Hidrogeno-ekoizpena bio-oilaren erreformatze katalitikoaren bidez

The growing demand of H2 for its use as petrochemical raw material and clean fuel has boosted the development of processes for its production from alternative sources to oil, among which biomass has received special attention due to its availabil-ity and renewable nature. There is an increasing interest in the development of indirect routes for H2 production from biomass, via steam reforming of biomass-derived oxy-genated compounds. Indirect pathways to obtain hydrogen from biomass, such as the steam reforming of oxygenates derived from biomass, are these days in the spotlight. Among them, the so called bio-oil deserves special attention, due to its economic via-bility. Actually, delocalized production of bio-oil in biomass production plants allows for its subsequent transportation to centralized units for its further valorization. How-ever, problems caused by the pyrolytic lignin produced during this process need to be also considered, specially, the solid residue deposited on both the catalyst and the reac-tion setup when bio-oil evaporates. Scale up technology is deemed necessary in order to solve this drawback. Moreover, the development of an active, selective and stable catalyst is of the utmost importance towards achieving full viability of the process. In this piece of work, we aim at giving an overview on the main bio-oil reforming strate-gies in literature, with special emphasis on the results from our research group.; H2-aren eskariaren igoerak, petrokimikako lehengai eta erregai garbi gisa erabiltzeko, petrolioaz bestelako lehengaiak jatorri duten prozesuen garapena bul-tzatu du. Prozesu horien artean, biomasak arreta berezia bereganatu du haren erabilga-rritasunagatik eta berriztagarritasunagatik. Biomasatik H2-a lortzeko zeharkako bideek gero eta jakin-min handiagoa eragin dute, esate baterako, biomasatik eratorritako oxi-genatuen bidezko lurrun erreformatzeak. Horien artean, bio-oilak interes handia dauka, beste bideek baino bideragarritasun ekonomiko handiagoa izan baitezake. Izan ere, bio-oilak ekoizpen deslokalizatua izan dezake biomasaren ekoizpen-fokoetan eta on-doren, unitate zentralizatuetara garraia daiteke balioztatzeko. Dena dela, prozesu horre-tan kontuan hartu beharra dago lignina pirolitikoak sortzen dituen arazoak, zehatzago, erreakzio-ekipoan eta katalizatzailean depositatzen den hondakin solidoa bio-oila lu-rruntzen denean. Arazo hori gainditzeko, beharrezkoa da teknologia eskalagarria. Ho-rretaz gain, katalizatzaile aktibo, selektibo eta iraunkorren garapena funtsezkoa da pro-zesu horren bideragarritasuna lortzeko. Lan honetan, bibliografian dauden bio-oilaren erreformatzearen estrategia nagusiak aurkezten dira, ikerketa-taldearen emaitza origi-nalak nabarmenduz

Cost-effective upgrading of biomass pyrolysis oil using activated dolomite as a basic catalyst

This study deals with a continuous process on a calcined dolomite operating at atmospheric pressure and by cofeeding water for cost-effective upgrading of raw bio-oil at 400 °C and 500 °C. The distribution of carbon in the feed to the product fractions (gas and upgraded bio-oil) and to the dolomite (as CO2 captured and coke) was investigated with time on stream, as well as the evolution of the gas and the upgraded bio-oil composition. Acids and high-molecular weight phenols were completely removed from the raw bio-oil for 0.5 h time on stream, with the upgraded bio-oil being mainly composed of ketones (acetone, 2-butanone and cyclopentanones). Chromatographic analyses of the reaction products were combined with analysis of the dolomite characteristics by thermogravimetry and X-ray diffraction. The results are explained on the basis of possible reaction mechanisms on the dolomite basic sites (CaO, Ca(OH)2 and MgO) and the extent of dolomite carbonation with adsorbed CO2. Composition of the upgraded bio-oil makes it suitable for further catalytic valorization for obtaining fuels and chemicals, such as H2 (by steam reforming) and aromatic hydrocarbons (by dual-stage hydrogenation- cracking processes).This work was carried out with the financial support of the Department of Education Universities and Investigation of the Basque Government (IT2018-19), the Ministry of Economy and Competitiveness of the Spanish Government jointly with European Regional Development Funds (AEI/FEDER, UE) (Project CTQ2015- 68883-R), the European Commission (HORIZON H2020-MSCA-RISE- 2018, Contract No. 823745), and PhD grant (BES-2016-078132) for N. García-Gómez

Stability of a NiAl2O4 Derived Catalyst in the Ethanol Steam Reforming in Reaction-Regeneration Cycles: Effect of Reduction Temperature

