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Cursos Abertos 2012aproveite esta oportunidadee FAÇA SUA INSCRIÇÃO.CAPACITAÇÃOTÉCNICAMARÇOCurso sobre Segurançanas Paradas de MáquinasData: 14 e 15 de marçoDocente: Paulo R. BezerraCurso básico sobre fabricaçãode celuloseData: 27 e 28 de marçoDocente: Alfredo MokfienskiABRILCurso básico sobrefabricação de papelData: 18 e 19 de abrilDocente: Clóvis PereiraMAIOCurso sobre branqueamentoda celuloseData: 16 e 17 de maioDocente: Carlos Augusto A. SantosCurso sobre reciclagemde aparas para tissue eembalagensData: 30 e 31 de maioDocente: João Alfredo LeonJUNHOCurso sobre Refinação deCeluloseData: 20 e 21 de junhoDocente: Vail ManfrediCurso sobre preparação deMassaData: 27 e 28 de junhoDocente: Clóvis PereiraJULHOCurso básico sobrepolpação (cozimento)kraftData: 18 e 19 de julhoDocente: Alfredo MokfienskiAGOSTOCurso sobre secagemde papelData: 15 e 16 de agostoDocente: Edison CamposCurso sobre reciclagemde aparas para tissue eembalagensData: 29 e 30 de agostoDocente: João Alfredo LeonSETEMBROCurso sobrebranqueamento daceluloseData: 12 e 13 de setembroDocente: Carlos Augusto A. SantosCurso básico sobrefabricação de papelData: 19 e 20 de setembroDocente: Clóvis PereiraVAGASLIMITADASACESSE O SITE E FAÇA SUA INSCRIÇÃO:abtcp.org.brcursos@abtcp.org.brTELEFONE (11) 3874-2736TODOS OS CURSOS SERÃO REALIZADOSNA SEDE DA ABTCP, EM SÃO PAULO,DAS 8h ÀS 17h.ANOS
Technical Article / Peer-reviewed ArticleO PAPEL vol. 73, num. 4, pp. 59 - 64 APR 2012Changes in a eucalyptus kraft pulp during a mild acidtreatment at high temperatureAuthors*: Leonardo Clavijo 1María Noel Cabrera 1Susanna Kuitunen 2Sirje Liukko 2Tiina Rauhala 2Tapani Vuorinen 2Keywords: Acid treatment, eucalyptus kraft pulp, hexenuronicacids, high temperature, ligninABSTRACTModern eucalyptus kraft pulp bleaching includes a hot acid stepfor removal of hexenuronic acid. This step is typically run at pH3.0-3.5 at 90-95ºC with a delay of 2 to 4 hours. In this study thetarget was to find out if similar or better results could be obtainedat higher temperatures with a shorter delay. A commercial oxygendelignified eucalyptus kraft pulp was treated at pH 3.0-3.2 at 80,100, 120 and 140ºC for varying times. The decrease in kappanumber could be modeled with a single component first orderkinetics. The correlation between kappa number and 2-furoic acidcontent of the filtrates was significant (R 2 =0.9969). The differenceUV-visible reflectance absorption spectra (∆(k/s)) were similarshape showing mostly decrease in content of hexenuronic acid.At the harshest condition, the baseline of the difference spectraat >270 nm was shifted upwards indicating partial degradation oflignin. UV Raman measurements showed that the residual aromatic(lignin) content of the pulp was reduced by one third under themost extreme conditions. Quite surprisingly, the selectivity of thetreatment was almost independent of temperature. This studygives additional information for designing mild acid stages foreucalyptus kraft pulp bleaching lines. The treatment could becarried out at a temperature much higher than applied todaywithout any significant loss in the quality of the pulp.INTRODUCTIONSince xylans are the main hemicelluloses group in hardwood,the reactions of uronic acid groups are important especially inhardwood kraft pulping. During the bulk delignification thehexenuronic acid groups (4-deoxyhex-4-enuronic acid groups –HexA) are cleaved off from the xylan chain (Vuorinen et al., 1999).The HexA react with several bleaching chemicals consumingthem and, furthermore, their presence in the final pulpdecreases the brightness stability of the paper products. Alsopermanganate attacks HexA, which therefore contributes tothe kappa number of the pulps.The amount of HexA groups in the pulp depends on the cookingtemperature and time, hydronium ion concentration and ionicstrength. Sixta and Rutkowska (2007) studied the influence ofeffective alkali concentration, sulfidity and ionic strength on theHexA concentration profiles. They proved that the HexA contentcannot be reduced to low levels by choosing appropriated cookingconditions without simultaneously deteriorating pulp qualityand decreasing pulp yield. While recent research aims to reducehexenuronic acid formation genetically modifying the side chains ofxylans (Li et al., 2011), this approach is emerging. Because of that,HexA groups should be removed from the pulp before bleaching.A mild acid hydrolysis of kraft pulp is the most used methodfor removal HexA groups (pH 3.0-3.5 at 90-95ºC with a delay of2-4 hours). In acid hydrolysis the HexA groups are quantitativelyconverted to 2-furoic plus formic acid and 5-carboxy-2-furaldehyde(Vuorinen et al., 1996)(Li and Gellerstedt, 1997)(Pikka et al., 2000).The purpose of this work was to study the effect of highertemperatures and shorter times in the A-stage.MATERIALS AND METHODSThe A-stage was done according HUT procedure at differenttemperatures (80, 100, 120 and 140ºC) and reaction times (between10 and 240 minutes). Industrial oxygen delignified eucalyptus pulpwas used in all cases (kappa number 11.1, brightness 62.9 %ISO,SCAN viscosity 1100 mL/g).In the acid filtrates UV-Visible spectra was studied, whereaskappa number, viscosity, brightness, UV-Visible reflection and UVRaman spectra were measured from the pulp. Dry matter content,kappa number and viscosity were done according SCAN standards,while brightness was determined according to ISO standard.*Authors’ references:1. Facultad de Ingeniería, Universidad de la República, Julio Herrera y Reissig 565, 11300, Montevideo, Uruguay2. Faculty of Chemistry and Material Sciences, Helsinki University of Technology, Otakaari 1, FI-02150, Espoo, FinlandCorresponding author: Leonardo Clavijo – E-mail: lclavijo@fing.edu.uyabril/April 2012 - Revista O Papel59
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