Vladimir A. Levdansky

Optimized methods for obtaining cellulose and cellulose sulfates from birch wood

The methods of obtaining cellulose and cellulose sulfates from birch wood based on the use of one-step catalytic delignification of wood by hydrogen peroxide in acetic acid–water medium were studied. The conditions of birch wood oxidative delignification by acetic acid/hydrogen peroxide mixtures in the presence of sulfuric acid catalyst were optimized in order to obtain an acceptable yield of cellulose product with low content of residual lignin. Cellulose extracted from birch wood by green method was used for preparation of cellulose sulfates in dioxane solution. The homogeneous sulfation of obtained cellulose by chlorosulfonic acid in dioxane allows to reduce the fragmentation of polymer and to synthesize cellulose sulfates with a finer and more homogeneous structure as compared to cellulose sulfates prepared by heterogeneous sulfation in harmful pyridine. Obtained samples of cellulose and cellulose sulfates were characterized by XRD, SEM, AFM, NMR, FTIR, Raman, XPS and chemical methods.

Green biorefinery of larch wood biomass to obtain the bioactive compounds, functional polymers and nanoporous materials

The first green biorefinery of larch wood based on the fractionation of biomass into dihydroquercetin (DHQ), arabinogalactan (AG), microcrystalline cellulose (MCC) and soluble lignin (SL) is reported. The new green method of one-step isolation of DHQ and AG from larch wood by ethanol–water solution was developed. The first results of kinetic studies and optimization of the process of extracted larch wood peroxide fractionation into MCC and SL in acetic acid–water medium in the presence of green TiO2 catalyst are described. The products obtained from larch wood were characterized by FTIR, NMR, XRD, AFM and chemical methods. The scheme of larch wood biorefinery is suggested which integrates the developed processes of woody biomass fractionation into DHQ, AG, MCC and SL. All developed methods use non-toxic and less-toxic reagents, such as water, ethanol, hydrogen peroxide and acetic acid.

Combination of phase-solubility method and capillary zone electrophoresis to determine binding constants of cyclodextrins with practically water-insoluble compounds

HIGHLIGHTSCombination of phase‐solubility technique and electrophoresis was suggested.Mode allows to determine binding constants of CD complexes with insoluble compounds.Background electrolyte for CE should contain ethanol and cyclodextrin if necessary.Binding constants between betulinic/betulonic acids and hydroxypropyl‐cyclodextrin. ABSTRACT The combined method based on phase‐solubility technique and capillary zone electrophoresis (PS‐CZE) was suggested for the determination of binding (stability) constants of cyclodextrins (CD) complexes with water‐insoluble organic compounds that have no or weak UV chromophores. In this method, the insoluble compounds are agitated at the desired temperature in CD solutions with different concentration up to the attainment of equilibrium and then CZE is used to determine the concentration of the compounds that have passed into the solutions. To avoid precipitation and complex dissociation, the background electrolyte (BGE) for CZE should contain ethanol and, if necessary, cyclodextrin. The samples should be diluted with the BGE without CD so that the CD concentrations in BGE and samples were equal to preclude a baseline shift. Using the suggested approach, the inclusion complexes between betulinic and betulonic acids, pentacyclic lupane‐type triterpenes, and hydroxypropyl‐&bgr;‐ and &ggr;‐cyclodextrins (HP‐&bgr;‐CD and HP‐&ggr;‐CD) were studied. It was found that solubility of the acids studied in HP‐&bgr;‐CD solutions did not differ from their solubility in pure water. That is, the HP‐&bgr;‐CD complexes of the acids studied were not formed in noticeable amount. At the same time, the acids formed inclusion complexes with HP‐&ggr;‐CD, what possibly was caused by the greater size of the HP‐&ggr;‐CD molecule as compared to HP‐&bgr;‐CD. To determine binding constants by Higuchi and Connors method, the acids solubility was determined by CZE after their agitation in the solutions of HP‐&ggr;‐CD (with 0.6 molar substitution) at 25 °C for 3 days. The dependences of acids solubility on HP‐&ggr;‐CD concentration deviated from straight line in the range of high concentration (AN mode). This can be explained by a self‐association of HP‐&ggr;‐CD molecules. Using the linear segment of the solubility dependences on CD concentration, the binding constants were determined. Their logarithms for the HP‐&ggr;‐CD complexes with betulonic and betulinic acids were 3.88 ± 0.14 and 3.82 ± 0.12, respectively.

