Volume 11 Issue 1

Treating wood with impregnating materials in order to improve resistance to burning is a commonly employed safety measure. In this study, chestnut (Castanea sativa Mill.) wood samples were impregnated using either Tanalith-E or Wolmanit-CB according to ASTM-D 1413-76 and surface-treated using water-based or synthetic varnish according to ASTM-D 3023. These samples were used to investigate the combustion characteristics of samples left outdoors for one year as detailed in ASTM-E 160-50. The combustion temperatures of the samples left outdoors were similar upon impregnation with either Tanalith-E or Wolmanit-CB. However, the combustion temperature of the samples treated with synthetic varnish was lower than those that were treated with water-based varnish. The time to collapse and the total duration of combustion of the samples left outdoors were shorter for those impregnated with Wolmanit-CB. Weight loss of the samples left outdoors was higher for those that were impregnated with Tanalith-E and treated with water-based varnish. Gas analysis of the samples that were left outdoors indicated that the O2 content of flue gas from samples that were impregnated with Wolmanit-CB and treated with synthetic varnish was high and the CO content of flue gas from the same samples was low.

A series of activated carbons (ACs) were prepared by K2CO3 activation from kraft lignin (KL) that was recovered from papermaking black liquor. The effects of process parameters such as the activation temperature (AT), activated period, K2CO3 to KL mass ratio, and N2 flow rate on the characteristics of the final product were determined. The ACs were characterized using nitrogen adsorption, morphology, and fractal dimension analyses. The results showed that the AT was the main factor influencing the yield, surface area, and pore structure. The yield of ACs obviously decreased from 50.6% to 20.5% with increasing AT from 600 °C to 1000 °C, and decreased with increasing K2CO3/KL mass ratio. Activation time and N2 flow rate had slight effect on the yield of ACs. The surface area and total pore volume increased as the AT rose to 900 °C and then decreased with further increases in temperature. The maximum surface area and total pore volume were 1816.3 m2/g and 1.26 cm3/g, respectively, at a K2CO3 to KL mass ratio of 3:1, AT of 900 °C, activation time of 2 h, and N2 flow rate of 70 cm3/min. The pore structure of the ACs could be tailored by controlling the AT. As the AT was increased from 700 to 1000 °C, the mesoporosity increased from 11.6% to 95.9%. SEM images indicated that the morphology of ACs was modified by the AT. The K2CO3 was partially recycled.

Chemical looping gasification (CLG) is a promising method for the utilization of biomass to produce syngas. However, its realization is largely dependent on the use of an oxygen carrier with a high and stable reactivity in cyclic reduction and oxidation. This work focused on the improvement of reactivity and stability of CuO in chemical looping gasification via the addition of MgAl2O4 as an inert material. First, the stability and reactivity of synthesized Cu-based oxygen carriers were studied in a thermogravimetric analyzer (TGA). Then, the characteristics of CLG of biomass and the oxygen carrier in syngas production were investigated by testing gas components, syngas production, and oxygen carrier sintering performance. The results show that CuO supported on MgAl2O4 has a better capacity for oxygen release than pure CuO and a superior stability and gasification activity in the cyclic chemical looping gasification with biomass. A higher operating temperature led to the production of more syngas from biomass gasification with CuO/MgAl2O4 as the oxygen carrier, particularly for CO and H2. CuO/MgAl2O4 also demonstrated a much better effect on methane reforming in CLG. It is believed that CuO/MgAl2O4 is a suitable oxygen carrier for the chemical looping with oxygen uncoupling (CLOU) and CLG of biomass.

Jute, kenaf, and ramie are important fiber crops in the textile industry, but their core stalks have not been well used. In this study, three fiber crops were examined with enhanced hexoses yields (% cellulose) up to 4.8-, 3.6-, and 1.9-fold from enzymatic hydrolysis of the steam-exploded stalks. Sequential dilute acid/alkali pretreatments achieved the increased hexoses yields up to 7.6-, 4.8-, and 2.8-fold. Without steam explosion, the three crops could increase hexoses yields under extremely high concentrations of NaOH (12% to 16%). While kenaf and ramie mainly showed hemicelluloses removal with steam explosion, jute exhibited an effective co-extraction of hemicelluloses and lignin, which greatly reduced its cellulose DP, hemicellulosic Xyl/Ara, and G-monomer. These findings explain why jute had the highest hexoses yield among the three crops and also suggest that G-monomer and Xyl may interact in a way that mainly determines wall polymers co-extraction with steam explosion.

