Aqueous phase reforming of starch wastewater over Pt and Pt-based bimetallic catalysts for green hydrogen production

This work analyses the application of aqueous phase reforming (APR) for green hydrogen production from starch industry wastewater. This work reports for the first time on the direct conversion of a high molecular weight biomass polymer contained in wastewater in contrast to low molecular weight substrates mainly reported in the literature. The potential of this type of feedstock was evaluated by varying the starch source (rice, potato, sweet potato and cassava) and the type of catalyst (carbon supported Pt, PtRu, PtPd, PtRe and PtRh catalysts). In APR experiments at 220 °C with synthetic wastewater, PtRu/C and Pt/C catalysts achieved the highest H2 yield values, around 51 mmol H2 per g of organic carbon in the initial wastewater, close to 2.6 times higher than that reported in the literature of brewery wastewater, a promising substrate. The lack of free aldehyde or keto groups due to glycosidic bonds between glucose units in starch results in higher conversion to gas and H2 production compared to APR of glucose. This fact shows that APR has more feedstock flexibility than that previously reported for light compounds. In the experiments with real wastewaters, the organic matter removal was influenced largely by the starch source: the best APR performance (28.5 mmol H2 gTOCi−1) was obtained for rice processing wastewater, which is characterized by the highest starch concentration and the lowest protein content. Poor performance was observed in the APR of potato processing wastewater, probably due to catalyst deactivation caused by protein fractio

Influence of bicarbonate, other anions and carbon dioxide in the activity of Pd-Cu catalysts for nitrate reduction in drinking water

Synthetic and commercial drinking waters with different composition were studied as reaction media to study the influence of salts in NO3- catalytic reduction using a Pd-Cu catalyst supported on a carbon black. As a general trend, a decrease in NO3- conversion and an increase in NH4+ selectivity were observed for high HCO3- concentration media in mixed salts waters. Literature has commonly ascribed HCO3- effect to competitive adsorption with NO3-. However, in the current work, the mechanism for effect HCO3- is reconsidered basis on HCO2- formation during NO3- catalytic reduction, here reported for the first time. HCO2- formation indicates that hydrogenation of HCO3- occurs in addition to adsorption. Likewise, decomposition of HCO2- on the catalysts surface releases hydrogen leading to increased spill-over and relevant hydrogenation of NO3- to NH4+. The presence of SO42-, Cl- reduces NH4+ selectivity due to competition for active sites and lower HCO2- generation. Furthermore, it was observed that the use of CO2 as buffer also contribute to the hydrogenation of NO3- to NH4+ through HCO2- routeThe authors greatly appreciate the support from Spanish Agencia Estatal de Investigacion ´ RTI2018-098431-B-I00 (MCIU/AEI/FEDER, UE). Dydia Tanisha Gonzalez ´ thanks the Regional Government of Madrid a research grant (PEJ-2020-AI/AMB-17551

Aqueous-phase reforming of water-soluble compounds from pyrolysis bio-oils

Aqueous-phase reforming (APR) of model compounds of bio-oil aqueous fraction (AFB) was studied at different operating conditions. Substrate conversion, carbon-to-gas yield (CCgas) and hydrogen and alkanes production were evaluated. Levoglucosan, hydroxyacetone, furfural and acetic acid were selected as representative of AFB and tested in batch APR at different concentrations (1–5 %wt.), temperatures (175–220 ◦C) and reaction times (0.5–4 h), using 3% (wt.) Pt/CB catalysts. Best results were obtained at 220 ◦C and 1%, with 70–90% substrate conversions, 45–70% CC gas and hydrogen production up to 50 mmol per gram of total organic carbon (TOC). Catalyst stability was checked in APR of levoglucosan during five successive 4 h reaction cycles. The catalyst exhibited high stability, CCgas remained constant and hydrogen production increased and became stable after first reaction cycle with only a slight decrease of TOC conversion. The catalyst with well dispersed metal phase and high contribution of nanoparticles smaller than 2 nm showed a higher production of hydrogen. APR was proved to be a feasible option for the valorisation of AF

Pd and Pd-Cu supported on different carbon materials and immobilized as flow-through catalytic membranes for the chemical reduction of NO3, NO2-and BrO3- in drinking water treatment

