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Upgrading of Pyrolysis Oil with Catalytic Hydrotreatment

Upgrading of Pyrolysis Oil with Catalytic Hydrotreatment. Agnes Ardiyanti Erik Heeres. Lignocellulosic biomass (“woody biomass”). Source: wood, grass, sawmill dust Composition (in wt-%) 1 : Potential: 13 EJ (minimum) in 2030. 1 WUR; 2 van Dam, 2007.

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Upgrading of Pyrolysis Oil with Catalytic Hydrotreatment

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  1. Upgrading of Pyrolysis Oilwith Catalytic Hydrotreatment Agnes Ardiyanti Erik Heeres

  2. Lignocellulosic biomass(“woody biomass”) • Source: wood, grass, sawmill dust • Composition (in wt-%)1: • Potential: 13 EJ (minimum) in 2030 1WUR; 2van Dam, 2007

  3. Lignocellulosic biomass – valorisation pathways

  4. Fast Pyrolysis Oil Volatiles Fast Pyrolysis Lignocellulosic biomass Condensables, Fast Pyrolysis Oil 450-600 oC, 1-2 s Char BTG, Enschede Bridgewater et al, Org. Geochem, 30,1999

  5. Fast pyrolysis oil • High oxygen content (up to 50%) • Immiscible with petroleum products • Unstable upon heating and storage (coke formation, repolymerization)

  6. Objective:Deoxygenation of Pyrolysis Oil Co-feedstock for refineries (FCC, hydrocracking) Deoxygenation Fast pyrolysis oil Selected process: Catalytic Hydrotreatment H2 Gas Catalyst, P, T Upgraded Oil Fast pyrolysis oil Water -(CHxOy)- + c H2 -(CHx)- + (H2O, CO2, CH4, CO)

  7. Desired product • Low oxygen content • Low viscosity • Low molecular weight • High aliphatic content • Low coking tendency

  8. Catalytic hydrotreatment Oxygen content H/C, O/C ratio Viscosity Molecular weight Coking tendency Upgraded oil properties: Process variables: Catalyst Heating route Reactor design

  9. Heating route

  10. Why heating route? • Polymerization is very common!  sticky, gooey paste is produced, instead of a nice and liquid oil • Pyrolysis oil contains 30 wt% sugar  when heated: charring Which condition should we apply to suppress this reaction?

  11. Thermal cracking releases O mainly as H2O and CO2 Repolymerisation occurrs O is released as H2O, H2 is consumed Further consumption of H2 saturates the C-C double bonds and cracks the large molecules (similar to coal liquefaction) Pyrolysis Oil Hypothesis1,2 HPTT HDO >250oC, H2, catalyst 175-225oC >250oC, H2, catalyst Low H/C, High Mw High H/C, Low Mw 1 Gagnon, Ind. Eng. Chem. Res 27, 1988 2 Venderbosch, et al, J. Chem. Tech & Biotech, 85, 2009

  12. Experimental set-up • 4 fixed-bed reactors in-series • Feed: forest residue pyrolysis oil (VTT, Finland) • Catalyst: Ru (5%)/C • H2 pressure: 200 bar • Variables: T, WHSV • Analysis: • Elemental composition, TGA, GPC, viscosity BTG, The Netherlands

  13. Effect of process conditions, visual observations • High T in all 4 reactors • Phase separation, clogging after 25 min • Low T in all 4 reactors (‘Stabilization’) • Phase separation at 225 oC or higher • Low T in first reactors, high T at the end (‘Mild Hyd’) • Phase separation, run for 3 days without clogging • ‘2-stage Hyd’ (Hydrotreatment on ‘Mild Hyd’ organic product) • Top organic layer formed, no clogging observed Py-oil Mild Hyd 2-stage Hyd

  14. Van Krevelen plot Py-oil (dry) Stabilization 175 oC Stabilization 225 oC Mild hydrotreatment 2-stage Hydrogenation  dehydration  hydrogenation

  15. Why H/C and O/C? H/C = 1 O/C = 0 HDO HDO H/C = 1.7 O/C = 0 H/C = 1 O/C = 1/6 H/C = 0.5 O/C = 0 Coke formation

  16. Physical properties during further hydrotreatment Mw and TGA stab Mild 2-stage Py-oil Mw residue (TGA) Correlation between Mw and residue weight (TGA)

  17. TG residue, as a function of H/C and O/C TGA residual weight [%] = 81.523 – 57.164 H/C + 32.25 O/C Estimation of physical properties is possible

  18. Change of composition: solvent fractionation • Sugar, HMM decreases after reaction, leaving the apolar, low molecular weight components behind!

