High-throughput approach to the catalytic combustion of diesel soot

A methodology for the evaluation of diesel soot oxidation catalysts by high-throughput (HT) screening was developed. The optimal experimental conditions (soot amount, catalyst/soot ratio, type of contact, composition and flow rate of gas reactants) ensuring a reliable and reproducible detection of light-off temperatures in a 16 parallel channels reactor were set up. The temperature profile measured in the catalyst/soot bed under TPO conditions when the exothermic combustion of soot takes place was shown to provide an accurate measurement of the ignition. Its reproducibility and relevance were checked. The results obtained with a reference noble metal free catalyst (La_0.8Cr_0.8Li_0.2O₃ perovskite) agree very well with literature data. Qualitative mechanistic features could be derived from these experiments, stressing the likely limiting step of oxygen transfer from catalyst surface to soot particulates to ignite the soot combustion. Ceria material was shown to be more appropriate than perovskite one. From an HT screening of a large diverse library (over 100 mixed oxides catalysts) under optimized conditions, about 10 new formulations were found to perform better than selected noble metal free reference materials.     

Low‐temperature selective oxidation of hydrogen sulfide into elemental sulfur on a NiS2/SiC catalyst

Nickel sulfide supported on SiC exhibits a very high activity and selectivity for the direct oxidation of H₂S into elemental sulfur at low reaction temperature (60°C). The presence of water on the catalyst surface could explain the absence of deactivation even at high sulfur loading of the surface. The chemical inertness of the SiC support allowed any detrimental reactions between the active phase and the support itself to be avoided.     

Silicon Substitution for Aluminum in Calcium Silicate Hydrates

²⁷Al MAS and multiquantum (MQ) MASNMR (magic-angle spinning nuclear magnetic resonance) spectroscopy were used to study the substitution of silicon by aluminum in calcium silicate hydrates (C-S-H), which are the main component of hydrated portland cement. Synthetic C-S-H samples were prepared, and their chemical stability was studied. Two-dimensional 3Q-MASNMR spectra revealed the chemical shift and quadrupolar parameters (delta_iso, nu_Q) that labeled aluminum sites in the C-S-H. Tetrahedral aluminum was observed in the bridging and nonbridging sites of the silicate chains.     

One-line measurement of the residence time distribution in screw extruders

A fluorescence monitoring device was constructed to measure in real time the residence time distribution (RTD) function in screw extruders. Its centerpiece was an optical fiber probe capable of transmitting optical excitation energy to the processed flow stream and detecting the subsequent fluorescence emission. The source of fluorescence emission was an anthracene-bearing substance that was injected to the flow stream as a pulse (tracer) in very small amounts. This device was validated against an off-line ultraviolet spectrophotometer and self-checked as well. In addition to its great sensitivity to fluorescence emission and ease of implementation on an extrusion line, this device could be used to monitor in real time subtle variations of an extrusion operation. The influence of the nature of anthracene-bearing compounds on the measured distribution and the effects of processing parameters on the RTD function were also investigated.     

Continuous fixed bed biosorption of Cu2+ ions: application of a simple two parameter mathematical model

Biomass from two fungi of the Mucorales order, laboratory cultured and immobilised Rhizopus arrhizus, and industrial waste Mucor miehei, was tested for capacity to adsorb copper from solution in batch and continuous‐flow column systems. Maximum uptake levels were c 400 and 300 mmol g⁻¹ (dry weight) respectively. Immobilisation of Rhizopus arrhizus in polyvinyl formal to cell loadings of 60% (w/w) did not diminish metal uptake levels. In continuous‐flow columns both biosorbents adsorbed copper to levels equal or approaching the batch uptake values. Column breakthrough curves were fitted to a two parameter model and each of the parameters, σ and t₀ , were linearly correlated with column operating parameters. Predicted breakthrough curves agreed closely with experimental values. © 1999 Society of Chemical Industry     

The invasion of a large lake by the Eurasian genotype of common reed: The influence of roads and residential construction

The Eurasian genotype of common reed (Phragmites australis) is one of the most aggressive plant invading North American wetlands. There is, however, little published evidence on establishment patterns of populations along lakes of the St. Lawrence River–Great Lakes watershed. We tested the hypothesis that the recent invasion of Great Lake Saint-François (Québec, Canada) by common reed was facilitated by a dense road system and by an intense residence construction activity along lakeshores. A total of 345 and 2914 reed stands were mapped along lakeshores, and along the road system of the study area, respectively. The probability of finding a reed stand on a lakeshore increases with the proximity of the lake's outlet, and of a paved road, but decreases with the proximity of a residence built since 1990. It is likely that common reed first spread along the road system, and that wind dispersal of seeds then favored the establishment of populations on lakeshores. Our model does not support the hypothesis that residential construction facilitated the establishment of reed stands, probably because the recent residential construction boom occurred essentially in the southern part of the lake, where the number of roadside reed populations is much lower than in the northern part (lower seed rain). The invasion of Great Lake Saint-François shows that the spread of the plant is not restricted to major river or road systems. Large or small lakes, if submitted to intense diaspore pressure, can also be at risk.     

