Effect of the physicochemical properties of bimetallic Ni-Cu catalysts for hydrogenation/hydrogenolysis of HMF varying the synthesis method

The evident necessity to transition away from a reliance on fossil resources implies the need to produce high-value-added chemicals from non-conventional sources, such as lignocellulosic biomass. The cellulosic fraction of this resource can be converted into 5-hydroxymethylfurfural (HMF), which can be further transformed to 2,5-bis(hydroxymethyl)furan (BHMF), a polymeric precursor, or 2,5-dimethylfuran (DMF), serving as a substitute or additive of conventional gasoline. This work investigates the effect of the synthesis method of the Ni-Cu/ZrO2 catalyst on the conversion of HMF to BHMF or DMF. The preparation process exerts influence on the dispersion of metals, the acidity of the catalyst, and the interaction of Ni-Cu. Consequently, product selectivity varied depending on the catalyst preparation method, with BHMF being the primary product when the catalyst was prepared through wet impregnation and DMF when precipitation was the chosen synthesis method. Concretely, a BHMF yield of 60 % yield was achieved at 150 °C with the impregnated catalyst, while a 65 % yield was obtained for DMF when employing the precipitation-prepared catalyst. Furthermore, a noticeable effect of the temperature on product selectivity was also detected

Insights into the Nature of the Active Sites of Pt-WOx/Al2O3 Catalysts for Glycerol Hydrogenolysis into 1,3-Propanediol

The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WOx materials are effective catalysts for this transformation, and their activity is often related to the tungsten surface density and Brönsted acidity, although there are discrepancies in this regard. In this work, a series of Pt-WOx/γ-Al2O3 catalysts were prepared by modifying the pH of the solutions used in the active metal impregnation step. The activity–structure relationships, together with the results from the addition of in situ titrants, i.e., 2,6-di-tert-butyl-pyridine or pyridine, helped in elucidating the nature of the bifunctional active sites for the selective production of 1,3-propanediol.This work was supported by the University of the Basque Country (UPV/EHU), European Union, through the European Regional Development Fund (ERDF) (Spanish MICIN Project: RTI2018-094918-BC43), and the Basque Government (IT993-16). Clara Jarauta Cordoba acknowledges financial support from the Spanish Government (BES-2014-069165 and EEBB-I-18-13018)

Effect of atomic substitution on the sodium manganese ferrite thermochemical cycle for hydrogen production

This work presents the effect of atomic substitution on the MnFe2O4-Na2CO3 thermochemical cycle for H-2 production. The non-oxidative decarbonation/carbonation reaction of the MnFe2O4-Na2CO3 mixture is investigated as the starting reference. Repeated cycling results in a 30% loss of reversibility due to an overall reduction of the reactive interfaces. The substitution of Na2CO3 for Li2CO3 decreases the decarbonation onset temperature by about 100 degrees C, but almost no reversibility is observed during the cycles due to the irreversible Li+ intercalation. The effect of partial Mn substitution for Ca, Ni, and Zn is presented. The 5% Zn mixture shows the best decarbonation/carbonation reversibility and is tested for H-2 production together with MnFe2O4-Na2CO3. The reference mixture produces more H-2 during the first cycle (asymptotic to 1.1 vs. 0.7 mmol/g), but its production drastically drops by two orders of magnitude upon cycling and becomes negligible after 5 cycles. By contrast, the Zn-doped mixture exhibits a stable H-2 production of 0.22 mmol/g with no decreasing trend observed from cycle 2 to cycle 5. As result, in the fifth cycle, the Zn-doped mixture produces 23 times more H-2 than MnFe2O4-Na2CO3. Thermogravimetry and X-ray diffraction confirm that doping with Zn significantly improves the regeneration of the reactants.Acknowledgment This Project is funded by the Department of Economic Devel-opment, Sustainability and Environment of the Basque Govern-ment (CICe 2019-KK-2019/00097-and H2BASQUE-KK-2021/00054) . The authors express their sincere gratitude to Cristina Luengo and Mikel Intxaurtieta for their technical support

Influence of morphology of zirconium-doped mesoporous silicas on 5-hydroxymethylfurfural production from mono-, di- and polysaccharides

Different zirconium-doped mesoporous silicas (Zr-KIT-6, Zr-SBA-15, Zr-MCM-41 and Zr-HMS) were synthesized and evaluated in the glucose dehydration to 5-hydroxymethylfurfural (HMF). A Si/Zr molar ratio of 5 was chosen for this purpose after the optimization of this parameter for the KIT-6 support. These materials were characterized by using XRD, N2 sorption, TEM, XPS, NH3-TPD and pyridine adsorption coupled to FTIR spectroscopy. All catalysts were active in glucose dehydration, being HMF the main product, and their catalytic performance is enhanced after CaCl2 addition to the reaction medium. However, Zr-doped mesoporous HMS silica showed the highest values of glucose conversion and HMF yield, mainly at short reaction times, due to this catalyst displayed the highest surface zirconium concentration and its 3D morphology favored the access of glucose molecules to active sites. This fact also caused a faster deactivation due to coke deposition on the catalyst surface, although leaching of zirconium was negligible. The Zr-HMS(5) catalyst could be reused for four catalytic runs without any treatment and the initial catalytic activity could be recovered after washing with water and acetone. This catalyst also demonstrated to be active for hydrolysis of disaccharides and polysaccharides, such as sucrose, maltose, cellobiose, inulin and cellulose, and subsequent dehydration of resulting monomers for HMF production.Spanish Ministry of Economy and Competitiveness (RTI2018-94918-B-C43 and C44 projects), Junta de Andalucía (RNM-1565), FEDER (European Union) funds (UMA18-FEDERJA-171) and Malaga University. C.G.S. also acknowledges FEDER funds for financial suppor

