Recycling GTL catalysts—A new challenge

The Fischer Tropsch synthesis of motor fuel from natural gas on a large scale may become significant in the near future for economic and environmental reasons. This process requires solid-phase catalysts containing large amounts of cobalt (catalyst) and traces of platinum group metals or rhenium (promoter). The economic data presented in this paper shows why recycling of those metals will be mandatory. Several recycling processes will be presented along with their technical challenges, most of which can be handled by Umicore using its know how and experience in the recycling of cobalt and the precious metals.     

GPCR antitarget modeling: pharmacophore models for biogenic amine binding GPCRs to avoid GPCR-mediated side effects

G protein-coupled receptors (GPCRs) form a large protein family that plays an important role in many physiological and pathophysiological processes. However, the central role that the biogenic amine binding GPCRs and their ligands play in cell signaling poses a risk in new drug candidates that reveal side affinities towards these receptor sites. These candidates have the potential to interfere with the physiological signaling processes and to cause undesired effects in preclinical or clinical studies. Here, we present 3D cross-chemotype pharmacophore models for three biogenic amine antitargets: the alpha(1A) adrenergic, the 5-HT(2A) serotonin, and the D2 dopamine receptors. These pharmacophores describe the key chemical features present within these biogenic amine antagonists and rationalize the biogenic amine side affinities found for numerous new drug candidates. First applications of the alpha(1A) adrenergic receptor model reveal that these in silico tools can be used to guide the chemical optimization towards development candidates with fewer alpha(1A)-mediated side effects (for example, orthostatic hypotension) and, thus, with an improved clinical safety profile.     

Study of sulfonic acid esters from 1→4‐, 1→3‐, and 1→6‐linked polysaccharides

Sulfonic acid esters of differently linked polysaccharides including cellulose, dextran, lichenan, and pullulan were synthesized homogeneously applying N,N‐dimethylacetamide/LiCl as the solvent. The dependence of the degree of substitution (DS) on the molar ratio of repeating unit to sulfonic acid chloride and on the structure of the reagent (benzene‐, p‐toluene‐, 4‐chlorobenzene‐, 2,4‐dinitrobenzene‐, 2,4,6‐trimethylbenzene‐, and 2,4,6‐triisopropylbenzene sulfonic acid chloride), as well as on the polysaccharide, was studied. DS values in the range of 0.2–2.3 were obtained. Bulky and electron withdrawing substituents on the aromatic ring inhibited ester formation. None of the sulfonic acid chlorides applied showed distinct regioselectivity. The polysaccharide sulfonic acid esters were soluble in organic solvents depending on the type of substituent and the degree of substitution. The molecular structure of the new polymers was confirmed by elemental analysis, FTIR, and ¹³C‐NMR spectroscopy. Subsequently, nucleophilic displacement reactions were carried out, which showed that the reactivity of the primary sulfonic acid ester group was higher than that of the secondary ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2142–2150, 2006     

Chemical synthesis of a dual branched malto-decaose: a potential substrate for alpha-amylases

A convergent block strategy for general use in efficient synthesis of complex alpha-(1-->4)- and alpha-(1-->6)-malto-oligosaccharides is demonstrated with the first chemical synthesis of a malto-oligosaccharide, the decasaccharide 6,6'-bis(alpha-maltosyl)-maltohexaose, with two branch points. Using this chemically defined branched oligosaccharide as a substrate, the cleavage pattern of seven different alpha-amylases were investigated. Alpha-amylases from human saliva, porcine pancreas, barley alpha-amylase 2 and recombinant barley alpha-amylase 1 all hydrolysed the decasaccharide selectively. This resulted in a branched hexasaccharide and a branched tetrasaccharide. Alpha-amylases from Asperagillus oryzae, Bacillus licheniformis and Bacillus sp. cleaved the decasaccharide at two distinct sites, either producing two branched pentasaccharides, or a branched hexasaccharide and a branched tetrasaccharide. In addition, the enzymes were tested on the single-branched octasaccharide 6-alpha-maltosyl-maltohexaose, which was prepared from 6,6'-bis(alpha-maltosyl)-maltohexaose by treatment with malt limit dextrinase. A similar cleavage pattern to that found for the corresponding linear malto-oligosaccharide substrate was observed.     

Viscoelasticity in Polymer Films on Rigid Substrates

The viscoelasticity of two thermally crosslinked polymer coatings was examined in terms of relaxation of the applied stress after a sudden strain. Two different transient methods were utilized: flat‐ended cylindrical indentation testing of a polymer film on a rigid substrate and tensile testing of a corresponding free‐standing polymer film. The correlation between tensile and indentation tests was studied. The mechanical response of a viscoelastic layer deposited on a rigid substrate was investigated as a function of indentation depth. There was good agreement between the results of the tensile and indentation tests for thick film layers at moderate indentation depths. The findings indicate that the substrate influences the coating performance by reducing the viscous contribution to the stress response and amplifying the magnitude of the equilibrium modulus for large indentation depths. The indentation method utilized here was shown to be a potentially suitable tool for the determination of Poisson's ratio of polymer films.

