CHEMICAL PULPING AND BLEACHING PROJECT ADVISORY COMMITTEE MEETING

Transcription

1 CHEMICAL PULPING AND BLEACHING PROJECT ADVISORY COMMITTEE MEETING November 4-5, 1998

2 CH EM ICAL PULPING BLEACHING AN id PRO JECT AD VIS ORY COMM ITT EE M EETING November 4-5, 1998 Institute of Paper Science and Technology 'hstreet, N.W. Atlanta, Georgia Phone- (404) FAX - (404)

3

4 TABiL E O F C OiNT ENTS Project F015 Fundamentals of Bleaching Chemistry... 1 Project 4168 Selectivity of Ozone Bleaching... 5 Project Fo17 Closed Mill Operations... 9 Project F013 Environmentally Compatible Production of Bleached Chemical Pulp Project F030 High Strength, High Yield Bleached Pulps Project F014 Fundamentals of Brightness Stability Externally Funded Projects' Project 4181 Trees with Built-in Catalysts Project 4226 Trees with Modified Lignin Listing of Industry/IPST Research Line Road Maps... 33

5

6 DUES-FUNDED PROJECT SUMMARY FY Project Title: Chemical Fundamentals of Bleac_ng Project Number' FO15 PAC: Chemical Pulping and Bleaching Division' ChemicalandBiologicalSciences Project Staft Faculty/Senior Staff: Arthur J. Ragauskas, Lucian A. Lucia Staff: Lenong Allison, Ki-Oh Hwang FY Budget: $270,000 Allocated as Matching Funds: N/A Time Allocation Faculty/Senior Staff: 80% Support: 150% Supporting Research M.Sc.Students J. Wemer Ph.D. Students: and F. Chakar F.S. Chakar, K. Haynes, T. Runge, M. Zawadzki, _SEARCH LINE_OADMAP' Environmental Performance: Reduce emissions of entire pulp and paper manufacturing process to meet Tier 3 Cluster Rule while maintaining global competitiveness. Reduce water usage in bleached kraft pulp production to 2,500 gallons per ton. Improved Forest Productivity: Increase the yield of kraft-p_p equivalent fiber by 10%. PROJECT OB_CTIVE: Provide a fundamemal understanding of the physical and chemical reactions that control lignin and carbohydrate degradation during new bleaching sequences. Understand the reasons for selectivity of reactions that occur in selected pulping and bleaching sequences. The research compliments Project FO13 research on bleach process technology. Focus areas for this fiscal year are hexenuronic acids, biobleaching, high efficiency peroxide bleaching, and oxygen delignification. PROJECT BACKGROUND: Influence of Hexenuronic Acids on Bleaching Confidential Information - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

7 The effects of temperature and acid conditions needed to optimize the removal of hexeneuronic acid (HexA) were determined. Metal binding studies demonstrated that hexenuromc acids are one of the main components involved in binding non-process elements to kraft pulp fibers. The removal of HexA was shown to significantly improve pulp bleachability of hardwood kraft pulps. Polysulfide kraft cooking showed little influence on the formation of hexenuronic acids, whereas AQ kraft cooks appeared to favor their formation. Preliminary investigations suggested that the effective alkali concentration during pulping influences the formation of hexenuronic acids. Biobleaching Studies New mediators were studied for the laccase/mediator delignification system. For a softwood oxygen delignified kraft pulp, the new mediators allowed for >50% delignification with less than 3% of the typical enzyme charge. Preliminary studies have demonstrated that the laccase/mediator systems are effective for the delignification of high-kappa pulps. High Efficiency Peroxide Bleaching Spectroscopic lignin studies of D(EOP) and DE bleached kraft pulps illustrated that condensed phenolic groups are resistant to a Do stage. Residual lignin and peroxide bleaching studies of methylated pulps suggest that alkaline peroxide is more effective at chromophore removal than delignification. Fundamental Role of S'mglet Oxygen in Pulp Bleaching Singlet oxygen is an electrophilic species with a very high oxidation potential in solution. Its role in oxygen delignification schemes has not been adequately investigated nor understood. It was the purpose of the present investigation to provide insight into its bleaching action on pulps. Initial investigations into the role of singlet oxygen revealed that it is a potent delignifying agent that also demonstrates a remarkable capacity to brighten kraft pulps. It can be generated both photochemically and chemically, and is known to react during both oxygen delignification and hydrogen peroxide bleaching. SUMMARY OF RESULTS: Influence of Hexenuronic Acids on Bleaching Research efforts in HexA were focused on exploring the effects of alternative acids at removing HexA and the impact of HexA removal on chlorine dioxide bleachability. The hydrolysis of hexa from an industrial hardwood kraft was examined with five different acids including, formic acid/potassium formate, nitric acid, phosphoric acid, p-toluenesulfonic acid, and the acidic effluent from a Do stage. Each of these reagents were reacted with the same hardwood kraft pulp using an initial ph of 3.0 for reaction times of 1, 2, and 5 h at 80, 90, and 95 C. The decrease in ConfidentialInformation - Not for Public Disclosure (ForIPSTMemberCompany'sInternalUse Only)

