A thermal study on NiAl-citrate LDH as catalyst precursor for dry reforming reaction

Abstract

Ni-based layered double hydroxides (LDHs) are well-known as catalysts precursors; in fact, their properties allow for a homogeneous distribution of Ni on a matrix through simple and economic synthetic passages. In this work, NiAl-citrate LDH was synthetized through a recently developed synthetic pathway that led to the formation of almost single-layered hexagonal nanocrystals. These ones seem to be promising for the production of a Ni (0)-based material with a very high surface area, since through pyrolysis, the interlayered citrate could be turned into CO that simultaneously reduces the Ni (II) to Ni (0) and blow-up the original crystals. In this transformation, temperature plays a key role; therefore, the processes occurring during heating were investigated to discriminate which of them contribute to the material reduction. Additionally, the appropriate pyrolysis temperature was determined to achieve the desired compound that was a homogeneous distribution of nanopatterned micro-flakes of Ni (0) and Al/Ni mixed oxides, with a high specific surface area (177m²g⁻¹). The high surface area and the expected properties of this new material make it an interesting candidate for heterogeneous catalysis of high-temperature gas reactions, such as dry reforming, a noteworthy process that produces syngas from the two greenhouse gases CO₂ and CH₄. DRM applicability is limited by high temperatures required to obtain acceptable conversion and by solid carbon deposition on catalyst, both leading to its deactivation over time; so, it is important to develop new catalysts able to overcome those problems. For these purposes, some preliminary tests on the obtained material were performed confirming its catalytic behavior for the DRM, especially at temperatures > 800 K.