Case Studies in Chemical and Environmental Engineering (Dec 2023)
Experimental study of the production of composite particles of Co3O4/aluminum oxides in the processes of sub- and supercritical water oxidation
Abstract
This work presents experimental studies for obtaining composite particles of Co3O4/aluminium oxides. The dependences of the influence of process temperature and time on the phase composition, adsorption properties, morphology, and dispersion composition of particles are revealed. Experimental studies were carried out in the temperature range T = 350–410 °C and time τ = 180–420 min. It has been revealed that metallic aluminium, depending on temperature and time, transforms into the forms γ−Al2O3,χ−Al2O3andα−Al2O3 in the processes of sub- and supercritical aqueous oxidation. Due to a rapid decrease in pressure and temperature to atmospheric values, nano-sized cobalt oxide particles are formed from a supercritical water solution, which are deposited on the porous aluminum oxide particle surface. The results obtained on an scanning electron microscopy (SEM) with an energy-dispersive spectrometer indicate the deposition of cobalt oxide nanoparticles on the aluminium oxide surface and the formation of composite particles.The abilities of water under sub- and supercritical conditions, such as high mass transfer characteristics, low dielectric constant, manifestation of catalytic properties and high diffusion rates, allow dissolved metal oxides to penetrate and precipitate in matrices with micro-, sub-micro and nano-sized pores. This proposed method in this work makes it possible to obtain composite particles with uniform impregnation of the entire porous matrix surface, with the given composition and given physical and chemical properties. The influence of thermodynamic parameters on the properties of sub- and supercritical water can be controlled by the composite particle characteristics.Thus, this method makes it possible to obtain composite particles in one stage. It is alternative method to traditional ones, that allows to avoid the use of organic solvents, high temperatures and additional stages of preparation and processing of materials.
