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Biocrude from Switchgrass

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  • Biocrude Production from Switchgrass using Subcritical Water

    Sandeep Kumar and Ram B. Gupta*

    [email protected]

    Department of Chemical Engineering, Auburn University, Auburn, AL

  • 2

    Outline

    IntroductionLignocellulosic biomass and possible conversion pathways

    Water as reaction medium

    ObjectiveLiquefaction of switchgrass to produce biocrude

    Experimental studySemi-continuous reactor set up

    Results

    Conclusion

  • Cellulose38 - 50%

    23 - 32%

    Lignin15 - 25%

    Other 5 -15%

    (Extractives, Ash etc)

    Hemicellulose

    http://www.nrel.gov

    SwitchgrassCorn Stover Bagasse

    Wood chips

    Lignocellulosic Biomass

    3

  • 4

    Biochemical Thermochemical

    Major pathways for biomass utilization

    Pretreatment (< 220 C)

    PhysicalPhysio-chemical

    ChemicalHydrothermal

    EnzymaticHydrolysis

    Fermentation

    Pyrolysis(450-600C)

    Pyrolysis Bio-oil

    Ethanol

    Gasification(600-1000C)

    HydrothermalLiquefaction(250-350C)

    Hydrocarbons Hydrogen Chemicals

    F-T Synthesis

    Hydrogen

    Aqueous-phase

    reforming

    Supercritical water

    reforming

    Liquid alkanes Hydrogen

    Sugars Chemical

  • Biocrude and hydrothermal liquefaction

    BiocrudeAqueous carbohydrate solution (Oxygenated hydrocarbons)

    Transportable through pipelines to central biorefining facility

    Easier to gasify

    Can be concentrated

    AdvantagesNo drying of biomass

    Not dependent on the type of biomass

    Wet residue from other processes can be used

    5

  • Sub- and supercritical water as a reaction medium

    6

    (J. W. Tester et. al. In Emerging technologies in hazardous waste management III, volume 518 of ACS Symposium Series, pages 3576. 1993)

    200-350 C region conducive for acid/base reactions !

    25 MPaDecreased Density

    Dielectric constant

    Viscosity

    Increased Ionization constant

    Diffusivity

    Tunable properties

    ()

    Ioni

    zatio

    n co

    nsta

    nt(K

    w)

  • Objectives

    Study the liquefaction of switchgrass in subcritical

    water

    Effect of temperature, and catalyst K2CO3 on

    switchgrass liquefaction

    Study the rate of solubilization of swithgrass

    7

  • Reaction pathway of biomass

    8

    Cellulose

    Cleavage of glycosidic linkages and endwise degradation (peeling)

    cellulose glucose decomposition products

    Hemicellulose

    Swelling, dissolution, peeling and glycosidic cleavage reactions

    Lignin

    Cleavage of aryl ether linkages, fragmentation, dissolution and

    re-polymerization

    Biomass components interact with each other, and leads

    to a very complex chemistry

  • 9

    Experimental set-up

  • Experimental details

    Semi-continuous flow reactor235 - 260 C, 1.5 ml/min liquid flow

    Reactor details

    Switchgrass

    Size: - 40 to + 60 mesh (0.25 - 0.42 mm)

    Composition: Cellulose (37%), Hemicellulose (23%), Lignin (25%)10

    0

    100

    200

    300

    0 25 50 75Tem

    pera

    ture

    (C)

    Time, min

    t

    Heating cycle

    SwitchgrassFrit (0.002mm)

    Reactor(9/16 ID tube)

    Liquid in Biocrude

  • Product analysesLiquid product (Biocrude)

    Total organic carbon (TOC) in liquid

    Sugar and degradation products analysis by HPLC

    Solid precipitates collected in the liquid products

    X-ray diffraction

    Composition analysis

    Switchgrass residue

    Composition analysis

    X-ray diffraction for crystallinity

    11

    Biocrude

    Solidprecipitate

    Switchgrassresidue

  • Results: Experiments at 260 C and 23.5 MPa

    No catalyst (K2CO3)82% of switchgrass solubilized in 50 min.

    Maximum TOC (31,520 ppm) within 10 min.

    Catalyst (K2CO3)

    0.25 and 0.50 wt% input resulted in char like solids and

    plugged the reactor

    High temperature and presence of catalyst promoted

    dehydration of biomass materials

    Maximum TOC (44,500 ppm) within 10 min.

