High pressure cell for edge jumping X-ray absorption spectroscopy : Applications to industrial liquid sulfidation of hydrotreatment catalysts

International audienceA new analytical cell to perform liquid sulfidation of HDS catalysts in industrial conditions was developed. It enables the alternate recording of time-resolved Mo and Co K edges X-ray Absorption spectra of bimetallic catalysts under high pressure (30 bar) and temperature (350°C) during the same reaction. Thanks to this cell, a comparative study of the species formed upon gas (1 bar, 15% H 2 S/H 2) and liquid sulfidation (30 bar, H 2 /gas oil/4% DMDS) of a CoMoP/Al 2 O 3 HDS catalyst was carried out, together with a discussion on the evolution of the concentration profiles upon activation. Different Mo and Co-based chemical species are involved during gas and liquid sulfidation. On one hand, in industrial liquid sulfidation, polymolybdate species are transformed into depolymerized oxides, then into an oxysulfide, a MoS x species and finally into MoS 2. On the other hand, gas sulfidation skips the depolymerization process because of the immediate supply of H 2 S at the beginning of the process and proceeds under a stepwise transformation of oxide into oxysulfide, itself into MoS 3 species and finally into MoS 2. Cobalt species under gas sulfidation goes through a CoS 2 intermediate whereas in liquid sulfidation, it is a 4-fold coordinated Co oxide species. Irrespective to the activation route, mixture of Co 9 S 8 and CoMoS is obtained at advanced sulfidation stage (T> 200°C). Graphical Abstract Quick XAS in situ cell Raman Probe H 2 Gas oil + DMDS 350 C 30 bar Synchrotron radiation Co K edge Mo K edge DMDS decomposition CH 4 H 2 S 232 C 284 C 2 Highlights  A high pressure cell has been developed to study the liquid sulfidation of HDS catalyst by X-ray Absorption Spectroscopy  Co and Mo local orders are studied alternatively during the same reaction  The sulfidation mechanism depends on the activation process  The sulfidation of Co and Mo in liquid phase mainly occurs when DMDS is decomposed into H 2 S between 225°C and 350°C. Gas sulfidation starts at room temperature and is completed at 400°

Operanto magnetic measurements : a new approach to characterise cobalt catalysts during activation and Fischer-Tropch synthesis

International @ INGENIERIE+LBC:YSCInternational audienceNon

A Rational Comparison of the Optimal Promoter Edge Decoration of HDT NiMoS

In order to gain a better understanding of the morphology and promoter edge content of the active phase of industrial HDT NiMoP catalysts in working conditions, a multi-technique study has been undertaken on a series of NiMoP catalysts with various Ni/Mo ratios. The combination of X-ray Photoelectron Spectroscopy (XPS), Transition Electron Microscopy (TEM), Density Functional Theory (DFT) modeling and catalytic testing (toluene hydrogenation) provided data to build a morphological model of NiMoS nanocrystallites. A parallel has been established with their CoMoS counterparts obtained in our previous work in order to emphasize differences arising from the promoter atom. This study confirms the importance of the presence of mixed Ni-Mo sites on the edges of the NiMoS nanocrystallites, and especially on the M-edge for reactions involving hydrogenation. These results provide new guidelines for future and ever more active catalysts

Synthesis and Catalytic evaluation of Mo(W)S2 1T polytype for Hydrotreating

SSCI-VIDE+ECI2D+SPL:PAFNational audienceIn the last decades a strong reduction of the sulfur content in fossil fuels was achieved. However, severe environmental regulations and new resources employed still demand more active and selective catalysts. To achieve it, an increase in intrinsic activity is requested for transition metal dichalcogenides (TMD). Thanks to sulphide edges promotion by nickel and cobalt, a modification in electronic properties of the edges leads to improved activity. However, considering the limited number of active edge sites, it would be extremely interesting to induce basal planes catalytic activity in order to drastically improve the number of active sites and their accessibility for reactants. Crystals of MoS2 can exist as different polymorphs, displaying a range of electronic and optical properties, i.e. depending on the Mo coordination within a single layer and the stacking order, it is possible to find three polytypes: 1T (Tetragonal), 2H (Hexagonal) and 3R (Rhombohedral). In the case of 2H and 3R polymorphs, each Mo has trigonal-prismatic coordination with the nearby S atoms, while for 1T-MoS2, Mo is coordinated in an octahedral manner

Synthesis and Catalytic evaluation of Mo(W)S2 1T polytype for Hydrotreating

SSCI-VIDE+ECI2D+SPL:PAFNational audienceIn the last decades a strong reduction of the sulfur content in fossil fuels was achieved. However, severe environmental regulations and new resources employed still demand more active and selective catalysts. To achieve it, an increase in intrinsic activity is requested for transition metal dichalcogenides (TMD). Thanks to sulphide edges promotion by nickel and cobalt, a modification in electronic properties of the edges leads to improved activity. However, considering the limited number of active edge sites, it would be extremely interesting to induce basal planes catalytic activity in order to drastically improve the number of active sites and their accessibility for reactants. Crystals of MoS2 can exist as different polymorphs, displaying a range of electronic and optical properties, i.e. depending on the Mo coordination within a single layer and the stacking order, it is possible to find three polytypes: 1T (Tetragonal), 2H (Hexagonal) and 3R (Rhombohedral). In the case of 2H and 3R polymorphs, each Mo has trigonal-prismatic coordination with the nearby S atoms, while for 1T-MoS2, Mo is coordinated in an octahedral manner

Operando characterisation by DRX-DRIFT-GC of cobalt catalysts during the Fischer Tropsch synthesis

International @ INGENIERIE+LBC:YSCInternational audienceNon