New insights into Mn2O3 based metal oxide granulation technique with enhanced chemical and mechanical stability for thermochemical energy storage in packed bed reactors

El artículo está embargado hasta 24 meses después de su publicación. Hasta el 15 de julio 2024[EN] High temperature thermochemical energy storage still requires a significant research effort. Most of the research has been carried out with materials at lab-scale, and proper material fabrication techniques need to be developed in order to make feasible the upscaling of the technology. Agglomeration, abrasion, or low volumetric energy density are some negative consequences observed when trying to pass from the powder state to the material shape and amount required for a thermochemical reactor. In this work, an established granulation technique is investigated, using a Si-doped manganese oxide as active material to determine the critical parameters that provide the best chemical and mechanical stability of the granules. The granulation process uses a polymeric binder to give consistency to the granules and later, it is removed to create a porous structure to facilitate the oxygen diffusion in and out of the granule. We identified the positive effect of decreasing the bath temperature to increase the volumetric energy density of the granules. Furthermore, it was observed that increasing the mechanical stability through a high temperature treatment did not decrease the chemical stability of the material. In order to provide the first insights into the scalability of the solution, the chemical and mechanical stability of the granules have been satisfactorily checked during 100 redox cycles, out of which 50 were carried out in a home-made lab-scale packed bed reactor with an inner diameter of 13 mm and another 50 redox cycles in a simultaneous thermal analyzer.This work has been supported by the Department of Economic Development and Infrastructures of the Basque government, through the funding of the ELKARTEK CIC Energigune-2017 research program

Solvent and catalyst effect in the formic acid aided lignin-to-liquids

[EN] The effect of the type of solvent, ethanol or water, and a Ru/C catalyst were studied in the formic acid aided lignin conversion. The best results were obtained in the presence of the Ru/C catalyst and using ethanol as solvent at 300 °C and 10 h (i.e. 75.8 wt% of oil and 23.9 wt% of solids). In comparison to the water system, the ethanol system yields a significantly larger amount of oil and, at 300 °C and 10 h, a smaller amount of solids. The main reasons for this positive effect of the ethanol solvent are i) the formation of ethanol-derived esters, ii) C-alkylations of lignin fragments and iii) the generation of more stable lignin derivatives. The Ru/C exhibits significantly higher lignin conversion activity compared to other Ni-based catalysts, especially at 300 °C, which is related to the enhanced activity of the Ru0 sites towards hydrogenolysis, hydrodeoxygenation and alkylation reactions.This project was supported by the Lignoref project group (including The Research Council of Norway (grant no. 190965/S60), Statoil ASA, Borregaard AS, Allskog BA, Cambi AS,Xynergo AS/Norske Skog, Hafslund ASA and Weyland AS)

Simultaneous catalytic de-polymerization and hydrodeoxygenation of lignin in water/formic acid media with Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 as bifunctional catalysts

[EN] The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media using bifunctional Ru/Al2O3, Rh/Al2O3, Pd/Al2O3 catalysts was explored in a batch set-up at different temperatures and reaction times (340–380 ◦C and 2–6 h, respectively). Blank experiments using only gamma–alumina as catalysts and non-catalyzed experiments were also performed and compared with the supported catalysts results. All the supported catalysts significantly improved the oil yields on a lignin basis, with yields up to 91.5 wt% using the Ru catalyst. The main components phenol, cresol, guaiacol, methylguaiacol, catechol, ethylcatechol, syringol and o-vanillin are found in different concentrations depending on the catalytic system. The stable Lewis acidity in the alumina support has been found to be active in terms of de-polymerization of lignin, leading to lower average molecular weight oils. In addition, it was found that alumina plays a significant role in the re-polymerization mechanism of the monomers. The effect of the type of lignin on the final oil and solid yields was also established, demonstrating that lignins produced by basic pretreatment of biomass do not show significant increase in oil yield when catalysts on an acid support like alumina are used. The interpretation is that acid conditions are needed for efficient de-polymerisation of the lignin.We gratefully acknowledge financial support from the Lignoref project group, including The Research Council of Norway(grant no.190965/S60), Statoil ASA, Borregaard AS, Allskog BA, Cambi AS, Xynergo AS/Norske Skog, Hafslund ASA and Weyland AS

Analysis of the effect of temperature reaction time on yields, compositions and oil quality in 3 catalytic and non-catalytic lignin solvolysis in a formic acid/water media using experimental design.