Powdered catalysts are commonly used in lab-scale tests for the catalytic reduction of oxoanions in drinking water, but their powder nature limits their application at full scale. In this work, Pd and Pd-Cu catalysts (5% wt.) supported on carbon materials with different structural properties, in powder form, were used to prepare catalytic membranes that were tested in a reactor with flow-through configuration (FTCMR) to study their performance in the reduction of NO3-, NO2- and BrO3-. Pd catalytic membranes showed high activity in the reduction of NO2-, being the selectivity to NH4+ lower than 2% at 80% NO2- conversion in all cases. In BrO3- reduction, they exhibited a wide range of conversions being the catalyst supported on materials with high conductivity the most active ones, which may be ascribed to the charge distribution at the metal-carbon interface. NO3- reduction using Pd-Cu catalytic membranes showed that catalysts supported on materials with small nanoparticle size and low electrical conductivity exhibited higher selectivity to NH4+. FTCMR led to a good control of H2 transfer and availability in the active sites, facilitating the tuning of H2 availability conditions to preserve the activity, while maintaining/diminishing selectivity to NH4+. In simultaneous oxoanions reduction tests, NO3- reduction was inhibited by Br species, probably by affection of the Pd-Cu redox cycle. This fact could be crucial to the future development of drinking water treatment processes, as conditions the order of the disinfection and NO3- reduction stepsThe authors greatly appreciate the support from Spanish Agencia Estatal de Investigacion ´ (AEI, RTI2018–098431-BI00). Adrian ´ Marí thanks the Spanish AEI for a research grant (PRE-2019-088601). This work was also financially supported by: LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM) and funded by national funds through FCT/MCTES (PIDDAC), and project NORTE01–0145-FEDER-000069 (Healthy Waters) co-funded by European Regional Development Fund (ERDF), through North Portugal Regional Operational Program (NORTE2020), under the PORTUGAL 2020 Partnership Agreemen

Laminar N-Doped Carbon Materials from a Biopolymer for Use as a Catalytic Support for Hydrodechlorination Catalysts

Nitrogen-doped porous carbons were prepared using a chitosan biopolymer as both a carbon and nitrogen precursor and metallic salts (CaCl(2) and ZnCl(2)-KCl) as a templating agent with the aim of evaluating their performance as catalyst supports. Mixtures of chitosan and templating salts were prepared by simple grinding subjected to pyrolysis and finally washed with water to remove the salts. The resulting materials were characterized, showing that homogeneous nitrogen doping of carbon was achieved (7–9% wt.) thanks to the presence of a nitrogen species in the chitosan structure. A lamellar morphology was developed with carbon sheets randomly distributed and folded on themselves, creating slit-shaped pores. Substantial porosity was observed in both the micropore and mesopore range with a higher surface area and microporosity in the case of the materials prepared by ZnCl(2)-KCl templating and a larger size of mesopores in the case of ZnCl(2). Catalysts with well-dispersed Pd nanoparticles (around 10 nm in diameter size) were synthesized using the chitosan-based carbons obtained both by salt templating and direct chitosan pyrolysis and tested in the aqueous phase hydrodechlorination of 4-chlorophenol. The fast and total removal of 4-chlorophenol was observed in the case of catalysts based on carbons obtained by templating with CaCl(2) and ZnCl(2)-KCl in spite of the low metal content of the catalysts (0.25% Pd, wt.)

Enhancement of activity and selectivity to nitrogen in catalytic nitrate reduction by use of conductive carbon catalytic supports and control of hydrogen mass transfer regime

Carbon materials with different structural properties (activated carbon, carbon nanofibers, reduced graphene oxide, graphite, and carbon black) were used as supports of Pd-Cu (5 wt%) catalysts for the catalytic reduction of NO3- in batch reactors. In general, those catalyst with smaller metal nanoparticles and carbon supports with higher specific surface area were more active, although remarkable activity was also observed for catalysts with relatively large nanoparticles and conductive supports. Conductivity of carbon supports also contributed to a lower selectivity to NH4+, which can be ascribed to higher charge transfer between metal and support reducing activation of intermediate species. The decrease of H2 feed into the reaction system resulted in external (gas-liquid) mass transfer constrains, as evidenced by the parameters describing control regime, and led to diminished NH4+ selectivity, particularly in the case of catalysts with conductive supports. Approaches combining control of mass transfer regime and conductive carbon catalytic supports can be useful to enhance selectivity to N2, which is a major challenge in catalytic NO3- reductionThe authors greatly appreciate the support from Spanish Agencia Estatal de Investigación (AEI, RTI2018-098431-B-I00). Dydia Tanisha González thanks the Regional Government of Madrid a research grant (PEJ-2020-AI/AMB-17551) and Adrián Marí thanks the Spanish AEI a research grant (PRE-2019–088601

