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N-Methylmorpholine N-oxide

About: N-Methylmorpholine N-oxide is a(n) research topic. Over the lifetime, 187 publication(s) have been published within this topic receiving 5251 citation(s). The topic is also known as: N-Methylmorpholine oxide & N-Methylmorpholine 4-oxide.

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Journal ArticleDOI
Abstract: Cellulose as the most abundant regrowing organic material exhibits outstanding properties and useful applications, but also a tremendous challenge with regard to an economical and environmentally friendly chemical processing. In recent years the N-methylmorpholine-N-oxide (NMMO)-technology turned out to be a simple physical alternative to the yet dominating viscose-technology for producing regenerated cellulosic fibers, films, food casings, membranes, sponges, beads, and others without hazardous byproducts. With consideration of own results, the present paper reviews the state of the art knowledge on structure formation of fibers and films via the NMMO-route comprising the cellulose–NMMO–water phase system, the state of solution, the dry jet-wet shaping, the precipitation, and the drying stages. Dissolving pulp as the starting material can be dissolved easily without pretreatment in NMMO-monohydrate. The fairly (8–12%) concentrated solution of cellulose in NMMO-monohydrate is characterized by a marked elastic behavior similar to a polymer melt which can be quantified by rheological measurements of the storage and loss moduli. As found by light scattering experiments of diluted cellulose–NMMO solutions, there exist aggregates of molecules even in the diluted solution, with the number of molecules corresponding to solid state morphological units (crystallites, microfibrils). As shown by WAXS-RDF analysis of the concentrated solutions at elevated temperature, the typical short-range order of a pure NMMO–water system is only slightly disturbed by the cellulose molecules. Fiber formation occurs in a dry jet-wet spinning process, with several physical factors (e.g. nozzle and air-gap dimensions, draw-down ratio, take-up speed) and dope characteristics (cellulose DP and concentration, temperature, modifiers) influencing the shaping process and the final fibers properties. The precipitation process has been shown to be another stage capable to affect the structure and properties of the fibers as, e.g. by a two-step precipitation leading to a skin–core structure and improved fiber properties (reduced fibrillation). The NMMO method offers for the first time the possibility to produce blow-extruded tube-like films similar to the polyolefine blown film processing. The influencing parameters are discussed and the properties of the new blown cellulosic films are shown to be superior to cellophane. Finally, the structures and properties of the NMMO-type fibers and films have been investigated and differences between the new materials and the traditional viscose based fibers and films were shown and related to the different structure formation routes.

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792 citations


Journal ArticleDOI
Abstract: N -Methylmorpholine- N -oxide monohydrate (NMMO) is used as a solvent for direct dissolution of cellulose in industrial fiber-making (Lyocell process). Ideally, Lyocell fiber production per se should be an entirely physical process that does not cause chemical changes in pulp or solvent. However, there are several side reactions and considerable byproduct formation in the system cellulose/NMMO/water which can cause detrimental effects, such as degradation of cellulose, temporary or permanent discoloration of the resulting fibers, decreased product performance, pronounced decomposition of NMMO, increased consumption of stabilizers, or even thermal runaway reactions. The present paper will focus on chemical aspects of the system NMMO/cellulose. After a short section on Lyocell fiber production, the analytical techniques to monitor side reactions in the Lyocell system will be discussed. In the main part, the side reactions of NMMO in the Lyocell process have been divided into homolytic (radical) and heterolytic (non-radical) processes in a systematic investigation. In all homolytic reactions of NMMO, cleavage of the N–O bond with formation of an aminium (aminyl) radical is the first step. Formation, properties and subsequent reactions of this primary radical species will be summarized. In the absence of oxygen, the radical undergoes disproportionation or other redox processes that finally produce N -methylmorpholine, or morpholine and HCHO, respectively. In contrast, reactions of C-centered tautomers of the radical with dioxygen dominate in the presence of oxygen. Also the effects of transition metal ions, which are potent inducers of homolytic reactions of NMMO, are described. Heterolytic reactions in the Lyocell system proceed according to three major pathways. First, reductive deoxygenation of NMMO produces N -methylmorpholine with concomitant oxidation of available reductants, e.g. cellulose or carbohydrate model compounds. Second, Polonowski type reactions, which are intramolecular redox processes, finally generate morpholine and formaldehyde. In a third pathway, an autocatalytic process induced by carbonium–iminium ions can cause quantitative decomposition of NMMO. The formation and determination of reactive intermediates and heterolytic degradation products as well as their role in the system is analyzed. Furthermore, thermal degradation reactions under controlled conditions or under conditions leading to uncontrolled thermal degradation, i.e. explosions or ‘exothermic events’, are considered. Especially the latter processes are important from the viewpoint of system safety since they can be induced by several of the discussed radical and non-radical reactions. The homolytic, heterolytic and thermal degradation reactions in the system cellulose/NMMO/water have been reviewed in terms of reaction mechanisms, byproduct formation, and negative effects on the Lyocell system. Precise knowledge of reaction mechanisms as well as the role of harmful intermediates and products allows for the safe and economical production of Lyocell fibers, and a rational design of chemical stabilizers for the Lyocell system.

