Greener synthesis of nanofibrillated cellulose using magnetically separable TEMPO nanocatalyst

Abstract

Nanofibrillated cellulose was synthesized by magnetically separable 4-oxo-2,2,6,6 tetramethylpiperidine-1 oxyl (TEMPO) mediated oxidation and mechanical disintegration of wood pulp.

Isolation of phenolic monomers from kraft lignin using a magnetically recyclable TEMPO nanocatalyst

“…27,28 We had previously anchored 0.3 mmol g −1 TEMPO on magnetic nanoparticles and used it successfully to oxidize pulp fibres. 29 In this work, we report the use of the same catalyst designated as Fe@MagTEMPO for the oxidative depolymerization of lignin to obtain a higher yield of vanillin with a lower calculated E factor than previously reported in the literature (Scheme 1 and Table S1 †). Overall, the isolation of phenolics utilizing oxidative methods has been recently reviewed; 15,30,31 it is worth noting germane studies listed in Table S1.…”

“…The Fe@MagTEMPO catalyst has been found to be stable even at 65°C in a previous study. 29 Further, the reaction mixture (4 h, 25°C, 5 mmol g −1 NaClO), the reaction mixture without the Fe@MagTEMPO catalyst (same conditions), and the reaction mixture with homogeneous TEMPO (same conditions) were analyzed with ICP analysis; no statistical differences were detected for the concentration of Fe and Si in the mixtures amongst the three samples (Table S3 †).…”

Industrial Application of Nanocelluloses in Papermaking: A Review of Challenges, Technical Solutions, and Market Perspectives

“…However, some TEMPO catalyst was degraded during electrolysis process and, therefore, they proposed first to recover the TEMPO catalyst by solid phase extraction (SPE) using a combination of hydrophobic resin material and distillation, and then carry out the regeneration of hypochlorite by electrolysis [169]. On the other hand, Patankar and Renneckar [172] reported the synthesis of heterogeneous magnetic TEMPO catalyst which it was recovered from the reaction mixture and reused avoiding the release of the catalyst into wastewater streams during CNF synthesis. At room temperature, the carboxylic content and rate of oxidation with heterogeneous catalyst were 0.54 mmol/g and 0.085 mmol/g·h, respectively, which were slightly lower than the values obtained by homogeneous TEMPO-mediated oxidation, carboxylic content of 1 mmol/g, and rate of oxidation of 0.48 mmol/g·h, but the oxidation level was enough to favor the fibrillation and, thus, CNF production.…”

Sol–gel Entrapped Nitroxyl Radicals: Catalysts of Broad Scope

“…More recently, the Karimi's catalyst was successfully applied to the green synthesis of cellulose nanofibrils (CNF) in water, by oxidising part of the wood pulp C 6 surface hydroxyls on cellulose microfibril surfaces to carboxylic acid groups. The reaction uses aqueous NaOCl as primary oxidant and a catalytic amount of NaBr as promoter and takes place in water only at the surface of the solid catalyst . The catalyst was found reusable for 4 successive reaction cycles (Figure ) with no nitroxyl radical leaching, thereby opening the route to greener and less costly industrial process for the synthesis of CNF, even though the extent and rate of oxidation with the heterogeneous catalyst were slightly lower than those obtained with homogeneous TEMPO.…”

“…TEM images of fresh magnetically core-shelln anoparticle-supported TEMPO catalyst and 15 days agedc atalyst in NaOHs olution at pH 10 (top);and (bottom) reusability of the catalyst for oxidation of cellulose pulp: 2gbleacheds oftwood pulp, 0.2 Lw ater,0.1 mmol NaBr,0.175 mg cm À3 solid catalyst, 5mmolg À1 NaClO, NaOH( 0.5 m)t om aintainpH10. [Reproduced from Ref [20]. w ith kind permission.…”