Nickel Nanoparticles Immobilized on Pristine Halloysite: An Outstanding Catalyst for Hydrogenation Processes

Abstract

Nickel nanoparticles (NiNPs) immobilized on halloysite-based supports were straightforwardly synthesized and fully characterized by different techniques with the purpose of evaluating the catalytic performance of these as-prepared composite materials as catalysts in hydrogenation reactions. Thus, halloysite bearing amino (HAL-NH 2 ) and ammonium (HAL-NEt 3 ) groups led to less active catalytic materials in comparison with unfunctionalized halloysite supports, probably due to relative strong metal-support interactions with amino and tetraalkylammonium functions, consequently hindering the interaction of unsaturated substrates at the surface of the catalytic material.Despite NiNPs supported on pristine halloysite provided merely agglomerates, NiNPs stabilized by quinidine on unfunctionalized halloysite (NiC) proved to be a highly effective and versatile catalyst operating at relative low temperature (25-100 °C) and metal loading (1-20 mol %Ni), very well-adapted to reduce a large range of functions (alkenes, alkynes, ketones, aldehydes, nitro…). Moreover, NiC was able to selectively reduce substrates from biomass to yield high value-added products, such as squalane, saturated fatty acids, furfuryl alcohol and γ-valerolactone.

Selective Catalytic Hydrogenation of Fatty Acids with Cobalt–Halloysite Nanocomposites for Waste Valorization

“…As observed by TEM analyses, the presence of quinidine afforded small nanoparticles uniformly distributed on the halloysite (3.2 ± 0.9 nm; dispersion of 23%, see the Supporting Information for the dispersion determination) ( CoA , Figure a), in agreement with our previous contributions involving metal nanoparticles. − However, in the presence of PEG-DME, nonuniformly distributed nanoparticles on the support were obtained ( CoB ) with sizes ranging between 13 and 30 nm, evidencing that PEG-DME (average MW average 240 g/mol) was not a suitable stabilizer (Figure b). Furthermore, it is worth mentioning that molecular hydrogen was not able to reduce Co­(OAc) 2 .…”

“…With the aim of efficiently immobilizing cobalt nanoparticles (CoNPs) on halloysite-based supports, different materials were prepared using both unfunctionalized and ammonium-functionalized halloysite; the latter was prepared following our previous reported methodology (Figure 1). 31 Using the pristine clay, three approaches were envisaged taking into account the influence of the metal precursor [Co 2 (CO) 8 , Co(OAc) 2 ] and the nature of both the stabilizing agent [quinidine, polyethyleneglycol dimethylether (PEG-DME)] and the reducing agent (H 2 , NaBH 4 ). In order to study the influence of the two stabilizers in the synthesis of CoC and thus to compare the catalytic behavior with CoA and CoB (see below Co-catalyzed hydrogenation discussion), we added QD and PEG-DME in two independent controls using Co(OAc) 2 as a metallic precursor.…”

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

“…The reaction conditions (feedstock composition) were calculated to obtain a theoretical H 2 /CO ratio of ca. 1.8, which is a suitable ratio for downstream hydroaminomethylation 42 and Fischer−Tropsch processes. 43 The performance of the catalysts was evaluated with regard to the CH 4 and CO 2 conversions.…”

“…The design of nickel nanocatalysts exhibiting high surface areas and enhanced reactivity profiles arising from low-coordination sites due to structural defects, and synergistic effects between metal–support interfaces, represents an innovative strategy toward the kinetic stabilization of small nanoparticles that has been widely applied by our group for zero-valent Ni systems immobilized both in a liquid phase (glycerol) and on solid supports (MgAl 2 O 4 , TiO 2 , halloysite).…”

A general and robust Ni-based nanocatalyst for selective hydrogenation reactions at low temperature and pressure

“…Furthermore, it exhibits a limited substrate scope, and sensitive functional groups are not tolerated. To solve these problems, in recent years, many non-noble metal-based heterogeneous catalysts based on Ni (10)(11)(12)(13)(14)(15)(16)(17)(18)(19), Co (20)(21)(22), Fe (23)(24)(25)(26)(27), and Cu (28)(29)(30) have been developed for the hydrogenation of nitroarenes, carbonyl compounds, nitriles, N-heterocycles, and unsaturated carbon─carbon bonds. However, most of these materials require higher temperature or pressure of hydrogen, which obviously limits practical applications.…”