In order to determine the amount of coke deposited on the catalyst, temperature-programmed oxidation (TPO) was performed on the used catalyst in a Stanton-Redcroft thermogravimetric analyser (TGA and DTG). Around 10 mg of the catalyst recovered after the reaction were heated in an atmosphere of air at 15 C min 1 to a final temperature of 800 C, with a dwell time of 10 min.