Synthesis and comparative evaluation of HZSM-5 and NaZSM-5 zeolites in the catalytic dehydration of glycerol

Abstract Glycerol is one of the main byproducts of the transesterification reaction involved in biodiesel production. Due to its low added value, several efforts have been made to make it more economically valuable, including catalytic processes to convert it into products of higher economic benefit, such as acrolein and allyl alcohol. This research work presents the synthesis of two zeolites with different superficial acid strengths, HZSM-5 and NaZSM-5. The catalytic performance of both materials was evaluated in the dehydration of glycerol reaction. X-ray diffraction, N2 physisorption, thermogravimetry and Fourier transform infrared spectroscopy were applied to characterize the structural and superficial properties. Temperature-programmed desorption of NH3 indicated a predominance of weak acid sites in NaZSM-5 and intermediate and strong ones in HZSM-5. This different acidity properties results in superior catalytic performance of HZSM-5, however both catalysts showed activity in the glycerol dehydration reaction. HZSM-5 catalyst has greater catalytic stability and less deactivation during the reaction. The product distribution showed a majority production of acrolein when HZSM-5 was the catalyst and an accentuated decrease in selectivity in the presence of NaZSM-5.