Purification of cellulosic pulp by hot water extraction

Hot water extraction (HWE) of pulp in a flow-through reactor was evaluated as a method to purify paper-grade pulps. About 50–80 % of the xylan and up to 50 % of the lignin in unbleached birch Kraft pulp was extracted by the HWE without losses in cellulose yield. The residual xylan content in the extracted pulps was predominantly too high for dissolving-grade applications, but some of the pulps with a xylan content of 5–7 % might still be suitable as rayon-grade pulps. Increasing extraction temperature lowered the xylan content at which cellulose yield started to decrease. Furthermore, at any given xylan content, increasing extraction temperature resulted in cellulosic pulp with higher degree of polymerization. The extracted xylan was recovered almost quantitatively as xylo-oligosaccharides. The results suggest that HWEs at elevated temperatures may be applied to purify cellulosic pulps, preferably containing a low xylan content, and to recover the extracted sugars.Finnish Bioeconomy Cluster FIBIC OyTechnology Development Centre (Finland

Deformation mechanisms in ionic liquid spun cellulose fibers

This is the final version of the article. Available from the publisher via the DOI in this record.The molecular deformation and crystal orientation of a range of next generation regenerated cellulose fibers, produced from an ionic liquid solvent spinning system, are correlated with macroscopic fiber properties. Fibers are drawn at the spinning stage to increase both molecular and crystal orientation in order to achieve a high tensile strength and Young’s modulus for potential use in engineering applications. Raman spectroscopy was utilized to quantify both molecular strain and orientation of fibers deformed in tension. X-ray diffraction was used to characterize crystal orientation of single fibers. These techniques are shown to provide complimentary information on the microstructure of the fibers. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm−1, emanating from the backbone structure of the cellulose polymer chains was followed under tensile deformation. It is shown that the shift rate of this band with respect to strain increases with the draw ratio of the fibers, indicative of an increase in the axial molecular alignment and subsequent deformation of the cellulose chains. A linear relationship between the Raman band shift rate and the modulus was established, indicating that the fibers possess a series aggregate structure of aligned crystalline and amorphous domains. Wide-angle X-ray diffraction data show that crystal orientation increases with an increase in the draw ratio, and a crystalline chain slip model was used to fit the change in orientation with fiber draw ratio. In addition to this a new model is proposed for a series aggregate structure that takes into better account the molecular deformation of the fibers. Using this model a prediction for the crystal modulus of a cellulose-II structure is made (83 GPa) which is shown to be in good agreement with other experimental approaches for its determination.The Engineering and Physical Sciences Research Council (EPSRC) is acknowledged for funding provided under Grant No. EP/L017679/1

High-Performance Acetylated Ioncell‑F Fibers with Low Degree of Substitution

Cellulose acetate is one of the most important cellulose derivatives. Herein we present a method to access cellulose acetate with a low degree of substitution through a homogeneous reaction in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]). This ionic liquid has also been identified as an excellent cellulose solvent for dry-jet wet fiber spinning. Cellulose was dissolved in [DBNH] [OAc] and esterified in situ to be immediately spun into modified cellulose filaments with a degree of substitution (DS) value of 0.05-0.75. The structural properties of the resulting fibers, which are characterized by particularly high tensile strength values (525-750 MPa conditioned and 315-615 MPa wet) and elastic moduli between 10-26 GPa, were investigated by birefringence measurements, wide-angle X-ray scattering, and molar mass distribution techniques while their unique interactions with water have been studied through dynamic vapor sorption. Thus, an understanding of the novel process is gained, and the advantages are demonstrated for producing high-value products such as textiles, biocomposites, filters, and membranes.Peer reviewe

Furfural production from xylose and birch hydrolysate liquor in a biphasic system and techno-economic analysis

Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by the US Department of Energy. In this study, furfural was produced from xylose and birch hydrolysate liquor employing a batch reactor in a biphasic system. The formation of furfural was conducted under auto-catalyzed conditions. 2-sec-Butylphenol was used as extractant to promptly extract furfural from the aqueous phase in order to minimize furfural degradation reactions. The effect of time, temperature, and organic-to-aqueous phase ratio were investigated. The maximum furfural yields from xylose and birch hydrolysate liquor as feedstock under auto-catalyzed conditions when employing 2-sec-butylphenol (SBP) were 59 mol% and 54 mol%, respectively. In the monophasic system when using hydrolysate, 46% furfural was yielded. Based on a techno-economic analysis carried out for furfural, the total investment cost for a plant integrated with an existing pulp mill or bio-refinery is estimated as 14 M€. The minimum selling price of furfural found to be 1.62 € kg-1. With a furfural selling price of 1.93 € kg-1, the payback period is approximately 5 years and an internal rate of return (IRR) of 20.7% is achieved at the end of the project lifetime.Postprint (published version

