N-methylmorpholine-N-oxide Research Articles

Flax Noils as a Source of Cellulose for the Production of Lyocell Fibers

The production of long flax fiber for the subsequent production of textile yarn is accompanied by the formation of a significant amount of waste—noils, which is a mechanical mixture of long and short flax fibers and shives. Comparative studies of the structure and chemical composition of the fibrous fraction of noils and shives were carried out using IR spectroscopy. The solubility of shives and flax noils in N-methylmorpholine-N-oxide (NMMO) was studied, a comparative analysis of the rheological behavior of solutions of flax and wood cellulose was carried out and the optimal temperature–concentration conditions for obtaining flax fibers from noils were determined. It was shown for the first time that using the method of solid-phase activation of the cellulose-solvent system makes it possible to obtain fibers in a short period of time (no more than 10 min). The structure of both the raw material and the resulting fibers was studied by X-ray diffraction analysis. The thermal properties of a new type of cellulose fibers was evaluated. The complex of the conducted studies allows us to consider flax fibers from noils along with flax fibers from long-staple flax, as a real alternative to fibers from wood pulp.

CELLULOSE/WOLLASTONITE BASED GREEN MEMBRANES USING RICE STRAW: FABRICATION AND CHARACTERIZATION

Cellulose/wollastonite membranes were prepared with an environmentally friendly process using N-methylmorpholine-N-oxide (NMMO), which resulted in mesoporous membranes with slit-shaped pores. Cellulose and wollastonite were extracted from rice straw with different methods. Some parameters, such as weight ratios of cellulose and wollastonite in solution, concentration, thickness of the cast solution on the support layer and porosity of the support layer, influence the formation of the porous cellulose/wollastonite membrane. It was concluded that the porosity and pore size of the cellulose/wollastonite membrane decreased with lower cellulose and higher wollastonite amounts. The membranes became more brittle by increasing the amount of wollastonite, while pure cellulose membranes did not have enough strength to be placed on the polyester support layer. Also, the concentration of cellulose should not be too high or too low. The thickness of the cast solution on the support layer should not be too high, as it reduces the porosity; on the other hand, low thickness reduces the performance of the membrane.

An in vitro approach to determine the human relevance of anti-spermatogenic effects of 4-methylmorpholine 4-oxide, monohydrate (NMMO) in rat reproductive toxicity studies

Reduced sperm counts have been observed in male rats in an extended one generation reproductive toxicity study (EOGRTS, OECD 443) following repeated administration of 300 mg/kg/day N-Methylmorpholine N-oxide (NMMO). However, no adverse effects on reproductive organs have been reported in studies conducted with NMMO, and the mode of action (MOA) for the effects of NMMO on spermatogenesis is unknown, which complicates the interpretation of these data for human risk assessment. Here, a New Approach Method (NAM) strategy was used to evaluate NMMO MOA and compare interspecies susceptibility for anti-spermatogenic effects using organotypic in vitro assays combined with in vitro metabolism and in vitro to in vivo extrapolation (IVIVE) biokinetic modeling to compare predicted oral equivalent doses (OEDs) in human and rat. Dose-response data were collected in isolated germ cells and in an ex vivo seminiferous tubule model that recapitulates the interaction between the somatic environment and differentiating germ cells to account for potential direct and indirect effects on germ cells. With regard to direct spermatogenic effects, the human isolated germ cell model showed no toxicity at doses ≤300 μM (OED ≤ 86 mg/kg/day). With regard to indirect effects, the rat ex vivo model demonstrated dose-dependent decreases in secondary spermatocyte populations at OEDs ≥89 mg/kg/day, and reduced expression of RNAs specific to several stages of spermatogenesis (spermatogonia, pachytene spermatocytes, round spermatids) at OED = 267 mg/kg/day, consistent with in vivo observations. In contrast, the monkey ex vivo model did not show dose-dependent decreases in these same RNAs, and often demonstrated increased trends instead. These studies demonstrate clear quantitative and qualitative differences in the rat and primate response to NMMO. Furthermore, effects observed in the rat in vitro culture were not observed in the monkey at concentrations equivalent to in vivo doses of up to 1376 mg/kg/day, which is higher than the in vivo dose limit in the EOGRT study, indicating that the isolated findings on spermatogenesis in the rat studies are not likely to be relevant to humans.

