Ingemar Odenbrand

Characterisation of Silica-Titania Mixed Oxides

Abstract A series of coprecipitated silica-titanias containing between 0 and I00 mol% titania were characterized by various methods. These materials are often used as supports for catalysts in the reduction of NO x and are shown to be micro-, meso-, and macroporous. All textural quantities decrease with the addition of TiO 2 to SiO 2 . The macroporosity, of vital importance in the highly diffusion-controlled NO x reduction, reaches a maximum value at 50 mol% TiO 2 . X-ray diffraction, FT-IR, and XPS studies showed that the materials, calcined at 723 K, consisted of a SiO 2 -TiO 2 glass phase, an amorphous silica phase, and an anatase phase. At I0 mol% TiO 2 , rutile was observed, by XRD, in addition to anatase. XPS data indicate the presence of a TiO 2 phase in all Ti-containing samples, a SiO 2 phase at and below 50 mol% TiO 2 , and a SiO 2 -TiO 2 phase at and above 75 mol% TiO 2 . The quantitative XPS analysis indicates a heterogeneous distribution of phases with an increased surface concentration of Si phases. Similar results were obtained by the FT-IR studies, which additionally indicate the presence of surface free silanol groups in all samples and detect tetrahedrally substituted Ti 4+ in the SiO 2 phase.

Combustion of methane over a Pd-Al2O3/SiO2 catalyst, catalyst activity and stability

Abstract Palladium supported on Si-stabilised alumina has been demonstrated to be an active and durable catalyst for the combustion of methane. Si is more effective in stabilising alumina than La or Ba when the elements are added through an impregnation technique. Multiple stabilisation with combinations of La, Ba and Si does not increase further the stability against sintering. The stability increases logarithmically with the amount of Si added (0.5–8 atomic%). The rate of sintering is not affected by an increase of the water vapour content of the atmosphere from 1 to 20 vol.%. Doping palladium with rhodium or platinum increases the activity of the catalyst for methane combustion. The high-temperature stability of pure Pd is however superior to the stabilities of the Rh- and Pt-doped catalysts. Addition of La or Ce to the Pd-catalyst increases its stability against thermal deactivation but leads to an overall decrease in activity. The activity of the as-prepared catalysts are affected by the Pd-content below a value corresponding to 5% of the monolayer capacity. Thermally deactivated catalysts show a stronger activity dependence of the Pd-content than asprepared catalysts. The combustion reaction is first order with respect to methane and zero-order with respect to oxygen (>2 vol.% of oxygen). Carbon dioxide has no inhibitory effects on the combustion. The activity of the Pd-catalyst is decreased by a factor of 5 through deactivation at 1473 K for 768 h. The decrease in activity is linearly correlated to the decrease in specific surface area.

Thermally sprayed wire-mesh catalysts for the purification of flue gases from small-scale combustion of bio-fuel - Catalyst preparation and activity studies

Catalytically active wire meshes were used to combust different pollutants present in flue gases from bio-fuel combustion, e.g. CO, propylene, terpenes and tar. Alumina was spray-deposited onto wire meshes of Kanthal AF (8-20 Tayler mesh) with a plasma spray equipment. The specific surface area of the ceramic layer was increased through wash coating, in-situ precipitation or sol-treatment. The catalytically active materials consisted of precious metals (Pd/Pt) or metal oxides (V2O5/CuO) and were added to the ceramic matrix through an impregnation technique. The combustion was in most cases severely limited by external mass transfer. The effects of the specific surface area and the loading of catalytically active material were only significant in the reaction controlled domain. In the mass transfer controlled domain the conversion was affected only by the flow conditions and the external surface area of the wire meshes. CO and most hydrocarbons were effectively combusted at temperatures below 773 on a Pd/Pt-catalyst. The catalyst performance was not affected by the presence of water vapour or carbon dioxide or by low oxygen concentrations. Similar combustion experiments were performed with a commercial monolith and it can be concluded that the performance of the catalytically active wire meshes in the mass-transfer controlled domain was superior. Tar-residues, soot particulates and charcoal particles were effectively combusted over a Pd/Pt-doped oxide-catalyst (V2O5/CuO). (Less)

