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Swelling and dissolution of oil palm biomass in ionic liquids
Abstract
Malaysia is amongst the zvorld's fop producers of palm oil and the current plan fed area is around 4.5 million hectares. The palm oil industry generates vast amounts of palm biomass, especially emptyfruit bunches (EFB) (from the mills), oil palm fronds (OPF) and oil palm trunks (OPT) (during routine pruning and from the field during replanting). Oil palm biomass can be used efficiently after further treatment, either by physical or chemical means. In this study, the swelling and dissolution mechanisms of the lignocellulosic hiomass by ionic liquids were compared. There are five modes in describing the swelling and dissolution for cotton and wood cellulose fibre, and these were compared to the results obtained. Depending on the quality of the solvent, disintegration into rod-like fi'agments and hallooning,followed subsequently by dissolution were all observed among the oil palm fibre. In a typical dissolution trial, 5 wt % of oil palm biomass and cellulosefibre from EFB, OPF and OPT were treated with two different ionic liquids: 1-butyl-3-methylimidazolium chloride/dimethyl sulphoxide ([bmim]Cl)/DMSO and 1-ethyl-3-methylimidazolium chloride/dimethyl sulphoxide ([emim]Cl)/ DMSO at a ratio of 80:20 wt %. They were heated at different fixed times, namely 4, 6, 8, 16 and 24 hr for untreated oil palm biomass, and 1, 2 and 3 hr for cellulose fibre. The mechanisms of swelling and dissolution were monitored by optical microscopy.
... Using two different ionic solutions, Mohd Basyaruddin et al. [19] investigated the swelling and dissolving of OPB and cellulose fibre from OPEFB, OPF, and OPT. Mohtar et al. [20] extracted lignin from OPB, namely OPEFB, OPT and OPF, using an ionic liquid solution followed by precipitation with various precipitating agents such as CO2-AlK (SO4)2·12H2O precipitation. ...
... The OPEFB was typically burned in palm oil mill incinerator and recycled ash content as the plantation fertilizers. However, OPEFB incineration has been discouraged due to the environmental issue [2]. The waste of lignocellulosic biomass must be used to ensure environmentally sustainable oil palm industry. ...
Oil palm plantation generates massive amount of oil palm empty fruit bunch (OPEFB) which source great amount of cellulose. However, wrapping this cellulose is an adhesive compound called lignin. Biodelignification process was applied to remove lignin in pulp and paper industry. Therefore, this study is focused on optimum conditions of delignification process using a combination of bacteria from Rhynchophorus ferrugineus on OPEFB. The composition of chemicals was characterized according to the TAPPI standard method and Kursher-Hoffner method. The Box-Behnken design (BBD) was used to determine the optimum conditions of delignification process based on lignin loss of OPEFB. The optimized fiber was investigated based on mechanical properties according to TAPPI standard methods. From BBD analysis, the finest conditions for delignification were recognized to be at 35 °C in 48 h incubation time with 5 mL of 1% glucose for predicted value 54.3% compared to experimental value 52% of lignin loss as revealed by confirmatory study. The highest result of chemical analysis was recognized at run 12 (1.15%), 10 (12.35%), 4 (48.99%) and 5 (1.28%) for extractive, lignin, cellulose and ash content respectively. The tensile, burst and tear were identified as 9.93 Nm/g, 0.98 kPa.m 2 /g and 2.57 mN.m 2 /g respectively for handsheet product at optimum conditions. In conclusion, the results obtained was indicated that the delignification process via bacteria combination from R. ferrugineus is a viable alternative pulping process for pulp and paper-based industry. The delignification process on OPEFB also provides a cleaner technology process and more sustainable development for the country.
... An optimum 100% glucose recovery was obtained with pre-treatment conditions of 80°C, a 15 min retention time and 10% solid loading by employing a response surface methodology. Mohd Basyaruddin et al. (2012) investigated the application of two different ionic liquids; namely 1-butyl-3-methylimidazolium chloride/dimethyl sulphoxide and 1-ethyl-3-methylimidazolium chloride/dimethyl sulphoxide on the swelling and dissolution of OPB and cellulose fibre from OPEFB, OPF and OPT. These OPB fibres treated with ionic liquids showed homogeneous swelling without dissolution, whereas the cellulose fibre from these OPB has been attributed to the subsequent swelling and dissolution mechanisms of the fibre when subjected to the ionic liquids. ...
Oil palm biomass (OPB) is a by-product derived from the oil palm industry; periodically available in the field during the replanting and pruning activities; and from the milling processes of palm oil. The biomass includes oil palm trunk (OPT), oil palm frond (OPF), kernel shell, oil palm empty fruit bunch (OPEFB), oil palm mesocarp fibre (OPMF), and palm oil mill effluent (POME). OPB is classified as lignocellulosic residues that typically contain cellulose, hemicellulose, and lignin in their cell wall that can be converted into fine chemicals. These lignocellulosic chemicals have significant potential applications in food, chemicals and pharmaceuticals industries. A number of different types of extraction technologies have been developed; namely chemicals, physico-chemicals, biochemicals or the combinations of these processes. But as the methods that are environmental-friendly are the current trend, this article has its focus entirely on green technologies. This article comprehensively reviews the conversion of OPB into lignocellulosic chemicals with special attention on various extraction processes, followed by discussion on their special merits as well as their weaknesses. Sustainability for each of the process is also considered in detail in the discussion.