8 apparent kappa number varied from 14-38% depending on the reaction conditions and acid used. As an exploratory study, we examined the use of hydrogen peroxide in an acid stage. Under the same conditions that typically reduced the kappa number by _ 15% we could further reduce the apparent kappa number by an additional 40% by reinforcing the acid hydrolysis stage with 2% hydrogen peroxide. The mechanisms contributing to this effect are unknown and require further investigation. The effects of removing HexA on yield were also examined. We continue to observe no measurable differences on yield for the HexA free pulps after an acid treatment or after a Do stage. Current research efforts are directed at examining the effects of HexA removal on ECF bleachability. Employing pre- and post oxygen delignified industrial hardwood kraft pulp, the pre-o2 pulp was bleached with DEDED sequence and the post-o2 pulp was treated with a DED sequence using a 0.20 k.f. The HexA free pulps exhibited improved response to DoE treatment and we anticipate that these results will carry through to the fully bleached pulp also. Biobleaching Studies The biobleaching studies continue to explore the use of violuric acid as a mediator for laccase catalyzed deligification of kraft pulps. The use of the laccase-violuric acid system on a hardwood kraft pulp was shown to yield a 42% reduction in kappa number after an alkaline extraction stage. The yield after the (LMS)E treatment was determined to be 99.6%. The sensitivity of the LMS treatment to NPEs was explored by adding metal sulfates to the pulp. These results suggest that the LMS system is sensitive to Cu 2+,Ni 2+and Fe 2+. Interestingly, the presence of Mn 2+or Mg 2+was shown not to influence the LMS delignification of kraft pulps. High Efficiency Peroxide Bleaching Studies on the bleaching chemistry of hydrogen peroxide in an EOP stage have only been recently initiated and will not be presented at the Fall PAC review. These results will be presented at the spring review. Fundamental Role of Singlet Oxygen in Pulp Bleaching Currently, research efforts in our sub-objective have been directed toward the study of the pulp reactions of a highly reactive and short-lived species of oxygen known as singlet oxygen. Interestingly, very few research efforts have been initiated to determine its role in oxygen delignification. Our work has shown that the photochemical and chemical production of singlet oxygen can induce delignification and concomitant brightening of both pre- and post-o2 kraft softwood pulp. Our beginning work was aimed at determining the influence of both visible and near- UV irradiation on the photochemical production of singlet oxygen through direct lignin carbonyl light Confidential :Information- Not for Public Disclosure (For IPST Member Company's Internal Use Only)

9 absorption resulting in singlet energy transfer to oxygen. We found that Rose Bengal-sensitized delignification technologies were NOT well-studied nor characterized. Very remarkably, we were able to substantially delignify pre-o2 softwood pulps with >95% visible light ( ) and a small amount of RB (0.5% odw). All singlet oxygen nms were done in a quartz round bottom flask containing pulp which was vigorously stirred and cooled by a fan. Lighting was provided by a series of 16 "cool-whit e'' fluorescent lamps (each rated at 8W). The efficiency of delignification for an irradiated softwood kraft pulp containing Rose Bengal is almost 70%. Control experiments successfully showed that isolated conditions of temperature, light, or Rose Bengal do not contribute significantly to de_gnification. The rest of our studies focused on determining the factors influencing the delignification, pulp viscosity, and the final brightness. All results indicated the involvement of singlet oxygen in lignin loss and brightness ga/n, two important data that strongly correlate to the action of singlet oxygen. We also generated singlet oxygen chemically by the oxidation of hydrogen peroxide with hypochlorite and found that the delignification occurred, but to a much lower extent. We attribute the differences in reactivity to "site-directed" attack of singlet oxygen by Rose Bengal vs. the chemical generation method. Rose Bengal adsorbs into the pulp quite well, and may help to direct the reaction of singlet oxygen, whereas chemically formed singlet oxygen is generated at an air-water interface and exists approximately 3-4 microseconds. Unless lignin is close enough to react before the decay of singlet oxygen, very little oxidation chemistry will be observed. DELIVERABLES FOR FY 98-99: 1. Determine the effects of O and P in an (EOP) stage. 2. Evaluate the effects of various acids on the removal of hexenuronic acids from hardwood kraft pulps. 3. Determine the yield after a laccase-mediator delignification treatment and the impact of metals on this biobleaching system. 4. Determine the experimental factors that affect the fundamental role of singlet oxygen in the bleaching of kraft pulps. Confidential Information- Not for Public Disclosure (For IPST Member Company's Internal Use Only)

10 EXTERNAL-FUNDED PROJECT SUMMARY FY Project Title: Improved Selectivity in Ozone Bleaching Project Number' 4168 PAC: ChemicalPulpingand Bleaching Division: Chemicaland Biological Sciences Project Staff Faculty/Senior Staff: Donald Dimmel Staff: Cathy Welder, Elizabeth Althen FY Budget' USDA New Research Initiative Program- $24,000 Time Allocation Faculty/Senio r Staff: 15% Support: 70% Supporting Research Internal: FO15, Chemical Fundamentals 0fBleaching RESEARCH LINE_OAD_P' Environmental Performance' Reduce emissions of entire pulp and paper manufacturing process to meet Tier 3 Cluster Rule while maintaining global competitiveness. Reduce water usage in bleached _aft pulp production to 2500 gallons per ton. PROJECT OBJECTIVE: Pulp quality issues hamper the use of ozone as a pulp-bleaching agent; there appears to be ozone-induced cellulose chain cleavage reactions that effectively reduce the degree of polymerization (DP). Cellulose can potentially be depolymerized when attacked by ozone directly, by radicals derived from ozone decomposition in water, by radicals from ozone-phenol reactions, and/or by radicals from secondary decomposition of ozone-organic intermediates. The goal of this research project is to clarify the relative importance of these reaction pathways and allow the industry to develop strategies to improve ozone selectivity which, in turn, positively impacts pulp strength, yield, and brightness and aids in reducing the level of bleach mill wastes. PRO.CT BACKGROUND' if carbohydrate degradation by ozone is a result of direct attack of ozone on C-H bonds, there is little that can be done about controlling ozone-bleaching selectivity. However, if the selectivity problem is associated with certain types of byproduct radical reactions with carbohydrates, then possible protective measures could be sought. The extent of each of these reactions, direct ozone attack and byproduct radical attack, is a controversial subject. To develop an in-depth understanding of the relative importance of different degradation pathways, we have elected to study ConfidentialInformation - Not for Public Disclosure (ForIPSTMemberCompany'sInternalUseOnly)

