Results and Discussion
Fuel
Properties of BWCO and Biodiesel Blends
Table S4 shows the percentage of FAME in BWCO. As a consequence, BWCO
contained higher levels of saturated fatty acid methyl esters (38.42
wt.%)
that
resulted in its poor cold flow properties.
The fuel properties of biodiesel blends (B20, B40, B60, and B80) are
listed in Table 2. As shown in Table 2, various indicators of biodiesel
blends are better than BWCO. Among them, the kinematic viscosity, acid
value, and flash point of the blends comply with ASTM D7467. However,
when the proportion of biodiesel with high acid value in the blends
increases (B60 and B80), the acid value of the biodiesel blends becomes
outside the standard range. It is worth mentioning that B20 has the best
low-temperature performance, and CP, CFPP, and PP are -2, -4 and -14 °C,
respectively. With the increase in BWCO content, the cold flow
properties of the blends gradually deteriorate probably because BWCO
contains more high melting point unsaturated fatty acid esters. Since
the n-alkanes in diesel have a lower melting point, when the proportion
of diesel in blends increases, wax crystals are formed at a lower
temperature. Therefore, B20 has better cold flow properties than other
biodiesel blends.
Depressive Effect of
RMC-MB-NVP Terpolymers on Biodiesel Blends
The CP, CFPP, and PP of B20 are -2, -4 and -14 °C, respectively. The
reduction in CP (ΔCP), CFPP (ΔCFPP), and PP (ΔPP) of B20 treated with
1000, 2000, and 3000 ppm RMC-MB-NVP (R=12, 14, 16, 18) are shown in Fig
1, and that of B20 treated with 500, 1500, and 2500 ppm RMC-MB-NVP are
presented in Fig S4. The decrease in
CP is the smallest compared with ΔPP and ΔCFPP under the same
conditions.
Fig 1 (e, f) shows that RMC-MB-NVP terpolymers exert higher ΔCFPP and
ΔPP at the dosage of 2000 ppm. At this dosage, the n-alkyl chain length
and monomer molar ratio of terpolymers have important effects on the
low-temperature performance of biodiesel blends.
When the terpolymers have different
monomer proportions, with decreasing ratio of the NVP monomer, the
depressing effect initially increases and then decreases. When the
monomer molar ratio of the terpolymer is 5:1:1, ΔCFPP have the best
reducing effect because the appropriate NVP ratio can increase the
solubility of the terpolymer, thereby improving the low-temperature
fluidity of biodiesel. When the terpolymers have different side carbon
chain lengths, with increasing carbon number in the side chain alkane,
the depression effect reveals a trend of initially increasing and then
decreasing. C16MC-MB-NVP terpolymers have the best
depressing effect, which can be attributed to the influence of the
length of the n-alkyl side chain on CFPP and PP in PPDs. In these
experiments, C16MC-MB-NVP (5:1:1) presented the greatest
reduction on the CP, CFPP, and PP of B20 (2, 4 and 9 °C). Thus, 2000 ppm
C16MC-MB-NVP (5:1:1) has the best depressing effect, and
B20 has optimal performance compared with other biodiesel blends.