... The quality of ILs for wood and cellulose fibres can range from Mode 1 to Mode 4. 1-n-butyl-3-methylimidazolium chloride, C 4 mimCl showed the best media for cotton and wood fibre with disintegration of small fragments and dissolves in C 4 mimCl (Mode 1) [15]. 1-ethyl-3-methylimidazolium chloride, EmimCl and 1-butyl-3-methylimidazolium chloride, BmimCl shows swelling by ballooning with dissolution occurred for cellulose fibre (Mode 2) [16]. Whereas for OPT, OPF and EFB fibres, both ILs exhibited homogenous swelling without dissolution. ...
Pre-treatment is a crucial step in biomass processing prior to the hydrolysis or fermentation to bioethanol. Herein, the potential of deep eutectic solvent (DES) in the pretreatment of oil palm biomass were described. The mechanism of swelling and dissolution of oil palm trunk (OPT) was studied under optical microscopy. The OPT fibres were stirred and heated at 100 °C in choline chloride:glycerol (ChCl:Gly), choline chloride:ethylene glycol (ChCl:EG), ethylammonium chloride:glycerol (EAC:Gly) and ethylammonium chloride:ethylene glycol (EAC:EG) with 1:2 molar ratio each. All DESs tested had showed homogenous swelling and disintegration of small fragments interaction mode with OPT. There were more small fragments observed in EAC-based DES compared to ChCl-based DES. This finding supports the result for the percentage of dissolution where OPT in EAC-based DES recorded higher dissolution with 55% and 50% in EAC:EG and EAC:Gly respectively whereas ChCl-based DES recorded only 33% and 29% in ChCl:EG and ChCl:Gly, respectively. In ChCl-based DESs the fragmentations were accompanied by large unswollen section of fibres. The formation of small fragments indicates that the fibres experienced a fast dissolution. Therefore, the EAC-based DESs proved to be a better swelling and dissolution media for oil palm biomass pretreatment compared to ChCl-based DES. © 2017, Malaysian Society of Analytical Sciences. All rights reserved.
... Reduction in fiber length for all the oil palm biomass sources was probably a result of holocellulose solubilization by ILs. The solubilization of fibers and their modes of interaction have been previously examined (Cuissinat and Navard 2006a,b;Rahman et al. 2012). ...
Ionic liquids (ILs) were used in the dissolution of oil palm biomass, primarily empty fruit bunches (EFB), oil palm fronds (OPF), and oil palm trunks (OPT). These ILs acted as alternative solvents that could dissolve biopolymer molecules up to 5 wt.%. The IL, [emim][OAc] was the best solvent, dissolving EFB, OPF, and OPT of 99%, 100%, and 97%, respectively, at 100 °C and 16 h. The lignin content of the regenerated oil palm solids for all biomass was quantified and showed significant reduction up to 35%; fiber length was also reduced as the heating time increased after IL dissolution. Also, the effect of ILs on the different parts of oil palm biomass fibers was thoroughly studied. The lignin content was quantified.
... acting as 'glue' that binds tightly to cellulose and hemicelluloses (Chandra et al 2007). Hence, it is suggested that a more harsh condition should be applied to remove lignin. However, Hamzah et al. (2009) was able to remove lignin content in oil palm empty fruit bunch (OPEFB) to as low as 7.56g/100g by using microwave-alkali heating pretreatment. Rahman et al. (2012) claimed that the difference in the amounts removed may be attributed to the different proportions components in the fibre which depends on nature and age of plant, source of fibre and the extraction conditions used to obtain fibre. ...
The Klason's lignin content in Elaeis guineensis or oil palm trunk (OPT) was intensively investigated in this study. The Microwave-Alkali (Mw-A) pretreatment experiment was designed using Design Expert 7.0 software. The design of experiment (DOE) for this research was established and conducted based on two-level factorial design with a total of eleven runs which included three centre points. All the run order was randomly performed without blocks. The studied variables or factors (parameters) such as temperature, heating duration and microwave power were denoted by high level (+1) and low level (-1) where their actual code i.e. 80-90°C, 40-80 min and 500-900 watt, respectively. Prior to Mw-A treatment, the oil palm trunk biomass with less than 1.0 mm (mesh size < No.18) were first presoaked in 2.5 molL -1 sodium hydroxide solution in the ratio of 1:10. The amount of lignin present in the washed and dried filtrate samples was subsequently determined. In this case, the total content of lignin determined for untreated and microwave-alkali treated were 17.87 and 13.87 (g/100g biomass), respectively. In addition, the obtained data from DOE were fitted into the response, viz. amount of lignin, YL for statistical analysis. Lignin response was found to be significant in terms of model (F-value = 20.35), the regression coefficient, R 2 = 0.9862 and adjusted regression coefficient RA 2 = 0.9377. The investigation revealed that the lignin content of oil palm trunk under Mw-A pretreatment can be modelled and as much as 22.38% reduction of lignin was attained when the microwave experiment was set at 100°C, 80 min and 900 watt.
This paper presents an overview of bio-refinery concept in Malaysia emphasing on diversifying and maximizing the value of palm oil biomass feedstock to produce bio-based chemicals that demonstrated strong market growth. The oil palm mills and plantations contributes to large amounts of biomasss such as oil palm fronds (OPF), oil palm trunks (OPT) and empty fruit bunches (EFB) which are sources of renewable energy. A majority of these lignocellulosic palm oil byproducts are not effectively utilized and some parts of the biomass are utilized as biofertilizers and solid biofuels. Thus, the potential of palm oil biomass should be explored by diversifying the consumption of these biomass to produce high value added chemicals and biofuels which can generate additional revenue for the country. A number of technologies; namely biochemical conversion, pyrolysis etc. have been established to convert such biomass into a wide spectrum of biobased commodities such as biodiesel, succinic acid, lactic acid, bioethanol and polyhydroxyalkanoates (PHA). This article comprehensively reviews the potential of high value added products generated from palm oil biomass via different bio-refinery approach with special attention on the biochemical conversion process followed by their development stage towards full commercial scale. Limitations and challenges in each process were also discussed in detail.
