A gas delivery system and method for delivering reactants such as a first gas through a first conduit and a second gas through at least one second conduit, for example, through a plurality of second conduits. The plurality of second conduits may each have a length, wherein at least a portion of the length is entirely disposed within the first conduit. In an implementation, the first conduit may deliver carbon monoxide and the one or more second conduits may deliver carbon monoxide doped with a catalyst such as iron pentacarbonyl. The first and second gases may be introduced into a reaction vessel such as a reactor chamber and used to form carbon nanotubes.

The invention relates to a process for the catalytic treatment of a hydrocarbon feedstock with continuous catalytic regeneration, in which process said feedstock is successively circulated in a plurality of reaction zones in series (R1, R2, R3, R4), the catalyst circulating as a moving bed successively in the plurality of reaction zones and flowing from the upstream end to the downstream end of each of the reaction zones and being transported by a carrier gas phase g1 from the downstream end of one reaction zone to the upstream end of the next reaction zone, characterized in that said carrier gas phase g1 has a density of greater than or equal to 1 kg/m.sup.3.

A system for reducing carbon dioxide emissions from a flue gas generated via combusting a fossil fuel is provided. The system includes a calcination chamber and a sealing-purger. The calcination chamber is configured to receive a plurality of loaded sorbent particles and a plurality of heat-transferring particles such that the loaded sorbent particles are heated within the calcination chamber so as to release carbon dioxide. The sealing-purger includes at least one gravity driven moving particle bed. The at least one gravity driven moving particle bed allows the plurality of heat-transferring particles or the plurality of sorbent particles to enter or leave the calcination chamber while restricting the flue gas from entering the calcination chamber and the released carbon dioxide particles from leaving the calcination chamber.

Compositions, methods, and reactors related to hydrogen production are generally described.

A gas delivery system and method for delivering reactants such as a first gas through a first conduit and a second gas through at least one second conduit, for example, through a plurality of second conduits. The plurality of second conduits may each have a length, wherein at least a portion of the length is entirely disposed within the first conduit. In an implementation, the first conduit may deliver carbon monoxide and the one or more second conduits may deliver carbon monoxide doped with a catalyst such as iron pentacarbonyl. The first and second gases may be introduced into a reaction vessel such as a reactor chamber and used to form carbon nanotubes.