Kinetic study and real-time monitoring strategy for tempo-mediated oxidation of bleached eucalyptus fibers

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Cellulose 
https://doi.org/10.1007/s10570-022-05013-7
ORIGINAL RESEARCH
Kinetic study and real‑time monitoring strategy 
for TEMPO‑mediated oxidation of bleached eucalyptus 
fibers
André Mazega · Alexandre F. Santos · 
Roberto Aguado · Quim Tarrés · Núria Fiol · 
M. Àngels Pèlach · Marc Delgado‑Aguilar
Received: 3 October 2022 / Accepted: 19 December 2022 
© The Author(s) 2022
Abstract The present work aims at glimpsing the 
rate-determinant process parameters of TEMPO-
mediated oxidation of bleached kraft cellulose for 
developing kinetic models and real-time monitoring 
tools. This may contribute to the scaling up of 
this reaction, frequently used as precursor of the 
production of cellulose nanofibers. For this, the 
effect of temperature, TEMPO and NaBr contents, 
and surface area of the fibers was assessed by means 
of a total experimental batch of 18 combinations, 
monitoring the carboxyl content (CC) of the samples 
and the NaOH consumption during oxidation. The 
obtained data was used to calculate the kinetic 
constant as a function of the conditions, as well as 
correlating the CC with the NaOH consumption, 
obtaining a strong linear correlation between these 
parameters. It was found that similar correlations 
could be used regardless process conditions, except 
for the case of TEMPO, which was found to protect 
the fibers from depolymerization and, thus, having 
different behavior at increasing TEMPO contents. 
Overall, the obtained results in the present study 
reveal the suitability of upscaling TEMPO-mediated 
oxidation, as well as having a deeper understanding 
on how the key parameters involved in the reaction 
affect the reaction path and, thus, contributing to 
the industrial deployment of oxidized cellulose and 
nanofibers.