h2o2 decomposition

7/30/2019 H2O2 Decomposition

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ACHIEVING MAXIMUM PEROXIDE BLEACHING RESPONSE THROUGH PROPER SELECTION OF

pH

A Comparison of Decomposition and Bleaching Reaction Rates

Jeff A Stevens Dr. Jeffery S. Hsieh

PhD Student Director

Pulp and Paper Engineering

School of Chemical Engineering

Georgia Institute of Technology

Atlanta, GA 30332-0100

ABSTRACT

Hydrogen peroxide bleaching performance can be significantly improved by using higher temperature pressurized

peroxide bleaching systems. Higher temperatures also have the disadvantage of increasing the rate of peroxide

decomposition, thus leading to lower brightnesses and lower pulp viscosities. The rates of both peroxide

decomposition and peroxide bleaching of kraft pulp are strongly dependent on the pH of the bleaching liquor. The

optimum balance at which decomposition reactions dominate over bleaching reactions at various temperatures willdetermine the potential success in any peroxide or pressurized peroxide bleaching process.

This work compares the rates of chromophore elimination and delignification to the rates of peroxide decomposition

and viscosity loss. The pH at which a peroxide stage is run strongly influences the overall selectivity of the process

at a given temperature. An empirical kinetic model for peroxide bleaching has shown that the activation energy for

brightening is higher than for decomposition.

INTRODUCTION

Interest in hydrogen peroxide bleaching of kraft pulp has increased in recent years due to a general effort to reduce

the amount of chlorine-containing compounds used in bleaching. Hydrogen peroxide is a versatile bleaching agent

that can be used to brighten high yield pulps, delignify kraft pulps, and brighten and delignify pulps with relatively

low lignin contents.

Hydrogen peroxide can be used in both ECF and TCF bleaching sequences. In ECF bleaching, peroxide is used to

reduce the amount of chlorine dioxide necessary to achieve high final brightness. Peroxide is primarily used as an

enhancement chemical in the first alkaline extraction stage. In this manner, the extraction stage becomes a combined

lignin separation/oxidation process. Peroxide can also be used in a dedicated stage to either delignify pulp in a

partially closed OQP bleaching sequence before ClO2 brightening or at the end of the bleaching sequence to increase

the final brightness. In TCF bleaching, peroxide is used to delignify and to brighten the pulp after oxygen and/or

oxygen/ozone bleaching sequences.

The most significant development in peroxide bleaching technology is the advent of pressurized peroxide bleaching.

In pressurized peroxide bleaching (PO), the rate of the bleaching reaction is significantly increased through increases

in temperature to up to 120C. To carry this out, the peroxide stage must be run under pressure to keep the bleach

solution from boiling up and causing lack of bleaching agent mass transfer to the pulp

1

. The higher temperaturesallow the peroxide stage to develop high brightnesses in a relatively short (1-2 hrs) reaction time. Pressurized

peroxide bleaching also allows a higher brightness ceiling to be achieved2.

One recent development that utilizes the increased initial rate of reaction in peroxide bleaching is known as the P HTprocess

3,4,5. In this process, the reaction is split up into two phases. Phase one is carried out under high temperature

pressurized conditions in a short upflow retention tube. The reaction time is from 5 to 15 minutes at 110C. In

phase two, the pulp is depressurized into a downflow tower to complete the reaction. The downflow section operates

at 90 - 98C, and the retention time is 2 to 3 hours. One advantage of the PHT process is that it is relatively easy to


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retrofit into existing mill equipment. A traditional Eop or D upflow/downflow tower can be modified by refitting the

uplflow tube with a pressure control system, and by using increased steam flow in the steam mixer.

In all these processes, the hydrogen peroxide delignification and brightening reactions take place in competition to

decomposition reactions which can waste peroxide as well as degrade pulp strength. The decomposition of hydrogen

peroxide can be represented in general by the reaction

H2O2 O2 + H2O (1)

where the decomposition products are oxygen and water. The mechanism of this decomposition is rather complex.