11 cellulose model reactions. The much less structurally complex model should be able to provide information on reaction sites, such as the location and frequency of carbonyl groups. However, our initial ozonolysis studies with 1,5-anhydrocellobiitol, a disaccharide cellulose model, have produced very complex product mixtures. Here, where radical reactions should have been minimal, ozone appears to be reacting in a non-selective manner. Glucose and 1,5-anhydrogluciitol, the two monomers composing the disaccharide model, were the major products, but each was found in less than 1-2% yield. This finding caused a significant change in the research direction. A second substrate of high interest to us was amorphous cellulose. Because of its disordered structure, amorphous cellulose should be much more accessible to reagents than highly-structured crystalline cellulose and, thus, exhibit more noticeable DP changes in degradative-type reactions. However, amorphous cellulose, prepared by precipitation of cotton linters from dimethylacetamide solution, proved to be somewhat difficult to work with. In addition, we initially observed few differences in the ozone reactions of amorphous cellulose and fluffed cotton linters. So, we chose to focus On the ozone-induced degradation of the cellulose in fluffed cotton linters. Degradation by direct glycosidic bond cleavage was monitored by determining the drop in the DP of carbamylated, NaBH4-reduced samples with gel permeation chromatography (GPC). The NaBH4 reduction step is intended to reduce carbonyl groups that may have been introduced by reaction of 03 with the carbohydrate. Carbonyl groups activate carbohydrate chain cleavage reactions in the presence of base, such as NaOH or pyridine. Pyridine is present in the carbamylation step. The amount of change in DP between NaBH4 reduced and non-reduced samples has been used as an estimate of the extent of carbonyl introduction into carbohydrates. We observed very little direct cellulose chain cleavage with ozone doses <10%. Low consistency ozonations of fluffed cotton linters caused less DP drop than high consistency ozonations. In the absence of lignin, it appears as if direct cellulose chain cleavage by ozone is minimal. RECENT RESULTS. Experiments of the last six months have focused on: completing a set of ozone reactions involving time and dose differences for fluffed cotton linters, with/without lignin present and with/without NaBH4 reduction in the workup, further evaluating differences between ozone reactions of fluffed cotton linters and amorphous cellulose, with/without lignin and with/without NaBH4 reduction, examining the ozone reactions of a fully acetylated 1,5-anhydrocellobiitol in organic solvents to gain possible insight into the reactivity of this type to disaccharide towards ozone, and comparing ozone reactions to that of Fenton's reagent (hydroxyl radical generator) with fluffed cotton linters. A statistical analysis of the molecular weights obtained from ozone reactions with fluffed cotton linters revealed that' Ozone dose, but not consistency or ozone addition time, had an effect on the DP. Quenching ozone-treated linters with sodium dithionite at different time intervals had no affect on the molecular weight. These results imply that secondary, slow developing radical reactions, such ConfidentialInformation - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

12 as the breakdown of organic peroxides and trioxides, are not significant. The typical 1% dose used for pulp bleaching had no effect on the linters' molecular weight. * Spiking the linters with 1.7% lignin had a DP protecting effect. Here again, ozone dose, but not addition time (60 to 300 s), was found to have an effect on molecular weight. In carefully conducted experiments, amorphous cellulose at 1% consistency shows twice the drop in DP at an applied ozone dose of 12.7% than does fluffed cotton linters. From this limited amount of data, it appears that ozone-amorphous cellulose reactions should be pursued. Except in one case, there was little difference in observed molecular weights with and without NaBH4 reduction atier the ozone treatment. Such an observation is consistent with the lack of carbonyl introduction by ozone. The exception was one of three reactions that was conducted with Fenton's reagent; here we observed a large drop in DP if a NaBH4 reduction was omitted. It is unclear why the Fenton's reagent is not providing a consistent result. In addition, fully acetylated 1,5-anhYdrocellobiitol was less reactive towards ozone in an organic solvent than 1,5-anhydrocellobiitol was in water; however, it also gave a complex product mixture, supporting our earlier observation of unselective ozone-carbohydrate reactions. GOALS FOR FY 98-99: Our goals for the remaining months of this project and longer term are: to evaluate the differences between ozone and Fenton's reagent reactions of pulp, fluffed cotton linters containing absorbed lignin and amorphous cellulose that has been precipitated in the presence of lignin, to evaluate the differences in the rates of reaction between ozone and Fenton's reagent reactions with 1,5-anhydrocellobiitol, to prepare (if possible) a lignin-carbohydrate-complex (LCC) of amorphous cellulose and a lignin dimer, and study the ozone-degradation of the LCC under different conditions, to perform select ozone reactions at different ph, temperature, and additive levels, and to summarize the 2-year study in a final report to IPST member companies and to the USDA. ConfidentialInformation - Not for Public Disclosure (For IPST Member Company's Imernal Use Only)

13

14 DUES-FUNDED PROJECT SUMMARY FY Title' Project: PAC: Division: Project Staff Faculty: Staff Closed Mill- NPE modeling F017 Chemical Pulping and Bleaching Chemical and Biological Sciences Division Alan Rudie Narendra Patel FY Budget $135,000 Time Allocation Faculty: 50% Staff: 60% Related Projects' Ph.D. Research M.S. Research Giselle Ow Yang Ana Puckett Georgia TIP 3 MP4 A. Rudie $55,000 to fund X-ray spectroscopy effort Georgia TIP 3 MP1 C. Woitkovich, $149,557 Machine water reuse DOE- Agenda 2020 J. Frederick (OSU) NPE modeling Research Line 4: Reduce water usage in bleached kraft pulp production to 2,500 gallons per ton. Project Objective: Develop technology useful in moving towards low effluent operation. Project Task: Characterize metal binding with wood pulps and develop methods to solve the equilibrium metals partitioning and speciation in the pulp mill and bleach plant. FY 98/99 Goals Complete the high temperature evaluation of selectivity coefficients for Na, Mg, Ca, Ba and Mn. Project Background: Metals management in the paper industry has been around for a long time, principally related to control of transition metals in peroxide bleaching of high-yield pulps. The recent interest in alternative bleaching chemicals and in eliminating the bleach plant wastewater stream has added a new dimension to the metals management problem. The problem with metals buildup and inorganic scale formation in low effluent and closed mills has created a need for a much better understanding of metal binding in wood pulp. Confidential Information - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

