Kinetics, acid sites and deactivation of H-mordenite during the SCR of NOx with CH4

H-mordenites are active for the SCR reaction but they suffer irreversible partial deactivation after being on stream for one hour at 650°C. The reaction orders and activation energies are not significantly affected by deactivation. This indicates that deactivation originates in a decrease in the number of active sites due to dealumination and possible pore blockage. The NO disappearance rate correlates with TPD NH₃ between 300 and 700°C; FTIR confirms these results. ¹²⁹Xe NMR of adsorbed xenon shows that pore blockage occurs and is due to the presence of aluminum species in the main zeolite channels. The overall deactivation process and the role of acid sites is discussed in terms of the current literature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contribution to the elucidation of the structure of the bacterial flagellum nano-motor through AFM imaging of the M-Ring

The flagellar nano-motor of bacteria is one of the most interesting and amazing natural nano-machine. Despite its discovery 30 years ago, some details of its structure and mechanisms are not yet elucidated. Several studies have revealed some important aspects of its structure and numerous data are available today; however, the inner mechanisms of the nano-motor have not been yet resolved, partially due to the lack of information about the 3D assembly, shape and interactions of the different parts in experimental environment as close as possible as the native cellular conditions. We have developed an approach using atomic force microscopy imaging in liquid media, which allows us to study part of the motor in native liquid environment. In this work, we are interested in the FliG proteins, identified as the key functional proteins of this nano-machine. We report 3D images of their assembly on surfaces, which could be representative of the so-called M-ring part of the nano-motor. These images have been acquired on both mica surfaces and on supported bilayer membranes mimetics of E. coli native membrane. The systematic analysis of the shape and the size of different recorded assemblies made us believe that the FliG organization we observed could lead to a new model for the structure and mechanism of the flagellar nano-motor.     

Measurement of CHn group abundances in fossil fuel materials using DEPT 13C n.m.r.

¹³C n.m.r. subspectra assigned to CH, CH₂ and CH₃ groups can be obtained in reasonably quantitative conditions by using the distortionless enhancement by polarization transfer (DEPT). The method has been applied to light and heavy petroleum materials.     

Fast MR-imaging of porous media

The study of fluid displacements in porous media is of considerable interest for the oil industry as it provides a better understanding of the oil-recovery process. Consequently, fast MR imaging techniques for routine applications of sequencial analysis of large samples would be valuable. The performances of a variant of the Fast Low Angle Shot (FLASH) imaging technique called SNAP with a very short acquisition time of 144 ms per slice were evaluated on water and/or oil-filled core samples such as chalk and limestone whose linewidths were smaller than 800 Hz. The SNAP signal intensity was theoretically reviewed and inversion-recovery preweighted SNAP was used for fastT ₁ measurements in porous media. The images so acquired were processed using a pixel clusterization technique to segment images and roughly estimate oil and water content. This imaging method opens a new field of investigation such as the study of rapid fluid ingress or displacements.Address for correspondence: Catholic University of Louvain, Bâtiment Lavoisier (Bte 3A), Place Louis Pasteur 1, B-1348 Louvain-la-Neuve, Belgium. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY10119.     

23Na microimaging of water phase in porous limestone

²³Na microimaging has been investigated as a method for discriminating multiple fluid phases in porous media. Useful²³ Na images from NaCl saturated brine in limestone were obtained in a few-minutes. Good images requires several hours.Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY 10119.     

Analysis of asphaltenes by carbon and proton nuclear magnetic resonance spectroscopy

Proton and ¹³C nuclear magnetic resonance spectroscopy has been used to derive a series of parameters of an ‘average molecule’ which characterize complex multicomponent organic mixtures such as asphaltenes. The method developed here is based on a minimum of assumptions and takes explicitly into account the effects of the oxygen atoms on the chemical shift of the adjacent ¹³C atoms. Moreover, the integrated intensities characterizing ring junction or substituted and unsubstituted carbon atoms are no longer determined on a chemical shift basis but are calculated by using parameters extracted from ¹H and ¹³C spectra. Factors influencing quantitative ¹³C measurements on asphaltenes in the Fourier transform mode are briefly discussed. The variations of parameters such as the aromaticity factor, the degree of substitution, and the number of aromatic and naphthenic cycles per structural unit are studied as functions of depth of burial for rock samples from the Toarcian Paris basin.     

Structural evolution of a sedimentologically homogeneous coal series as a function of carbon content by solid state 13C n.m.r.

The cross polarization technique combined with magic-angle spinning has been applied to obtain ¹³C n.m.r. spectra of a sedimentologically homogeneous series of peat, lignite and bituminous coal derived from higher plants. Despite some uncertainties on the quantitative aspects of the method, the structural information obtained was corelated with data from elemental analysis. Structural average parameters were also calculated by using the structural basic unit concept and relating it to the maturation stage of the organic matter.