It is widely known that peroxide decomposes through one or several possible free radical mechanisms6,7,8

in which

the primary radical species formed are OH., O2

-., and HOO

.. These radicals are then utilized in the pulp bleaching

mechanism for degradation of the lignin6,9

, but they also cause cellulose degradation9. Cellulose degradation, as

indicated by a loss in CED viscosity, is increased when peroxide decomposition reactions are not controlled in some

manner.

It is also widely known that peroxide decomposition is increased in the presence of transition metals such as Fe2+

,

Cu2+

, and Mn2+

, which exist naturally in wood pulp6,10

. This is the reason for metals management processes in

peroxide bleaching11,12

. Proper management of metals involves complexing the harmful metal ions with a chelating

agent and/or an acidic washing step. After a metal management process, the levels of transition metals are reducedso that decomposition is minimized and free radical formation is more controlled, thus higher pulp brightnesses and

better viscosity maintenance is achieved.

Hydrogen peroxide decomposition is also affected by pH in a base-catalyzed reaction mechanism13,14

. This

mechanism becomes significant in peroxide bleaching, as the bleaching reaction is carried out under alkaline

conditions both for delignification and brightening. The primary reactions in the alkaline peroxide system are shown

as equations (2) - (4).

H2O2 HO2-+ H

+(2)

H2O2 + OH-

HO2-+ H2O (3)

H2O2 + HO2- O2 + OH

-+ H2O (4)

In peroxide brightening, the perhydroxyl anion, HO2-, reacts with chromophoric groups to eliminate color and

thereby brighten the pulp10,15

. Thus, reactions that bleach the pulp are in competition with reactions which waste

peroxide and degrade pulp strength.

This work examines the rates at which these competing reactions take place. Oxygen pressure rise in a sealed reactor

is used to observe the rate at which peroxide decomposes, and brightness and viscosity results are obtained from

running peroxide bleaching reactions for defined retention times. Since these reactions are all pH and temperature

dependent, the effect of initial pH at differing reaction temperatures is examined.

CONCENTRATION AND TEMPERATURE EFFECTS ON pH

Due to the complex reactions in Equations 2 - 4, the pH is determiend by peroxide concentration, hydroxide ion

concentration, and temperature. Various chemical reaction equilibria are used to calculate the pH of alkaline

peroxide solutions at various temperatures. From the definition of pH and from the equilibrium reaction in Equation

3, the pH of an alkaline peroxide solution may be calculated by Equation 5.

pH = pKw + log{[HO2-]/[H2O2]K3} (5)

where the perhydroxyl anion concentration can be calculated by Equation 6.

[HO2-] = {z-(z

2-4[H2O2]T[OH

-]T)

}/2 (6)


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where [OH-]T = [OH

-] + [HO2

-]

z = [H2O2]T + [OH-]T + 1/K3.

Table 1 gives the equilibrium constants for the alkaline peroxide reactions16

for use in Equations (5) and (6).

Table 1. Equilibrium Constants for Peroxide Reactions

Temp (C) Kreaction 2 Kreaction 3 Kreaction 450 4.94e-12 91.05 4.14e28

70 8.02e-12 50.68 1.06e27

90 1.11e-11 29.26 4.47e25

110 1.35e-11 17.41 2.83e24

From these equations, the amount of total sodium hydroxide charge necessary to reach a given pH at a given

temperature can be calculated. Figure 1 shows the amount of sodium hydroxide required to reach a given pH for

10% consistency operations at varying initial peroxide charge and temperatures.

8.5 9 9.5 10 10.5 11 11.5 12 12.50

5

10

15

20

pH

NaOH, % on pulp

1%, 90

3%, 90

1%, 110

4%, 110

Figure 1. Caustic charge to reach given pH.