[EN] The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media was explored at different temperatures and reaction times (283–397 °C and 21–700 min, respectively). Non-catalyzed experiments were compared with the effect of three different type of bifunctional catalysts (Pd/Al2O3, Rh/Al2O3 and Ru/Al2O3) and a solid Lewis acid (γ–Al2O3). We demonstrated that surface response methodology (RSM) and principal component analysis (PCA) were an adequate tool to: (i) evaluate the effect of the catalysts, temperature and reaction time in the oil yield, oil quality (H/C and O/C ratios, and Mw) and composition of the oil, (ii) establish the differences and/or similarities between the three bifunctional catalyst and (iii) to determine the role of the noble metal and the alumina support in the reaction system. In addition, the most active catalysts, Ru/Al2O3, and the optimum reaction conditions were determined (i.e. 340 °C and 6 h).Some of this work has been performed as a part of the LignoRef project (“Lignocellulosics as a basis for second generation biofuels and the future biorefinery”). We gratefully acknowledge The Research Council of Norway (grant no. 190965/S60), Statoil ASA, Borregaard Industries Ltd., Allskog BA, Cambi AS, Xynergo AS, Hafslund ASA and Weyland AS for financial support

High-Performance Magnetic Activated Carbon from Solid Waste from Lignin Conversion Processes. 1. Their Use As Adsorbents for CO2

[EN] Lignin is naturally abundant and a renewable precursor with the potential to be used in the production of both chemicals and materials. As many lignin conversion processes suffer from a significant production of solid wastes in the form of hydrochars, this study focused on transforming hydrochars into magnetic activated carbons (MAC). The hydrochars were produced via hydrothermal treatment of lignins together with formic acid. The activation of the hydrochars was performed chemically with KOH with a focus on the optimization of the MACs as adsorbents for CO2. MACs are potentially relevant to carbon capture and storage (CCS) and gas purification processes. In general, the MACs had high specific surface areas (up to 2875 m2/g), high specific pore volumes, and CO2 adsorption capacities of up to 6.0 mmol/g (1 atm, 0 °C). The textual properties of the MACs depended on the temperature of the activation. MACs activated at a temperature of 700 °C had very high ultramicropore volumes, which are relevant for potential adsorption-driven separation of CO2 from N2. Activation at 800 °C led to MACs with larger pores and very high specific surface areas. This temperature-dependent optimization option, combined with the magnetic properties, provided numerous potential applications of the MACs besides those of CCS. The hydrochar was derived from eucalyptus lignin, and the corresponding MACs displayed soft magnetic behavior with coercivities of <100 Oe and saturation magnetization values of 1–10 emu/g.This project was supported by the Swedish Energy Agency and by VR and VINNOVA. YT was supported by the Knut and Alice Wallenberg Foundation (Project: 3DEM-NATUR). GSA was supported by the Knut and Alice Wallenberg Foundation (3DEM-NATUR and Wallenberg Wood Science Center.This project was supported by the Swedish Energy Agency and by VR and VINNOVA. Y.T. was supported by the Knut and Alice Wallenberg Foundation (Project: 3DEM-NATUR). G.S.-A. was supported by the Knut and Alice Wallenberg Foundation (3DEM-NATUR and Wallenberg Wood Science Center)

Thermocatalytic conversion of lignin in an ethanol/formic acid medium with NiMo catalysts: role of the metal and acid sites

[EN] NiMo catalysts supported on different sulfated and non-sulfated aluminas and zirconias were studied for the catalytic conversion of lignin in a formic acid/ethanol medium. All the pre-reduced NiMo-support combinations resulted in high conversion of lignin into bio-oil, with over 60% yield (mass%). The NiMo-sulfated alumina catalyst exhibited the highest activity among all the catalysts studied. The overall reaction mechanism of the catalytic lignin conversion was found to be especially complex. The oil yield and its properties are affected by a combination of successive catalytic reactions that are part of the lignin conversion process. Lignin is first de-polymerized into smaller fragments through the cleavage of the aliphatic ether bonds. This reaction can be either catalyzed by Ni0 species and strong Lewis acid sites within the alumina supports. In the presence of both active species, the Ni0 catalyzed ether bond cleavage is the prevailing reaction mechanism. In a second step, the smaller lignin fragments can be stabilized by catalytic hydrodeoxygenation (HDO) and alkylation reactions that hinder their re-polymerization into char. Mo was found to be especially active for HDO reactions while all the catalysts studied exhibited significant alkylation activity. The final bio-oil yield is strongly dependent on the aliphatic ether bond cleavage rate; the contribution of those monomer stabilization reactions (i.e. HDO and alkylation) being secondary.This project was supported by the Lignoref project group (including The Research Council of Norway (grant no.190965/S60), Statoil ASA, Borregaard AS, Allskog BA, Cambi AS,Xynergo AS/Norske Skog, Hafslund ASA and Weyland AS) and by the Swedish Energy Agency and by VR and VINNOVA