Gases - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 18

CH 2 + H 2 O CO + 2 H 2

The two reactions are run in conjunction and adjusted by varying the
amount of oxygen and water. The reactions are run in such a manner as to
satisfy the need to balance the heat requirements and also the desired H 2 :CO
ratio.
The syn gas process is usually run for specific purposes. Examples include
feedstock for ammonia production, feedstock for methanol production,
feedstock for the Fischer-Tropsch synthesis, or for the energy output.
Depending on the reason for running the reaction, a different ratio of H 2 :CO
is needed. This ratio is influenced strongly by the material undergoing partial
oxidation. Coal gives a 1:1 ratio of H 2 :CO; petroleum about a 2:1 ratio and
natural gas somewhat higher than a 2:1 ratio as will be evident from the
discussion on methane oxidation.
Some of the principles can be illustrated with the partial oxidation of
methane. Methane is a major component of natural gas so this reaction is
important when natural gas is the feedstock.

2 CH 4 + O 2 2 CO + 4 H 2

This is an exothermic reaction. For processes occurring at constant pres-
sure, the heat flow can be expressed as an enthalpy change. Enthalpy (H) is
the internal energy of the system plus the product of pressure and volume.

H = E + PV

At constant pressure, the change in enthalpy equals the heat gained or
lost. We can calculate standard enthalpy changes of a reaction from standard
enthalpies of formation. Standard state is 1 bar pressure and a temperature of
298 ∘ K(25 ∘ C) and is symbolized by the degree sign after H as H ∘ .

∑ n ∑ n

H ∘ rxn = H ∘ f ( H ∘ f (

Δ Δ products )− Δ reactants )

The standard enthalpy of formation of a compound is the enthalpy change
for the reaction that forms one mole of the compound from its elements with
all substances in their standard states. Enthalpies of formation are readily
available. For CO (g) , H ∘ f =− H ∘ f =− 74.8

kJ/mol. Oxygen gas and hydrogen gas are each elements in their standard
state so

Δ 110.5 kJ/mol. For CH 4(g) Δ

H ∘ f = 0. For the partial oxidation of 2 moles of methane gas at

standard temperature and pressure, we can calculate the enthalpy change
to be:

Δ