(704b) Simultaneous Reaction and Purification Process for Continuous Production of High Quality Biodiesel From Acid Oils

Authors: 
Yonemoto, T., Tohoku University
Shibasaki-Kitakawa, N., Tohoku University
Ihara, T., Tohoku University



Introduction

Even today, the refined edible
oils are mainly used as feedstocks for biodiesel,
fatty aid ester, and this causes an increase in the production cost of biodiesel.
  The side-stream products,
such as soapstocks, acid oils and deodorized
distillates, obtained during edible oil refining have been suggested for use as
alternative feedstocks for biodiesel.   Especially, the crude oils of palm
and rice bran have a high content of free fatty acid and, hence the amount of
acid oils generated is large, about 10-15 wt% of refined oil output.   There are some industrial uses for
acid oils such as ink, but most acid oils are burned out as waste.   The acid oils consist of about 95
wt% of free fatty acids (FFAs) and 5 wt% of acylglycerols
(TAGs) and these components can be converted to fatty acid ester by esterification or transesterification
using homogeneous acid catalyst.  
However, these reversible reactions do not go to completion, so that the
separation and purification processes to remove the by-products and unreacted reactants are necessary to produce the high
quality biodiesel in compliance with all international standards.   These processes cause a further
increase in the production cost of biodiesel and there is no commercially
realizable process for biodiesel production from acid oils.

The purpose of this research is to construct
a simple and economical production process of high quality biodiesel from waste
acid oils using the ion-exchange resins as catalysts and adsorbents.

Materials and methods

The acid oil was
donated by the rice bran oil company.   Figure
1 shows a schematic diagram and photograph of our production process.   Two columns were individually
packed with the cation-exchange resin, Diaion PK208LH, and the anion-exchange resin, Diaion PA306S, respectively, and then connected in
series.   The temperature of
each column was kept constant at 50 °C.   The mixed solution at the molar
ratio of methanol to the total fatty acid residue in the oil of 2:1 was
supplied to the bottom of the first column at the constant flow rate.   The effluent from the process was
analyzed to check the quality of biodiesel.

Results
and discussion

Table 1 shows the analytical result of
standard tests for biodiesel quality of product without purification except for
removing residual methanol by evaporation.   The contents of product and
residual reactants fully met the standard values.   This indicated that free fatty acids and
acylglyceroles
were converted to biodiesel by esterification and transesterification with cation-
and anion-exchange resin catalysts, respectively.   The content of byproducts also met
the standard values without downstream purification processes to remove them.   This was because the by-products,
water and glycerol were adsorbed on the anion-exchange resin and the effluent
was free from them.   Other properties for contaminants and
fuel properties were found to satisfy with the standards.

Figure 2 shows the photographs of the feed
oil and the effluents from the first and second columns at room
temperature.   The feed oil was
liquefied by the esterificaion through the first
column.   The dark brown pigment was removed by the adsorption through
the second column.

fig1.gif
Fig.1 Schematic
diagram (a) and photograph (b) of production process

fig2.gif

Fig.2 Photographs
of feed oil (a) and effluents from the first (b) and second (b) columns at room
temperature

Table 1 Analytical result of standard tests for
biodiesel quality of product


properties

units

standards

product without purification

EN14214

product

FAME

[wt%]

≥96.5

97.1

reactants

acid value (FFA)

[mg-KOH/g]

≤0.5

0.04

monoglyceridel

[wt%]

≤0.8

0.48

diglyceride

[wt%]

≤0.2

0.02

triglyceride

[wt%]

≤0.2

0.03

byproducts

water

[mg/kg]

≤500

291

free glycerol

[wt%]

≤0.02

0.00

total glycerol

[wt%]

≤0.25

0.13

contaminants

sulfur

[mg/kg]

≤10

<5

sulfated ash

[wt%]

≤0.02

<0.005

phosphorous

[mg/kg]

≤4

<1

carbon residue (at 10% distillation residue)

[wt%]

≤0.3

0.11

total contamination

[mg/kg]

≤24

2

fuel properties

density at 15°C

[kg/m3]

≥860, ≤900

880.4

kinematic viscosity at 40°C

[mm2/s]

≥3.5, ≤5.0

4.353

flash point

[°C]

≥101

128.0

cetane number

[-]

≥51

53.1

iodin value

[-]

≤120

94.9

methyl linolenate

[wt%]

≤12

1.2