Catalytic Deactivation of HY Zeolites in the Dehydration of Glycerol to Acrolein

Israel Pala-Rosas,Beatriz Zeifert,Sofía Hernández-Ramírez,Juan Navarrete-Bolaños,José L Contreras,José Salmones,Jennipher Pérez-Cabrera,Andrés A Fragoso-Montes De Oca,Ricardo López-Medina

doi:10.3390/catal11030360

Abstract

The study of the deactivation of HY zeolites in the dehydration reaction of glycerol to acrolein has represented a challenge for the design of new catalysts. HY zeolites with SiO2/Al2O3 molar ratios between 3.5 and 80 were studied. The solids were characterized by XRD, N2 physisorption, SEM-EDXS, Raman and UV-vis spectroscopies, infrared spectroscopy of pyridine (FTIR-Py) and catalytic activity tests from 250 °C to 325 °C. It was found that the total amount of acid sites per unit area of catalyst decreased as the SiO2/Al2O3 molar ratio increased from 3.5 to 80, resulting in the decrease in the initial glycerol conversion. The initial acrolein selectivity was promoted with the increase of the Brønsted/Lewis acid sites ratio at any reaction temperature. The deactivation tests showed that the catalyst lifetime depended on the pore structure, improving with the presence of large surface areas as evidenced by the deactivation rate constants. The characterization of the deactivated catalysts by XRD, N2 physisorption and thermogravimetric analysis indicated that the deposition of coke resulted in the total obstruction of micropores and the partial blockage of mesopores. Moreover, the presence of large mesopores and surface areas allowed the amount of coke deposited at the catalyst surface to be reduced.

Highlights

The production of biodiesel for its use as fuel in diesel engines has gained importance during recent decades, leading to the rapid growth of the biodiesel industry
The HY zeolites with different SiO2/Al2O3 molar ratios were active as catalysts in the conversion of glycerol to acrolein, improving with the increase in temperature, as well as with the total number of acid sites
Acrolein was the main reaction product, and its selectivity was enhanced with the temperature increment, with the exception of the HY(3.5), which promoted the production of acetaldehyde

Summary

Introduction

The production of biodiesel for its use as fuel in diesel engines has gained importance during recent decades, leading to the rapid growth of the biodiesel industry. According to the Organization for Economic Cooperation and Development (OECD) and the Food and Agriculture Organization of the United Nations (FAO), it is expected that glycerol production from the biodiesel industry will reach and remain around 4.4 billion liters per year between 2020 and 2028 [4]. In this context, the valorization of glycerol by means of catalytic reactions has been investigated in recent years in order to change the current status of glycerol as a byproduct into raw material for the synthesis of value-added compounds [1,2,5,6,7]. The catalytic dehydration of glycerol has become important since it may yield acrolein as the main reaction product, representing a route for its renewable production in comparison with the current process based on the partial oxidation of propylene derived from fossil resources [8]

Methods

Results

Conclusion