Cellulose liquid crystal templated TiO2 chiral nematic foams

Aerogels with chiral nematic structure are promising candidates for structural coatings and optical devices. Cellulose nanocrystals (CNCs) are excellent photonic building blocks for the fabrication of chiral nematic aerogels. Conventional bottom-up fabrication process usually is complicated, energy and time consumption. Herein, a simple method for fabricating CNCs and polyethylene glycol (PEG) based foams with chiral nematic structure was proposed. After CNCs-PEG based solid films were swollen with N-methylmorpholine N-oxide (NMMO) aqueous solutions, the obtained hydrogels were freeze-dried, resulting in chiral nematic foams. During the process, both macropores and mesopores were created with chiral nematic phase retained inside foam walls. Owning numerous macropores and chiral nematic walls of varying axial directions, the chiral nematic foams exhibited a broad-band reflection phenomenon. Moreover, the representative Titanium diisopropoxide(bis-2,4-pentanedionate) was permeated into foam walls, and transformed into chiral nematic TiO2 foams after annealing. We envisage that the chiral nematic foams may have a promising application in the fields of chiral separation or chiral catalysis.

Hydrogen bonding in ternary mixtures of N-Methyl morpholine Oxide, water and Dimethyl sulfoxide for enhanced cellulose dissolution capabilities

N-Methylmorpholine-N-oxide (NMMO) is the solvent of choice in the lyocell process because of the interesting biodegradable, non-toxic and non-ecotoxic features that the full recovery of NMMO provides to the process. NMMO is used in its monohydrate form (1NMMO:1H2O) and cellulose dissolution occurs via hydrogen bond (HBs) formation between the oxygen at the oxide group (as the HB acceptor, HBA) and the hydroxyl groups of the cellulosic units (as the HB donor, HBD). Interestingly, H2O is a serious competitor for NMMO to form HBs with cellulose so the number of H2O-cellulose-HBs should be kept under control. Addition of co-solvents has become a common practice and the challenge is studying the capability of this additional co-solvent to balance the NMMO-cellulose-HBs versus H2O-cellulose-HBs and thus modify the solvent capabilities of the resulting ternary mixture. Herein, we prepared ternary mixtures by addition of the respective equivalents of H2O and DMSO (e.g., 1:0.5, 1:1 and 0.5:1) to anhydrous NMMO to obtain 1NMMO:1H2O:0.5DMSO, 1NMMO:1H2O:1DMSO and 1NMMO:0.5H2O:1DMSO. We correlated the solvent capability with the HB formed among the components in the different three ternary mixtures. 1NMMO:0.5H2O:1DMSO controlled the number of H2O-cellulose-HBs better than the other two mixtures and this helped to maintain the resulting cellulose solution in the liquid form at room temperature.

Copper (II) bromide catalysed one pot bromination and amination for the green, cost-effective synthesis of clopidogrel

Copper (II) bromide catalyzed one pot α-bromination and followed by amination of a benzylic ester is reported. The α-bromination of ester by copper (II) bromide generates copper (I) bromide and HBr. The copper (I) bromide is oxidized to copper (II) bromide by N-Methylmorpholine-N-Oxide (NMO) in presence of HBr. The amines undergo nucleophilic substitution reaction with α-brominated ester compound. This methodology was applied for the synthesis of the familiar antiplatelet drug clopidogrel. This green process is an alternate to classical methods for the synthesis of clopidogrel, which requires, generates stochiometric amount of brominating agents and HBr, respectively.

Structure, Morphology, and Permeability of Cellulose Films.

The work is focused on the study of the influence of the cellulose type and processing parameters on the structure, morphology, and permeability of cellulose films. The free volume of the cellulose films was evaluated by the sorption of n-decane, which is a non-solvent for cellulose. The structural features of the membranes and their morphology were studied using X-ray diffraction, IR spectroscopy, SEM, and AFM methods. The characteristic features of the porous structure and properties of cellulose films regenerated from cellulose solutions in the N-methylmorpholine-N-oxide (NMMO) and cellophane films were compared. Generally, cellulose films obtained from solutions in NMMO have a higher permeability and a lower rejection (as measured using Orange II dye) as compared to cellophane films. It was also found that the cellulose films have a higher ultimate strength and modulus, whereas the cellophane films are characterized by higher elongation at break.