15 10 Summary of Results: Progress has been quite good in collecting multiple temperature data for selectivity coefficients. The Gibbs Energy relationship RTln(K) = AG = AH- TAS is working quite well, giving useful straight-line relationships. This effort is going on simultaneously in the Georgia TIP project on linerboard grade pulps (Project 4153), and FO17 on bleachable grades. The decision was made to repeat the room temperature experiments when collecting the 45 and 65 data to make sure the Gibbs Free Energy was calculated on a consistent data set _ )29 O.C:)34 At this point, two bleachable grade -0A pulps and three linerboard grade pulps _' have been evaluated. Most selectivity 5' -0._' 'E coefficient data is suitable for all grades. -_ The exception appears to be the acid -_.2 y =-3272XR2: competition experiments where -_.4 significant variations have been l/t, Deg-I observed. This variation is observed as Figure 1. Gibbsfree energyplot for a change in slope for the transition from Magnesium competition with Sodium, the acid state to a metal adsorbed state, Softwoodlinerboardpulp (GA TIPs MP1). andwascommunicatedto thepaclast march as a difference observed between hardwoods and softwoods. There is now additional evidence that this value is more variable than initially thought and may need better characterization. A fully bleached pulp sample has been obtained and experiments will start with it when the current activities are concluded. Efforts at incorporating the existing data into the OLI database are proceeding under the DOE - Agenda 2020 project. This effort has been supplied with a very limited set of data generated under the Georgia TIP 3 project. The primary purpose of this is to evaluate the data analysis procedures and confirm the suitability of the methods for this application. A detailed review of the matrix of Selectivity Coefficients provided in March shows several inconsistencies K Mn in the data set. For example, KC_ = 0.9 and KCj = 1. We expect N 1 but find instead that the initial estimate was 0.5. Considerable effort is going to be required to reconcile some of these errors and this task has been put off until the data set and numerical methods are completed. Considerable time has been spent on developing EXCEL macros that can calculate the bound metal content for the two metal competition experiments. The latest versions of these macros contain the Debye Huckel activities. It remains yet to include the bound water calculation and these will be finished. Unfortunately, the macros still fail to converge in some instances and a calculation error was recently discovered in one of the three cases. There is little value in reworking the existing data until the macro revisions are completed. The data collection and macro correction effort should be finished by Confidential Information - Not for Public Disclosure (For IPST Member Company's IntemaI Use Only)

16 11 January and corrected and reconciled tables will be available for the March annual review meeting. Ph.D. Research of Giselle Ow Yang, and Georgia TIP 3 MP4 This project has recently completed the initial EXAFS data collection for Calcium and Manganese in unbleached pulp. The Calcium EXAFS radial distribution function indicates features at about and 3.4 A with smaller features at 4.3, 5 and 5.8 A. Remember, there is an unpredictable phase shift of ,, and the typical Ca- _n O bond distancesof 2.1 to 2.3 A are _2 within this range. Efforts to simulate the '_ o.8 calcium sites with FEFF7 have ruled out Calcium Carbonate (aragonite) as the '_ 06 source of the EXAFS spectrum. EXAFS Y_o2 n simulations of calcium sugarcomplexes o havegreatersimilarityto the EXAFSof o Radial 2Distribution, Angstroms 4 6 calcium in pulp and this is the current focus of the project. Figure 2. Calcium inpulp: EXAFSradial distribution function. (Ph.D. project, GOY and GA TIP 3MP4) Efforts to prepare a complex that mimics the iron site continue. Most of the isolated materials have been obtained as oils and changes in the structure para to the phenolic oxygen have failed to increase stability or fllow crystals to be collected. In traditional chemical synthesis, one generally isolates and purifies a compound before expending much time in characterizing it. Having failed thus far with this approach, we are making a larger effort to characterize the crude products of these reactions in an effort to determine what is preventing the isolation of a useful complex. Goals For Remainder: FY98-99 F Complete selectivity coefficient and Gibbs Free Energy analysis for bleachable and fully bleached pulps. 2. Complete an analysis of differences in pulp metal adsorption and acid removal. 3. Develop methods to determine the metal adsorption at high ph and begin characterizing the contribution of lignin phenols to metal adsorption. Student Research and GA TIP 3 MP4 1. Prepare chemical models of the iron, calcium and manganese binding sites: G.O. Yang. 2. Carry out a laboratory bleach filtrate recirculation experiment to generate a data set suitable for testing the adsorption models: A.Puckett. Confidential Information - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

17 12 GA TIP 3 1. Complete any remaining selectivity coefficient work on linerboard grade pulps 2. Incorporate selectivity coefficient data into OLI and complete a simple OLI mass balance model of a linerboard papermachine. ConfidentialInformation - Not for Public Disclosure (ForIPSTMemberCompany'sIntemalUseOnly)

