Iron (II) impregnated double-shelled hollow mesoporous silica as acid-base bifunctional catalyst for the conversion of low-quality oil to methyl esters

Abstract

To promote the use of low-quality oils in producing biodiesel, a bifunctional acid-base catalyst Fe/DS-HMS-NH2 is fabricated using the two-step condensation technique. The obtained Fe/DS-HMS-NH2 is of a doubled shell structure in spherical shape with a uniform size of 156 nm. Its hollow core (with a diameter of 86 nm) and two spatial shells with different active sites enables the esterification and transesterification reactions to be accomplished in a one-pot synthesis. The influences of four independent reaction variables on the yield of fatty acid methyl esters YF was studied, including catalyst loading mc, reaction time t, reaction temperature T, and the methanol to degummed palm oil mass ratio rm/o. The highest yield was obtained at 85.36% (w/w) when mc = 6% (w/w), t = 4.5 h, T = 60 °C, and rm/o = 6:1. The Fe/DS-HMS-NH2 shows a good recyclability with YF > 80% (w/w) up to three reaction cycles.