Effect of the synthesis conditions of Ni/Al2O3 catalysts on the biogas decomposition to produce H2-rich gas and carbon nanofibers
Abstract The utilization of biogas as carbon source for the co-production of filamentous-like materials and syngas is proposed. Catalysts with different Ni:Al molar ratios, Al 2 O 3 supports and preparation methods were synthesized. The suitability of the catalysts was analyzed considering activity, stability and carbon yield. Catalysts showed a good performance and similar results according to syngas compositions were obtained. However, some differences related to stability over time and carbon yields were detected. TPR analysis and TEM micrographs of the fresh catalysts revealed the presence of two different Ni particles: large Ni particles with low metal support interaction (MSI) that favoured the formation of encapsulating carbon and small Ni particles inserted in the Al 2 O 3 structure with a greater MSI that lead to nanofilamentous carbons formation. Generally both kinds of Ni particles were observed in all catalysts, however their relative abundance was dramatically affected by the Al 2 O 3 employed, the preparation method and the Ni:Al molar ratio.
H2-rich gases production from Catalytic Decomposition of Biogas: Viability of the process associated to the co-production of carbon nanofibers
Abstract The exploitation of biogas for different applications such as the production of hydrogen, syngas or bio-methane appears as an interesting option to valorise this renewable source. However, these processes are energetically penalized and have to offer an extra added value to become economically attractive. In this context, the Catalytic Decomposition of Biogas (CDB) has been recently proposed as a potential alternative to be considered for biogas valorization. In this process, syngas (H 2 and CO) and valuable carbon nanofibers (CNFs) are simultaneously generated. The know-how obtained in previous studies allowed us to select the optimum experimental conditions to simulate the implementation of a CDB continuous process using a fluidized bed reactor. The process consisted in a cyclic operation, by which after the completion of the each run, carbonaceous material produced (containing ca. 6% of catalysts) was withdrawn from the reactor, and the required amount of fresh catalyst to keep catalyst inventory constant was added to the reactor. Characterization of carbonaceous material carried out by several techniques revealed the prevalence of fishbone-like CNF with very interesting textural and structural properties. Mass and energy balances carried out pointed out that the viability of the CDB process depends on the co-production of valuable CNFs that can be used in different applications.
Catalytic growth of single-walled carbon nanotubes with a narrow distribution of diameters over Fe nanoparticles prepared in situ by the reduction of LaFeO3
Abstract Bundles of single-walled carbon nanotubes (SWNTs) with a narrower distribution of diameter have been produced by catalytic decomposition of methane at 1010 °C on a newly developed catalyst LaFeO 3 . The SWNTs were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The diameter of the SWNTs is in the range of 0.8–1.8 nm. This result shows for the first time that SWNTs could be produced by catalytic decomposition of hydrocarbons without Al 2 O 3 , or SiO 2 or MgO support.