     

A TDS study of D adsorption on terraces and terrace edges of graphite (0 0 0 1) surfaces

Adsorption of thermal (2000 K) D atoms on (0 0 0 1) surfaces of various highly oriented pyrolytic graphite (HOPG) and natural graphite substrates was studied under ultra high vacuum (UHV) conditions with thermal desorption spectroscopy (TDS). D chemisorption on terrace and terrace edge sites of graphite (0 0 0 1) surfaces was identified. Recombinative desorption of D adsorbed on terraces was observed between 400 and 600 K. The analysis of TD spectra from various graphite surfaces reveals the existence of three desorption states intrinsic to graphite (0 0 0 1), and proposed as being due to adsorbate structures composed of one (monomer) and two neighbouring (dimer) chemisorbed D atoms, and aggregates thereof (mixed). The dimer structure is supposed to exhibit higher stability than the monomer. Reaction of D with terrace edges leads to the formation of CD, CD₂ and CD₃-groups at edge C atoms. These groups decompose during heating between 790 and 1300 K via release of gaseous D₂ and CD_x, C₂D_x and C₃D_x-hydrocarbons.     

Sintering ZrO2/TiC Composites with TiH2: The Role of Transient Liquid Phase and of Substoichiometry

Sintering tetragonal ZrO₂ with 35 vol% TiC results in a microstructure where all grain facets are free of amorphous interfaces independent of sintering aids as TiH₂ or MgO/ Y₂O₃; grain sizes are below 1 μm. With substoichiometric TiC_1-x, a relative density of 95% and closed porosity are obtained at a lower sintering temperature than with stoichiometric TiC, but subsequent cladless hot isostatic pressing (HIP) is required to achieve 99% density. High densities of 98% accompanied by good mechanical properties become possible by pressureless sintering with the use of TiH₂. MgO/Y₂O₃ doping also promotes densification, but results in less transformable zirconia and increases the number and size of amorphous triple junctions. The consequences are a lower fracture toughness and strength.     

Low Density,Thermally Stable,and Intrinsic Flame Retardant Poly(bis(benzimidazo)Benzophenanthroline‐dione) Sponge

Low density (≤13.9 mg cm^?3), compressible poly(bis(benzimidazo)benzophenanthroline‐dione) (BBB) sponges with high temperature resistance are reported. The processing of BBB is limited due to its insolubility in organic solvents and infusibility. Therefore, the sponges are made in two steps: first, the BBB fibers are prepared by electrospinning the starting monomers with a template polymer followed by polycondensation of monomers on solid fibers at high temperature. In the second step, the BBB fibers are mechanically cut and self‐assembled from a dispersion during freeze‐drying. The use of poly(vinyl alcohol) is critical in getting self‐assembled hierarchically double‐pore‐structured, mechanically stable sponges. The sponges show very high pyrolytic stability, high compressibility (more than 92% recovery after 50% compression), very low thermal conductivity (0.028–0.038 W mK^?1), and high oil absorption capacity.     

X-Ray Absorption Spectroscopy and Morphology Study on Antiwear Films Derived from ZDDP Under Different Sliding Frequencies

X-ray absorption near-edge structure (XANES) spectroscopy has been used to characterize the chemistry of antiwear (AW) films generated from mineral base oil containing a zinc dialkyl dithiophosphate additive. These films were formed on rubbed steel surfaces with a reciprocating boundary contact using different sliding frequencies. The phosphorus L-edge XANES spectra show that these films have slightly different chemical natures. Longer chain polyphosphates were present on the steel surface prepared at the higher sliding frequencies. The surface morphology of these films was investigated using atomic force microscopy. These images show that the surface morphology of the AW films changes with the sliding frequency. Round and bigger antiwear pads were formed at a lower frequency while higher frequencies resulted in thinner films and flattened surfaces. Nanomechanical properties of these antiwear films were investigated by nanoindentation measurement and the elastic moduli extracted from force–displacement (f–d) curves are similar for all antiwear films, 100 ± 10 GPa.     

Tribological Behaviour of Sub-micron Cutting-ceramics in Contact with Wood-based Materials

New sub-μm Al₂O₃-ceramics exhibit much better mechanical and tribological characteristics than commercially available grades. Previously, the sub-μm-ceramics have been successfully tested for machining hardened steels, but there is not any scientific experience with machining wood-based materials. The aim of the presented study was to examine how these ceramics behave in dry sliding when in contact with wood-based materials and to compare their behaviour with that of hard metals and polycrystalline diamond. It has been found that the friction coefficient mostly depends on the properties of the wood-based material. Furthermore, the changes of the ceramic materials surface roughness have confirmed that the grain size-related material features affect its tribological properties.