Kinetics of Eucalypt Lignosulfonate Oxidation to Aromatic Aldehydes by Oxygen in Alkaline Medium
authors Santos, SG; Marques, AP; Lima, DLD; Evtuguin, DV; Esteves, VI
nationality International
journal INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
keywords FINE CHEMICALS; SULFITE LIQUOR; VANILLIN; LIGNIN; DELIGNIFICATION; CHEMISTRY; GLOBULUS
abstract The oxidation kinetics of lignosulfonates (LS) from acidic magnesium-based sulfite pulping of Eucalyptus globulus wood with oxygen under alkaline conditions was studied. The analysis of oxidation products in the reaction system O(2)/NaOH revealed a predominance of aromatic aldehydes (vanillin and syringic aldehyde) though small amounts of vanillic and syringic acids and acetophenone/phenylacetaldehyde derivatives have also been detected. The rate constant of syringic aldehyde formation was roughly twice of that for vanillin. The effective activation energies for the oxidation of LS to aromatic aldehydes (ca. 60-70 kJ/mol) were rather different to those found for the formation of aromatic acids (ca. 110 kJ/mol) indicating different mechanisms involved in the rate-determining reaction step. The addition of catalyst (copper salt, 20% w/w) promoted the LS oxidation with increments of aromatic aldehyde yields by 25-50%. The maximum yields of syringic aldehyde and vanillin upon LS oxidation were 16.1 and 4.5%, respectively (150 degrees C, 20 min, P(O2) = 10 bar, 0.9 M NaOH solution). The highly negative effect of concomitant sugars in sulfite liquor to the yield of aromatic aldehydes was highlighted.
publisher AMER CHEMICAL SOC
issn 0888-5885
year published 2011
volume 50
issue 1
beginning page 291
ending page 298
digital object identifier (doi) 10.1021/ie101402t
web of science category Engineering, Chemical
subject category Engineering
unique article identifier WOS:000285570700034
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