Mechanistic Insight in the Ethane Dehydrogenation Reaction over Cr/Al2O3 Catalysts

A Cr/Al₂O₃ alkane dehydrogenation catalyst exhibits a maximum in ethylene yield during an ethane dehydrogenation cycle. Isotopic labelling experiments with monolabelled ¹³C-ethane and deuterium were used to elucidate whether the initial activity increase could be due to formation of an active, larger hydrocarbon intermediate on the surface. The results strongly indicate that this is not the case, and instead point to a traditional reaction cycle involving adsorption of ethane to form an ethyl species, followed by desorption of ethene and hydrogen. Transient kinetic data suggest that ethane adsorption is the rate-determining step of reaction.     

Cathodic disbonding of paint films-transport of charge

Cathodic disbonding and charge transport through paint films were studied as a function of polarization potential, temperature, dry-film thickness and cation type in the electrolyte. It was found that both the disbonding rate and the charge transport were linearly related to the polarization potential. The activation energy for the disbonding process and the charge transport were quite different. The disbonding rate was linearly related to the dry-film thickness and was dependent on the cation type in the electrolyte. This was not the case for the charge transport. The results indicate a rate controlling factor for the disbonding process involving transport of cations through the film where the film is already disbonded. A fundamental difference in the conductive properties of the paint film on either side of the disbonding front is also proposed.     

A Comparison of Narrative Exposure Therapy, Supportive Counseling, and Psychoeducation for Treating Posttraumatic Stress Disorder in an African Refugee Settlement.

Little is known about the usefulness of psychotherapeutic approaches for traumatized refugees who continue to live in dangerous conditions. Narrative exposure therapy (NET) is a short-term approach based on cognitive-behavioral therapy and testimony therapy. The efficacy of narrative exposure therapy was evaluated in a randomized controlled trial. Sudanese refugees living in a Ugandan refugee settlement (N = 43) who were diagnosed as suffering from posttraumatic stress disorder (PTSD) either received 4 sessions of NET, 4 sessions of supportive counseling (SC), or psychoeducation (PE) completed in 1 session. One year after treatment, only 29% of the NET participants but 79% of the SC group and 80% of the PE group still fulfilled PTSD criteria. These results indicate that NET is a promising approach for the treatment of PTSD for refugees living in unsafe conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Natural rubber (Hevea Brasiliensis)-based quasi-solid electrolyte as a potential candidate for arresting recombination and improving performance in aqueous dye-sensitized solar cells

Journal of Materials Science: Materials in Electronics - We successfully fabricated dye sensitized solar cells (DSSCs) employing a quasi-solid state electrolyte based on pristine insulator natural...     

Methanol Conversion to Hydrocarbons (MTH) Over H-ITQ-13 (ITH) Zeolite

Product flexibility is key to meeting fluctuating chemicals demands in the future. In this contribution, the methanol to hydrocarbons (MTH) reaction was investigated over two Ge-containing H-ITQ-13 samples, one with needle-like (H-ITQ-13(N), with (Si+Ge)/Al) = 42) and another with plate-like (H-ITQ-13(P), with (Si+Ge)/Al > 100) morphology. The samples were characterised using XRD, BET, SEM/EDS and FTIR spectroscopy, and their MTH performance was compared with the performance of H-ZSM-5 and H-ZSM-22. Similar specific surface areas (413 and 455 m² g^?1 for H-ITQ-13(N) and (P), respectively) and similar acid strength (Δν ~ ?327(?310) cm^?1) was observed for the two H-ITQ-13 samples. Testing of H-ITQ-13(N) at weight hourly space velocity (WHSV) = 2–8 h^?1 at 350–450 °C revealed that C₅₊ alkenes were the main products (35–45 % selectivity at 400 °C), followed by propene and butene. A low but significant selectivity for aromatic products was observed (6–8 % selectivity at 400 °C). Product selectivity was found to be independent of deactivation. The methanol conversion capacity of H-ITQ-13(N) was 120–150 g methanol g^?1 catalyst at 400 °C. Testing H-ITQ-13 at high (30 atm) and ambient pressure, respectively, at 350 °C showed that a high pressure led to enhanced C₅₊ selectivity, but close to a tenfold decrease in methanol conversion capacity. H-ITQ-13(P) was tested at 400 °C and 2 h^?1. It gave lower conversion than H-ITQ-13(N). Furthermore, when compared at the same conversion level, H-ITQ-13(P) gave higher C₅₊ alkene selectivity, lower aromatics selectivity, and a higher propene to ethene ratio than H-ITQ-13(N). The H-ITQ-13 samples yielded a product spectrum intermediate of H-ZSM-22 and H-ZSM-5. The effluent product cut-off of H-ITQ-13 was similar to that of H-ZSM-5 with tetramethylbenzene as the largest significant product, while H-ZSM-22 produced mainly linear and branched alkenes. The lifetime of H-ITQ-13(N) was clearly enhanced compared to H-ZSM-22, but inferior to H-ZSM-5.     

