# Partial oxidation

Partial oxidation (POX) is a type of chemical reaction. It occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas which can then be put to further use, for example in a fuel cell. A distinction is made between thermal partial oxidation (TPOX) and catalytic partial oxidation (CPOX).

## Principle

Partial oxidation is a technically mature process in which natural gas or a heavy hydrocarbon fuel (heating oil) is mixed with a limited amount of oxygen in an exothermic process.

• General reaction equation (without catalyst, TPOX): $\mathrm{C_nH_m + \frac{2n+m}{4} \ O_2 \rightarrow n \ CO + \frac{m}{2} \ H_2O}$[1]
• General reaction equation (with catalyst, CPOX): $\mathrm{C_nH_m + \frac{n}{2} \ O_2 \rightarrow n \ CO + \frac{m}{2} \ H_2}$
• Possible reaction equation (heating oil): $\mathrm{C_{12}H_{24} + 6 \ O_2 \rightarrow 12 \ CO + 12 \ H_2}$
• Possible reaction equation (coal): $\mathrm{C_{24}H_{12} + 12 \ O_2 \rightarrow 24 \ CO + 6 \ H_2}$

The formulas given for coal and heating oil show only a typical representative of these highly complex mixtures. Water is added to the process for getting both the extreme temperatures as well as extra control on the formation of soot.

## TPOX

TPOX (thermal partial oxidation) reactions, which are dependent on the air-fuel ratio, proceed at temperatures of 1200°C and above.

## CPOX

In CPOX (catalytic partial oxidation) the use of a catalyst reduces the required temperature to around 800°C – 900°C.

The choice of reforming technique depends on the sulfur content of the fuel being used. CPOX can be employed if the sulfur content is below 50 ppm. A higher sulfur content can poison the catalyst, so the TPOX procedure is used for such fuels. However, recent research shows that CPOX is possible with sulfur contents up to 400ppm.[2]

## History

1926 – Vandeveer and Parr at the University of Illinois used oxygen to replace air.[3]