Evidences of the Cerium Oxide-Catalysed DPF Regeneration in a Real Diesel Engine Exhaust

The active phase Ce0.5Pr0.5O2 has been loaded on commercial substrates (SiC DPF and cordierite honeycomb monolith) to perform DPF regeneration experiments in the exhaust of a diesel engine. Also, a powder sample has been prepared to carry out soot combustion experiments at laboratory. Experiments performed in the real diesel exhaust demonstrated the catalytic activity of the Ce–Pr mixed oxide for the combustion of soot, lowering the DPF regeneration temperature with regard to a counterpart catalyst-free DPF. The temperature for active regeneration of the Ce0.5Pr0.5O2-containing DPF when the soot content is low is in the range of 500–550 °C. When the Ce0.5Pr0.5O2-containing DPF is saturated with a high amount of soot, pressure drop and soot load at the filter reach equilibrium at around 360 °C under steady state engine operation due to passive regeneration. The uncoated DPF reached this equilibrium at around 440 °C. Comparing results at real exhaust with those at laboratory allow concluding that the Ce0.5Pr0.5O2-catalysed soot combustion in the real exhaust is not based on the NO2-assisted mechanism but is most likely occurring by the active oxygen-based mechanism.

A new synthesis route for bone chars using CO2 atmosphere and their application as fluoride adsorbents

This study describes a new synthesis route for bone chars using a CO2 atmosphere and their behavior as adsorbent for fluoride removal from water. Specifically, we have performed a detailed analysis of the adsorption properties of bone char samples obtained at different carbonization conditions and a comparative study with samples of bone char obtained via pyrolysis under nitrogen. Experimental results show that the nature of the gas atmosphere (CO2 versus N2) and the carbonization temperature play a major role to achieve an effective bone char for water defluoridation. In particular, the best adsorption properties of bone char for fluoride removal are obtained with those samples synthesized at 700 °C. Carbonization temperatures above 700 °C under CO2 atmosphere cause the dehydroxylation of the hydroxyapatite in the bone char, thus reducing its fluoride adsorption capacity. The maximum fluoride adsorption capacity for the bone char obtained in this study under CO2 atmosphere (i.e., 5.92 mg/g) is higher than those reported for commercial bone chars.