Trivalent chromium removal from tannery effluent using kaolin‐supported bacterial biofilm of Bacillus sp isolated from chromium polluted soil

BACKGROUND: Bacterial strains belonging to the genus Bacillus, isolated from Cr‐ polluted soil (tannery sludge) were employed as consortium for Cr(III) removal from tannery effluents. Kaolin clay, a natural adsorbent, was used as supporting material for bacterial biofilm formation. The use of clay‐supported bacterial biofilm has not previously been employed for the treatment of tannery effluents containing Cr(III) salt. RESULTS: Commercial tannery effluent containing 1000 ppm initial metal ion concentration was treated in stages. The initial Cr(III) concentration of 1000 ppm was brought down to 2 ppm, a permissible level for discharge, after the fourth stage. The bacterial isolates were found to be Bacillus subtilis VITSCCr01 and Bacillus cereus VITSCCr02 by 16s rRNA gene sequencing. Batch assay and confocal laser scanning microscopy results revealed the role of kaolin as a support material in biofilm formation. Best fit was obtained with the Freundlich adsorption isotherm. The mechanism of sorption was confirmed by Fourier transform infrared (FT‐IR) spectroscopy and scanning electron microscopy–energy dispersive X‐ray spectroscopy (SEM‐EDS). CONCLUSION: Cr(III) removal from tannery effluent using low cost adsorbents such as kaolin and bacteria proved to be effective for metal concentrations ?1000 ppm; this is normally not possible using conventional treatment methods. This work has demonstrated feasible sorption of Cr(III), especially during post‐tanning operations. Copyright © 2011 Society of Chemical Industry     

Methane Steam Reforming Over Ni/NiAl2O4 Catalyst: The Effect of Steam-to-Methane Ratio

Methane steam reforming was investigated over a Ni/NiAl₂O₄ catalyst at steam-to-carbon ratios (S/C) = 0.27?C6.3 at 873 K. Increasing S/C ratios led to increasing, then stable, and finally decreasing, methane conversion, suggesting that the rate-determining step of reaction is a surface reaction between two species competing for the same active site.     

Designing Heterogeneous Catalysts by Incorporating Enzyme-Like Functionalities into MOFs

Everyone who works within the field of catalysis draws inspiration from the amazing functionality of nature’s catalysts, the enzymes. It is particularly the mild conditions that these catalysts are able to operate at and the selectivity that they demonstrate that make these materials dream targets for scientists involved in the art of synthesizing homogeneous and heterogeneous industrial catalysts. But enzymes also have their weak points; in particular their low thermal stability and their often too slow reaction rates for an economical industrial process are problems that have to be overcome. The obvious solution would be to copy the catalytic active center into a robust open framework. A key property of an enzyme is its selectivity; this property is partly regulated by steric constraints surrounding the catalytically active site. The microporous zeolite based catalysts in some cases show impressive selectivity based on the geometrical constraints imposed by the size and shape of the regular channels in these crystalline silicate and alumino-phosphate based structures, and enzyme-like properties have been claimed but the pure inorganic nature of the selective internal surface in these materials makes it impossible to mimic many important enzymatic properties. The new generation of microporous materials, Metal Organic Frameworks (MOFs) are hybrids of organic and inorganic structures. This dualistic nature offers an unprecedented flexibility in the possibility to incorporate both organic and metallic functional groups into the ordered crystalline lattice and thereby opening up for a much greater possibility to copy structural motifs known from enzymes into much simpler but also more stable open structures. Several groups are working on development of new catalysts by this approach. Here we will illustrate this approach with structures that mimic anhydrase and C–H activation.     

Doped oxides of cerium as inorganic colorants

The colour of inorganic colorants is based on metal ions such as cadmium, lead, chromium or cobalt, the majority of which are unfortunately potentially toxic. Thus, there is in a need to introduce alternative metal or metal oxides, which would be environmentally friendly and economically viable as a replacement for potentially toxic inorganic colorants. Rare earth-based colorants offer an additional opportunity for the development of optically pure colours. In this study, a replacement for potentially toxic colorants has been sought through the use of a rare earth metal ion, cerium. Appropriate doping of cerium oxides with molybdenum and iron gives an orange–red colorant. The conditions ideal for optimal colour have been standardised and the resultant colorant characterised through powder X-ray diffraction techniques, particle size measurement, etc. The colorants exhibit good hiding power and tinting strength.     

Solid waste removes toxic liquid waste: adsorption of chromium(VI) by iron complexed protein waste

The leather processing industry generates huge amounts of wastes, both in solid and liquid form. Fleshing from animal hides/skins is one such waste that is high in protein content. In this study, raw fleshing has been complexed with iron and is used for removal of chromium(VI). The effect of pH and the initial concentration of chromium(VI) on the removal of Cr(IV) by iron treated fleshing is presented. Iron treatment is shown to greatly improve adsorption of the fleshing for hexavalent chromium. The ultimate adsorption capacity of iron treated fleshing is 51 mg of chromium(VI) per gram of fleshing. That of untreated fleshing is 9 mg/g such that iron treatment increases the adsorption capacity of fleshing by 10-fold. The measured adsorption kinetics is well described by a pseudo-second-order kinetic model. The uptake of chromium(VI) by fleshing is best described by the Langmuir adsorption isotherm model. X-ray photoelectron spectroscopic (XPS) studies show that the iron is incorporated into the protein matrix. Shifts in XPS spectra suggest that dichromate binding occurs with iron at active adsorption sites and that iron treated fleshing removes chromium(VI) without reducing it to chromium(III).