Acidic properties of supported niobium oxide catalysts: An infrared spectroscopy investigation

Dátka, Jerzy; Turek, Andrzej M.; Jehng, Jih‐Mirn; Wachs, Israel E.

doi:10.1016/0021-9517(92)90279-q

Cited by 353 publications

(129 citation statements)

References 21 publications

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“…The data in Table 1 confirmed that strength of BAS is comparable for all the samples. The value of A 200 /A 150 nearly close to unity is characteristic of strong acid sites [30,31]. The relationship between the pressure drop and the flow rate is of practical significance, providing additional knowledge which is useful in assessing process economics.…”

Section: Introductionmentioning

confidence: 99%

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Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

et al. 2017

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Abstract:The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, differing in the size of mesopores, and in particular, flow-through macropores which significantly affected the flow characteristic of the continuous system. The highest ester productivity of 105.2 mol·mol H +−1 ·h −1 was achieved in microreactor M1 with the largest porosity, characterized by a total pore volume of 4 cm 3 ·g −1 , mesopores with 20 nm diameter, and large flow-through macropores 30-50 µm in size. The strong impact of the permeability of the monoliths on a reaction kinetics was shown.

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Section: Introductionmentioning

confidence: 99%

“…The data in Table 1 confirmed that strength of BAS is comparable for all the samples. The value of A200/A150 nearly close to unity is characteristic of strong acid sites [30,31]. The identification of acid sites and their strength were studied using pyridine (Py) adsorption combined with Fourier transform infrared (FTIR) studies.…”

Section: Introductionmentioning

confidence: 99%

Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

et al. 2017

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“…The as-produced materials were therefore analyzed on acidic properties using pyridine as probe molecule using integrated molecular absorption coefficients as established by Datka et al [41] Results are presented in Table 2. Expectedly, undoped WO 3 has the highest density of LAS, but also possesses a reasonable density of BAS.…”

Section: Resultsmentioning

confidence: 99%

Early Transition Metal Doped Tungstite as an Effective Catalyst for Glucose Upgrading to 5-Hydroxymethylfurfural

2018

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Glucose valorization to 5-hydroxymethylfurfural (HMF) remains challenging in the transition towards renewable chemistry. Lewis acidic tungstite is a viable, moderately active catalyst for glucose dehydration to HMF. Literature reports a multistep mechanism involving Lewis acid catalyzed isomerization to fructose, which is then dehydrated to HMF by Brønsted acid sites. Doping tungstite with titanium and niobium improves activity by optimizing the ratio between Lewis and Brønsted acid sites. Graphical AbstractKeywords Biomass · Glucose · 5-Hydroxymethylfurfural · Tungsten oxide · Doping

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“…After that, the sample was dosed with excess pyridine vapor, followed by high vacuum evacuation for 40 min. Literature values were used for the integrated molar extinction coefficients for quantitative determination of the Brønsted acid and Lewis acid site contents [40]. The X-ray photoelectron spectroscopy (XPS) measurements were carried out on a Thermo Scientific K-Alpha spectrometer, equipped with a monochromatic small-spot X-ray source and a 180°double-focusing hemispherical analyzer with a 128-channel detector.…”

Section: Characterizationmentioning

confidence: 99%

Silica deposition as an approach for improving the hydrothermal stability of an alumina support during glycerol aqueous phase reforming

Liu

Okolie

Ravenelle

et al. 2018

Applied Catalysis A: General

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A B S T R A C TSilica deposition on the benchmark aqueous phase reforming (APR) catalyst Pt/γ-Al 2 O 3 is studied to prevent or limit hydrolytic attack of the support under hydrothermal APR conditions, for which boehmite formation by support hydration is a known cause for catalyst deactivation. Tetraethyl orthosilicate (TEOS) is employed as a silicon source in a straightforward liquid-phase, silylation process followed by catalyst calcination and reduction. Characterization by X-ray diffraction, temperature-programmed desorption of NH 3 , infrared, 27 Al nuclear magnetic resonance and X-ray photoelectron spectroscopy of the fresh catalysts suggests that silica addition occurs preferentially on the support surface, resulting in weak Brønsted acid sites as well as in the formation of Si-O-Al linkages at the expense of specific surface Lewis acid sites. Silylation and calcination of Pt/γ-Al 2 O 3 causes partial blockage of the metal surface area (12% loss), whereas γ-Al 2 O 3 surface silica modification prior to Pt deposition makes controlled metal deposition difficult. Catalytic performance tests show the overcoated samples to be active in the APR of 5 wt% glycerol, albeit with lower H 2 production rates compared to the benchmark catalyst. Characterization of spent APR catalysts clearly demonstrates that silylation/calcination treatments effectively slows down the transformation of the γ-Al 2 O 3 support due to the formation of a Si-O-Al interface. Overall, the lifetime of the catalyst is increased three-fold as a result of the surface overcoating treatment, with repetitive recycling ultimately leading to loss of the protective silica layer.

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Acidic properties of supported niobium oxide catalysts: An infrared spectroscopy investigation

Cited by 353 publications

References 21 publications

Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

Early Transition Metal Doped Tungstite as an Effective Catalyst for Glucose Upgrading to 5-Hydroxymethylfurfural

Silica deposition as an approach for improving the hydrothermal stability of an alumina support during glycerol aqueous phase reforming

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