Abstract
Low-energy wet milling was employed to activate commercial CoAl2O4 spinel and disperse mono- and multimetallic nanoparticles on its surface. This method yielded efficient Pt,Ni catalysts for soot oxidation in simulated diesel exhaust conditions. The characterization and activity results indicated that although Ni/CoAl2O4 was highly active, the presence of Pt was required to obtain a stable Ni(0.25 wt. %),Pt(0.75 wt. %)/CoAl2O4 catalyst under the operating conditions of diesel particulate filters, and that hot spots formation must be controlled to avoid the deactivation of the cobalt aluminate. Our work provides important insight for new design strategies to develop high-efficiency low-cost catalysts. Platinum-containing multimetallic nanostructures could efficiently reduce the amount of the costly, but to date non-replaceable, Pt noble metal for a large number of industrially important catalytic processes.
Highlights
Diesel internal-combustion engine emissions could rise between 50% and 250% by 2050 [1] despite the increasingly stringent regulations for vehicles in both the EU and the US, and, even more regulation in this sector is expected to limit their impact on health and the environment [2]
Promotion by alkali metals is reported to increase the catalyst ability to form compounds with low melting point temperatures [18]. This is meant to increase the number of contact points between the catalyst surface and soot particles, which is essential for soot oxidation [19,20,21,22]
We have recently reported that the creation of acid sites and defects in commercially available CoAl2 O4 by wet milling yields a low-cost active catalyst for soot oxidation [50]
Summary
Diesel internal-combustion engine emissions could rise between 50% and 250% by 2050 [1] despite the increasingly stringent regulations for vehicles in both the EU and the US, and, even more regulation in this sector is expected to limit their impact on health and the environment [2]. Un-catalyzed soot combustion occurs at around 600 ◦ C, and, a catalyst is added to reduce this temperature below that of diesel exhausts, in the range from 260 to 540 ◦ C [1,8,9] Noble metals, such as Pt, achieve high catalytic activity by oxidizing the NO present in the exhaust gas to NO2 , which promotes soot combustion [10,11]. Promotion by alkali metals is reported to increase the catalyst ability to form compounds with low melting point temperatures [18]. This is meant to increase the number of contact points between the catalyst surface and soot particles, which is essential for soot oxidation [19,20,21,22]. In this context, mixed oxides built of d-metal cations (Fe, Mn, Co), which
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