ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Preparation and characterization of K-loaded Mg/Al mixed oxides obtained from hydrotalcites for transesterification of Camelina sativa oil

Miroslava Mališová, Michal Horňáček, Pavol Hudec, Jozef Mikulec, Martina Slezáčková, and Elena Hájeková

Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Bratislava, Slovakia

E-mail: miroslava.malisova@stuba.sk

Received: 14 April 2022  Accepted: 15 August 2022

Abstract:

The preparation and characterization of K-loaded Mg/Al mixed oxides as catalysts for the transesterification of nonfood Camelina sativa oil were studied. Transesterification was performed using three different potassium-loaded mixed oxides (MO) and the parent Mg/Al MO obtained from hydrotalcite by calcination and treated by impregnation. For K impregnation, three different K salt solutions were used as a K source. To observe the impact of K impregnation on the physicochemical properties of MO, analytical methods were used. X-ray diffraction, basicity, acidity, thermogravimetry, scanning electron microscopy, and textural properties showed a relationship between the type of K impregnation and the properties of the catalysts. Potassium caused an increase in the basicity of MO. The specific surface area (S_BET) of the MO loaded by potassium acetate (MO–CH₃COOK) increased after impregnation, but the pore volume decreased to half of the original value for all impregnated samples. However, impregnation led to an increase in acidity that negatively affected K-impregnated catalyst activity during the transesterification process. The highest ester content of 94.2 wt% was observed after 7 h of transesterification at 140 °C for the parent MO without impregnation. K-impregnated MO showed lower activity during transesterification and after 7 h reached around 65 wt% for both MO loaded with potassium nitrate (MO–KNO₃) and MO–CH₃COOK and almost 77 wt% for the MO loaded with potassium fluoride (MO–KF).

Graphical abstract

Keywords: Mg/Al hydrotalcite; Basicity; Acidity; Textural properties; Fatty acid methyl esters (FAME); Biodiesel

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02434-3

Chemical Papers 76 (12) 7585–7596 (2022)