Kinetics of biofuel generation from deodorizer distillates derived from the physical refining of olive oil and squalene recovery

The recovery of squalene from deodorizer distillate derived from the physical refining of olive oil was evaluated by combining pressurized acidic esterification in a closed system with vacuum distillation. Esterification was carried out at 341, 359, 366, 391 and 395 K. The reaction at 395 K was found to be satisfactory as it decreased the acid value by 99.21% and generated a FAME concentration of 67.53% within 1 h. In order to demonstrate that the generation of FAME from deodorizer distillate was mainly due to the transformation of FFA, the reaction extent, which characterizes the reaction and simplifies calculations, was evaluated for FFA removal and the generation of FAME. Subsequent vacuum distillation allowed the separation of one fraction rich in FAME (94%), which can be used as a biofuel and accounted for 85% of the initial mass, and another fraction that was rich in squalene (78%) and may be used for manufacturing pharmaceutical products. The global squalene yield was 117 g kg⁻¹ initial deodorizer distillate.     

Ammonia decomposition kinetics over LiOH-promoted, α-Al2O3-supported Ru catalyst

A LiOH-promoted Ru-based catalyst was recently reported to have a high TOF of 17.7 s⁻¹ at 623 K, compared to 2.7 s⁻¹ for an un-promoted Ru-based catalyst, and has been reproduced for this study to develop further understanding of the catalyst activity under a range of conditions. The kinetic values were calculated using a Temkin-Pyzhev-like power law rate expression model. Reaction orders, pre-exponential factors (A) and activation energies (E) were calculated for two temperature ranges, 623–748 K, and 748–873 K. The TOF of this catalyst at 623 K is not similar to that previously reported, being only 1.6 s⁻¹ in this study. A follow-up CFD analysis supports the fact that the kinetic model effectively describes performance of the catalyst at a range of temperatures and pressures, and can be used in the future on similar catalysts. H₂ partial pressure has an inhibitory effect on the rate of decomposition of NH₃ at all temperatures, not just near or below 673 K as previously proposed in the literature, however equilibrium decomposition is still possible with sufficient catalyst loading.     

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H₂ absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.     

Effects of trimesic acid-Ni based metal organic framework on the hydrogen sorption performances of MgH2

A metal-organic framework based on Ni (II) as metal ion and trimasic acid (TMA) as organic linker was synthesized and introduced into MgH₂ to prepare a Mg-(TMA-Ni MOF)-H composite through ball-milling. The microstructures, phase changes and hydrogen storage behaviors of the composite were systematically studied. It can be found that Ni ion in TMA-Ni MOF is attracted by Mg to form nano-sized Mg₂Ni/Mg₂NiH₄ after de/rehydrogenation. The hydriding and dehydriding enthalpies of the Mg-MOF-H composite are evaluated to be −74.3 and 78.7 kJ mol⁻¹ H₂, respectively, which means that the thermodynamics of Mg remains unchanged. The absorption kinetics of the Mg-MOF-H composite is improved by showing an activation energy of 51.2 kJ mol⁻¹ H₂. The onset desorption temperature of the composite is 167.8 K lower than that of the pure MgH₂ at the heating rate of 10 K/min. Such a significant enhancement on the sorption kinetic properties of the composite is attributed to the catalytic effects of the nanoscale Mg₂Ni/Mg₂NiH₄ derived from TMA-Ni MOF by providing gateways for hydrogen diffusion during re/dehydrogenation processes.     

Reduction of oxide scale on hot-rolled steel by hydrogen at low temperature

This study was carried out with an intention to remove the oxide scale on hot-rolled steel by gaseous reduction instead of traditional acid pickling method with an aim to reduce the pollution. The reduction of iron oxide scale by hydrogen–argon mixture was studied by thermogravimetric tests in the temperature range of 370–550 °C. The rate controlling process was discussed according to the Avrami–Erofe'ev equation generalized method. The analysis suggests that the reduction of scale is controlled by two- and/or three-dimensional growth of nuclei in the whole temperature range investigated. The apparent activation energy exhibit a sudden decrease from 78.8 to 31.8 kJ/mol at temperature higher than 410 °C. Morphological structure of the reduced scale was investigated by scanning electron microscope.     

Investigating possible kinetic limitations to MgB2 hydrogenation

An investigation is reported of possible kinetic limitations to MgB₂ hydrogenation. The role of H–H bond breaking, a necessary first step in the hydrogenation process, is assessed for bulk MgB₂, ball-milled MgB₂, as well as MgB₂ mixed with Pd, Fe and TiF₃ additives. The Pd and Fe additives in the MgB₂ material exist as dispersed metallic particles in the size range ~5–40 nm diameter. In contrast, TiF₃ reacts with MgB₂ to form Ti metal, elemental B and MgF₂, with the Ti and the MgF₂ phases proximate to each other and coating the MgB₂ particulates with a film of thickness ~3 nm. Sieverts studies of hydrogenation kinetics are reported and compared to the rate of H–H bond breaking as measured by H-D exchange studies. The results show that H–H bond dissociation does not limit the rate of hydrogenation of MgB₂ because H–H bond cleavage occurs rapidly compared to the initial MgB₂ hydrogenation. The results also show that surface diffusion of hydrogen atoms cannot be a limiting factor for MgB₂ hydrogenation. Instead, it is speculated that it is the intrinsic stability of the B–B extended hexagonal ring structure in MgB₂ that hinders the hydrogenation of this material. This supposition is supported by B K-edge x-ray absorption measurements of the materials, which showed spectroscopically that the B–B ring was intact in the material systems studied. The TiF₃/MgB₂ system was examined further theoretically with reaction thermodynamics and phase nucleation kinetic calculations to better understand the production of Ti metal when TiB₂ is thermodynamically favored. The results show that there exist physically reasonable ranges for which nucleation kinetics supersede thermodynamics in determining the reactive pathway for the TiF₃/MgB₂ system and perhaps for other additive systems as well.     

Effects of MWCNTs on improving the hydrogen storage performance of the Li3N system

In this paper, the influence of multi-walled carbon nanotube (MWCNT)-doping on the hydrogen storage properties of the Li₃N system was systematically investigated. Compared with the pure Li₃N sample, the MWCNT-doped Li₃N sample shows faster hydrogen absorption and desorption kinetics and a drastically improved cycling stability. Along with increasing MWCNT content, the hydrogen storage improvement becomes more apparent. When the MWCNT doping level reaches 10 mol%, the enhancement effect is significant. The improved hydrogen storage properties of the Li₃N system by MWCNT-doping can be reduced to the physical effect of ball milling, the increased specific surface area and large pores as well as the good thermal conductivity of MWCNTs.     

Application of hydrophobic and magnetic plastic particles for enhanced flotation recovery

The effect of hydrophobic and magnetic plastic particles having a contact angle of around 83° on flotation performance was evaluated using coal particles of varying degrees of floatability. The magnetic plastic material were recovered by a low intensity magnetic separator and recycled back to the flotation feed for re-use. Flotation rate tests conducted on coal using a conventional cell proved that combustible recovery and flotation rate were significantly enhanced with the addition of the plastic particles, especially for difficult-to-float coals, which was corroborated by flotation column tests. Carrying capacity and particle size-by-size flotation tests further showed that the magnetic plastic particles preferentially increased the recovery of coarse particles by as much as 35 absolute percentage points due to froth stabilization which reduced the selective detachment of coarse and/or weakly hydrophobic particles. The enhanced flotation recovery was attributed to the influence on liquid drainage rate in the froth zone, froth stability, bubble coalescence and flotation rates.