Hidrogeno energia-bektorea: I. iturriak eta ekoizpena

Gaur egungo ekonomia petrolioan oinarrituta dago. Eraginkortasun txikikoa da honelako erregai fosilak energia bihurtzeko prozesua, baina gainera, ingurumenari kalte egiten dioten gasak igortzen dira, CO2 kasu. Hidrogenotiko energia-lorpenak, prozesu eraginkorragoa izateaz gain, ez dio igurumenari kalterik egiten. Ura edo edozein erregai fosiletatik lor daiteke hidrogenoa, eta erabiltzen diren energia-iturrien garbitasunaren araberako garbitasuna lortzen da. Lan honetan, ura, ikatza edo biomasa bezalako lehengaiak erabiltzen dituzten hidrogeno-ekoizpenerako prozesuak aztertuko dira

Hidrogeno energia-bektorea: I. iturriak eta ekoizpena

Gaur egungo ekonomia petrolioan oinarrituta dago. Eraginkortasun txikikoa da honelako erregai fosilak energia bihurtzeko prozesua, baina gainera, ingurumenari kalte egiten dioten gasak igortzen dira, CO2 kasu. Hidrogenotiko energia-lorpenak, prozesu eraginkorragoa izateaz gain, ez dio igurumenari kalterik egiten. Ura edo edozein erregai fosiletatik lor daiteke hidrogenoa, eta erabiltzen diren energia-iturrien garbitasunaren araberako garbitasuna lortzen da. Lan honetan, ura, ikatza edo biomasa bezalako lehengaiak erabiltzen dituzten hidrogeno-ekoizpenerako prozesuak aztertuko dira

Hidrogeno energia-bektorea II: gordetzea eta energia-lorpena

Aurreko artikulu batean [Ekaia 21 (2008) 65-88] hidrogeno-ekonomiaren lehen zatia den hidrogeno-ekoizpena aztertu da. Haren jarraipena den lan honetan hidrogeno-ekonomiaren beste bi zatiak aztertuko dira: gordetzea eta erabilera azken buruko energia bihurtzeko. Hidrogeno-ekonomiarako trantsizioan ari garen honetan, bi prozesuak hobetzen eta garatzen ari dira teknologiaren ikuspuntutik, besteak beste, kostuak murrizteko. Ahal den bolumen txikiena erabiliaz hidrogenoa gordetzeko metodo fisiko eta kimikoen deskribapena aztertuko dira hemen, bai eta arlo horietan ikerkuntzak dauzkan erronka nagusiak ere. Azkenik, hidrogenotiko energia-lorpenerako metodo eraginkorrena den erregai-pilaren egitura eta eragiketa aztertuko dira

Hidrogeno energia-bektorea II: gordetzea eta energia-lorpena

Aurreko artikulu batean [Ekaia 21 (2008) 65-88] hidrogeno-ekonomiaren lehen zatia den hidrogeno-ekoizpena aztertu da. Haren jarraipena den lan honetan hidrogeno-ekonomiaren beste bi zatiak aztertuko dira: gordetzea eta erabilera azken buruko energia bihurtzeko. Hidrogeno-ekonomiarako trantsizioan ari garen honetan, bi prozesuak hobetzen eta garatzen ari dira teknologiaren ikuspuntutik, besteak beste, kostuak murrizteko. Ahal den bolumen txikiena erabiliaz hidrogenoa gordetzeko metodo fisiko eta kimikoen deskribapena aztertuko dira hemen, bai eta arlo horietan ikerkuntzak dauzkan erronka nagusiak ere. Azkenik, hidrogenotiko energia-lorpenerako metodo eraginkorrena den erregai-pilaren egitura eta eragiketa aztertuko dira

Aqueous-phase reforming of glycerol over Pt-Co catalyst: Effect of process variables

