Arndal, Trine M. H.

Gabrielsend, Jostein

Gaur, Abhijeet

Grunwaldt, Jan-Dierk

Høj, Martin

Jensen, Anker Degn

Pintos, Delfina Garcia

Prüssmann, Tim

Studt, Felix

W. Hansen, Thomas

Catalytic hydropyrolysis combines fast pyrolysis with catalytic upgrading by hydrodeoxygenation (HDO) in a single step for the production of fuel oil from biomass in which reactive pyrolysis vapors are upgraded before condensation. Catalyst activity and lifetime is challenged by carbon deposition and by the presence of alkali, nitrogen, sulfur and water. In this contribution, a combined experimental, characterization (in-situ Quick-EXAFS) and theoretical (DFT) study of catalytic HDO of biomass pyrolysis model compounds over MoS2 based catalysts is presented with emphasis on the influence of water and H2S.<br/

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Downloaded from orbit.dtu.dk on: Jan 01, 2018Influence of Promotor, H2O and H2S on the Hydrodeoxygenation of Biomass PyrolysisVapor over MoS2 CatalystsDabros, Trine Marie Hartmann; Høj, Martin; Gaur, Abhijeet; Prüssmann, Tim ; Pintos, Delfina Garcia;Studt, Felix; Gabrielsend, Jostein ; Grunwaldt, Jan-Dierk; Jensen, Anker DegnPublication date:2017Document VersionPeer reviewed versionLink back to DTU OrbitCitation (APA):Arndal, T. M. H., Høj, M., Gaur, A., Prüssmann, T., Pintos, D. G., Studt, F., ... Jensen, A. D. (2017). Influence ofPromotor, H2O and H2S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS2 Catalysts. Abstractfrom 25th North American Catalysis Society Meeting, Denver, United States.Influence of Promotor, H2O and H2S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS2 Catalysts  Trine M. H. Arndal1, Martin Høj1, Abhijeet Gaur2, Tim Prüssmann2, Delfina G. Pintos3, Felix Studt2, Jostein Gabrielsen4, Jan-Dierk Grunwaldt2 and Anker D. Jensen1* 1Technical University of Denmark (DTU), Kgs. Lyngby, DK-2800 (Denmark) 2Karlsruhe Institute of Technology (KIT), Karlsruhe, D-76131 (Germany) 3Stanford University, Stanford, CA-94305 (USA) 4Haldor Topsøe A/S, Kgs. Lyngby, DK-2800 (Denmark) *aj@kt.dtu.dk  Introduction Catalytic hydropyrolysis combines fast pyrolysis with catalytic upgrading by hydrodeoxygenation (HDO) in a single step for the production of fuel oil from biomass in which reactive pyrolysis vapors are upgraded before condensation. Catalyst activity and lifetime is challenged by carbon deposition and by the presence of alkali, nitrogen, sulfur and water. In this contribution, a combined experimental, characterization (in-situ Quick-EXAFS) and theoretical (DFT) study of catalytic HDO of biomass pyrolysis model compounds over MoS2 based catalysts is presented with emphasis on the influence of water and H2S.  Materials and Methods MoS2/MgAl2O4 and Co(/Ni)-MoS2/MgAl2O4 catalysts with 3.3 wt% Mo and Co(/Ni):Mo molar ratio = 0.3 have been prepared by incipient wetness impregnation and sulfidation with 10-12% H2S/H2 at 360-400°C. Ethylene glycol (EG) is a simple model polyol representing the cellulosic fraction of biomass. Catalytic HDO tests were conducted in a fixed bed reactor at 350-450°C, 28 bar H2 and 545-2200 ppm H2S (mcat = 0.5-4 g, feedEG = 0.14 mL/min, EG WHSV = 2.3-19 h-1, 40 barg, balance N2). Products were separated into gas (online analysis by GC/TCD) and liquid (offline analysis by GC-MS/FID). DFT calculations were used to predict the influence of varying H2O/H2S ratios on the stability of the sulfide/oxide phases and reaction pathways. The Quantum Espresso code was applied in combination with the BEEF-vdW exchange correlation functional. In-situ Quick-EXAFS was conducted at the SLS SuperXAS beamline [1] at the Co-, Ni- and Mo-K-edge of prepared catalysts during sulfidation and subsequent exposure to varying H2O/H2S ratios at 400-450°C. Catalysts and support material have also been analyzed using other techniques such as ICP-OES, NH3-TPD, XRD, BET and Raman spectroscopy.   