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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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lignocellulosic biomass woody biomass
Lignocellulosic biomass(“woody biomass”)
  • Source: wood, grass, sawmill dust
  • Composition (in wt-%)1:
  • Potential: 13 EJ (minimum) in 2030

1WUR; 2van Dam, 2007

fast pyrolysis oil
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

fast pyrolysis oil5
Fast pyrolysis oil
  • High oxygen content (up to 50%)
  • Immiscible with petroleum products
  • Unstable upon heating and storage (coke formation, repolymerization)
objective deoxygenation of pyrolysis oil
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)

desired product
Desired product
  • Low oxygen content
  • Low viscosity
  • Low molecular weight
  • High aliphatic content
  • Low coking tendency
catalytic hydrotreatment
Catalytic hydrotreatment

Oxygen content

H/C, O/C ratio

Viscosity

Molecular weight

Coking tendency

Upgraded oil properties:

Process variables:

Catalyst

Heating route

Reactor design

why heating route
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?

pyrolysis oil
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

experimental set up
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

effect of process conditions visual observations
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

van krevelen plot
Van Krevelen plot

Py-oil (dry)

Stabilization 175 oC

Stabilization 225 oC

Mild hydrotreatment

2-stage

Hydrogenation  dehydration  hydrogenation

why h c and o c
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

physical properties during further hydrotreatment
Physical properties during further hydrotreatment

Mw and TGA

stab

Mild

2-stage

Py-oil

Mw

residue (TGA)

Correlation between Mw and residue weight (TGA)

tg residue as a function of h c and o c
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

change of composition solvent fractionation
Change of composition: solvent fractionation
  • Sugar, HMM decreases after reaction, leaving the apolar, low molecular weight components behind!
1 h nmr organic phase
1H-NMR (organic phase)
  • Groups: aldehydes, aromatics, carbohydrates, methoxy, aliphatics

Pyrolysis oil

Stabilization 175 oC

Mild hydrotreatment

2nd hydrotreatment

upgraded oil as co feeding
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

summary on heating route
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
what type of catalyst
What type of catalyst?
  • No specific reaction  homogeneous is not an option
  • Heterogeneous catalyst: Which support, active metal, preparation?
support
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)
noble metal vs cheaper transition metal
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

potential catalyst nicu
Potential catalyst: NiCu
  • δ-Al2O3 as support (better stability than γ-Al2O3)
  • Various Ni/Cu ratio
hydrogenation activities
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

why is cu needed
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
xrd analysis
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

what about the stability hrtem
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

next find other supports
Next? Find other supports …
  • Carbon, ZrO2, TiO2, etc
  • Ongoing research
summary on catalyst selection
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

slide34

UIC

Acknowledgement:Robbie Venderbosch, Vadim Yakovlev, Sofia Khromova, Jelle Wildschut, Anja Oasmaa, Jelmer Westra

Boreskov Institute of Catalysis – SB RAS