MoS2 and Ni-promoted MoS2 catalysts supported on γ-Al2O3, siliceous SBA-15, and Zr- and Ti-modified SBA-15 were explored for the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of o-propylaniline (OPA). In all cases, OPA reacted preferentially via initial hydrogenation, and DBT was converted through direct sulfur removal. HDN and HDS activities of MoS2 catalysts are determined by the dispersion of the sulfide phase. Ni promotion increased its dispersion and activity for DBT HDS and also increased the rate of HDN via enhancing the rate of hydrogenation. On nonpromoted MoS2 catalysts, HDS was strongly inhibited by NH3, and the addition of Ni dramatically reduced this inhibiting effect. The conclusion is that HDS is proportional to the concentration of Mo and Ni on the edges of sulfide particles. In contrast, the direct hydrodenitrogenation of OPA occurs only on accessible Mo cations and, hence, decreases with increasing Ni substitution. The nature of the supp...

Effects of the Support on the Performance and Promotion of (Ni)MoS2 Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

CO2 reforming of methane over highly active La-promoted Ni supported on SBA-15 catalysts: mechanism and kinetic modelling

Mesoporous SBA-15 materials with different morphologies were successfully synthesized through different methods by using pluronic P123 triblock copolymer (EO20PO70EO20) and cosurfactant (CTAB) as structure-directing agent. Moreover, highly ordered mesoporous Al-SBA-15 with a Si/Al molar ratio of 10 has been prepared with three different Al resources using post-synthesis methods. The characterization results of X-ray fluorescence spectroscopy, X-ray power diffraction, N2 adsorption–desorption and 27Al nuclear magnetic resonance spectroscopy revealed that the chemical grafting of aluminum chloride on the surface of SBA-15 was the best post-synthesis route for the preparation of Al-SBA-15 with different morphologies. The corresponding Al-SBA-15-supported NiMo hydrodesulfurization (HDS) catalysts with different morphologies were prepared and evaluated using DBT as a probe reactant. The sphere NiMo/AS-SP catalyst has higher dispersion degree of MoS2 slabs and more acid sites than other catalysts. The catalytic results showed that the morphologies and mesochannels of SBA-15 played an important role in the catalytic performance of DBT HDS over NiMo catalysts, especially in the diffusivity of DBT molecules in the catalysts, while they have little effect on the selectivity of DBT HDS. The kinetics investigations confirmed that the activity of DBT HDS over these catalysts followed the order: long-rod catalyst (NiMo/AS-LR) < hexagonal prism catalyst (NiMo/AS-HP) < short-rod catalyst (NiMo/AS-SR) < sphere catalyst (NiMo/AS-SP). The high activity of the last one was attributed to the superior diffusion of the supports and the better dispersion of the active components.

Synthesis of NiMo catalysts supported on mesoporous Al-SBA-15 with different morphologies and their catalytic performance of DBT HDS

Catalytic depolymerization of the hydrolyzed lignin over mesoporous catalysts.

A general mechanism for H2 activation by Lewis acid–transition metal (LA-TM) bifunctional catalysts has been presented via density functional theory (DFT) studies on a representative nickel borane system, (PhDPBPh)Ni. There are four typical H2 activation modes for LA-TM bifunctional catalysts: (1) the cis homolytic mode, (2) the trans homolytic mode, (3) the synergetic heterolytic mode, and (4) the dissociative heterolytic mode. The feature of each activation mode has been characterized by key transition state structures and natural bond orbital analysis. Among these four typical modes, (PhDPBPh)Ni catalyst most prefers the synergetic heterolytic mode (ΔG‡ = 29.7 kcal/mol); however the cis homolytic mode cannot be totally disregarded (ΔG‡ = 33.7 kcal/mol). In contrast, the trans homolytic mode and dissociative heterolytic mode are less feasible (ΔG‡ = ∼42 kcal/mol). The general mechanistic picture presented here is fundamentally important for the development and rational design of LA-TM catalysts in the f...

General H2 Activation Modes for Lewis Acid–Transition Metal Bifunctional Catalysts

Mesoporous Al-SBA-15 with different Si/Al molar ratio (10, 20, 30, and 40) was synthesized hydrothermally, and Mo–Ni catalysts were prepared by incipient wet impregnation method and characterized by different techniques. An impressive catalytic performance was observed on Mo–Ni/Al-SBA-15(10) for Methylcyclohexylamine conversion to hydrocarbons. The observed trend of activity is correlated with the aluminum content, and it is concluded that the variation in Si/Al ratio remarkably affects the hydrodenitrogenation ability of Al-SBA-15 supported Mo–Ni catalysts.

G. Deepa

Papers

Mo–Ni/Al-SBA-15 (Sulfide) Catalysts for Hydrodenitrogenation: Effect of Si/Al Ratio on Catalytic Activity