18 13 PRO.CT SUMMAR Y Period: April1-September30, 1998 Project Title: Environmentally Compatible Production of Bleached Chemical Pulp Project Code: BLECH Project Number: FO13 PAC: ChemicalPulpingandBleaching Division: Chemicaland BiologicalSciences Project Staff: Faculty/Senior Staff T.J. McDonough, C.E. Courchene, A. Ragauskas Staff.' M. Alger,J.-C. Barom_s,B. Carter,N. Rawat, A. Shaket, M. Turner FY 98-99Budget: $245,721 Allocated as Matching Funds' Project 4201' $15,000 Project 4159' Project 4120' $36,000 Supporting Research: M.S. Students: PhD. Students' External: Carter Johnson Aric Bacon Project 4201, "Bleach Plant Capital Reduction with Rapid Do and Simplified Bleaching" (U.S.D.O.E. Agenda 2020 Capital Effectiveness) RESEARCH LINE/ROADMAP: Environmental Perfomance/RM5 - Reduce Emissions PROJECT OBJECTIVE: Project 4159, "High Efficiency C102 Delignification" (U.S.D.O.E Agenda 2020 Environmental) Project 4120 "Energy Efficient Kraft Pulping for Highly Bleachable, Low Lignin Content Pulp" (U.S. D.O.E. Paper Mill of the Future) Define pulping and bleaching technology that will decrease or eliminate the release of byproduct organic chlorine compounds without sacrificing bleached pulp quality. PROJECT BACKGROUND: Prior work on this has included investigations in the area of environmentally compatible manufacture of bleached chemical pulp. These have included studies of peroxide delignification of kraft pulps, ECF bleaching process behavior, effects of kraft, oxygen ConfidentialInformation - Not for PublicDisclosure (For IPST Member Company's Internal Use Only)

19 14 and C102 delignification on pulp physical properties, and Rapid Do mill trials and laboratory studies. Additional objectives of this project have been leveraged through the contribution of matching efforts in support of related externally funded projects. These have included work on environmental aspects of ECF bleaching, bleachability as related to pulping conditions, improving the efficiency of C102 delignification, and development of low-capital bleaching processes based on Rapid Do and simplified bleaching. Recent investigations within these projects have included vapor phase C102 delignification, effects of cooking liquor concentration profiling on bleachability, effects of pulping conditions on hardwood bleachability, and effects of bleach plant washer inefficiency on effluent characteristics. Experiments were conducted in which kraft pulping conditions were systematically varied over wide ranges and the resulting pulps were delignified with peroxide after chelation. The results showed that modem chelation-peroxide technology is capable of extensively delignifying southern pine kraft regardless of pulping conditions. In a comparison of effects of carryover and D1 stage ph in ECF and (DC)-based bleaching, we showed that, at low KF, carryover has about the same effect on Do and (DC) bleaching. However, at high KF, carryover has significantly less effect on Do than on (DC). Final brightness is higher for Do than for (DC) when carryover is high, and the optimum D1 exit ph is higher at low KF than at high KF, and higher in the presence of carryover than in its absence. A subproject was initiated to characterize the effects of delignification and bleaching processes on fiber properties. The initial work was defined to include conventional kraft batch pulping, oxygen delignification, and both CED and DED bleaching. From a mill trial of the Rapid Do concept, it was concluded that the industrial scale mixers, both static and dynamic, can give sufficiently good mixing to make Rapid Do bleaching industrially feasible. Work on a several externally funded projects moved us toward goals that were closely aligned with the goals of Project FO13. Laboratory studies showed that Rapid Do bleaching is applicable to conventional and Lo-Solids pulps and to pulps prepared at unusually low kappa number levels. Laboratory vapor phase C102 delignification experiments showed that, in bleaching hardwood pulps, vapor phase delignification is remarkably more efficient, but generated markedly larger quantities ofaox than the conventional process. In an effort to assign a cause for the superior bleachability of pulps made by modified pulping processes, we conducted systematic bleaching studies of southern pine pulps prepared with controlled liquor concentration profiles. We conducted a systematic study of AOX, BOD, and COD released by bleaching southern pine kraft pulp in the D0(EPO)D1 sequence at a kappa factor of 0.20 and a D1 stage C102 charge of 1.2%. Hardwood bleachability studies indicated that EA and pulping temperature affect the nature and bleachability of the pulp produced' High EA and high temperature pulping emerged as a very attractive option for maple. ConfidentialInformation - Not for PublicDisclosure (For IPST Member Company's Internal Use Only)

20 15 SUMMARY OF _CENT RESULTS' Effects of Delignification and Bleaching on Fiber Properties The joint project between the Chemical and Biological Sciences (CBS) and Fiber and Paper Physics (FFP) Divisions to characterize the effects of delignification and bleaching processes on fiber properties has provided fiber property results on a set of the unbleached pulp samples following kraft and oxygen delignification. Analysis of the remaining samples bleached with both CED and DED sequences will be completed this fiscal year. Prior to testing, all samples have been subjected to an ion-exchange procedure which includes an acid wash to strip metal ions followed by replacement with Ca +2at the active ion-exchange sites on the fiber. The success of this ion-exchange is being followed by a subsequent metal ion analysis of the pulps. Refining of the pulp samples is being done with a PFI mill. All samples are being compared in both the unbeaten state and after 3,000 revolutions. The p_ps are tested for CSF, % fines (Britt Jar procedure), and water retention value (WRV). Standard handsheets of both the unrefined and refined samples are being tested for porosity, scattering coefficient, tear, tensile, and both in-plane and out-of-plane elastic properties. Zero span tensile analysis is being done on dry handsheets as well as neverdried and rewetted sheets. The development of structural features in the fibers are being measured both qualitatively and quantitatively by iron and palladium colloid staining techniques that highlight both cell wall and fibrillation changes following mechanical treatment. Peroxide Delignification The use of modern chelation-peroxide practices for delignification of kraft pulp was investigated further with a series of QP experiments on a kraft pulp (kappa no. 24) from a southeastern mill. Following the Q stage with 0.5% EDTA, a series of atmospheric peroxide stages were done in duplicate with 1, 2, or 3% H202. The extent of delignification as measured by the kappa no. reduction, was 35, 48, or 54% at each of the peroxide levels of 1, 2, or 3% respectively. There was only a slight drop in viscosity at 1% peroxide with a 13% decrease at 2% and 19% decrease at 3%. The unbleached and bleached pulps were also characterized by metal ion content analysis. The degree of delignification on this mill pulp was less than the 60-70% achieved from peroxide delignification in the study with lab pulps reported previously. To determine if lab pulps delignify more readily, a kraft pulp at a kappa no. of 28.6 prepared in the lab from southern pine chips was chelated and treated with 3% peroxide at the same conditions as the mill pulp. In this case, the degree of delignification was 59%. Additional work is being done to examine the effect of manganese-catalyzed peroxide delignification. ConfidentialInformation- Not for PublicDisclosure (For IPST Member Company's Internal Use Only)

