In ATR, a hydrocarbon feedstock, such as methane, reacts with both oxygen (O2) and steam (H2O) over a catalyst. The process is carried out in a single reactor where the exothermic partial oxidation reaction: \[ \text{CH}_4 + \frac{1}{2}\text{O}_2 \rightarrow \text{CO} + 2\text{H}_2 \] is balanced by the endothermic steam reforming reaction: \[ \text{CH}_4 + \text{H}_2\text{O} \rightarrow \text{CO} + 3\text{H}_2 \]
