Multivariate analysis of ATR-IR spectroscopic data: applications to the solid-liquid catalytic interface

Area of Science:

• Surface Science
• Catalysis
• Spectroscopy

Background:

• Investigating solid catalyst-liquid interfaces is crucial for understanding heterogeneous catalysis.
• In situ methods are needed to observe dynamic processes at these interfaces.
• Supported catalysts like platinum on alumina are widely used in liquid-phase reactions.

Purpose of the Study:

• To demonstrate the effectiveness of attenuated total reflection infrared (ATR-IR) spectroscopy combined with multivariate data analysis for in situ studies of supported catalyst-liquid interfaces.
• To investigate the adsorption and dissociation of formaldehyde in water and acetonitrile in hexane on a Pt/gamma-Al(2)O(3) catalyst.
• To elucidate the surface species and reaction pathways occurring at the catalyst-liquid interface.

Main Methods:

• Utilized attenuated total reflection infrared (ATR-IR) spectroscopy.
• Employed multivariate data analysis techniques, including classical least squares (CLS) and partial least squares (PLS).
• Studied thin films of 5 wt % Pt/gamma-Al(2)O(3) on a germanium waveguide.
• Performed experiments involving formaldehyde adsorption/dissociation in water and acetonitrile adsorption in hexane.
• Incorporated isotope labeling for hydrogen adsorption studies.

Main Results:

• No adsorbed molecular formaldehyde was detected; carbon monoxide was observed as a dissociation product in an atop configuration on Pt.
• Spectroscopic evidence suggests adsorbed atomic hydrogen forms nu(Pt-H) stretching peaks at 1990 and 2060 cm(-1).
• Acetonitrile adsorbed on Pt via sigma-bonding of the CN group, forming tilted configurations reactive towards hydrogen, indicating a role in nitrile hydrogenation.

Conclusions:

• ATR-IR spectroscopy coupled with multivariate analysis is a powerful tool for in situ investigation of solid catalyst-liquid interfaces.
• The study provides detailed insights into the adsorption and reaction mechanisms of formaldehyde and acetonitrile on platinum catalysts.
• The findings highlight the potential of this approach for examining complex solid-catalyzed liquid-phase reactions.