Continuous Waste Cooking Oil Transesterification with Microwave Heating and Strontium Oxide Catalyst

Abstract

Biodiesel produced from waste cooking oils (WCOs) mixed with methanol was efficiently transesterified using a continuous fluid flow system with a focused microwave heating device. Strontium oxide (SrO) was added as the catalyst. The factors that most influence the biodiesel conversion rate were first estimated by considering the effects of oil-to-methanol ratio, added quantity of SrO, and microwave heating power on reaction time in a built-in batch unit. The optimal parameter values were then applied to a continuous fluid flow system, which simulates the conversion of a scaled-up quantity of WCOs into biodiesel. Under the optimum fluid flow velocity and an appropriate output temperature, a biodiesel conversion rate of ca. 93 % was reached, associated with the decomposition of ester bonds and the formation of a tetrahedral intermediate substance during the reaction.

Strontium Oxide Deposited onto a Load-Bearable and Porous Titanium Matrix as Dynamic and High-Surface-Contact-Area Catalysis for Transesterification

“…The alcohol is deprotonated with a base to make nucleophile tougher in the transesterification procedure [39]. Despite natural variations (e.g., those caused by the degradation of the SrO catalyst and the quality of olive oil), the conversion process of olive oil into biodiesel and the reaction rate are mainly based on the formation of the transesterification reaction [12]. SrO catalyst lowers the activation energy for the transesterification reaction, which promotes the decomposition of ester bonds and the formation of a tetrahedral intermediate substance.…”

“…Factors that may affect the reaction include the reaction temperature and the evaporation of methanol, which will also be varied with the oil:methanol ratio [40,41,42]. Previous studies have shown that the optimal oil-to-methanol ratio is about 1:6 [12]. Other ratios such as 1:4 and 1:8 have been studied.…”

“…Nevertheless, lower mean yields compared to that of 1:6 resulted [12,43]. Processing parameters such as the fluid flow velocity, which may reduce the clustering effect of reactants and soap formation, and energy efficiency, which may realize a temperature control, are of importance for carrying out the scale-up process [12]. In Figure 6b, we illustrate a practical use of Sr 0.5 -P-Ti_55 in a continuous process for biodiesel conversion and production.…”

“…With the porosity and considerable mechanical strength of P-Ti_55 and appropriate amount of SrO bonded with Ti-based matrix, an appropriate oil flowing speed penetrating into the porous matrix and reaction with the firmly attached SrO is feasible [13,14]. The Sr 0.5 -P-Ti_55 is thus promising to be employed in a continuous process for biodiesel conversion and production [12].…”

“…Besides, they perform much better in microwave-promoted transesterification reactions. Strontium oxide (SrO) is superior to other catalysts in terms of conversion and reaction time, but at the same time [12], it has a significant disadvantage: Since SrO remains in the biodiesel after the reaction, separation of the catalyst and the product requires neutralization washing, resulting in a large amount of industrial wastewater pollution to the environment.…”