Hydrothermal Pathways to Renewable Fuels...

1

Algae Under Pressure and in Hot Water – Hydrothermal Pathways to

Renewable Fuels

Phillip E. Savage

University of Michigan Chemical Engineering Dept.

2

Energy Usage Trends

society transitions to new energy sources when it improves life - not because of scarcity

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Why Liquid Fuels from Biomass?

~ 15 TW ~ 450 quads

courtesy A. Yokochi - Oregon State Univ

Biomass is recently stored solar energy - renewable energy

We need liquid fuels for transportation.

We can grow enough biomass to meet this need.

Biofuels are renewable - live off the sun in real time.

4

Can algae be a better biofuel feedstock?

  Major issues with terrestrial crops:   Expensive   Food/Feed vs. fuel   Require lots of land,

water, and fertilizer   Less efficient at

photosynthesis   Indirect land use

change Chisti Y. Biodiesel from microalgae. Biotechnol Adv 2007;25(3):294-306.

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Crop Oil Yield (L ha-1 y-1) Soybean 450 Camelina 560 Sunflower 955 Rapeseed 1,190 Jatropha 1,890 Oil Palm 5,950 Microalgae 3,800-50,800

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Microalgae   Aquatic biomass (lots of water)   Can have very high oil content

  along with protein and polysaccharide   No food vs. fuel competition   Water provides structural support (no lignin)   High biomass growth rates

  ~ 5000 gal/acre/yr (~ 10X relative to terrestrial biomass)

  Can grow in salt water (reduce fresh water needed)   Industrial ecology possibilities - co-locate with water treatment and coal-fired power plants

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Algae need much less land than conventional energy crops!

Land Area to Replace 50% of Petroleum Distillates

Adapted from Bryan, et al. (2008)

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Standard approach is dewatering, drying, lipid extraction (e.g., with hexane), and oil processing to make biodiesel or “green” diesel

  $$$$, requires organic solvents, acids, bases

 Let’s use a potentially greener approach!

Biofuel from Microalgae

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Overview  Develop biofuel processes that use wet algae paste   avoid drying   minimal dewatering   no lipid extraction

 Feedstock flexible   high-lipid algae not required   useful for other wet biomass

 Hydrothermal approach - Use high-temperature liquid water to convert biomass into fuels   mimic nature   break down biomacromolecules in algae

HydrothermalProcess

wet biomass fuel product

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Introduction to High-Temperature Water (HTW)

HTW: Liquid H2O at 200 – 350oC (TC = 374oC)

Properties of HTW different from room-temperature water

•  Lower dielectric constant

•  Fewer and less persistent H-bonds

Increased solubility of organic compounds

•  Higher KW = (H+)(OH–) enhanced acid catalysis 0

20

40

60

80

100

0 200 400

T (oC)

Die

lect

ric C

onst

ant

-14

-13

-12

-11

0 100 200 300 400

T (oC)

log

K w0.0001

0.0010

0.0100

0.1000

25 75 125 175 225 275Temperature (oC)

Ben

zene

mol

e fr

acti

on

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Hydrothermal Routes from Wet Algae to Biofuels

Wet Biomass (algae)

Crude Bio-oil Hydrocarbon Fuel or Oil

Liquefaction Upgrade

Fatty Solids

Crude Biodiesel

Hydrocarbon Fuel Deoxygenation

~ 350 °C

CH4, H2 Processes that work with wet biomass (its natural state) and avoid organic solvents could be less costly, more energy efficient, and more environmentally sustainable.

US Patent: 2012/0079760A1

US Patent: 2012/0055077A1

Savage, Science, 2012

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http://www.igb.fraunhofer.de/WWW/Presse/Jahr/2000/en/PI_Algae.en.html

OIL

Hydrothermal Liquefaction

(HTL)

Microalgae Growth

aqueous by-product

liquid fuel

CO2

H2O

Hydrothermal Catalytic

Processing

bio-oil components

Recover energy & nutrients in aqueous stream – essential for energy-positive & sustainable process

Microalgae HTL Process

Energy Recovery

Energy Recovery

N, P recycling

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Hydrothermal Liquefaction of Microalgae