Efficient ethanol production from rice straw through cellulose restructuring and high solids loading fermentation by Mucor indicus

The production of high concentrations of ethanol from N-methylmorpholine N-oxide- (NMMO) and phosphoric acid-pretreated rice straw was investigated at high solid loadings (solid-state) using filamentous fungus Mucor indicus. The impacts of most influential factors on ethanol production by simultaneous saccharification and fermentation (SSF), i.e., enzyme loadings (2.5, 5, 10, and 20 FPU/g substrate), solids loadings (15, 20, and 30% w/w), and SSF time (72 and 120 h), were assessed. The highest glucose concentrations were 106.5 and 94.1 g/L gained from 72-h hydrolysis of the straw pretreated with NMMO and phosphoric acid at 15% (w/w) solids loadings, respectively. The highest ethanol concentrations were 63.4 and 69.0 g/L, achieved by 30% solids loading from 72-h SSF of the straw pretreated with NMMO and phosphoric acid at 20 and 10 FPU celluloses per g substrate, respectively. A prolonged SSF process at enzyme loadings less than 5 FPU/g straw could not improve ethanol concentration from NMMO-pretreated straw, while ethanol concentrations above 40 g/L (61.0 and 59.9 g/L) were achieved through 120-h fermentation of the straw pretreated with phosphoric acid at 30% solid loading. The highest ethanol yields were 73.7 and 100% of the theoretical yield gained from the straw pretreated with phosphoric acid and NMMO, respectively, at the lowest solids loading (15%) and the highest enzyme loading (20 FPU/g substrate).

Preparation and Characterization of Regenerated Cellulose Membrane Blended with ZrO2 Nanoparticles.

It is of great significance to search for efficient, renewable, biodegradable and economical membrane materials. Herein, we developed an organic-inorganic hybrid regenerated cellulose membrane (ZrO2/BCM) with excellent hydrophilic and anti-fouling properties. The membrane was prepared by introducing ZrO2 particles into an N-Methylmorpholine-N-oxide(NMMO)/bamboo cellulose(BC) solution system by the phase inversion method. The physi-chemical structure of the membranes were characterized based on thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). The modified regenerated cellulose membrane has the excellent rejection of bovine serum albumin (BSA) and anti-fouling performance. The membrane flux of ZrO2/BCM is 321.49 (L/m2·h), and the rejection rate of BSA is 91.2%. Moreover, the membrane flux recovery rate after cleaning with deionized water was 90.6%. This new type of separation membrane prepared with green materials holds broad application potential in water purification and wastewater treatment.

Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent–cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

Carboxylate functionalized imidazolium-based zwitterions as benign and sustainable solvent for cellulose dissolution: Synthesis and characterization

Cellulose is most abundant biopolymer on earth and can be utilized as sustainable resources for many applications, however, their utilization at great extent is limited due to lack of benign and recyclable solvent. While N-methylmorpholine-N-oxide (NMMO), used in Lyocell process, is thermally unstable and may undergoes runaway conditions, commercialization of ionic liquid as solvent still suffers from recyclability issues. Herein, we present the synthesis of a series of zwitterions, composed of tethered alkyl imidazolium cation and carboxylate anion, and investigated their cellulose dissolution characteristics. Effect of alkyl chain length of imidazolium ring on its dissolution efficiencies was studied and amongst synthesized zwitterions, the hexanoate derivatives exhibited 13% (w/w) cellulose dissolution at 100–125 °C. Thermal stability of zwitterions and their cellulose solution was characterized by DSC-TGA and found to be more stable than the NMMO and Lyocell solution. Rheological studies indicate that cellulose solution in zwitterions are viscoelastic and in spinnable range of fibre processing. Structural and morphological characterization of regenerated cellulose using elemental analysis, FTIR, DSC-TGA, GPC, XRD and SEM showed that zwitterions have no adverse effect on its physicochemical and morphological properties. A method for recovery and purification of solvent after cellulose dissolution and regeneration is also presented.