Biochar produced from oil palm biomass has been demonstrated to be effectively utilized in energy, soil amendment, wastewater treatment, catalyst and composting applications. However, the industrial development of biochar plants for specific biomass requires an adequate description of the pyrolysis process of the feedstock. Knowledge of biomass devolatilization characteristics and kinetics may describe the pyrolysis process adequately, which would be needed for the proper industrial process design and optimization. Therefore, in this review, the thermal degradation characteristics and pyrolysis kinetics of oil palm biomass residues are discussed to reveal important influential factors and pyrolysis reaction mechanisms. The findings from the literature indicate that the main devolatilization temperature range and the overall reactivity are 352 to 380°C and 0.360 mg min-1°C-1 for kernel shell, 336 to 360°C and 0.270 mg min-1°C-1 for mesocarp fiber, and 329 to 356°C and 0.530 mg min-1°C-1 for empty fruit bunch. The kinetic parameters for the consecutive reactions model suggest that the ease to commence pyrolysis reaction was in the following order: frond < kernel shell < mesocarp fiber < empty fruit bunch. The percentage biochar yield for the residues was higher than 23 wt.% under slow pyrolysis conditions and the tendency of obtaining high biochar yield followed this order: kernel shell > mesocarp fiber > empty fruit bunch > trunk > frond. The tendency for high biochar yield could be attributed to the proportion of lignin content which slowly decomposes over a wide temperature range. The treatment temperatures of 400, 500, and 600°C are adequate to carbonize the oil palm biomass residues for producing biochars suitable for use as biofuels, activated carbon, and reducing agent, respectively.
Michael addition reactions of n-pentanal with ß-nitrostyrene in achiral and chiral ionic liquids catalyzed by l-proline were studied. Results indicate anion plays an important role as weak coordination properties in the reactivity and stereoselectivity towards Michael product. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][NTf2]) ionic liquid was found to be the best solvent media with a high yield (up to 90%) and a high diastereomeric ratio (syn/anti: 91/9), with moderate enantioselectivity (38% ee) among ten ionic liquids tested. The ionic liquid has been reusable over five numbers of cycles.
The depletion of fossil fuels and natural
raw materials has encouraged the
search for the development of new
resource materials for the production of
bio-based materials (Alekhina et al., 2014).
Oil palm biomass (OPB) is classified as
lignocellulosic residues that comprised
mainly of cellulose, hemicellulose, and
lignin in their cell walls (Raveendran et
al., 1995). This lignocellulosic material can
be converted into valuable feedstock for
the production of biosugar, biocompost,
biochemical and bioethanol. Due to the
lignocellulosic nature of OPB, countless
research and development activities
were undertaken by various agencies
in order to improve the transformation
of OPB into more valuable substrate for
producing a variety of chemicals that will
have huge potential in food, chemical and
pharmaceutical industries. The chemical
constituents in OPB varied considerably due
to their diverse origins and types (Chew and
Bhatia, 2008). The chemical composition of
different OPB is shown in Table 1.
In this article, we described fabrication of regenerated cellulose (RC) films derived from oil palm empty fruit bunch-microcrystalline cellulose (OPEFB-MCC) via ionic liquid 1-butyl-3-methylimidazolium chloride [BMIM][Cl]. The properties of RC films as a function of varied dissolution temperature; 75, 80 and 85 °C were unraveled by means of their water vapor permeability, light opacity, mechanical performance, thermal characteristic and morphology. It was shown that when dissolution temperature was increased, the barrier properties of RC films were enhanced as indicated by increment of opacity values (1.44–1.63) but decline of water vapor permeability values (0.95–1.30 × 10⁻¹⁰ g s⁻¹ m⁻¹ Pa⁻¹). We also observed an improvement in thermal stability of RC films as shown by the increase of their degradation temperatures; T20 = 264–266 °C and Tmax = 273–281 °C. However, the films’ mechanical performances denoted by TS and EAB values were slightly diminished with percentage reduction of 21.7% and 5.2%, respectively. Meanwhile, the films exhibited Tg without Tm, reflecting their highly amorphous structure after regeneration. Microstructural analyses of the films depicted uniform distribution of cellulose fragments on their cross-sectional surfaces thus indicated excellent dissolution of cellulose in the solvent.
Deep eutectic solvents (DES) were utilised as pretreatment media on oil palm trunk (OPT) fibre in order to change the morphology of the highly crystalline cellulose prior to enzymatic hydrolysis. Among all the DESs tested, ethylammonium chloride: ethylene glycol (EAC:EG) was found to be the most efficient solvent for the pretreatment of OPT fibre. The pretreatment of OPT by EAC:EG had removed 42% lignin and 83% hemicellulose with the ability to dissolve the OPT biomass (58%) after heating at 100 °C for 48 h. FTIR analysis was used in determining the chemical characteristic changes where OPT treated in EAC:EG had more disruption of hydroxyl bond and indication of delignification compared to OPT treated with other DESs. Enzymatic hydrolysis was carried out on OPT treated in EAC:EG and the highest glucose production (74%) was achieved at 50 °C after 24 h with 15 mg/mL substrate concentration, 50 FPU/g of Celluclast 1.5 L and 100 CBU/ml of Novozyme 188.