Vapor-Liquid Equilibrium of Ionic Liquid 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium Acetate and Its Mixtures with Water

Ionic liquids have the potential to be used for extracting valuable chemicals from raw materials. These processes often involve water, and after extraction, the water or other chemicals must be removed from the ionic liquid, so it can be reused. To help in designing such processes, we present data on the vapor-liquid equilibrium of the system containing protic ionic liquid 7-methyl-1,5,7-triazabicyclo [ 4.4.0 ] dec-5-enium acetate, water, acetic acid, and 7-methyl-1,5,7-triazabicyclo [4.4.0] dec-5-ene. Earlier studies have only focused on mixtures of water and an ionic liquid with a stoichiometric ratio of the ions. Here, we also investigated mixtures containing an excess of the acid or base component because in real systems with protic ionic liquids, the amount of acid and base in the mixture can vary. We modeled the data using both the ePC-SAFT and NRTL models, and we compared the performance of different modeling strategies. We also experimentally determined the vapor composition for a few of the samples, but none of the modeling strategies tested could accurately predict the concentration of the acid and base components in the vapor phase.Peer reviewe

Recent advances in the catalytic production of platform chemicals from holocellulosic biomass

This Review discusses novel catalytic pathways of lignocellulosic biomass to value-added chemicals including biomass-derived sugar alcohols, organic acids, furans and biohydrocarbons. These production approaches are undertaken by biological, chemical and thermochemical transformations or a combination of them. Nevertheless, the majority of research in this area is focused on the design of heterogeneous catalysts to convert value-added products from holocellulosic biomass. Biorefineries represent the peak of biomass processes in order to produce valuable chemicals and liquid fuels avoiding the utilization of corroding and toxic elements. The aim of the present Review is to offer the readers a broad overview of recent holocellulosic-based chemical and fuels production technologies via heterogeneous catalysis. There is also an overview of the economic aspects to efficiently produce these platform chemicals at industrial scale. To summarize this Review, an outlook and conclusions of the reported processes to date is provided.Postprint (author's final draft

Polymer-Based n-Type Yarn for Organic Thermoelectric Textiles

A conjugated-polymer-based n-type yarn for thermoelectric textiles is presented. Thermoelectric textile devices are intriguing power sources for wearable electronic devices. The use of yarns comprising conjugated polymers is desirable because of their potentially superior mechanical properties compared to other thermoelectric materials. While several examples of p-type conducting yarns exist, there is a lack of polymer-based n-type yarns. Here, a regenerated cellulose yarn is spray-coated with an n-type conducting-polymer-based ink composed of poly(benzimidazobenzophenanthroline) (BBL) and poly(ethyleneimine) (PEI). The n-type yarns display a bulk electrical conductivity of 8 7 10−3 S cm−1 and Seebeck coefficient of −79 \ub5V K−1. A promising level of air-stability for at least 13 days can be achieved by applying an additional thermoplastic elastomer coating. A prototype in-plane thermoelectric textile, produced with the developed n-type yarns and p-type yarns, composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated regenerated cellulose, displays a stable device performance in air for at least 4 days with an open-circuit voltage per temperature difference of 1\ua0mV\ua0\ub0C−1. Evidently, polymer-based n-type yarns are a viable component for the construction of thermoelectric textile devices

Furfural production in a biphasic system using a carbonaceous solid acid catalyst

The formation of furfural from xylose was investigated under heterogeneously catalyzed conditions with Starbon®450-SO3H as a catalyst in a biphasic system. Experiments were performed based on a statistical experimental design. The variables considered were time and temperature. Starbon®450-SO3H was characterized by scanning electron microscopy, N2-physisorption, thermogravimetric analysis, diffuse reflectance infrared Fourier transform, Raman spectroscopy, pyridine titration and X-ray photoelectron spectroscopy. The results indicate that sulfonated Starbon®450-SO3H can be an effective solid acid catalyst for furfural formation. A maximum furfural yield and selectivity of 70¿mol% was achieved at complete xylose conversion under optimum experimental conditions. The present paper suggests that functionalized Starbon®450-SO3H can be employed as an efficient solid acid catalyst that has significant hydrothermal stability and can be reused for several cycles to produce furfural from xylose.Peer ReviewedPostprint (author's final draft