Noble metal-free ceria-based diesel soot combustion catalyst, suitable for gas purification in Diesel engine exhausts

Description of the technology

A research group of the University of Alicante has developed a new diesel soot combustion catalyst which consists of a high surface area nanoscale material (ceria-praseodymia oxide). It has better or equal activity than Pt catalysts and, as it is noble metal free, it is cheaper. It can be used to remove soot in gas exhausts from combustion engines used in industrial processes, vehicles or stationary power generation engines. Companies are sought to license the technology or adapt the developed catalyst to their needs.

Specifications

A catalyst active phase has been developed with the following composition Ce0.5Pr0.5O2 particles size smaller than 9 nm and specific surface areas higher than 90 m2/g. The method used allows obtaining 7 nm particles with 125 m2/g surface area. The synthesis is carried out using a reverse microemulsion and following the several steps: 1. The cerium and praseodymium precursors are dissolved in water. 2. An emulsion is prepared with the previous water solution. 3. Another alkali emulsion is prepared. 4. Both emulsions are mixed. 5. The solid obtained is separated by centrifugation. 6. The solid is calcined at T > 400ºC. Figure 1 shows the soot conversion profiles obtained with the novel ceria-praseodymia nanoparticles under a diesel exhaust simulated gas mixture (500 ppm NO + 5 % O2 en N2; 30000 h-1). Reference curves obtained with a commercial 1% Pt/alumina catalyst, with a ceria-praseodymia prepared by a conventional precipitation procedure and without catalyst. All soot:catalyst mixtures used simulate the loose contact attained in real conditions. Doped ceria catalysts either with zirconium or praseodymium show high activity, but the platinum catalysts performance is on only overcome by the ceria-praseodymia catalysts prepared in the current invention by the microemulsion method. The high activity of these ceria-praseodymia catalysts is related to: (i) the intrinsic high catalytic activity of ceria-praseodymia mixed oxides, which relies on the high production of active oxygen species and (ii) the small particle size, which allows the transfer of such active oxygen species from catalyst to soot particles. This is evidenced on Figure 2, where the T50% temperature is plotted against the catalyst particle size for two sets of ceria-based catalysts. The selected compositions of these sets of catalysts were the most actives for ceria-zirconia (20 molar % zirconium) and ceria-praseodymia (50 molar % praseodymia) according to previous studies, and different synthesis methods were used (calcination of nitrates mixture, coprecipitation and reversed microemuslion; all catalysts were calcined at 500ºC, otherwise indicated.

Main advantages of its use

• Better/equal activity tan Pt catalysts at cheaper prize
• Higher surface per particle
• Higher yield of oxygen production (useful for oxidation reactions)
• Lower particle size

Applications

• This technology is suitable for gas purification in Diesel engine exhausts, like vehicles, stationary power generation engines, etc.

Additional information (attached documents)

• Figure 1 - Fig1.jpg
• Figure 2 - Fig2.jpg