Effect of feedstock moisture on solvent liquefaction of ...Effect of feedstock moisture on solvent...

Post on 09-Jan-2020

2 views 0 download

transcript

Bioeconomy InstituteTCS Conference, Raleigh NC

November 1-4, 2016

Martin R. Haverly, Arpa Ghosh, Robert C. Brown

Funding for this research was provided by the Gary and Donna Hoover Endowment in Mechanical Engineering at Iowa State University and the U.S. Department of Energy under contract #EE0005974.

Effect of feedstock moisture on solvent liquefaction of biomass in non-aqueous solvents

INTRODUCTION

METHODOLOGY

RESULTS & DISCUSSION

CONCLUSIONS FUTURE WORK

Please follow this link to learn more about

research being done at the Bioeconomy Institute

• Energy to dry biomass to 10 wt% moisture represents about 18% of the energy content of fresh

biomass [1]

• Fast pyrolysis typically requires feedstock with moisture content of less than 10 wt% to achieve

necessary heating rates [2]

• Solvent liquefaction performance is relatively independent of heating rates [3]

• Since solvent liquefaction utilizes solvents other than water, excessive moisture in feedstock is

expected to impact performance

• Biomass decomposition reactions in water are expected to be different than those in non-

aqueous solvents due to the unique properties of water at elevated temperatures

• Some solvents such as tetralin are recognized to be hydrogen donors

• Water can hydrolyze ether linkages

• Ionic dissociation of water reaches its maximum around 280 °C – resulting in an increased

concentration of H+ and OH- ions

• The objective of this work was to evaluate the effect of feedstock moisture on solvent

liquefaction of biomass in tetralin

• Experiments were performed in a modified Autoclave reactor with continuous pressure

control and vapor condensation that allowed water and other low boiling point

compounds to vaporize from the reactor

• Solvent: Reagent Grade Tetralin

• Feedstocks:

• Loblolly Pine

• Sigmacell Crystalline Cellulose

• Hardwood Plantrose™ Lignin

• Reaction Temperature: 280 °C

• Reaction Pressure: 15 – 70 bar

• Liquid Analyses: GC-FID, HPLC

• Solid Analyses: FTIR, Elemental

• Feedstock moisture was simulated by oven-drying

the feedstock to <1 wt% moisture and then re-wetting

with specific quantities of deionized water

• Liquid Yields

• Solid Yields

• Liquid yields consistently decreased

with increasing moisture for all 3

feedstocks

• Increasing pressure generally improved

liquid yields – most likely due to

enhanced solvent penetration

• Reduction in liquid yields resulted in

very low levels of detectable products

0%

20%

40%

60%

80%

1% 33% 50%

Liq

uid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Loblolly Pine

29 bar

42 bar

70 bar

0%

10%

20%

30%

40%

50%

60%

1% 5% 33% 50%

Liq

uid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Cellulose

29 bar

42 bar

70 bar

0%

20%

40%

60%

80%

100%

1% 5% 33% 50%

Liq

uid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Lignin

29 bar

42 bar

70 bar

0%

10%

20%

30%

40%

50%

60%

1% 5% 33% 50%

Solid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Cellulose

29 bar

42 bar

70 bar

0%

10%

20%

30%

40%

50%

1% 33% 50%

Solid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Loblolly Pine

29 bar

42 bar

70 bar

• Solid yields consistently increased with

increasing moisture for all 3 feedstocks

• Increasing pressure reduced solids yields

• Cellulose residue congealed into a solid

lump at 50 wt% moisture – below 50

wt% solids existed as a powder

• Lignin residue agglomerated into larger

particles and an acetone-insoluble sludge

Feedstock Moisture (wt%)

Pre

ssu

re (

bar)

Yie

ld (

wt%

)

Monosaccharide Yield

Feedstock Moisture (wt%)

Pre

ssu

re (

bar)

Yie

ld (

wt%

)

Phenolic Monomer Yield

• Some moisture was required to result in

appreciable monosaccharide yields

• At constant pressure, increasing moisture

beyond 5 wt% resulted in a reduction in

monosaccharides – most likely due to

polymerization of monosaccharides and

their derivatives in the presence of water

• Phenolic monomer yields were

significantly reduced when moisture was

increased

• Increasing pressure improved phenolic

monomer yields at all feedstock moisture

levels

• Water balance indicated a consumption of

water during wet lignin liquefaction

• Solids analysis (FTIR, Elemental)

indicated formation of humins

with increasing moisture contents

• Humin formation is acid-catalyzed

– likely hydrogen ions from the

ionic dissociation of water at

reaction conditions

SEM of 50 wt% Moisture Cellulose Solid Residue

0

10

20

30

40

50

60

70

80

100 150 200 250 300

Pre

ssu

re (

bar

)

Temperature (°C)

• Water had a deleterious effect on liquid yields for tetralin solvent liquefaction

resulting in reduction in overall liquid yield as well as reduction in monomer yields

• Solid yields increased at the expense of liquid yields when the feedstock moisture

was increased

• Humin formation from cellulose indicated acid behavior from water due to ionic

dissociation at elevated temperatures and pressures

• Despite only constituting up to 20 wt% of the solvent mixture, water introduced as

feedstock moisture significantly reduced liquid yields and increased solid yields

from the liquefaction of loblolly pine, cellulose, and lignin in tetralin

• Explore the effect of feedstock moisture on alternative non-aqueous solvent systems (e.g. γ–

valerolactone, phenol, etc.)

• Determine the economic impact of fully drying feedstock versus feeding wet feedstock on

product yields and quality

• Investigate energy and economic impact of separating water from product streams

(■) theoretical vapor pressure of pure water at 280 °C

(●) theoretical boiling point of pure water at each operating

pressure

(✕) experimentally determined boiling points for water

0

2E-12

4E-12

6E-12

8E-12

0 100 200 300 400Ion

izat

ion

Co

nst

ant

(Kw

)

Temperature (°C)

Temperature Dependence of Water Ionic Dissociation

Mass of

Dry Feed (g)

Mass of Water

Added (g)

Simulated Feed

Moisture (wt%)

25.0 0.0 1

25.0 1.2 5

25.0 12.5 33

25.0 25.0 50

0%

10%

20%

30%

40%

50%

1% 5% 33% 50%

Solid

Yie

ld (w

t%)

Feedstock Moisture (wt%)

Lignin

29 bar

42 bar

70 bar

• Moisture balance indicated increasing

consumption of water with increasing feed

moisture

• FTIR solids analysis indicated formation of aryl

ketone (1685 cm-1), aryl alkene (1510-1430 cm-1),

and ether linkages (1208-1110 cm-1) in the

presence of moisture – suggesting production of

aromatic rings joined by ether linkages111012081685 1510

b) 33%

c) 50%

% T

ran

smit

tan

ce

1800 750

Wavenumber (cm-1)

a) 1%

1430

FTIR Analysis of Lignin Solids

Proposed Humin Structure

References:

[1] Brown, R.C. and T.R. Brown, Biorenewable resources: engineering new products from agriculture. 2013: John Wiley & Sons.

[2] Wright, M.M., et al., Techno-economic analysis of biomass fast pyrolysis to transportation fuels. Fuel, 2010. 89: p. S2-S10.

[3] Kumar, S., et al., Liquefaction of Lignocellulose: Process Parameter Study To Minimize Heavy Ends. Industrial & Engineering Chemistry Research, 2014. 53(29): p. 11668-11676.