Reforming natural gas for CO2 precombustion capture in combined cycle power plant.

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Modelisation numerique de chambres de combustion axisymetriques : application au projet Aladin

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1995 n.166 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Experimental Microkinetic Approach of De-NOx by NH3 on V2O5/WO3/TiO2 Catalysts. 3. Impact of Superficial WOz and VxOy/WOz Groups on the Heats of Adsorption of Adsorbed NH3 Species

SSCI-VIDE+ECI2D:ING+FGI:CGE:NOG:SLO:DBIInternational audienceThe present article is dedicated to the measurement of the individual heats of adsorption of adsorbed NH3 species on WO3/TiO2 and V2O5/WO3/TiO2 (a catalyst for the selective catalytic reduction of NOx by NH3 on stationary sources, briefly NH3-SCR) model and commercial solids by using an original experimental procedure (adsorption equilibrium infrared spectroscopy, AEIR) developed in parts 1 [Giraud et al. J. Phys. Chem. C 2014, 118, 15664] and 2 [Giraud et al. J. Phys. Chem. C 2014, 118, 15677] for the adsorbed NH3 species on TiO, and V2O5/TiO2 solids. In agreement with the literature, Raman and Fourier transform infrared spectra indicate the presence of well-dispersed VxOy and WOz entities on the different solids. For NH3 adsorption at pressure P-a < 0.5 IrPa and temperature T-a in the range 300-673 K, the modifications of the V=O and W=O overtone IR bands indicate that these entities are involved in the adsorption of NH3, forming NH3ads-L, and NH4+ species on Lewis and Br-misted sites, respectively. For T-a = 300 K, it is shown that four adsorbed NH3 species are formed on the WOz- containing catalysts: two are adsorbed on Lewis sites, named NH3ads-L1 and NH3ads-L2, and two are adsorbed on Bronsted sites, named NH4+-1 and NH4+-2 ("1" and "2" indicate the increasing order of stability of the different species). Using the delta(as) IR band characteristic of the NH3ads-L (similar to 1600 cm(-1)) and NH4+ (similar to 1445 cm(-1)) species, it is shown that the AEIR method provides the individual heats of adsorption of the four adsorbed species at low and high coverages of their adsorption sites. For instance, on a model 0.5% V2O5/6% WO3/TiO2 catalyst the heats of adsorption of the two more stable species (which slightly change with the exact composition of the solid) at low and high coverages of the sites are 105 and 148 kJ/mol for NH3ads-L2 and 78 and 135 kJ/mol for the NH4+-2 species, respectively. These values indicate that the presence of WOz increases significantly the heat of adsorption of the NH4+ species, as compared to TiO2 and V2O5/TiO2, explaining that both NH3(ads-L2) and NH4+-2 species can be present in the experimental conditions of NH3-SCR

Experimental Microkinetic Approach of De-NO by NH3 on V2O5/WO3/TiO2 Catalysts. 2. Impact of Superficial Sulfate and/or VxOy Groups on the Heats of Adsorption of Adsorbed NH3 Species

AIR:RAFFINAGE:INGENIERIE:SURFACES+FGI:CGE:NOG:SLO:DBIThe present article is dedicated to the impacts of sulfatation and/or VxOy deposition on TiO2 supports on the individual heats of adsorption of adsorbed NH3 species. The S and V loadings are similar to those of TiO2 based commercial catalysts for the selective catalytic reduction of NOx by NH3: NH3-SCR. Two original experimental procedures are used, namely, adsorption equilibrium infrared spectroscopy (AEIR) and temperature-programmed adsorption equilibrium (TPAE). They have been developed in previous works and adapted in Part 1 for the species formed by the adsorption of NH3 on a sulfate free TiO2 support (P25 from Degussa). In agreement with the literature, Raman and FTIR spectroscopies show that the impregnation of the sulfate-free and sulfated TiO2 supports by the vanadium precursor leads to well-dispersed VxOy species, which are involved in the adsorption of NH3 in the temperature T-a range of 300-673 K and for adsorption P-a < 0.5 IcPa. Sulfate and VxOy groups favor the amount of NH4+ species without modifying their heats of adsorption as compared to the TiO2, support: they are not detected for temperatures of interest for NH3-SCR reaction. In these experimental conditions and whatever the solids, two main adsorbed NH3 species on Lewis sites (denoted NH3ads.L1 and NH3ads.L2) are present, characterized by two delta(s) IR bands below 1300 cm(-1) and a common delta(as), IR band at approximate to 1600 cm(-1). By comparison with TiO2, P25; it is shown that sulfate groups have strong impacts neither on the proportion, x(1) and x(2),, of the two adsorbed species nor on their heats of adsorption (E-L1 (theta) and E-L2(theta) with theta the coverage of the NH3ads.L1 and NH3ads-L2 species: x(1) = 0.65, x(2) = 035, E-L1 (1) = 56 kJ/mol, E-L1(0) = 102 kJ/mol, E-L2(1) = 110 kJ/mol, E-L2(0) = 140 kJ/mol. The deposition of V-containing species on the sulfate-free and sulfated TiO2 surfaces leads to similar conclusions: in the experimental conditions (Ta and Pa) of the NH3-SCR, two adsorbed NH3 species on Lewis sites are detected with comparable proportions and heats of adsorption to those observed on the TiO2 supports

