Stability of Li-LSX zeolite in the catalytic pyrolysis of non-treated and acid pre-treated Isochrysis sp. Microalgae

This paper investigates the use of Li-LSX-zeolite catalyst over three regeneration cycles in presence of non-treated and acid pre-treated Isochrysis sp. microalgae. The spent and regenerated catalysts were characterised by surface analysis, elemental analysis (EA), SEM-EDS, and XRD to correlate their properties with the bio-oil yield and quality. The acid pre-treatment removed alkali metals, reducing gas yield in favour of bio-oil, but, at the same time, led to catalyst deactivation by fouling. Differently, the non-treated microalgae resulted in a bio-oil enriched in C and H and depleted in O, compared to the pre-treated ones, denoting higher deoxygenation activity. After 3 pyrolysis/regeneration cycles, the analyses suggest that there are no major changes on catalyst using non-treated microalgae. Regeneration at 700 °C has been shown to be able to remove most of the coke without damaging the Li-LSX zeolite structure. In summary, Li-LSX zeolite was effective in maintaining deoxygenation activity over three cycles in the pyrolysis of non-treated Isochrysis microalgae, while the algae pre-treatment with sulphuric acid was detrimental on the catalyst activity

Removal of NO at low concentration from air in urban built environments by activated miscanthus biochar

This work presents an innovative and sustainable approach to remove NO emissions from urban ambient air in confined areas (underground parking areas or tunnels) using low-cost activated carbons obtained from Miscanthus biochar (MSP700) by physical activation (with CO2 or steam) at temperatures ranging from 800 to 900 °C. The NO removal capacity of the activated biochars was evaluated under different conditions (temperature, humidity and oxygen concentration) and compared against a commercial activated carbon. This last material showed a clear dependence on oxygen concentration and temperature, exhibiting a maximum capacity of 72.6% in air at 20 °C, whilst, its capacity notably decreased at higher temperatures, revealing that physical NO adsorption is the limiting step for the commercial sample that presents limited oxygen surface functionalities. In contrast, MSP700-activated biochars reached nearly complete NO removal (99.9%) at all tested temperatures in air ambient. Those MSP700-derived carbons only required low oxygen concentration (4 vol%) in the gas stream to achieve the full NO removal at 20 °C. Moreover, they also showed an excellent performance in the presence of H2O, reaching NO removal higher than 96%. This remarkable activity results from the abundance of basic oxygenated surface groups, which act as active sites for NO/O2 adsorption, along with the presence of a homogeneous microporosity of 6 Å, which enables intimate contact between NO and O2. These features promote the oxidation of NO to NO2, which is further retained over the carbon surface. Therefore, the activated biochars studied here could be considered promising materials for the efficient removal of NO at low concentrations from air at moderate temperatures, thus closely approaching real-life conditions in confined spaces.J. Fermoso gratefully acknowledges the financial support from the Comunidad de Madrid through the Talent Attraction Programme (2018-T1/AMB-10023)

Production of fuel-cell grade H2 by sorption enhanced steam reforming of acetic acid as a model compound of biomass-derived bio-oil

Fuel-cell grade H2 has been produced by the sorption enhanced steam reforming (SESR) of acetic acid, a model compound of the bio-oil obtained from the fast pyrolysis of biomass. A Pd/Ni–Co catalyst derived from a hydrotalcite-like material (HT) with dolomite as CO2 sorbent was used in the process. A fixed-bed reactor with three temperature zones was employed to favor the catalytic steam reforming reaction in the high-temperature segment, the SESR reaction in the intermediate-temperature part, as well as the water-gas shift (WGS) and CO2 capture reactions in the low-temperature segment. Different conditions of pressure, temperature, steam/C molar ratio and weight hourly space velocity (WHSV) in the feed were evaluated. Higher steam/C molar ratios and lower WHSV values facilitated the production of H2 and reduced the concentrations of CH4, CO and CO2 in the produced gas. A fuel-cell grade H2 stream with a H2 purity of 99.8 vol.% and H2 yield of 86.7% was produced at atmospheric pressure, with a steam/C ratio of 3, a WHSV of 0.893 h−1 and a temperature of 575 °C in the intermediate part of the reactor (675 °C in the upper segment and 425 °C in the bottom part). At high pressure conditions (15 atm) a maximum H2 concentration of 98.31 vol.% with a H2 yield of 79.81% was obtained at 725 °C in the intermediate segment of the reactor (825 °C in the upper segment and 575 °C in the bottom part). Under these conditions an effluent stream with a CO concentration below 10 ppm (detection limit) was obtained at both low and high pressure, making it suitable for direct use in fuel cell applications.This work was carried out with financial support from the Spanish MINECO (Project ENE2014-53515-P), co-financed by the European Regional Development Fund (ERDF) and the Principado de Asturias (PCTI 2013-2017, GRUPIN14-079)Peer reviewe

