Environmental Engineering Reference
In-Depth Information
calculating from the rest of the specifications, the total alcohol content allowed by the EU and
United States is 99.8% v/v minimum and 99.0% v/v minimum, respectively (White Paper 2007).
9.3.8 phe
pHe is used to ensure that some strong acids, such as sulfuric acid (H
2
SO
4
), hydrochloric acid (HCl),
and phosphoric acid (H
3
PO
4
), are within acceptable limits. These acids enter the bioethanol produc-
tion process in the manufacturing step and carryover in the final product (IFQC 2004). Although
even a low level of these strong acids in bioethanol can cause corrosion problems (RFA 2009), the
acidity of the fuel is not always influenced so much as to be detectable by some other test methods
(e.g., the acidity test; Gray 2005) that better measure weak acids (IFQC 2004).
The pHe of bioethanol is tested after the addition of denaturant and corrosion inhibitor (Gray
2005) and should be limited to 6.5-9. The use of bioethanol with pHe below this range may dam-
age the engine because of corrosion of fuel pump and injector equipment. When pHe values exceed
this range, the fuel contains more alkaline components and the plastic parts of the fuel system may
be damaged. These effects of bioethanol's pHe increase with the level of bioethanol blend; that is,
are more important for E75 and E85 blends than for E5 or E10 (IFQC 2004). pHe can be adjusted
by the use of sodium hydroxide (NaOH). However, this can have some side effects and a sodium
content test is required (IFQC 2004) (see Section 9.3.14).
Currently, the United States and Brazil limit the pHe range to 6.5-9 for anhydrous denatured
bioethanol (ASTM D6423) and 6-8 for hydrated bioethanol (NBR 10891). However, given that
the ASTM method (ASTM D6423) is not for nonaqueous solutions, such as denatured etha-
nol, its use for the estimation of the pHe of this fuel has to be based on empirical estimation.
Consequently, the repeatability and reproducibility of the results are under investigation (IFQC
2004; WWFC 2008). For this reason, CEN has excluded this test from its bioethanol quality
specification (White Paper 2007). Another workable test method for pHe is under development
(White Paper 2007).
9.3.9 a
cidity
Acidity specification is used to ensure that some weak acids (e.g., acetic acid) are within acceptable
limits (IFQC 2004). This method also measures acidity, as does pHe (see Section 9.3.8), but it is
effective mainly for the measurement of the very dilute aqueous solutions of low-molecular-weight
organic acids (Gray 2005). These solutions are corrosive to a wide range of metals and alloys (RFA
2009) and may result in some long-term wear problems in vehicles. Nevertheless, this correlation
between acidity by acetic acids and corrosion is doubted by some experts (White Paper 2007).
Contrary to the strong acids, there is no negative effect from the low concentration of these acids in
bioethanol (IFQC 2004) and consequently bioethanol blenders should keep their acidity value at a
very low level (WWFC 2008).
The United States currently limits the acidity by acetic acid at 0.0074% m/m (ASTM D1613).
This limit is approximately the same as that of the EU [0.007% m/m (EN 15491)] and almost double
that of the Brazilian limit [0.0038% m/m (ABNT NBR 9866)]. The lower limit of Brazil can be
explained by the higher concentration of ethanol in its blends (White Paper 2007). These limits are
not expected to change in the near future, and this specification can be eliminated after the develop-
ment of a more accurate pHe test method (White Paper 2007).
9.3.10 p
hoSphoruS
c
ontEnt
Phosphorus enters the bioethanol production chain from certain performance additives or during the
fermentation process, especially when synthetic ethanol is produced from ethylene and the H
3
PO
4
