無

A study on the application of ultrasound on in situ methanolysis of rice
bran to produce biodiesel has been carried out in this work. Biodiesel production
cost may be reduced by using a low-cost raw material, such as rice bran, and by in
situ esterification (methanolysis), yet it gives low conversion for rice bran with
low free fatty acid (FFA) content. In order to improve production yield for rice
bran with mid- to low FFA content, the effects of reaction temperature, time, FFA
content on ultrasound-assisted methanolysis were investigated.
From the study, it can be concluded that FAME content and yield increase
with increasing temperature, but conversions at different temperatures do not
show significant differences. As temperature increases from 30 to 60oC, FAME
content and yield increase from 33.67 to 46.56% and 16.07 to 28.37%,
respectively.
For in situ methanolysis of rice bran with low FFA content (13.27%) with
mechanical stirring, as time proceeded from 1 to 4 h, FAME content, conversion
and yield increased from 33.85 to 70.73%, 53.52 to 84.80% and 20.53 to 72.59%,
respectively. For ultrasound-assisted in situ methanolysis of rice bran with
medium FFA content (47.87%), as time proceeded from 1 to 6 h, FAME content,
conversion and yield increased from 70.99 to 85.63%, 81.96 to 96.33% and 60.33
to 84.69%, respectively. For ultrasound-assisted in situ methanolysis of rice bran
with low FFA content (13.27%), as time proceeded from 1 to 4 h, FAME content,
conversion and yield increased from 44.69 to 70.76%, 57.69 to 89.29% and 26.61
to 74.76%, respectively. For ultrasound-assisted in situ methanolysis of rice bran
with low FFA content (13.27%) with mechanical stirring, as time proceeded from
1 to 4 h, FAME content, conversion and yield increased from 46.87 to 76.46%,
55.99 to 87.14% and 29.75 to 79.08%, respectively.
Higher initial FFA content resulted in higher FAME content, conversion,
and yield at reaction times of 1 and 2 h. At 4 h, higher FFA content resulted in
significantly higher conversion and yield, but not the FAME content. At a reaction
tine of 1 h, as the FFA content changes from 13.27 to 47.87%, the increase in
FAME content, conversion, and yield are 58.85, 42.05, and 126.75 %,
respectively.
In general, ultrasound-assisted in-situ methanolysis with mechanical
stirring performs better than other modes of reaction studied in this work. Slight
differences were found in overall performance for these 3 types of operation mode,
they impact significantly on FAME content and yield at reaction times of 1 and 2
h, but no significant effect was found in purity, conversion, and yield at 4 h.
Compared with in-situ reaction without ultrasound, ultrasound-assisted reaction
increased FAME content, conversion, and yield by 32.03, 7.800, and 29.62 %,
respectively, at a reaction time of 1 h. Ultrasound-assisted and mechanically
stirred reaction increased FAME content, conversion, and yield by 38.47, 4.613,
and 44.95 %, respectively, at a reaction time of 1 h.

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