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• High pressure cell developed to study the liquid sulfidation of HDS catalysts by XAS. • Co and Mo local orders are studied alternatively during the same reaction. • The sulfidation mechanism depends on the activation process. • Co and Mo are sulfided when DMDS is decomposed into H 2 S in liquid phase. • Gas sulfidation starts at room temperature and is completed at 400 °C. An analytical cell to perform liquid sulfidation (30 bar, H 2 /gas oil/4% DMDS) 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, unique information about the concomitant electronic and local order transformation occurring around Mo and Co upon liquid sulfidation of a CoMoP/Al 2 O 3 HDS catalyst has been obtained and discussed together with the ones recorded on a similar catalyst sulfided under academic gas sulfidation (1 bar, 15% H 2 S/H 2). A special emphasis on the evolution of the concentration profiles upon both activations has been carried out. On one hand, in industrial liquid sulfidation, polymolybdate species are slowly transformed into depolymerised oxides between room temperature and 230 °C, itself transformed abruptly into an oxysulfide, and then into a MoS x species mainly between 230 and 280 °C and finally into MoS 2. On the other hand, gas sulfidation skips the depolymerisation process because of the room temperature supply of H 2 S and proceeds under a stepwise slow 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 -like 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 above 200 °C. [ABSTRACT FROM AUTHOR]

Evolution in crystal, electronic and local atomic structures of Pt in ammonium hexachloroplatinate in the course of thermal decomposition in inert and reducing atmospheres have been studied by Powder X-Ray Diffraction (PXRD) and Quick X-ray Absorption Fine Structure (QXAFS) at Pt L 3 -edge for deeper understanding the thermally-induced solid state reaction and the formation of metallic nanoparticles. A three-step thermal decomposition mechanism of (NH 4) 2 [PtCl 6 ] in the inert atmosphere with the intermediate products Pt(NH 3) 2 Cl 2 and PtCl 2 has been found instead one-[G.Meyer, A.Möller, J. Less. Common. Met. 170 (1991) 327–331] and two-step one [Q.Kong, F.Baudelet, J.Han, S.Chagnot, L.Barthe, J.Headspith, R. Goldsbrough, F.E.Picca, O.Spalla, Sci. Rep. 2 (2012) 1018–1025] considered early. In the reducing atmosphere, the thermal decomposition is a two-step process with the formation of the intermediate PtCl 2. The best approach to determining the number of thermal decomposition steps turned out to be the express-analysis of QXAFS spectra offered in the papers, based on the simultaneous presentation of the most important parameters extracted from X-ray Absorption Near Edge Structure (XANES) and Fourier transformed Extended XAFS (EXAFS). This express-analysis was tested by comparison with results of various approaches such as conventional EXAFS fitting, linear combination fit (LCF), Multivariate Curve Resolution Alternating Least Squares method (MCR ALS). • Pt L 3 QXAFS: three- and two-step thermal decomposition mechanism of (NH 4) 2 [PtCl 6 ] in inert and reducing atmospheres, resp. • An offered express-analysis of QXAFS bases on the simultaneous presentation of the parameters of XANES and EXAFS. • Comparative analysis of the conventional EXAFS processing and MCR ALS revealed a number of shortcomings of MCR ALS. [ABSTRACT FROM AUTHOR]