Microbial inactivation by pulsed electric fields in a batch treatment chamber: effects of some electrical parameters and food constituents

The inactivation of Escherichia coli by high voltage pulsed electric fields in a batch treatment chamber was studied in liquid, solid and semisolid foods or model systems. Treatment heterogeneity was demonstrated and found to be due to the presence of an air bubble trapped inside the chamber. Agitation of the inoculated liquid samples (16 mM sodium phosphate buffer, pH 7, ρ=460 Ωcm) during pulse processing resulted in efficient microbial inactivation (five log cycles at 33 kV/cm and 25°C after 261 μs of cumulated pulses). A slower inactivation rate was observed in inoculated solid agar gels of the same pH and resistivity, under the same pulse processing conditions. The inactivation of E. coli in inoculated dairy cream (33% fat, pH 6.8, ρ=370 Ωcm), ovalbumin solution (10% protein w/v, pH 6.7, ρ=370 Ωcm) or fish egg suspension (pH 6.8, ρ=400 Ωcm) was almost identical to that in 16 mM phosphate buffer, pH 7. Thus emulsified lipids, soluble proteins or conductive food particulates do not appear to protect against microbial inactivation by electric pulses.     

Exposure of several Belgian consumer groups to pesticide residues through fresh fruit and vegetable consumption

The output of a pesticide surveillance program (detection frequency and number of exceeding measures) can lead to unnecessary concern among consumers since they lack information concerning the actual exposure. In this study, the exposure to pesticide residues through fruit and vegetable consumption is evaluated based on the 2008 surveillance data of the Belgian Federal Agency for the Safety of the Food Chain (FASFC).Results (deterministic and probabilistic approach) demonstrate that the chronic exposure of the adult population (>15 years) is generally under control, even at high or frequent consumption of fruit and vegetables. For most of the pesticide residues studied, the exposure is one hundred times lower than the ‘acceptable daily intake’ or ADI. With regard to children (2–5 years) who consume regularly or large amounts of fruit and vegetables, there are however, indications that for some pesticides the ADI can be exceeded. Nevertheless, due to the large uncertainty in these calculations, a more detailed study is required for this vulnerable group of consumers. In addition, it was demonstrated that washing and peeling of fruit and vegetables result in an exposure that is probably five to six times lower.     

Effect of collection time on chemical composition of the essential oil of Foeniculum vulgare subsp. piperitum growing wild in Turkey

The essential oils of Foeniculum vulgare subsp. piperitum were subjected to detailed GC-MS analysis in order to determine possible similarities and differences in their chemical compositions, depending on growth years (2001 and 2002). In both oils, methyl chavicol (40.29 and 21.69%), limonene (17.66 and 22.24%), fenchone (16.90 and 12.98%), α-pinene (1.86 and 34%) and α-phellandrene (2.30 and 2.74%) were the main components, respectively. A total of 32 components were identified accounting for 85.01 and 67.14% of the oils of F. vulgare, respectively. The main characteristic of the oils is the high content of the limonene, fenchone and estragol. Our findings indicated that the oil of Turkish bitter fennel belonged to methyl chavicol rich type.     

Combination of mass spectrometry and site-specific NMR isotope analyses in the characterisation of amino acids

Experimental strategies have been developed which make amino acid probes accessible to the NMR study of site-specific natural isotope fractionation. A multi-isotope approach, based on combined mass spectrometry determination of hydrogen-, carbon- and nitrogen-overall isotope contents and on ²H-NMR determination of site-specific hydrogen isotope ratios, shows that relatively wide ranges of variation are exhibited by the isotopic parameters of glutamic acid, aspartic acid, alanine, proline and lysine samples from different origins. Moreover, relatively large deviations with respect to a random distribution of deuterium among the molecular sites are quantified and compared. A noticeable enantiomeric imbalance at the methylenic site adjacent to the chiral centre is also detected in natural samples of L -glutamic and L -aspartic acids in particular. The results are analysed in terms of filiation criteria and technological effects. It is shown in particular that the C₃ or C₄ metabolic origin of the raw materials utilised in fermentation processes can be recognised. Principal component analyses involving the two mean isotopic variables δ¹³C and δ¹⁵N and the three site-specific variables (D/H)_x (D/H)_β and (D/H)_γ associated with positions α, β and γ of glutamic acids, for example, are helpful for interpreting the main discriminating factors. This approach provides the basis for new applications to origin recognition of fundamental constituents and metabolites of plant or animal species.