Highly dispersed Ni nanoparticles encapsulated in hollow mesoporous silica spheres as an efficient catalyst for quinoline hydrogenation

Facile Synthesis of Surface-Modified Hollow-Silica (SiO2) Aerogel Particles via Oil-Water-Oil Double Emulsion Method

Due to their high surface area and low weight, silica aerogels are ideally suited for several uses, including drug delivery, catalysis, and insulation. Oil-water-oil (OWO) double emulsion is a simple and regulated technique for encasing a volatile oil phase in a silica shell to produce hollow silica (SiO2) aerogel particles by using hydrophilic and hydrophobic emulsifiers. In this study, the oil-water-oil (OWO) double emulsion method was implemented to synthesize surface-modified hollow silica (SiO2) aerogel particles in a facile and effective way. This investigation mainly focused on the influence of the N-hexane-to-water glass (OW) ratio (r) in the first emulsion, silica (water glass) content concentration (x), and surfactant concentration (s) variations. Furthermore, surface modification techniques were utilized to customize the aerogel's characteristics. The X-ray diffraction (XRD) patterns showed no imprints of impurities except SiO2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images highlight the hollow microstructure of silica particles. Zeta potential was used to determine particle size analysis of hollow silica aerogel particles. The oil-water-oil (OWO) double emulsion approach was successfully employed to synthesize surface-modified hollow silica (SiO2) aerogel particles, providing precise control over the particle characteristics. By the influence of the optimization condition, this approach improves the aerogel's potential applications in drug delivery, catalysis, and insulation by enabling surface modifications.

A One-Pot Hydrothermal Preparation of High Loading Ni/La2O3 Catalyst for Efficient Hydrogenation of Cinnamaldehyde

It is a challenging task for selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) without additional by-product formation. In this work, a La2O3 supported high Ni content nanoparticle catalyst was prepared for CAL selective hydrogenation. Meanwhile, Co-La2O3 catalysts were used as a reference catalyst. XRD, TEM, STEM-HAADF, XPS, and H2-TPR measurements were used to investigate the physicochemical properties of Ni-La2O3 catalysts. The experimental results confirmed that the CAL conversion and HCAL selectivity were effectively promoted with the increase of Ni loading amounts. At a Ni/La molar ratio of four, a high HCAL selectivity of 87.4% was obtained at a CAL conversion of 88.1% under mild reaction conditions. The catalyst was recycled five times without activity loss. Combined with various characterizations, it could be inferred that the good hydrogen adsorption and dissociation capacity of Ni and the presence of a certain amount of oxygen vacancies on the La2O3 support have a positive effect on the improvement of HCAL selectivity. This work provided an effective path to design transition-metal-based supported oxide catalyst for the cinnamaldehyde hydrogenation to hydrocinnamaldehyde.

Nickel Catalysts on Carbon-Mineral Sapropel-Based Supports for Liquid-Phase Hydrogenation of Nitrobenzene

Nickel catalysts with carbon-mineral supports derived from sapropel were synthesized; the effect exerted by the nature of the support (type of the initial sapropel) and active component precursor on the activity of the catalysts in the model reaction of liquid-phase nitrobenzene hydrogenation was studied. The catalysts, synthesized using the support with a smaller fraction of carbon, were more active irrespective of the precursor nature. The highest activity was observed for the catalysts synthesized from nickel nitrate and formate; nitrobenzene conversion was 65% and 51%, respectively, after 1 h of reaction. The catalysts retained high activity after six reaction cycles at 100% aniline selectivity. The presence of sulfur in the nickel precursor deteriorated the catalytic activity (convection less than 3%) due to formation of the sulfide phase.