    12Reduce the severity of treatment

  • Experiments at 235 C, 13.8 MPa in subcritical water

    0

    10000

    20000

    30000

    40000

    0 10 20 30 40 50 60

    TOC

    , ppm

    Reaction time, min

    0 % K2CO3

    Liquid flow rate = 1.5 ml/min

    Peak TOC within 10 min

    Total organic carbon(TOC) profile in the liquid product

    13

  • Experiments at 235 C, 13.8 MPa (K2CO3 Catalyst)

    0

    10000

    20000

    30000

    40000

    0 10 20 30 40 50 60

    TOC

    , ppm

    Reaction time, min

    0 % K2CO3

    0.15 % K2CO3

    Liquid flow rate = 1.5 ml/min

    K2CO3 enhanced the rate of liquefaction

    Total organic carbon(TOC) profile in the liquid product

    14

  • Experiments at 235 C, 13.8 MPa (catalyst)

    0

    10000

    20000

    30000

    40000

    0 10 20 30 40 50 60

    TOC

    , ppm

    Reaction time, min

    0 % K2CO3

    0.15 % K2CO3

    Total organic carbon(TOC) profile in the liquid product

    Cellulose

    Maximum TOC from pure cellulose after 10 min

    Zhang et. al 2004

    Lignin

    Hemicellulose

    Cellulose

    15

  • 16

    0

    20

    40

    60

    80

    100

    67.172.2

    83.4

    Solu

    biliz

    atio

    n(%

    )Solubilization of switchgrass (235 C)

    5 min 10 min 20 min

    80% of switchgrass solubilized after 20 min. of treatment

    13.8 MPa, 0.15 wt% K2CO3Liquid flow rate = 1.5 ml/min

  • Composition of Switchgrass residue

    Char like solids were deposited over the residue biomass

    0

    25

    50

    75

    Cellulose Lignin

    33

    5932

    66

    Com

    posi

    tion

    (%)

    5 min 20 min

    17

  • XRD Pattern of switchgrass residue

    Untreated

    5 min

    20 min

    10 20 30

    Inte

    nsity

    Angle (2)

    CrystallanityUntreated 51%

    5 min 56.6%

    20 min 64.3%

    Crystallinity of cellulose increased in residual biomass

    18

  • XRD pattern of the solid precipitates

    Solids collected from the product solution (235 C, 13.8 MPa, 20 min)

    Sugars in solid residue is 22%

    0

    3000

    6000

    9000

    10 15 20 25 30 35

    Inte

    nsity

    (CPS

    )

    Angle (2)

    Solid precipitate

    Switchgrass(untreated)

    19

  • Biocrude composition (at 235C, 20 min)

    20

    SugarProducts

    15%

    HMF4%

    Furfural6%

    Organic acids17%

    Unidentified Compounds

    57%

    Sugar productsGlucose & oligomers

    Xylose & oligomers

    Organic acidsLactic acid

    Formic acid

    Acetic acid

    Unidentified compoundsSugar degradation products

    Other organic acids

    Acid soluble lignin etc

    Biocrude

  • Future work and challenges

    Future work

    Development of lab scale continuous process set up

    for biomass liquefaction

    Challenges

    Pumping of biomass slurry at high pressure

    Presence of solid and liquid in the downstream

    21

  • Conclusions

    At higher temperature (260C), biomass tended to dehydrate

    and formed char like solid products in the presence of K2CO3

    Presence of 0.15 wt% of K2CO3 (235C) catalyzed the

    liquefaction of switchgrass

    More than 80% of switchgrass could be solubilized in 20 min

    and biocrude having more than 3wt% carbon could be

    produced within 10 min. of reaction

    Re-polymerization of lignin and deposition of char like solids

    over the residual biomass inhibited the complete hydrolysis of

    cellulose

    22

  • Acknowledgements

    National Science Foundation

    (grant NSF-CBET-0828269)

    Alabama Center for Paper and Bioresource

    Engineering

    23

    Thank you !!

    Slide Number 1OutlineSlide Number 3Slide Number 4Biocrude and hydrothermal liquefactionSub- and supercritical water as a reaction mediumObjectivesReaction pathway of biomassSlide Number 9Experimental detailsProduct analysesResults: Experiments at 260 C and 23.5 MPaExperiments at 235 C, 13.8 MPa in subcritical waterExperiments at 235 C, 13.8 MPa (K2CO3 Catalyst)Experiments at 235 C, 13.8 MPa (catalyst)Solubilization of switchgrass (235 C)Composition of Switchgrass residueXRD Pattern of switchgrass residueXRD pattern of the solid precipitatesBiocrude composition (at 235C, 20 min)Future work and challengesConclusionsAcknowledgements

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