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420 citations


Journal ArticleDOI
Chia-Hung Kuo1, Cheng-Kang Lee1Institutions (1)
Abstract: Attempts were made to enhance cellulose saccharification by cellulase using cellulose dissolution as a pretreatment step. Four cellulose dissolution agents, NaOH/Urea solution, N-methylmorpholine-N-oxide (NMMO), ionic liquid (1-butyl-3-methylimidazolium chloride; [BMIM]Cl) and 85% phosphoric acid were employed to dissolve cotton cellulose. In comparison with conventional cellulose pretreatment processes, the dissolution pretreatments were operated under a milder condition with temperature

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242 citations


Journal ArticleDOI
Henri Chanzy1, A. Peguy1, S. Chaunis, P. MonzieInstitutions (1)
Abstract: Cellulose mesophases were obtained by preparing concentrated solutions of cellulose (20–55%) in a mixture of N-methyl-morpholine N-oxide (MMNO) and water. The anisotropy depends on four interconnected parameters: the temperature of the solution which, in general, must be lower than 90°C; the concentration of cellulose which must exceed 20%; a water content such that the mole ratio water/anhydrous MMNO is smaller than unity; and the degree of polymerization of the dissolved cellulose. The anisotropic cellulose solutions can readily be oriented during extrusion or casting thus giving fibers or films which upon regeneration exhibit high orientation.

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154 citations


Journal ArticleDOI
01 Sep 2002-Cellulose
Abstract: Efficient stabilization of cellulose solutions in NMMO(1) against side reactions and their harmful effects meansprevention of both homolytic and heterolytic side reactions, which is mainlyaccomplished by trapping radicals, formaldehyde, andN-(methylene)iminium ions (5). Whileradical trapping is commonly reflected by the antioxidativeefficiency, the effectivity against heterolyticdegradationin the Lyocell dope can be expressed by the newly introduced term‘formaldehyde trapping capacity’ (FTC). Propyl gallate (PG,4), the most widely applied Lyocell stabilizer nowadays, actsas a phenolic antioxidant, and is finally oxidized to a deeply colored, highlyconjugated chromophore (11) via ellagicacid (10). It was demonstrated that 4 is alsoa quencher of formaldehyde and N-(methylene)iminium ions,both in organic solutions of NMMO and in Lyocell dope. The processes of radicaltrapping and scavenging of HCHO/5 are competitive in the caseof propyl gallate. A novel oxa-chromanol derivative, PBD (14),was designed as stabilizer for Lyocell solutions. In analogy to propyl gallate,PBD acts as a scavenger of all three dangerous species, namely HCHO,5 and radicals. Upon oxidation by radical species, PBDreleasesacetaldehyde which acts as a very efficient HCHO trap. Thus, in contrast topropyl gallate, radical trapping and HCHO trapping are not competitive. Boththeantioxidative efficiency and the capacity to trap HCHO and 5are higher for PBD as compared to propyl gallate. In preliminary stabilizertesting, mixtures of PBD and PG proved to be especially effective.

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153 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20216
20206
20196
20185
20177
20164

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Topic's top 5 most impactful authors

Thomas Rosenau

19 papers, 928 citations

Antje Potthast

13 papers, 301 citations

Frank Wendler

10 papers, 186 citations

Valery G. Kulichikhin

9 papers, 45 citations

Frank Meister

9 papers, 153 citations