Oil palm empty fruit bunch (EFB) fibers were subjected to solvolytic liquefaction to convert into liquid products using ethylene glycol (EG) as a supporting agent. The process was carried out at 250°C for 60 min. The water-insoluble product fraction was exhaustively extracted with acetone (ASL fraction) to separate all less polar. FTIR and comparative analytical pyrolysis GC/MS of the parent EFB fiber and the ASL fraction confirmed the formation of larger amounts of long-chain lipophilic compounds under liquefaction conditions. Furthermore, a considerable amount of less polar thermal lignin degradation products were obtained comprising all of the three main lignin building blocks, i.e. 4-hydroxyphenyl-(P units), 4-hydroxy-3-methoxyphenyl-(G units) and 3,5-dimethoxy-4-hydroxyphenyl (S units) substituted compounds. 4-Prop-2-en-1-yl substituted phenolic compounds contributed mostly to the cumulated peak area of all lignin derived pyrolysis products obtained by analytical Curie point pyrolysis GC/MS at 600C. The results of both instrumental-analytical methods confirm the formation of phenol and its derivatives, furan derivatives, organic acids, hydrocarbon, ester, benzene groups and alcohols.
The potential for performing cellulase-catalyzed reactions on cellulose dissolved in 1-butyl-3-methylimidazolium chloride ([bmim]Cl) has been investigated. We have carried out a systematic study on the irreversible solvent and ionic strength-induced inactivation and unfolding of cellulase from Trichoderma reesei
(E.C. #3.2.1.4). Experiments, varying both cellulase and IL solvent concentrations, have indicated that [bmim]Cl, and several other ILs, as well as dimethylacetamide–LiCl (a well-known solvent system for cellulose), inactivate cellulase under these conditions. Despite cellulase inactivity, results obtained from this study led to valuable insights into the requirements necessary for enzyme activity in IL systems. Enzyme stability was determined during urea, NaCl, and [bmim]Cl-induced denaturation observed through fluorescence spectroscopy. Protein stability of a PEG-supported cellulase in [bmim]Cl solution was investigated and increased stability/activity of the PEG-supported cellulase in both the [bmim]Cl and citrate buffer solutions were detected.
This study examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin. Dissolution experiments were carried out employing lignin isolated from pine kraft pulp. Up to 20 wt% lignin could be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][MeSO4]. For the [bmim]‐containing ionic liquids, the order of lignin solubility for varying anions was: [MeSO4]>Cl∼Br⋙[PF6], indicating that the solubility of lignin was principally influenced by the nature of the anions. Ionic liquids containing large, non‐coordinating anions [PF4] and [PF6] were unsuitable as a solvent for lignin. C nuclear magnetic resonance (NMR) analyses of lignin and model compounds showed that C signals using ionic liquid as a solvent were shifted up‐field by δ 0.1 to 1.9 ppm in comparison to C NMR data acquired using dimethyl sulfoxide (DMSO) as the solvent.
Important cellulose solvents are described based on the systematization of derivatizing and non-derivatizing solvents. Advances and limitations of the homogeneous phase chemistry of the biopolymer will be discussed based on new results considering adequately own research work in the field.
Dissolution of cellulose with ionic liquids allows the comprehensive utilization of cellulose by combining two major green chemistry principles: using environmentally preferable solvents and bio-renewable feed-stocks. In this paper, the dissolution of cellulose with ionic liquids and its application were reviewed. Cellulose can be dissolved, without derivation, in some hydrophilic ionic liquids, such as 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-allyl-3-methylimidazolium chloride (AMIMCl). Microwave heating significantly accelerates the dissolution process. Cellulose can be easily regenerated from its ionic liquid solutions by addition of water, ethanol or acetone. After its regeneration, the ionic liquids can be recovered and reused. Fractionation of lignocellulosic materials and preparation of cellulose derivatives and composites are two of its typical applications. Although some basic studies, such as economical syntheses of ionic liquids and studies of ionic liquid toxicology, are still much needed, commercialization of these processes has made great progress in recent years.
The bulk of the cellulose currently employed by industry is isolated from wood through Kraft pulping, a process which traditionally involves a barrage of environmentally detrimental chemicals and is undeniably 'non-green.' In this report we present a simple and novel alternative approach for the processing of lignocellulosic materials that relies on their solubility in solvent systems based on the ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C 4 mim]Cl). Dissolution profiles for woods of different hardness are presented, making emphasis on the direct analysis of the cellulosic material and lignin content in the resulting liquors by means of conventional 13 C NMR techniques. We also show that cellulose can be readily reconstituted from the IL-based wood liquors in fair yields by the addition of a variety of precipitating solvents. Spectroscopic and thermogravimetric studies indicate that the polysaccharide obtained in this manner is virtually free of lignin and hemicellulose and has characteristics that are comparable to those of pure cellulose samples subjected to similar processing conditions.
An efficient solventless protocol for the preparation of a wide variety of ionic liq-uids is described, which requires a simple exposure of admixed 1-methylimidazole and alkyl halides to microwave irradiation in open glass containers. The details of this clean process using a common household microwave oven, which exploits the newer inverter technology system for better power attenuation, are described. The characterization and thermal stabili-ty data on selected ionic liquids and their potential applications are summarized.