Valorization to hydrogen of bio-oil aqueous fractions from lignocellulosic biomass pyrolysis by aqueous phase reforming over Pt/C catalyst

Aqueous phase reforming was studied for the valorization to hydrogen of the aqueous fraction of bio-oil from lignocellulosic biomass pyrolysis. Aqueous phase reforming was carried out at 220 °C with a 3 % wt. Pt/carbon catalyst and an aqueous fraction of bio-oil feed containing 1 % wt. of organic matter. Binary and multicomponent mixtures representing aqueous fractions of bio-oil were studied. Strong hydrogen production dependence on aqueous fraction of bio-oil composition was evidenced. Higher processability was obtained for aqueous fractions of bio-oil rich in levoglucosan and hydroxyacetone, reaching a hydrogen production close to 40 mmol per gram of organic carbon, whereas furfural and acetic acid hampered reforming. A significant influence of minority components such as methanol and, particularly, formic acid, was observed. These components improved reforming of the whole multicomponent mixture, showing that blending with biorefinery fractions rich in them can improve the applicability of aqueous phase reforming. The catalyst exhibited stable activity and hydrogen production after 5 reaction cycles and more than 20 h. An increase in selectivity was observed during cycles 2 and 3, which was studied by characterization of fresh and used catalysts to show structure-selectivity relationships. No significant variation of Pt2+/Pt0 and metal particle mean diameter were observed, but Pt nanoparticles underwent morphological changes leading to higher prevalence of low coordination sites, in particular step-edge sites on the particle surface, resulting in higher hydrogen production. Temperature programmed desorption and oxidation analysis showed a cumulative deposition of reaction byproducts on the catalyst surface that contributed to loss of activityThis work was supported by Community of Madrid (research network BIO3, P2018/EMT-4344) and Ministry of Science and Innovation (Recovery, Transformation and Resilience Plan, project HYDROCIRCLE, TED2021-130054B-I00). Jessica Justicia thanks supporting from Ministry of Science, Innovation and University trough the project WASTEVALOR (PID2019-108445RB-I00

Experiencias de Aprendizaje-Servicio en la UPM: 2021 y 2022

La Oficina de Aprendizaje-Servicio (ApS) de la UPM, constituida en sesión del Consejo de Gobierno de diciembre de 2019 tiene, como misión fundamental, promover en el ámbito de las enseñanzas de esta universidad la metodología ApS. Con esta finalidad se vienen realizando convocatorias de proyectos de impacto social alineados con los ODS como un mecanismo más para la contribución a la Agenda 2030, y se colabora intensamente con las diversas oficinas constituidas con el mismo objetivo en otras universidades. Nuestra oficina pretende impulsar progresivamente la colaboración con entidades ajenas a la UPM, y atender demandas y necesidades sociales en las que nuestros estudiantes y profesores brinden sus conocimientos para la construcción de una mejor y más justa sociedad. Con este propósito, se han puesto en marcha numerosas iniciativas y colaboraciones con Ayuntamientos, Asociaciones, ONG, Fundaciones y centros de enseñanza, con el fin común de plantear mejoras y trabajar con entornos desfavorecidos, y colectivos vulnerables de nuestro entorno. Cabe destacar la muy positiva acogida que, progresivamente se está logrando, en lo relativo a la diseminación de estas iniciativas en el ámbito de la UPM, viéndose incrementada la participación e interés de nuestros docentes y estudiantes en los llamamientos que se realizan desde la oficina. Desde la constitución de la oficina, son ya más de 100 actividades desarrolladas con la participación de más de 500 profesores. Uno de los compromisos de la Oficina ApS de la UPM es dar visibilidad por su carácter meritorio a las experiencias realizadas por el profesorado y los estudiantes de nuestra universidad y, es por ello, que nos complace la presentación de esta primera edición del ebook, en el que se recogen algunas de las experiencias realizadas en nuestra universidad y que confiamos ampliar periódicamente con futuras ediciones. Nuestro más sincero agradecimiento a todos los profesores que habéis hecho posible esta primera publicación con vuestras contribuciones