This study examined the influence of process variables (glycerol concentration in feed, coupled temperature/pressure and space velocity) in the catalytic performance in the APR of glycerol over 0.3Pt/CoAl catalyst in a continuous fixed-bed reactor in order to maximize the production of H2. The effect of glycerol concentration in the feed was studied from 5 to 20 wt%, the coupled temperature/pressure varied from 225 °C/25 bar to 260 °C/50 bar and the spatial velocity was changed from 0.68 to 17 h-1. Our results reflected that H2 production was favored at higher reaction temperature/pressure (3.62 vs. 2.49 molH2/molGly-converted, at the most severe and mild conditions, respectively), lower WHSV (3.89 vs. 1.27 molH2/molGly-converted, at the lowest and highest space velocity, respectively) and more diluted feedstocks (3.95 vs. 1.44 molH2/molGly-converted, at the most diluted and concentrated freestreams, respectively). A threshold value at 10 wt% glycerol was found for the ratio of dehydrogenation to dehydration liquid products. The post-reaction catalyst was also characterized by several techniques, showing that Co leaching was the major drawback, especially at the mildest operation conditions, while carbonaceous deposits are negligible.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0

Bio‑hydrogen and valuable chemicals from industrial waste glycerol via catalytic aqueous-phase transformation

Waste glycerol obtained as by-product of biodiesel production has been submitted to a sequential physico-chemical treatment in order to make it suitable for continuous Aqueous-Phase Reforming (APR) in a tubular reactor. Special focus was given to the impact of impurities. APR was performed using 0.3%Pt/CoAl2O4 catalyst, at 260 °C and 50 bar within WHSV range 6–55 h−1 to cover whole conversion ranges. Glycerol conversion and yield to hydrogen reached 99.7% and 45.4%, respectively at WHSV = 6 h−1. The liquid product distribution strongly varied with glycerol conversion, maximum C-yield to 1,2-propylene glycol was attained in the 60–90% glycerol conversion range. APR of methanol and acetic acid aqueous feedstreams were investigated independently. It was concluded that acetic acid exerts a negative influence on catalyst stability since glycerol conversion decreased by 41% after 5 h TOS. Extensive characterization of fresh and exhausted catalysts revealed strong Co leaching, especially for acetic acid APR, oxidation of metals, and carbonaceous deposits. The basis for the regeneration of the spent catalyst, consisting of a reductive treatment at 500 °C, has been established. This work is expected to have significant implications for the development of APR technology for crude glycerol from biodiesel industry.This research was supported by grant PID2019-106692EB-I00 funded by MCIN/AEI/10.13039/501100011033. The authors thank for technical support provided by SGIker of UPV/EHU and European funding (ERDF and ESF)

Cobalt aluminate spinel-derived catalysts for glycerol aqueous phase reforming

Catalytic activity at mild (235 °C/3.5 MPa) and severe (260 °C/5.0 MPa) APR conditions was investigated over catalysts based on cobalt aluminate spinel synthetized by coprecipitation. Co/Al ratio was varied and physicochemical characteristics were assessed by N2 adsorption, H2 chemisorption, XRD, H2-TPR, DRS-UV, FTIR, CO2-TPD, NH3-TPD and XPS. Formation of cobalt aluminate produced strong Co-O-Al interaction in the catalyst precursor leading to improved Co dispersion upon activation. Co/Al ratio could be used to tune catalyst characteristics, thus selectivity towards the desired reaction pathway. Overall, Co/Al above the stoichiometric value produced smaller and more stable metallic Co, which allowed best APR performance. For instance, at 235 °C/3.5 MPa glycerol conversion and conversion to gas of 0.625CoAl (88% and 22%) were notably higher than those of bare Co3O4 (23% and 5%). At severe conditions, 0.625CoAl catalyst produced 231 μmolH2/gcat min (60% H2). Statistical analysis of data collected from long-term run was used to investigate reaction mechanism. Long-term run revealed that sintering and oxidation were main mechanisms for catalyst deactivation whereas some leaching of Co nanoparticles, and carbonaceous deposition was also detected.Ministerio de Economía y Competitividad, ENE2016-7450-