Softwood acetic acid lignin (S-AL), obtained by aqueous acetic acid pulping of todomatsu (Abies sachalinensis Masters), is infusible. In this study, a method for conversion of S-AL to a fusible material for the preparation of lignin fibers was developed based on examination of the relationship between the thermal properties and the chemical structure of S-AL. S-AL was found to be converted to fusible material by removal of the high-molecular-mass fraction by solvent extraction with 70% acetic acid, with a yield of 80%. From a comparison of the chemical structure of the fusible and infusible fractions, we found that the structures of aromatic nuclei in the acetic acid lignin (AL), such as condensed and aryl-ether structures, were related closely to the thermal mobility of AL. The large contents of condensed and aryl-ether structures in AL seemed likely to hinder thermal motion. Therefore, the cutting of aryl-ether bonds by re-cooking with aqueous acetic acid resulted in a fusible lignin, with a yield of approximately 90%. The fusible fraction of S-AL and the re-cooked S-AL were capable of being spun by fusion spinning.
Alkaline peroxide extraction is an environmentally friendly pulping process allowing the recovery of valuable hemicelluloses and lignin products. Extraction of the dewaxed wheat straw with 2% H2O2 % NaOH aqueous solution for 5 h at 45 and 50° resulted in a dissolution of 85% and 86% of the original lignin, 75% and 76% of the original hemicelluloses, respectively, and left 53.8% and 53.3% residues with light chromatophore. which are very suitable for paper-making, in comparison with other pulps. The two alkaline lignin fractions, two hemicellulosic preparations and the corresponding residues (mainly cellulose) were characterized by both degraded methods, alkaline nitrobenzene oxidation and acid hydrolysis, and non-destructive techniques, Ultraviolet (UV), Fourier transform infrared (FT-IR), hydrogen-1 and carbon-13 Nuclear magnetic resonance spectroscopes (1H and 13C-NMR) as well as Gel permeation chromatography (GPC).
Activated carbon fibers (ACF's) were prepared from acetic acid lignin-based carbon fibers by steam activation. The ACF had excellent properties, such as more rapid adsorption rate and higher iodine and methylene blue adsorption capacities, as compared to a commercially available activated carbon. The adsorption mechanism of ACF was quite different from that of activated carbon (AC), as supported by the micropore distribution profiles.
The stress relaxation in phenol-formaldehyde composites reinforced with short oil-palm empty fruit bunch fibres has been studied as a function of fibre loading, fibre treatment, physical ageing and strain level. Maximum stress relaxation was observed for 30 wt.% fibre loading. Treated composites showed higher relaxation except in composites treated with alkali and toluene 2, 4 diisocyanate (TDI). Water ageing increased the rate of relaxation. The effect of hybridisation of the oil-palm fibres with glass fibres on the relaxation behaviour was examined. The stress-relaxation rate of the composite was lowered upon hybridisation. The rate of relaxation for different time intervals and crossover time was calculated in order to explain the relaxation mode of the composites. Master stress-relaxation curves were drawn to explain the long-term behaviour of the composites by superimposing the stress values at different strains by a horizontal shift along the logarithmic time axis. The relaxation modulus values for the composite show a trend similar to that of relaxation of stress in the composites.
A novel dissolving process for chitin and chitosan has been developed by using the ionic liquid 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) as a solvent, and a novel application of chitin and chitosan as substitutes for amino-functionalized synthetic polymers for capturing and releasing CO2 has also been exploited based on this processing strategy.
1-Butyl-3-methylimidazolium chloride ionic liquid has been developed for the dissolution and regeneration of wool keratin fibers, which can be used to prepare wool keratin/cellulose blended materials directly.
A new and highly efficient direct solvent, 1-allyl-3-methylimidazolium chloride (AMIMCl), has been used for the dissolution and regeneration of cellulose. The cellulose samples without any pretreatment were readily dissolved in AMIMCl. The regenerated cellulose materials prepared by coagulation in water exhibited a good mechanical property. Because of its thermostable and nonvolatile nature, AMIMCl was easily recycled. Therefore, a novel and nonpolluting process for the manufacture of regenerated cellulose materials using AMIMCl has been developed in this work.
This review paper gives an overview of synthesis paths recently studied for the preparation of unconventional, i.e. not commercially produced, cellulose derivatives with alternative functional groups and patterns of functionalization. A classification of solvents that can be applied as medium for homogeneous reactions is given and the different types of solvents, namely both aqueous and non-aqueous non-derivatizing and derivatizing ones, are evaluated. Carbonic and sulfonic acid esters of the polymer, deoxycellulose derivatives, ionic and non-ionic ethers of cellulose as well as silylated cellulosics are included. Moreover, exotic products, e.g. hydrophobically-modified water-soluble as well as regioselectively functionalized cellulosics are critically reviewed. Among the synthesis pathways discussed are conversions in homogeneous phase using different aqueous and non-aqueous solvents, the reaction via organo-soluble intermediates, the functionalization of cellulose in reactive microstructure obtained by induced phase separation and by applying a certain degree of accessibility as well as protecting group technique with cellulose. A number of new synthesis tools for the derivatization of cellulose are reviewed, e.g. new in situ activating agents for cellulose esterification like N,N-dicyclohexylcarbodiimide, N,N-carbonyldiimidazole and p-toluenesulfonyl chloride. Furthermore, nucleophilic displacement reactions, offering the possibility to design advanced cellulose materials by reactions at the C-atoms, as well as oxidation reactions are described. Selected methods appropriate for structure analysis of cellulose derivatives both on the level of the repeating unit and along the polymer chain are briefly reviewed. Emphasis is placed on the application of NMR spectroscopy including two-dimensional methods and of chromatographic techniques after specific sample pretreatment as enzymatic and acidic partial or complete depolymerization. Some comments on structure–property relationships of the cellulose derivatives are also given.
