Influence of atomic structure on the nano-nickel-based catalyst activity produced by solution combustion synthesis in the hydrogenation of maleic acid

Effects of Precursor Concentration in Solvent and Nanomaterials Room Temperature Aging on the Growth Morphology and Surface Characteristics of Ni–NiO Nanocatalysts Produced by Dendrites Combustion during SCS

The morphology and surface characteristics of SCS(Solution Combustion Synthesis)-derived Ni–NiO nanocatalysts were studied. The ΤΕΜ results highlighted that the nanomaterial’s microstructure was modified by changing the reactants’ concentrations. The dendrites’ growth conditions were the main factors responsible for the observed changes in the nanomaterials’ crystallite size. Infrared camera measurements demonstrated a new type of combustion through dendrites. The XPS analysis revealed that the NiO structure resulted in the bridging of the oxygen structure that acted as an inhibitor of hydrogen adsorption on the catalytic surface and, consequently, the activity reduction. The RF-IGC indicated three different kinds of active sites with different energies of adsorption on the fresh catalyst and only one type on the aged catalyst. Aging of the nanomaterial was associated with changes in the microstructure of its surface by a gradual change in the chemical composition of the active centers.

Influence of Various Parameters on the SCS Ni/NiO Nanostructures and their Mechanism of Formation

Solution combustion synthesis (SCS) is an efficient approach to deliver materials with desirable properties directly in the nanoscale. Nevertheless, it is a very sensitive method and there are many parameters that influence the final materials’ properties and microstructure. In this work, four parameters that severely affect the combustion mechanism of formation for the final products, and as a result their final properties, are studied. These are the concentration of nitrates, the concentration of fuel in direct and slow heating and the time in furnace after the SCS is completed. It has been concluded that all these parameters affect the SCS process in a complicated way and an attempt has been made to explain the underlying mechanisms and processes that shape the final nanostructures. Finally, some of the as-synthesized Ni/NiO nanopowders were employed as catalysts and their activity was tested in the liquid-phase hydrogenation of maleic acid.

The Effect of the Precursor Solution’s Pretreatment on the Properties and Microstructure of the SCS Final Nanomaterials

Nanostructured nickel-based catalysts were produced by solution combustion synthesis and it was found that their properties and structure depended on the pretreatment of the precursor solution. X-ray diffraction, N2 adsorption, and an infrared high-speed camera were used to follow the various synthesis steps and to characterize the obtained catalysts, while their catalytic activity was determined in the hydrogenation of maleic acid. It was determined that the amount of water used and the heating of the precursor solution under mild stirring up to 70 °C influenced the nickel nitrate–glycine–water complexes that were formed in the precursor solution in the form of dendrites. These play a key role in the solution combustion synthesis (SCS) reaction mechanism and in particular in the formation of nickel-based catalysts. Understanding the interrelationships between the processing parameters and the ensuing powder properties allowed an efficient optimization of the catalytic performance.

Structure and surface characteristics of Fe-promoted Ni/Al2O3 catalysts for hydrogenation of 1,4-butynediol to 1,4-butenediol in a slurry-bed reactor

Nanostructured Ni–xFe/Al₂O₃ catalysts prepared by sol–gel combustion synthesis (SGC) display superior activity in hydrogenation of 1,4-butynediol to 1,4-butenediol. The Fe addition promoted the Ni reducibility and stabilized the Al₂O₃ structure.

Highly dispersed Ni nanoparticles on mesoporous silica nanospheres by melt infiltration for transfer hydrogenation of aryl ketones

Nickel-based catalysts have been applied to the catalytic reactions for transfer hydrogenation of aryl ketones.