Biodiesel Production from Waste Cooking Oil Catalyzed by a Bifunctional Catalyst

Vania Enguilo Gonzaga; Rubi Romero; Rosa María Gómez-Espinosa; Amaya Romero; Sandra Luz Martínez; Reyna Natividad

doi:10.1021/acsomega.1c03586

Biodiesel Production from Waste Cooking Oil Catalyzed by a Bifunctional Catalyst

ACS Omega. 2021 Sep 10;6(37):24092-24105. doi: 10.1021/acsomega.1c03586. eCollection 2021 Sep 21.

Authors

Vania Enguilo Gonzaga¹, Rubi Romero¹, Rosa María Gómez-Espinosa¹, Amaya Romero², Sandra Luz Martínez³, Reyna Natividad¹

Affiliations

¹ Chemical Engineering Lab., Centro Conjunto de Investigación en Química Sustentable, UAEM-UNAM, Universidad Autónoma del Estado de México, km 14.5 Carretera Toluca-Atlacomulco, Toluca 50200, Mexico.
² Chemical Engineering Department, University of Castilla-La Mancha, Avenida Camilo Jose Cela, 12, Ciudad Real 13071, Spain.
³ Faculty of Chemistry, Universidad Autónoma del Estado de México, Paseo Colón esq. Paseo Tollocan s/n, Toluca 50120, Estado de México, Mexico.

Abstract

The objective of this study was to prepare bifunctional catalysts based on iron and CaO and test them in the biodiesel production using waste cooking oil (WCO) as feedstock. Two iron precursors were studied, Fe₂O₃ and Fe(NO₃)₃·9H₂O. The identified crystalline phases were Ca₂Fe₂O₅ and CaFeO₃. Surface morphology and textural properties (distribution of active species, specific surface area, size, and pore volume) were also analyzed. Additionally, thermal stability was studied and 800 °C was established as the optimum calcination temperature. The density of both acidic and basic sites was higher with the catalyst prepared with Fe₂O₃ than with that prepared with Fe(NO₃)₃·9H₂O. The latter, however, leads to reach equilibrium in half of the time than with the former. This was ascribed to the ratio of acidic to basic sites, which is higher with the catalyst prepared with the precursor salt. This ratio not only affects the overall cost of the process by affecting the time at which equilibrium is reached but also by dictating the methanol/oil molar ratio at which the equilibrium is reached sooner. The prepared bifunctional catalyst allowed us to produce biodiesel with 90% of methyl ester content at atmospheric pressure, reaction temperature of 60 °C, reaction time of 2 h, with 12:1 M ratio of methanol/WCO, 10 wt % of Fe over CaO, and a catalyst loading of 5 wt %. This catalyst can be used at least 3 times. The so-obtained biodiesel met the European norm EN-14214 regarding viscosity and density.