Pulp Properties Influencing Oxygen Delignification Bleachability A.J. Ragauskas Institute of Paper Science and Technology

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1 Pulp Properties Influencing xygen Delignification Bleachability A.J. Ragauskas Institute of Paper Science and Technology

2 xygen Delignification M i l l i o n T o n s Chemical Usage of North American Bleach Plants Chlorine 2 Delign Total Cl2 Improved environmental and operating cost performance

3 xygen Delignification Increased interest in one and two-stage oxygen delignification Pulp Yield, % Kraft DEopD DEopD 30 () 30 ECF 50 () 40 () KAPPA Improved environmental, operating, and capital cost performance

4 xygen Delignification: Back ground Citations Literature 1960/70s basic engineering & chemistry 1980/early 90s process parameters, energy, environmental, pretreatments, fundamental chemistry, pulp properties Late 1990 s yield, selectivity, process parameters, lignin/carbohydrate chemistry, catalysts

5 Fundamentals of xygen Delignification

6 xygen Delignification: Back ground Lignin - NaH 2 2 H CH 3 - CH 3 CH 3 CH 3 Free Phenolic 2 2 -MeH Fragmented Lignin Acid & ketone groups C 2 - C 2 - H 3 C -

7 xygen Delignification: Back ground 2 + e - H + + e - H + H HH + e - H + HH + H + e - H + 2 HH oxygen perhydroxl radical hydrogen peroxide water & hydroxyl radical water H + 2 superoxide radical H + - H H + perhydroxyl anion oxoanion pka 4.8 pka 11.8 pka 11.9 Several potential bleaching agents with varying sensitivities to reactions with transitional metals

8 xygen Delignification: Back ground Free Phenolic R NaH 2 R 2 - R R H CH 3 CH 3 CH 3 - CH 3 Chain Fragmented Lignin Enriched with carbonyl groups

9 xygen Delignification: Back ground 2 CH 3 H NaH Free Phenolic H MeH H NaH 2 C - 2 (colored) C 2 -

10 Delignification: Lignin Structure Studies xygen delignification leads to a decrease of various types of phenolic groups in residual lignin. However, condensed phenolics survived...to a large extent Jiang & Argyropoulos, JPPS, xygen delignification does not change the residual lignin structure of kraft pulp to a large-degree Moe & Ragauskas. Holzforschung, After the oxygen stage, the isolated residual lignin seems to have a somewhat more intact and less oxidized structure than the corresponding lignin from the unbleached pulp. Gellerstedt, Heuts, & Robert, JPPS, Discrepancies exist between model compound and residual lignin studies

11 Delignification Research bjectives - I Examine use of standard, Pa, and aggressive * delignification conditions on high and low kappa pulps evaluated by: % Delignification Brightness Viscosity Fundamental lignin structures

12 Delignification: Experimental Design Bleaching Conditions Bleach Sequences 75 psig, 60 min., 6% csc High Kappa SW kraft (47) : 2% NaH, 90 o C *: 4% NaH, 105 o C Low Kappa SW kraft (24) : 1% NaH, 90 o C *: 2% NaH, 105 o C Pa: 4% Pa, ph 8, 70 o C distilled peracetic acid High Kappa SW, *, Pa, Pa*, Pa Low Kappa SW, *, Pa, Pa*

13 Delignification Research bjectives-ii Determine how varying and Pa-stages influences residual lignin structure and controls bleachability Lignin Analysis Techniques Isolate residual lignin Analyze residual lignin functional groups: uncondensed phenoxy free phenoxy acid groups quinones carbonyl groups-- ketones

14 , *, and Pa Delignification Results

15 -Delignification High Kappa Delignification Pa equivalent to * >> Pa or Pa* >> * Brightness increases as % delign. increases* Low Kappa Delignification Pa > * Pa treated pulps usually exhibit a higher brightness

16 -Delignification: Viscosity vs. Delignification Delignification (%) Pa* * Pa Pa Low Kappa Pa* * Pa Viscosity (cp) High Kappa Greater delignification incurs greater loss in viscosity Higher kappa pulps yield higher post viscosity

17 -Delignification: Viscosity vs. Brightness Brightness (% IS) Pa* Pa Pa Pa* 40 * * Pa 30 Low kappa High kappa Viscosity (cp) Higher kappa pulp yields higher brightness at a given brightness

18 - Delignification: Summary Pulp Results High kappa SW pulp responded very well to all treatments Pa improved performance >50% delignification is a possible target What is the Chemistry? Color Bodies CH 3 Reactive Sites CH 3 H 3 C H H H CH 3

19 Fate of Quinones and Carbonyl Groups After, *, & Pa

20 - Delignification: Quinones Quinones Lignin P(CH 3 ) 3 H 2 H 3 C H 3 C P "Quinone" Lignin 0.1 BS:47 * Pa Pa* Pa BS:24 * Pa Pa* Quinone (mmol/gr lig.)

21 - Delignification: Quinones 19 F-NMR: Lignin IS Carbonyl + H 2 NNH CF 3 NNH CF 3 Quinone ppm

22 - Delignification: Quinones Quinone (mmol/g Lignin) BS(47) P31 F19 * Pa Pa* Pa D Minor increase in quinones and virtually no increase in carbonyl content of residual lignin

23 - Delignification: Phenoxy Groups Reactive PhH mmol/gr Lign BS:47 :27 Pa:19 Pa:19 Uncond. Phenoxy Condensed Phenoxy *14 Pa*10 :10 CH 3 H Unreactive H 3 C H H CH 3

24 - Delignification: Acid Groups 3 PhH mmol/gr Lign BS:47 :27 Pa:19 Pa:19 *14 Pa*10 :10 BS:24 :14 *:8 Pa*7 Generally Acid groups % delign. Pa introduces more acid groups Note: despite increased lignin solubility resistant to extraction

25 - Delignification: β--aryl Ether Groups PhH mmol/gr Lign H H Me Me Important linkage in pulping & D Not in BS:47 :27 Pa:19 Pa:19 *14 Pa*10 :10 BS:24 :14 *:8 Pa*7 Note: PhMe does not change

26 - Delignification: Residual Lignin Results Primary site of oxidation is unsubstituted phenolics Substituted phenols resistant to oxidation Lignin structure enriched in acid groups Quinones/carbonyls appear not to accumulate during - delign. hence brightness gains not due to their destruction PhMe and β--aryl ether unreactive

27 - Delignification: Implications Enhanced -stages must activate both condensed and unsubstituted PhHs. Cleavage of β--aryl ether may improve delign. Lignin model compounds provided limited practical guidance. Mass transfer limitations could explain portions of residual lignin chemistry.

28 IPST Member Companies L. Allison or