Cellulose-Pulp-Based Stretchable Composite Film with Hydroxyethyl Cellulose and Turmeric Powder for Packaging Applications

Cellulose pulp (CP), hydroxyethyl cellulose (HEC), and turmeric-powder-based ecofriendly, transparent, and flexible composite films were prepared. The above-mentioned materials dissolved well with an environmentally friendly process using N-methyl morpholine N-oxide (NMMO) ionic liquids. The Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis studied their structure, microstructure, and morphology properties. Thermal properties of the CP/HEC/turmeric powder composites were thoroughly studied by thermogravimetric analysis (TGA) and differential scanning calorimetry analysis (DSC) and dynamic mechanical analysis (DMA) instruments. The initial thermal stability of the composites was significantly improved by the addition of HEC. All the composite films exhibited a single glass transition temperature (Tg), and it was confirmed by both DSC and DMA analysis. The tensile strength (TS) of CP was 94.5 MPa, which decreased to 19 MPa for CP/HEC-1:0.5 composites, and then, it steadily increased to 24.7 MPa with an increment of HEC. Similarly, HEC increased the elongation at break (EB) of CP from 9.4 to 67.2%. The addition of HEC into the CP composite improved its flexibility, and it is more transparent in the visible light spectrum. The water vapor permeability (WVP) and swelling ratio of CP/HEC/turmeric powder composites were in the range of 1.35–1.61 × 10–9 g/m2 Pa and 185–209%, respectively. Furthermore, the composites have no cytotoxicity to the HaCat cell line. However, they exhibited excellent antioxidant properties. These merits of CP/HEC/turmeric powder composite establish them as a potential candidate for packaging and biomedical applications.

On the role of N-methylmorpholine-N-oxide (NMMO) in the generation of elemental transition metal precipitates in cellulosic materials

Several literature reports describe the role of aqueous solutions of N-methylmorpholine-N-oxide monohydrate (NMMO) as a suitable medium for the generation of transition metal (nano)particles in or on cellulosic materials and further elaborate its role as a co-reactant of the transition metal salts that are reduced to the elemental metal. However, this would assign NMMO the role of a reductant, which is in contradiction of its obvious oxidative nature. In the present study, the exemplary cases of silver, gold, and platinum salts as the precursors of the respective metal (nano)particles in aqueous NMMO/cellulose mixtures were investigated. Naturally, NMMO did not act as a reducing agent in any case—this role was taken over by the frequently used NMMO stabilizer propyl gallate, or by cellulose itself, into which carbonyl and carboxyl groups were introduced. Also, hypochlorite—produced intermediately from chloride ions and subsequently undergoing disproportionation into chloride and chlorate—or transient N-methylene(morpholinium) ions generated from NMMO, which are in turn oxidized to formyl morpholide, can act as the corresponding reductants while the metal ions are reduced, depending on the reaction conditions. Apart from providing interesting mechanistic insights, the study points to the importance of a precise description of the composition of the chemical systems used, as well as the importance of seemingly inert auxiliaries, which turned out to be essential co-reactants in the metal (nano)particle generation.Graphic abstract

Morphological Transformations in the Process of Coagulation of Cellulose Solution in N-Methylmorpholine N-Oxide with Isobutanol

Morphological Transformations in the Process of Coagulation of Cellulose Solution in N-Methylmorpholine N-Oxide with Isobutanol

Optimisation of AgNP Synthesis in the Production and Modification of Antibacterial Cellulose Fibres.

The main aim of the presented research is to determine the optimal conditions for the production of silver nanoparticles (AgNPs) in N-methylmorpholine-N-oxide (NMMO), which will potentially allow to obtain small nanoparticles with uniform diameter distribution. In this paper, NMMO is used in the fibre production process, both as a direct cellulose solvent and as an Ag+ reducing system. From an industrial point of view, this method is very promising because it allows to reduce the amount of used chemicals. The UV/Vis, DLS and TEM analysis proved that the synthesis temperature and time could play a key role in nanoparticle growth control in NMMO. It was found that the optimal conditions for AgNPs synthesis are 100 °C and 0.33 h. The estimations of the antibacterial activity of the fibres were completed. The applied AgNPs synthesis conditions allow to obtain antibacterial fibres with a wide range of applications, mainly in medicine.

