REACTIONS: THERMODYNAMIC ASPECTS, KINETICS, AND CATALYSIS - Biomass as a Sustainable Energy Source for the Future - page 131

It is important to highlight that in chemistry the mass conservation law is the conserva-
tion of the number of atoms and this does not always implies the conservation of the
number ofmolecules.Molecules canbebrokendownormerged, but the atoms stay intact.
In RX. 5.1, nothing is said about:

￿ The elementary reactions that define the entire reaction mechanism (an elemen-

tary reaction is a reaction that proceeds through only one transition state, i.e., one
mechanistic step)

￿ The rate of the reaction itself

In order to have a reliable and real description of the phenomena going on, we need to
have a look at the elementary reactions as, e.g.,

CO+OH ! CO 2 +H ð RX : 5 : 2 Þ

This is an elementary reaction of the complete mechanism for the methane oxidation
in the gas phase (Bowman, 1975).
An example of a complete reaction mechanism can be given for the Fischer -

Tropsch synthesis. The Fischer Tropsch synthesis, is

a collection of chemical reactions that converts a mixture of carbon monoxide and
hydrogen into liquid hydrocarbons. The process, a key component of gas-to-liquid
technology, produces a synthetic lubrication oil and synthetic fuel, typically from
coal, natural gas, or biomass. Its complete reaction mechanism is given by Kellner
and Bell (1981), where S denotes the substrate (e.g., an active site):

- Tropsch process, or Fischer -

CO+ S !

CO S

ð RX : 5 : 3 Þ

CO S +S ! C S +O S ð RX : 5 : 4 Þ

H 2 +2S ! 2H S ð RX : 5 : 5 Þ

H 2 +O S ! H 2 O+S ð RX : 5 : 6 Þ

C S +H S ! CH S +S ð RX : 5 : 7 Þ

CH S +H S !

CH 2S +S ð RX : 5 : 8 Þ

CH 2S +H S ! CH 3S +S ð RX : 5 : 9 Þ

CH 3S +H S ! CH 4 +2S ð RX : 5 : 10 Þ

CH 3S +CH 2S ! C 2 H 5S +S ð RX : 5 : 11 Þ

C 2 H 5S +S ! C 2 H 4 +H S +S ð RX : 5 : 12 Þ

C 2 H 5S +H S ! C 2 H 6 +2S ð RX : 5 : 13 Þ

C 2 H 5S +CH 2S ! C 3 H 7S +S ð RX : 5 : 14 Þ

etc.