21 16 AOX Reduction from Combined Bleach Filtrates The effect of mixing filtrates from acid and alkaline bleach stages on potential AOX and COD reduction was measured with a series of three-stage bleaches (DED) on a southernpine kraft pulp (kappa no. 26). Duplicate bleaches were done at each of two kappa factors, 0.1 and 0.2. The individual stage filtrates were analyzed for COD and AOX. From each bleach sequence, a combined filtrate sample was prepared then adjusted to either ph 7 or 11 and held at 60 C for 6 hours. The AOX and COD of these combined and treated filtrates were also measured. There was only a slight reduction in the COD of the combined filtrates at ph 7 Or 11 compared to the sum of the individual filtrates. The combined filtrates had a reduction in the AOX of 20-30% when treated at a ph of 7 and a 30-70% reduction at a ph of 11. This degree of reduction is similar to other reported studies. (D/Z) and (Z/D) Bleaching Experiments were done to assess the effects of the level of substitution of 03 for C102 and mixing speed on the (D/Z)(EPO) partial sequence as applied to a southern U.S. hardwood kraft pulp. This partial sequence was very effective and selective at substitution levels of both 25% and 75%. Mixer speed was shown to be a critically important variable, in terms of both kappa number reduction and brightness development. GOALS FOR FY 98-99: 1. Complete a study of effects of delignification with kraft pulping liquor, oxygen, chlorine and chlorine dioxide on pulp refining behavior and fiber properties and initiate a followup study. 2. Complete a study of predictors of ease of delignification by (1) an oxygen stage and (2) a D(EO) sequence at several extents of delignification. Use a set of softwood and hardwood pulps representing a wide range of bleachabilities to evaluate a defined set of candidate predictors. 3. Evaluate and develop modem chelation-peroxide technology as a substitute for oxygen delignification. 4. Assist one or more mills in implementation of the Rapid Do concept. 5. Report laboratory work to date on ozone bleaching kinetics. 6. Complete a statistically designed comparison of the (D/Z)(EO)D, (Z/D)(EO)D, O(D/Z)(EO)D, O(Z/D)(EO)D, D(EO)D, and OD(EO)D sequences, to enable operating conditions to be optimized and to define the relative advantages and disadvantages of the respective sequences. ConfidentialInformation - Not for PublicDisclosure (For IPST Member Company's Intemat Use Only)

22 17 DELIVERABLES FOR FY 98-99: 1. Report of study of effects of delignification with kraft pulping liquor, oxygen, chlorine and chlorine dioxide on pulp refining behavior and fiber properties. Plan for follow-up study and achievement of significant progress on the follow-up study. 2. Evaluation of a defined set of candidate predictors of ease of delignification by (1) an oxygen stage and (2) a D(EO) sequence at several extents of delignification. 3. Brownstock chelation-peroxide technology for use as an alternative to oxygen delignification. 4. Assistance with demonstration of Rapid Do implementation. 5. Report on ozone bleaching kinetics 6. Optimum operating conditions and relative advantages and disadvantages of the (D/Z)(EO)D, (Z/D)(EO)D, O(D/Z)(EO)D, O(Z/D)(EO)D, D(EO)D, and OD(EO)D sequences. ConfidentialInformation - Not for Public Disclosure (For IPST Member Company's tntemal Use Only)

23 18

24 19 PROJECT SUMMARY Period: April 1 - September 30, 1998 Project Title: High Strength, High Yield Bleached Pulps Project Number: F030 PAC: Chemical Pulping and Bleaching Division: Chemical and Biological Science Project Staff Faculty/Senior Staff: J. Li, E. Malcolm, C. Courchene D. Dimmel Staff: Tech. III FY Budget: $180,000 Allocated as Matching Funds: $ 0 RESEARCH LINE/ROADMAP' Increase Yield by 10% Absolute / Develop Modified Pulping Process. PROJECT OBJECTIVE: The objective of this project is to significantly improve the strength properties of higher yield chemical pulps to the level of current, Iow yield, kraft pulp. Initial work will center on the suitable processes, which do not require significant capital investment. SUMMARY OF RESULTS: A Review on Yield -Strength Relationship Yield increase by 10% can be very significant to the economics of a kraft mill. For example, kraft pulp production can be increased by 50% (!) with the same recovery furnace capacity if the rest processes of the mill are not limiting the production increase. Such magnitude yield increase, mostly from hemice!lulose, will greatly affect softwood pulp physical properties. 1. Change in pulp yield hardly affects fiber length. Material removal during pulping only leads to the reduction in the transverse dimensions, i.e., cell wall thickness and fiber width (or diameter), which are summed into a reduction in fiber coarseness. ConfidentialInformation- Notfor PublicDisclosure (ForIPSTMemberCompany'sInternalUseOnly)

