Kinetic study on TEMPO-mediated selective oxidation of regenerated cellulose

Sun, Bin; Gu, Chunju; Ma, Jianqing; Liang, Biao

doi:10.1023/b:cell.0000049409.56806.da

Cited by 27 publications

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“…The activation energy of the TEMPO oxidation of kraft pulp was 58.4 kJ/mol for the initial phase and 66.9 kJ/mol for the end phase. These values for the activation energy are similar to values reported for TEMPO oxidation of various substrates, e.g., 58 kJ/mol for α-D-glucopyranoside (de Nooy et al 1995), 66.2 kJ/mol for rayon (Sun et al 2005), and 56.7 kJ/mol for cotton linter (Dai et al 2011). Figure 11 shows that the reaction rate of the TEMPO/NaBr/NaClO system was not affected by the concentration of hypochlorite ions.…”

supporting

confidence: 82%

“…2), i.e., the nitrosium ion (A), the nitroxyl radical (B), and the hydroxyl amine (C). The reactions involved in TEMPO oxidation of cellulose have been described in de Nooy et al (1995), Bragd et al (2000), and Sun et al (2005). The nitrosium ion is involved in the reactions where primary hydroxyl groups on the cellulose fibres are oxidized to carboxylic acids via aldehyde intermediates.…”

Section: Reactionsmentioning

confidence: 99%

“…In an earlier study, de Nooy et al (1995) found in experiments with TEMPO/NaBr/NaClO and methyl α-D glucopyranoside that the rate of carboxylate group formation was much faster (about seven times faster) than the rate of aldehyde group formation. TEMPO oxidation kinetics has also been studied for regenerated cellulose, e.g., rayon fibres (Sun et al 2005), and for cotton linters (Dai et al 2011), where the kinetics was modeled using a homogeneous reaction model. Sun et al (2005) found that the experimental data could be well fitted to a first-order reaction expression with respect to the primary oxidant (NaClO).…”

Section: Introductionmentioning

confidence: 99%

“…TEMPO oxidation kinetics has also been studied for regenerated cellulose, e.g., rayon fibres (Sun et al 2005), and for cotton linters (Dai et al 2011), where the kinetics was modeled using a homogeneous reaction model. Sun et al (2005) found that the experimental data could be well fitted to a first-order reaction expression with respect to the primary oxidant (NaClO). For cotton linters, Dai et al (2011) found that the kinetics could be described by two first-order expressions, i.e., one for the rapid initial reaction and one for the remaining part of the reaction.…”

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High Temperature TEMPO Oxidation in a Heterogeneous Reaction System: An Investigation of Reaction Kinetics, Pulp Properties, and Disintegration Behavior