The catalyst regeneration is still a challenge to make the ethanol steam reforming (ESR) process feasible for sustainable H2 production. NiAl2O4 spinel derived catalysts are highly active and selective for ESR, but they require avoiding irreversible deactivation to ensure their regeneration. Their stability depends on the catalyst structure, and herein we report different Ni/Al2O3-NiAl2O4 catalysts obtained upon reduction of a NiAl2O4 spinel at 700, 750, or 850 °C. The catalysts were tested in ESR reaction-regeneration cycles, with reaction at 600 °C and regeneration by coke combustion at 850 °C followed by reduction at the corresponding temperature. The fresh, spent, and regenerated catalysts were characterized using X-ray diffraction, N2 physisorption, temperature programmed reduction and oxidation, and scanning electron microscopy. The irreversible deactivation is due to Ni volatilization and catalyst particle fragmentation. These phenomena are prompted by a high filamentous carbon deposition favored by the Al2O3 content in the catalyst. The reduction in the 700–750 °C range is optimum for controlling the Al2O3 content, increasing the NiAl2O4/Al2O3 ratio in the resulting catalyst. These catalysts show a period of partial reversible deactivation by coke with a change in the H2 formation mechanism reaching a pseudo-stable state with a H2 yield of 40% and a reproducible performance in successive reaction-regeneration cycles.This research was funded by the Ministry of Science and Innovation of the Spanish Government (grant RTI2018-100771-B-I00 and PhD grant BES-2019-090943 for S.I.-V. funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”); the European Commission (HORIZON H2020-MSCA RISE 2018. Contract No. 823745); the Department of Education, Universities and Investigation of the Basque Government, grant number IT1645-22

Comparison of the NiAl2O4 derived catalyst deactivation in the steam reforming and sorption enhanced steam reforming of raw bio-oil in packed and fluidized-bed reactors

The choice of appropriate reactors and reforming strategies is key to make progresses on scaling up H2 production processes from raw bio-oil. This work compares the performance (conversion, product yields and deactivation) of packed-bed and fluidized-bed reactors (PBR and FBR, respectively) using a NiAl2O4 spinel derived catalyst for the H2 production from raw bio-oil via steam reforming (SR) and sorption enhanced SR (SESR, with dolomite to capture CO2). The experiments were carried out at 600 °C; steam/carbon ratio, 3.4; space time, 0.15 h; time on stream, 5 h; dolomite/catalyst ratio, 10 (SESR runs); and with prior thermal separation of the pyrolytic lignin from the raw bio-oil. The initial H2 yields are 80 % and 69 % in the SR runs with PBR and FBR, respectively, and 99 % and 92 % in the CO2 capture period (of 30 min duration) of the SESR runs in the PBR and FBR, respectively. The lower H2 yield in the FBR is due to the less efficient gas–solid contact (bubbling or slugging phenomena). Based on the analysis of the spent catalysts with varied techniques the catalyst deactivation is related to the coke deposition, whose quantity and nature (amorphous or structured) depends on the reactor type and reforming strategy. The catalyst deactivation is slower in the FBR due to the rejuvenation of the catalyst surface by the moving particles that favor external coke gasification. The presence of dolomite prolongs the period of stable catalyst activity in both reactors with different effects on the coke quantity and nature. The results are of interest to advance on scaling up the SESR process that would require a FBR integrated with a regeneration unit for the catalyst and sorbent.This work has been carried out with the financial support of the grant RTI2018-100771-B-I00 and PID2021-127005OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”, the European Commission (HORIZON H2020-MSCA RISE 2018. Contract No. 823745) and the Department of Education, Universities and Investigation of Basque Government (Project IT1645-22 and PhD grant PRE_2021_2_0147 for L. Landa). The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU), and to Calcinor S.A. for supplying the dolomite

Oxidative Steam Reforming of Raw Bio-Oil over Supported and Bulk Ni Catalysts for Hydrogen Production

