Method and system for pyrolysis and carbon deposition

A method of sequential pyrolysis and carbon deposition to produce a composite carbonaceous product, the method comprising:

• a pyrolysis process step comprising pyrolyzing a pyrolyzable organic feed at a pyrolysis temperature in a first reaction zone in the presence of a non-oxidising gas to produce hot char and pyrolysis gas, wherein the pyrolysis gas and the non-oxidising gas combine to form a gas mixture;
• discharging the gas mixture from the first reaction zone to a combustion zone and combusting at least a portion of the pyrolysis gas therein, wherein heat produced by the combusting of the pyrolysis gas is transmitted from the combustion zone to the first reaction zone to provide at least a portion of the heat of pyrolysis;
• and
• a decomposition process step comprising contacting a hydrocarbon-rich organic gas with the hot char directly after its production in the pyrolysis process step, wherein the hydrocarbon-rich organic gas catalytically decomposes on the hot char at a decomposition temperature which is higher than the pyrolysis temperature, thereby producing gaseous decomposition products comprising hydrogen and a composite carbonaceous material comprising the char with carbon deposits thereon,
• the carbon deposits comprising carbon nanomaterials,
• wherein the hot char remains continuously at temperatures of above 300° C. between its production in the pyrolysis process step and the catalytic decomposing of the hydrocarbon-rich organic gas thereon in the decomposition process step, and
• wherein at least 90% of the hydrocarbon-rich organic gas is provided from a source external to the pyrolysis process step where the hot char is produced.