Microwave chemical processing

A method comprising:

• supplying pulsed microwave radiation through a waveguide having a length, the microwave radiation propagating in a direction along the waveguide;
• providing a supply gas into the waveguide at a first location along the length of the waveguide, a majority of the supply gas flowing in the direction of the microwave radiation propagation;
• generating a plasma in the supply gas in at least a portion of the length of the waveguide;
• adding a process gas into the waveguide at a second location downstream from the first location, a majority of the process gas flowing in the direction of the microwave propagation at a flow rate of greater than 5 slm;
• and
• controlling an average energy of the plasma to convert the process gas into separated components by controlling at least one of the group consisting of:
• a pulsing frequency of the pulsed microwave radiation, wherein the pulsing frequency is greater than 500 Hz;
• and
• a duty cycle of the pulsed microwave radiation, wherein the duty cycle is less than 90%;
• wherein a pressure within the waveguide is at least 0.1 atmosphere, and
• wherein the process gas is methane, and the separated components comprise hydrogen and a nanoparticulate carbon.