As shown in Figure 1, as peroxide charge is increased, more caustic is required to reach a given pH. Also,

temperature increases will increase the amount of caustic required to reach a given pH. For example, in a 10%

consistency pressurized peroxide reactor operating at 110C, to bleach at an initial pH of 11.5 with a peroxide

charge of 30 kg/ton requires to total caustic charge of 11.6 % on o.d. pulp. For a pH of 10.5, only 1.93% NaOH is

required. Thus, operation at higher pH is more expensive, and runs the risk of cellulose damage due to alkaline

peeling reactions of the carbohydrates. The remainder of this paper discusses the results of bleaching oxygen

delignified and chelated pulp over the pH range from 10.5 to 11.5 at temperatures ranging from 80 to 110C

EXPERIMENTAL

Oxygen delignified softwood kraft pulp with an initial kappa number of 17.4 and an initial viscosity of 23.6 mPa s

was used in this study. This pulp was well washed with distilled water and then chelated to remove the harmful

transition metals. Chelation was carried out using a charge of 0.5% EDTA on oven dry pulp. The chelation stage

was conducted at 5% consistency, 90C for 60 minutes at a pH of 4.5-5.0 as suggested in literature 17. After the

chelation stage, the pulp was washed with 5 volumes of distilled water to displace water in the pulp. The pulp was

then pressed to about 25% consistency and stored in a cold room for later use in the peroxide stages.

The peroxide bleaching runs for the kinetic study were run in a CRS model 1015S stainless steel reactor, as

described previously18. This reactor is well sealed, and an Omega model PX 425 pressure transducer connected to a

panel meter was used to monitor the pressure in the reactor. The panel meter was connected to a computer which

recorded the pressure data for later study. A schematic of this setup appears in Figure 2.


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P

pH T

Injection

H2O21/2 O2 + H2O

O2 (aq)

O2 (g)

Pulp

Slurry

To computer

Figure 2. CRS Reactor showing principle of oxygenpressure rise measurement.

Figure 1 also shows the principle behind measuring the rate of decomposition. As peroxide decomposes, oxygen is

released into the headspace of the sealed reactor. Since the free volume in the reactor is constant, the rate of pressure

rise is directly related to the rate of peroxide decomposition. These principles have been discussed in more detail

elsewhere18

.

The majority of the peroxide bleaching experiments were carried out at 0.5% consistency at equivalent peroxide

concentrations as found in 10% consistency bleaching. This was to ensure that each fiber would be exposed to the

same concentration of hydrogen peroxide and perhydroxyl anions. Also, as discussed by Hsu and Hsieh19, the use of

very low consistency insures the measurement of the intrinsic rate of a bleaching reaction. The use of very low

consistencies in this work also allows easy determination of the oxygen pressure rise, and thus allows comparisons to

be made between bleaching kinetics and decomposition kinetics. Other bleaching runs were made at 5% and 10%consistencies to confirm that the results presented are valid at more traditional operating conditions.

Peroxide bleaching experiments were run at 80, 90, and 110C over a pH ranging from 10.5 - 11.5. Two different

levels of peroxide concentration, corresponding to 10 kg/ton and 30 kg/ton peroxide charge on 10% consistency

pulp, were examined. For each experiment, pulp and water were loaded into the reactor and brought to the reaction

temperature under 40 psig nitrogen pressure. When the temperature reached steady-state, the nitrogen was bled from

the reactor, and the bleach reagents were fed under pressure into the reactor. The turbine rotated at 300 rpm

throughout the duration of the experiment. The peroxide bleaching experiments were run for total reaction times of

5, 15, 30, 60, and 120 minutes, after which the pulp was washed and the residual chemicals were determined. Total

reaction time refers to the time from injection of the chemicals to the time the pulp was washed.

Brightness and viscosity values were obtained using standard TAPPI testing methods. Residual peroxide

concentrations were determined through iodometric titration of residual bleach liquors, and hydroxide concentrationswere obtained through titration of the residual liquors with HCl, and using pH measurements. Lignin contents of the

bleached pulps were calculated from UV absorbance values at 280 nm of pulp samples dissolved in phosphoric acid.

This analytical technique was adapted from a study by Weinstock et al20

.


