Sökning: "Sulfur accumulation"

Visar resultat 1 - 5 av 14 avhandlingar innehållade orden Sulfur accumulation.

1. 1. Sulfur-Related Conservation Concerns in Marine Archaeological Wood : The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa

   Författare :Yvonne Fors; Magnus Sandström; Ian MacLeod; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sulfur accumulation; marine archaeological wood; Vasa; acidity; iron; ammonia; x-ray spectroscopy; cellulose; Chemistry; Kemi; strukturkemi; Structural Chemistry;

   Sammanfattning : Synchrotron-based sulfur spectroscopy reveals a common concern for marine archaeological wood from seawater: accumulation of reduced sulfur compounds in two pathways. The distribution of sulfur species in the oak wood cell structure was mapped by scanning x-ray spectro-microscopy (SXM). LÄS MER

3. 2. Deactivation of SCR catalysts - Impact of sulfur and the use of biofuels

   Författare :Johanna Englund; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; Cu-SSZ-13; Cu-CHA; Catalyst deactivation; Activity test; DeNOx; Sulfur; NOx reduction; NH3-SCR; FAME; Emission control; HVO; Vanadia; Biofuel;

   Sammanfattning : 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. LÄS MER

4. 3. Structure and bonding of sulfur-containing molecules and complexes

   Författare :Emiliana Damian Risberg; Magnus Sandström; Ingmar Persson; Tsun-Kong Sham; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sulfur species; x-ray absorption and vibrational spectroscopy; TP-DFT calculations; Chemistry; Kemi; strukturkemi; Structural Chemistry;

   Sammanfattning : Synchrotron-based spectroscopic techniques enable investigations of the many important biological and environmental functions of the ubiquitous element sulfur. In this thesis the methods for interpreting sulfur K-edge X-ray absorption near edge structure (XANES) spectra are developed and applied for analyses of functional sulfur groups. LÄS MER

5. 4. Dynamics and Reactivity of Cu-species in Cu-CHA for NH3-SCR

   Författare :Joachim Bjerregaard; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Machine Learning Force Field; Diffusion; Cu-CHA; NH3-SCR; DFT; Sulfur Deactivation;

   Sammanfattning : Copper exchanged chabazite (Cu-CHA) is a state-of-the-art catalyst for deNOx via ammonia assisted selective catalytic reduction (NH3-SCR) in lean burn engines, owing to its good low-temperature activity, and high hydrothermal stability. One challenge for Cu-CHA is, however, the sensitivity to sulfur species, which are present in the exhaust gas. LÄS MER

7. 5. Aging effects on commercial lean NOx trap catalysts

   Författare :Jesus De Abreu Goes; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; aging; thermal degradation; sulfur poisoning; characterization; commercial lean NOx traps; NOx storage and reduction;

   Sammanfattning : As a countermeasure to global warming, vehicles with low carbon emissions are being investigated by promoting lean-burn engines and high combustion efficiencies. However, one limitation to the increasing use of these engines is the need to develop corresponding catalytic systems for controlling the nitrogen oxide (NOx) emissions in their lean exhaust. LÄS MER