Experimental Microkinetic Approach of De-NOx by NH3 on V2O5/WO3/TiO2 Catalysts. 6. NH3-H2O Coadsorption on TiO2-Based Solids and Competitive Temkin Model

SSCI-VIDE+CARE:ECI2D:ING+FGI:JCO:CGE:NOG:SLO:DBIInternational audience--

Experimental Microkinetic Approach of De-NOx by NH3 on V2O5/WO3/TiO2 Catalysts. 5. Impacts of the NH3-H2O Coadsorption on the Coverage of Sulfated TiO2-Based Solids

SSCI-VIDE+CARE:ECI2D:ING+FGI:JCO:CGE:NOG:SLO:DBIInternational audience--

Experimental Microkinetic Approach of De-NOx by NH3 on V2O5/WO3/TiO2 Catalysts. 4. Individual Heats of Adsorption of Adsorbed H2O Species on Sulfate-Free and Sulfated TiO2 Supports

SSCI-VIDE+ECI2D:ING+FGI:JCO:CGE:NOG:EPU:DBIInternational audienceThe present study is a part of an experimental microkinetic approach of the removal of NOx from coal-fired power plants by reduction with NH3 on V2O5/WO3/TiO2 catalysts (NH3-selective catalytic reduction, NH3-SCR). It is dedicated to the characterization of the heats of adsorption of molecularly adsorbed H2Oads species formed on sulfate-free and sulfated TiO2 supports. Water, which is always present during the NH3-SCR, may be in competition and/or react (formation of NH4+) with the adsorbed NH3 species controlling the coverage of the adsorbed intermediate species of the reaction. Mainly, an original experimental procedure named adsorption equilibrium infrared spectroscopy (AEIR) previously used for the adsorption of NH3 species on the same solids is adapted for the adsorption of H2O. At T-a = 300 K and for P-H2O <= 1 kPa, three main H2Oads species are formed (associated with a minor amount of dissociated H2O species) on the two TiO2 solids. The species are identified by the positions of their IR bands in the 3750-3000 cm(-1) range. Considering the decreasing order of stability, they are (a) coordinated to strong (L-2) and weak (L-1) Lewis sites and denoted H2Oads-L2 and H2Oads-L1, respectively, and (b) hydrogen bonded to the H2Oads-L species and on O2-/OH sites of the solids (denoted H2Owads). The three species have a common well-defined delta H2O IR band at a position in the range 1640-1610 cm(-1) according to the total coverage of the surface. According to the AEIR method, the evolution of the intensity of this IR band during the increase in the adsorption temperature Ta in isobaric condition provides the evolution of the average coverage of the three species and then to their individual heats of adsorption as a function of their coverage. It is shown that there are no significant differences on the two TiO2 solids. In particular, the heat of adsorption of the H2Oads-L2 species varies from similar to 114 to 61 kJ/mol at low and high coverages respectively, indicating that it can be present in the experimental conditions of the NH3-SCR. In a forthcoming article, the competitive chemisorptions and reaction between adsorbed H2O and NH3 species are studied and modeled on the TiO2 supports and model and commercial V2O5/WO3/TiO2 catalysts