Integration of peroxide delignification and sulfamic acid sulfation methods for obtaining cellulose sulfates from aspen wood

A new method to obtain cellulose sulfates from available and inexpensive raw material—aspen wood was developed. This method integrates catalytic peroxide delignification and sulfamic acid sulfation stages. Solvents such as acetic acid and water were used for isolation of pure cellulose by wood peroxide delignification with TiO2 catalyst. Low-aggressive and less-toxic sulfating agent—sulfamic acid–urea mixture was used to obtain cellulose sulfates.

Effect of Lignin on the Properties of Organic and Carbon Gels from Polyphenols of the Larch Bark

The influence of lignin on the properties of organic and carbon gels synthesized by sol-gel polymerization of a mixture of formaldehyde and polyphenols isolated by various solvents from the larch bark was investigated. The porous structure and adsorption properties of polymer gels synthesized from mixtures of formaldehyde and ethanol extracts of bark by varying the pH value of initial solutions in the range of 4 to 12 were studied by BET and SEM methods. It was shown that an increase in pH value leads to the formation of organic gels with a more compacted texture and narrow pores. Carbonization of organic gels at 900 °C promotes the significant development of the specific surface area (up to 477 m2/g) of the obtained carbon gels. It was found that the addition of lignin in an amount of 10 % wt. to the polyphenols extracted by water from the larch bark improves the texture characteristics of the obtained organic and carbon gels and increases theirs elasticity and strength. But the increase of the lignin content to 20-30 % wt. reduces the total porosity and the total pore volume of the obtained gels. The effect of lignin on the properties of gels, obtained with the use of polyphenols extracted from larch bark by water–alkaline solution, is less pronounced.

Sulfation of Xylan with Chlorosulfonic Acid in 1,4-Dioxane

Sulfation of birch wood xylan by chlorosulfonic acid in 1,4-dioxane was studied for the first time. It has been found, that sulfation of xylan at a temperature of 20 °C for 5–6 hours makes it possible to obtain xylan sulfates with a degree of sulfur substitution 1.2. The optimum conditions of the reaction were found which allow to carry out the sulfation of xylan in milder conditions, as compared to known methods.

Spectrophotometric and quantum-chemical study of acid-base and complexing properties of (+/-)-taxifolin in aqueous solution

Abstract This study reports the acid-base properties of taxifolin (Tf) in HCl media and aqueous complexation with Ni(II). The equilibrium processes was investigated using a spectrophotometric technique and ab initio calculations. Equilibrium constant of protonation was determined using a non-linear Cox-Yates method. Analysis of Ni(II)-Tf complex species under metal dominance conditions was performed in tris-buffer solution. For interpretation and verification of experimental results the Def2-SVP/DFT/PBE0/SMD level was used.

Solubility Study of Betulonic Acid in the Presence of Hydroxypropyl-γ-cyclodextrin by Capillary Electrophoresis

Olesya V. Popovaa, Viktoria V. Sursyakova*a, Galina V. Burmakinaa, b Nikolay G. Maksimova, Vladimir A. Levdanskya and Anatoly I. Rubayloa, b, c aInstitute of Chemistry and Chemical Technology SB RAS FRC “Krasnoyarsk Science Center SB RAS” 50/24 Akademgorodok, Krasnoyarsk, 660036, Russia bSiberian Federal University 79 Svobodny, Krasnoyarsk, 660041, Russia cKrasnoyarsk Scientific Centre, SB RAS 50 Akademgorodok, Krasnoyarsk, 660036, Russia

Study of Microcryslalline Cellulose Sulfates Obtained with the Use of Chlorosulfonic and Sulfamic Acids

Composition and structure of microcrystalline cellulose (MCC) sulfates obtained by traditional and new advanced methods of MCC sulfation were compared. Data on the composition and structure of MCC sulfates synthesized in the medium of chlorosulfonic acid –1,4-dioxane and by sulfation of MCC with sulfamic acid in the presence of urea in N,N-dimethylformamide and diglyme were obtained with the use of elemental analysis, FTIR, Raman, 13C NMR, XRD, XPS, SEM and AFM methods. It was shown that MCC sulfates synthesized by new methods have more homogeneous composition and morphology as compared to sulfates obtained by known methods.