Shape-Controlled CeO₂ Nanoparticles: Stability and Activity in the Catalyzed HCl Oxidation Reaction

Abstract

CeO 2 is a promising catalyst for the HCl oxidation (Deacon process) in order to recover Cl 2 . Employing shape-controlled CeO 2 nanoparticles (cubes, octahedrons, rods) with facets of preferential orientations ((100), ( 111), ( 110)), we studied the activity and stability under two reaction conditions (harsh: Ar:HCl:O 2 = 6:2:2 and mild: Ar:HCl:O 2 = 7:1:2). It turns out that both activity and stability are structuresensitive. In terms of space time yield (STY), the rods are the most active particles, followed by the cubes and finally the octahedrons. This very same trend is reconciled with the complete oxygen storage capacity (OSCc), indicating a correlation between the observed activity STY and the OSCc. The apparent activation energies are about 50 kJ/mol for cubes and rods, while the octahedrons reveal an apparent activation energy of 65 kJ/mol. The reaction order in O 2 is positive (0.26−0.32). Under mild reaction conditions, all three morphologies are stable, consistent with corresponding studies of CeO 2 powders and CeO 2 nanofibers. Under harsh reaction conditions, however, cubes and octahedrons are both instable, forming hydrated CeCl 3 , while rods are still stable. The present stability and activity experiments in the catalytic HCl oxidation reaction over shape-controlled CeO 2 nanoparticles may serve as benchmarks for future ab initio studies of the catalyzed HCl oxidation reaction over well-defined CeO 2 surfaces.

Electrospinning of CeO2 nanoparticle dispersions into mesoporous fibers: on the interplay of stability and activity in the HCl oxidation reaction

“…However, the XRD patterns showed almost no changes even under harsh conditions. Recent insights on shape-controlled CeO 2 nanoparticles used in the HCl oxidation reaction 20 showed that rod-like particles with (110)-orientation are quite active and do not show CeCl 3 formation, similar to the CeO 2 nanoparticles in the present study. Furthermore, pure CeO 2 nanoparticles show stable performance in the HCl oxidation reaction in the presence of water.…”

“…Furthermore, it is interesting to note that both, rods with (110) orientation as well as small nanoparticles do not show CeCl 3 in XRD experiments and are, thus, surprisingly stable against chlorination. 20 The comparably small decay in STY aer 60 h is in agreement with the absence of substantial amounts of CeCl 3 , in that the chlorination of CeO 2 is directly related to inactivation of CeO 2 in the HCl oxidation reaction. 27 Such stable STY values under highly corrosive conditions for two types of pure CeO 2 nanomaterials, the 6 nm-particles in the present study as well as the preferentially oriented rods (ca.…”

“…In addition, the STY and OSC/OSCc were studied on nanoscopic shape-controlled CeO 2 nanoparticles (rods, cubes, octahedrons), with respect to the HCl oxidation reaction. 20 We showed that the rods are the most active particles, followed by the cubes and the octahedrons. The same trend holds true for the complete oxygen storage capacity (OSCc), suggesting a correlation between the observed STY and the OSCc.…”

“…Degradation of the CeO 2 catalysts' brous structure during HCl oxidation can be linked to the transformation of cerium dioxide into the trichloride. 20 However, the XRD patterns of the particle-based bers measured aer the Deacon reaction exhibit no discernible reections attributable to cerium chlorides (Fig. 4, bottom), even under "harsh" conditions.…”

Synthesis of CeO2 nanoparticles with different morphologies and their properties as peroxidase mimic

“…Due to the valence of cerium element can be reciprocally transformed in trivalent and tetravalent, CeO 2 nanoparticles can act as catalysts in many reactions, such as photodegradation of organic pollutants, water splitting, oxidation reduction reaction in organic synthesis . Meanwhile, both surface oxygen and lattice oxygen show oxidation in CeO 2 nanoparticles.…”