Biodiesel Production Using Ultrasonic-Assisted Heterogeneous Catalytic Process
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Date
2011-04
Authors
Salamatinia, Babak
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Biodiesel, a product from the transesterification of alcohol and vegetable oils or animal fats, is a greener alternative to petroleum diesel. Biodiesel production process assisted by means of ultrasonic energy has been investigated. Alkaline metal earth oxide catalysts i.e. MgO, CaO, BaO and SrO were employed to catalyze the transesterification process. Initially these catalysts were tested in conventional mixing method to find out the best catalytic activities and to serve as background data. Ultrasonic was initially introduced into the reaction as a replacement for mechanical mixing. Effects of process variables for the reaction in the case of both non-ultrasonic and ultrasonic-assisted biodiesel production were investigated. The process variables were the reaction temperature (50-70 °C), catalyst loading (0.5-3 % w/w.), methanol to oil ratio (6:1-15:1) and reaction time (10-240 min). The best operating conditions were used to study the effects of varying ultrasonic conditions such as pulse on (1-9 s), pulse off (1-9 s), ultrasonic power (20-70 % of amplitude), reaction time (10-50 min) and sample weight (30-60 g). Response surface methodology (RSM) was used to optimize the variables.The best conditions were verified using different oil sources i.e. corn oil, canola oil, sunflower oil and used palm oil. The highest biodiesel yield was achieved at a methanol to oil ratio of 9:1. For BaO catalyst, the biodiesel yield showed a graduate increase above 65 °C while for the other two catalysts, it dropped. The best yield was observed using BaO with 95.4% of yield followed by SrO with a yield of 86.4 %. The optimum conditions were achieved at pulse on for 9 s, pulse off of 2 s, reaction time of 30.7 min, at a power of 130 W and an oil amount of 52 g. Compared to stirrer mixing reaction, ultrasonic-assisted process showed significant reduction in time (from 120-180 min to 30-50 min) and catalyst loading (from 3-5 % to less than 2.8 %) to reach up to 96 % yield. The increase in the reaction rate was attributed to the collapse caused of cavitation bubbles by ultrasonic which led to high intensity mixing. That improved the contact between the reactants.
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Keywords
Biodiesel production process assisted , by means of ultrasonic energy