A temperature programmed desorption study of the interaction of ethyl cyanoacetate and benzaldehyde on metal oxide surfaces

• Benzaldehyde and ethyl cyanoacetate decompose upon desorption from ZnO and γ-Al2O3.
• Ethyl cyanoacetate forms ethyl formate and ketenimine on the surface of ZnO.
• Benzaldehyde decomposes to form Benzene, CO and CO2.
• The surface species identified play an important role in Knoevenagel condensation.

Reagents from a base catalysed condensation reaction (Knoevenagel condensation reaction between ethyl cyanoacetate and benzaldehyde), were adsorbed on ZnO and Al2O3 catalyst surfaces and subject to temperature programmed desorption experiments, monitored using mass spectrometry. Ethyl formate, ketenimine species, carbon dioxide and carbon monoxide were desorption products from ethyl cyanoacetate, while benzene, carbon dioxide and carbon monoxide were desorbed from the catalysts loaded with benzaldehyde. The formation of the ketenimine species was confirmed by in situ FTIR experiments. The observation of the decomposition species further substantiates a proposed reaction mechanism for the Knoevenagel condensation reaction on the catalyst surface of some oxide catalysts.

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