Natalia M. Ivanchenko

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 catalytic valorization of hardwood biomass into valuable chemicals with the use of solid catalysts

Results of the study on green valorization of hardwood biomass into valuable chemicals with the use of solid catalysts were described. The heterogeneous catalytic processes of hemicelluloses and cellulose hydrolysis, wood oxidative fractionation and lignin depolymerization in supercritical spirits are suggested to employ for the green biorefinery of hardwood to xylose, pure cellulose, glucose, alcohols and liquid hydrocarbons.

Porous carbon materials produced by the chemical activation of birch wood

It was established that the main factors responsible for the yield and specific surface area of porous carbon materials obtained by the chemical activation of the wood of birch are the nature of a modifying agent and the temperature of pyrolysis. The additional opening of the porous structure of the product of the chemical activation of wood occurs at the stage of its water treatment as a result of the removal of water-soluble compounds. The conditions of the carbonization of birch wood modified with H3PO4, KOH, and ZnCl2 were chosen in order to provide the significant development of the porous structure of carbon materials. The porous carbon material with the highest specific surface area (more than 2560 m2/g) was obtained by the water washing of the product of the carbonization of birch wood modified H3PO4 at 400°C.

Production and properties of porous carbon materials from chemically modified microcrystalline cellulose

Certain fundamental aspects of how the porous structure is formed in carbon materials produced by pyrolysis of microcrystalline cellulose modified with phosphoric acid, potassium hydroxide, and zinc chloride were determined. The above chemical promoters shift the onset of the process of intense thermal transformation of cellulose to lower temperatures and promote formation of porous carbon materials. Water treatment of porous carbon materials produced by pyrolysis of microcrystalline cellulose with high content of a promoter leads to additional pore opening due to the removal of the excess amount of the promoter and soluble products formed in its interaction with cellulose, which makes it possible to obtain porous carbon materials with specific surface area of up to 1500 m2 g−1.

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.

The Integration of Catalytic Processes of Acid Hydrolysis and Peroxide Delignification to Obtain the Bioethanol from Aspen Wood

The processes of catalytic hydrolysis of hemicelluloses and cellulose of aspen wood were studied at the temperatures 100 and 150 °C. The dissolved mineral acids (H2SO4, HCl), ion exchange resin Amberlyst-15 and acid-modified SBA-15, Sibunit-4 were used in hydrolysis of aspen wood as the catalysts. The optimal conditions for the implementation of catalytic processes of acid hydrolysis of wood hemicelluloses, peroxide delignification of lignocellulose and hydrolysis of cellulose for the production of hydrolysates with the maximum glucose yield and the minimum amount of inhibitors of enzymatic processes (furfural and 5-hydroxymethylfurfural) were established. The estimated yields of bioethanol obtained by integration of optimized catalytic processes of acid hydrolysis of polysaccharides and peroxide delignification of lignocellulose of aspen wood were evaluated.

Production of porous carbon materials from bark

The effect of the conditions of consecutive carbonization–activation of the bark of larch, fir tree, and birch in a fluidized bed reactor on the yield, textural characteristics, and sorption properties of the resulting porous carbon materials was studied. The rate of temperature increase at the stage of the pyrolysis of bark exerted the greatest effect on the specific surface area, total pore volume, and sorption capacity of porous carbon materials for iodine and methylene blue. The porous carbon materials obtained by the slow pyrolysis (5 K/min) of larch bark with an isothermal exposure for 60 min at 600°C and the subsequent activation with CO2 at 850°C for 30 min were characterized by a maximum sorption activity. The porous carbon materials obtained from bark by consecutive carbonization–activation in a fluidized bed were similar to commercial powder sorbents from wood in their characteristics.