J. Remón

Effect of using smartphones as clickers and tablets as digital whiteboards on students’ engagement and learning:

This work addresses the use of tablets and smartphones to enhance both student learning and engagement. Tablets were tested as potential substitutes for digital whiteboards, while smartphones were tested as potential survey media in the classroom using a question and answer method. Two teaching strategies were evaluated and compared: (1) traditional, which includes the use of the blackboard together with PowerPoint presentations and (2) interactive, where lessons are taught with the aid of a tablet, using interactive activities and digital materials. Measures of performance outcomes achieved with these strategies were made using the question and answer method at two points, during the classes and during the end-of-term examination. Three different question and answer methodologies were studied and compared, ranging from the very traditional method where students raise their hand to answer a question to the most modern where students use their smartphones to answer. The findings demonstrated higher outcomes with interactive lessons than with traditional learning (PowerPoint included). Tablets proved to be an effective and cheaper substitute for interactive whiteboards during lessons. The results suggested that the use of interactive procedures increased student participation. Furthermore, the students were very receptive to the use of smartphones as survey media. The use of smartphones as clickers is an interesting and instant way for both teachers and students to check students’ learning and perceived engagement. Considering that students are advanced users of smartphones and/or tablets, the use of these may be considered as more convenient than clickers. In addition, it is economically more acceptable than some other audience response systems.

Processing of Citrus Nanostructured Cellulose: A Rigorous Design‐of‐Experiment Study of the Hydrothermal Microwave‐Assisted Selective Scissoring Process

A detailed design-of-experiment (DoE) study to investigate the cause-effect interactions of three process variables, that is, temperature (120-200 °C), holding time (0-30 min), and concentration (1.4-5.0 wt %), on the processing of citrus cellulosic matter using acid-free microwave-assisted selective scissoring (Hy-MASS) is reported. Analysis of variance (ANOVA) showed that post-microwave processing, the yield of cellulosic matter (25-72 %), decomposition temperature (345-373 °C), and crystallinity index (34-67 %) were strongly affected by temperature. SEM and TEM analyses showed that the isolated cellulosic matter was heterogeneous and consisted of a mixture of micro- and nanofibers more akin to microfibrillated cellulose (MFC) at low processing temperatures and tending towards aggregated cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) at higher processing temperatures. The water holding capacity of the processed cellulosic matter (15-27 gH2O  g-1 ) was higher than the original feedstock or previously reported values. The average molecular weight of the cellulosic matter (113.6-1095.9 kg mol-1 ) decreased significantly by a factor of 10 at operating temperatures above 180 °C, invoking significant scissoring of the cellulosic chains. The process energy input and costs varied between 0.142-0.624 kWh and 13-373 € kg-1 , respectively, and strongly depended on the reaction time.A detailed design of experiment (DoE) study to investigate cause-effect interaction of three process variables: temperature (120-200 °C), holding time (0-30 min) and concentration (1.4-5.0 wt.%), on processing of citrus cellulosic matter using acid-free microwave-assisted selective scissoring (Hy-MASS) is reported. Analysis of variance (ANOVA) showed that post microwave processing, yield of cellulosic matter (25-72 %), decomposition temperature (345-373 °C) and crystallinity index (34-67%) were strongly affected by temperature. SEM and TEM analyses showed that the isolated cellulosic matter was heterogeneous comprising a mixture of micro- and nano-fibres more akin to microfibrillated cellulose (MFC) at low processing temperatures and tending towards aggregated cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) at higher temperatures. The water holding capacity of the processed cellulosic matter (15-27 g H2O·g-1) was higher than the original feedstock or previously reported values. The average molecular weight of the cellulosic matter (113.6-1095.9 kg·mol-1) decreased significantly by a factor of 10 above 180 °C, invoking significant scissoring of the cellulosic chains. The process energy input and costs varied between 0.142-0.624 kWh and 13-373 €/kg, respectively, and were found to be strongly dependent of the reaction time.

Production of fermentable species by microwave-assisted hydrothermal treatment of biomass carbohydrates: reactivity and fermentability assessments

This work addresses and compares the production of fermentable species by microwave-assisted hydrothermal treatment of cellulose and hemicellulose (from lignocellulose) and alginic acid (from macroalgae). A reliable reactivity comparison was established at different temperatures (160–210 °C), reaction times (0 and 5 min) and solid/water mass ratios (1/20 and 1/10 g/g). The nature of the carbohydrates and the hydrothermal conditions had a significant influence on the reactivity, which increased as follows: cellulose 6) and mono-/di-saccharides, carboxylic acids, ketones and furans. While the chemical composition of the hydrolysates produced from hemicellulose was not affected by the microwave operating conditions, the liquids having a high concentration of DP > 6 oligosaccharides in all cases, the microwave conditions substantially influenced the composition of the liquids produced from cellulose and alginic acid. The former contained high proportions of oligosacharides and saccharides and the latter comprised water soluble DP > 6 oligomers/oligosaccharides, saccharides, carboxylic acids and furans. The yeast Metschnikowia pulcherrima, previously demonstrated to be inhibitor tolerant and to metabolise a range of oligosacchaides, was used to assess the fermentability of the liquid fraction. All the hydrolysates produced were fermentable; their efficiency (standarised yeast biomass growth) decreasing as follows: cellulose (high/low saccharides/inhibitors proportion) > hemicellulose (high/low oligosaccharides/inhibitors proportion) > alginic acid (low/high saccharides/inhibitors proportion). Therefore, the promising results obtained in this work and the intrinsic green nature of the process make this method a very promising route for biomass valorisation, which can help to enable the development of new thermochemical and biological linked routes.

