The effect of hot acid hydrolysis (A-stage) pretreatment on the ozone (Z/E) performance at medium consistency was evaluated. An experimental plan was set up involving full optimization of A and Z/E stages for an oxygen delignified eucalypt kraft pulp. A-stage caused significant kappa and HexA drop, and the optimum condition for this stage being pH 3.0, 90 ºC, 120 minutes at 10% consistency. For A-stage pretreated pulp, the conditions for maximum Z/E-stage efficiency and selectivity were pH 2.5, 40 ºC, 5.0 kg O3 adt-1 pulp for the (Z/)-treatment and pH 10.5 for the alkaline extraction (E). The values of kappa drop per kilogram of ozone applied were 1.04 and 1.18 for A-stage pretreated and reference pulps, respectively. Since the A-stage pretreatment did not decrease the (Z/E)-stage efficiency to a large extent, such stages are complementary rather than competitive. The potential of the A-stage pretreatment to save bleaching chemicals is quite large given that pulp kappa number (brightness) after Z/E and AZ/E treatments were 5.5 (brightness 67.3% ISO) and 1.1 (brightness 72.6% ISO), respectively. The impact of the A-stage pretreatment on overall bleaching performance, comparing the sequences Z/EDP and AZ/EDP will be a matter of other publication on the subject.

Bleached eucalypt kraft pulps are widely used in print and writing (P&W) and tissue paper manufacture. Among the quality requirements of pulp for these papers, xylan content has been controversial. The objective of this study was to evaluate the influence of xylan content on bleachability, hygroscopic, physic-mechanical and optical properties of the pulp. In this study industrial unbleached eucalyptus kraft pulp (15.6% xylans) treated with different NaOH loads to change its xylan content was used. Subsequently, pulps were bleached by the ODHT(EP)D sequence to achieve 90% ISO of brightness, then refined and submitted to hygroscopic, physicomechanical and optical tests. NaOH treatments decreased the xylan content to 14.5-5.9% using NaOH loads of 10-70 g L-1. Pulp bleachability was not significantly affected by xylan content decrease. The decrease in xylan content negatively affected the water retention value and Klemm capillarity of the pulp, while water absorption capacity was positively affected. Tensile and tear index were negatively influenced by the reduction in xylan content, whereas bulk and light scattering coefficient increased.

The sugarcane industry has huge potential for biorefinery concept application, given its development in recent years. In this context, cane sugar straw has become an attractive raw material for biofuel production. This study aims to investigate the chemical composition of cane sugar straw from different regions of Brazil, and to optimize a hydrothermal pretreatment stage for cellulosic ethanol production. Results of chemical characterization of the cane sugar straw for the regions assessed indicated little influence of place on straw chemical composition. Hydrothermal pretreatment showed high efficiency in hemicellulose removal. Hydrothermal pretreatments operating with temperatures of 190 and 210 ºC presented satisfactory results, reaching values close to 100% hydrolysis.

It is well known that pH is an important parameter for controlling the eucalyptus pulp bleaching when using the final chlorine dioxide stage, since it affects the effectiveness of the process. Recommendations found in the literature for operating are in the 3.5 to 4.0 range. However, in this paper it was shown that final chlorine dioxide has better performance, with significant brightness gain while also preserving pulp quality, when it is operated at near neutral pH. This result can be explained by the generation of sodium bicarbonate in situ upon adding carbon dioxide at this stage.

Sugarcane straw biomass accounts for 1/3 of the energy potential of sugarcane and represents a rich source of sugars. Studies have been intensified for the use of this biomass along with bagasse for the production of cellulosic ethanol. Development of this technological path will allow for taking full advantage of sugarcane, increasing ethanol production without expanding the area cultivated. However, in order for this technology to be viable certain challenges must be overcome, including establishment of appropriate conditions of pretreatment and hydrolysis of these materials for release of fermentable sugars.

Pulp hemicelluloses can be extracted with NaOH and quantified by colorimetric and gravimetric techniques. However the most usual methods to measure eucalyptus pulp hemicelluloses have been through the pentosan method or through xylan analyses by GC or HPLC techniques. In this study a comparison was made between the more traditional methods and indirect method of NaOH 5% extraction followed by colorimetric analyses. It was observed that the content of NaOH 5% extract correlates very well with pulp xylan content and reasonably well with the pentosan content. It is concluded that the 5% NaOH solubility method can be used in replacement of the other two, since it is faster, simpler and less costly to carry out than the others.

