Study On The Influence Factors Of Color And Bleaching Of Alkyl Polyglycosides

Generally pure alkyl polyglycosides are white powder. However in practical industrialsynthesis, recombination reaction and decomposition reaction are liable to occur at hightemperature and acid environment, generating polysaccharides and other colored substances.The color bodies were presumed as polymerized dehydration and degradation products ofsaccharides, such as levulinic acid, furfural, or hydroxymethyl furfural. These polymers,known as humins, show conjugated unsaturated moieties that absorb light and may beresponsible for the dark-hued discoloration of the alkyl polyglucosides. Alkylpolyglycosides are generally brown after dealcoholization reaction, which seriously affectsits application scope and commercial value. Therefore, bleaching of alkyl polyglycosidessolution becomes extremely important.The coloration mechanism, the causes of the color and the optimization of theproduction process of alkyl polyglycosides were summarized firstly, and then the bleachingof the alkyl polyglycosides was studied. This paper explored the impacts of H2O2/TAED/NaOH system on the bleaching effect with NaOH as alkaline agent. The single factor testand orthogonal experiment have been carried out respectively, and the the optimalbleaching conditions were as follows: bleaching temperature of55℃, addition of TAEDwas3.2%, addition of H2O2was8.3%, addition of NaOH (the mass fraction was50%) was1.4ml, and the PH value of the corresponding10%aqueous solution was12.12, addition ofMgO was0.11%. The sequence of every factor for the bleaching effect was NaOH, H2O2,temperature, TAED, MgO in turn.Besides, the effect of H2O2/TAED/NaHCO3system, namely NaHCO3as alkaline agentwith the (tetra acetyl ethylene diamine (TAED))TAED-activated peroxide system,bleaching of alkyl polyglycosides solution was studied. The results showed that the optimalbleaching conditions about H2O2/TAED/NaHCO3system bleaching of alkyl polyglycosidessolution were as follows: molar ratio of TAED to H2O2was0.06, addition of H2O2was8.6%, addition of NaHCO3was3.2%, bleaching temperature of50℃～65℃, addition ofMgO was0.13%, and bleaching time was8h. TAED as the bleach activator is often applied in bleaching of pulp, fiber, fabric, etc.This paper emphasized on the study of TAED application in bleaching of alkylpolyglycosides. In the TAED-activated peroxide system, using NaOH as alkaline agent, theblack precipitate could be formed easily in the APGs solution after bleaching. While,NaHCO3was chosen as alkaline agent and buffer agent, which has overcome thedisadvantage of producing black precipitates. If too much amount of NaHCO3was addedand maintained alkaline pH, the bleaching effect would be greatly reduced. Fixing molarratio of TAED to H2O2and increasing the amount of H2O2were beneficial to improve thewhiteness of APGs, but adding too much amount of H2O2would reduce the transparency.