In both Elite Dangerous Horizons and Elite Dangerous Odyssey, you will have access to a materials trade that is able to trade materials for other materials.

In Horizons, not all stations will have a materials trader and not all traders will be trading the same type of materials. 

In Odyssey, stations that feature a concourse will have a bartender that will only trade assets and exchange goods and data for credits.

A materials trader will trade a single type of material, they trade either Encoded, Manufactured, or Raw materials only.

Bartenders can be found in the main lounge area of a station's concourse.

A Bartender's job is to trade assets, which consists of Technology, Circuits and Chemicals, and exchange goods and assets for credits.