Bifunctional Heterogeneous Catalyst for Biodiesel Production from Waste Vegetable Oil

Abstract

Bifunctional solid catalysts facilitate the esterification of free fatty acids (FFA) into alkyl esters alongside the transesterification reaction, which allows for the use of waste vegetable oils with high water and FFA contents for biodiesel production. This makes the process economically viable and greener, as the waste fats and oils are readily available. The concurrent esterification and transesterification of waste palm oil (WPO) and waste sunflower oil (WSO) with methanol was investigated in the presence of calcium oxide on alumina catalyst in a conventional batch process. The catalyst characterization showed the existence of calcium oxide aluminates (calcined at 750 °C), which exhibited crystalline phases with porous/spongy-like particles. The high concentration of CaO in CaO/Al2O3 was a favorable support material in the heterogeneously-catalyzed transesterification reactions. The optimum catalyst parameters for the production of fatty acid methyl esters (FAMEs) were observed at 65 °C for 4 h with a methanol-to-oil ratio of 9:1, 60% (waste palm oil, or WPO) and 80% (waste sunflower oil, or WSO), CaO/Al2O3 (% wt/wt) catalyst ratio as well as 4% CaO/Al2O3 concentration (% wt.) for WSO and WPO. The simultaneous esterification/transesterification reactions at optimum conditions on WPO and WSO led to high yield of FAMEs of 89, 61 and 55% for WPO and 54, 75 and 98% for WSO at catalyst ratios (wt %) of 60, 70 and 80% respectively. The use of bifunctional heterogeneous catalyst (CaO/Al2O3) with waste vegetable oil can result in high performance and the upscaling of biodiesel production.

Catalyst and Elemental Analysis Involving Biodiesel from Various Feedstocks

“…After applying the same calcination temperature (475 • C), the pore diameter in this study increased to 24 nm, which is superior by showing better permeability with an increased surface area. As seen in Table 2, this assisted in the transesterification of sunflower waste to biodiesel with a maximum yield of 98% using a lower catalyst weight and ratio (solid base: solid acid) compared to that used in achieving similar yields by Elias et al [65]. Additionally, the yield found was a lot more than that reported by Marinkovic et al when a high catalyst amount of 5.5 wt% was used prepared at high calcination of 700 • C [66].…”

Glycerol-Based Retrievable Heterogeneous Catalysts for Single-Pot Esterification of Palm Fatty Acid Distillate to Biodiesel

“…However, the yields dropped to 6–10% when the reaction temperature raised to 130 °C and 140 °C due to the increment of addition effective collision frequency (beyond optimized temperature) between PFAD-methanol mixture on the catalyst surface [ 33 ]. Thus, enhancing the effective collision between the methanol-PFAD phase with the acidic sites of glycerol catalysts for producing biodiesel at maximum yield of ideal temperature at 120 °C [ 45 ].…”

Progress on Modified Calcium Oxide Derived Waste-Shell Catalysts for Biodiesel Production

“…The formation of soap during reactions resulted in the poisoning of the catalyst surface, which resulted in the reduction of both transesterification reactivity and reusability. Besides, the presence of catalyst-soap suspension in the reaction medium makes the separation between glycerol and biodiesel product difficult and thus reduces the biodiesel yield [99].…”