Characterization study of NiMo/SiO2-Al2O3 spent hydroprocessing catalysts for heavy oils

International audienceNiMo/SiO2-Al2O3 spent catalysts were obtained after the hydroprocessing of Maya crude oil in a fixed-bed up-flow reactor. The textural properties, metal content, carbon deposition and sulfide phase of spent catalysts were studied and compared with those of fresh catalysts. Scanning electron microscopy was used to study the deposit of nickel and vanadium, and the total metal content was determined by atomic absorption. The sulfide phase was analyzed with the use of infrared spectroscopy technique. Moreover, the catalytic activity of spent catalysts was evaluated with cumene hydrocracking and compared with the catalytic activities of fresh catalysts. The characterization results show that the silica-alumina NiMo catalysts are more sensitive to metal deposition than carbon deposition because of their porous structure which provokes pore mouth plugging and the decrease of the NiMoS active sulfide phase. The results show that optimizing the catalyst resistance to deactivation requires a trade-off between the support acidity and macro-mesoporosity. (C) 2013 Elsevier B.V. All rights reserved

An operando diffuse reflectance FT-IR study of CO methanation over supported nickel catalysts

International @ INGENIERIE+FRM:YSC:CMIInternational audienceNon

Understanding deactivation processes during bio-syngas methanation: DRIFTS and SSITKA experiments and kinetic modeling over Ni/Al2O3 catalysts

SSCI-VIDE+ECI2D:ING+DLR:FRM:YSC:CMIInternational audienceDRIFT

Identification of the carbonaceous compounds present on a deactivated cobalt based Fischer-Trospch catalyst resistant to “rejuvenation treatment”

International audienc

Synthesis, characterization and study of lanthanum phosphates as light alcohols dehydration catalysts

XPS:RMN+ECI2D+LMA:CLO:PAF:JMIInternational audienceFour preparation methods have been developed for the synthesis of lanthanum orthophosphate catalysts, which are shown to be active and selective catalysts for the dehydration of light alcohols (C-2 to C-4). Their crystallinity, surface area, surface composition and acid-base properties appear to differ according to the preparation method used. The most important parameter influencing their catalytic properties appears to be their surface composition since this has a direct influence on their surface acidity. All of the solids presented weak and moderately strong Bronsted and Lewis acid sites, and only weak basic sites in low quantities. These acid-base properties resulted in the prevalence of an E-1-type mechanism for 1-butanol dehydration. Bronsted acid sites, which appear as the most efficient sites, are associated with the presence of an excess of phosphorus at their surface and from spectroscopic data this is attributed to (H2PO4)(-3+n) (n=1 or 2) species from spectroscopic data. The prevalence of these species and their optimum surface distribution make them extraordinarily efficient and ultra-selective for the dehydration of several alcohols. Published by Elsevier B.V

HIF-prolyl hydroxylase 2 inhibition enhances the efficiency of mesenchymal stem cell-based therapies for the treatment of critical limb ischemia

International audienceUpregulation of hypoxia-inducible transcription factor-1a (HIF-1a), through prolyl-hydroxylase domain protein (PHD) inhibition, can be thought of as a master switch that coordinates the expression of a wide repertoire of genes involved in regulating vascular growth and remodeling. We aimed to unravel the effect of specific PHD2 isoform silencing in cell-based strategies designed to promote therapeutic revascularization in patients with critical limb ischemia (CLI). PHD2 mRNA levels were upregulated whereas that of HIF-1a were downregulated in blood cells from patients with CLI. We therefore assessed the putative beneficial effects of PHD2 silencing on human bone marrow-derived mesenchymal stem cells (hBM-MSC)-based therapy. PHD2 silencing enhanced hBM-MSC therapeutic effect in an experimental model of CLI in Nude mice, through an upregulation of HIF-1a and its target gene, VEGF-A. In addition, PHD2-transfected hBM-MSC displayed higher protection against apoptosis in vitro and increased rate of survival in the ischemic tissue, as assessed by Fluorescence Molecular Tomography. Cotransfection with HIF-1a or VEGF-A short interfering RNAs fully abrogated the beneficial effect of PHD2 silencing on the proangiogenic capacity of hBM-MSC. We finally investigated the effect of PHD2 inhibition on the revascularization potential of ischemic targeted tissues in the diabetic pathological context. Inhibition of PHD-2 with shRNAs increased postischemic neovascularization in diabetic mice with CLI. This increase was associated with an upregulation of proangiogenic and proarteriogenic factors and was blunted by concomitant silencing of HIF-1a. In conclusion, silencing of PHD2, by the transient upregulation of HIF-1a and its target gene VEGF-A, might improve the efficiency of hBM-MSC-based therapies.© AlphaMed Press 2013