The catalytic properties of dispersed unsupported Mo sulfide catalysts in eugenol hydrotransformation were studied under the in situ hydrogen generation conditions provided by steam conversion of carbon monoxide. Active component particles were formed directly in the reaction medium by high-temperature decomposition–sulfidization of oil- or water-soluble precursors in the presence of elemental sulfur (sulfiding agent). Experiments under typical conditions (Т = 340°C, р(СО) =5 MPa (at 25°C), t = 6 h, Mo : eugenol = 1 : 65, ω(Н2О) = 20 wt
Because combustion produces sulfur oxides and traditional hydrodesulfurization struggles to remove refractory thiophenic species, sulfur-containing compounds in petroleum fuels continue to pose a significant environmental and refining challenge. In order to selectively transform refractory sulfur compounds into more polar sulfoxides and sulfones that can be removed from the fuel, oxidative desulfurization (ODS) has garnered a lot of interest. Focusing on catalyst–oxidant interactions, active-site chemistry, support characteristics, metal dispersion, acidity, pore architecture, and mass-transfer effects, this paper critically examines the chemical and structural factors that influence ODS performance. The debate distinguishes between the inherent oxidation activity of active species and the supportive function of porous materials, emphasizing the impact of oxidant identity and reaction environment on the creation of reactive oxygen species. Catalytic systems supported by alumina, silica, activated carbon, graphene, zeolite, and composites are studied in depth, as well as dual-active and multifunctional structures. Rather than directly comparing reported sulfur-removal efficiencies, the review examines catalytic performance in terms of fuel composition, sulfur speciation, oxidant activation, catalyst dose, reactor architecture, and catalyst stability. The primary limits of oxidant consumption, metal leaching, pore obstruction, regeneration, separation, and scale-up are also examined. Lastly, hierarchical porosity, regulated metal-support interactions, multifunctional active sites, catalytic recyclability, and intensified ODS reactors are highlighted as aspects of future catalyst research.
This study is the first to investigate Pt-Pd catalysts supported on untreated and dealuminated halloysite nanotubes (HNT and HNT-t, respectively) in the hydrogenation of diaromatic (naphthalene) and monoaromatic (benzene, toluene, ethylbenzene) hydrocarbons. Pre-dealumination of halloysite with a concentrated hydrochloric acid solution increases the specific surface area (from 65 to 154 m2/g), acidity (from 177 to 317 μmol NH3/g), and the Si/Al ratio (from 0.90 to 1.35). The deposition of active species by incipient wetness co-impregnation yields Pt and Pd loadings of 0.19 and 0.35 wt
This review examines the use of acid gases, primarily hydrogen sulfide (H2S) and carbon dioxide (CO2), in enhanced oil recovery (EOR) applications. The study synthesizes laboratory, simulation, and field-scale research to evaluate the technical mechanisms, environmental implications, and economic feasibility of acid-gas-based EOR. Key findings indicate that H2S-rich injection can significantly reduce minimum miscibility pressure, improve oil swelling and viscosity reduction, and enhance sweep efficiency compared to conventional CO2 or hydrocarbon gas injection. However, challenges such as sulfur and asphaltene precipitation, corrosion risks, and operational safety constraints must be carefully managed. Compared with alternative EOR techniques, acid gas injection offers the unique advantage of combining incremental oil recovery with emissions reduction through subsurface disposal. This review identifies critical research gaps related to long-term geochemical effects, solids precipitation control, and economic optimization under regulatory constraints. Overall, acid gas EOR represents a promising pathway to integrate recovery enhancement with environmental stewardship in sour hydrocarbon reservoirs.
