The Effect of Aluminum on the Two-Stage Pe rox i d e B I each i n g of Eucalyptus regnans Stone Groundwood Pulp
The addition of aluminum nitrate (up to 100 ppm A1 on pulp) to a two-stage, acidalkali, hydrogen peroxide bleach of Eucalyptus regnans stone groundwood pulp enhanced the brightness gain of the pulp, over a range of consistencies. It is proposed that the presence of aluminum ions modifies the catalytic behaviour of the transition metal ions present in the pulp, especially manganese, reducing peroxide consumption while increasing the brightness of the pulp. The two-stage process, under optimized conditions at low consistency, consumes considerably less peroxide while achieving a greater brightness increase than a singlestage alkaline peroxide bleach.
Sulfite-anthraquinone pulping of southern pine for bleachable grades
Etude experimentale detaillee de la mise en pâte, de la selectivite, du rendement, des caracteristiques et de l'aptitude au blanchiment des pâtes, comparaison avec des pâtes kraft
The «catalytic» effect of anthrone and anthrahydroquinone in cleaving β-aryl ether bonds in lignin model compounds
Abstract To elucidate the mechanism of anthrone-promoted β -ether cleavage reactions, the phenolic lignin model compound 1, 1-(4-hy-droxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol, was heated with 0.1 mole of anthrone (AN) or anthrahydroquinone (AHQ) at 140 °C for 1/2, 1, 2, 3 and 5 hours in 1 M sodium hydroxide solution. The cleavage products [2-methoxyphenol and (2-meth-oxy-4-propenyl)phenol] were the same as in experiments with equimolar amounts or excess of AN and the yields increased as a function of reaction time to a maximum corresponding to the cleavage of four to five moles of 1 per one mole of AN. AHQ was found to react in a similar manner. This “catalytic” effect is tentatively attributed to sequential transformations of AN and AHQ to products capable of causing further reductive cleavages. GC-MS analysis of the reaction mixture showed the presence of by-products which indicate that some catalyst regeneration through oxidation of 1 or its hydrolysis products may have occured. 1-Hydroxyan...