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The preparation of trans-[Pt(dmso)2ClMe] (2) and cis-[Pt(dmso)2Me2] (3) from cis-[Pt(dmso)2Cl2] (1) and SnMe4 has been reexamined (dmso = dimethyl sulfoxide). The information obtained from experimental and DFT studies has permitted the improvement of previously reported methods for the synthesis of both complexes in terms of reaction times, reaction yields, and atom economy. These studies show that complex 1 reacts with a first equiv of SnMe4 to form trans-[Pt(dmso)2ClMe] (2) as an intermediate that quickly reacts with a second equiv of SnMe4 to yield cis-[Pt(dmso)2Me2] (3). When only 1 equiv of the organostannane reagent is added, the comproportionation of 3 with the excess of unreacted 1 leads the reaction back to the formation of trans-[Pt(dmso)2ClMe] (2). The mechanism of this comproportionation has been studied using DFT calculations.

Light (Tlight), middle (Tmiddle) and severe (Tsevere) torrefaction processes by TGA in woody biomass were evaluated in relation to devolatilization rate (Drate), maximum devolatilization rate (DRmax), temperature at the level of 50% weight loss (T50), rate of weight loss at T50 (R50) and weight loss during torrefaction (Wloss-DT). The relationship between these parameters with cellulose, lignin and extractives content was established. The TGA and devolatilization curves showed that DRmax was of 4.16, 1.80 and 0.70%/min for Tlight, Tmiddle and Tsevere respectively. Wloss-DT in Tlight ranges between 3 and 6%, between 9 and 14% in Tmiddle and from 11 to 16% in Tsevere. G. arborea showed the highest Wloss-DT, with 29.10% for Tsevere and C. Lusitania and T. grandis the lowest Wloss-DT, with 15% for Tsevere. The duration of Dmax was of 5 min in Tlight and Tmiddle and 6 min in Tsevere. Cellulose, lignin and carbon presented statistically significant correlations with R50, T50, Wloss-DT and DRmax. Ash content was correlated with Wloss-DT and DRmax in all torrefaction condition. Extractives in dichloromethane was significantly in many parameters. We conclude that the torrefaction of different woody species can be optimized as biomass feedstocks with a specific temperature and time of torrefaction.

Torrefaction can increase the energy yield of biomass for better utilization in bioenergy, but chemical changes occur during the pretreatment process. Wood residues of Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea were torrefied for three different time periods (8, 10, and 12 min) and three different temperatures (200, 225, and 250 °C). The mass loss, net calorific value, ash, volatiles, lignin, cellulose, extractives, and infrared spectra were evaluated. The results showed that the mass loss in torrefied biomass varied between 10% and 70%, ash content varied between 0.19 and 7.00%, and volatiles content varied between 63 and 85%. Net calorific value values varied between 17 and 23 MJ/kg, increasing with the increased torrefaction temperature. Cellulose varied between 49.85 and 67.57%. Lignin varied between 27.33 and 41.09%. The extractives varied between 3.70 and 16.86%. The change in the ratio of intensity (RI) for the bands identified using FTIR analyses showed that large changes occurred in hemicellulose components. The multivariate analysis showed that lignin, ash, extractives in hot water, volatiles, and mass loss were the variables that contributed most. The analysis of all these variables showed that torrefaction at 250 °C for 12 min presented the greatest biomass degradation. Torrefaction at 200 °C and 225 °C for 8, 10, and 12 min was optimal for thermal treatment of the biomass of these woody species.

Woody biomasses from five fast-growth plantations of Costa Rica were evaluated in relation to thermal degradation characteristics and devolatilisation rate (Drate) using thermogravimetric analysis (TGA). The relationship between TGA parameters and Drate with content of cellulose, lignin and extractives were established. The results indicate that during degradation, the five woody biomass types (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis and Vochysia ferruginea) show different temperatures and residual mass, as well as different Drate of the polymers conforming them, indicating that each biomass type has unique pyrolysis characteristics. The difference in these parameters is influenced by extractives content, and a little effect is presented due to lignin content, cellulose content and ash composition. A greater amount of extractives decreases the degradation temperatures of the different biomass components, although the residual mass was scarcely affected and if so, a positive correlation was presented. Extractives also affected the Drate more significantly than cellulose, lignin and macro- or micro-nutrients contents. Moreover, the Drate of cellulose was more affected by the extractives content than was Drate of hemicellulose, indicating a higher degree of association of extractives with cellulose than hemicellulose. In this concern, the higher the amount of extractives, the lower the Drate of cellulose.

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture content, water absorption, and compression force of torrefied biomass pellets of five wood species (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) under three torrefaction temperature conditions (light, middle, and severe) and three torrefaction times (8, 10, and 12 min). The results showed that the bulk density of the pellets was 0.90–1.30 g/cm3. The density variation of the pellets was higher with torrefaction at 250 °C. The moisture content decreased with increasing torrefaction temperature from 3% to 1%. Water absorption was lower in the pellets torrefied at 250 °C. The compression force was lower in the pellets torrefied at 250 °C with approximate loads of 700 N. Based on the above results, it was concluded that pellets made with biomass torrefied at 200 °C have better energy properties and evaluated properties. According to these results, pellets fabricated with the torrefied biomass of tropical species can be used in stove, gas, and hydrogen production because the pellet presents adequate characteristics.

