Polymerization and decarbonylation reactions of aldehydes on the Pd(111) surface

Journal Article · Wed Mar 01 00:00:00 EST 1989 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00187a035· OSTI ID:5637885

Davis, J L; Barteau, M A

The adsorption and reaction of formaldehyde, acetaldehyde, and propanal were compared in temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) studies on a clean Pd(111) surface. Formaldehyde reacted upon adsorption at 170 K via decomposition to CO(a) and H(a) and polymerization to paraformaldehyde. In contrast, decomposition of the higher aldehydes required significantly higher temperatures. Acetaldehyde adsorbed on the clean surface in an /eta//sup 2/ configuration and reacted to form stable acetyl species (CH/sub 3/C/double bond/O), which decomposed above 300 K to produce CO(a), H(a), and C/sub 1/ hydrocarbon fragments. Adsorbed acetyl groups were readily identified by the characteristic frequency of their CO stretch at 1565 cm/sup /minus/1/. In competition with decarbonylation, desorption of acetaldehyde occurred at 220 and 325 K. The CO stretch of /eta//sup 2/-acetaldehyde was observed at 1390 cm/sup /minus/1/. Similarly, the adlayer produced by the adsorption of propanal on Pd(111) was a mixture of /eta//sup 2/-propanal and propanoyl species (CH/sub 3/CH/sub 2/C/double bond/O) produced by removal of the aldehyde hydrogen atom. No evidence was found for polymerization of either acetaldehyde or propanal on the clean Pd(111) surface. A kinetic isotope effect was observed in the decomposition of adsorbed acetyl intermediates, suggesting that C-H cleavage is rate determining for this reaction. These results illustrate the pathways, intermediates, and energetics of aldehyde decarbonylation reactions on group VIII metal surfaces and may provide insights into the mechanism of oxygenate synthesis from CO and H/sub 2/.

• Research Organization: Univ. of Delaware, Newark (USA)
• DOE Contract Number: FG02-84ER13290
• OSTI ID: 5637885
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 111:5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALDEHYDES
ADSORPTION
POLYMERIZATION
PLATINUM
SORPTIVE PROPERTIES
CARBONYLS
CATALYSTS
DESORPTION
ENERGY-LOSS SPECTROSCOPY
EXPERIMENTAL DATA
ISOTOPE EFFECTS
LAYERS
OXYGEN
REACTION INTERMEDIATES
RESOLUTION
SURFACE PROPERTIES
SURFACES
TEMPERATURE DEPENDENCE
CHEMICAL REACTIONS
DATA
ELECTRON SPECTROSCOPY
ELEMENTS
INFORMATION
METALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
PLATINUM METALS
SORPTION
SPECTROSCOPY
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties