Zn,Al-catalysts for heterogeneous biodiesel production: Basicity and process optimization

• Published in: Energy (Oxford) Vol. 75; pp. 453 - 462
• Main Authors: Veiga, Paula Moraes, Luna, Aderval Severino, de Figueiredo Portilho, Marcio, de Oliveira Veloso, Cláudia, Henriques, Cristiane Assumpção
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2014; Elsevier
• Subjects: Alcohols; Alternative fuels. Production and utilization; Aluminum; Applied sciences; Biodiesel; Catalysis; Catalysts; Chemistry; Density; Energy; Esters; Exact sciences and technology; Fuels; General and physical chemistry; Miscellaneous; Response surface methodology; Soybean oil; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Transesterification; Zn,Al-mixed oxides; Zn,Al-mixed oxides; Transesterification; Response surface methodology; Soybean oil; Biodiesel; Heterogeneous catalysis; Biofuel
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2014.08.001

Methyl esters produced by transesterification of vegetable oils are the main components of biodiesel, an alternative, biodegradable, non-toxic biofuel produced from renewable resources. The use of solid catalysts allows the development of environmentally friendly processes to produce biodiesel. In this work, Zn,Al-mixed oxides with different Al/(Al + Zn) molar ratios were studied as catalysts for the transesterification of soybean oil with methanol. TPD-CO2 (temperature programmed desorption of CO2) and model reactions such as retroaldolization of diacetone alcohol and 2-propanol transformation were employed to determine the basic properties of the catalysts. The catalytic activity was influenced by the chemical composition of the catalyst and showed a good correlation with basic site density determined by TPD-CO2. The RSM (response surface methodology) was used to select experimental conditions such as alcohol/oil molar ratio, reaction temperature, and catalyst loading that maximize fatty acid methyl esters yield. The best experimental conditions indicated by RSM were reaction temperature of 182.5 °C, catalyst loading of 5.0 wt.%, and alcohol/oil molar ratio of 45, that provided a biodiesel yield of 86% without significant leaching of the catalyst.
•Zn,Al-mixed oxides are catalytically active for the transesterification of soybean oil with methanol.•Zn content affected textural and basic properties, and FAME yield.•The activity of Zn,Al-mixed oxides is related to basic sites density measured by TPD-CO2.•The use of response surface methodology allows the optimization of FAME yield.