Deactivation of after-treatment catalysts for bio-fuelled engines

To decrease the emissions of anthropogenic CO2 from vehicles one option is to increase the utilization of biobased fuels. However, there are challenges with this transition, one being the mitigation of emissions of the potent greenhouse gas methane, which is the main constituent of biogas. Another relates to the presence of catalyst poisons in biofuels due to a wide variety of raw materials that are used for the production of these fuels.In this thesis, the aim is to investigate how exhausts from biogas and biodiesel impact the emission control system of a heavy-duty vehicle. The catalysts in the emission control system are studied individually and as a system, with commercial biobased fuels and synthetic gas feeds containing catalyst poisons. After exposure to biogas exhaust for 900 h in an engine-bench, the Pd/Pt-Al2O3 oxidation catalyst was found to be severely deactivated in terms of CH4 oxidation activity. A decrease in low-temperature activity for NO oxidation to NO2 was observed, which impacts the performance of the SCR-catalyst down-stream in the system. This loss in activity is explained by the finding of catalyst poisons as well as metal segregation and sintering of the noble metal particles.The V2O5-WO3/TiO2 SCR-catalyst in the engine-bench system remained active for NOx reduction after long-term ageing, however, the decrease in NO2 formation over the oxidation catalyst at low temperatures could cause an increase in NOx emissions even if the SCR catalyst itself is still active. Except for the vanadium-based SCR catalyst also a Cu-CHA catalyst was studied. Both types of SCR catalysts were found to be sensitive to phosphorus poisoning and the Cu-CHA catalyst was also found to be sensitive to sulfur.From results obtained we propose that the SO2 exposure leads to the formation of Cu-bisulfate species that reduce the amount of copper sites available for NOx reduction in the Cu-CHA SCR catalyst. The degree of deactivation is also dependent on the reaction condition where the standard SCR reaction is more impacted than the fast SCR reaction

Deactivation of SCR catalysts - Impact of sulfur and the use of biofuels

In a near future, limits on CO2 emissions from vehicles will be introduced, which requires development of more fuel-efficient engines and most likely a transition towards the use of more biofuels. With the implementation of biofuels several issues could arise, one being the lack of fuel standards for these new type of fuels, leading to higher concentrations of catalyst poisons compared to conventional fossil fuels. This work specifically focuses on catalyst poisoning originating from biofuels and is based on two papers.The aim of the work presented in paper I is to study the influence of SO2 on the low-temperature performance of a Cu-SSZ-13 SCR (selective catalytic reduction) catalyst. In particular the sulfur exposure temperature and the influence of the NO2/NOx ratio are considered, and two different regeneration temperatures are investigated. The results show that the temperature at which the Cu-SSZ-13 catalyst is exposed to SO2 is a critical parameter. The lowest exposure temperature (220\ub0C) resulted in the most pronounced deactivation, while the highest exposure temperature (400\ub0C) caused the lowest degree of deactivation of the catalyst. It was also shown that the exposure to SO2 resulted in decreased N2O selectivity. Engine-aging of the Cu-SSZ-13 catalyst resulted in decreased SCR activity and increased selectivity towards N2O formation, which most likely is caused by impurities from the fuel and engine-oil.In paper II, the influence of the fuel on the functionality of a commercial vanadia-based SCR catalyst after extended field-operation is investigated. The NH3-SCR activity, NH3-oxidation activity, NH3 adsorption capacity, specific surface area and surface composition were measured before and after field-operation in two heavy-duty Euro V vehicles fuelled with fatty acid methyl ester (FAME) and hydrotreated vegetable oil (HVO), respectively. For the catalyst samples taken from the vehicle fuelled with FAME, the NH3-SCR activity, NH3-oxidation activity and NH3 adsorption capacity were significantly lower compared to the fresh sample and the samples taken from the vehicle fuelled with HVO. This is likely due to accumulation of catalyst poisons that originates from the FAME fuel that cause blocking of the active sites on the vanadia-based catalyst.The studies of single poison compounds in lab-scale experiments are important for the understanding of catalyst deactivation mechanisms, however, there are many more parameters that dictates the deactivation in a vehicle. This can be seen from the engine-aged samples in both paper I and II where a single poison cannot fully explain the observed deactivation