The recycling behavior of sawdust, both hardwood and softwood, filled polystyrene composites was observed by measuring the mechanical properties and dimensional stability under normal conditions (room temperature) as well as extreme ones (e.g., exposure to water at room temperature and boiling temperature, and to heat at +105°C and −20°C). Mechanical properties and dimensional stability of the original and recycled composites—that is, nontreated and treated ones (e.g., 3% isocyanate, coated fiber-filled and grafted fiber-filled)—are compared under all extreme conditions. the behavior of the recycled composites did not change significantly. Furthermore, treated wood fiber-filled thermoplastic composites offered superior mechanical properties and dimensional stability under all extreme conditions, even after recycling.
Semi-interpenetrating networks (SIPNs) of poly(N,N-dimethylacrylamide) (DMAm) containing cellulose or chitin were prepared in 9%LiCl/N,N-dimethylacetamide (DMAc) as the homogeneous reaction medium. N,N-Methylenebisacrylamide (MBAm) was utilized as the cross-linking agent with 2,2‘-azobisisobutyronitrile (AIBN) as the initiator. The respective SIPNs contained 25, 12, and 6 wt % cellulose or 6 wt % chitin. A control DMAm hydrogel (without polysaccharide) was also synthesized in 9%LiCl/DMAc. The 25 wt % cellulose DMAm SIPN was found to be unique, differing from the other compositions prepared, possessing a 6-fold higher modulus than the DMAm control. The enhancement in mechanical stiffness was attributed to intimate molecular interactions and complexation between cellulose and DMAm. The presence of the extended cellulose chains within the DMAm matrix creates a more open network in the nonsolvated state as reflected in DSC and fluorescence experiments. It is this molecular level interaction of cellulose with DMAm that enhances the physical properties in the first SIPN composite to utilize unmodified cellulose and chitin. In the solvated state, the microdispersed polysaccharide hydrogen bonds with the DMAm matrix increases the rigidity of the network yet allows reversible hydration as reflected in rheology, equilibrium swelling, and fluorescence experiments.
An all-cellulose composite, in which both the fibers and the matrix are cellulose, was prepared by distinguishing the solubility of the matrix cellulose into the solvent from that of the fibers through pretreatment. The structure, mechanical, and thermal properties of this composite were investigated using an X-ray diffraction, a scanning electron microscope, a tensile test, and dynamic viscoelastic and thermomechanical analyses. The tensile strength of uniaxially reinforced all-cellulose composite was 480 MPa at 25 °C, and the dynamic storage modulus was as high as 20 GPa at 300 °C. These were comparable or even higher than those of conventional glass-fiber-reinforced composites. In addition, a linear thermal expansion coefficient was about 10-7 K-1. This all-cellulose composite shows substantial advantages, that is, it is composed of sustainable resources, there is less interface between the fiber and the matrix, it possesses excellent mechanical and thermal performance during use, and it is biodegradable after the service.
Reactivity of cellulose hydroxyl functional groups to strained-ring systems was examined in the lithium chloride/N,N-dimethylacetamide solvent. Epoxide reagents were unreactive to cellulose hydroxyl groups in nucleophilic ring-opening reactions. Cyclic anhydrides and lactones readily reacted in the presence of triethylamine, while 1,3-propane sultone reacted with the competing chloride anion in the DMAc/ LiCl solvent. ∈-Caprolactone reacted with cellulose to form a hydroxy-terminal ester derivative by an addition-elimination mechanism. A novel cyclic iminium chloride cellulose derivative and subsequent hydrolysis products were prepared.
Light scattering and viscosity measurements on diluted and moderately concentrated solutions of several cellulose samples dissolved in N,N-dimethylacetamide (DMAc) containing 5% or 7.8% (w/w) LiCl are reported. Cellulose samples include regenerated cellulose, sulfate pulps, and HCl hydrolyzates having DP between 60 and 760. Solubilization without chain degradation was achieved by using a method reported in the patent literature involving activation of cellulose by DMAc at the reflux temperature followed by addition of LiCl. Cellulose was dissolved either as a molecular dispersion (I) or as stable aggregates (II) consisting of ca. 7 fully extended cellulose molecules with a side-by-side organization. Concentration-dependent association equilibria (III) involving single molecules or aggregates were also observed. The occurrence of said situations depends upon the concentration, Cp, of stock solutions prepared with the method indicated above, the concentration, c, to which stock solutions are diluted, the LiCl concentration, the DP, and the treatment performed by the producer. In particular, acid hydrolysis favors situation II. This complex situation is considered in the accompanying paper in order to establish a relationship between the size of polymer particles and the critical concentration for mesophase formation.
Cellulose acetoacetates with and without other ester groups were prepared directly from cellulose by reaction with diketene or tert-butyl acetoacetate (and, where appropriate, a carboxylic anhydride) in N,N-dimethylacetamide (DMAC)/LiCl or 1-methyl-2-pyrrolidinone (NMP)/LiCl solution. This is the only method yet described for the direct synthesis of these polymers from cellulose and, except for the triester, the only method available for synthesis of cellulose acetoacetates which do not contain another ester group. The products span the entire degree of substitution (DS) range, are amorphous, and are readily soluble in various solvents depending on DS. Cellulose acetoacetates of low DS are soluble in water. Some of these water-soluble materials can be formulated into cross-linkable coatings which have outstanding solvent resistance. Methods have been developed for the determination of DS by proton NMR spectroscopy. Proton and carbon-13 NMR resonance assignments for cellulose tris(acetoacetate) are also provided.
