Impregnation EXAFS study

Denecke MA, Reich T, Pompe S, Bubner M, Heise KH, Nitsche H, Allen PG Bucher JJ, Edelstein NM, Shuh DK, Czerwinski KR (1998b) EXAFS investigations of the interaction of humic acids and model compounds with uranyl cations in sohd complexes. Radiochim Acta 82 103-108 Dent AJ, Ramsay JDF, Swanton SW (1992) An EXAFS study of uranyl ions in solutions and sorbed onto sihca and montmorillonite clay colloids. J Colloid Interface Sci 150 45-60 d Espinose de la Caillerie J-B, Kermarec M, Clause (1995a) Impregnation of y-alumina with ( ) and ( ) ions at neutral pH Hydrotalcite-type coprecipitate formation and characterization J Am Chem Soc 117 11471-11481... 

EXAFS study of the alumina/metal ion interactions durii impregnation at neutral pH... 

Stable rhenium tricarbonyls bonded to the surface of MgO have been prepared and characterized by EXAFS. Heating under He, O2 or vacuum of a sample obtained by impregnation of Re2(CO)io produced the oxidative fragmentation of the initial surface organometallic species [39-41]. These types of supported well-characterized species can be used as models in the study of reaction mechanisms [42]. 

Munoz-Paez and Koningsberger use a combination of TPR, MS and EXAFS to study the decomposition of [Pt (NH3)4](OH )2 impregnated on y-Al203. They report the decomposition of the precursor to Pt(NH3)20 during drying in He at 120°C and a partial reduction of the precursor to metallic Pt when reduced at 180 and 200°C. 

In this study, a powerful combination of high resolution transmission electron microscopy (HRTEM), mass spectrometry (MS) and Quick EXAFS (QEXAFS) is used to study the reactions of [Pt2+(NH3)4](N03 )2 impregnated on Si02 during different pretreatment processes. MS is used to monitor which gases are produced during the pretreatment. QEXAFS is used to study the local structure of the Pt complex during the pretreatment. The timescale of... 

Three different pretreatments were performed and studied by both Quick EXAFS and MS. During each pretreatment the impregnated support was heated in one gas with a ramp of 2°C/min from room temperature to 400°C. The gases used were 1) either He (QEXAFS) or Ar (MS) (this sample is called Pt[Ar/He] ), 2) 02 ( Pt[02] ) and 3) H2( Pt[H2] ). 

This study is aimed at using and identifying Al- and Co-containing Anderson-type heteropolyanions in the synthesis of (Co)Mo/alumina and (Co)Mo/zeolite HDS catalysts oxidic precursors. Various techniques such as Raman spectroscopy, NMR and EXAFS are used to show the apparition of the AlMo6024H6 entity upon impregnation of an alumina or a zeolite with an ammonium heptamolybdate solution. The question of the Mo-Co interaction in the promoted precursors is also tackled through the use of the CoMo6024H6 entity. 

The surface of the si orted VPO systems were studied by SEM with MPA (Jcol JSM-35 SF and Ortek EEDS-II) and XPS (VG ESCA-3, A1 Kap. standard C Is B E. = 284.8 eV) in much the same manner as it was described in [10]. Study of the samples by EXAFS was carried out analogously to that published in [11]. Sortie of the catidysts, namely impregnated ones, were analysed by XRD method (DRON-3M). 

The selective reduction of NO by hydrocarbon in an excess of oxygen was studied using a platinum catalyst doped or not with zinc. Successive impregnetion or co-impregnation of Pt and Zn on alumina were made. In some cases, in the presence of Zn, the NO conversion is increased in parallel with N2 formation. A better conversion of hydrocarbons was also observed. EXAFS experiments and N2O decomposition experiments have been carried out to explain these observations. 

It has been shown through a Raman, and Mo K-edge EXAFS spectroscopic study, that upon impregnation of alumina with AHM solution a decomposition occurs with extraction of aluminium atoms of the support... 

In this work the formation of nickel, cobalt or zinc aluminum hydrotalcite-type coprecipitates upon impregnation of y-alumina at near neutral pH and ambient temperature was confirmed by EXAFS and X-ray dif action. The role of the metal ion concentration in solution on the composition of the supported coprecipitate was studied as well as the influence of the specific surface area of the Y-alumina. The deposition of Co(II), Ni(II) and Zn(II) ions onto a commercial almnina was first investigated. Since the coprecipitation mechanism is likely to be affected both by the impurity level and the thermal pretreatment of the carriers before impregnation, supports of high purity were prepared by hydrolysis of aluminum alkoxides and were submitted to identical pretratments immediately before impregnation. The deposition of Ni(ll) onto these supports was then examined. 

Introduction of cobalt and nickel into zeolites by solid-state ion exchange was investigated by Jentys and colleagues and compared with preparations via conventional exchange in aqueous solution, impregnation and direct synthesis ([164-170], vide infra). For their studies, the authors employed TPD of NH3 (TPDA), IR spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS) and XRD. TPDA revealed that 100% of the strong Bronsted acid sites were eliminated at an nco/nAi ratio of ca. 1.0 and 0.5 in the case of SSIE of C0CI2 in mixtures with H-ZSM-5 and NH4-Y, respectively. Therefore, the authors concluded... 

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