How synthetic graphite is made

Synthetic graphite is coke baked in an electric furnace until its carbon atoms rearrange into sheets.

stations: 6
things upstream: 3
raw sources: 2
steps from the ground: 2

The short version

Synthetic graphite is made from petroleum coke and coal tar pitch. The coke is calcined, ground and mixed with pitch, shaped into blocks, and baked. The blocks are then passed through a furnace heated by electric current to above 2,100 °C, where the carbon atoms rearrange into stacked graphite layers.

Calcine the coke

Raw petroleum coke, the solid left behind when a refinery cooks heavy crude oil, is heated to drive off volatile matter. What is left is a hard, nearly pure carbon.

Goes in
Crude oil Petroleum coke
Grind and mix with pitch

Coke is milled to a controlled grain size and kneaded with hot pitch, a sticky binder from coal. The grain mix decides the strength of the finished graphite.

Goes in
Coal
Press it into blocks

Warm paste is extruded or molded into green blocks or rods. At this point they are crumbly carbon held together by pitch.
Bake the blocks

The blocks are baked slowly in a furnace for weeks, which turns the pitch into hard carbon. They are often soaked in more pitch and baked again to fill pores.
Graphitize in an electric furnace

Electric current passes straight through the blocks, which are packed in coke. They are heated above 2,100 °C, and carbon atoms shuffle into the layered graphite structure.

above 2,100 °C
Machine to size

The finished graphite is soft enough to be cut and turned on lathes. Electrodes, battery anode powder and crucibles are among the products.

End of the lineSynthetic graphite Next it goes into lithium-ion cell, lab-grown diamond.

Worth repeating

Edward Goodrich Acheson patented his process for making graphite and silicon carbide in 1896.
In 1890, Acheson tried to make diamond and ended up with blue silicon carbide crystals that he called carborundum.