Results and Discussion Co(/Ni)-MoS2/MgAl2O4 catalysts were active and moderately selective for EG HDO. 100% conversion was obtained for 50 h on stream at 400°C with 545 ppm H2S and EG WHSV = 2.3 h-1. At these conditions, a moderate HDO product yield (ethane and ethylene) of 40-45% was observed together with an undesired cracking (C1: CO, CO2, CH4) yield of 30-35%. Catalyst deactivation is believed to be caused by carbon deposition (3.5-9.5 wt% on spent catalysts) and exchange of S by O at the active MoS2 edges. S-O exchanges may be mitigated with a higher H2S concentration. In fact, a higher H2S concentration reactivated and stabilized the catalyst and improved the HDO/cracking selectivity in experiments with EG WHSV = 19 h-1, see Figure 1 (A+B). DFT has however indicated that a too high concentration of H2S inhibits S-vacancy formation at the MoS2 S-edge thereby potentially limiting HDO. In-situ Quick-EXAFS has thus been applied to study the effect of varying H2O/H2S ratios on catalyst composition. The magnitude of the Fourier Transformed in-situ EXAFS spectra (Figure 1C) shows the transition from oxide (MoOx) to sulfide (MoS2) during catalyst sulfidation. The EXAFS fit for the resulting sulfide phase shows contributions from Mo-S (2.40Å) CN = 4.2+0.3 and Mo-Mo (3.15Å) CN = 0.37+0.07. The presence of a small Mo-O contribution (Mo-O (1.61Å) CN = 0.24+0.07) indicates incomplete sulfidation which is possibly caused by interaction of highly dispersed MoS2 crystallites with the support.     Figure 1 TOS profiles for EG conversion and gas product yields for Ni-MoS2/MgAl2O4 (A) and Co-MoS2/MgAl2O4 (B) at 400°C, EG WHSV = 19 h-1, 28 bar H2, 545-2200 ppm H2S (noted with red text) and total pressure 40 barg. Magnitude of the Fourier Transformed in-situ EXAFS spectra (Mo-K-edge) for in-situ sulfidation (C) of MoS2/MgAl2O4 going from oxide (MoOx, black), through transition phases (red) to a sulfide (MoS2, green).  DFT calculations have shown that promotion with Ni compared to Co results in more adsorbed H atoms at the S-edge of MoS2. This higher hydrogen availability could explain the higher yield of ethane compared to ethylene observed for Ni-MoS2/MgAl2O4 (Figure 1A). DFT calculations for EG HDO reaction pathways are being conducted.  Significance To our knowledge, this is the first catalytic HDO study which combines the experimental and theoretical investigation with advanced in-situ XAS characterization to unravel the influence of promotion and H2O/H2S on catalytic HDO over MoS2 catalysts. Understanding the mechanisms behind this influence is a key step in optimizing the catalytic hydropyrolysis process.  References 1. Müller, O., Nachtegaal, M., Just, J., Lützenkirchen-Hecht, D., Frahm, R., J. Synchrotron Rad. 23, 260 (2016). (A)                                                                                       (C)  (B)                                                                                       TOS [h]  R [Å]       Yield  [%]                   Yield [%] 545 ppm   2170 ppm   550 ppm   2200 ppm   C2H6  C1  C2H4  14      11    8     5     2  14      11    8     5     2  100      75    50     25     0  100      75    50     25     0  0    20   40   60   80  100   120    140 0         20          40        60         80 TOS [h]  0        1        2        3        4        5 RT  200°C  400°C   Conv.  [%]                   Conv. [%] 

Influence of Promotor, H2O and H2S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS2 Catalysts

Catalytic hydropyrolysis combines fast pyrolysis with catalytic upgrading by hydrodeoxygenation (HDO) in a single step for the production of fuel oil from biomass in which reactive pyrolysis vapors are upgraded before condensation. Catalyst activity and lifetime is challenged by carbon deposition and by the presence of alkali, nitrogen, sulfur and water. In this contribution, a combined experimental, characterization (in-situ Extended X-Ray Absorption Fine Structure, EXAFS) and theoretical (Density Functional Theory, DFT) study of catalytic HDO of biomass model compounds over MoS2 based catalysts is presented with emphasis on the influence of water and H2S