Artículo científico Trametes versicolor and Pleurotus ostreatus were used for the biopulping from pineapple leaf fiber (PALF). PALF substrate was subjected to T. versicolor for 2 to 6 weeks and to P. ostreatus for 4 to 8 weeks. The yields, holocellulose and lignin contents, and extractives in ethanol-toluene mixture and in sodium hydroxide (NaOH) solution were evaluated. Fourier transform infrared spectroscopy (FTIR) spectra, thermogravimetric analysis (TGA), and color studies by L*a*b* systems were used for sample analysis. The results showed that the pulp yield was 55% to 70% with P. ostreatus and 35% to 50% with T. versicolor. Longer colonization periods increased the amount of holocellulose and decreased the amount of lignin and extractives in ethanol-toluene and NaOH solution. TGA showed an increase in intensity associated with cellulose, and the observed inflexion was attributed to lignin, which showed a tendency to fade. The FTIR spectrum showed high intensity between 3100 cm-1 and 3600 cm-1 (cellulose) and decreased intensity at 1730 cm-1 (lignin). For both fungi, the pulp color produced an increase in L* color parameter and decreased in yellowness, while little variation was observed in redness. The most appropriate colonization period was 5 weeks for P. ostreatus and 4 weeks for T. versicolor.

The addition of titanium dioxide nanoparticles (TiO2 nanoparticles) to a water-based varnish used for finishing tropical woods was studied. Three different concentrations of TiO2 nanoparticles (0%, 1.0%, and 1.5%) were evaluated. The nanoparticles were characterized by means of the transmission electron microscopy and an X-ray diffractometer. The varnish prepared was evaluated for its viscosity, adhesion of the film to the wood, water absorption, and the effects of natural weathering on the color and quality of the varnish. It was found that viscosity decreases as the concentration of TiO2 nanoparticles increases, while no variation was found in the thickness of the film. Except for Gmelina arborea and Tectona grandis, the adhesion was not statistically affected. It was found that, in the 9 species tested, incorporation of TiO2 nanoparticles decreased the values of water absorption. The evaluation of natural weathering showed that the varnish with no added TiO2 nanoparticles degraded completely after 1 year of weathering exposure, while the modified varnish film endured. Less color change was observed in lumber treated with the varnish containing TiO2 nanoparticles. The best performance of the varnish in the nine tropical woods used was observed when TiO2 nanoparticles were added at 1.5% concentration.

Se presenta la evaluación de la combustión de pellets fabricados con dos cultivos forestales y ocho cultivos agrícolas en Costa Rica utilizando un quemador doméstico de 50 Kw/h. Se evaluó las características de la biomasa, las temperaturas en la salida del quemador y en la chimenea, las emisiones (O2, CO2, CO, NO, NO2, NOx y SO2), las pérdidas de calor y la eficiencia. La temperatura de salida en el quemador varió entre 400 °C y 613 °C y la temperatura en la chimenea estuvo desde los 205 a 322 °C, la temperatura más baja correspondió a Phyllostachys aurea y la mayor al residuo de la palma de aceite. Tectona grandis presentó la mayor variación de la temperatura, mientras que Cupressus lusitanica obtuvo la menor variación. Los dos cultivos forestales presentaron los menores valores de emisiones. En la eficiencia en combustión el mejor cultivo fue Gynerium sagittatum, mientras que las especies forestales presentaron una eficiencia intermedia entre los cultivos analizados.

The present study shows the results of the evaluation of the pellets made from two forestry crops and eight agricultural crops in Costa Rica by employing a 50 kW domestic stove. Methods: The following variables were evaluated: flame outlet and flue gas temperatures and emissions (CO2, CO, NO, NO2, NOx and SO2). Results: It was found that the pellet consumption varies from 2.5 to 3.4 kg/h, where the former corresponds to Tectona grandis and the latter to the mesocarp oil palm fruit. Flame outlet temperature varied from 400 to 623 °C and flue gas temperature varied from 205 to 322 °C, where the lowest temperature corresponds to Phyllostachys aurea and the highest to the oil palm residue. T. grandis showed the highest variation in temperature, while Cupressus lusitanica showed the lowest variation. A result that stands out in the measurement of emissions is that the two forestry crops show the lowest values. Conclusions: Different type of pellet produces different behaviour in domestic stove. Gynerium sagittatum and C. lusitanica were with greater heat generation and Pennisetum purpureum and T. grandis with the lowest heat generation. © 2015, Springer Science+Business Media Dordrecht.

https://www.scopus.com/inward/record.url?eid=2-s2.0-84940754701&partnerID=40&md5=1821f371fbf5ca780f855a8c5c875e01 Multiwall carbon nanotubes (MWCNTs) functionalized with hydroxyl groups (MWCNTs-OH) have been incorporated into polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives utilized in tropical wood gluing. The Raman spectroscopy, the atomic force microscopy (AFM), and transmission electron microscopy (TEM) were used to describe the MWCNTs-OH. The adhesives were evaluated in three concentrations of MWCNTs-OH: 0% (control), 0.05%, and 0.1%. The evaluation included color, the distribution of MWCNTs-OH by TEM and AFM, thermal stability and viscosity of the adhesives, and shear strength (SS) of the glue line for nine tropical woods. AFM and TEM confirmed interaction of MWCNTs-OH with adhesives. The viscosity of the PVAc adhesive increases with added MWCNTs-OH. The incorporation of MWCNTs-OH in PVAc and UF resin produces wood adhesives with less brightness, less yellowness, and increased redness. The nanotubes in the adhesive improved the thermal stability of the composites and increased the entropy factor and energy of activation in the kinetic decomposition of the resin. In relation to SS, MWCNTs-OH in any of the two concentrations had no significant effect on SS in dry condition in half of the species studied glued with PVAc adhesive, whereas, for UF-adhesive, the SS and percentage of wood failure improved in most of the 9 species studied.