  19. 1H-NMR (organic phase) • Groups: aldehydes, aromatics, carbohydrates, methoxy, aliphatics Pyrolysis oil Stabilization 175 oC Mild hydrotreatment 2nd hydrotreatment

  20. Upgraded oil as co-feeding In catalytic cracking • Comparable yields are found for the petroleum feed (Long Residue) and mixture of Long residue+upgraded oil de Miguel Mercader, App. Cat. B 96, 2010

  21. Summary on heating route • Van Krevelen plot indicates the occurence of three subsequent processes: • hydrogenation, • dehydration, • hydrogenation • During hydrotreatment, the Mw, viscosity, and TGA residue-weight of product oil increase during the stabilization step, then decrease at more severe conditions. • High H/C and low O/C of the organic product is desired • The change of composition can be followed by e.g. solvent fractionation and 1H-NMR. • Upgraded oil can be used as co-feeding in refinery units

  22. Catalyst

  23. What type of catalyst? • No specific reaction  homogeneous is not an option • Heterogeneous catalyst: Which support, active metal, preparation?

  24. Support • Regenerable • Stable in water, acid, high temperature: • ZrO2, SiO2 potential • High specific surface area (less important) Active metal • Any metal with hydrogenation activity • Interesting: noble metals (Ru, Pd, Rh), Ni (usually promoted)

  25. Noble metal vs cheaper transition metal • Noble metal: high activity, easy maintenance, very high price • “cheaper” transition metal: lower activity, prone to deactivation, cheap www.kitco.com

  26. Van Krevelen: comparison of activity Pd/C Ru/C

  27. Potential catalyst: NiCu • δ-Al2O3 as support (better stability than γ-Al2O3) • Various Ni/Cu ratio

  28. Hydrogenation activities • Van Krevelen plot is used to calculate the hydrogenation activities, blank experiment as the reference 16Ni2Cu and 13.8Ni6.83Cu are the most active

  29. Why is Cu needed? • Ni is a catalyst for CNT (carbon nanotube) formation produces “carbon whiskers”, decrease the activity • CNT formation is structure sensitive  needs adjacent active sites • Cu makes NixCu1-x alloy, and reduce the crystallite size  the carbon formation is reduced • Cu also helps the reduction

  30. XRD analysis • No Ni(0) was found at 20.8Ni after reduction at 300 oC (reduction temperature of Ni is > 500 oC) • Ni(0) was formed on 13.8Ni6.83Cu after reduction 13.8Ni6.83Cu Ni 20.8Ni NiO Cu does not have HDO activity, but supports the reduction of Ni Reduction was performed at 300 oC and 10 bar of H2

  31. What about the stability?HRTEM Fresh 16.8Ni6.83Cu Spent 16.8Ni6.83Cu Active metal particle size: 10 nm (fresh)  100 nm (spent). ICP showed leaching of Ni, Cu, and Al Dissolution and recrystallisation of NiCu seem to occur

  32. Next? Find other supports … • Carbon, ZrO2, TiO2, etc • Ongoing research

  33. Summary on catalyst selection • A good support selection is a good start • Noble metal vs “cheaper” transition metal • Bimetallic catalyst: effect of composition Heterogeneous catalysts, SϋdChemie

  34. UIC Acknowledgement:Robbie Venderbosch, Vadim Yakovlev, Sofia Khromova, Jelle Wildschut, Anja Oasmaa, Jelmer Westra Boreskov Institute of Catalysis – SB RAS

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