LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 6A: TOOLS AND DATABASES 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
3. Results
The chemical supply chain for glyphosate is shown in Fig. 1. Each block represents one gtg. A chemical
name with a bold font indicates multi-output processes. The three gtgs with a grey background, glyphosate,
PMIDA, and DSIDA may be run as an integrated glyphosate process. However, PMIDA and DSIDA are
available as commercial products, and thus these were created as separate gtgs.
The disodium salt of iminodiacetic acid (DSIDA) is produced from diethanol amine and sodium hydroxide
(Rxn. 1). The hydrogen formed is assumed to be combusted for potential heat recovery, leading to a net
negative energy consumption in this gtg. DSIDA, phosphorus trichloride, formaldehyde, sodium hydroxide,
and water are converted into phosphonomethyl iminodiacetic acid (PMIDA) and sodium chloride in a separate
gtg. The overall reaction takes place in several steps and variations on the order of reactions are described
in the patent literature (US 4,724,103; US 5,527,953; US 5,312,972; EP 599,598; US 5,527,953; US
5,688,994; US 6,515,168; WO 00/22888). Large quantities of NaCl are formed in the net reaction (Rxn. 2),
and the NaCl is considered to be a chemical emission to wastewater. In the final step, PMIDA is oxidized by
sparging oxygen through a series of reactors with a dilute aqueous solution of PMIDA (Rxn. 3). Carbon
dioxide is a direct by-product in this reaction. Additionally, 20% of the formaldehyde by-product is assumed
to be oxidized to CO2 and water. The remainder of the formaldehyde exits in a dilute aqueous waste stream.
C4H11NO2+2NaOH HN(CH2COONa)2+ 4H2 Rxn. 1
+NaOH + H2
Diethanolamine + sodium hydroxide DSIDA (disodium salt of iminodiacetic acid) + hydrogen
PCl3 + H2CO + HN(CH2COONa)2+ H2O +NaOH C5H10NO7P + 3NaCl Rxn. 2
+ + +H2O + NaOH + NaCl
phosphorus trichloride + formaldehyde + DSIDA + water + sodium hydroxide PMIDA + sodium chloride
C5H10O7NP + ½ O2 C4H8NO4 + CO2 + H2CO Rxn. 3
+ O2 + CO2 +
PMIDA + oxygen glyphosate + carbon dioxide + formaldehyde
The mass yields and stoichiometric yields for each of these three gtgs are shown in Table 1. The
stoichiometric yields were about 93% from each of the primary inputs (diethanol amine to DSIDA to
PMIDA to glyphosate). The stoichiometric yield from diethanol amine is 80%. The mass yields, which are
calculated as the total product divided by the total reactant (to each gtg) from Fig. 1, are relatively low (50 –
90%). This is due in part to the reaction stoichiometry, which produces a number of reaction byproducts that
are treated as waste. The overall yield from ethylene oxide in this chemistry is < 50%, because two ethylene
oxides are used per molecule of PMIDA. One of these ethylene oxide groups is oxidized to CO2 and formaldehyde
in the glyphosate gtg as discussed in US 7,750,180.
Table 1. Yields for glyphosate gtgs. Apparent mass yields are from Figure 1. The other yield values are
stoichiometric, and refer to overall process yield based on inputs to the process.
Gtg Mass yield Yield I1 Yield I2 Yield I3 Inputs corresponding to yield data
Glyphosate a 61% 93% 47% I1 = PMIDA, I2 = oxygen
PMIDA 47% 93% 71% 84% I1 = DSIDA, I2 = formamide, I3 = PCl3
DSIDA 86% 92% 88% I1 = diethanol amine, I2 = sodium hydroxide
a The mass yield for DSIDA excludes the oxygen input, which is used to recover heat from hydrogen.
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