Download Hydrogen Peroxide Bleaching: Background, Mill Applications, and Research Directions and more Exercises Art in PDF only on Docsity! Hydrogen Peroxide Bleaching Highlights State of the Art and Research Direction Art J. Ragauskas Hydrogen Peroxide Bleaching • Background • Mill Applications • Research Directions Peroxide Bleaching: Background OCH3 O R O- HOO- OCH3 O- R O- O HO OCH3 O- R O O OCH3 O C O- O R OCH3 O- OH O R -O HO- O2 OCH3 O O O2 - O2 or OHC OH O - OCH3 C OH O OCH3 C OH O OCH3 C OH O OCH3 O O- O OCH3 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 OOH O O R Destruction of color bodies Peroxide Bleaching: Background Peroxide Bleaching: Background O O XylanO HO O HO OH CO2HH H2O2/NaOH Formed during pulping • 30 -50% of Southern HW Kappa # •10 - 20% of Southern SW Kappa # NR 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 metals 2.5% 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 Brightening After OD(EPO)D Kraft HW 84 86 88 90 92 0.0 0.5 1.0 1.5 2.0 2.5 Chemical Charge, % o.d. pulp Br ig ht ne ss Chlorine Dioxide Peroxide Ozone Peroxide Brightening Effects 80 81 82 83 84 85 86 87 88 89 0.5 1 1.5 2 2.5 3.5 Peroxide Charge (%) T ap pi B ri gh tn es s DEDP DEPD • D-stage generates active lignin structures for P-stage Peroxide Activation - Catalyst Peroxide Bleaching: Research P-catalyst N N V O2 - O2 -O2 - N Fe N N N O O O O O HH X X Mn O Mn O N N N N N N O O Peroxide Bleaching: Research P-catalyst Catalytic Peroxide Activation: Use of Mn-catalyst to improve alkaline peroxide bleaching of Do SW kraft. 0 2 4 6 8 10 12 14 16 D o SW kr af t 0. 5% P 0. 02 % Pc at 0. 2% P ca t 1. 0% P 0. 02 % Pc at 0. 2% P ca t K ap pa # Peroxide Fiber Modification 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. Acknowledgments Member Companies IPST
