Biodiesel production using solid metal oxide catalysts

Abstract

Biodiesel production is worthy of continued study and optimization of production procedures due to its environmentally beneficial attributes and its renewable nature. Heterogeneous transesterification is considered to be a green process. The process requires neither catalyst recovery nor aqueous treatment steps and very high yields of methyl esters can be obtained, close to the theoretical value. However, heterogeneously catalyzed transesterification generally requires more severe operating conditions, and the performance of heterogeneous catalysts is generally lower than that of the commonly used homogeneous catalysts. Heterogeneous catalysis for biodiesel production has been extensively investigated in the last few years. Many metal oxides have been studied for the transesterification process of oils; these include alkali earth metal oxides, transition metal oxides, mixed metal oxides and supported metal oxides. The use of solid metal oxides as catalysts in oil transesterification is well established, accordingly, researchers' attempts are now focused on how to attain the highest catalyst activity. Catalyst activity is a function of its specific surface area, base strength and base site concentration. High specific surface area, strong base strength and high concentration of base sites are characteristics of an active transesterification catalyst. This review provides a brief overview of the different metal oxides frequently used in the process of transesterification of oils for the production of biodiesel with special reference to the various methods of catalyst preparation and catalyst characterization. Reaction conditions and catalyst leaching analysis are also highlighted. Finally, concluding remarks regarding catalyst selection and catalyst preparation steps are provided.

Deactivation Processes, Regeneration Conditions and Reusability Performance of CaO or MgO Based Catalysts Used for Biodiesel Production—A Review

“…Hammett indicator method is usually used to determine the basic strength of the catalyst [5]. This method is based on the change in color of acid-base indicator such as aniline and its derivatives.…”

“…Heterogeneous catalysts, acidic, basic or neutral provide many advantages in the process such as less corrosive character, simple operating steps, safer handling of material, easy and cheap separation process of biodiesel from the reaction mixture, and little wastewater generation [3]. Between heterogeneous catalysts reported in literature for transesterification in biodiesel production, a large number of metal oxides offer an attractive alternative to overcome economic and environmental drawbacks of homogeneous catalysts [3] [4] [5] [6] [7]. One can note among them, alkaline earth metal oxides (BaO, CaO, MgO) and SrO [8].…”

Synthesis and Characterizations of Needle- Shaped Cuo Nanoparticles.

“…[19,20]. There have been very few studies on nano metal oxides catalysed transesterification to produce FAME (Fatty Acid Methyl Ester) [21][22][23]. Among the availing transition metal oxides, CuO is one of the potential p-type semiconductors and gains considerable attention due to its excellent optical, physical and magnetic properties [24][25][26][27].…”

Current Status of Biodiesel Production in Baja California, Mexico

“…Several studies have been performed using different oils as raw material, alcohols, as well catalysts, including homogeneous catalysts such as sodium hydroxide, potassium hydroxide and sulfuric acid and heterogeneous catalysts such as lipase (Nielsen et al, 2008), CaO (Lim et al, 2009) and MgO (Refaat, 2010).…”