Alkaline pretreatement of wheat straw

31 Pages·2010·2.12 MB·English

Alkaline pretreatment of
wheat straw
“Analytical methods for non-wood raw materials and their
products and processes”
COST FP0901 meeting, 19-21 August 2010, Hamburg
Richard Gosselink, Hans van der Kolk, Paulien Harmsen, Robert Bakker
Outline presentation
(cid:1) Wheat straw biorefinery
(cid:1) Alkaline pretreatment
(cid:1) Analytical tools
(cid:1) Highlights results
(cid:1) Available samples for Round Robin COST PF0901
2
Wheat straw biorefinery concept
S L
Clark et al. 2006
3
Pretreatment
(cid:1) Goal
(cid:2) Fractionation of lignocellulosic to cellulose, hemicellulose and
lignin
(cid:2) Make cellulose and hemicellulose fractions more accessible for
enzymatic hydrolysis
(cid:2) Make lignin available for higher-valued products
(cid:1) Numerous processes
(cid:2) Mechanical, chemical, enzymatic
(cid:2) Acids, alkaline, organic solvents
(cid:2) Combinations thereof
4
Alkaline pretreatment (high pH)
(cid:1) Alkali induces swelling of biomass, leading to increase of
internal surface area
(cid:1) Disruption of lignin structure (lignin removal)
(cid:1) Reduction of cellulose crystallinity
(cid:1) Results in improved
accessibility of cellulose and
hemicellulose towards
enzymatic hydrolysis
5
Alkaline pretreatment
(cid:1) Common alkaline pretreatment route
(cid:2) Base as catalyst (NaOH, Ca(OH) , ammonia); T<120 °C
2
(cid:2) Carried out under (close to) atmospheric conditions
(cid:2) Long reaction times (hours)
(cid:2) Need for chemical recycling
(cid:1) Improve alkaline pretreatment
(cid:2) Apply milder process conditions
• Less formation of degradation products (e.g. inhibitors)
• Lower operational costs
(cid:2) Improve accessibility of sugars to enzymes
(cid:2) Obtain lignin of high purity
6
From wheat straw to fermentable sugars
Wheat Enzymatic
Pretreatment Polymeric sugars
straw hydrolysis
Monomeric
Lignin
sugars
(cid:1) Enzymatic hydrolysis Fermentation
(cid:1) Pretreatment efficiency
(cid:2) Conversion of solid fraction
(cid:2) Properties of solid fraction (cellulose-rich)
• Glucan to glucose
Ethanol or
• Biochemical composition
• Xylan to xylose
(cid:2) Properties of liquid fraction
(cid:2) Standard procedure ABE
• Sugars, organic acids and lignins in
• 50 °C, 120h
solution
• Excess of enzyme
• Recovery of lignin
(GC220)
7
Experimental setup
Base case: 4h alkaline pretreatment in stirred reactor
(cid:1) Preliminary experiments (2 L, 70 °C)
(cid:2) Base case
(cid:2) Effect NaOH-concentration
(cid:1) Main experiments (200 L, 90 °C)
(cid:2) Base case
(cid:2) Extrusion
(cid:2) Refining
8
Analytical tools (selection)
(cid:1) Biochemical composition untreated & pretreated straw (solids) 500RnCG070918 #27 [modified by User, 5 peaks manually assigned] ECD_1
(cid:2) Extraction (ASE) 400
300
(cid:2) Carbohydrates (HPAEC-PAD) 5 - Glucose - 19.733
200
(cid:2) Lignin (AIL by weight, ASL by UV)
100
(cid:2) Ash (TGA, ignition) 0 1 - fucose - 5.221 73- R- hAarmabnion4so -es G e- a1- l21a.2c0.t08o00s0e - 61 7- .X07y3 -l3 oMsaen -n 2o4s.e0 5- 0285 -. 6935 2-0 .3648.3033
(cid:2) Proteins (N by Kjehldahl or Dumas, AA by UPLC) -100 min
0.0 10.0 20.0 30.0 40.0 50.0
(cid:2) Morphology (SEM)
0.70
0.60 3934 - 20.121
(cid:2) Cellulose cristallinity (WAXS) 0.50
0.40
AU
(cid:1) Liquids 0.30
0.20
(cid:2) Carbohydrates (monomers, oligomers) 0.10
0.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00Minu1te8s.00 20.00 22.00 24.00 26.00 28.00 30.00 32.00 34.00
(cid:2) Lignin SSaammpplleeNNaammee:: OOrrggaannoossoollvv lliiggnniinn AARRDD 12
(cid:2) Fermentation inhibitors (phenolics, organic acids by LC)
AliphaticOH Internal std SyringylOH
GuaiacylOH
(cid:1) Isolated lignin
p-CoumarylOH
(cid:2) FT-IR
(cid:2) Impurities (carbohydrates, proteins, ash)
COOH
(cid:2) MWD (alkaline SEC)1
(cid:2) Functional groups (31P NMR)1
Cond. Arom.OH
1Gosselink, R.J.A. et al.Holzforschung 2010
9
Pretreatment efficiency Solid fraction
100
Other
Ash (TGA)
%) 80 14 Lignin
17
wt 23 18 Hemicelluloses
(

n Cellulose
o 20
i
it 60 30
s
o 27
p 26
m 24
o 22
c
40
l
a
c
i
m
e
h
oc 20 36 38 44 41
i 33
B
0
Wheat 0% NaOH 6% NaOH 9% NaOH 12% NaOH
straw
NaOH-conc as wt% dry biomass
10