Kinetic models comparison for non-isothermal steam gasification of coal–biomass blend chars

The non-isothermal thermogravimetric method (TGA) was applied to a bituminous coal (PT), two types of biomass, chestnut residues (CH) and olive stones (OS), and coal–biomass blends in order to investigate their thermal reactivity under steam. Fuel chars were obtained by pyrolysis in a fixed-bed reactor at a final temperature of 1373 K for 30 min. The gasification tests were carried out by thermogravimetric analysis from room temperature to 1373 K at heating rates of 5, 10 and 15 K min−1. After blending, no significant interactions were detected between PT and CH during co-gasification, whereas deviations from the additive behaviour were observed in the PT–OS blend. However, for the two coal–biomass blends, the gasification behaviour resembled that of the individual coal, as this component constituted the larger proportion of the blend. The temperature-programmed reaction (TPR) technique was employed at three different heating rates to analyze noncatalytic gas–solid reactions. Three nth-order representative gas–solid models, the volumetric model (VM), the grain model (GM) and the random pore model (RPM) were applied in order to describe the reactive behaviour of the chars during steam gasification. From these models, the kinetic parameters were determined. The best model for describing the reactivity of the PT, PT–CH and PT–OS samples was the RPM model. VM was the model that best fitted the CH sample, whereas none of the models were suitable for the OS sample.This work was carried out with financial support from the Spanish MICINN (Project PS- 120000-2006-3, ECOCOMBOS), and co-financed by the European Regional Development Fund, ERDF.Peer reviewe

The role of the surface acidic/basic centers and redox sites on TiO2 in the photocatalytic CO2 reduction

The development of sustainable processes for CO reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO deactivation is mainly initiated by the formation of carbonates and peroxo- species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion

Engineering the acidity and accessibility of the zeolite ZSM-5 for efficient bio-oil upgrading in catalytic pyrolysis of lignocellulose

The properties of the zeolite ZSM-5 have been optimised for the production and deoxygenation of the bio-oil∗ (bio-oil on water-free basis) fraction by lignocellulose catalytic pyrolysis. Two ZSM-5 supports possessing high mesopore/external surface area, and therefore enhanced accessibility, have been employed to promote the conversion of the bulky compounds formed in the primary cracking of lignocellulose. These supports are a nanocrystalline material (n-ZSM-5) and a hierarchical sample (h-ZSM-5) of different Si/Al ratios and acid site concentrations. Acidic features of both zeolites have been modified and adjusted by incorporation of ZrO2, which has a significant effect on the concentration and distribution of both Brønsted and Lewis acid sites. These materials have been tested in the catalytic pyrolysis of acid-washed wheat straw (WS-ac) using a two-step (thermal/catalytic) reaction system at different catalyst/biomass ratios. The results obtained have been assessed in terms of oxygen content, energy yield and composition of the produced bio-oil∗, taking also into account the selectivity towards the different deoxygenation pathways. The ZrO2/n-ZSM-5 sample showed remarkable performance in the biomass catalytic pyrolysis, as a result of the appropriate combination of accessibility and acidic properties. In particular, modification of the zeolitic support acidity by incorporation of highly dispersed ZrO2 effectively decreased the extent of secondary reactions, such as severe cracking and coke formation, as well as promoted the conversion of the oligomers formed initially by lignocellulose pyrolysis, thus sharply decreasing the proportion of the components not detected by GC-MS in the upgraded bio-oil∗