Analysis and optimisation of a microwave-assisted hydrothermal process for the production of value-added chemicals from glycerol

This work addresses an alternative and green route for glycerol upgrading recently highlighted as a potentially critical aspect of the economic and environmental viability of future biodiesel-based bio-refineries. For the first time we report the microwave-assisted hydrothermal process, examining the effects of the temperature (150–250 °C), pressure (50–120 bar), reaction time (0–2 h) and catalyst mass (5–15 wt%; Ni–Co/Al–Mg) during the upgrading of a 30 wt% glycerol solution. The global glycerol conversion and the carbon converted to gas and liquids varied by 5–54%, 0–21% and 3–42%, respectively. Increasing the temperature, reaction time and/or catalyst amount increased glycerol decomposition due to the positive kinetic effects that these variables have on the process. The pressure exerted two counteracting effects: a positive kinetic effect and a thermodynamic inhibitory influence; this latter being accounted for by the lower dielectric loss factor of water at high pressures. The liquid phase was made up of monohydric (10–62 wt%) and polyhydric (0–46 wt%) alcohols, carboxylic acids (0–9 wt%) and C3-ketones (0–80 wt%). Monohydric alcohols and C3-ketones were the most abundant compounds in the liquid when short reaction times and/or low catalyst amounts were used. An increase in these operating variables increased the concentration of polyhydric alcohols and decreased the amount of C3-ketones. The production of C3-ketones (72 wt%) could be maximised using a medium temperature (210 °C) and low pressure (50 bar) and catalyst mass (5 wt%) for a long reaction time (2 h). Around 40% of the glycerol can be purely converted to monohydric (79 wt%) and polyhydric (21 wt%) alcohols by employing a temperature of 250 °C, a pressure of 83 bar and a catalyst mass of 10 wt% for 2 h.

Liquid and Gas Biofuels from the Catalytic Re-forming of Pyrolysis Bio-Oil in Supercritical Water: Effects of Operating Conditions on the Process

This work analyses the influence of temperature (310–450 °C), pressure (200–260 bar), catalyst/bio-oil mass ratio (0–0.25 g catalyst/g bio-oil) and reaction time (0–60 min) during the re-forming in sub- and supercritical water of a bio-oil obtained from the fast pyrolysis of pinewood. The original liquid has a 39 wt.% of water and the following elemental composition in dry basis: 54 wt.% C, 3.3 wt.% H, 41.3 wt.% O, 0.8 wt.% N and 0.6 wt.% S. The upgrading experiments were carried out in a batch microbomb reactor employing a co-precipitated Ni–Co/Al–Mg catalyst. Statistical analysis of the re-forming results indicates that the operating conditions and the water regime (sub-/supercritical) have a significant influence on the process. Specifically, the yields to upgraded bio-oil (liquid), gas and solid vary in ranges of 5–90 %, 7–91 % and 3–31 % respectively. The gas phase, having a medium-high lower heating value (2–17 MJ/STP m3), is made up of a mixture of H2 (9–31 vol.%), CO2 (41–84 vol.%), CO (1–22 vol.%) and CH4 (1–45 vol.%). Depending on the operating conditions, the amount of C, H and O (wt.%) in the upgraded bio-oil varies in ranges of 48–74, 4–9 and 13–48 respectively. This represents an increase of up to 42 and 152 % in the proportions of C and H respectively, as well as a decrease of up to 69 % in the proportion of O. The higher heating value (HHV) of the treated bio-oil varies from 20 to 32 MJ/kg, which corresponds to an increase of up to 68 % with respect to the HHV of the original bio-oil.

Pyrolysis Bio-Oil Upgrading to Renewable Liquid Fuels by Catalytic Hydrocracking: Effect of Operating Conditions on the Process

This work analyses the influence of operating conditions during the catalytic hydrocracking of a bio-oil obtained from the fast pyrolysis of pinewood. The original liquid has a 39 wt.% of water and the following elemental composition in dry basis: 54 wt.% C, 3.3 wt.% H, 41.3 wt.% O, 0.8 wt.% N and 0.6 wt.% S.