Specialty paper products made using natural pulps is an attractive field for the paper industry and for researchers. Studying the thermal dynamics of plant pulps is an important step toward improving the thermal stability of papers. This study has the aim of gaining detailed insight into the thermal properties of softwood, hardwood, flax, hemp, mulberry, bamboo, bagasse, and esparto pulps. Chemical composition and thermogravimetric analyses of these non-wood pulps were performed to find the correlations between the chemical, structural, and thermal properties of these pulps. In addition, the Malek model for kinetics of the thermo-decomposition process of pulps is proposed. The kinetics of the most probable mechanism function for G(α) = 1-(1-α) 1/2 of the thermo-decomposition process of plant fibers from 200 to 400 °C is deduced using the Malek model. This study also provides a method to help select the most promising pulps for specialty materials.

A facile and eco-friendly system for synthesis of 5-hydroxymethylfurfural (HMF) from glucose has been investigated with the catalyst dihydric phosphate (H2PO4—) in a methyl isobutyl ketone (MIBK)/H2O biphasic system. The results showed that the catalyst dosage, reaction temperature, and reaction time had noticeable effects on glucose conversion and the HMF yield; more than 50% yield of HMF was achieved at the optimum conditions. In addition, this catalytic system was broadly substrate-tolerant; a satisfactory HMF yield was obtained from higher substrate concentrations and complex substrates. Furthermore, this efficient catalyst was recycled up to nine consecutive times without the loss of catalytic activity.

Different modification routes using fly ash-based calcium silicate (FACS) with starch/sodium stearate were explored to mitigate the negative effect of filler on paper strength and allow for improved filler content. The morphology of the modified fillers and the properties of the filled paper were investigated. The modification route was found to be critical to the amount of starch/sodium stearate deposited on the surface of the filler particles. The most suitable modification route using FACS filler was as follows: starch (20% dosage on o.d. filler) was cooked, filler was added, and then sodium stearate was added (4% dosage on o.d. filler). The tensile index of the FACS-filled paper could be increased by 22% at 30% filler content under the best modification route. The brightness and bulk of the filled paper were also improved. However, the opacity of the filled paper was slightly decreased due to the deposition of starch/sodium stearate on the porous surface of the filler particles.

The development of natural adhesives derived from non-fossil resources is very important for the future. In this study, by taking sugarcane bagasse as the raw material, without using any synthetic resin but adding some eco-friendly additives (citric acid and sucrose), low density particleboards were successfully developed. The effects of board density and additive contents on the physical and mechanical properties of the boards were investigated. The bonding mechanism was observed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed that the low density bagasse particleboard had good mechanical properties and dimensional stability relative to its low board density. The modulus of rupture (MOR) and the thickness swelling (TS) values increased with increasing board density. The board with a density of higher than 0.40 g/cm³ and manufactured at 15% additive content can meet the requirements of the Chinese national forestry industry standard LY/T 1718-2007 (2007). Based on the results of the FTIR spectra, the additive not only increased the hydrogen bond but also the molecular linkage force (C-O-C). X-ray diffraction showed the relationship between crystallinity of cellulose and the strength of particleboard.

Lactic acid (LA) is a potential platform chemical that can be produced from lignocellulosic biomass. The development of a cost-competitive, catalytic-based LA production system is gaining significant attention in modern biorefineries. A series of experimental study was carried out to investigate the chemocatalytic effect of the conversion of oil palm empty fruit bunch (EFB) fibers into lactic acid under hydrothermal conditions. Synthesis of chemicals from lignocellulosic biomass involves complex mechanisms because of the complex composition of the biomass. Therefore, experimental parameters, i.e., temperature, Pb(II) concentration, and reaction time were studied. It was found that production of LA is highly dependent on the experimental conditions. In this study, the highest LA yield obtained from EFB fibers was > 46% (230 °C, 2 mM Pb(II) after 4 h of reaction). However, a similar yield can be achieved either using higher Pb(II) and shorter reactions time or vice versa. The selective production of chemical compounds (glucose, 5-hydroxymethyl furfural (5-HMF), furfural, levulinic acid, and lactic acid) from EFB fibers is highly dependent on the availability of Pb(II) ions.

Lignin is a valuable biomaterial. It is both naturally abundant and readily available as a byproduct of the pulping processes, and the proper reprocessing of lignin is an effective way to achieve waste recovery. Lignin fiber mats with web structures can be produced using electrospinning techniques. Such fiber mats are a promising material for use in the production of filter products. This study focused on the development of filter media using electrospun lignin fiber mats. A series of tests were conducted (e.g., particle penetration and pressure drop) to evaluate the filtration efficiency of the proposed filters. The results indicated that the unfavorable mechanical properties of filters solely comprised of a single layer of the lignin fiber mat would have a negative impact on the filtration efficiency of such filters. However, lignin-based composite filters developed with polyethylene oxide (PEO) fiber mats and surgical mask filter layers exhibited a filtration efficiency comparable to filter products that filter out 95% of small particles (N95). Therefore, the proposed lignin-based composite filter has the potential for air filtration applications.