A facile preparation of hydroxylated magnesium fluorides as an active catalyst for biodiesel production: The effect of different aging times

[Display omitted] •The MgF2−x(OH)x samples with various aging times are prepared by sol-gel method.•The aging time greatly affects the crystallinity and porosity of samples.•The solids are applied as a heterogeneous catalyst to yield biodiesel.•The MgF2−x(OH)x catalyst aged for 1 h shows excellent catalytic evaluation. The MgF2−x(OH)x with various aging times (1, 3, 6 and 12 h) have been obtained from sol-gel technique. The structure, chemical bonding and porosity of material were studied by X-ray diffraction, Fourier-transform infrared spectrofotometer and N2 adsorption-desorption isotherms. The crystallinity and the number of OH groups of solids increase linearly with increasing of aging time. Moreover, the pore diameter and volume decrease from 4.79 to 2.82 nm and from 0.165 to 0.107 cm3/g, while the surface area increases from 137.84 to 150.55 m2/g with the increase in aging times, respectively. The catalytic activity of materials to yield biodiesel from Crude Palm Oil shows that the biodiesel yield decreases from 64.43 to 14.89, 12.17 and 10.49% with increasing aging times, respectively. The best performance of the catalyst depends on the greater values of pore size and volume as well as the lower crystallinity and the smaller number of OH groups.