[melaniejs (OP)]

Matt, who listened to the show on the radio, asks on twitter:

You mentioned about the use of cobalt in batteries, but is cobalt also used in the process of producing unleaded petrol?

Anyone know?

[chiralSPO]

It depends how the petrol is being made. I am unaware of cobalt being used in the traditional methods of converting petroleum into petrol (though it may be).

However, there are some methods for manufacturing hydrocarbon fuels from other feedstocks (carbon monoxide and hydrogen, or carbon dioxide and water, or carbon-rich compounds which can be reacted to form these small molecule precursors...) The Fischer-Tropsch process (https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process), for instance often uses cobalt catalysts. NOTE: cobalt is not used as a component of the petrol in this case, it is just used as a component of the machinery that manufactures it.

I am aware of iron compounds (such as ferrocene and iron carbonyls) being used as anti-knocking agents in non-leaded petrol. The cobalt analogs of these might also do the job, but cobaltocene and cobalt carbonyls are much more reactive than ferrocene and iron carbonyls, and cobalt is about 50x as expensive as iron...

[Bored chemist]

The usual catalysts used in making gasoline by catalytic cracking are zeolites rather than metals.
https://en.wikipedia.org/wiki/Fluid_catalytic_cracking

There will be cobalt in some of the alloy steels used in the equipment.

[colinpowell]

Cobalt is used now in the production of unleaded petrol. Far less is used in battery technology.