The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system

The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system

Ultra-high-strength composite films prepared from NMMO solutions of bamboo-derived dissolving pulp and chitosan

Regenerated cellulose (RC) films have numerous separation and purification applications. However, the mechanical properties of RC films are poor. Because of their very similar chemical structures and excellent compatibility, chitosan (CS) particles were chosen to reinforce bamboo-derived dissolving pulp (BP)-based films. BP/CS blend solutions were obtained by mixing BP and CS particles at different weight percentages into N-methyl-morpholine-N-oxide (NMMO) solvent. The BP/CS composite films prepared by the traditional phase transformation method formed a physically cross-linked network with high packing density for the water evaporation after air-drying. Due to the strong hydrogen bonding between CS and BP revealed by rheological properties and Fourier transform infrared (FTIR) data, the CS particles dispersed uniformly in the matrix, and the compatibility of the reinforcement with the matrix was excellent, which was further confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis transmittance data. As the weight percentage of CS increased from 9.09 wt% to 14.24 wt%, the crystallinity of cellulose II increased from 32.20%–38.59%, and the tensile strength of the BP/CS composite films increased from 662.20 MPa to 865.53 MPa, respectively. These results indicate that the tensile strength of the BP/CS composite films was increased by nearly 250.83 %–358.56 % compared with that of the regenerated BP film (188.75 MPa). Moreover, the elongation at break was increased by 51.16 %-41.63 %. These findings provide a new way to prepare ultra-high-strength RC composite films.

Preparation of cellulose nanofiltration membranes and their removal of typical pollutants from drinking water

Abstract Cellulose membranes have the advantages of good hydrophilicity, excellent mechanical properties, and biodegradability. Therefore, they are the first choice to replace petroleum polymer membranes. In this study, cellulose (BC) and chitosan (CS) were used as raw materials, and N-methylmorpholine-N-oxide (NMMO) was used as solvent. A new kind of cellulose nanofiltration membrane (BC-NFM), cellulose/chitosan nanofiltration membrane (BC/CS-NFM), and interfacial polymerized cellulose/chitosan composite nanofiltration membrane (IP-BC/CS-NFM) were successfully prepared by NaOH hydrolysis and chloroacetic acid carboxymethylation modification, piperazine (PIP), and 1,3,5-trimellitic chloride (TMC) interfacial polymerization, respectively. These two methods were used for the preparation of cellulose nanofiltration membranes for the first time.We also studied their structure, separation performance and their capacity to remove typical pollutants. The results showed that obvious holes appeared on the surface of the nanofiltration membrane obtained by alkali hydrolysis and chloroacetic acid carboxymethylation modification, and the cross-section showed a spongelike structure. The surface of the nanofiltration membrane obtained by interfacial polymerization formed a rough and dense separation layer. The rejection rates of the three kinds of nanofiltration membranes were all over 30% for monovalent salt ions, over 60% for divalent salt ions, over 92% for methyl orange, and over 98% for methyl blue. They had good removal effects for typical pollutants in drinking water.

A comparative study of the effect of cellulose-based deep coating and pulp refining on the structural and mechanical properties of paper

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the “deep coating” method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The “deep coating” name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure.

Determination of Cellulose, Water, and N-Methylmorpholine N-Oxide during the Production of Lyocell by Attenuated Total Reflection (ATR) – Fourier Transform Infrared (FTIR) Spectroscopy

Attenuated total reflection (ATR) – Fourier transform infrared (FTIR) spectroscopy with the pretreatment of converting the absorption spectrum into angle spectrum (CASAS) and partial least squares (PLS) was employed to rapidly and simultaneously determine the ingredients of cellulose slurries and solutions during lyocell production. ATR was employed to rapidly and conveniently collect the spectra of the swollen slurries and viscous solutions during production. CASAS was used to eliminate the influence on modeling by the optical path differences due to uneven ingredient distributions in the samples. The PLS models for the cellulose, water, and N-methylmorpholine N-oxide (NMMO) concentrations of the cellulose slurry/solution were constructed using the raw spectra, pretreated spectra by CASAS, and common pretreatment methods, respectively. The results show that CASAS eliminates interferences due to the differences in optical path and improves the performance of PLS model for each analyte. The standard errors of prediction (SEP) of models using CASAS for cellulose, NMMO, and water concentration of cellulose slurry were 0.368, 0.196 and 0.171, while the values for the cellulose solution were 0.442, 0.353, and 0.066, respectively. The standard errors of prediction (SEPs) of CASAS models are significantly lower than the reproducibility requirement of the reference method, 0.5. The reported approach using ATR-FTIR spectroscopy combined with CASAS and PLS is rapid and accurate for determining the ingredients of the cellulose slurries and solutions and offers potential for identifying similar samples.