Effect of simultaneous use of microwave and ultrasound irradiations on the sulfuric acid hydrolysis lignin (SAHL) depolymerization

In this study, the individual and combined effect of microwave (MW) and ultrasound (US) processes on the depolymerization of sulfuric acid hydrolysis lignin (SAHL) was investigated in a hybrid microwave–ultrasound...

Optimization of the Hot-Pressing Regime in the Production of Eco-Friendly Fibreboards Bonded with Hydrolysis Lignin

This research was aimed at studying the potential of using residual lignin from acid hydrolysis as a binder in manufacturing eco-friendly, dry-process fibreboards. For that purpose, a modification of the adhesive system and hot-pressing regime was conducted. The adhesive system applied was composed of 2 % phenol-formaldehyde (PF) resin and 10 % hydrolysis lignin (based on the dry fibres). The PF resin does not only act as a binder but generally contributes to the even distribution and good retention of the main binder – hydrolysis lignin. A specific hot-pressing cycle was used. In the first stage, the pressure was 1.0 MPa, followed by an increased pressure of 4.0 MPa, and subsequent cooling. The purpose of the initial lower pressure was softening the lignin and reduction of the material moisture content. The effect of the second stage of hot-pressing on the properties of eco-friendly fibreboards was investigated. It was determined that the fibreboards produced with 2 % PF resin and 10 % hydrolysis lignin have similar physical and mechanical properties to those of the control panels, produced with 10 % PF resin at a standard hot-pressing cycle. The findings of this work demonstrate that residual hydrolysis lignin can be effectively utilized as a binder in the production of eco-friendly, dry-process fibreboards with acceptable physical and mechanical properties.

SYNTHESIS, STRUCTURE AND PROPERTIES OF ORGANIC GELS BASED ON LARCH BARK TANNINS AND HY-DROLYSIS LIGNIN

For the first time, tannin-lignin-formaldehyde and tannin-lignin-furfuryl organic gels were obtained on the basis of larch bark tannins and hydrolysis lignin by sol-gel condensation with formaldehyde and furfuryl alcohol. Their physico-chemical properties were studied by varying the content of lignin (from 5 to 30 wt%) and a fixed mass ratio of polyphenolic substances to the crosslinking reagent (1 : 1.5). With an increase in the lignin content the density of tannin-lignin formaldehyde gels decreases from 0.83 to 0.53 g/ cm3, and that of tannin-lignin-furfuryl gels is from 0.32 to 0.14 g / cm3. According to the FTIR data, the structures of tannin-lignin-formaldehyde and tannin-lignin-furfuryl gels are formed by aromatic fragments cross-linked with methylene and methylene-ether bridges. Scanning electron microscopy shows that the addition of appropriate amounts of lignin to tannins (up to 10 wt% when using formaldehyde and up to 20 wt% when using furfuryl alcohol) promotes the formation of gels with a more developed porous structure. In the case of tannin-lignin-formaldehyde gel, the specific surface area and sorption of methylene blue are 12 m2 / g and 43 mg / g and for tannin-lignin-furfuryl gel – 72 m2 / g and 114.5 mg/g, respectively. It was found that an increase in the lignin content in the gel composition over 20 wt.% is accompanied by the phase localization of lignin (precipitation), which reduces the strength of the resulting gel and reduces its specific surface area.

Catalytic Conversion of Lignin in an Isopropanol/formic Acid Medium With Nimo Catalyst Promoted by W Species

Background: Large amounts of enzymatic hydrolysis lignin (EHL) are generated with the production of cellulosic bioethanol. Efficient degradation and upgrading of EHL is significant for the sustainable and stable development of energy supply.Results: In this study, hydrodeoxygenation (HDO) of EHL to biofuels was carried out promoted by the in situ hydrogen donor produced from the decomposition of formic acid over NiMo catalysts. Results showed that active sites (derived from the support SiO2, W, and NiMo species) had remarkable effect on lignin conversion, and the highest oil yield (57.2 wt%) was gained over NiMo/W-SiO2 catalyst. Conclusions: The product evolution demonstrated that active metal sites (derived from NiMo species) favored hydrogenolysis and deoxygenation via leading in situ hydrogen to attack C-O-C bonds, while acid sites (derived from the support) adsorbed and activated chemical bonds in lignin, resulting in the linkage cleavage caused by the heating program. The obtained bio-oil was rich in alkyl guaiacols (6.7 wt%), containing stable chemical properties and high quality.

Preparation of Molded Fiber Products from Hydroxylated Lignin Compounded with Lewis Acid-Modified Fibers Its Analysis

In this study, molded fiber products (MFPs) were prepared from lignin compounded with Lewis acid-modified fibers using enzymatic hydrolysis lignin (EHL) as a bio-phenol. The fibers were modified and compounded entirely through hot-pressing. To improve the reactivity of enzymatic lignin, hydroxylated enzymatic hydrolysis lignin (HEHL) was prepared by hydroxylation modification of purified EHL with hydrogen peroxide (H2O2) and ferrous hydroxide (Fe(OH)3). HEHL was mixed uniformly with Lewis acid-modified fibers on a pressure machine and modified during the molding process. The purpose of Lewis acid degradation of hemicellulose-converted furfural with HEHL was to generate a resin structure to improve the mechanical properties of a MFPs. The microstructure of the MFP was shown to be generated by resin structure, and it was demonstrated that HEHL was compounded on Lewis acid-modified fibers during the molding process. The thermal stability of the MFP with composite HEHL did not change significantly owing to the addition of lignin and had higher tensile strength (46.28 MPa) and flexural strength (65.26 MPa) compared to uncompounded and modified MFP. The results of this study are expected to promote the application of high lignin content fibers in molded fibers.