Hydrothermal Liquefaction

wet algal biomass Crude bio-oil

Brown, Duan, Savage, Energy & Fuels, 2010 Valdez, Dickinson, Savage, Energy & Fuels, 2011 Duan, Savage, Ind. Eng. Chem. Res., 2011 Valdez et al., Biomass & Bioenergy, 2012 Valdez & Savage, Algal Research, 2013

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Experimental Procedure

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HTL Products

Aqueous Phase

Biocrude (Organic Phase)

Light Biocrude

Heavy Biocrude

Solids

250°C 300°C

350°C

400°C

0

5

10

15

20

25

30

100 200 300 400 500

Pres

sure

(MPa

)

Temperature (°C)

Liquid Water

Water Vapor

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Elemental Analysis of Bio-Crude

Temp. (°C) C H O N S Dry Algae 43.3 6.0 25.1 6.4 0.53

200 74.6 10.8 11.8 2.4 0.44 300 75.2 10.3 9.8 4.3 0.79 400 76.7 10.3 8.7 3.6 0.91

Crude Oil2 83-87 10-14 0.1-1.5 0.1-2.0 0.5-6.0

• O decreased with temp. • S increased with temp.

2Data from h6p://en.ci9zendium.org/wiki/Petroleum

From Brown, Duan, & Savage., Energy & Fuels. 2010

Nannochloropsis sp.

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0 15 30 45 60 75 900

10

20

30

40

50 Total Biocrude

yield

(wt %

)

time (min)

Biocrude Yields (wt%) from Isothermal HTL

Valdez et al., Biomass & Bioenergy, 2012

50 – 80% energy recovery in biocrude

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Total Ion Chromatogram of Bio-Crude O

OH

O

OH

HO O

OH

HN

C16 fatty acids

350 °C, 60 min

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C & N distributions at 20 min

Light Biocrude

Heavy Biocrude

Water-soluble

Products

Solids Gas

Light Biocrude

Heavy Biocrude Water-

soluble Products

Solids

Light Biocrude

Heavy Biocrude

Water-soluble

Products

Solids Light

Biocrude

Heavy Biocrude

Water-soluble

Products

Solids Gas

Light Biocrude

Heavy Biocrude

Water-soluble

Products

Solids

Light Biocrude

Heavy Biocrude Water-

soluble Products

Solids

C

N

250°C 350°C 400°C

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0 30 60 900

10

20

30

40

50

60

70

80250ºC

Yie

ld (w

t %)

time (min)

SOLAPPLBCHBCGAS

0 30 60 900

10

20

30

40

50

60

70

80300ºC

Yie

ld (w

t %)

time (min)

SOLAPPLBCHBCGAS

0 30 60 900

10

20

30

40

50

60

70

80350ºC

Yie

ld (w

t %)

time (min)

SOLAPPLBCHBCGAS

0 30 60 900

10

20

30

40

50

60

70

80400ºC

Yie

ld (w

t %)

time (min)

SOLAPPLBCHBCGAS

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Solids Aqueous-phase Products

Light Biocrude

Heavy Biocrude Gas

P. Valdez, et al., Hydrothermal Liquefaction of Nannochloropsis sp.: Systematic study of process variables and analysis of the product fractions, Biomass and Bioenergy, (2012)

Reaction Network?

Heavy Biocrude

Solids Light Biocrude

1

2

3

Gas

Aqueous-phase Products

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Reactions of Intermediate Products

4mL Swagelok

Reactor

200mL Induction-heated

Parr Reactor

Light Biocrude

Heavy Biocrude

Solids


+ Gas

350°C, 40min 15 wt % slurry

350°C, 10-40min 5 wt % loading

Product Workup

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Heavy Biocrude


1

2

3

6

Gas


5

4

Reaction of Aqueous-phase Products •  Aqueous-phase produces Light and Heavy Biocrudes and relatively large amounts of CO2 (~3 wt %)

0 10 20 30 400

10

20

30

40

50 Reaction of Solids

yiel

d (w

t %)

time (min)(a)

0 10 20 30 400

20

40

60

80

100

120Reaction of Aqueous�phase Products

yiel

d (w

t %)

time (min)(b)

0 10 20 30 400

20

40

60

80

100 Reaction of Light Biocrude

yiel

d (w

t %)

time (min)(c)

0 10 20 30 400

20

40

60

80

100 Reaction of Heavy Biocrude

yiel

d (w

t %)

time (min)(d)