"Tonga" : A Novel Toolbox for Straightforward Bioimage Analysis

Techniques to acquire and analyze biological images are central to life science. However, the workflow downstream of imaging can be complex and involve several tools, leading to creation of very specialized scripts and pipelines that are difficult to reproduce by other users. Although many commercial and open-source software are available, non-expert users are often challenged by a knowledge gap in setting up analysis pipelines and selecting correct tools for extracting data from images. Moreover, a significant share of everyday image analysis requires simple tools, such as precise segmentation, cell counting, and recording of fluorescent intensities. Hence, there is a need for user-friendly platforms for everyday image analysis that do not require extensive prior knowledge on bioimage analysis or coding. We set out to create a bioimage analysis software that has a straightforward interface and covers common analysis tasks such as object segmentation and analysis, in a practical, reproducible, and modular fashion. We envision our software being useful for analysis of cultured cells, histological sections, and high-content data.Peer reviewe

Predator–prey overlap in three dimensions: cod benefit from capelin coming near the seafloor

Spatial overlap between predator and prey is a prerequisite for predation, but the degree of overlap is not necessarily proportional to prey consumption. This is because many of the behavioural processes that precede ingestion are non-linear and depend on local prey densities. In aquatic environments, predators and prey distribute not only across a surface, but also vertically in the water column, adding another dimension to the interaction. Integrating and simplifying behavioural processes across space and time can lead to systematic biases in our inference about interaction strength. To recognise situations when this may occur, we must first understand processes underlying variation in prey consumption by individuals. Here we analysed the diet of a major predator in the Barents Sea, the Atlantic cod Gadus morhua, aiming to understand drivers of variation in cod's feeding on its main prey capelin Mallotus villosus. Cod and capelin only partly share habitats, as cod mainly reside near the seafloor and capelin inhabit the free water masses. We used data on stomach contents from ~2000 cod individuals and their surrounding environment collected over 12 years, testing hypotheses on biological and physical drivers of variation in cod's consumption of capelin, using generalized additive models. Specifically, effects of capelin abundance, capelin depth distribution, bottom depth and cod abundance on capelin consumption were evaluated at a resolution scale of 2 km. We found no indication of food competition as cod abundance had no effect on capelin consumption. Capelin abundance had small effects on consumption, while capelin depth distribution was important. Cod fed more intensively on capelin when capelin came close to the seafloor, especially at shallow banks and bank edges. Spatial overlap as an indicator for interaction strength needs to be evaluated in three dimensions instead of the conventional two when species are partly separated in the water column.publishedVersio

European Network of Breast Development and Cancer turned 10 years: a growing family of mammary gland researchers

The European Network for Breast Development and Cancer (ENBDC), a worldwide network (http://www.enbdc.org/), celebrated its tenth anniversary with a fantastic meeting last March 15-17, 2018 in Weggis with 76 attendees

Effect of biofuel- and lube oil-originated sulfur and phosphorus on the performance of Cu-SSZ-13 and V2O5-WO3/TiO2 SCR catalysts

Two different SCR catalysts, V2O5-WO3/TiO2 and Cu-SSZ-13, were exposed to biodiesel exhausts generated by a diesel burner. The effect of phosphorus and sulfur on the SCR performance of these catalysts was investigated by doping the fuel with P-, S-, or P + S-containing compounds. Elemental analyses showed that both catalysts captured phosphorus while only Cu-SSZ-13 captured sulfur. High molar P/V ratios, up to almost 3, were observed for V2O5-WO3/TiO2, while the highest P/Cu ratios observed were slightly above 1 for the Cu-SSZ-13 catalyst. Although the V2O5-WO3/TiO2 catalyst captured more P than did the Cu-SSZ-13 catalyst, a higher degree of deactivation was observed for the latter, especially at low temperatures. For both catalysts, phosphorus exposure resulted in suppression of the SCR performance over the entire temperature range. Sulfur exposure, on the other hand, resulted in deactivation of the Cu-SSZ-13 catalyst mainly at temperatures below 300-350 \ub0C. The use of an oxidation catalyst upstream of the SCR catalyst during the exhaust-exposure protects the SCR catalyst from phosphorus poisoning by capturing phosphorus. The results in this work will improve the understanding of chemical deactivation of SCR catalysts and aid in developing durable aftertreatment systems

