Pyrolysis gasoline hydrogenation is a complex process involving several reactions. It's not possible to represent it with a single reaction equation.

Here's a simplified explanation and a general representation:

What happens:

Pyrolysis gasoline, a product of cracking hydrocarbons at high temperatures, contains various unsaturated compounds like olefins, diolefins, and aromatics. Hydrogenation aims to saturate these unsaturated compounds by adding hydrogen.

General Reaction:

```

C<sub>n</sub>H<sub>m</sub> (unsaturated compounds) + H<sub>2</sub> → C<sub>n</sub>H<sub>m+2</sub> (saturated compounds)

```

Specific Examples:

* Olefin hydrogenation:

* CH₂=CH₂ (ethylene) + H₂ → CH₃-CH₃ (ethane)

* Diolefin hydrogenation:

* CH₂=CH-CH=CH₂ (butadiene) + 2H₂ → CH₃-CH₂-CH₂-CH₃ (butane)

* Aromatic hydrogenation:

* C₆H₆ (benzene) + 3H₂ → C₆H₁₂ (cyclohexane)

Key Points:

* The actual reaction mixture in pyrolysis gasoline is much more complex than these examples. It contains numerous compounds with different degrees of unsaturation.

* The specific catalysts used and reaction conditions (temperature, pressure, etc.) influence the selectivity of the hydrogenation process.

* The goal is to produce a high-quality gasoline blendstock with improved octane number and reduced environmental impact.

Therefore, it's important to remember that the overall reaction is a complex mixture of various hydrogenation reactions happening simultaneously.