Nanostructured Ni-containing spinel oxides for the dry reforming of methane: Effect of the presence of cobalt and nickel on the deactivation behaviour of catalysts

Nanostructured Ni-containing spinel oxide catalysts were obtained using a nanocasting method. Analyses by XRD, TEM, TPD-CO₂ and TPR showed that Ni^o and/or Co^o entities with high accessibility to CH₄ and CO₂ were responsible for high catalytic performance in the dry reforming of methane. The NiCo (Co^o and Ni^o dispersed on NiAl₂O₄) and NiAl (Ni^o dispersed on NiAl₂O₄) species were highly active for CH₄ conversion, whereas Ni^o dispersed on either Fe₃O₄–Co₃O₄ or CeO₂–NiAl₂O₄ provided a lower catalytic performance due to active phase degradation. The higher activity exhibited by NiAl compared to NiCo was related to the higher activity of nickel for CO₂ decomposition, while its remarkable stability seemed to be due to the presence of well dispersed nanoparticles involved in long-term conversion because they produced non-deactivating carbon deposits, as suggested by Raman analyses.     

The use of 2D NMR to study β-cyclodextrin complexation and debittering of amino acids and peptides

This work fully demonstrated the formation of amino acids complexes with β-cyclodextrin (β-CD) by the method of nuclear magnetic resonance with the rotating frame Overhauser effect spectroscopy (ROESY) and diffusion ordered spectroscopy (DOSY) techniques. The tested amino acids display the following decreasing order of affinity for β-CD: tryptophane > tyrosine > phenylalanine > proline > histidine > isoleucine. The influence of complexation on taste perception was determined with a trained panel to qualify taste alterations of single amino acids and quantify the debittering of soy protein hydrolysate by β-CD complexation. The results showed that β-CD complexation is effective for modifying single amino acids taste perception and debittering soy protein hydrolysate. Bitterness sensation of the latter is reduced by 90% when 5% β-CD was added, thus β-CD is recommended as a prospective additive for masking bitter taste of new functional food products.     

Modification of eucalyptus pulp fiber using silane coupling agents with aliphatic side chains of different length

The objective of this work was to evaluate the effect of three silane coupling agents with different aliphatic chain lengths on the hydrophobicity of eucalyptus pulp fiber. The three silanes coupling agents used (isobutyltrimethoxysilane, methyltrimethoxysilane, and n‐octyltriethoxysilane [OTES]) were each tested at three concentrations. Scanning electron microscopy coupled with energy dispersive spectroscopy revealed that the silane coupling agents markedly increased the Si content of the treated fibers. The Si distribution was not completely homogenous but was abundant in the treated samples. The treated fibers had higher contact angles for water and lower moisture adsorption than the control. Of the coupling agents tested, OTES treated fibers had the highest moisture resistance. This was likely due to the greater chain length of the aliphatic side group coupled to OTES. The use of silane coupling agents with alkyl side chains could improve the functional properties of pulp fiber and increase its compatibility with hydrophobic polymers. POLYM. ENG. SCI., 55:1273?1280, 2015. © 2015 Society of Plastics Engineers     

Impact of aliphatic amine comonomers on DGEBA epoxy network properties

This study characterized the mechanical and thermal properties of the oligomer‐based formulations of the diglycidyl ether of bisphenol A (DGEBA) cured with series aliphatic amines (triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and O,O bis (2‐aminopropyl propylene glycol) (Jeffamine D230) with different functionalities in the glassy state. Impact Izod and three‐point bending tests were conducted to determine the networks' impact energy (E_i), elasticity modulus (E_y), yield stress (σ_y) and fracture toughness (K_IC) values. The same three‐point bending mode was also employed to characterize the systems' thermo‐mechanical properties (DMA) and storage modulus (E') and damping modulus (tan δ = E"/E') values. The DGEBA/D230 network showed greater flexibility, maximum impact energy, higher fracture toughness, and a lower yield stress than the DGEBA/TETA and DGEBA/TEPA networks. The fracture behavior of these epoxy systems was correlated to the molecular weight between the crosslink points, M_c, and the plastic zone size (r_p) at the crack tip carved in the samples. The DGEBA/D230 network had the highest storage modulus and tan δ intensity, together with higher toughness and deformation during the network's fracture. These results were a consequence of the structural characteristics of comonomers, including their chain segment flexibility, molecular weight between crosslink points and functionality. POLYM. ENG. SCI., 54:2132–2138, 2014. © 2013 Society of Plastics Engineers     

BEM modeling of saturated porous media susceptible to damage

This paper deals with the numerical analysis of saturated porous media, taking into account the damage phenomena on the solid skeleton. The porous media is taken into poro-elastic framework, in full-saturated condition, based on Biot’s Theory. A scalar damage model is assumed for this analysis. An implicit boundary element method (BEM) formulation, based on time-independent fundamental solutions, is developed and implemented to couple the fluid flow and two-dimensional elastostatic problems. The integration over boundary elements is evaluated using a numerical Gauss procedure. A semi-analytical scheme for the case of triangular domain cells is followed to carry out the relevant domain integrals. The non-linear problem is solved by a Newton-Raphson procedure. Numerical examples are presented, in order to validate the implemented formulation and to illustrate its efficacy.