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RESULTS AND DISCUSSION

Effect of Initial pH on Peroxide Bleaching Response

Hydrogen peroxide bleaching yields the highest brightness gains when the pH is about 10.5 or higher21

.

Decomposition, which leads to pulp strength loss as well as a waste of peroxide, is also affected by the pH of the

bleach solution. Figure 3 shows how the rate of peroxide decomposition is affected by pH at various temperatures.The rate of decomposition is calculated from the rate expression developed previously18

.

This plot also shows that the pH at which the decomposition rate is maximized shifts downward slightly as the

temperature increases. Over the temperature range, however, the pH at which decomposition is maximized is about

11. In terms of peroxide bleaching, this suggests that operation at the pH at which decomposition reactions are

maximized may be harmful to the pulp strength.

8 9 10 11 12 130

0.00002

0.00004

0.00006

0.00008

0.0001

pH

Initial Rate, M/s

110C

90C

70C

Figure 3. The effect of pH and temperature on the rate of peroxide decomposition.

Peroxide bleaching batch kinetic data are presented in Figure 4 and Figure 5. Figure 4 shows the brightness gain

with time at 90C at pH 10.5, 11.0, and 11.5. In the remainder of this work, the pH at which a reaction was run

refers to the initial pH at the reaction temperature. The peroxide concentration is .098 mol/L, or equivalent to 30

kg/ton peroxide charge on 10% consistency pulp. Figure 5 shows the viscosity loss with time for these same runs. It

is easy to see that the pH at which the peroxide bleaching is run does not significantly impact the brightness gain in

this pH range. However, as the pH is increased, the pulp viscosity decreases due to more rapid decomposition

reactions. Although the base-catalyzed peroxide decomposition rate goes through a maximum at~pH 11, the

viscosity loss is greater at pH 11.5. This is explained by transition metal-catalyzed decomposition, which increases

as pH rises14

.

These results show that as the pH is increased, the rate of brightening and the rate of viscosity loss are different.

Thus, it is more advantageous from a selectivity point of view to operate at a pH closer to 10.5 than to 11. This is

just below the pH at which decomposition reactions are maximized. Figure 6 shows the selectivities for each pH run

at 90C, .098M H2O2 initial concentration. The selectivities are plotted as viscosity vs. chromophore content, Ck,

measured as m2/kg, as described above.


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0 20 40 60 80 100 120 14030

40

50

60

70

80

Time, min

Brightness

Figure 4. Brightness gain in peroxide bleaching. Conditions in these runs are 90C, .098M H2O2, pH 10.5, 11.0,

11.5.

0 20 40 60 80 100 120 1405

10

15

20

25

Time, min

Viscosity, cp

pH 10.5

pH 11.0

pH 11.5

Figure 5. Viscosity loss with time in peroxide bleaching. These are the same runs as in Figure 3.

0 2 4 6 8 10 12 145

10

15

20

25

Ck, m2/kg

Viscosity, cp

pH 10.5

pH 11.0

pH 11.5

Figure 6. Selectivity plots for 90C peroxide bleaching.

[H2O2]o = .098M

Figure 6 confirms that the selectivity of the peroxide bleaching reaction is optimized at a pH of 10.5. Figure 6 shows

the reason for the lowered selectivities. The rate of peroxide decomposition is measured as pressure rise in the CRS

reactor. Figure 7 shows pressure rise curves for each of these experiments over a one hour time period. The curve


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with the sharpest upward slope is the 11.5 pH pressure rise curve. The middle curve represents the pressure rise at a

pH of 11.0. In this run, the reactor developed a small leak at the shaft seal, which was later repaired. For this

reason, the pH 11 curve does not lie between the curves for pH 10.5 and 11.5. Similar analysis at shorter time

periods indicates that the pressure rise for pH 11.0 is between those for pH 10.5 and pH 11.5, however, indicating

that the pressure rise increases with pH in peroxide bleaching.

