Search results for "DESULFURIZATION"

Ternary transition metals sulfides in hydrotreating catalysis.

2007

International audience; Pure microcrystalline barium molybdate BaMoO4 and barium tungstate BaWO4 materials were prepared by molten flux reaction using alkali metal nitrates as reaction media. The obtained crystals have rhombic shape and expose mostly (111) crystallographic planes. Their mean size depends on the flux temperature and the nature of the alkali metal cation. Monomeric molybdate and tungstate used as precursors yield target products already at 673 K whereas if polymerized ammonium oxosalts were used, then higher temperatures were necessary to obtain barium salts. The optimal temperature for the preparation of pure crystals with well defined shape was found to be near 773 K. UV–vi…

Metabolic and process engineering for biodesulfurization in Gram-negative bacteria

2017

32 p.-2 fig.-1 tab.

Bio-polymeric Ionic Liquid Gels for the Desulfurization of Fuel

Fully aerobic bioscrubber for the desulfurization of H2S-rich biogas

2019

Abstract A fully aerobic bioscrubber for the desulfurization of H2S-rich biogas was developed in the present study by coupling an absorption column and a bubble column bioreactor. The bioscrubber treated H2S loading rates of 37, 59, and 100 g S mliquid−3 h−1 at gas residence times of 6.6, 4.1 and 2.4 min in the absorption column, respectively. Stable H2S removal efficiencies above 80% were recorded at all the conditions tested. The bioscrubber was robust towards short- and long-term operation shutdowns (5 and 18 days), the H2S removal performance being recovered after few hours. The aerated bubble column bioreactor was operated at slightly alkaline conditions (pH 8 ± 0.5), which prevented H…

Desulfurization: Critical step towards enhanced selenium removal from industrial effluents

2017

Abstract Selenium (Se) removal from synthetic solutions and from real Flue Gas Desulfurization (FGD) wastewater generated by a coal-fired power plant was studied for the first time using a commercial iron oxide impregnated strong base anion exchange resin, Purolite ® FerrIX A33E. In synthetic solutions, the resin showed high affinity for selenate and selenite, while sulfate exhibited a strong competition for both oxyanions. The FGD wastewater investigated is a complex system that contains Se (∼1200 μg L −1 ), SO 4 2− (∼1.1 g L −1 ), Cl − (∼9.5 g L −1 ), and Ca 2+ (∼5 g L −1 ), alongside a broad spectrum of toxic trace metals including Cd, Cr, Hg, Ni, and Zn. The resin performed poorly again…

Bacterial community analysis of a gas-phase biotrickling filter for biogas mimics desulfurization through the rRNA approach

2010

Abstract The bacterial composition of a lab-scale biotrickling filter (BTF) treating high loads of H 2 S was investigated by the rRNA approach. Two 16S rRNA gene clone libraries were established 42 and 189 d after reactor startup, while fluorescent in-situ hybridization (FISH) with DNA probes was performed throughout 260 d of reactor operation. Diversity, community structure and metamorphosis were studied from reactor startup to fully-established pseudo-steady state operation at near neutral pH and at an inlet H 2 S concentration of 2000 ppmv (load of 55.6 g H 2 S m −3  h −1 ). In addition, FISH was used for assessing the spatial distribution of sulfur-oxidizing bacteria (SOB) along the len…

Reactivity of arsenic compounds on trapping masses and role of the active phase

2019

The aim of the thesis is to study the reactivity of organic arsenic compounds on various recovery masses and to identify the role of the nature of the active phase and the reaction mechanisms involved. The active phase is composed of metals (Ni, Co, Mo, Cu, Zn, Fe, etc.), pure or in a mixture, in the reduced state or in the sulphide state. The selection of the metallic phases will be carried out by molecular modeling "ab initio", and the synthesis by impregnation of metallic salts on mesoporous aluminas). The reactivity of the solids will be studied in a static reactor on simplified model loads, with kinetic monitoring. The advanced characterization of the solids after synthesis and after r…

Synergetic effect of gold in Au/Pd catalysts during hydrodesulfurization reactions of model compounds

2003

Abstract The simultaneous formation of colloidal dispersions of Pd and Au metal particles protected by the organic polymer polyvinylpyrrolidone (PVP) in reducing alcohol solution was used for the synthesis of new silica-supported monometallic and bimetallic Au x Pd y catalysts with different x / y ratios. The samples, with a 2 wt% total metal loading, after air calcinations at 673 K to remove the PVP, were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and FTIR spectra of chemisorbed CO. Formation of alloyed Au x Pd y particles of different metal composition with consequent modification of their electronic and geometric properties was ascertained. The catalytic activi…

Effect of Gold on the HDS Activity of Supported Palladium Catalysts

2002

Abstract The effect of gold on palladium catalysts supported on amorphous aluminosilicate was investigated in the hydrodesulfurization of thiophene. A series of bimetallic AuxPdy catalysts was prepared by the slow deposition–precipitation method with decomposition of urea. The structural and surface properties of the samples were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy techniques at different stages of the catalyst life. After calcination at 673 K, gold-enriched solid solutions of approximately Au90Pd10 and Au80Pd20 composition were formed for all samples of different Au/Pd ratios, along with free palladium phases. Au80Pd20 was the prevailing phase. Hydrogen treat…

Sulfidation Mechanism of Pure and Cu-Doped ZnO Nanoparticles at Moderate Temperature: TEM and In Situ XRD Studies

2012

International audience; Sulfidation mechanism of pure and Cu-doped ZnO nanoparticles (Cu0.03Zn0.97O and Cu0.06Zn0.94O) at 250 and 350 degrees C was studied by transmission electron microscopy (TEM) and in situ synchrotron XRD. For nondoped ZnO, we observed by TEM that partial reaction with H2S is accompanied by the formation of voids at the ZnO/ZnS interface. This phenomenon (known as the Kirkendall effect) confirms that sulfidation of nanosized ZnO by gaseous H2S proceeds via the outward growth of ZnS: Zn2+ and O2- are transferred to the external (ZnS/gas) surface, where zinc is combined with sulfur and oxygen reacts with protons yielding H2O. During sulfidation of Cu-doped ZnO, the caviti…