INVESTIGADORES
BONIVARDI Adrian Lionel
artículos
Título:
Infrared Study of the Absorption of Formic Acid on Clean and Ca-promoted Pd/SiO2 Catalysts
Autor/es:
GRISELDA C. CABILLA; ADRIAN L. BONIVARDI; MIGUEL A. BALTANÁS
Revista:
APPLIED CATALYSIS A-GENERAL
Referencias:
Año: 2003 vol. 255 p. 181 - 195
ISSN:
0926-860X
Resumen:
The adsorption and decomposition of formic acid on a highly dispersed supported Pd/SiO2 catalyst (2 wt.% Pd) prepared
via ion exchange (IE) of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca/Pd = 2 at./at.)
where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by
FTIR at 298653 K.
On the support, HCOOH is mostly adsorbed molecularly at room temperature, with partial dimerization, condensation
and extensive hydrogen bonding, but readily decomposes, on the Pd crystallites of Pd/SiO2, via decarbonylation, to give CO
multicoordinated to the metal surface, and water. With heating, formic acid decomposition is accompanied by some water
gas shift as well, while CO reacts to give methyl (methane) and methoxy.
Calcium promotion to both the prereduced Pd and its diammine complex precursor, enhanced HCOOH decomposition onto
the catalyst surface, even at 298 K. Together with sorbed HCOOH and chemisorbed CO, mono- and bidentate formates were
observed on these materials, owing to the incorporation of well-dispersed CaOxHy. These formates were readily decomposed
by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates
(polydentate and simple) were formed, but hardly anymethanewas detected.On CaPd/SiO2 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO22 catalyst (2 wt.% Pd) prepared
via ion exchange (IE) of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca/Pd = 2 at./at.)
where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by
FTIR at 298653 K.
On the support, HCOOH is mostly adsorbed molecularly at room temperature, with partial dimerization, condensation
and extensive hydrogen bonding, but readily decomposes, on the Pd crystallites of Pd/SiO2, via decarbonylation, to give CO
multicoordinated to the metal surface, and water. With heating, formic acid decomposition is accompanied by some water
gas shift as well, while CO reacts to give methyl (methane) and methoxy.
Calcium promotion to both the prereduced Pd and its diammine complex precursor, enhanced HCOOH decomposition onto
the catalyst surface, even at 298 K. Together with sorbed HCOOH and chemisorbed CO, mono- and bidentate formates were
observed on these materials, owing to the incorporation of well-dispersed CaOxHy. These formates were readily decomposed
by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates
(polydentate and simple) were formed, but hardly anymethanewas detected.On CaPd/SiO2 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO23)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca/Pd = 2 at./at.)
where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by
FTIR at 298653 K.
On the support, HCOOH is mostly adsorbed molecularly at room temperature, with partial dimerization, condensation
and extensive hydrogen bonding, but readily decomposes, on the Pd crystallites of Pd/SiO2, via decarbonylation, to give CO
multicoordinated to the metal surface, and water. With heating, formic acid decomposition is accompanied by some water
gas shift as well, while CO reacts to give methyl (methane) and methoxy.
Calcium promotion to both the prereduced Pd and its diammine complex precursor, enhanced HCOOH decomposition onto
the catalyst surface, even at 298 K. Together with sorbed HCOOH and chemisorbed CO, mono- and bidentate formates were
observed on these materials, owing to the incorporation of well-dispersed CaOxHy. These formates were readily decomposed
by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates
(polydentate and simple) were formed, but hardly anymethanewas detected.On CaPd/SiO2 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO22, via decarbonylation, to give CO
multicoordinated to the metal surface, and water. With heating, formic acid decomposition is accompanied by some water
gas shift as well, while CO reacts to give methyl (methane) and methoxy.
Calcium promotion to both the prereduced Pd and its diammine complex precursor, enhanced HCOOH decomposition onto
the catalyst surface, even at 298 K. Together with sorbed HCOOH and chemisorbed CO, mono- and bidentate formates were
observed on these materials, owing to the incorporation of well-dispersed CaOxHy. These formates were readily decomposed
by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates
(polydentate and simple) were formed, but hardly anymethanewas detected.On CaPd/SiO2 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO2xHy. These formates were readily decomposed
by atomic hydrogen produced by decarbonylation/WGS of formic acid on Pd. At increasing temperatures, some carbonates
(polydentate and simple) were formed, but hardly anymethanewas detected.On CaPd/SiO2 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO22 with calcium added to prereduced
Pd metal particles the extension and/or onset of all these processeswasmore straightforward than on the promoted CaPd/SiO22
where calcium was added to diammine palladium instead, most likely owing to the combined impact of a higher dispersion
of the Pd crystallites on the former preparation, and calcium oxyhydroxide decoration (CaOxHy) of the metal particles on the
latter, which hamper H-spillover from them.xHy) of the metal particles on the
latter, which hamper H-spillover from them.