0 500 1,000 1,500 2,000 2,500 3,0000

20

40

60

80

Time, sec

Delta P, psig

10.5 pH

11.5 pH

11 pH

Figure 7. Pressure rise curves in 0.5% consistency

peroxide bleaching at 90C. [H2O2]o = .098M.

This result is significant in that we are able to observe in situ the rate of peroxide decomposition during a bleaching

reaction. Thus, the competitive reaction rates can be examined. Also, we are able to determine the optimum pH for

bleaching, based on a comparison between bleaching, decomposition, and viscosity loss rates. Figures 8-11 show

similar results obtained at 110C with .098 mol/L initial peroxide concentration.

0 1,000 2,000 3,000 4,00030

40

50

60

70

80

Time, sec

Brightness

pH 10.5

pH 11

Figure 8. Brightness gain at 110C using .098mol/L initial H2O2 concentration, 10.5 and 11.0 initial pH.


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0 1,000 2,000 3,000 4,0005

10

15

20

25

Time, sec

Viscosity, cp

pH 10.5

pH 11

Figure 9. Viscosity loss at 110C for .098M initial H2O2

0 2 4 6 8 10 12 145

10

15

20

25

Ck, m2/kg

Viscosity, cp

pH 11

pH 10.5

Figure 10. Selectivity plots for 110C peroxide bleaching. Initial [H2O2] = .098 mol/L.

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,0000

20

40

60

80

100

120

140

Time, sec

Delta P, psig

10.5 pH

11 pH

Figure 11. Pressure rise curves for peroxide bleaching at 110C. [H2O2]= .098 mol/L initially.

At 110C, only one run was made with a reaction time of 15 minutes. In this run, all the peroxide decomposed

within the first five minutes, as indicated by a leveling off of the reactor pressure. This means that peroxide

bleaching at a pH greater than 11 at 110C is undersireable due to a very high rate of uncontrolled decomposition.

The brightness of this pulp was 61 after 15 minutes, but the viscosity is only 5.4 cp, meaning that the fast

decomposition destroyed the carbohydrates in the pulp. As mentioned earlier, to achieve this high pH requires a


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large quantity of sodium hydroxide, making this conditiion undesireable from an operations and economic standpoint

as well.

One interesting note from the pressure rise data is that there is not a huge increase in the rate of pressure rise when

the pH goes from 10.5 to 11.0, but from 11.0 to 11.5 in 90C data, there is a more significant increase in the rate of

pressure rise. This further illustrates the need for good pH control in peroxide bleaching.

Effect of Temperature on Peroxide Bleaching Response

Hydrogen peroxide bleaching can be significantly enhanced by increasing the temperature and pressure of the

reaction. All the experiments presented here have the same initial starting pressure (40 psig), but the effect of

temperature on the reaction rates is examined. Figure 12 shows the brightening response at an initial pH of 10.5 and

an initial peroxide concentration of .098 mol/L over temperatures ranging from 80 to 110C.

0 20 40 60 80 100 120 14030

40

50

60

70

80

Time, min

Brightness

80C

90C110C

Figure 12. The effect of temperature on brightening rates in peroxide bleaching. Initial [H2O2] = .098M, initial pH

= 10.5

This data indicates that there may not be a linear increase in brightening response as temperature increases,

indicating a possible shift in the reaction mechanism. Figure 13 shows the impact of temperature on the bleaching

performance, as indicated by data taken after 15 minutes of reaction time. As other authors have noted3, when the

temperature is increased over 100C, there is a sharper increase in the reaction rate than would be expected by

Arrhenius kinetics. The data in Figures 12 and 13 agree with these authors conclusions. Specifically, peroxide

consumption is significantly increased over the low temperature runs, but this is due in part to the increased rate of

decomposition as well as the increased bleaching rate.

H2O2 consumption

brightness

75 80 85 90 95 100 105 110 11545

50

55

60

65

70

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Temperuture, C

Brightness [H2O2], g/L

Figure 13. Peroxide bleaching results after 15 minutes reaction time. Initial [H2O2] = .098M, initial pH = 10.5.