Several Ni catalysts of supported (on La2O3-alpha Al2O3, CeO2, and CeO2-ZrO2) or bulk types (Ni-La perovskites and NiAl2O4 spinel) have been tested in the oxidative steam reforming (OSR) of raw bio-oil, and special attention has been paid to the catalysts' regenerability by means of studies on reaction-regeneration cycles. The experimental set-up consists of two units in series, for the separation of pyrolytic lignin in the first step (at 500 degrees C) and the on line OSR of the remaining oxygenates in a fluidized bed reactor at 700 degrees C. The spent catalysts have been characterized by N-2 adsorption-desorption, X-ray diffraction and temperature programmed reduction, and temperature programmed oxidation (TPO). The results reveal that among the supported catalysts, the best balance between activity-H-2 selectivity-stability corresponds to Ni/La2O3-alpha Al2O3, due to its smaller Ni-0 particle size. Additionally, it is more selective to H-2 than perovskite catalysts and more stable than both perovskites and the spinel catalyst. However, the activity of the bulk NiAl2O4 spinel catalyst can be completely recovered after regeneration by coke combustion at 850 degrees C because the spinel structure is completely recovered, which facilitates the dispersion of Ni in the reduction step prior to reaction. Consequently, this catalyst is suitable for the OSR at a higher scale in reaction-regeneration cycles.This work was carried out with the financial support of the Department of Education Universities and Investigation of the Basque Government (IT748-13), the Ministry of Economy and Competitiveness of the Spanish Government jointly with the European Regional Development Funds (AEI/FEDER, UE) (Projects CTQ2012-35263, CTQ2015-68883-R and CTQ2016-79646-P and Ph.D. grant BES-2013-063639 for A. Arandia)

Unveiling the deactivation by coke of NiAl2O4 spinel derived catalysts in the bio-oil steam reforming: Role of individual oxygenates

The catalyst stability, mainly affected by coke deposition, remains being a challenge for the development of a sustainable process for hydrogen production by steam reforming (SR) of bio-oil. In this work, the influence of oxygenates composition in bio-oil on the deactivation by coke of a NiAl2O4 spinel derived catalyst has been approached by studying the SR of a wide range of model oxygenates with different functionalities, including acetic acid, acetone, ethanol, acetaldehyde, acetol, catechol, guaiacol and levoglucosan. A fluidized bed reactor was used in the following conditions: 600 and 700 degrees C; steam/carbon ratio, 3 (6 for levoglucosan); space-time, 0.034 gcatalyst h/gbio-oil (low enough to favor the rapid catalyst deactivation), and; time on stream, 5 h. The spent catalysts were analyzed with several techniques, including Temperature Programed Oxidation (TPO), X-ray Diffraction (XRD), N2 adsorption-desorption, Scanning and Transmission Electron Microscopy (SEM, TEM) and Raman Spectroscopy. The main factors affecting the catalyst stability are the morphology, structure and location of coke, rather than its content, that depend on the nature of the oxygenate feed. The deposition of pyrolytic and amorphous coke that blocks the Ni sites inhibiting the formation of filamentous carbon causes a rapid deactivation in the guaiacol SR. Conversely, the large amount of carbon nanotubes (CNTs) giving rise to a filamentous coke deposited in the SR of aliphatic oxygenates only causes a slight deactivation. The increase in the temperature significantly reduces coke deposition, but has low impact on deactivation.This work has been carried out with the financial support of the Ministry of Science and Innovation of the Spanish Government (grant RTI2018-100771-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe") , the European Commission (HORIZON H2020-MSCA RISE 2018. Contract No. 823745) and the Department of Education, Universities and Investigation of the Basque Government (Project IT1645-22, IT1218-19 and PhD grant PRE_2021_2_0147 for L. Landa) . The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU)

Effect of reaction conditions on the deactivation by coke of a NiAl2O4 spinel derived catalyst in the steam reforming of bio-oil

[EN]The steam reforming of bio-oil is a promising and economically feasible technology for the sustainable H-2 production, yet with the main challenge of designing highly active and stable catalysts. This work aimed to study the deactivation mechanism of a NiAl2O4 spinel derived catalyst, the role of Ni and alumina sites in this mechanism and the appropriate reaction conditions to attenuate deactivation. The reaction tests were carried out in a fluidized bed reactor with prior separation of the pyrolytic lignin. The fresh or used catalysts were characterized using X-ray diffraction, temperature-programmed oxidation, X-ray photoelectron spectroscopy, scanning electron microscopy combined with energy dispersive X-ray spectroscopy, and Raman spectroscopy. For steam/carbon ratios > 3.0, space time above 0.075 h and temperature between 600-700 degrees C, high initial hydrogen yield is obtained (in the 85-90 % range) with CO yield near 20 %, CH4 yield below 5 % and negligible initial yield of hydrocarbons. The catalyst is more stable at 600 degrees C, with coke formation preferentially located on Ni sites inside the catalyst particle. Increasing the temperature favors the coke development and consequent deposition on the alumina support, leading to a rapid catalyst deactivation because the limited availability of Ni and alumina sites. These results contribute to understand the phenomenon of catalyst deactivation in the steam reforming of bio-oil and set appropriate reaction conditions to mitigate this problem with a NiAl2O4 spinel derived catalyst.This work was carried out with the financial support of the Department of Education, Universities and Investigation of the Basque Government (IT1218-19), theEuropean Commission(HORIZON H2020MSCA RISE 2018. Contract No. 823745), the Ministry of Economy and Competitiveness of the Spanish Government jointly with European Regional Development Funds(AEI/FEDER, UE) (Projects CTQ201568883-R and RTI2018-100771-B-I00), and PhD grant (BES-2016078132) for N. Garcia-Gomez. The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU)