25 20 2. Higher hemicellulose content will provide over all higher bonding potential from increasing number of hydroxyl bonds per unit of contact area and higher plasticity (higher swelling) for better conformability. However, higher coarseness, i.e % at 10% yield increase, may reduce the potential of fiber collapse or conformability. 3. For over all bonding strength, mannan has been reported as being more effective than xylan. Most of the yield increase from softwood pulp is due to higher glucomannan retention. 4. As chemical pulp yield increases from the present 40s% to 50s%, the weightnormalized fiber strength, as measured by zero-span tensile, is likely to decrease since the fiber strength is proportional to a-cetilulose content of the fiber. This disadvantage is unlikely solvable. High viscosity may reduce its impact, especially when oxygen delignification is used. 5. Tearing strength of the higher yield chemical pulp will be lower than that of Iow yield kraft pulp because both higher bonding potential and lower fiber strength will reduce the tearing strength of the pulp. This problem could be reduced by alkaline extraction of short chain hemicellulose. 6. Tensile strength may increase somewhat or at least not decrease because higher bonding potential should be able to compensate the loss in fiber strength. 7. Optical property and flexibility of paper products may be affected. However, these may be corrected by hardwood furnishes and papermaking additives. Non-uniformity of Carbohydrate Degradation during Kraft Pulping- Measurement and Modeling Using A Modified "G" Factor Nonuniform carbohydrate degradation during pulping can be very detrimental to pulp strength and yield. Especially, it will reduce the chances of correcting the lower fiber strength from higher pulp yield or higher hemice!lulose content in pulp. It is well known that carbohydrate degradation kinetics during kraft pulping is mainly influenced by temperature and hydroxide ion concentration. The classical "G" factor method developed by Kubes et. al., however, can not be used directly to predict the effect of nonuniform [OH-] inside wood chips on pulp viscosity uniformity. A modified "G" factor method is developed in this work, which incorporates both temperature and [OH-] history during the cooking, and can be used to predict pulp viscosity profile over the chip thickness. This new method requires the [OH-] variation history throughout the wood chips during entire cooking, which can only be obtained by solving the mathematical model for kraft delignification. The model consists of a set of mass transfer equations with kinetic reaction terms, and is solved numerically by a computer Confidential Information - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

26 21 program, which generates the values of the modified "G" factor. These "G" factor values are then converted to pulp viscosity as a function of positions within the chips. The predicted viscosity profiles were validated by the experimental values. Hand-cut Southern pine chips with given thicknesses were cooked under conventional kraft conditions, and were then sectioned with a proper technique. The measured and predicted viscosity profiles agreed well, and both indicated that carbohydrate degradation of thick chips was very nonuniform. Application of this modified "G" factor method will provide more insights about the uniformity of carbohydrate degradation within wood chips dur..ingkraft cooking. GOALS FOR REMAINING FY 98-99: 1. Continue to write the report on yield - strength relationship' the report will be completed by next spring. 2. Continue the work on digester modification' the parts and equipment needed for the modification are received. The engineering design and control software are being made year research plan' This research plan for the next 3 years shall be presented in the next spring PAC meeting. 4. Start the experiments on modification of one-liquor (no split sulfidity) cooking in the beginning of next year: the goal of this research is to develop modified cooking conditions that do not require any significant amount of capital investment when applied in current mill equipment. Cooking procedures will be modified to maximize the effect of polysulfide and catalyst on both strength and yield. 5. Start to develop suitable process conditions for Soda-Catalyst pulping to achieve high yield and strength' This part of research will use alkali concentration to alter carbohydrate degradation and extraction rate. Confidential Information - Not for Public Disclosure ('For IPST Member Company's Internal Use Only)

27 22

28 23 DUES-FUNDED PROJECT SUMMARY FY Project Title: Fundamemals of Brightness Stability Project Number: FO14 PAC: ChemicalPulpingandBleaching Division' ChemicalandBiologicalSciences Project Staff Faculty/Senior Staff Arthur J. Ragauskas Staff.' Lenong Allison FY 97-98Budget: $63,000 Allocated as Matching Funds: N/A Time Allocation Faculty/Senior Staff 15% Support: 50% Supporting Research Ph.D. Students: RESEARCH LINE/ROADMAP' Improved Forest Productivity' Increase the yield of kraft-pulp equivalent fiber by 10%. Use of post treatments to give kraft properties. Modificationof structureor compositionofproducts. PROJECT OBJECTIVE' Provide a fundamemal understanding of the chemical reactions that are initiated when high-yield pulps are photolyzed. As our knowledge of the photoxidation of mechanical pulp increases, methods to eliminate or significantly retard the photoyellowing of high-yield pulps will be pursued. PROJECT BACKGROUND: Past research activities in FO14 have been directed at four sub-projects: 1. Reversion studies examined the photostability of kraft- BCTMP handsheets treated with fluorescent whitening agents (FWAs), TiO2, CaCO3, and starch. The results of these studies detected a decreased performance of FWA to retard photoyellowing in the presence of other papermaking additives. Interestingly, both CaCO3 and TiO 2 were found to retard the rates of photoyellowing. ConfidentialInformation - Not for Public Disclosure (ForIPSTMemberCompany'sInternalUseOnIy)

