Hydrogen Peroxide BleachingHighlights

State of the Art and Research Direction

Art J. Ragauskas

Hydrogen Peroxide Bleaching

• Background

• Mill Applications

• Research Directions

Peroxide Bleaching: Background

HOO HOOH HOH + OH 2 H2O O2

- e- H+ - e- H+ + e- H+ + e- H+

perhydroxyl radical water & hydroxyl radical

H+ O2- H+ -OOH H+ O-

superoxide anion perhydroxyl anion oxoanion

pKa 4.8 pKa 11.8 pKa 11.9

-active bleaching species is HOO- and derivatives

Peroxide Bleaching: BackgroundH2O2 + M → HO. + HO- + M+

H2O2 + HO- → HO2- + H2O

HO2- + M+ → HO2

. + M

HO2. + HO- → O2

-. + H2O

O2-. + M+ → O2 + M

O2-. + HO. → O2 + HO-

2O2.- + H2O → O2 + HO2

- + HO-

HO. + HO2- → H2O + O2

-.

HO. + M → HO- + M+

HO. + HO. → H2O2

Peroxide chemistry strongly influenced by metals

Peroxide Bleaching: Background

OCH3

OR

O-

HOO-

OCH3

O-R

O-

OHO

OCH3

O-R

O

O

OCH3

OC

O-

OR

OCH3O-

OH

OR

-O

HO- O2

OCH3O

O

O2-

O2 or OHC OH

O-

OCH3

C OH

OOCH3

C OH

OOCH3

COH

OOCH3

O O-

OOCH3

O

C O

HO--O2-

Dakin reaction

Dakin-like reaction

Lignin fragmentation reactions

Addition to quinone structures

-OOH O

O-

R

OHO

O-

R

OOHHO O--OHO

-O

R

OOHO

O

R

Destruction of color bodies

Peroxide Bleaching: Background

Peroxide Bleaching: Background

OO XylanO

HO

OHO

OH

CO2HH H2O2/NaOH

Formed during pulping

• 30 -50% of Southern HW Kappa #

•10 - 20% of Southern SW Kappa #

NR

Peroxide: Mill Applications

Eop– Peroxide 0.1 - 0.5%– Temp.: 55 - 85oC– Time: 50 - 134 min– O2: 0.5 - 0.7%consumed

– first extraction stage– P is largely brightening

chemistry

• Ep– Peroxide: 0.1 - 0.2%– Temp. 65- 85oC– Time: 45 - 120 min.– second extraction stage– Brightening chemistry

• P– Peroxide: 0.5 - 1.5%– Temp. 65- 85oC– Time: 45 - 120 min.

Peroxide: Mill Applications

• PHT– Pre Q stage preferred– Peroxide 0.5 - 3.0%– Temp.

• 105 - 110oC for 5-15 min• 90 - 98oC for 180 - 240 min

– O2: 70 - 120 psi– Stabilizer– Brightening &

delignifying

• PO– Requires pre Q-stage– Peroxide: 0.5 - 3.0%– Temp: 100 - 110oC– Time: 60 - 120 min– O2: 75 - 120 psi– Stabilizer– Brightening &

delignifying

Peroxide: Mill Applications

• North America– Primarily ECF

• D(Eop)DED• D(Eop)DEpD, • OD(Eop)D or OD(Eop)DEpD• D(Ep)DED

• HD storage (0.1 - 0.2% P, pH approx. 9)

P-Stage Mill Applications

• Europe– Greater bleaching sequence diversity in ECF & TCF

• OD(Eop)DED• O/OD(Eop)DP• OQ(Op)PaaQ(PO)• ODQ(PO)• OAZQ(Eop)(PO)• OQPZP

Peroxide Bleaching: Role of metals2.5% P, Q vs. no Q for SW Kraft Pulp

• P-delignification requires metal management via Q-stage

• Favorable M: Mg2+

• Harmful: Fe, Cr, Ni– Mn favorable/harmful

• Note: C/D or D not M sensitive

0

10

20

30

40

50

70 C no Q 70 C Q

% Delignification

% Brightness

Peroxide Bleaching: Role of Temperature 2.5% P Q HW Kraft Pulp

• P* significantly improves peroxide

• P* not just increase in rates

• Capital intensive• Sensitive to M+

– Q stage– yield

05

1015202530354045

30 70 110

130/

C

% Delignification

P-Stage Future Research Directions

• Peroxide Efficiency

•Improved Conditions

•Catalysis

•Modification of fibers

Brightening After OD(EPO)D Kraft HWBrightening After OD(EPO)D Kraft HW

84

86

88

90

92

0.0 0.5 1.0 1.5 2.0 2.5Chemical Charge, % o.d. pulp

Brig

htne

ss

Chlorine Dioxide

Peroxide

Ozone

Peroxide Brightening Effects

80818283848586878889

0.5 1 1.5 2 2.5 3.5

Peroxide Charge (%)

Tap

pi B

righ

tnes

s DEDPDEPD

• D-stage generates active lignin structures for P-stage

Peroxide Activation - Catalyst

Peroxide Bleaching: Research

• Bleaching properties of PHT and PO suggest that a catalyst could improve delignification and/or brightening

• First generation– HO3SOOH, CH3CO3H

Peroxide Bleaching: Research P-activators

O

O O AcNN Ac

AcN

NAc

Ac

Ac

O

OAc

OAc

AcO

AcO

OAc

OAc

OAc

OH

OAc

OAc

OH

Pentacetyl Glucose Diacetin

Diethyl Pyrocarbonate DAED TAED

+ H-O-O - RH + -O-O-AcRAc

All improve a P-stage by 15 - 40% >>stoichiometrically

Peroxide Bleaching: Research P-catalyst

N

N

V O2-

O2-O2

-

NFe

N N

NO

OO

OO

HH

X

X

Mn O Mn

O

N

N N

NN N

O O

Peroxide Bleaching: Research P-catalyst

Catalytic Peroxide Activation: Use of Mn-catalyst to improve alkaline peroxide bleaching of Do SW kraft.

02468

10121416

Do

SWkr

aft

0.5%

P

0.02

%Pc

at

0.2%

Pca

t

1.0%

P

0.02

%Pc

at

0.2%

Pca

t

Kap

pa #

Peroxide Fiber Modification

Strength Effects of O and (PO) on (OZE) SW Kraft

Use an OZE pulp and apply O or (PO)

Bleaching stage enriched acid groups content of pulp fibers

(PO) increased acid groups by 65%

(O) increased acid groups by 37%

Practical Application - Bleaching

0

0.02

0.04

0.06

0.08

300 350 400 450

Scattering Coefficient (cm2/g)

Control

Oxygen/Peroxide

Oxygen

Scot

t-B

ond

(J)

CONCLUSIONS

• Additional acid groups on or near fiber surfaces increased specific bond strength.

• Strength benefit mechanism is not known, but could be intermolecular diffusion.

• The possibility exists to produce stronger, bulkier sheets than by conventional processes.

Peroxide Summary

• Current peroxide bleaching chemistry has dramatically advanced.

• P-stage delignifies but destroys color bodies more effectively.

• Environmentally compatible.

• Sensitive to certain metals.

• Peroxide research is directed at reducing capital requirements.

• Improved peroxide delignification will be achieved.

• New research opportunities in fiber modification.

AcknowledgmentsAcknowledgmentsMember Companies IPSTMember Companies IPST