Study of the poisoning of γ‐Al<sub>2</sub>O<sub>3</sub> by alkali metals addition

Cortez, G. G.; Miguel, Sergio R. de; Scelza, Osvaldo A.; Castro, Alberto A.

doi:10.1002/jctb.280530212

Cited by 19 publications

(10 citation statements)

References 13 publications

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“…When the sodium content exceeds 1.0%, almost no NH 3 desorption at higher temperature appears. This result clearly indicates that sodium can neutralize the strong acidic sites of the catalysts effectively, which is consistent with the results of prior research [29,30].…”

Section: Catalysts Characterizationsupporting

confidence: 81%

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

et al. 2010

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The effect of Na addition to PtSn/AlSBA-15 on the catalytic properties in propane dehydrogenation was studied. The catalysts were characterized by XRF, BET, HR-TEM, NH 3 -TPD, TPO and TPR. Results showed that the presence of sodium could not only modify the acid function of the catalysts but also the structure of metallic phase, thus reduce the amount of coke deposition. Among the catalysts investigated, PtSnNa (1.0%)/AlSBA-15 had the best catalytic performance in terms of propane conversion and stability. The high catalytic performance may be owing to the strong interaction between metal and support.

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Section: Catalysts Characterizationsupporting

confidence: 81%

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

et al. 2010

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“…Moreover, the selectivity to di-isopropylether displays an analogous behaviour since it decreases with the increase of the Na content, such as also shows. Taking into account that the ether formation would require strong acid sites [7], the results obtained in the isopropanol dehydration would be in agreement with the higher poisoning capacity of Na on the stronger acid sites of the alumina. Fig.…”

Section: Characterization Of the Acid And Metallic Phasesupporting

confidence: 72%

“…Jiratová reported a selective poisoning of the support when alumina is doped with Na ions. García Cortéz et al [7], by using ammonia thermodesorption, found that Li, Na and K ions poison the acid sites of alumina. Moreover, these authors reported that the strong acid sites are poisoned by the addition of small quantities of alkali metal ions.…”

Section: Introductionmentioning

confidence: 98%

Characteristics of the metallic phase of Pt/Al2O3 and Na-doped Pt/Al2O3 catalysts for light paraffins dehydrogenation

Castro

Guerrero-Ruı́z

Scelza

et al. 2006

Chemical Engineering Journal

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“…5 In this case, water in the form of H 2 O -and ОН -can be removed from the same active sites that are present in the starting samples, which explains the TSE curves similar in shape (see Fig. 3) recorded upon isopropyl alcohol decomposition in the adsorption layer.…”

Section: Resultsmentioning

confidence: 90%

“…ESR spectra of anthraquinone adsorbed on the surface of the γ Al 2 O 3 and Li + /Al 2 O 3 samples(1)(2)(3)(4)(5). The spectra were recorded at 20 °С.…”

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confidence: 99%

Donor-acceptor properties, catalytic activity, and negative charge exoemission from the alumina surface modified with lithium cations

et al. 2006

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Donor acceptor properties of alumina modified with lithium cations were studied by ESR of paramagnetic complexes of adsorbed anthraquinone. The results were compared with the data on negative ion emission (exoemission) accompanying the decomposition of isopropyl alcohol in the adsorption layer. The data on the activity measured by the pulse microcatalytic technique in isopropyl alcohol decomposition are discussed. Small additives of lithium were found to promote catalytic activity of the samples. The role of acid and basic sites in isopropyl alcohol decomposition was discussed.Alkaline metals often exist as admixtures in Al 2 O 3 based catalysts and exert a substantial effect on the acid base properties of the surface and, hence, on the selectiv ity of catalytic processes. Alumina modified with lithium cations is being studied as both a catalyst by itself 1,2 and a support for the nickel and manganese supported cata lysts. 3,4 Modification is usually carried out by the impreg nation method, and either hydroxide 2,5 or a thermally unstable salt (nitrate 3 or acetate 6 ) is applied as a lithium compound. In the present work, the ESR and exoemission (EE) methods are used to study the acid base properties of the Li + /Al 2 O 3 catalyst surface. ESR spectroscopy of paramagnetic complexes of adsorbed anthraquinone pro vides detailed information on the structure and concen tration of electron acceptor sites. 7 The method of low temperature (-269-420 °С) EE of negative charges gives data on the content of electron donor sites. 8 In the present work, we studied how a modifying lithium additive can influence the activity of the Li + /Al 2 O 3 catalysts in the decomposition of isopropyl alcohol and change their donor acceptor properties. ExperimentalCatalysts were prepared by the impregnation of γ Al 2 O 3 with an aqueous solution of lithium nitrate followed by drying and calcination in air at 450 °С for 4 h and then at 600 °С for 4 h. The catalysts with a content of 0.4-4 mmoles of Li + (g of Al 2 O 3 ) -1 were obtained in this way (Table 1). The surface coverage was estimated under the assumption that each Li + ion occupies the ion area equal to (2r) 2 , where r = 0.068 nm (see Ref. 9). Then the monolayer corresponds to a coverage of 5.41•10 19 Li + m -2 or 89.8 mmol m -2 .The phase composition was determined by X ray diffraction analysis on a DRON 3M diffractometer using Cu Kα radiation.The specific surface was measured on a GKh 1 gasometer using the chromatographic method. At first, low temperature adsorption (-196 °С) of nitrogen was carried out (using an N 2 -He mixture containing 6 mol.% N 2 ), then nitrogen was desorbed at room temperature, and the surface area was deter mined from the area of the desorption peak.Prior to anthraquinone adsorption, the samples were sub jected to thermovacuum treatment at 470 °С in air for 2 h and in vacuo (10 -5

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Study of the poisoning of γ‐Al₂O₃ by alkali metals addition

Cited by 19 publications

References 13 publications

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

Characteristics of the metallic phase of Pt/Al2O3 and Na-doped Pt/Al2O3 catalysts for light paraffins dehydrogenation

Donor-acceptor properties, catalytic activity, and negative charge exoemission from the alumina surface modified with lithium cations

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Study of the poisoning of γ‐Al2O3 by alkali metals addition

Cited by 19 publications

References 13 publications

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

Effect of Sodium Addition to PtSn/AlSBA-15 on the Catalytic Properties in Propane Dehydrogenation

Characteristics of the metallic phase of Pt/Al2O3 and Na-doped Pt/Al2O3 catalysts for light paraffins dehydrogenation

Donor-acceptor properties, catalytic activity, and negative charge exoemission from the alumina surface modified with lithium cations

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Study of the poisoning of γ‐Al₂O₃ by alkali metals addition