Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis

Abstract

Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. The presence of FFA in WCO usually requires a pretreatment stage before subjecting it to methanolysis. In the present work, heterogeneously catalyzed methanolysis of WCO with and without pretreatment was investigated. Removal of FFA from WCO was conducted by using only quicklime or with the addition of a small amount of methanol (FFA to methanol = 1:3 molar ratio). The obtained results showed that pretreatment of WCO with quicklime at 30?C after 1 h reduces the FFA content by 72 %, while the adsorption capacity was determined to be 910 mg g-1. The adsorptive pretreatment, as a simple operation, using low-cost quicklime under mild conditions, had a positive effect on the transesterification rate with CaO?ZnO as a catalyst, enabling the achievement of over 96 % of biodiesel yield in only 15 min, compared to 1 h without the pretreatment. Furthermore, pretreated WCO allows an increase in repeated catalyst use and overall savings in the necessary amount of catalyst. The present study showed that quicklime is an economic, environmental-friendly, and sustainable material for FFA removal from WCO.

Optimization of Methyl Ester Through Simultaneous Esterification –Transesterification Reactions Using Waste Cooking Oil as Raw Material

“…At a wave number 1377 cm -1 it can be identified as a glycerol group, namely O-CH2 (mono-, di-, and triglycerides) which is generally found in processed oils and should not be present in Fatty Acid Methyl Ester (FAME). Symmetrical carboxylic bonds occur at wave numbers 1460-1400 cm -1 [8]. According to Shattesh Kumar, the peak between 1169 cm -1 and 1175 cm -1 is formed due to the methyl group being close to the carbonyl group.…”

“…The wasted cooking oil that has been collected is filtered using a filter cloth to separate the oil from impurities and food processing residues. The value of the acid number is obtained from the titration process and calculated using the following equation [8]:…”