Biomass Valorization of Walnut Shell for Liquefaction Efficiency

Globally, lignocellulosic biomass has great potential for industrial production of materials and products, but this resource must be used in an environmentally friendly, socially acceptable and sustainable manner. Wood and agricultural residues such as walnut shells as lignocellulosic biomass are one of the most affordable and important renewable resources in the world, which can partially replace fossil resources. The overall objective of the research is to provide background information that supports new applications of walnut shells in a biorefinery context and to increase the economic value of these non-wood forest products. This paper presents the properties characterization of liquefied biomass according to their chemical composition. All results were compared to liquefied wood. In this study, the liquefaction properties of five different walnut shell particle sizes were determined using glycerol as the liquefaction reagent under defined reaction conditions. The liquefied biomass was characterized for properties such as percentage residue, degree of liquefaction, and hydroxyl OH numbers. The chemical composition of the same biomass was investigated for its influence on the liquefaction properties. Accordingly, the main objective of this study was to determine the liquefaction properties of different particle sizes as a function of their chemical composition, also in comparison with the chemical composition of wood. The study revealed that walnut shell biomass can be effectively liquefied into glycerol using H2SO4 as the catalyst, with liquefaction efficiency ranging from 89.21 to 90.98%.

Preparation of Polyurethane Adhesives from Crude and Purified Liquefied Wood Sawdust

Polyurethane (PU) adhesives were prepared with bio-polyols obtained via acid-catalyzed polyhydric alcohol liquefaction of wood sawdust and polymeric diphenylmethane diisocyanate (pMDI). Two polyols, i.e., crude and purified liquefied wood (CLW and PLW), were obtained from the liquefaction process with a high yield of 99.7%. PU adhesives, namely CLWPU and PLWPU, were then prepared by reaction of CLW or PLW with pMDI at various isocyanate to hydroxyl group (NCO:OH) molar ratios of 0.5:1, 1:1, 1.5:1, and 2:1. The chemical structure and thermal behavior of the bio-polyols and the cured PU adhesives were analyzed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Performance of the adhesives was evaluated by single-lap joint shear tests according to EN 302-1:2003, and by adhesive penetration. The highest shear strength was found at the NCO:OH molar ratio of 1.5:1 as 4.82 ± 1.01 N/mm2 and 4.80 ± 0.49 N/mm2 for CLWPU and PLWPU, respectively. The chemical structure and thermal properties of the cured CLWPLW and PLWPU adhesives were considerably influenced by the NCO:OH molar ratio.

Preparation of Polyurethane Adhesive from Wood Sawdust polyol: Application of Response Surface Methodology for Optimization of Catalyst and Glycerol

Response surface methodology (RSM) was applied to optimize catalyst and glycerol values as suitable additives in polyurethane adhesive production and determine the appropriate gel time. Polyurethane adhesive was prepared using polyol, two types of diisocyanate (PMDI and TDI), catalyst, and glycerol with equal NCO/OH ratio. Polyol was produced using the liquefaction process of Beechwood sawdust with ethylene carbonate solvent at 130°C for 120 minutes under atmospheric pressure. Fourier transform infrared spectroscopy (FTIR) results revealed the existence of the hydroxyl groups in the liquefied wood and confirmed that the liquefied wood sawdust is a source of polyols and a potential chemical stock for the synthesis of polyurethane. Also, the adhesive bonding strength was evaluated by lap shear strength. The result of optimization by response surface methodology showed that catalyst and glycerol values were 0.11% and 1.56% for PU adhesive with PMDI, and catalyst and glycerol values of 0.34% and 3.12%for PU adhesive with TDI were appropriate.

Influence of soaking temperature time on the ability prepared liquefaction of wood from cashew nut shell waste

Liquefied wood is one of the phenolic resin. However, unlike commercial phenolic resins that are normally synthesized by the chemical reaction between phenol and formaldehyde, liquefied wood is usually produced by reacting phenol with wood-derived materials, and catalyst at 120-180◦C. Depending on whether the catalyst is a base or a acid, the formed resin is a thermoset or a thermoplastic. In this study, wood liquefaction was prepared from a cashew nut shell waste (CNSW), phenol, and sulfuric acid catalyst. The cashew nut shell waste is taken from Binh Phuoc province - Vietnam and crushed to a size of less than 500 mm. Phenol and sulfuric acid catalyst are chemical experiments. The powder of cashew nut shell waste, phenol, and sulfuric acid were mixed and reacted at 150oC for different soaking times. An optimal soaking temperature time was determined through a cashew nut shell waste residue content in wood liquefaction products. The wood liquefaction products also were determined by a number average molecular weight (Mn) and a weight average molecular weight (Mw) by Gel permeation chromatography method (GPC); the function groups by Fourier Transform Infrared method (FT-IR). The results showed that the formed resin is thermoplastic and the optimal soaking time to prepared liquefied wood is 180 minutes. This sample has a residual cashew nut shell waste ratio of 9.44%, a number average molecular weight of 7552, and a weight average molecular weight of 10640. The liquefied wood from cashew nut shell waste can be used as a binder in the manufacture of the medium density fiberboard (MDF) or as a material to promote the sintered process in the production of woodceramic materials. In addition, the liquefied wood can also be pyrolyzed to form carbon fiber. Carbon fiber can be applied as reinforcing materials for ceramic products.

Adsorption Property, Kinetic and Equilibrium Studies of Activated Carbon Fiber Prepared from Liquefied Wood by Zncl2 Activation

Activated carbon fiber was prepared from liquefied wood by chemical activation with ZnCl2 (Z-LWACF) at different impregnation ratios, with a particular focus on its adsorption property, kinetic and isotherm. The characterization and properties of Z-LWACFs were investigated by nitrogen adsorption/desorption, X-ray photoelectron spectroscopy (XPS), methylene blue (MB) and iodine adsorption. Two activation process methods were employed to prepare Z-LWACF and contrasted with others fibers. The results showed that the Z-LWACF obtained by one-step ZnCl2 activation present higher yields and specific surface area than others fibers. Besides, the change of MB adsorption value at different impregnation ratios was consistent with pore structure distribution above 1.5 nm pore size, indicating that larger micropores (1.5 to 2 nm) and mesopores played a major role in the MB adsorption by Z-LWACF. The kinetics of MB adsorption process was found to follow the pseudo-second-order kinetic model and the adsorption rate was controlled by chemisorption. It was also found that MB adsroption by Z-LWACF belonged to monolayer adsorption and Z-LWACF was easy to adsorb MB.