Re: What processes are used in breaking methane into carbon and hydrogen?

Very high temperatures (over 1000 degrees Celsius) are required in order 
methane to be broken down to carbon and hydrogen. Furthermore, one would 
need a special reactor for this purpose. Taking into account that the 
construction of such reactor is not a trivial task and that it is quite 
difficult to reach the required high temperature, I suggest that it would 
not be feasible at all to do this in your home lab.
Also, you should not forget that methane is highly explosive when mixed 
with air!

The thermal decomposition of methane is also known as "pyrolysis". 
Actually this is a complex chemical process, in which the initial step is 
formation of acetylene:

2CH4 ---> C2H2 + 3H2

The acetylene then decomposes to carbon and hydrogen:

C2H2 ---> 2C + H2


The pyrolysis of methane is sometimes used for the industrial production 
of acetylene.

Moderator's note:
-----------------
A lower-temperature reaction, using steam and a catalyst, is used to convert 
methane into a mixture of hydrogen and carbon monoxide. This mixture is 
called "synthesis gas" or "syngas" for short, and is used as a raw material for 
a number of industrial chemicals, including methanol.