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Gold nanoparticles supported on magnesium oxide for CO oxidation.

Carabineiro SA, Bogdanchikova N, Pestryakov A, Tavares PB, Fernandes LS, Figueiredo JL - Nanoscale Res Lett (2011)

Bottom Line: Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.CO oxidation was used as a test reaction to compare the catalytic activity.This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Catálise e Materiais, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal. scarabin@fe.up.pt.

ABSTRACT
Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

No MeSH data available.


H2-TPR profiles of the commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM.
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Figure 4: H2-TPR profiles of the commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM.

Mentions: TPR results are shown in Figure 4 for the pure MgO and MgO loaded with gold by DIM. It can be seen that pure MgO does not show any significant reduction peak in the studied range of temperatures (thin line), as expected from the literature [16,45]. When Au is loaded into MgO, as discussed above, the support is transformed into Mg(OH)2, most likely by reaction with water. As can be seen in Figure 4 (thick line), a large negative peak is observed on the TPR spectrum between approximately 300 and approximately 600°C. This means that hydrogen is not being consumed. However, water release was detected by mass spectrometry, most likely meaning that MgO is being formed (Mg(OH)2 → MgO + H2O). In fact, a second TPR run produced a spectrum with no peaks, as for the oxide, as expected from the literature [16,45]. Similar results were obtained for samples loaded by the other methods.


Gold nanoparticles supported on magnesium oxide for CO oxidation.

Carabineiro SA, Bogdanchikova N, Pestryakov A, Tavares PB, Fernandes LS, Figueiredo JL - Nanoscale Res Lett (2011)

H2-TPR profiles of the commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211853&req=5

Figure 4: H2-TPR profiles of the commercial MgO, pure (thin line) and loaded with 1% Au wt (thicker line) by DIM.
Mentions: TPR results are shown in Figure 4 for the pure MgO and MgO loaded with gold by DIM. It can be seen that pure MgO does not show any significant reduction peak in the studied range of temperatures (thin line), as expected from the literature [16,45]. When Au is loaded into MgO, as discussed above, the support is transformed into Mg(OH)2, most likely by reaction with water. As can be seen in Figure 4 (thick line), a large negative peak is observed on the TPR spectrum between approximately 300 and approximately 600°C. This means that hydrogen is not being consumed. However, water release was detected by mass spectrometry, most likely meaning that MgO is being formed (Mg(OH)2 → MgO + H2O). In fact, a second TPR run produced a spectrum with no peaks, as for the oxide, as expected from the literature [16,45]. Similar results were obtained for samples loaded by the other methods.

Bottom Line: Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.CO oxidation was used as a test reaction to compare the catalytic activity.This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratório de Catálise e Materiais, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal. scarabin@fe.up.pt.

ABSTRACT
Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

No MeSH data available.