A State-Space Simplified SCR Catalyst Model for Real Time Applications

The use of Selective Catalytic Reduction (SCR) is becoming increasingly more popular as a way of reducing NOx emissions from heavy duty vehicles while maintaining competitive operating costs. In order to make efficient use of these systems, it’s important to have a complete system approach when it comes to calibration of the engine and aftertreatment system. This paper presents a simplified model of a heavy duty SCR catalyst, primarily intended for use in combination with an engine-out emissions model to perform model based offline optimization of the complete system. The traditional way of modelling catalysts using a dense discretization of the catalyst channels and non-linear differential equation solvers to solve the heat and mass balance equations, requires too much computational power in this application. The presented model is also useful in other applications such as model based control. The basic model structure is a series of continuously stirred tank reactors using discretized catalyst walls to describe the mass transport in the solid phase. The simplified model uses a state-space concept. At low temperatures the model uses an implicit method of calculating the coverage differential. At higher temperatures, the model is simplified to a first order system using an operating condition dependent characteristic time constant. These simple, yet robust methods allows for long step lengths in the process of solving the differential equations. This makes the model a useful improvement over current models.

Model Predictive Control of a Combined EGR/SCR HD Diesel Engine

Materials Noise, Vibration and Harshness Parts and Components Power and Propulsion Quality, Reliability and Durability Safety Tests and Testing Transportation Systems Vehicles and Performance Other Options Papers by Event SAE Home > Papers> By Event> SAE 2010 World Congress & Exhibition Model Predictive Control of a Combined EGR/SCR HD Diesel Engine Date Published: 2010-04-12Paper Number: 2010-01-1175 DOI: 10.4271/2010-01-1175 Author(s): Claes Westerlund - Scania CV AB Bjorn Westerberg - Scania CV AB Ingemar Odenbrand - Lund Univ. Rolf Egnell - Lund Univ. View All CollapseAbstract Achieving upcoming HD emissions legislation, Euro VI / EPA 10, is a challenge for all engine manufacturers. A likely solution to meet the NO x limit is to use a combination of EGR and SCR. Combining these two technologies poses new challenges and possibilities when it comes to optimization and calibration.

New halogen-specific detector applied to the analysis of chlorinated fatty acids

A new halogen-specific detection method (XSD) was tested for determination of chlorinated fatty acids in marine biota. In XSD, an increased emission of ions and electrons is caused by the high-temperature combustion of halogen-containing compounds. The detection limit of methyl dichlorooctadecanoate and the selectivity at a reactor temperature of 900 degrees C match those of electrolytic conductivity detection (ELCD). The relative standard deviation is less than 11% for > or =0.2 ng methyl dichlorooctadecanoate. An XSD chromatogram of a complex sample, chlorinated fatty acid methyl esters liberated from fish lipids, agreed with a previously obtained ELCD chromatogram.

Response factors of organochlorine compounds in the electrolytic conductivity detector

In our previous studies we have used electrolytic conductivity detection (ELCD) in the selective analysis of chlorinated fatty acids in marine samples. In order to determine the chlorinated fatty acids quantitatively, we studied the ELCD response factors (RFs) of chlorinated fatty acids and compared them with those of other chlorinated compounds. We also studied the effect of reactor temperature and total gas flow-rate on the RFs. The ELCD RFs of different organochlorine compounds varied significantly at a reactor temperature of 600°C. The variation was reduced at reactor temperatures higher than 850°C. At low reactor temperatures, the RFs of methyl esters of chlorinated fatty acid were much higher than those of the other compounds. Although the gas flow in the reactor was laminar, diffusion was still rapid enough not to cause the varied RFs. Nitrogen-containing chlorinated compounds had lower RFs than compounds without nitrogen, owing to a neutralization of hydrogen chloride by ammonia.