Enhancing Biodiesel Production from Soybean Oil Using Ultrasonics

Abstract

Our objective was to determine the effect of ultrasonics on biodiesel production from soybean oil. In this study, ultrasonic energy was applied in two different modes: pulse and continuous sonication. Soybean oil was mixed with methanol and a catalytic amount of sodium hydroxide, and the mixture was sonicated at three levels of amplitude (60, 120, and 180 μm pp ) in pulse mode (5 s on/25 s off). In the continuous mode, the same reaction mixture was sonicated at 120 μm pp for 15 s. The reaction was monitored for biodiesel yield by stopping the reaction at selected time intervals and analyzing the biodiesel content by thermogravimetric analysis (TGA). The results were compared to a control group, in which the same reactant composition was allowed to react at 60 °C for intervals ranging from 5 min to 1 h without ultrasonic treatment. It was observed that ultrasonic treatment resulted in a 96% by weight isolated yield of biodiesel in less than 90 s using the pulse mode, compared to 30−45 min for the unsonicated control sample with comparable yields (83−86%). In the pulse mode, the highest yield (96%) was obtained by sonicating the mixture at 120 μm pp amplitude. In the continuous sonication mode, the highest biodiesel yield was 86% by weight, which was obtained in 15 s. Our objective was to determine the effect of ultrasonics on biodiesel production from soybean oil. In this study, ultrasonic energy was applied in two different modes: pulse and continuous sonication. Soybean oil was mixed with methanol and a catalytic amount of sodium hydroxide, and the mixture was sonicated at three levels of amplitude (60, 120, and 180 μm pp ) in pulse mode (5 s on/25 s off). In the continuous mode, the same reaction mixture was sonicated at 120 μm pp for 15 s. The reaction was monitored for biodiesel yield by stopping the reaction at selected time intervals and analyzing the biodiesel content by thermogravimetric analysis (TGA). The results were compared to a control group, in which the same reactant composition was allowed to react at 60°C for intervals ranging from 5 min to 1 h without ultrasonic treatment. It was observed that ultrasonic treatment resulted in a 96% by weight isolated yield of biodiesel in less than 90 s using the pulse mode, compared to 30-45 min for the unsonicated control sample with comparable yields (83-86%). In the pulse mode, the highest yield (96%) was obtained by sonicating the mixture at 120 μm pp amplitude. In the continuous sonication mode, the highest biodiesel yield was 86% by weight, which was obtained in 15 s.

Continuous and pulse sonication effects on transesterification of used vegetable oil

“…A 93.5% of biodiesel yield was obtained at a reaction time of 0.5 min under pulse conditions which can be compared to the 92% yield obtained during 3 h reaction time using 5 wt.% CaO catalyst under conventional heating and stirring, although this is a heterogeneous catalyst [43]. Our observations were found to be similar to those by Chand et al [41]. They studied a comparison on pulse and continuous mode operations.…”

“…Unlike pulse sonication, the yields obtained from continuous sonication increased from 0.5 min to 1 min but started to decrease when 1.5 min was reached. According to Chand et al [41], continuous ultrasound irradiations are not recommended for long reaction times because it could affect the biodiesel yield. Similar observation was made in our study as well.…”

Heterogeneous catalysis for sustainable biodiesel productionviaesterification and transesterification

“…Chand et al observed similar improvements in heat transfer and reaction time applying ultrasonication to soybean oil transesterification. 270 However, both groups employed a homogeneous NaOH catalyst, hindering product purification. Ultrasound was used with a heterogeneous catalyst for continuous biodiesel production from palm oil by Salamatinia et al 271 BaO and SrO catalysts were tested, and ultrasound again found to reduce the reaction times and catalyst loadings needed to achieve 495% FAME yields.…”

“…270 The origin of ultrasonic enhancements in respect of reaction mixing via e.g. cavitation or microstreaming, remains a matter of debate.…”

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst

“…Synthesis of Al(HSO 4 ) 3 . (Chand et al, 2010). The temperature range employed was 50-500°C at a ramp rate of 10°C/min.…”