Characteriza*on of Lignocellulosics by Using Separa*on of Fibre Surface Layers and Nitrogen Sorp*on

Transcription

1 Characteriza*on of Lignocellulosics by Using Separa*on of Fibre Surface Layers and Nitrogen Sorp*on Latvian State Ins,tute of Wood Chemistry COST FP1105 in Stockholm

2 Fibres surface layers separa,on procedure Microscopy & FiberTester Microscopy & FiberTester Parenchima, fines, etc 3 min Fibres from pulp mill Fibres Fibres Screening Mixing h Microscopy & FiberTester Analysis Fibres After peeling S 2 -S 3 Analysis Analysis Peeling Screening P-S 1 Analysis COST FP1105 in Stockholm

3 COST FP1105 in Stockholm

4 What can be done Distribu,on of the fibre cons,tutents across the fibre wall; Molecular characteris,cs of cellulose, hemicelluloses or lignin in different parts of pulp fibre wall; UV, Raman, etc. spectra of the fibre wall frac,ons and their extracts; Bleaching or another treatment of the separated frac,ons; Example: Fluorescence labelling and GPC- MALLS of the unbleached and Molecular weight distribu6on of bleached and unbleached pulps bleached eucalyptus krau pulp In addi6on, the figure on the bo<om (unbleached) shows the distribu6on of carboxyl groups in rela6on to the molecular weight. (A.PoWhast, A.Treimanis et al.) COST FP1105 in Stockholm

5 TEM pictures 2- stage replica technique, Au stained COST FP1105 in Stockholm

6 Determination of fractal dimensionality of lignocellulosics surface using nitrogen gas sorption-desorption data (Sorptometer KELVIN 1042) Fractal analysis of surfaces gives the opportunity to quantify the complexity of the surface of real materials with their irregularity and polydispersity. The surface fractal dimensionality (d fs ) can be applied for characterization of wood and other lignocellulosics in order: to characterize these materials in terms of complexity of the external and internal surface of these materials to monitor the changes caused by various treatments (heating, components removal, degradation, mechanical or chemical processing etc.) The use of nitrogen adsorption-desorption isotherms for calculation of dfs provides a convenient means for monitoring wood/lignocellulosics structural changes due to N2 molecules are mainly adsorbed via van der Waals forces and thus the geometry of the interface resembles the real underlying solid more closely than, for example, in the case of water adsorption. The Neimark approach (Neimark, 1990), considering the fractal surface as a hierarchical system of self-similar pores of different sizes and assuming that the total adsorption consists of capillary condensation and adsorption on the pore surface, is suitable for fractal analysis of microsurface structure of wood (Nakano and Miyazaki, 2003) and other lignocellulosic materials. COST Action FP1105, Stockholm Meeting, December 2 nd - 3 rd, 2012

7 Determination of fractal dimensionality of lignocellulosics surface using nitrogen gas sorption-desorption data (Sorptometer KELVIN 1042) In order to quantify micro-surface transformation caused by hydrolysis lignin modifications via; * cation exchange with Cu 2+ (Cu-lignin); * Si-oligomers (Si-lignin); * modification of Si-lignin by complexing with Cu 2+ (Cu-Si-lignin), the surface fractal dimensionality (d fs ) was calculated using the Neimark approach on the basis of isotherm obtained by N 2 adsorption: d fs = 3 + dln[n(χ)]/dln[-ln(χ)] where N(χ) corresponds to nitrogen adsorbed content (n c ) and χ to relative nitrogen pressure (p/p o ). 3,5 N 2 sorption-desorption isotherm by hydrolysis lignin 3 2,5 ln(nc) (g/g%) 2 1,5 1 0,5 0-0, ln(-ln(p/p0)) The relationship between logarithmic adsorbed nitrogen content, nc and double logarithmic relative pressure of nitrogen gas, P/Po). 1 hydrolysis lignin, 2 Cu-lignin, 5 Si-lignin, 4 Cu-Si-lignin

8 Lignin product Characterization of porous structure of hydrolysis lignin samples Surface fractal dimensionality, d fs BET Specific surface, m 2 /g; Volume of pores, mm 3 /g, Total Micropores Hydrolysis lignin Hydrolysis lignin + Cu Siliceous hydrolysis lignin Siliceous hydrolysis lignin + Cu 2+ Determination of fractal dimensionality of lignocellulosics surface using nitrogen gas sorption-desorption data (Sorptometer KELVIN 1042) When the hydrolysis lignin was modified by ion-exchange interaction with Cu 2+, the d fs decreased a little from 2.46 (the value typical for isolated lignins) to 2.35, indicating the partial reduction in lignocellulosic surface complexity, that can be interpreted in terms of surface screening effect of Cu adsorption. Modification of lignin matrix with Si-oligomers resulted in increasing of the fractal dimensionality, but following alteration of Si-lignin by complexing with Cu 2+ led to the further significant increase in d fs. These changes were accompanied by the development of new pores system with eightfold increase in the BET specific surface of Cu-Si-lignin as compared with the parent hydrolysis lignin, and appearance of microporocity. COST Action FP1105, Stockholm Meeting, December 2 nd - 3 rd, 2012

9 The one-axle compression test for characterization of lignocellulosic structure A single pelletizing unit having a close fit plunger assembly was used to study the behavior at compression of a range of ground plant biomass samples (d 2.0 mm): birch wood, alder wood, pine wood, willow wood, goat willow bark, alder bark, pine bark, wheat straw, rape straw, softwood hydrolysis lignin, Reed canary grass. The single pelletizing unit used in the experiments The cylinder die was mm long and 8.00 mm in diameter. The mass of sample used was ± gr. Compressive force up to 150 MPa was applied using the ZWICK/ROELL Z100 testing machine. The machine ZWICK/ROELL Z100 The mechanical deformations of ground lignocellulosic biomass in the compression process Biomass in the die The impact of the reversible deformation was expressed by relaxation ratio (R) value: R= γ 150 /γ t, where γ 150 is the density of a sample in the die at 150 MPa and γ t - the density of the relaxed sample. Irreversible deformations Inertial Stress 150 MPa Stress removed Reversible deformations I m m e d i a t e expansion e l a s t i c deformation Pellet removed 24 h ago Expansion over the time viscoelastic deformation Plastic deformation

10 The one-axle compression test for characterization of lignocellulosic structure The values of R highly depend on the sample origin and its prehistory (type of processing). For example the highest R=2.05 (the highest elastic deformation shear) was determined for grey alder wood. The cell wall of soft wood (pine, spruce) has some lower elasticity (R= ). The chemical destruction of cell wall (acid hydrolysis lignin of spruce ) leads to the appearance mainly of plastic deformation (R=1.17) in result of compression stress. Stress, MPa R=1.17 E =36.6 kj/kg Strain, mm Lignin grey alder wood R=2.05 E= 27.7 kj/kg Deformation curves for compression of lignin and ground alder wood: E a specific energy consumption for compression Destruction of wood cell wall upon the hydrolysis processing excludes the contribution of wall elastic properties to lignin behavior at compression. At stress impact, the damage of the network bonds results in the rearrangement of lignocellulosic structure with appearance of the irreversible plastic deformation and the higher value of energy consumption for hydrolysis lignin compression. The results obtained allow to propose the one-axle test as a sensitive tool for estimation of the effects of any treatment of wood on its cell wall structure. COST Action FP1105, Stockholm Meeting, December 2 nd - 3 rd, 2012

11 Thank You Thank You for for Attention!