Brodin¹,

Theliander²

2013

BioResources

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TEMPO oxidation was performed on never-dried bleached softwood kraft pulp fibres to study the influence of reaction temperature and the dosage of sodium hypochlorite in the oxidation treatment. It was found that oxidation at a high temperature shortened oxidation time, but it also resulted in more extensive degradation of the pulp. Harsh reaction conditions (high temperature and high dosage of sodium hypochlorite) enabled the rapid disintegration of pulp fibres with a low energy demand. The freeze-dried disintegrated pulp fibres had a high absorption capacity of saline liquid, 40 to 80 g/g, and retained 9 to 14 g saline liquid/g material in a standard centrifuge retention test. Four different models were investigated to describe the kinetics of TEMPO oxidation of pulp fibres. However, none of the models could adequately describe all the mechanisms involved in this reaction system. The results showed that the diffusion of hypochlorite ions was sufficiently fast compared to the chemical reactions. In contrast, the concentration of the catalytic compounds, NaBr and TEMPO, both had a strong influence on the reaction rate. Results show that the reactions have different phases, possibly with different rate-determining steps. It remains to be determined which reaction steps correspond to the different phases. Keywords INTRODUCTIONCellulose is currently only used in a few different products, mostly various paper products, but the demand for new cellulose-based products, e.g., viscose and various cellulose derivatives, is growing. Because cellulose is the most abundant biomaterial on earth, it can be expected that cellulose-based products will find many new applications in the future, e.g., as replacement products in applications that, today, are dominated by products produced from fossil-based resources.Cellulose extracted from wood using chemical pulping methods is an excellent starting material for developing new biomaterials. In many cases, however, it will be necessary to modify the cellulose properties to fulfill the needs of the new applications. There are many ways of modifying cellulose, and one of these is oxidizing the hydroxyl groups in the cellulose, thus forming new aldehyde and carboxylate groups. Primary hydroxyl groups can be oxidized selectively through so-called TEMPO oxidation, where a catalytic amount of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediates the oxidation of cellulose and is regenerated by a primary oxidant (Bragd et al. 2004). This PEER-REVIEWED ARTICLE bioresources.com Brodin and Theliander (2013). "TEMPO ox. kinetics," BioResources 8(4), 5925-5946. 5926 type of modification also causes a substantial decrease in the degree of polymerization (DP) (Saito and Isogai 2004), i.e., the molecular weight of the cellulose polymers decreases. Saito et al. (2006) found that TEMPO-oxidized pulp fibres could be disintegrated into microfibrillar cellulose (MFC) through treatment in a Waring blender. Furthermore, they reported that the disintegration of TEMPO-oxidized sulfite pulp was facilitat...

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supporting

confidence: 82%

Section: Reactionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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High Temperature TEMPO Oxidation in a Heterogeneous Reaction System: An Investigation of Reaction Kinetics, Pulp Properties, and Disintegration Behavior

Brodin¹,

Theliander²

2013

BioResources

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“…In general, cotton fiber (Dai et al 2011), softwood pulps (Dang et al 2007), hardwood pulps (Fukuzumi et al 2010, Mishra et al 2011, lignocellulosic fibers (Hamid et al 2011), and regenerated cellulose (Sun et al 2005) can be oxidized by a TEMPO/ NaClO/NaBr aqueous system. During the reaction, sodium hypochlorite solution is typically added all at once before the reaction (Qin et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Influence of Buffer Solution on Tempo-Mediated Oxidation

Xu¹,

Sun²,

Wang³

et al. 2012

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TEMPO-mediated oxidation has been reported to effectively convert C6 primary hydroxyl groups to carboxyl groups for better water-solubility. However, the pH decreases continuously during the oxidation process, and it is therefore difficult to maintain the stability of the reaction. The control of pH at a constant level throughout the oxidation process is a complicated task. The applicability of a carbonate buffer system and a borax buffer system with various continuous addition rate of sodium hypochlorite solution was considered. Carbonate buffer solution and borax buffer solution can efficiently buffer the pH. The results of carboxyl content and DP of celluloses proved that the activities of sodium hypochlorite solution can be maintained when sodium hypochlorite is added with controlled flow rates without adjusting pH by hydrochloric acid. Buffer solutions created a milder reaction environment in which the damage of celluloses would be buffered. The conclusion was consistent with DP tests of celluloses. Compared with carbonate buffer, the borax buffer with high ability of penetration could enhance the depth and width of oxidation, which was demonstrated by the results of X-ray diffraction patterns and carboxyl content of celluloses.

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Commercialization of Cellulose Nanofibril (CNF) and Cellulose Nanocrystal (CNC): Pathway and Challenges

Rudie

2017

Handbook of Nanocellulose and Cellulose Nanocomposites

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Kinetic study on TEMPO-mediated selective oxidation of regenerated cellulose

Cited by 27 publications

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High Temperature TEMPO Oxidation in a Heterogeneous Reaction System: An Investigation of Reaction Kinetics, Pulp Properties, and Disintegration Behavior

High Temperature TEMPO Oxidation in a Heterogeneous Reaction System: An Investigation of Reaction Kinetics, Pulp Properties, and Disintegration Behavior

Influence of Buffer Solution on Tempo-Mediated Oxidation

Commercialization of Cellulose Nanofibril (CNF) and Cellulose Nanocrystal (CNC): Pathway and Challenges

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