29 24 2. BCTMP/kraft testsheets were prepared with FWA, polymer additives, and antioxidants under simulated size press conditions and the photoreversion properties were determined. It was demonstrated that the additives could retard photoyellowing but nonetheless we could not achieve a photostable sheet in this type of approach. 3. The photoaging of acetylated BCTMP handsheets was found to be dependent on the light source. Use of office lighting with acetylated BCTMP handsheets resulted in significant photobleaching of the treated sheets. These results suggest new research oppommities that could be exploited to halt brightness reversion. 4. The use of polycarboxylic acids to crosslink BCTMP fibers was explored. Although it was anticipated that this technology could 'nuprove strength and reversion properties of mechanical pulps, experimental results failed to detect improvements in the photostability of crossl'mked BCTMP fibers. DELIVERABLES FOR FY 98-99: 1. Evaluate the photostabilization effects of CaCO3 and TiO2 on brightness reversion of handsheets composed of 75% SW kraft and 25% HW BCTMP. 2. Examine the potential role of cellulose acetate and other additives at retarding brightness reversion. 3. Examine the use of laccase to graft photostabilization additives onto BCTMP. 4. Study the chemistry involved in the photostabilization of mechanical pulps via acetylation. ConfidentialInformation - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

30 25 EXTERNAL-FUNDED PROJECT SUMMARY FY Project Title: TREES CONTAINING BUILT-IN PULPING CATALYST Project Number: 4181 PAC' ChemicalPulpingand Bleaching Division: Chemical and Biological Sciences Project Staff Faculty/Senior Staff: Donald Dimmel, Jerry Pullman, Gary Peter, John Cairney Staff.' ElizabethAlthen,Huabin Meng FY Budget: DOE funds of $240,000 Time Allocation Faculty/Senior staff 40% Support: 200% Supporting Research M.S. Student: Karen Crews RESEARCH LINE_OAD_P: Environmental Performance: Develop economically viable pulping technology to produce kra_ equivalent pulp which ensures no odor at mill boundaries. Reduce emissions of emire pulp and paper manufacturing process to meet Tier 3 Cluster Rule while maintaining global competitiveness. PROJECT OBJECTIVE: The aim of this project is to define the parameters needed to produce trees that contain >0.05% by weight anthraquinone (AQ)-type pulping catalysts. We will (1) examine what type of trees already contain AQ components, (2) establish whether or not AQ components from one tree will catalyze the pulping of other trees, (3) attempt to find the biological pathways responsible for AQ production in trees, and (4) try to turn on such pathways in genetically modify trees. PROJECT BACKGROUND: Trees that contain AQ, or simple substituted AQ structures, will likely be superior trees as a raw material for producing pulp. Environmental impacts of chemical pulping and bleaching of wood will be minimized by developing forests of healthy trees that contain their own built-in pulping catalysts. These trees will be easily pulped and may require no sulfur delignification agents. The cost of pulping will decrease, along with a substantial reduction in odor emissions. Anthraquinone (AQ) can be used at <0.1% levels to improve pulping efficiency by increasing delignification rates and increasing yields (1). Anthraquinones are natural products that are Confidential Information - Not for Public Disclosure (For IPST Member Company's Internal Use Only)

31 26 present in many plants, including some tree species (2). Previously, we found AQs in the wood of teak and showed that teak extracts containing AQs catalyze the delignification of pine (3). A key step in increasing AQ levels in trees through genetic engineering is to isolate the gene(s) that are rate limiting for anthraquinone biosynthesis. A good starting point appears to be isochorismate synthase, which converts chorismic acid to isochorismic acid and catalyzes the first committed step in the biosynthesis of anthraquinones (4-6). In higher plants, chorismic acid plays a central role for the synthesis of a number of aromatic compounds, including lignin precursors (7). We propose to isolate the gene for isochorismate synthase and increase its expression in trees to enhance anthraquinone production. A higher level of isochorismate synthase will increase its competition for chorismic acid and, therefore, increase the flux of chorismic acid into anthraquinone biosynthesis while at the same time decreasing the flux of chorismic acid into lignin precursor biosynthesis...., ' SUMMARY OF RESULTS' Wood samples from teak, red oak (2 sources), red maple, elm, chestnut, walnut, hickory, blackjack oak, eastern cottonwood, and aspen were extracted and analyzed by GC/MS. Six of the ten commercial hardwood trees were shown to contain significant levels of anthraquinone or anthraquinone derivatives. The existence of AQs in select trees indicates that such trees have the biosynthetic enzymes for AQ production. The survey also showed that levels of naturally occurring AQs varied in normal, healthy trees from to 0.33 percentage on wood weight basis. Eastern cottonwood is especially valuable pulp raw material and contained a three AQs (AQ, methyl-aq, dimethyl-aq) useful for wood pulping. This might explain why eastern cottonwood are easy to pulp. In addition, cottonwood has the distinct advantage that it is easily manipulated in tissue culture for gen e transfer experiments and it is of commercial interest due to its rapid growth rates in plantation settings. Cottonwood will therefore serve as a good model system for transgenic studies to increase anthraquinone levels. When a relatively small amount of teak chips (-0.7% AQ content) were added to the pine chips, a greater amount of delignification of pine was achieved. This suggests endogenous AQs in wood can be released from wood chips during pulping and can catalyze delignification reactions. When AQs are removed, via extraction, both Elm and Red Oak woods do not delignify as much under identical pulping conditions as unextracted wood. On the genetic engineering front, we have been focusing on isochorismate synthase because it catalyzes the first committed step in the biosynthesis of anthraquinones in plants. Isochorismate synthase has been well studied and cloned from many prokaryotic organisms. The study of this enzyme in plants lags behind prokaryotic organisms. A partial sequence of about 400 base pairs from an Arabidopsis thaliana EST (GenBank T42189) was found to be similar to the C-terminal region of bacterial isochorismate synthase. From this sequence information, we designed nested PCR primers and successfully isolated a full-length isochorismate synthase cdna from an Arabidopsis cdna library. This cdna is-_2000 base pairs long and encodes a protein of 503 amino acids with a predicted molecular weight of 55,368 Daltons. It represents the first full-length isochorismate synthase cdna isolated from an eukaryotic system. ConfidentialInformation - Not for Public Disclosure (ForIPSTMemberCompany'sInternalUseOnly)