RESUMO Nesse estudo, foram avaliadas seqüências “Total Chlorine Free” (TCF) para o branqueamento de fibras secundárias provenientes de três fontes diferentes. As polpas foram branqueadas a um nível mínimo de alvura de 78% ISO, sendo que a quantidade necessária de reagentes e as suas principais propriedades foram avaliadas. A utilização do ozônio mostrou-se eficiente no branqueamento TCF, pois permitiu alcançar a alvura objetivo nos três tipos de polpas, por meio das seqüências (ZQ)P e (ZQ)(PO). As letras apresentadas nas seqüências de branqueamento possuem os seguintes significados: os estágios de ozônio, Z, seguido de uma quelação, Q, e um simples estágio de peróxido, P, ou um estágio de peróxido pressurizado com oxigênio (PO). E também reduziu significativamente a coordenada de cor b* e ligeiramente a fluorescência das polpas. Os resultados de rendimento para os processos avaliados nesse estudo foram afetados negativamente por estágios alcalinos, como oxigênio, O, P e (PO), em altas temperaturas e também pela origem das polpas de fibras secundárias.

ABSTRACT In this study, Total Chlorine Free (TCF) bleaching processes were evaluated for bleaching a secondary fiber of different origens. The samples were bleached to a target brightness of 78 % ISO. The results were interpreted on the basis of chemical cost to reach the target brightness, bleaching yield and bleached pulp quality as measured by viscosity, fluorescence and b* color coordinate. The ozone stage was responsible for improve TCF bleaching performance. The pulp bleached by sequences contained an ozone stage followed by chelation, without interstage washing (ZQ), and a final hydrogen peroxide stage unpressurized (P) or pressurized with oxygen (PO), designed as (ZQ)(PO) showed good results. These sequences decreased pulp b* coordinate significantly and fluorescence slightly. For all three bleaching processes, it was determined that process yield is negatively affected by hot alkaline stages such as oxygen, O, peroxide, P, and peroxide pressurized with oxygen, (PO) and also for the origin of the pulps of secondary fibers.

RESUMO Neste estudo foram avaliadas seqüências ECF e TCF para o branqueamento de celulose de fibras secundárias destintadas provenientes de uma mistura de composição conhecida de lixo de escritório (MOW) e produzidas em planta piloto. A polpa foi branqueada a um nível mínimo de alvura de 78% ISO, sendo que o requerimento de reagentes e as principais propriedades da polpa foram avaliadas. Dentre as seqüência ECF, a mais atrativa foi a DEDD que apresentou o mais baixo custo e ainda eliminou toda a fluorescência e grande parte da coordenada de cor b* da polpa. As seqüências ECF resultaram em polpas de alta viscosidade em relação às convencionais. A seqüência TCF com ozônio mais atrativa foi a Q(PO)(ZQ)(PO) que se mostrou flexível quanto ao teto de alvura, além de reduzir significativamente a coordenada de cor b* e ligeiramente a fluorescência da polpa. A melhor seqüência TCF sem-ozônio Q(PO)Q(PO) apresentou-se pouco flexível quanto ao teto de alvura e teve pouco efeito na fluorescência e coordenada de cor b* da polpa. As viscosidades finais das polpas, branqueadas pelos processos TCF, foram aceitáveis. Os resultados de rendimento, para os processos avaliados nesse estudo, foram afetados negativamente por estágios alcalinos, como O, P e (PO), em alta temperatura.

ABSTRACT In this study, ECF and TCF bleaching processes were evaluated for the bleaching of a deinked mixed office waste (MOW) pulp sample produced in a pilot plant. The sample was bleached by all processes to a target brightness of 78 % ISO minimum. The results were interpreted on the basis of chemical cost to reach the target brightness, bleaching yield and bleached pulp quality as measured by viscosity, fluorescence and b* color coordinate. Among the ECF sequences, the mosattractive was the DEDD which showed the lowest chemical cost and produced bleached pulp of high quality as measured by viscosity, fluorescence and b* coordinate. The best TCF sequence with ozone was the Q(PO)(ZQ)(PO) which resulted in very high brightness ceiling. This sequence decreased moderately the pulp b* coordinate and viscosity and slightly its fluorescence. Among the TCF sequences without ozone the Q(PO)Q(PO) was the most effective but showed poor flexibility with regard to brightness ceiling. This sequence had little effect on pulp viscosity, fluorescence and b* coordinate. For all three bleaching processes, it was determined that process yield is negatively affected by hot alkaline stages such as O, P and (PO).