Abstract
In this work, a ceria-zirconia supported nickel catalyst (Ni/CeZrO2) was for the first time used in a fluidized bed reactor in order to obtain carbon nanotubes (CNTs) and H2 in the reaction of the decomposition of CH4. The same catalyst was afterward regenerated with H2O, which was accompanied with the production of H2. The impact of catalyst granulation, temperature, and gas hourly space velocity (GHSV) on the amount and type of carbon deposits was determined using thermogravimetric analysis (TGA) and scanning and transmission electron microscopy (SEM and TEM). The presence of randomly oriented and curved CNTs with an outer diameter of up to 64 nm was proved. The Ni/CeZrO2 particles were loosely covered with CNTs, freely dispersed over CNTs, and strongly attached to the external CNT walls. TEM proved the presence of a Ni/CeZrO2@CNT hybrid material that can be further used as catalyst, e.g., in WGS or DRM reactions. The impact of GHSV on hydrogen production during catalyst regeneration was determined. The catalyst was subjected to cyclic tests of CH4 decomposition and regeneration. According to the obtained results, Ni/CeZrO2 can be used in CH4 conversion to CNTs and H2 (instead of CH4 combustion), e.g., in the vicinity of installations that require methane utilization.
Highlights
This paper deals with the possibility of CH4 utilization for carbon nanotubes (CNTs) and H2 production in a fluidized bed reactor using a ceria-zirconia supported nickel catalyst (Ni/CeZrO2)
The Ni/CeZrO2 catalyst was used for the first time in the chemical vapor deposition (CCVD) process in a fluidized bed reactor to obtain CNTs and hydrogen from CH4
The catalyst granulation of 0.125–02 mm, T = 700 ◦C and gas hourly space velocity (GHSV) = 10,000 h−1 were found to be the optimal parameters for CH4 decomposition to CNTs and H2
Summary
This paper deals with the possibility of CH4 utilization for carbon nanotubes (CNTs) and H2 production in a fluidized bed reactor using a ceria-zirconia supported nickel catalyst (Ni/CeZrO2). The CCVD process for CNT production can be carried out in a fixed bed, a floating catalyst, and in a fluidized bed [14]. Maghsoodi et al [16] studied the continuous production of CNTs via CCVD of methane over Fe/MgO catalyst in a fluidized bed reactor. Three important aspects are raised: (i) The possibility of obtaining CNTs on Ni/CeZrO2 in a fluidized bed reactor using CH4 as the source of carbon, (ii) H2 production during that process, and (iii) the possibility of catalyst regeneration in a fluidized bed with the simultaneous production of H2. The system has been found to be active in dry methane reforming (supporting file, Figure S1)
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