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The viscosity is more significantly impacted by temperatures greater than 100C. As shown in Figure 15, the

viscosity reduction at 110C is significantly sharper than at either 80 or 90C, due to the faster rate of

decomposition.

.098M H2O2, pH = 10.5 initially

0 20 40 60 80 100 120 1408

10

12

14

16

18

20

22

24

Time, min

Viscosity

80C

90C

110C

Figure 14. Effect of temperature on the rate of viscosity loss during peroxide bleaching at an initial pH of 10.5.

While the viscosities at 110C are still acceptable from a strengh point of view, they represent a significant problem

from a process engineering standpoint. During an upset period in the mill it would be extremely difficult to control

the fiber strength exiting the bleach plant if it is run on the edge of the viscosity envelope. This makes the PHTprocess more attractive. The initial rate of bleaching can be increased, and then the temperature is cut back for less

destructive, slower brightening. This can be used to help protect the pulp viscosity while still allowing for higher

brightness targets in existing bleach plant equipment.

The lignin contents of the pulps after these peroxide stages is presented in Figure 15. These lignin contents were

obtained by using UV spectrophotometry. The pulps were dissolved in 83% phosphoric acid, and the absorbances of

the solutions at 280 nm were obtained. An absorbance coefficient of 20 L/g cm was used to calculate the lignincontent from the absorbance using Beers law

20.

Figure 16 shows the relationship between the UV lignin content and the pulp brightness after the peroxide stage. The

data in Figure 16 is from many peroxide stages over a range of temperatures, initial pHs, and initial peroxide

concentrations. This data indicates that the reaction mechanism for brightening is also responsible for delignification

in peroxide bleaching after an oxygen delignification stage. This data shows that, when delignification is a

parameter of interest, on-line brightness analysis can be used to directly predict the actual lignin content.


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.098M H2O2, pH = 10.5 initially

0 20 40 60 80 100 120 1400.5

1

1.5

2

2.5

3

Time, min

% Lignin

80C

90C

110C

Figure 15. Lignin reduction kinetics of peroxide bleaching at initial pH = 10.5, initial [H2O2] = .098 mol/L

0.5 1 1.5 2 2.5 330

40

50

60

70

80

% Lignin

Brightness

Figure 16. The relationship between lignin content and pulp brightness after peroxide bleaching.

Empirical Brightening Kinetic Model

An empirical model has been developed from the bleaching results. This model is based on the dynamic condition of

constantly changing chromophore content, pH, and peroxide concentration during the run. The chromophore content

for each sample is calculated from the Kubelka-Munk theory23

. The Kubelka-Munk equation relates the reflectance

of a pulp handsheet to the chromophore content, as described by the absorption coefficient, Ck.

Ck= s(1-Roo)2/2Roo (7)

The light scattering coefficient is calculated by measuring the refletctance at 457 nm of a single sheet under a black

background, and normalizing this reflectance with the sheet basis weight. As noted by Teder and Tormund24

, certain

darker pulps will give an inaccurate measure of the chromophore content when directly applied to the Kubelka-Munkequation. For this reason, darker samples of pulp are mixed with samples of a known absorption coefficient. The

relationship between the absorption coefficient of the mixture with the absorption coefficient of the unknown sample

is given by Equation 8.

Ck, sample = (Ck, mixture - Ck, known(1-x))/x (8)

where x is the fraction of pulp with the unknown absorption coefficient.


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0 2 4 6 8 10 1255

60

65

70

75

1

1.2

1.4

1.6

1.8

2

% Consistency

Brightness g/L H2O2

Brightness [H2O2], g/L

Figure 18. The effect of run consistency on peroxide bleaching results after one hour retention time.

It was further established that the viscosity results were similar at the 5% and 10% consistency levels. These results

indicate that there is little mass transfer effect when the concentration of bleaching agents is kept constant over a

consistency range. Further results in this area will be discussed in a future paper.

