Specifically, the values of adsorption energy for acetone and benzene on the Pd-doped BC6N monolayer experience a remarkable increase, measuring -0.745 and -1.028 eV, respectively. Moreover, the charge transfer is enhanced along with reduced adsorption distances, indicating strong chemisorption of acetone and benzene on the Pd-doped BC6N monolayer. Our results establish the Pd-doped BC6N monolayer as an efficient adsorbent for the toxic gases, particularly acetone and benzene, carrying practical implications for air quality improvement and environmental sustainability.

Atomic coordination structural dynamic evolution of single-atom Mo catalyst for promoting H2 activation in slurry phase hydrocracking

Development of efficient catalysts with high atomic utilization and turnover frequency (TOF) for H₂ activation in slurry phase hydrocracking (SPHC) is crucial for the conversion of vacuum residue (VR). Herein, for the first time, we reported a robust and stable single atoms (SAs) Mo catalyst through a polymerization-pyrolysis-in situ sulfurization strategy for activating H₂ in SPHC of VR. An interesting atomic coordination structural dynamic evolution of Mo active sites was discovered. During hydrocracking of VR, the O atoms that coordinated with Mo were gradually replaced by S atoms, which led to the O/S exchange process. The coordination structure of the Mo SAs changed from pre-reaction Mo-O₃S₁ to post-reaction Mo-O₁S₃ coordination configurations, promoting the efficient homolytic cleavage activation of H₂ into H radical species effectively. The evolved Mo SAs catalyst exhibited robust catalytic hydrogenation activity with the per pass conversion of VR of 65 wt%, product yield of liquid oils of 93 wt%, coke content of only 0.63 wt%, TOF calculated for total metals up to 0.35 s^-1, and good cyclic stability. Theoretical calculation reveals that the significant variation of occupied Mo 4d states before and after H₂ interaction has a direct bearing on the dynamic evolution of Mo SAs catalyst structure. The lower d-band center of Mo-O₁S₃ site indicates that atomic H diffusion is easy, which is conducive to catalytic hydrogenation. The finding of this study is of great significance to the development of high atom economy catalysts for the industrial application of heavy oil upgrading technology.

Hydrotreating of Waste Tire Pyrolysis Oil over Highly Dispersed Ni2P Catalyst Supported on SBA-15

A highly dispersed nickel phosphide catalyst supported on SBA-15 was prepared and tested for the hydrotreating of tire pyrolysis oil (TPO). Physicochemical properties of the prepared catalyst were analyzed by CO uptake chemisorption, BET, TEM, and X-ray diffraction (XRD). An advanced technique with gas chromatography equipped with mass spectrometry and atomic emission detector was applied to investigate carbon-, sulfur-, and nitrogen-containing compounds in TPO. Hydrotreating tests were carried out in a fixed-bed continuous flow reactor at 350 °C, 3.0 MPa, and LHSV of 0.5 h−1. The Ni2P/SBA-15 exhibited an HDS conversion of 89.3% and an HDN conversion of 60.7%, which was comparable to the performance of a commercial NiMoS catalyst under the same conditions.