Catalytic decomposition of methane-rich hydrocarbons in high hydrogen content gases and nanofilamentous carbon

The Fuel Conversion Group (FCG) has been a pioneer in the development of various processes based on the catalytic decomposition of hydrocarbons. This line of research is motivated by the need for our society to reduce CO2 emissions by gradually replacing fossil fuels by a hydrogen-based economy.

Our research group has worked on a novel process for hydrogen production named Catalytic Decomposition of Methane (CDM), which represents a very promising alternative to steam methane reforming, the most widespread method used industrially for the production of hydrogen. The CDM is a reaction in which methane (the main component of natural gas) is decomposed into free-CO2 hydrogen and nanostructured carbon with high added value in the form of carbon nanofibers (CNF) or carbon nanotubes (CNT), by using supported catalysts based on Group 8 metals (Ni, Co and Fe). The gas stream produced consists of a mixture of hydrogen and unreacted methane, which can be used directly to power a combustion engine, or being subjected to a separation process to obtain pure hydrogen which can be subsequently fed to a fuel cell. Moreover, the generated carbon materials have multiple applications such as additives for composites, catalyst support or energy conversion systems (anodes in Li ion batteries and ion Na).

In the last years, the FCG has developed a new process based on the use of biogas for the simultaneous production of synthesis gas and carbon nanofibers, known as Catalytic Decomposition of Biogas (DCB). This process is presented as a very interesting alternative to biogas combustion for energy production. Because of its composition, biogas is considered as an ideal raw material for the dry reforming of CH4. However, biogas presents CH4:CO2 ratios higher than 1, which favors carbon deposition that can eventually produce catalyst deactivation. Based on the previous experience of the FCG in DCM, we have applied the same concept to biogas showing the possibility of promoting the formation of carbon in the form of nanofibers with high added value while avoiding catalysts deactivation, together with a gas synthesis with a ratio H2: CO close to 1.5.

By using both DCM and DCB processes, and by a careful selection of catalysts and operating conditions, it is possible to obtain a la carte a variety of nanostructured carbon, including fishbone-like carbon nanofibers, parallel-type carbon nanofiber, multiwall carbon nanotubes and chain-like carbon nanotubes. In addition, our group has the technology necessary to produce these carbon materials in relatively large quantities (on the order of hundreds of grams), thanks to the development of fluidized and rotary bed reactors at semi-pilot scale.

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Relevant publications:

Pinilla JL, Moliner R, Suelves I, Lázaro MJ, Echegoyen Y, Palacios JM. Production of hydrogen and carbon nanofibers by thermal decomposition of methane using metal catalysts in a fluidized bed reactor. Int J Hydrog Energy. 2007;32:4821-9.

Pinilla JL, Suelves I, Lázaro MJ, Moliner R, Palacios JM. Influence of nickel crystal domain size on the behaviour of Ni and NiCu catalysts for the methane decomposition reaction. Appl Catal A. 2009;363:199-207.

de Llobet S, Pinilla JL, Moliner R, Suelves I, Arroyo J, Moreno F, et al. Catalytic decomposition of biogas to produce hydrogen rich fuels for SI engines and valuable nanocarbons. Int J Hydrog Energy. 2013;38:15084-91.

de Llobet S, Pinilla JL, Moliner R, Suelves I. Effect of the synthesis conditions of Ni/Al2O3 catalysts on the biogas decomposition to produce H2-rich gas and carbon nanofibers. Appl Catal B. 2015;165:457-65.