Biodiesel production over Ca, Zn, and Al mixed compounds in fixed-bed reactor: Effects of premixing catalyst extrudates with methanol, oil, and fatty acid methyl esters

We studied the production of biodiesel as fatty acid methyl esters (FAMES) via transesterification of refined bleached deodorized palm oil with methanol in a fixed-bed reactor, using a new heterogeneous base catalyst in extrudate form. The catalyst extrudates were prepared using a dissolution-precipitation method from enamel venus shells (Meretrix meretrix) in the presence of zinc nitrate and alumina as binder precursors. The effects of addition of hydroxyethylcellulose as a plasticizer and of the extruder type on the extrusion process and physicochemical properties of the extrudates were studied. The as-prepared catalyst extrudate was a mixture of Ca, Zn, and AI compounds. Calcination at 400 degrees C generated CaO as the major active phase, which was dispersed on the surface of an alumina support (ZSAH-400). The maximum FAME yield obtained over ZSAH-400 was 65% in a fixed-bed reactor operated at a methanol:oil molar ratio of 30:1, 65 degrees C, and ambient pressure. The effects of premixing the catalyst extrudates with methanol, vegetable oil, and commercial methyl esters (CiVIEs) with different fatty acid chain lengths were investigated to improve FAME formation. The ZSAH-400 extrudate premixed with different CME types gave a stable FAME yield of similar to 96.5% throughout the operation. The promotion effect provided by premixing with methanol or oil was much less pronounced. A three-phase diagram, thermogravimetry, and solubility parameters suggest that the CME-rich layer covering the extrudate surface reduces the mass transfer limitations caused by immiscibility of the reactants. (C) 2016 Elsevier B.V. All rights reserved.