Structured catalysts for soot combustion for diesel engines

E.D. BANÚS; M. A. ULLA; E.E. MIRÓ; V. G. MILT

Diesel Engine - Combustion, Emissions and Condition Monitoring

InTech Open

Año: 2013; p. 117 - 142

It can be seen that nowadays the most popular systems for soot elimination in dieselexhausts are a complex combination of different types of physical and chemical processes.More compact processes are highly desirable to reduce costs and improve efficiency. To thisend, the synergism between better understandings of the fundamentals of the catalyticreactions together with the development of new structured systems able to efficiently retainsoot particles is highly desirable. It has been shown that an adequate morphology of thecatalyst is required so as to improve the contact between the catalyst and soot and,simultaneously, the catalyst should be supported as a film on a porous structured substrate,thus allowing simultaneous soot filtration and combustion.Although monoliths and foams are the most widely studied substrates for the preparation ofstructured catalysts, other merging substrates that can be considered for controlling thediesel engines exhaust pollutants are ceramic papers and wire meshes. In our laboratory,research works are ongoing, with the aim of developing these types of novel structures inorder to make them efficient and economic diesel particulate catalytic filters. In this vein,papers made of ceramic fibers, cerium oxide and potassium nitrate were prepared whichprovided a high-temperature resistant paper with good activity for soot combustion attemperatures as low as 390°C. Moreover, the use of zeolitic ingredients added to the paperconstituted a new way to generate new and effective SCR structured catalysts. Thus, theintercalation of paper beds containing different catalysts (sandwich catalysts) could be usedfor the one-step process to simultaneously eliminate soot particles and NOx.On the other hand, we have developed filters made of AISI-316 stacked wire meshes coatedwith the Co,Ba,K/CeO2 catalyst, that showed good activity for the combustion of diesel soot.Wire-mesh catalysts combine excellent mass and heat transfer performance with lowpressure drop, the catalyst efficiency being considerably improved compared with pellet ormonolith catalysts. The effects of catalyst clogging and fouling can be handled as thesestructured catalysts are easy to disassemble and to clean. Wire-mesh catalysts also offer agreat flexibility with respect to dimensions that make retrofit installations easier.