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Results and performances of the QEXAFS double monochromator of the SAMBA beamline (Synchrotron SOLEIL) are presented. The device is capable of speeds of up to 40 Hz, while giving the user the possibility to choose the amplitude of the scan from 0.1° to 4° in a few seconds. The device is composed of two independent units and it is possible to perform scans alternating between two different crystals, literally jumping from low (4 keV) to high (37 keV) energies.

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Carbon nanofibers (CNFs) were functionalized with aryl sulfonic acid groups using in situ diazonium coupling. The use of diazonium coupling yielded an acidic carbon material, in which the introduced acidic groups are readily accessible to the triglyceride substrate. The material is an efficient catalyst for the transesterification of triolein and methanol, outperforming conventional sulfonated carbons in both stability and activity per acid site. Upon comparing CNFs with varying degrees of functionalization, a linear correlation between sulfonic acid sites and catalytic performance was found.

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For the first time, the sulfidation process of a bimetallic NiMo catalyst supported on alumina has been followed by combining time-resolved laser Raman spectroscopy (LRS) and X-ray absorption spectroscopy (XAS) quasi simultaneously at both Ni and Mo K edges. Multivariate data analysis reveals that the thermal activation upon 15% H2S/H2 atmosphere of a dehydrated-calcined NiMo­(VI) catalyst involves (i) a 5-stepped mechanism with oxysulfided or fully sulfided Mo intermediate species and (ii) a direct transformation of oxidic nickel species into NiS x and NiMoS ones. Complementary information extracted from LRS and Quick-XAS data permitted to identify at the early stage of the sulfidation the trimeric Mo­(V/VI) oxysulfide species [Mo3(μ2O)4(μ2S)­μ2{S2}­(Ot)2(St)3] grafted to the support surface, which is quickly transformed into the Mo­(IV) intermediate species [Mo3(μ3S)­(μ2S)2μ2{S2}­(Ot)2{S2}t]. Above 190 °C, the Mo­(IV) second intermediate is transformed into Mo­(IV)­S3, itself transformed into the final Mo­(IV)­S2 at T > 220 °C. Thanks to the unambiguous comparison of sulfidation kinetics for both metals the incorporation of promoter into the extended sulfidic molybdenum-based phase has been unprecedentedly related to the formation of the MoS3 intermediate species.

The structure of oxidic precursors of supported NiMo hydrodesulfurization catalysts has been investigated indepth by the combination of laser Raman spectroscopy and Xray absorption spectroscopy measured at the Mo and Ni K edges at the different stages of the preparation. The oxidic catalysts were prepared by incipient wetness impregnation of δ-alumina with a solution obtained by dissolving MoO 3 in H 2 O 2 and subsequently adding Ni(NO 3 ) 2 ·6H 2 O in this asprepared solution (8 wt % MoO 3 ; 2 wt % NiO). The formation of the 6-molybdoaluminate Anderson-type heteropolyanion (AlMo 6 O 24 H 6 ) 3− and of a mixture of oxo−hydroxo nickel species and bulk and/or surface NiAl-layered double hydroxide dispersed at the surface of the support has been identified after drying. Upon further thermal treatment at 723 K under dried air, calcined dehydrated catalyst is constituted of highly distorted isolated or partially condensed tetrahedral Mo units with terminal mono-oxo groups and of bulk and/or surface NiAl 2 O 4 -type and NiO-type species. After further exposure of the calcined catalyst to air moisture, a partial recovery of the Anderson-type molybdenum heteropolyanion and NiAl-layered double hydroxide species is evidenced by X-ray absorption spectroscopy. The nature and dispersion of active species formed after sulfidation under H 2 S/H 2 of the different oxidic catalysts (dried-NiMo, dehydrated-calcined NiMo, and calcined-NiMo samples) are finally discussed in light of the structure of the parent oxidic precursors.