Thermocatalytic Decomposition of Methane in a Fluidized Bed Reactor: Proof of Concept

Thermocatalytic decomposition of methane (TCD) into functional-carbon and hydrogen requires optimal design of the reactor and the process. To facilitate this, the particle growth needs to be characterized and understood by means of conducting kinetic measurements and modeling of the heat and mass transfer and catalytic reaction at the particle and reactor scale.

TCD was studied in a lab-scale fluidized bed reactor to assess the effect of reactor parameters (such as temperature, concentration, particle size and space velocity) and investigate the effect of the increasing particles size and mass during reaction on the fluidization and finally to derive a kinetic model for the reaction and deactivation of the catalyst. A commercial nickel catalyst supported on silica was used in our kinetic experiments. The performance of the catalyst was evaluated and values up to and higher than 70 g of functional Carbon NanoFibers (CNFs) per gram of catalyst was produced. The fluidization regime was changed from a turbulent regime with the fresh catalyst to the minimum fluidization regime with the grown catalyst particles. The extent of particle growth and fluidization regime is dependent on operating conditions and time.

In the fluidized bed reactors, the scale of the effective phenomena can vary from; the mass and heat transfer within a single porous particle, the chemical reaction leading to particle growth to the interactions of particles with each other or with the fluid. Computational Fluid Dynamics – Discrete Element Method (CFD-DEM) is coupled with the Multi-Grain Model (MGM) to capture all these effects and enables us to study dense gas-particle flows in combination with coupled mass and heat transfer and catalytic reactions in growing particles. The obtained knowledge from this study will be used to study the TCD and to bring the industrial scale TCD in gas-fluidized beds one step closer to reality.