Temperature-programmed desorption of water and ammonia on sulphated zirconia catalysts for measuring their strong acidity and acidity distribution

Choudhary, Vasant R.; Karkamkar, Abhijeet J.

doi:10.1007/bf02704219

Cited by 16 publications

(4 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CZ‐supported metal oxides catalysts are generally free of Brønsted acid sites [35] . As the sample activation was carried out at 500 °C, insignificant signals above 500 °C were likely from dehydration of the sample and hence were not included for total NH 3 uptake calculations [36] …”

Section: Resultsmentioning

confidence: 99%

“…[35] As the sample activation was carried out at 500°C, insignificant signals above 500°C were likely from dehydration of the sample and hence were not included for total NH 3 uptake calculations. [36] The CZ support contained some Lewis acid sites (LAS) as indicated by the release of the adsorbed NH 3 . The addition of 2-3 wt% of metal oxide clusters to the CZ support increased the LAS concentration by 80-220 % as indicated by the greater NH 3 uptake (Table 1).…”

Section: Temperature Programmed Desorption Of Ammonia (Nh 3 -Tpd)mentioning

confidence: 99%

See 1 more Smart Citation

Selective Oxidation of Methane to Methanol over Ceria‐Zirconia Supported Mono and Bimetallic Transition Metal Oxide Catalysts

Lyu

Jocz

et al. 2021

ChemCatChem

View full text Add to dashboard Cite

Several ceria‐zirconia supported mono and bi‐metallic transition metal oxide clusters containing Fe, Cu, and Ni are synthesized by dry impregnation. Through XRD, H2‐TPR, NH3‐TPD, pyridine adsorption followed by FTIR spectroscopy and XAS, the well‐dispersed nature of the transition metal oxide clusters is revealed, and the Lewis acidity of the catalysts is assessed. In‐situ FTIR spectroscopy is used to monitor the methane activation on catalyst surfaces. All catalysts activate methane at 250 °C forming methyl, alkyl, and methoxy species on the catalyst surface. By co‐feeding steam and oxygen together with methane, continuous direct oxidation of methane to methanol can be achieved, with the complete oxidation to CO2 as the other reaction path. Methoxy species are found to be a key intermediate for methanol production. Lowering the methane conversion improves the methanol selectivity. By extrapolation, it is estimated that methanol selectivity close to unity can be achieved below a threshold of methane conversion at about 0.002 %. The formation of CuO and NiO mixed metal oxides produces stronger Lewis acid sites and yields higher methanol selectivity.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Temperature Programmed Desorption Of Ammonia (Nh 3 -Tpd)mentioning

confidence: 99%

Selective Oxidation of Methane to Methanol over Ceria‐Zirconia Supported Mono and Bimetallic Transition Metal Oxide Catalysts

Lyu

Jocz

et al. 2021

ChemCatChem

View full text Add to dashboard Cite

show abstract

“…We determine the strength of water adsorption in six porous oxides (extruded pellets) used as supports and catalysts: TiO 2 ‐a (anatase), TiO 2 ‐r (rutile) (supplied by Evonik‐Degussa), ZrO 2 , γ‐Al 2 O 3 , θ‐Al 2 O 3 and SiO 2 . We chose water as the adsorbate because it is central to aqueous‐phase heterogeneous catalytic processes and, in the context of this work, has the additional advantages of not decomposing during thermally driven desorption 45…”

Section: Methodsmentioning

confidence: 99%

“…We chose water as the adsorbate because it is central to aqueousphase heterogeneous catalytic processes and, in the context of this work, has the additional advantages of not decomposing during thermally driven desorption. [45] The TPD energy distributions for water desorbing from the porous oxides are shown in Figure 2. Due to the uncertainty associated with the tail of the TPD curves, we determine the maximum activation energy of desorption (E max ) where the integral area of the desorption curves is 95 % of the total, see Figure 2.…”

Section: Tpd Experimentsmentioning

confidence: 99%

Interpretation of NMR Relaxation as a Tool for Characterising the Adsorption Strength of Liquids inside Porous Materials

D’Agostino

Mitchell

Mantle

et al. 2014

Chemistry A European J

109

142

View full text Add to dashboard Cite

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate–adsorbent interactions in liquid-saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T1/T2) is related to an adsorbate–adsorbent interaction energy, and we introduce a quantitative metric esurf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO2 anatase, TiO2 rutile, γ-Al2O3, SiO2, θ-Al2O3 and ZrO2) and show that esurf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the esurf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T1/T2 measurements may become a useful addition to the methods available to characterise liquid-phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate–surface interactions in liquid-phase catalysis.

show abstract

Ba/ZrO2 nanoparticles as efficient heterogeneous base catalyst for the synthesis of β-nitro alcohols and 2-amino 2-chromenes

2016

View full text Add to dashboard Cite

Zirconia nanoparticles were synthesized by precipitation, urea hydrolysis, amorphous citrate and combustion synthesis methods. The zirconia surface was subsequently modified by grafting Ba 2+ species. The Ba 2+ modified zirconia (Ba/ZrO 2) materials were characterized using XRD, Fourier analysis, UV-vis-DRS, FESEM and HRTEM techniques. XRD study indicated selective stabilization of the tetragonal phase of zirconia in the presence of Ba 2+ species. Fourier line profile analysis of the XRD peaks revealed that the average crystallite size of the zirconia nanoparticles is in the range of 5-15 nm. The surface area, basicity and barium content of the material depend strongly on the method of synthesis. The Ba/ZrO 2 catalyst prepared by urea hydrolysis method exhibited higher surface area and barium content compared to other samples. The catalytic activity of the Ba/ZrO 2 catalyst was evaluated for synthesis of β-nitro alcohols and 2-amino 2-chromenes. The β-nitro alcohols were synthesized by condensation of aryl aldehydes and nitromethane. Similarly, the 2-amino 2-chromenes were synthesized by condensation of arylaldehydes, α-naphthol and malononitrile. The Ba/ZrO 2 catalyst was found to be highly efficient for synthesis of both classes of compounds providing excellent yield and purity of the products.

show abstract

Temperature-programmed desorption of water and ammonia on sulphated zirconia catalysts for measuring their strong acidity and acidity distribution

Cited by 16 publications

References 13 publications

Selective Oxidation of Methane to Methanol over Ceria‐Zirconia Supported Mono and Bimetallic Transition Metal Oxide Catalysts

Selective Oxidation of Methane to Methanol over Ceria‐Zirconia Supported Mono and Bimetallic Transition Metal Oxide Catalysts

Interpretation of NMR Relaxation as a Tool for Characterising the Adsorption Strength of Liquids inside Porous Materials

Ba/ZrO2 nanoparticles as efficient heterogeneous base catalyst for the synthesis of β-nitro alcohols and 2-amino 2-chromenes

Contact Info

Product

Resources

About