Cellulose In Aqueous System Research Articles

Production of acetol and lactic acid from cellulose hydrogenolysis over Sn-Fe@C catalysts

Acetol and lactic acid are valuable platform chemicals that have a broad range of industrial applications and their production from renewable cellulose is of scientific and practical significance. A series of Sn-Fe@C catalysts were prepared by sol-gel and high-temperature annealing method in an inert atmosphere and then used for preparing acetol and lactic acid by one-step hydrogenolysis of cellulose in aqueous system. 3Sn1Fe@C600 as catalyst, the total acetol and lactic acid yield of 45.4% were obtained at 240 °C for 1 h under H2 atmosphere, of which the yields of acetol and lactic acid were 24.3% and 21.1%, respectively. The results indicated that the yield of acetol and lactic acid was strongly dependent on the Sn/Fe ratio of the catalyst as well as the annealing temperature. The characterizations including BET, XRD, XPS, Py-FTIR and CO2-TPD were carried out to explore the relationship between the structure of catalysts and catalytic activity. The strong L acid sites, basic sites and the metal active sites of the catalyst were the key factors affecting the selective production of acetol and lactic acid from cellulose hydrogenolysis.

Dissolution and Metastable Solution of Cellulose in NaOH/Thiourea at 8 °C for Construction of Nanofibers.

To develop a facile approach for the dissolution of cellulose, a novel solvent (9.3 wt % NaOH/7.4 wt % thiourea aqueous solution) was used, for the first time, to dissolve cellulose within 5 min at 8 °C. The results of NMR and Raman spectra demonstrated that stable thiourea···OH- complexes were formed through strong hydrogen bonds in NaOH/thiourea at room temperature. Moreover, the strength of the hydrogen bonds in thiourea···OH- complexes was much higher than that in urea···OH- complexes, and the number of thiourea···OH- complexes increased significantly in 9.3 wt % NaOH/7.4 wt % thiourea compared to that in 9.5 wt % NaOH/4.5 wt % thiourea, which dissolved cellulose at -5 °C, leading to the dissolution of cellulose at a relatively high temperature (8 °C). The cellulose that dissolved at such a high temperature was metastable. The results of dynamic light scattering and transmission electron microscope experiments confirmed that the extended cellulose chains and their aggregates coexisted in the dilute cellulose solution. Interestingly, stiff cellulose chains could be self-assembled in parallel to form nanofibers in the metastable cellulose solution, from which cellulose microspheres consisting of nanofibers could be easily produced by inducing heating. This work not only proposed a novel method for the dissolution of cellulose in aqueous system at temperatures over 0 °C but also opened up a new pathway for the construction of nanofibrous cellulose materials.

Dissolution state of cellulose in aqueous systems. 2. Acidic solvents

Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution.

Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents

The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.

Facile Approach for the Dispersion of Regenerated Cellulose in Aqueous System in the Form of Nanoparticles

This study reports a facile method to disperse cellulose in deionized water, wherein a critical condition of regenerated cellulose is discovered, where it completely disperses up to a maximum of 5 g L(-1) concentration in deionized water with the help of ultrasonication. The dispersed cellulose is characterized by TEM and DLS, the latter among which shows 200 nm hydrodynamic radii of cellulose nanoparticles dispersed in deionized water. FTIR analysis of dispersed cellulose reveals that dispersed cellulose losses its crystallinity during regeneration and dispersion step employed in this study. The dispersed cellulose reported in this study is able to form free-standing, transparent films, which were characterized by SEM, XRD, TGA, EDX, and FTIR spectroscopy and show resistance against dissolution in water. Additionally, the dispersed cellulose is able to undergo at least three times faster enzymatic hydrolysis in comparison to pristine microcrystalline cellulose under similar reaction conditions. The dispersed cellulose reported here could be a better material for reinforcement, preparation of hydrogels, and drug delivery applications under physiological environment.

A Facile Construction of Supramolecular Complex from Polyaniline and Cellulose in Aqueous System

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTA Facile Construction of Supramolecular Complex from Polyaniline and Cellulose in Aqueous SystemXingwei Shi†, Lina Zhang*†, Jie Cai†, Gongzhen Cheng†, Hongming Zhang‡, Ji Li‡, and Xianhong Wang‡View Author Information† Department of Chemistry, Wuhan University, Wuhan 430072, China‡ Key Lab of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, ChinaPhone: +86-27-87219274. Fax: +86-27-68762005. E-mail: [email protected]Cite this: Macromolecules 2011, 44, 12, 4565–4568Publication Date (Web):June 7, 2011Publication History Received4 May 2011Revised2 June 2011Published online7 June 2011Published inissue 28 June 2011https://doi.org/10.1021/ma2009904Copyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views3197Altmetric-Citations61LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (2 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Cellulose,Noncovalent interactions,Plastics,Polymers,Solution chemistry Get e-Alerts

DISTRIBUTION OF SUBSTITUENTS IN CELLULOSE ETHERS PREPARED IN AQUEOUS AND NON-AQUEOUS SYSTEMS

The distribution of substituents in partially substituted cellulose ethers (methyl-, carboxymethyl-, benzyl- and methallylcelluloses) prepared in aqueous and non-aqueous systems was studied. The reactivity order of three hydroxyl groups in cellulose in aqueous systems was HO-2>HO-6>HO-3 with the exception for benzylation. On the other hand, the reactivity order was HO-6>HO-2_??_HO-3 for etherifications with powdered sodium hydroxide and etherifying reagents except iodides in a non-aqueous cellulose solvent, SO2-diethylamine-dimethylsulfoxide system. The difference in reactivities of the hydroxyl groups in the non-aqueous system were much smaller than those in aqueous systems.

A New Type of Phenomenon of Flow Birefringence in Macromolecular Solutions

DURING an investigation of solution states of methyl cellulose in aqueous systems, an unexpected new phenomenon was noted. The observed optical anisotropy as a function of the velocity gradient in the systems changed anomalously, as shown in Fig. 1 (solid lines). Reproducibility of the variations both of the degree of birefringence and the angle of extinction versus the rates of shear were within experimental error.