In Search of Factors Determining Activity of Co3O4 Nanoparticles Dispersed in Partially Exfoliated Montmorillonite Structure

Abstract

The paper discusses a formation of Mt–PAA composite containing a natural montmorillonite structure partially exfoliated by poly(acrylic acid) introduced through intercalation polymerization of acrylic acid. Mt–PAA was subsequently modified by controlled adsorption of Co2+ ions. The presence of aluminosilicate packets (clay) and carboxyl groups (hydrogel) led to the deposition of significant amounts of Co2+ ions, which after calcination formed the Co3O4 spinel particles. The conditions of the Co2+ ions’ deposition (pH, volume and concentration of Co(NO3)2 solution, as well as a type of pH-controlling agent) were widely varied. Physicochemical characterization of the prepared materials (including X-ray fluorescence (XRF), X-ray powder diffraction (XRD), low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H2-TPR)) revealed that the modification conditions strongly influenced the content as well as the distribution of the Co3O4 active phase, tuning its reducibility. The latter parameter was, in turn, very important from the point of view of catalytic activity in the combustion of aromatic volatile organic compounds (VOCs) following the Mars–van Krevelen mechanism.

On the effect of metal loading on the performance of Co catalysts supported on mixed MgO–La2O3 oxides for ammonia synthesis

“…Some of their limitations, such as the low activity in the high conversion region for the former and high price and high requirements for the purity of synthesis gas for the latter, cause that research is still ongoing to develop alternative catalysts. Recently, cobalt catalysts that are used in many catalytic reactions [35][36][37][38][39][40][41][42] are getting more attention for their use in ammonia synthesis owing to their relatively high activity and stability. [43][44][45][46][47][48][49] Cobalt-based catalysts are commonly used with the support materials.…”

Design of Co3O4@SiO2 Nanorattles for Catalytic Toluene Combustion Based on Bottom-Up Strategy Involving Spherical Poly(styrene-co-acrylic Acid) Template

“…A compromise solution is therefore to use transition metal oxides which combine the benefits of low manufacturing costs with relatively high efficiency and enhanced resistance to deactivation. The final performance of these catalysts is influenced by various factors, including properties of active components, dispersion of the active phase, and size and morphology of grains [1][2][3][4][5]. Co 3 O 4 , CuO, MnO x , Fe 2 O 3 and NiO are the most common oxide systems used in the combustion of VOCs.…”

“…As in the case of noble metals, the involvement of a support also has a positive effect on dispersion and thermal stability of the catalytically active phase. The selection of the appropriate material forming the support depends on many factors (including its porosity, chemical activity and strength of interaction with the active phase), but a typical choice is γ-Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 , CeO 2 and zeolites [1,5,6]. Mixed systems containing at least two transition or noble metals in their structure have also been increasingly studied.…”