Insights into the Reaction Routes for H2 Formation in the Ethanol Steam Reforming on a Catalyst Derived from NiAl2O4 Spinel

[EN]This work describes the satisfactory performance of a Ni/Al2O3 catalyst derived from NiAl2O4 spinel in ethanol steam reforming and focuses on studying the prevailing reaction routes for H-2 formation in this system. NiAl2O4 spinel was synthesized using a coprecipitation method and reduced at 850 degrees C to obtain a Ni/Al2O3 catalyst. The spinel structure and catalyst were characterized using XRD, TPR, N-2 physisorption, NH3 adsorption and TPD, TPO, SEM, and TEM. The experiments were carried out in a fluidized-bed reactor at 500 or 600 degrees C and different spacetime values, using pure ethanol, ethanol-water, pure ethylene, or ethylene-water feeds. The reaction takes place through two paired routes activated by each catalyst function (metal and acid sites) whose extent is limited by the selective catalyst deactivation. The results evidence that at the beginning of the reaction the main route for the formation of H-2 and carbon (nanotubes) is the dehydration of ethanol on acid sites followed by decomposition of ethylene on the Ni-Al2O3 interface. This route is favored at 500 degrees C. After the rapid deactivation of the catalyst for ethylene decomposition, the route of H-2 formation by steam reforming of ethanol and water gas shift reactions over Ni sites is favored. The morphology of the carbon deposits (nanotubes) allows the catalyst to maintain a notable activity for the latter pathways, with stable formation of H-2 (during 48 h in the experiments carried out). At 600 degrees C, the extent of the gasification reaction of carbon species lowers the carbon material formation. The high formation of carbon material is interesting for the coproduction of H-2 and carbon nanotubes with low CO2 emissions.This work was possible thanks to the financial support of the Department of Education, Universities and Investigation of the Basque Government (IT1218-19), the European Comisssion (HORIZON H2020-MSCA RISE 2018, contract 823745), and the Ministry of Science, Innovation and Universities of the Spanish Government cofinanced with European Regional Development Funds (AEI/FEDER, UE) (Project RTI2018-100771-B-I00). S.I.-V. is thankful for his PhD grant (PRE-2019-090943) awarded by the Ministry of Science, Innovation and Universities. The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU)

Combined effect of bio-oil composition and temperature on the stability of Ni spinel derived catalyst for hydrogen production by steam reforming

A challenge for scaling up hydrogen production by raw bio-oil steam reforming (SR) is the rapid catalyst deactivation that is strongly sensitive to the temperature and bio-oil composition. This work studies the combined effect of both variables on the stability of a Ni/Al2O3 catalyst with high Ni dispersion in the internal and external surfaces of the particles, obtained by reduction of a NiAl2O4. The raw bio-oil composition is modified by (i) removal of phenolic compounds by liquid-liquid extraction or (ii) use of an online pre-reforming step with dolomite. Then, SR tests of the bio-oils at 600 and 700 ?C are carried out in a system with two online units, the first one for controlled deposition of pyrolytic lignin (and also pre-reforming with dolomite) and the second one (fluidized bed reactor) for the SR of the volatile oxygenates. The time on stream evolution of the conversion and products yields is related to the amount, nature and location of coke in the catalyst particles, determined with several techniques. For bio-oils with high or moderate phenolic content (raw or pre-reformed bio-oil, respectively), the SR at 600 ?C leads to a moderate deactivation. However, at 700 ?C, a refractory coke is formed, mainly composed of carbon filaments and turbostratic carbon among them that causes a rapid catalyst deactivation by blocking the external surface of the catalyst particle. Conversely, the removal of phenolic compounds from raw bio-oil leads to a more stable SR operation at 700 ?C, because the formation of turbostratic carbon is slowed down.This work has been carried out with the financial support of the grant RTI2018-100771-B-I00 and PhD grant BES-2016-078132 (N. GarciaG ' omez) funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe", the European Commission (HORIZON H2020MSCA RISE 2018. Contract No. 823745) and the Department of Education, Universities and Investigation of Basque Government (Projects IT1218-19 and IT1645-22). The authors thank for technical and human support provided by SGIker (UPV/EHU/ERDF, EU), and to Calcinor S.A. for supplying the dolomite