Effect of Mg addition on the structure and performance of sulfide Mo/Al2O3 in HDS and HDN reaction

Comparative Study on the Hydrogenation of Naphthalene over Both Al2O3-Supported Pd and NiMo Catalysts against a Novel LDH-Derived Ni-MMO-Supported Mo Catalyst

Naphthalene hydrogenation was studied over a novel Ni-Al-layered double hydroxide-derived Mo-doped mixed metal oxide (Mo-MMO), contrasted against bifunctional NiMo/Al₂O₃, and Pd-doped Al₂O₃ catalysts, the latter of which with Pd loadings of 1, 2, and 5 wt %. Reaction rate constants were derived from a pseudo-first-order kinetic pathway describing a two-step hydrogenation pathway to tetralin (k ₁) and decalin (k ₂). The Mo-MMO catalyst achieved comparable reaction rates to Pd_2%/Al₂O₃ at double concentration. When using Pd_5%/Al₂O₃, tetralin hydrogenation was favored over naphthalene hydrogenation culminating in a k ₂ value of 0.224 compared to a k ₁ value of 0.069. Ni- and Mo-based catalysts produced the most significant cis-decalin production, with Mo-MMO culminating at a cis/trans ratio of 0.62 as well as providing enhanced activity in naphthalene hydrogenation compared to NiMo/Al₂O₃. Consequently, Mo-MMO presents an opportunity to generate more alkyl naphthenes in subsequent hydrodecyclization reactions and therefore a higher cetane number in transport fuels. This is contrasted by a preferential production of trans-decalin observed when using all of the Al₂O₃-supported Pd catalysts, as a result of octalin intermediate orientations on the catalyst surface as a function of the electronic properties of Pd catalysts.

Synthesis of NiW Supported on an Al-Modified Cubic Ia3d Mesoporous KIT-5 Catalyst and Its Hydrodenitrogenation Performance of Quinoline

Pure KIT-5 and a series of Al-KT-X materials modified by different amounts of aluminum were synthesized by a direct hydrothermal method and acted as supports for the catalysts of a quinoline hydrodenitrification reaction with the NiW active phases supported. The results of X-ray diffraction (XRD), N2 isotherm absorption-desorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) for the supports indicated that Al species were embedded into the framework of the KIT-5 materials with a large pore size, pore volume, and specific surface area. The Pyridine-Fourier transform infrared spectroscopy (Py-IR) result of the catalysts demonstrated that the addition of aluminum atoms enhanced the acidity of the catalysts. The results of the high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS) characterizations for the sulfide catalysts indicated that the embedded Al species could facilitate the dispersion of active metals and the formation of the active phases. Among all the catalysts, NiW/Al-KT-40 showed the maximal hydrodenitrogenation conversion (HDNC) due to its open three-dimensional pore structure, appropriate acidity, and good dispersion of active metals.

Ni-modified MoS2 nanoflake arrays with stepped sites on carbon nanotubes for efficient hydrodesulfurization of coal-to-liquid fuel

Carbon nanotube (CNT)-supported Ni-modified MoS₂ catalysts with ultra-high loading were synthesized with the assistance of citric acid. The morphology of the nanoflake arrays could be controlled to give abundant stepped sites, which favored the hydrogenation desulfurization pathway of dibenzothiophene. The catalyst exhibited excellent performance and stability for hydrodesulfurization of model oil and coal-to-liquid fuel.

Effect of TiO2-ZnO-MgO Mixed Oxide on Microbial Growth and Toxicity against Artemia salina

Mixed oxide nanoparticles (MONs, TiO₂–ZnO–MgO) obtained by the sol-gel method were characterized by transmission electron microscopy, (TEM, HRTEM, and SAED) and thermogravimetric analysis (TGA/DTGA–DTA). Furthermore, the effect of MONs on microbial growth (growth profiling curve, lethal and sublethal effect) of Escherichia coli, Salmonella paratyphi, Staphylococcus aureus and Listeria monocytogenes, as well as the toxicity against Artemia salina by the lethal concentration test (LC₅₀) were evaluated. MONs exhibited a near-spherical in shape, polycrystalline structure and mean sizes from 17 to 23 nm. The thermal analysis revealed that the anatase phase of MONs is completed around 480–500 °C. The normal growth of all bacteria tested is affected by the MONs presence compared with the control group. MONs also exhibited a reduction on the plate count from 0.58 to 2.10 log CFU/mL with a sublethal cell injury from 17 to 98%. No significant toxicity within 24 h was observed on A. salina. A bacteriostatic effect of MONs on bacteria was evidenced, which was strongly influenced by the type of bacteria, as well as no toxic effects (LC₅₀ >1000 mg/L; TiO₂–ZnO (5%)–MgO (5%)) on A. salina were detected. This study demonstrates the potential of MONs for industrial applications.

Recent Insights in Transition Metal Sulfide Hydrodesulfurization Catalysts for the Production of Ultra Low Sulfur Diesel: A Short Review

The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal of sulfur from typical refractory compounds. This review is separated into three very specific topics of the catalysts to produce ultra-low sulfur diesel. The first issue is the supported catalysts; the second, the self-supported or unsupported catalysts and finally, a brief discussion about the theoretical studies. We also inspect some details about the effect of support, the use of organic and inorganic additives and aspects related to the preparation of unsupported catalysts. We discuss some hot topics and details of the unsupported catalyst preparation that could influence the sulfur removal capacity of specific systems. Parameters such as surface acidity, dispersion, morphological changes of the active phases, and the promotion effect are the common factors discussed in the vast majority of present-day research. We conclude from this review that hydrodesulfurization performance of TMS catalysts supported or unsupported may be improved by using new methodologies, both experimental and theoretical, to fulfill the societal needs of ultra-low sulfur fuels, which more stringent future regulations will require.

Effect of Mg as Impurity on the Structure of Mesoporous γ-Al203: Efficiency as Catalytic Support in HDS of DBT

This work shows the study of two alumina materials synthesized from aluminum sulfate with different purity by hydrolysis-precipitation route. The main difference between the aluminum salt precursors was the lower cost of one of them which was due to the higher percentage of magnesium species as impurity. Both materials showed different mesoporous structure nano-fibrillar. The physic-chemical properties of these materials were studied by several characterization techniques as XRD, XRF, BET, 27Al MAS NMR, Pyridine adsorption FT-IR, FE-SEM/EDX, TEM and XPS. Furthermore, these materials were used as supports in the formulations of NiMo-based catalysts which were obtained by impregnation by the incipient wetness method of Ni and Mo salts in 3.3 and 15 wt. % respectively. The two NiMo/γ-Al2O3 sulfide catalysts were evaluated as catalysts in the reaction of hydrodesulphurization (HDS) of dibenzothiophene (DBT), using a high-pressure batch reactor at 350 °C and 3.1 MPa and time reaction of 5 h−1. The NiMo/γ-Al2O3 catalyst prepared by aluminum sulfate of low purity and lower cost exhibited the highest HDS efficiencies, 95 %, respectively, which were mainly ascribed to the presence of Mg (0.9 wt. %) as impurity.

AC. Characterisation and performance of hydrotalcite-derived CoMo sulphide catalysts for selective HDS in the presence of olefin

Infrared spectroscopy of adsorbed CO showed that, in hydrotalcite-derived CoMoMgAl catalysts, Co-promoted sites catalyse HDS, and un-promoted sites, hydrogenation.