General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from orbit.dtu.dk on: Jan 01, 2018Influence of Promotor, H2O and H2S on the Hydrodeoxygenation of Biomass PyrolysisVapor over MoS2 CatalystsDabros, Trine Marie Hartmann; Høj, Martin; Gaur, Abhijeet; Prüssmann, Tim ; Pintos, Delfina Garcia;Studt, Felix; Gabrielsend, Jostein ; Grunwaldt, Jan-Dierk; W. Hansen, Thomas ; Jensen, Anker DegnPublication date:2017Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Arndal, T. M. H., Høj, M., Gaur, A., Prüssmann, T., Pintos, D. G., Studt, F., ... Jensen, A. D. (2017). Influence ofPromotor, H2O and H2S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS2 Catalysts. Abstractfrom 13th European Congress on Catalysis (EUROPACAT 2017), Florence, Italy. Influence of Promotor, H2O and H2S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS2 Catalysts Trine M. H. Arndala, Martin Høja, Abhijeet Gaurb, Tim Prüssmannb, Delfina G. Pintosc, Felix Studtb, Jostein Gabrielsend, Jan-Dierk Grunwaldtb, Thomas W. Hansena and Anker D. Jensena* aTechnical University of Denmark (DTU), Kgs. Lyngby, DK-2800, Denmark bKarlsruhe Institute of Technology (KIT), Karlsruhe, D-76131, Germany cStanford University, Stanford, CA-94305, USA dHaldor Topsøe A/S, Kgs. Lyngby, DK-2800, Denmark *aj@kt.dtu.dk Catalytic hydropyrolysis combines fast pyrolysis with catalytic upgrading by hydrodeoxygenation (HDO) in a single step for the production of fuel oil from biomass in which reactive pyrolysis vapors are upgraded before condensation. Catalyst activity and lifetime is challenged by carbon deposition and by the presence of alkali, nitrogen, sulfur and water. In this contribution, a combined experimental, characterization (in-situ Extended X-Ray Absorption Fine Structure, EXAFS) and theoretical (Density Functional Theory, DFT) study of catalytic HDO of biomass model compounds over MoS2 based catalysts is presented with emphasis on the influence of water and H2S. 1. Scope The aim of this work is to study the influence of promotion and H2O/H2S on catalytic HDO of biomass model compounds and their mixtures over MoS2 catalysts through a combined experimental and theoretical investigation. MoS2/MgAl2O4 and Co(/Ni)-MoS2/MgAl2O4 catalysts with 3.3 wt% Mo and Co(/Ni):Mo molar ratio = 0.3 have been prepared by incipient wetness impregnation and sulfidation with 10-12% H2S/H2 at 360-400°C. Ethylene glycol (EG) is a simple model polyol representing the cellulosic fraction of biomass. Catalytic HDO tests were conducted in a fixed bed reactor at 350-450°C, 28 bar H2 and 545-2200 ppm H2S (mcat = 0.5-4 g, feedEG = 0.14 mL/min, EG Weight Hourly Space Velocity (WHSV) = 2.3-19 h-1, 40 barg, balance N2). Products were separated into gas (online analysis by GC-TCD) and liquid (offline analysis by GC-MS/FID). DFT calculations were used to predict the influence of varying H2O/H2S ratios on the stability of the sulfide/oxide phases and reaction pathways. The Quantum Espresso code1 was applied in combination with the BEEF-vdW exchange correlation functional2. In-situ Quick-EXAFS was conducted at the Swiss Light Source (SLS) SuperXAS beamline3 at the Co-, Ni- and Mo- K-edge of prepared catalysts during sulfidation and subsequent exposure to varying H2O/H2S ratios at 400-450°C using an appropriate in-situ cell4. Catalysts and support material have also been analyzed using other techniques such as Transmission Electron Microscopy (TEM), ICP-OES, NH3-TPD, XRD, BET and Raman spectroscopy. 