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

Abstract : A 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°C
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Submitted on : Friday, September 27, 2019 - 3:41:35 PM
Last modification on : Monday, January 10, 2022 - 10:16:07 AM
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C. Lesage, E. Devers, C. Legens, G. Fernandes, O. Roudenko, et al.. High pressure cell for edge jumping X-ray absorption spectroscopy : Applications to industrial liquid sulfidation of hydrotreatment catalysts. Catalysis Today, Elsevier, 2019, 336, pp.63-73. ⟨10.1016/j.cattod.2019.01.081⟩. ⟨hal-02299215⟩

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