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Pre Treatment Technologies 090507

May 30, 2018



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  • 8/14/2019 Pre Treatment Technologies 090507


    Cellulosic Biomass Chemical Pretreatment

    TechnologiesSeptember 5-6, 2007

    Keith Pauley

    [email protected]


    Chemical and Environmental


    Health and Life Sciences Advanced EngineeringSystems

    Life-changing Research and Development

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    MATRIC 2

    Industrialization of Cellulosic Ethanol

    Five factors control the ability for

    cellulosic ethanol to becomeeconomically viable: Process rateslow process step

    kinetics requires larger capitalequipment costs

    Conversion efficiencypoorutilization of feed materials driveshigher operating costs

    Capital equipment costsexoticMOC, high pressure or temperaturematerials drive adversely impactcost of goods produced

    Operating costshigh temperaturesor pressures require significantamounts of energy

    Product quality/consistencyInconsistency increases the cost ofthe overall process

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    MATRIC 3

    Cellulosic Ethanol Process

    Pretreatment phase, tomake the lignocellulosicmaterial such as woodor straw amenable tohydrolysis

    Cellulose hydrolysis(cellulolysis), to breakdown the moleculesinto sugars

    Separation of the sugarsolution from theresidual materials,

    notably ligninMicrobial fermentationof the sugar solution

    Distillation to produce99.5% pure alcohol

    Chart courtesy of the National Renewable Energy Lab andappears on the Renewable Fuels Association website.
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    MATRIC 4

    Key Processing Cost Elements

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    MATRIC 5

    Pretreatment Technologies

    Mosieret al., Bioresour. Technol. 2005

    Pretreatment technologies aremostly used as precursor toenzymatic hydrolysis Acid Hydrolysis

    Steam Explosion

    Ammonia Fiber Expansion (AFEX)

    Alkaline Wet Oxidation

    Ozone Pretreatment (Ozonolysis)

    Each method has advantages anddisadvantages No one method is best for all types

    of feedstock

    Optimum reaction parameters of thevarious pretreatments, liketemperature, pressure, and reactiontime, are specific to each feedstock

    High yield of sugars does not alwaysresult in high conversion to ethanol lignocellulosic components or

    chemicals used in pretreatment mayform compounds that inhibitfermentation

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    MATRIC 6

    Acid Hydrolysis

    Concentrated or dilute mineralacids penetrate biomass,breaking down hemicelluloseinto monomeric sugars, andremoving part of the lignin First cellulosic pretreatment

    technology dating from Germanyin 1898

    Reaction is carried out atelevated temperatures

    Sulfuric acid is most often used,because it is available at low cost

    Low moisture content ispreferred, since less energy isneeded to heat the biomass


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    MATRIC 7

    Acid Hydrolysis

    Advantages good hemicellulose sugar


    high cellulose digestibility

    removal of hemicellulose andlignin exposes more cellulosefor enzymes to attack

    can solubilize heavy metals

    that may contaminate the


    Disadvantages requires downstream


    some degradation of

    hemicellulose sugars lower yield of sugars

    may form compounds such asacetic acid and furfural which

    inhibit bacteria or yeasts

    during fermentation

    equipment costs are high reactors must be corrosion

    resistant, suitable for high

    temperature and pressures

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    MATRIC 8

    Steam Explosion

    Physico-chemical pretreatmentin which biomass is subjected to

    high-pressure saturated steam,

    followed by rapid


    Expansion of water vapor exertsforce, causing mechanical

    breakdown of biomass

    degrades hemicellulose and

    lignin, thus increasing the

    potential of cellulose hydrolysis

    acids or bases may be

    incorporated into the steam to

    increase hydrolysis
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    MATRIC 9

    Steam Explosion

    Advantages economical for hardwoods

    effectively hydrolyzes


    promotes delignification enlarges pore size in plant

    cells which is beneficial for

    subsequent cellulose


    Disadvantages increases crystallinity of

    amorphous regions of

    cellulose, which decreases

    cellulose digestibility

    high equipment costs

    need for high temperatureand high pressure reactors

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    MATRIC 10

    Ammonia Fiber Expansion (AFEX)

    Physico-chemical pretreatment in which prewetted

    lignocellulosic material is treated with liquid

    anhydrous ammonia at high temperature and

    pressure, then pressure is rapidly released

    Created and patented by Michigan State University

    In contrast to most pretreatments, AFEX does not

    significantly solubilize hemicellulose

    Pressures exceeding 12 atm are required for operation at

    ambient temperature

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    MATRIC 11

    Ammonia Fiber Expansion (AFEX)

    Advantages Much less sugar degradation

    than acid pretreatment

    inhibitor formation is verylimited

    Fast reaction time (~5min)

    Improves hydrolysis rates of

    hemicellulose and cellulose in

    herbaceous crops and grasses

    Ammonia can serve as a

    nitrogen source for organisms

    downstream Ammonia is all volatilized and

    can be recovered as gas

    neutralization is notnecessary

    Disadvantages High energy utilization to

    achieve very high pressures

    Relatively new and undeveloped


    Not proven effective onhardwoods or softwoods

    AFEX effectiveness decreases

    with increasing lignin content

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    MATRIC 12

    Alkaline Wet Oxidation

    Water, sodium carbonate, and oxygen at elevatedtemperature and pressure interact with biomass bybreaking ester bonds Mechanism believed to be saponification of intermolecular

    ester bonds that crosslink hemicelluloses with othercomponents

    Porosity of the material is increased due to the removal ofthe crosslinks, so enzymes can attack sugars more easily

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    MATRIC 13

    Alkaline Wet Oxidation

    Advantages Readily oxidizes lignin

    Significant decrease incellulose crystallinity

    more accessible to enzymes

    Low formation of furfural, amicrobial inhibitor oftenproduced by other pretreatmentmethods

    Disadvantages Degradation of lignin and

    hemicellulose to produce

    carboxylic acids

    hemicellulose sugarslargely decompose, thus

    cannot be converted to


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    MATRIC 14

    Ozone Pretreatment (Ozonolysis)

    Ozone acts primarily by degrading lignin, via attack and

    cleavage of aromatic ring structuresIn one study using wheat straw, ozone pretreatment removed60% of lignin, which increased enzymatic hydrolysis rates five-fold

    Sugimoto et al., Ozone Pretreatment for Ethanol Production Using Lignocellulose Materials, Forestry and

    Forest Products Research Institute

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    MATRIC 15

    Ozone Pretreatment (Ozonolysis)

    Advantages Effective delignification Ozone does not form any toxic

    compounds that inhibithydrolysis

    ozone can be easily

    decomposed to oxygen usinga catalytic bed or hightemperatures, thus extensivedownstream processing isavoided

    Can be conducted at ambienttemperature and pressure

    Disadvantages Requires large amounts of

    ozone, which is expensive

    Generation of carboxylic

    acids from extensive lignin


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    MATRIC 16


    None of the current pretreatment technologies

    described in this presentation meet the criteria for

    economic viability

    Each of these technologies is currently being

    demonstrated at scale

    Further information may change the verdict

    MATRIC is currently developing a proprietary

    chemical pretreatment technology that has the

    potential to satisfy all of the requirements outlinedherein