Thermolysis of methane in a solar reactor for mass-production of hydrogen and carbon nano-materials

Solar thermolysis of methane to produce hydrogen and carbon nano-materials in a volumetric reactor/receiver with carbon particles cloud either priory seeded or chemically produced in the reactor, has been developed and tested. The reactor is based on absorbing of the concentrated solar radiation by the carbon particles and maintaining a reaction core at high temperature while the reactor walls are kept at relatively low temperatures, compatible with existing ceramic materials. The main advantage of the volumetric approach lies in its excellent heat transfer effectiveness and scalability to larger scales. As a result of computational fluid dynamics (CFD) analysis a compound reactor was designed and tested. The reactor's most important characteristics are: high reaction temperature, transparent window protection and directional streaming flow (tornado) without boundary layer separation. Experimentally, high temperatures (up to 1500 degrees C) in the reaction domain were achieved resulting in complete conversion of methane to hydrogen and solid carbon nano particles. Experiments were operated for periods of about 60 min with steady-state temperatures and reaction products. Organometallic catalysts were mixed together with the methane feed to produce multiwalled carbon nanotubes (MWCNT). In the catalytic experiments lower temperatures were maintained which, although resulted in lower methane conversion, enhanced the MWCNT production. (C) 2011 Elsevier Ltd. All rights reserved.