Introduction to Hydroxyapatite‐based Materials in Heterogeneous Catalysis

Advanced Nickel-Based Catalytic Materials on Hydroxyapatite: Effect of the Metal Particle Size on Tri-reforming of Methane

“…This can be due to some residual ethanol and water physisorbed on hydroxyapatite, even after the catalyst drying process. After this initial mass loss, all the samples behave in a similar way, exhibiting mass losses of 3.5–3.7% between 300 and 900 °C, in analogy to other HAP-based materials described in the literature . All of the as-prepared materials were thermally stable at the working temperature of TRM (800–850 °C, Figure a).…”

“…Despite the reversible loss of hydroxyl groups in HAP having been described to take place in a large range of temperatures along the thermal treatment, TRM operating conditions in the presence of steam can help preserve the apatite structure via rehydration. 32 The reducibility of the as-prepared catalytic materials was studied by temperature-programmed reduction (TPR, Figure 2b). The catalysts prepared by the impregnation method showed similar behavior, observing a signal with two main peaks at 388 and 411 °C for 10 wt % Ni loading (10Ni@ HAP_IWI), and 381 and 402 °C for 5 wt % Ni loading (5Ni@ HAP_IWI) (see deconvolution analysis in Figure S12 in the Supporting Information), typical for NiO reduction slightly interacting with the support.…”

Hydroxyapatite: A Matrix for Metal Exsolution Leading to Highly Dispersed Catalytically Active Species

“…Its specific surface area is higher than that of perovskites, , while its thermal and chemical stabilities are generally better than those of zeolites and metal–organic frameworks. ,, Its intrinsic surface acid–base properties can easily be tuned by varying its Ca/P ratio, − and its framework Ca 2+ cations can be substituted by catalytically active metals (Cu 2+ , Ni 2+ , Ag + , etc. ). ,, This leads to multifunctional catalysts suitable for a wide range of applications. ,, Through surface cation deposition in the excess of solution or strong electrostatic adsorption (SEA), at substituent metal contents of 1–2 wt %, it is possible to obtain HAp catalysts with atomically dispersed active sites showing a particularly high catalytic performance and an exceptional resistance to sintering under harsh reaction conditions. − …”

“…1,3,15 This leads to multifunctional catalysts suitable for a wide range of applications. 1,3,5 Through surface cation deposition in the excess of solution or strong electrostatic adsorption (SEA), at substituent metal contents of 1−2 wt %, it is possible to obtain HAp catalysts with atomically dispersed active sites showing a particularly high catalytic performance and an exceptional resistance to sintering under harsh reaction conditions. 16−18 In the present work, for the first time, to our knowledge, we demonstrate that such highly valuable HAp-based catalysts with highly dispersed active sites can actually be obtained through an advantageous novel bottom-up approach.…”

“…Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 or HAp) is a biocompatible and ecological material. As the main mineral component of bones and teeth, it can be obtained from natural sources, or it can be synthesized in mild conditions from cheap precursors. − Besides playing an important role in many clinical applications such as drug design and bone tissue regeneration, it has proved to be efficient as a support and (co)­active phase in heterogeneous catalysis. ,,− It has important advantages over other materials used in the latter field. Its specific surface area is higher than that of perovskites, , while its thermal and chemical stabilities are generally better than those of zeolites and metal–organic frameworks. ,, Its intrinsic surface acid–base properties can easily be tuned by varying its Ca/P ratio, − and its framework Ca 2+ cations can be substituted by catalytically active metals (Cu 2+ , Ni 2+ , Ag + , etc.…”