Enhancing the low temperature oxidation performance over a Pt and a Pt–Pd diesel oxidation catalyst

Abstract

The influence of hydrogen over platinum and combined platinum-palladium diesel oxidation catalysts were investigated on the oxidation kinetics of CO, HC and NO. Although H 2 has been reported to have a positive effect on CO and HC oxidation as well as NO 2 formation over platinum catalysts, there is still uncertainty whether this is due to the temperature rise caused by H 2 oxidation or the result of a change in the reaction kinetics of CO, HC and NO oxidation by the production of intermediate species. The results have showed smaller H 2 concentrations are more effective in improving the catalyst light-off temperature as well as promoting NO oxidation over both platinum and platinum-palladium catalysts. It is suggested that these benefits are a result of not only the exothermic reactions which in turn increase the local catalyst temperature but also H 2 increasing the rate of reactions and the species accessibility to the catalyst active sites thus further CO, HC and NO oxidation can occur at lower catalyst temperatures.

Experimental study on detailed emissions speciation of an HCCI engine equipped with a three-way catalytic converter

“…In principle, low performance of hydrocarbons oxidation concerns all engines which produce exhaust gases at low temperatures, e.g. diesel engines under low loads [22].…”

Kinetic Modeling of C3H6 Inhibition on NO Oxidation over Pt Catalyst

“…(1) Surface components balance for each surface species w in each tank k was described by transient equation shown in Equation (2). When steady state condition is achieved, the derivative term in Equation (2) turns to zero.…”

“…For example it is restricted by thermodynamics at high temperature, it possess hysteresis phenomenon during heating and cooling, it is structure sensitive and the reaction is inhibited by HC and CO at low temperature [1]. Recently, it has also been reported that addition of H2 may boost the NO oxidation reaction over Pt catalysts [2,3]. For this reason, kinetic studies of NO oxidation over Pt/Al2O3 have gained a lot of interests from a number of research groups.…”

Increased NO2 concentration in the diesel engine exhaust for improved Ag/Al2O3 catalyst NH3-SCR activity

“…The approaches can be described as i) hydrogen addition directly to the SCR, ii) Pt/Al2O3 -DOC placement in the front of the SCR and iii) hydrogen addition upstream the DOC and the SCR [19][20][21]. The well know storage limitations of hydrogen for automotive applications could be solved through the carbon free process of on-board catalytically production of hydrogen through ammonia exhaust gas reforming.…”