Solids


Light Biocrude Heavy Biocrude

Gas

T = 350°C

Valdez & Savage, Algal Research, under review

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Heavy Biocrude


1

2

3

6

Gas


5 8

7 4

Reaction of Light Biocrude •  Light Biocrude produces Aqueous-phase and Heavy Biocrude

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0 10 20 30 400

10

20

30

40


yie

ld (

wt

%)

time (min)(a)

0 10 20 30 400

20

40

60

80

100


yie

ld (

wt

%)

time (min)(b)

0 10 20 30 400

20

40

60

80


yie

ld (

wt

%)

time (min)(c)

0 10 20 30 400

20

40

60

80


yie

ld (

wt

%)

time (min)(d)

Solids


Light Biocrude

Heavy Biocrude

Gas

T = 350°C


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Reaction of Heavy Biocrude •  Heavy Biocrude produces Aqueous-phase products, Light Biocrude

and H2, C1, and C2 gases

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Heavy Biocrude


1

2

3

6

Gas

9


5 8

11

7 4

10

0 10 20 30 400

20

40

60

80


yie

ld (

wt

%)

time (min)(a)

0 10 20 30 400

20

40

60

80

100


yie

ld (

wt

%)

time (min)(b)

0 10 20 30 400

20

40

60

80


yie

ld (

wt

%)

time (min)(c)

0 10 20 30 400

20

40

60

80


yie

ld (

wt

%)

time (min)(d)

Solids


Light Biocrude

Heavy Biocrude

Gas

T = 350°C


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Building a Kinetics Model

•  Write & solve governing equations –  xi = mass fraction of each product –  1st order kinetics

•  Estimate rate constants by minimizing objective function

•  Used MATLAB, Constrained, non-linear multivariable function

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dxidt

= ν ijk j xij∑

i∑

Objective Function = xiexp. − xi

calc.( )2

i∑

Heavy Biocrude


1

2

3

6

Gas

9


5 8

11

7 4

10

25

Model & Exptl. Results for HTL

25

0 30 60 900

10

20

30

40

50

60

70

80250ºC

yiel

d (w

t %)

time (min)0 30 60 90

0

10

20

30

40

50

60

70

80300ºC

yiel

d (w

t %)

time (min)

0 30 60 900

10

20

30

40

50

60

70

80350ºC

yiel

d (w

t %)

time (min)0 30 60 90

0

10

20

30

40

50

60

70

80400ºC

yiel

d (w

t %)

time (min)

Solids Aqueous-phase Products

Light Biocrude

Heavy Biocrude

Gas


Gas


Light Biocrude

Heavy Biocrude

Light Biocrude

Heavy Biocrude

Solids


Light Biocrude

Heavy Biocrude

Solids

Gas

Solids

Gas

Solids

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Model Predictions

26 Valdez & Savage, Algal Research, 2013

300 350 400 450 500 5500

10

20

30

40

50

temperature (ºC)

bioc

rude

yie

ld (w

t %)

Biocrude Yield Prediction

Brown et al.3

Faeth et al.18

Li & Savage19

Biocrude yields from liquefaction of Nannochloropsis sp. at 60 min

Gas yields from hydrotherrmal treatment of Nannochloropsis sp. at 60 min

0 20 40 60 800

15

30

45

60

75

90Guan et al.

gas

yiel

d (w

t %)

time (min)

27

Model Predictions

27 Valdez & Savage, Algal Research, 2013

High temp, short time gives highest biocrude yields Rapidly heat to high temperature “Fast” liquefaction

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Fast Hydrothermal Liquefaction •  Nannochloropsis sp. •  1.5 mL stainless steel batch reactors •  Thermocouple dummy reactors •  Setpoint temperatures 300-600°C •  Reaction times 1, 3, 5 min •  Quench in cold water

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Temperature Profile

176 °C

283 °C 297 °C 297 °C

565 °C 593 °C

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Tem

pera

ture

(°C

)

Time (minutes)

300°C Setpoint Temperature


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Total Biocrude Yield (wt.%)

13 ± 7

38 ± 0.5 44 ± 1 66 ± 11

14 ± 4 10 ± 3

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Tem

pera

ture

(°C

)

Time (minutes)



Uncertainty given is standard deviation

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Total Biocrude Yields - 1 minute

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0 10 20 30 40 50 60 70 80

25 300 350 400 450 500 550 600

Bioc

rude

Yiel

d (w

t.% d

.a.f.)

