纸浆漂白臭氧处理段纤维素分子上羰基的形成

Formation of carbonyl groups on cellulose during ozone treatment of pulp:Consequences for pulp bleaching

研究了纸浆臭氧漂白过程中,木素和乙烯糖醛酸的存在对纤维素上羰基的形成及纤维素降解的影响。在碱抽提段(E),采用C C OA方法{以咔唑-9-羧酸[2-(2-氨基氧杂乙氧基)-乙氧基]酰胺作为羰基的选择性荧光标记物}对纸浆中的羰基进行跟踪检测。研究表明:在臭氧漂白过程中,己烯糖醛酸、木素与臭氧反应形成的自由基导致纤维素和半纤维素上形成羰基并致使纤维素降解。此外,还发现羰基的总量在E段有所下降,但在随后P段,当H2O2不够稳定的时候又会有所增加。最后,提出了几种有助于减少羰基形成的方法。

The formation of carbonyl groups during the ozonetreatment （Z） of eucalyptus （Eucalyptus grandis and Eucalyptusurophylla hybrid） kraft pulps and their behaviors during subsequentalkaline stages were investigated by the CCOA method withcarbazole-9-carboxylic acid [2-（2-aminooxethoxy）-ethoxy] amide（CCOA） as the carbonyl-selective fluorescence label. Several pulpsamples with or without lignin and hexenuronic acid （HexA） wereused to elucidate the effects of these components when present inunbleached kraft pulp. Both HexA and lignin increased the formationof carbonyl groups on cellulose and hemicellulose during ozonation.It was concluded that radicals are likely formed when ozone reactswith either lignin or HexA. These carbonyl groups were involved incellulose depolymerization during subsequent alkaline extractionstages with sodium hydroxide （E） and alkaline hydrogen peroxide （P,in ZEP or ZP）. Their numbers decreased after E but increased duringP when H2O2 was not stabilized enough. Several ways to minimizethe occurrence of carbonyl group formation are suggested.