CONCLUSIONS

The rates of the competing reactions in peroxide bleaching of oxygen delignified pulp have been presented. This

work shows that the pH does not significantly affect the rate of brightening, but it does affect the viscosity of the

pulp by speeding up decomposition reactions. The proper pH for a peroxide stage should be controlled to a pH of

around 10.5 for viscosity protection.

Raising the temperature also significantly increases the rate of bleaching in a peroxide stage. In pressurized

peroxide bleaching at temperatures over 100C, pH and metal control is especially crucial to the success of the

peroxide stage from a pulp strength standpoint. Thus, the PHT concept takes advantage of both high temperature and

low temperature operating conditions.

An empirical kinetic model for peroxide bleaching softwood kraft pulp after oxygen delignification has been

developed. The rate is second order in chromophore content. The activation energy of bleaching reactions is higher

than for base-catalyzed peroxide decomposition reactions. High temperature peroxide bleaching is thus more

efficient at converting chromophores using hydrogen peroxide.

ACKNOWLEDGEMENTS

The authors express thanks for support from the International Paper Company Foundation and the Fluor Daniel

Foundation as well as the Georgia Tech Pulp and Paper Foundation.

REFERENCES

1. Devenyns, J., Renders, A., Carlier, J., and Walsh, P., Proc. 1995 Pulping Conf.: Chicago, p. 281.

2. Germgard, U., and Norden, S., Proc 1994 Int. Bleaching Conf., Vancouver, B.C.: p. 53.

3. Roy, B., van Lierop, B., Berry, R., and Audet, A., Proc.1995 Tappi Pulping Conference, Chicago: 771.

4. Van Lierop, B., Roy, B., Berry, R., Audet, A., and Shackford, L., Proc 1996 Int Bleaching Conf, Washington,

D.C.: p. 303.

5. Breed, D., and Salvador, E., Proc. 1996 Pulping Conf., Nashville, TN. p. 567.


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6. Abbot, J. and Brown, D.,Int Journ Chem Kinet. 22: 963 (1990).

7. Abbot, J. JPPS. 17(1): 10 (1991).

8. Agnemo, R. and Gellerstedt, G., Acta Chem Scand. B33: 337 (1979).

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10. Backman, L., and Gellerstadt, G., Proc 1993 ISWPC: p. 223.

11. Bryant, P. S., and Edwards, L. L., JPPS, 22(1): p. J37, (1996).

12. Van Lierop, B., Liebergott, N., and Faubert, M. G.,JPPS, 20(7): p. J193, (1994).

13. Duke, F. and Haas, T. J Phys. Chem. 65: 304 (1961).

14. Colodette, J., Rothenberg, S., and Dence, C.,JPPS. 14(6): 126 (1988).

15. Gellerstadt, G., Gartner, A., and Heuts, L., Proc 1996 Int. Bleaching Conf., Washington, D.C., p. 505.

16. Roine, A.HSC Chemistry for Windows. 1994.

17. Gellerstedt. G., and Pettersson, I., J. Wood Chem. Technol. 2(3): p. 231. (1982).

18. Stevens, J., and Hsieh, J., Proc 1996 Pulping Conf. Nashville, TN. p. 559. (1996).

19. Hsu, C., and Hsieh, J., AIChE J. 34(1): p. 116. (1988).

20. Weinstock, I., Minor, J., Agarwal, U., Atalla, R., and Reiner, R., Proc 1993 Pulping Conf., Atlanta, GA. p. 519.

(1993).

21. Strunk, W., Peroxide Bleaching, Pulp and Paper Manufacture: Mechanical Pulping. p. 425. (1989).

22. Kubelka, P.,J. Opt. Soc. Am. 38. p. 448. (1951).

23. Teder, A., and Tormund, D., AIChE Symp. Ser. 200(76). p. 133. (1980).

25. Ni, Y., Dixon, C., and Ooi, T., Can J. Chem. Eng. 75. p. 48. (Feb, 1997).

26. Detroz, R., Renders, A., and Devenyns, J., Proc 1996 Pulping Conf. Nashville, TN. p. 643. (1996).

h2o2 decomposition

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