An investigation into the activation of methane using a tuneable femtosecond laser system

Abstract

Using a tuneable femtosecond- and nanosecond laser system at room temperature, it was observed that by photo-irradiation in the infrared region, methane can be photo-excited to undergo the coupling reaction in which ethane and hydrogen is formed. In similar conditions, the addition of carbon dioxide results in the formation of carbon monoxide through the photoreduction of carbon dioxide by methane. Molecular modelling calculations were used to determine the photoabsorption wavelength needed for C-H bond activation of methane. Calculations showed that the 2v3 overtone at 1.67 pxn was ideal for excitation. Fourier transform infrared spectroscopy was used to analyze the samples after excitation. These results suggested that partial dehydrogenation of ethane to ethylene also occurred during the coupling reaction of methane while traces of methanol were found in the CH4/CO2 mixture after excitation. Although pleasing results were obtained with the nanosecond laser system, the femtosecond laser system proved more reliable and efficient.