2. Results and discussion Co(/Ni)-MoS2/MgAl2O4 catalysts were active and moderately selective for EG HDO. 100% conversion was obtained for 50 h on stream at 400°C with 545 ppm H2S and EG WHSV = 2.3 h-1. At these conditions, a moderate HDO product yield (ethane and ethylene) of 40-45% was observed together with an undesired cracking (C1: CO, CO2, CH4) yield of 30-35%. EG conversion over un-promoted MoS2/MgAl2O4 (WHSV = 6.2 h-1) showed a conversion >80% and an initial HDO product yield of 55%, but with a rapid deactivation giving < 22% yield of HDO products after 25 h on stream. Catalyst deactivation is believed to be caused by carbon deposition (3.5-9.5 wt% on spent catalysts) and exchange of S by O at the active MoS2 edges. S-O exchanges may be mitigated with a higher H2S concentration. In fact, a higher H2S concentration reactivated and stabilized the catalyst and improved the HDO/cracking selectivity in experiments with EG WHSV = 19 h-1, see Figure 1. DFT calculations have however indicated that a too high concentration of H2S inhibits S-vacancy formation at the MoS2 S-edge thereby potentially limiting HDO. In-situ Quick-EXAFS has thus been applied to study the effect of varying H2O/H2S ratios on catalyst composition. The magnitude of the Fourier Transformed in-situ EXAFS spectra (Figure 2A) shows the transition from oxide (MoOx) to sulfide (MoS2) during catalyst sulfidation. The EXAFS fit for the resulting sulfide phase shows contributions from Mo-S (2.40Å) with Coordination Number (CN) = 4.2+0.3 and Mo-Mo (3.15Å) with CN = 0.37+0.07. The presence of a small Mo-O contribution (Mo-O (1.61Å), CN = 0.24+0.07) together with the low Mo-S CN could indicate incomplete sulfidation and is possibly caused by interaction between the small and highly dispersed MoS2 crystallites and the support. The morphology was validated with High-Angle Annular Dark-Field Scanning TEM (HAADF-STEM), see Figure 3B. Figure 1. Time on stream (TOS) profiles for EG conversion (□) and gas product yields (ethane, ethylene and C1) for Ni-MoS2/MgAl2O4 (A) and Co-MoS2/MgAl2O4 (B) at 400°C, EG WHSV = 19 h-1, 28 bar H2, 545-2200 ppm H2S (noted with red text) and total pressure 40 barg. 2 0 n m Figure 2. A) Magnitude of the Fourier Transformed in-situ EXAFS spectra (Mo-K-edge) for in-situ sulfidation of MoS2/MgAl2O4 going from oxide (MoOx, black), through transition phases (red) to a sulfide (MoS2, green). B) HAADF-STEM image of Co-MoS2/MgAl2O4. Co-MoS2 crystallites are visible as bright slabs. DFT calculations indicate that promotion with Ni compared to Co results in more adsorbed H atoms at the S-edge of MoS2. This higher hydrogen availability could explain the higher yield of ethane compared to ethylene observed for Ni-MoS2/MgAl2O4 (Figure 1A). DFT calculations for EG HDO reaction pathways are being conducted. Future experiments will be performed with mixtures of ethylene glycol and other oxygenates such as acetic acid and phenol to study e.g. inhibition by competitive adsorption. 3. Conclusions To our knowledge, this is the first catalytic HDO study which combines the experimental and theoretical investigation with advanced in-situ EXAFS characterization to unravel the influence of promotion and H2O/H2S on catalytic HDO over MoS2 catalysts. Understanding the mechanisms behind this influence is a key step in optimizing the catalytic hydropyrolysis process. References 1. P. Giannozzi, S. Baroni, N. Bonini, M. Calandra, R. Car, C. Cavazzoni, D. Ceresoli, G. L. Chiarotti, M. Cococcioni, I. Dabo, et al. J. Phys.: Condens. Matter 2009, 21, 395502. 2. J. Wellendorff, K. T. Lundgaard, A. Møgelhøj, V. Petzold, D. D. Landis, J. K. Nørskov, T. Bligaard, K. W. Jacobsen, Phys. Rev. B 2012, 85, 235149. 3. O. Müller, M. Nachtegaal, J. Just, D. Lützenkirchen-Hecht, R. Frahm, J. Synchrotron Rad. 2016, 23, 260-266. 4. J.-D. Grunwaldt, N. van Vegten, A. Baiker, Chem. Commun. 2007, 44, 4635-4637. (A) (B) 20 nm (A) (B)

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Influence of Promotor, H<sub>2</sub>O and H<sub>2</sub>S on the Hydrodeoxygenation of Biomass Pyrolysis Vapor over MoS<sub>2</sub> Catalysts

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