Question

Why adding water to the feed of formic acid makes it a better fuel?

What other additives would you consider instead and why?

Answer 1

Formic acid decomposes primarily to CO and H2 0 in the gas phase, but to CO, and
H, in the aqueous phase. Ab-initio quantum chemical calculations were performed,
using Hartree-Fock and density functional methods, to seek an explanation for this
behavior. The effect of water on the two decomposition pathways and on the isomeriza-
tion of formic acid was determined. The transition state structures were fully optimized
and include up to two water molecules. In the absence of water, dehydration is more
favorable than decarboxylation. The presence of water reduces the activation barriers for
both decomposition pathways, but decarboxylation is consistently more favorable than
dehydration. The water molecules actively participate in the bond-breaking and bond-
forming processes in the transition state. The reduction in the activation barriers with
the addition of water indicates that water acts as a homogeneous catalyst for both
dehydration and decarboxylation, whereas isomerization of formic acid occurs indepen-
dently of water. Water has a strong effect on the relative stability of the formic acid
isomers, acid - water complexes, and transition states. The relative stability of the transi-
tion states plays an important role in determining the faster decomposition pathway.So adding water make it a better fuel. The decomposition of 0.05−0.7 M formic acid in supercritical water was investigated in a temperature range of 550−650 °C and a pressure range of 24−30 MPa for residence times of 16−46 s. The gaseous products were composed of H2 and CO2 as major components, and CO as a minor one, which indicates that decarboxylation is the dominant reaction pathway and dehydration is secondary. High temperature increased hydrogen production. Compared with temperature, pressure had less effect on hydrogen production. Carbon gasification efficiency reached 94.5% at a residence time of 20 s, and extending the residence time had very little effect. High concentration of formic acid led to side-reactions, which caused a great decrease of hydrogen production. The mechanisms for formic acid decomposition were studied computationally using the GAUSSIAN 03 suite of programs. Results show that water takes part in the formic acid decomposition reaction as a catalyst, which promotes both the decarboxylation and dehydration, and the promoting effect on decarboxylation is more apparent.So by adding water ,we can dilute formalic acid, and hidrogen production is also increased.

The liquid-phase carbonylation of methanol
to methyl formate in the presence of a
basic catalyst such as sodium or potassium
methoxide (NaOCH3 or KOCH3) and further
hydrolysis to formic acidhas been
practiced industrially already since the early
1980s. Potassium methoxide is more soluble
in methyl formate than sodium methoxide,
and correspondingly gives a higher reaction
rate