Protocol for Studying Embryonic Mammary Gland Branching Morphogenesis Ex Vivo

Mammary gland development starts during embryogenesis, and the process continues after birth. During development, the mammary gland undergoes massive morphological and physiological alterations including growth, invasion, and branching morphogenesis providing an ideal model for stem cell and cancer biology studies. Great efforts have been made in understanding mammary gland development during puberty and adulthood; however, the process during embryogenesis is still elusive. One reason is that the tools to study tissue dynamics during development are limited, which is partially due to the lack of an ex vivo culture method. Here we describe an updated organ culture protocol of the murine embryonic mammary gland. This powerful tool allows monitoring of growth and branching morphogenesis of mammary gland ex vivo by live imaging. In addition, we introduce a novel method for culturing intact, stroma-free mammary rudiments from late gestation mouse embryos in 3D in Matrigel. This approach can be used to identify the direct stromal cues for branching morphogenesis.Non peer reviewe

Laminin alpha 5 regulates mammary gland remodeling through luminal cell differentiation and Wnt4-mediated epithelial crosstalk

Epithelial attachment to the basement membrane (BM) is essential for mammary gland development, yet the exact roles of specific BM components remain unclear. Here, we show that Laminin alpha 5 (Lama5) expression specifically in the luminal epithelial cells is necessary for normal mammary gland growth during puberty, and for alveologenesis during pregnancy. Lama5 loss in the keratin 8-expressing cells results in reduced frequency and differentiation of hormone receptor expressing (HR+) luminal cells. Consequently, Wnt4-mediated crosstalk between HR+ luminal cells and basal epithelial cells is compromised during gland remodeling, and results in defective epithelial growth. The effects of Lama5 deletion on gland growth and branching can be rescued by Wnt4 supplementation in the in vitro model of branching morphogenesis. Our results reveal a surprising role for BM-protein expression in the luminal mammary epithelial cells, and highlight the function of Lama5 in mammary gland remodeling and luminal differentiation.Peer reviewe

Deactivation of a Vanadium-Based SCR Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation

We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NO(x)reduction performance in terms of standard, fast and NO2-rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NO(x)reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V4+/V(5+)ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V(4+)to V(5+)is partially hindered, blocking the redox cycle for parts of the active sites

Spatio-temporal activation of caspase-8 in myeloid cells upon ischemic stroke

Ischemic stroke (caused by thrombosis, embolism or vasoconstriction) lead to the recruitment and activation of immune cells including resident microglia and infiltrating peripheral macrophages, which contribute to an inflammatory response involved in regulation of the neuronal damage. We showed earlier that upon pro-inflammatory stimuli, the orderly activation of caspase-8 and caspase-3/7 regulates microglia activation through a protein kinase C-δ dependent pathway. Here, we present in vivo evidence for the activation of caspase-8 and caspase-3 in microglia/macrophages in post-mortem tissue from human ischemic stroke subjects. Indeed, CD68-positive microglia/macrophages in the ischemic peri-infarct area exhibited significant expression of the cleaved and active form of caspase-8 and caspase-3. The temporal and spatial activation of caspase-8 was further investigated in a permanent middle cerebral artery occlusion mouse model of ischemic stroke. Increasing levels of active caspase-8 was found in Iba1-positive cells over time in the peri-infarct area, at 6, 24 and 48 h after artery occlusion. Analysis of post-mortem brain tissue from human subject who suffered two stroke events, referred as recent and old stroke, revealed that expression of cleaved caspase-8 and -3 in CD68-positive cells could only be found in the recent stroke area. Analysis of cleaved caspase-8 and -3 expressions in a panel of human stroke cases arranged upon days-after stroke and age-matched controls suggested that the expression of these caspases correlated with the time of onset of stroke. Collectively, these data illustrate the temporal and spatial activation of caspase-8 and -3 in microglia/macrophages occurring upon ischemic stroke and suggest that the expression of these caspases could be used in neuropathological diagnostic wor