Bimetallic Pt-Co Catalysts for the Liquid-Phase WGS

[EN] Bimetallic Pt-Co catalysts derived from cobalt aluminate spinel were investigated in the liquid-phase water–gas shift (WGS) reaction and CO hydrogenation. Liquid-phase WGS is a key reaction in the aqueous-phase reforming (APR) of polyols; thus, WGS activity is essential to formulate good APR catalysts. In this work, catalysts with different Pt/Co molar ratios were synthesized together with a reference Pt/alumina. All the synthesized catalysts were characterized by various techniques in order to gain knowledge on their structural and surface characteristics. WGS activity was tested with a feedstream of CO/H2O = 1/15 (space-time of 76.8 kg·s/molCO), isothermal operation at 260 ºC and 50 bar, for 10 TOS. Bimetallic Pt-Co catalysts showed improved activity in liquid-phase WGS in comparison to bare Co or Pt catalysts, which was ascribed to the synergistic effect. Despite being subjected to an increased hydrogen concentration in the feedstream (H2/CO between 0 and 12/3), these catalysts maintained a preferential selectivity towards WGS activity. In addition, the effect of temperature (220–260 ºC) and pressure (25–50 bar) was investigated over a catalyst with 0.3Pt/CoAl. CO conversion and CO2 yield were more sensitive to temperature, while a higher pressure favored methane production. The measured activation energy in the 220–260 ºC temperature range was 51.5 kJ/mol.This research was funded by Mineco (ENE2016-74850-R and PID2019-106692EB-I00) and FEDER. The APC was funded by ENE2016-74850-R. A.J.R. was supported by a PhD research fellowship provided by the University of the Basque Country UPV/EHU (PIF-17/319)

Research overview of hydrogen production from biomass: A bibliometric analysis of the research published during the 1979-2019 period

The purpose of this paper is to develop a conceptual analysis of hydrogen production from biomass research in literature by quantifying the main bibliometric performance indicators, identifying the main authors, countries, journals and research areas and evaluating the intellectual structure and evolution of the field using SciMAT as a bibliometric analysis software. In this way, the methodology implemented in this research encompasses both the bibliometric performance analysis and science mapping approaches of biomass-based hydrogen production research themes. The bibliometric performance analysis is centered on the citation-based impact of the scientific output, while science mapping illustrates the evolution of the research themes that build the field through the use of bibliometric network analysis techniques. The publications related to biomass-based hydrogen production research available at Scopus have been compiled between 1979 and 2019 (876 publications). Finally, the paper provides objective evidence of the evolution of the hydrogen production from biomass field, which confirms the interest that researchers have in this theme to develop new capabilities. Finally, it offers a framework to support researchers evaluating the field and, finally, to assist them in the development and direction of their future analysis identifying trends in terms of research

Effect of the synthesis method on the performance of Ni-CeO2-ZrO2 catalysts for the hydrogenolysis of glycerol with endogenous hydrogen

In this work, we investigated the influence of the synthesis method of Ni-based CeZr catalysts on their physicochemical and catalytic properties in the hydrogenolysis (HDO) of glycerol with H2 in-situ produced by the aqueous-phase reforming (APR). Conventional impregnation method involved surface nickel deposition (NiCeZr-IM). The one-pot methods, which involved nickel embedment into CeZr lattice, included sol-gel (NiCeZr-SC) and coprecipitation (NiCeZr-CA and ultrasound-assisted NiCeZR-CS) methods. Differences in textural, structural, morphological, redox, and surface properties, together with and catalytic performance in the glycerol APR-HDO, were investigated systematically. As well, spent catalysts were deeply characterized. There were notable differences among textural properties, which significantly affected their activity in glycerol conversion. The structural characterization confirmed the successful integration of Ni into the CeZr lattice, especially for the catalysts synthesized using one-pot methods. One-pot synthesized catalysts showed stronger Ni-CeZr interaction, which affect the reducibility. The catalysts prepared by coprecipitation contained the highest metal-to-acid ratio, making them very active for C-O bond hydrogenation. Post-reaction characterization discloses a leaching of the nickel, in greater amount for both coprecipitated catalysts. This study revealed the potential of Ni-based catalysts derived from subsurface insertion of nickel into the CeZr matrix for the hydrogenolysis of glycerol without external hydrogen.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0