A room temperature ionic liquid (RTIL), that is, 1-butyl-3-methylimidazolium acetate (BminAc), is proposed to be a new good solvent for native chitins with different origins and molecular weights. A water and a methanol coagulant were used to regenerate the dissolved chitins and chitin materials with a variety of structures were prepared. Wide-angle X-ray diffraction (WAXD), Fourier transform IR (FTIR), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to visualize the modifications of the native structures of chitin during the dissolution and the regeneration processes, as well as the morphological features and properties of the reconstituted chitin materials.
The dissolution behaviour of cellulose in low temperature molten salts was investigated. Depending on the chosen anions in the melt, cellulose shows different reaction behaviour in different Li+‐containing melts. Dissolution of the polymer was observed in molten LiClO4ċ3H2O and molten LiIċ2H2O. In the hydrated melts of LiCH3COOċ2H2O and LiNO3ċ3H2O a fine distribution of cellulose was stated. Cellulose can be regenerated by cooling the melt and removing the salt by dissolution in water.
The structure of the recrystallized product is determined by the used low temperature molten salt.
A coarse thermomechanical Asplund pulp was prepared from Norway spruce (Picea abies). The pulp was delignified to different degrees using acidified sodium chlorite. The swelling behavior (measured as water retention value=WRV) of the resulting pulps was studied under various chemical conditions (pH and conc. of NaCl). It is shown that chlorite-delignified pulps have an appreciable polyelectrolytic character. Whereas the WRV of an Asplund pulp does not respond to changes in the chemical environment, the delignified pulp has a WRV of 155 at pH 3 and 250 at pH 9. Compared under the same chemical conditions, the WRV increases with increasing degree of delignification (70%).
Biopolymers such as starch and zein protein were found to be soluble at 80 °C in ionic liquids such as 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-butyl-3-methylimidazolium dicyanamide (BMIMdca) in concentrations up to 10% (w/w). Higher concentrations of biopolymers in these novel solvents resulted in solutions with too high viscosity to stir. Solutions of both starch and zein in BMIMCl were acylated with anhydrides in presence of pyridine to give acetyl starch and benzoyl zein with various degrees of substitution. Without pyridine the acylation reaction did not proceed. 1H NMR and IR spectroscopies were used to determine the degree of substitution of starch. Viscosity studies indicated that the starch underwent slight reduction in molecular weight during the course of acylation. Starch was also soluble in other non-conventional solvents such as choline chloride/oxalic acid and choline chloride/ZnCl2. However, zein was insoluble in these solvents.
We report here initial results that demonstrate that cellulose can be dissolved without activation or pretreatment in, and regenerated from, 1-butyl-3-methylimidazolium chloride and other hydrophilic ionic liquids. This may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this important bioresource.
The kinetics of the acid-catalysed hydrolysis of cellobiose in the ionic liquid 1-ethyl-3-methylimidazolium chloride, [C(2)mim]Cl, was studied as a model for general lignocellulosic biomass hydrolysis in ionic liquid systems. The results show that the rate of the two competing reactions, polysaccharide hydrolysis and sugar decomposition, vary with acid strength, and that for acids with an aqueous pK(a) below approximately zero, the hydrolysis reaction is significantly faster than the degradation of glucose, thus allowing hydrolysis to be performed with a high selectivity in glucose. In tests with soluble cellulose, hemicellulose (xylan), and lignocellulosic biomass (Miscanthus grass), comparable hydrolysis rates were observed with bond scission occurring randomly along the biopolymer chains, in contrast to end-group hydrolysis observed with aqueous acids.
Five modes describing the behaviour of cellulose fibres dipped in a chemical have been identified:
Mode 1: Fast dissolution by disintegration into fragments
Mode 2: Large swelling by ballooning, and dissolution
Mode 3: Large swelling by ballooning, and no dissolution
Mode 4: Homogeneous swelling, and no dissolution
Mode 5: No swelling and no dissolution
In the case of the behaviour of wood and cotton cellulose fibres in N-methylmorpholine-N-oxide (NMMO) and water mixtures, four domains of water content have been identified. Below 17% of water up to monohydrate (13%), the fibres are disintegrated into rod-like fragments and dissolve (mode 1). In NMMO – water mixtures containing 19–24% water, the cellulose fibres exhibit a heterogeneous swelling by forming balloons (composed of dissolved cellulose holds inside a membrane) separated with non-swollen sections. The whole fibre will completely dissolve (mode 2) in four successive steps (growth of the balloons, burst of the balloons, dissolution of the non-swollen sections and finally dissolution of the membrane). With still greater water contents (25–30%), only the ballooning phenomenon is observed, with a partial dissolution inside the balloon (mode 3). Above 35% of water, the fibres swell homogeneously and are not dissolving (mode 4).
