An expeditious solvent-free route to ionic liquids using microwaves

Varma, Rajender S.; Namboodiri, Vasudevan

doi:10.1039/b101375k

Cited by 272 publications

(161 citation statements)

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“…A clear, colorless, viscous solution was obtained. ILs are heated with exceptional efficiency by microwaves, 8 and care must be taken to avoid excessive heating that induces cellulose pyrolysis. The decomposition appears to be more rapid in contact with the ILs than for isolated cellulose under equivalent conditions.…”

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confidence: 99%

Dissolution of Cellose with Ionic Liquids

et al. 2002

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Cellulose is the most abundant biorenewable material, with a long and well-established technological base. 1 Derivitized products have many important applications in the fiber, paper, membrane, polymer, and paints industries.Cellulose consists of polydisperse linear glucose polymer chains ( Figure 1) which form hydrogen-bonded supramolecular structures; 2 cellulose is insoluble in water and most common organic liquids. The growing willingness to develop new cellulosic materials results from the fact that cellulose is a renewable resource, although many of the technologies currently used in cellulose processing are decidedly nongreen. 3 For example, viscose rayon is prepared from cellulose xanthate (production over 3,000,000 tons per year) utilizing carbon disulfide as both reagent and solvent. Most recently, processes using more environmentally acceptable nonderivitizing solvents (N-methylmorpholine-N-oxide (NMNO) and phosphoric acid) have been commercialized. Solvents are needed for dissolution that enable homogeneous phase reactions without prior derivitization. 4 Graenacher 5 first suggested in 1934 that molten N-ethylpyridinium chloride, in the presence of nitrogen-containing bases, could be used to dissolve cellulose; however, this seems to have been treated as a novelty of little practical value since the molten salt system was, at the time, somewhat esoteric and has a relatively high melting point (118°C). We were interested in examining whether other solvents that would now be described as ionic liquids (ILs) 6 would dissolve cellulose and, especially, whether the availability of a wide and varied range of ILs, coupled with the current understanding of their solvent properties, 7 would allow flexibility and control in the processing methodology, with increased solution efficiency and reduction or elimination of undesirable solvents.Ionic liquids, containing 1-butyl-3-methylimidazolium cations ([C 4 mim] + ) were screened with a range of anions, from small, hydrogen-bond acceptors (Cl -) to large, noncoordinating anions ([PF 6 ] -) also including Br -, SCN -, and [BF 4 ] -. In addition, variations in cation alkyl-substituent from butyl through octyl were investigated for the chloride salts. Dissolution experiments were carried out using cellulose-dissolving pulps (from cellulose acetate, lyocell, and rayon production lines), fibrous cellulose (Aldrich), and Whatman cellulose filter papers. The cellulose samples were added to the ionic liquids without pretreatment, in glass vials, and heated without agitation on a heating plate or in a domestic microwave oven. Table 1 summarizes the results obtained using high MW dissolving pulp (DP ≈ 1000). Stirring cellulose in the ILs under ambient conditions did not lead to dissolution, although the cellulose fibers were wetted by the ILs. However, on heating to 100-110°C , cellulose slowly dissolved in the Cl --, Br --, and SCN --containing ILs to yield increasingly viscous solutions.Dissolution rates could be significantly improved by heating in a microwave oven. ...

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Dissolution of Cellose with Ionic Liquids

et al. 2002

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“…[102][103][104][105][106] Development of non-haloaluminate ionic liquids over the past fifteen years has resulted in an explosion of research in these systems. [107][108][109][110][111][112][113][114][115][116][117] In particular, the application of these "new" ionic liquids in useful electrochemical reactions including the Kolbe oxidation, the reductive alkene coupling and carbonylation, and alkyl halide coupling, among others, is well illustrated in the literature. [118][119][120][121][122][123][124] Ionic liquids possess a variety of properties (low melting point, non-volatility, high ion density, high ion conductivity etc) that make them desirable as electrolytes for electrochemical devices and processes, solvents for organic and catalytic reactions, new material production, solvents for separation and extraction processes etc.…”

Section: Inorganic Synthesis In Ionic Liquidsmentioning

confidence: 99%

Electrochemical routes for industrial synthesis

Sequeira¹,

Santos²

2009

J. Braz. Chem. Soc.

112

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Esta revisão examina as razões que justificam um interesse crescente da indústria química pelos processos eletrolíticos. Reveem-se as indústrias químicas, nas quais compostos orgânicos e inorgânicos são processados e descrevem-se os avanços tecnológicos mais relevantes. Inicialmente, abordam-se processos bem estabelecidos, como as indústrias cloroalcalinas de produção de alumínio, p-aminofenol, adiponitrila, etileno glicol, antraquinona, produtos perfluorados, ácido glioxílico e L-cisteína. Face à grande quantidade de informação disponível, o assunto é tratado com base científica, mas de modo bastante simplificado. Posteriormente, descrevem-se processos orgânicos e inorgânicos emergentes, nomeadamente processos eletroquímicos mediados e síntese em líquidos iónicos. Estabelecem-se paralelos entre síntese química e síntese eletroquímica. Estimula-se o interesse nos processos de eletrossíntese, particularmente em líquidos iónicos, não desmerecendo a importância das vias puramente químicas de síntese orgânica e inorgânica.This review examines the reasons for increasing interest towards electrolyses by the chemical industry, reviews the electrochemical industries as most of them now exist, and provides a status report on the key technological advances which are occurring to meet present and future needs. Classical industries like those of chloroalkali, aluminium, p-aminophenol, adiponitrile, ethylene glycol, anthraquinone, perfluorinated products, glyoxylic acid and L-cysteine are initially covered. Considering the large amount of available publications in these topics of electrochemical engineering, the covered relevant information is treated at a scientific level, although in a simplified way. Then the paper deals with emerging inorganic and organic processes, e.g. electrosynthesis in ionic liquids and mediated electrochemical processes, and finishes by assessing what the future development trend might be given the electrochemical and non electrochemical competing influences. With this approach it is hoped to stimulate the interest of chemical engineers and scientists non-specialised in electrochemical routes, and to review some cutting edge research, particularly as far as electrosynthesis in ionic liquids is concerned.

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“…Nevertheless, the use of microwaves to perform the nucleophilic substitution can significantly reduce reaction time (Varma & Namboodiri, 2001a;Levêque et al, 2006). Alkyl triflates (Bonhôte et al, 1996) or tosylates (Karodia et al, 1998) may also be used.…”

Section: Fig 2 Typical Steps For the Ionic Liquid (Type N-alkylimidmentioning

confidence: 99%