European journalism observatory: An international consolidated platform for training and professional networks in the Faculty of Information Sciences

El objetivo principal de este proyecto Innova-Docenia era ampliar y consolidar una plataforma de formación internacional y consolidada, para alumnos y alumnas de la Facultad de Ciencias de la Información, como parte del European Journalism Observatory (EJO), fundado por el Instituto Reuters de la Universidad de Oxford. Se trataba de afianzar EJO Spain como plataforma de formación y escaparate de las acciones implementadas en España, donde la Universidad Complutense de Madrid se convertía en el socio español principal. El Observatorio Europeo de Periodismo (EJO), una red de instituciones independientes y sin ánimo de lucro del campo de la comunicación de 14 países, tiene como objetivo tender puentes entre la investigación y la práctica del periodismo en Europa y fomentar el profesionalismo y la libertad de prensa. Promueve el diálogo entre investigadores y profesionales de los medios. Acerca los resultados de la investigación a las personas que trabajan en los medios. Su objetivo es mejorar la calidad del periodismo, contribuir a una mejor comprensión de los medios y fomentar la libertad de prensa y la responsabilidad de los medios. Nació en 2004, como una red de varios socios europeos, coordinados por la Universidad de Lugano y la Universidad de Oxford. Fue diseñado para observar las tendencias en el periodismo y en los medios de comunicación, desde una perspectiva ética y deontológica muy amplia. Desde entonces, sus artículos, investigaciones y editoriales son publicados en las distintas páginas web de cada socio: https://es.ejo-online.eu/red-ej

H2 production by sorption enhanced steam reforming of biomass-derived bio-oil in a fluidized bed reactor: An assessment of the effect of operation variables using response surface methodology

High-purity H2 was produced by the sorption enhanced steam reforming (SESR) of acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, in a fluidized bed reactor. A Pd/Ni–Co hydrotalcite-like material (HT) and dolomite were used as reforming catalyst and CO2 sorbent, respectively. The hydrogen yield and purity were optimized by response surface methodology (RSM) and the combined effect of the reaction temperature (T), steam-to-carbon molar ratio in the feed (steam/C) and weight hourly space velocity (WHSV) upon the sorption enhanced steam reforming process was analyzed. T was studied between 475 and 675 °C, steam/C ratio between 1.5 and a 4.5 mol/mol and WHSV between 0.893 and 2.679 h−1. H2 yield, H2 selectivity and H2 purity, as well as the CH4, CO and CO2 concentrations in the effluent gas, were assessed. The operating temperature proved to be the variable that had the greatest effect on the response variables studied, followed by the WHSV and the steam/C ratio. The results show that the H2 yield, H2 selectivity and H2 purity increased, while the CH4, CO and CO2 concentrations decreased, concurrently with the temperature up to around 575–625 °C. Higher values of the steam/C ratio and lower WHSV values favored the H2 yield, H2 selectivity and H2 purity, and reduced the CH4 concentration. It was found that the SESR of acetic acid at atmospheric pressure and 560 °C, with a steam/C ratio of 4.50 and a WHSV of 0.893 h–1 gave the highest H2 yield of 92.00%, with H2 purity of 99.53% and H2 selectivity of 99.92%, while the CH4, CO and CO2 concentrations remained low throughout (0.04%, 0.06% and 0.4%, respectively). The results also suggested that a slow CO2 capture rate led to a poor level of hydrogen production when the SESR process was carried out at low temperatures, although this can be improved by increasing the sorbent/catalyst ratio in the fluidized bed.The financial support from the Research Council of Norway (RCN) is gratefully acknowledged. The authors thank Franefoss Miljøkalk A/S (Norway) for supplying Arctic dolomite. M.V. Gil acknowledges funding from the CSIC JAE-Doc program, Spain, co-financed by the European Social Fund, and support from the Research Council of Norway through the Yggdrasil program.Peer reviewe