Setpoint Temperature (°C)

Faeth, Valdez & Savage, Energy & Fuels, 2013

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Reaction Ordinate •  Severity index that combines effects of time and

temperature1

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•  Used previously with wood pulping •  Numerical integration using experimental temperature

trajectory

1 T. Rogalinski, T. Ingram, and G. Brunner, e Journal of Supercritical Fluids, 2008, 47, 54–63.

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Total Biocrude Yield with R0

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0 10 20 30 40 50 60 70 80 90

0 2 4 6 8 10 12 14 16

Bioc

urde

Yiel

d (w

t.% d

.a.f.)

Log(R0)

Fast HTL

Unreacted Algae


34 34

0 10 20 30 40 50 60 70 80 90

0 2 4 6 8 10 12 14 16

Bioc

urde

Yiel

d (w

t.% d

.a.f.)

Log(R0)

Fast HTL Conv HTL

Conv. HTL Data from Valdez et al., Biomass and Bioenergy, 2012

Unreacted Algae

Total Biocrude Yield with R0

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Biocrude O/C, N/C Ratios

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0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

0 2 4 6 8 10 12

Atom

ic Ra

tio

Log(R0)

Fast HTL O/C Conv HTL O/C Fast HTL N/C Conv HTL N/C

Algae N/C = 0.145

O/C

N/C

Algae O/C = 0.353


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Model Compound Approach •  Chemical details likely to be obscured starting with algae directly

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Ester Triglycerides

Proteins

Chlorophyll

Carbohydrates

Amino Acid

Phytol Bio-oil

Algae

Specific How do model compounds react individually and interact with each other in HTW?

Sugars

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Phenylalanine Ethyl Oleate Protein Lipids

37

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Phenylalanine Reaction Pathway

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[Changi et al., ChemSUSChem (2012)]

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Ethyl Oleate Hydrolysis

•  Sigmoidal shape - autocatalysis

•  Adding oleic acid increases conversion

•  Catalysis by product (oleic acid) confirmed

Moles Oleic Acid Moles Ethyl Oleate

Conversion (240˚C, 30 minutes)

0 0.07 ± 0.03 0.25 0.27 ± 0.07 0.5 0.41 ± 0.05 1 0.61 ± 0.09

[Changi et al., Ind.Eng.Chem.Res. (2011)]

Effect of Added Oleic Acid

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Phenylalanine + Ethyl Oleate

40

41

•  Phenylethylamine (primary product) yield decreases with added ester

•  Styrene, 2-phenylethanol (2° products) yields increase with added ester

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Reactions enhanced in presence of ester

Effect of Adding Ethyl Oleate


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Effect of Adding Phenylalanine •  Formation of new products - oleic acid amides, phenylacetaldehyde

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0

0.005

0.01

0.015

0.02

0.025

0.0 0.2 1.0 5.0

Mol

ar Y

ield

of P

heny

lace

tald

ehyd

e

Ethyl Oleate : Phenylalanine

At 350 °C and 10 min


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Reaction Network for Binary System

43 [Changi et al., ChemSUSChem (2012)]

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Reaction Network for Binary System

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Increased Rates


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Parity Plot for Binary System

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Insights to Chemistry of Algae Liquefaction

•  Oligomerization in amino acid system at high temperatures

–  Decreases quality of bio-oil

–  Use hydrogenation strategy to prevent oligomers

•  Binary mixtures of amino acids and esters form amides

–  Decreases yield of fatty acid components in bio-oil

–  Adds nitrogen to crude bio-oil

–  Rates of individual reactions increase

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Summary •  Hydrothermal Liquefaction (HTL) converts wet

biomass into crude bio-oil •  Reaction network for HTL of algae established

–  Reaction modeling, reactor engineering

•  Fast HTL produces biocrude in higher yield and shorter time than conventional HTL –  66 wt.% yield in 1 min.

•  Reaction ordinate unifies results from conventional and fast HTL

•  Model compounds provide insights into HTL chemistry

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•  Peter Valdez, Julia Faeth, Shujauddin Changi •  NSF – EFRI – 0937992 •  EPA, NSF Graduate Fellowships •  College of Engineering – University of Michigan •  Rackham Graduate School – University of Michigan

Acknowledgements

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