TY - JOUR

T1 - Alkalization of dissolving cellulose pulp with highly concentrated caustic at low NaOH stoichiometric excess

AU - Albán Reyes, Diana Carolina

AU - Gorzsás, András

AU - Stridh, Kjell

AU - de Wit, Paul

AU - Sundman, Ola

PY - 2017/6/1

Y1 - 2017/6/1

N2 - We present a quantitative study, using Raman spectroscopy combined with multivariate data analysis, to determine the degree of activation of softwood sulphite dissolving cellulose pulp by aqueous sodium hydroxide. We have chosen industrially relevant conditions, including low stoichiometric ratio of NaOH/Anhydroglucose Unit (AGU) < 2 and highly concentrated caustic (≥45% w/w [NaOH]). A design of experiments is used to investigate the effects of simultaneous variation of a set of key parameters on the degree of activation (i.e. transformation to alkali cellulose, denoted as DoA): (a) the NaOH/AGU stoichiometric ratio, denoted (r); (b) the concentration of NaOH, denoted [NaOH]; (c) temperature, denoted (T); and (d) reaction time, denoted (t). Solid-state 13C CP/MAS NMR spectroscopy was applied to investigate the reproducibility of the experiments and to select the range for (t). According to the model, (r) is found to have a statistically significant effect on DoA (increasing from DoA = 6–30% at the lowest (r) = 0.8, to DoA = 48–87% at the highest (r) = 1.8), together with [NaOH]. The influence of [NaOH] depends strongly on (r). The other studied variables are found to be insignificant in the model and has a complicated influence on the activation. In particular, (T) is found to be unimportant in the studied range (30–60 °C), but increasing (t) from 5 to 25 min shows a positive influence on DoA, depending on both (r) and [NaOH]. A mercerisation mechanism that is controlled by diffusion is proposed to explain these phenomena.

AB - We present a quantitative study, using Raman spectroscopy combined with multivariate data analysis, to determine the degree of activation of softwood sulphite dissolving cellulose pulp by aqueous sodium hydroxide. We have chosen industrially relevant conditions, including low stoichiometric ratio of NaOH/Anhydroglucose Unit (AGU) < 2 and highly concentrated caustic (≥45% w/w [NaOH]). A design of experiments is used to investigate the effects of simultaneous variation of a set of key parameters on the degree of activation (i.e. transformation to alkali cellulose, denoted as DoA): (a) the NaOH/AGU stoichiometric ratio, denoted (r); (b) the concentration of NaOH, denoted [NaOH]; (c) temperature, denoted (T); and (d) reaction time, denoted (t). Solid-state 13C CP/MAS NMR spectroscopy was applied to investigate the reproducibility of the experiments and to select the range for (t). According to the model, (r) is found to have a statistically significant effect on DoA (increasing from DoA = 6–30% at the lowest (r) = 0.8, to DoA = 48–87% at the highest (r) = 1.8), together with [NaOH]. The influence of [NaOH] depends strongly on (r). The other studied variables are found to be insignificant in the model and has a complicated influence on the activation. In particular, (T) is found to be unimportant in the studied range (30–60 °C), but increasing (t) from 5 to 25 min shows a positive influence on DoA, depending on both (r) and [NaOH]. A mercerisation mechanism that is controlled by diffusion is proposed to explain these phenomena.

KW - Alkalinisation

KW - Cellulose ether

KW - Cellulose I

KW - Cellulose II

KW - Mercerisation

KW - Raman spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85013156223&partnerID=8YFLogxK

U2 - 10.1016/j.carbpol.2017.02.045

DO - 10.1016/j.carbpol.2017.02.045

M3 - Article

C2 - 28363542

AN - SCOPUS:85013156223

VL - 165

SP - 213

EP - 220

JO - Carbohydrate Polymers

JF - Carbohydrate Polymers

SN - 0144-8617

ER -