The swelling and dissolution mechanisms of native cotton and wood cellulose fibres in NaOH-water are studied. The cellulose fibres exhibit a heterogeneous swelling by ballooning in the best dissolving conditions (-5 degrees C, 7.6% of NaOH). This corresponds to the mode 3 of the swelling-dissolution (see companion paper). in this region of the mixture phase diagram, cellulose is only dissolved inside the balloons. A lot of insoluble parts are present. Increasing the temperature and/or the content of NaOH decreases the quality of the solvent. in this case, the cellulose fibres do not show ballooning, but only a homogeneous swelling (mode 4). Three components are tested as additives: urea, zinc oxide and N-methylmorpholineN-oxide (NMMO). The swelling and dissolution mechanisms in NaOH-water and NaOH-water-additives stay the same. Adding urea to NaOH-water (-5 degrees C, 7.6% of NaOH) gives the same ballooning mechanisms, but with a larger expansion of the balloons, indicating that the solvent is better. Zinc oxide does not increase the expansion of the balloons, but the kinetics of swelling is faster. NMMO acts as a dissolution inhibitor
The miscibility behavior of cellulose (CELL) with poly(4-vinylpyridine) (P4VPy) was compared to that of the methylolcellulose/P4VPy pair (MC/P4VPy). The homopolymers and their blends were characterized by dynamic mechanical analysis (DMA), CP-MAS NMR spectroscopy, and proton spin-lattice relaxation measurements in the rotating frame (T1-rho). By fitting the T(g) data for the two series of blends to T(g)-composition models proposed by Gordon and Taylor and by Jenckel and Heusch, it is shown that the relative strength of the interactions in the CELL/P4VPy pair is higher than that in the MC/P4VPy pair; this is confirmed by CP-MAS NMR spectroscopy. The combined results obtained by DMA and proton T1-rho measurements show that MC and P4VPy are miscible on a scale between 2.5 and 15 nm, while the CELL/P4VPy pair is probably miscible on a scale of 2.5 nm.
Room-temperature ionic liquids (RTILs) are useful in many chemical applications. Recent publications have attempted to determine the polarity of RTILs using empirical solvent polarity scales. The results have indicated that most RTILs have similar polarities. Nevertheless, RTILs are capable of behaving quite differently when used as solvents in organic synthesis, matrixes in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, liquid-liquid extraction, and as stationary phases in gas chromatography. The work presented in this study uses a linear free energy approach to characterize 17 RTILs on the basis of their distinct multiple solvation interactions with probe solute molecules. This model provides data that can be used to help identify the interactions and properties that are important for specific chemical applications.
In this work, the suitability of imidazolium-based ionic liquid solvents is investigated for the dissolution and regeneration of silkworm (Bombyx mori) silk. Within an ionic liquid the anion plays a larger role in dictating the ultimate solubility of the silk. The dissolution of the silk in the ionic liquid is confirmed using wide-angle X-ray scattering. The dissolved silk is also processed into 100 mum-thick, two-dimensional films, and the structure of these films is examined. The rinse solvent, acetonitrile or methanol, has a profound impact on both the topography of the films and the secondary structure of the silk protein. The image depicts a silkworm cocoon dissolved in 1-butyl-3-methylimidazolium chloride and then regenerated as a film with birefringence.
The application of different ionic liquids (IL), namely 1-N-butyl-3-methylimidazolium chloride ([C(4)mim](+)Cl(-)), 3-methyl-N-butyl-pyridinium chloride and benzyldimethyl(tetradecyl)ammonium chloride were investigated as solvents for cellulose. The ILs used have the ability to dissolve cellulose with a degree of polymerization in the range from 290 to 1 200 to a very high concentration. Using [C(4)mim](+)Cl(-), no degradation of the polymer appears. By (13)C NMR measurement it was confirmed that this IL is a so-called non-derivatizing solvent. [C(4)mim](+)Cl(-) can be applied as a reaction medium for the synthesis of carboxymethyl cellulose and cellulose acetate. Without using any catalyst, cellulose derivatives with high degree of substitution could be prepared.(13)C NMR spectrum of cellulose dissolved in the IL [C(4)mim](+)Cl(-) (top). The (13)C NMR spectrum of cellulose dissolved in DMSO/tetrabutylammonium fluoride trihydrate is shown for comparison (bottom).
Solution properties and molecular structure of tunicate cellulose (TC), an animal cellulose from Halocynthia roretzi, were investigated in terms of rheological and dilute solution properties. The solvent used is 8 wt % LiCl/1,3-dimethyl-2-imidazolidinone (DMI). A solution of dissolving pulp (DP), derived from plant, was also used for comparison. The weight-average molecular weight, Mw, and the limiting viscosity number, [eta], of the TC were evaluated to be 413 x 10(6) and 2645 mL/g, respectively. The TC solution showed the same concentration dependence of GN (GN=5.49 x 10(6)phiw(2.1)4 Pa; phiw: weight fraction of cellulose in solution; GN: plateau modulus) as the DP solution and, moreover, also as the solution of cotton linter (CC) in 8 wt % LiCl/N,N-dimethylacetamide (DMAc). This exponent of 2.1(4) indicates that network structure by entanglements was formed in these solutions. According to the theory of Fetters et al., moreover, such identity means that all of these celluloses have the identical chain structure though their biological origins are far different. On the other hand, the phiw-dependence of eta0-etas (eta0=zero shear rate viscosity of solution; etas=solvent viscosity) was different between the TC and the DP solution in the semidilute regime: the TC solution exhibited eta0-etas proportional, variant phiw(7.5) and the DP solution eta0-etas proportional, variant phiw4. According to the theory of Doi-Edwards, this exponent of 4 (the DP solution) indicates that the DP behaves as flexible polymers in the solution. In contrast, the dependence for the TC solution seems unexplainable on the basis of molecular theories. This difference probably signifies the difference in the relaxation process or mechanism in entanglement systems.