HDS and HDN activity of (Ni,Co)Mo binary and ternary nitrides prepared by decomposition of hexamethylenetetramine complexes

RAFFINAGE+#34:MVR:PA

Compensation effect and volcano curve in toluene hydrogenation catalyzed by transition metal sulfides

Guernalec, N. Geantet, C. Cseri, T. Vrinat, M. Toulhoat, H. Raybaud, P.Within the framework of volcano curves, a kinetic study of toluene hydrogenation catalyzed by transition metal sulfides highlights the variation of the apparent kinetic parameters as a function of the ab initio sulfur-metal bond energy descriptor and sulfo-reductive reaction conditions

Dual Effect of H

Recent progresses achieved by quantum molecular modeling techniques enabled the rational interpretation of catalytic trends of series of transition metal sulfide catalysts. Empirical volcano curves can be explained by microkinetic models including chemical descriptors calculated at an ab initio level. This approach was successfully applied in the field of hydrotreating catalysis using the metal-sulfur bond energy descriptor. The purpose of the present work was to extend this approach by exploring the effect of reaction conditions (partial pressure of H2S) on the volcano curve. On the one hand, high resolution transmission electron microscopy (HRTEM) images combined with molecular modeling of morphologies and surfaces exposed by catalysts provide an estimate of the number of potential active sites. This approach is illustrated for the relevant case of unsupported or alumina supported Co9S8 sulfide. On the other hand, an improved microkinetic model is proposed in order to reflect the dual effects of H2S observed in the hydrogenation of toluene : an inhibiting effect for MoS2, Rh2S3, RuS2, NiMoS and a promoting effect for Cr2S3 et Co9S8. The experimental results and kinetic modeling reveal that the maximum of the volcano curve and thus the optimal sulfide catalyst depends closely on the partial pressure of H2S

Nature, structure and strength of the acidic sites of amorphous silica alumina: An IR and NMR study

International audienc

New Approaches to the Synthesis of Highly HDS Active Silica-Supported Nickel Phosphide Catalysts

internationa

A Novel Approach to the Synthesis of Silica-Supported Nickel Phosphide Catalysts using Nickel Thiophosphate as Precursor

internationa

A novel approach to the synthesis of unsupported nickel phosphide catalysts using nickel thiophosphate as precursor

International audienceNickel thiophosphate, NiPS3 synthesized at room temperature using a soft chemistry approach (a-NiPS3) has been successfully used as precursor for low-temperature preparation of unsupported nickel phosphide. Using Raman spectroscopy and EXAFS, comparison with a wellcrystallized NiPS3 reference (c-NiPS3) first confirmed that nickel thiophosphate can be effectively obtained at low temperatures of preparation. In situ XRD diffraction and EXAFS showed that Ni2P was obtained by the reduction of a-NiPS3 at a temperature as low as 573 K. For c-NiPS3, slower kinetics of reduction first led to the formation of an intermediate richer phosphorus-containing nickel phosphide phase, Ni5P4 at a temperature of reduction of 623 K while Ni2P started being formed at 773 K. Under hydrodesulfurization (HDS) thiophene catalytic conditions (613 K, 2.8 mol% thiophene/H2), a-NiPS3 was decomposed into a mixture of Ni2P and Ni5P4 while c-NiPS3 was converted into Ni5P4. Both nickel phosphide catalysts exhibit much higher activities compared to a MoS2 reference. Ni5P4 exhibited a specific activity (per gram of catalyst) seven times as high as for MoS2