Staffan Lundgren

Spatially Resolved Effects of Deactivation on Field-Aged Automotive Catalysts

Four samples from each of two field-aged catalysts subjected to different field test conditions were investigated. The light-off and conversion performance of each sample was measured in a synthetic exhaust flow reactor system. Time-resolved laser IR spectroscopy was used to investigate the catalyst behaviour under transient conditions. Significant differences in light-off temperatures and transient conversion performance between the samples was observed. The samples taken from the inlet side of the monolith were more deactivated than the corresponding ones from the outlet. However, samples taken from peripheral positions always showed better performance than samples originating from the centre. For the covering abstract of the conference see IRRD 852385.

Deterioration of Three-Way Automotive Catalysts, Part I - Steady State and Transient Emission of Aged Catalyst

Five field-aged catalysts with different mileages were analysed with respect to emission performance and structural changes. The FTP-75 emission results were compared to synthetic exhaust gas tests including: i) light-off, ii) lambda screening at stationary and oscillating stoichiometry, iii) space velocity variation. Several samples from different positions of one catalyst were used to achieve the spatially resolved activity profile for that catalyst. Surface characterisation was used to characterise accumulated catalyst poison. Laboratory space velocity test was concluded to be a sensitive probe for catalyst performance: good correlation to vehicle emission data was found. An analysis of the influence of temperature and oscillation on the catalyst conversion performance was made, with particular emphasis on the ageing effects. The oxidation of hydrocarbons and CO, and the reduction of NO was significantly higher during oscillations at 753 K than at steady state, while this effect was not found at 653 K. The spatially resolved activity profile revealed large differences between the oxidation and NO reduction activities, the latter being the most significantly deteriorated catalyst function. For the covering abstract see IRRD 858138.

Sulfur adsorption and desorption on fresh and aged Ce containing catalysts

Abstract The effect of field ageing on the transient H 2 S emissions from Ce-containing three-way catalysts was studied with TPR experiments and XPS analysis. A set of differently aged catalyst samples was analyzed by SO 2 exposure followed by TPR treatment with H 2 , in combination with successive XPS analysis of the oxidation state of Ce. TPR studies were also made using H 2 , CH 4 , C 2 H 2 , C 3 H 6 and C 3 H 8 as reducing agents. It was found that the H 2 S desorption declines rapidly as a function of field ageing. Simultaneously, the TPR (with H 2 ) desorption peak temperature of H 2 S increases and the SO 2 peak temperature decreases. For the catalyst with high activity the Ce3d XPS spectra indicated a shift in the oxidation state from (III) to (IV) during sulfur adsorption. The severely aged catalyst stayed in the trivalent state, during sulfur storage and TPR. The temperature for maximum H 2 S formation strongly depend on the type of reducing agent. A fullscale engine bench test was performed, by use of chemical ionization mass spectrometry. The results are dicussed in the light of the flow reactor results. Possible explanations are discussed, as well as a possible mechanism for changes in the H 2 S formation, due to deactivation.

Double Compression Expansion Engine Concepts: A Path to High Efficiency

Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to todays turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)