Recent technologies in the production of chemicals and bio-materials products are focusing on lignocellulosic resources since it is the world’s most abundant material, low cost, as well as sustainable. Lignocellulosic biomass consists of three main compounds: cellulose, hemicellulose, and lignin. Productions of carbon fiber from lignin as its precursor are proposed to reduce the usage of fossil fuel based materials. However, the difficulties on recovering lignin from biomass are widely known. Therefore, several studies were conducted to explore possible technologies to isolate lignin from the complex lignocellulosic biomass in simple and minimal cost. One of the potential technologies is by using sub- and supercritical fluids. The polymer made of from phenylpropane units (p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol), the building block of lignin in plants can be converted to low molecular weight compounds using sub- and supercritical fluid technology with diverse applications including carbon fiber production. Hence, this paper aims to review on the lignin extraction from lignocellulosic biomass using sub- and supercritical fluid technology as precursor for carbon fiber production.
The utilization of renewable resource such as biomass in the production of green materials as an alternative to petrochemistry is increasing due to the depleting fossil resources and the increasing CO2 emission. The present study focused on the use of tetraethoxysilane (TEOS) and dodecyltriethoxysilane (DTES) to modify surface of nanocellulose. One-pot method provides a facile and convenient route for the fabrication of hydrophobic nanocellulose-silica film as a renewable material for the water resistant packaging application. Morphological characterization of the hydrophobic nanocellulose-silica (NC-SiO2-DTES) film showed well self-assembled DTES modified silica spherical nanoparticles with an average particle size of 126 nm over the nanocellulose film. The NCSiO2-DTES film exhibited hydrophobic and superoleophilic properties simultaneously. It also performed chemical durability with an excellent hydrophobic property over a wide range of pH values. This approach is an alternative way to improve the hydrophobicity of nanocellulose films and can be applied in water resistant packaging.
This study focused on the synthesis of copper/carbon (Cu/C) composites through hydrothermal treatment of copper (II) acetate in the presence of xylose. The effect of the Cu content in the Cu/C composite on its electrochemical properties was investigated. The reduction of Cu2+ (CuO) to Cu1+ (Cu2O) and Cu0 was observed during the hydrothermal reaction. The structure, surface morphology and metal dispersion of the Cu/C composites with and without carbonization treatment at 550°C for 1 h were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, respectively. The electrochemical properties of the Cu/C composites, in terms of cyclic voltammograms and galvanic charge/discharge, were investigated. The Cu/C composite formed with a 10 wt.% Cu loading by the one-step hydrothermal treatment at 190°C for 24 h presented a good Cu dispersion on the carbon surface, and displayed a good charge transfer and high specific capacitance of up to 370 F/g.
Oil palm fronds (OPF) are potential resources for production of biomass-based chemicals such as furfural, levulinic acid, and 5-HMF due to its large abundance. Although there are various conventional methods for biomass conversion, they suffer from low yields as well as extreme reaction severity due to the usage of mineral acids as catalyst. A new method using subcritical alcohol can be an alternative. Hence, the aim of this study is to determine the feasibility of using subcritical alcohol for furfural production from OPF. The study will also determine the effect of reaction parameters such as reaction temperature, time, and types of alcohol towards the yield. From the study, it is concluded that high furfural yield can be achieved at milder temperature and moderate reaction time under subcritical conditions. The yield obtained is comparable with other conventional methods indicating that subcritical alcohol technology has the potential for furfural production.
The environmental footprint for microalgae based biofuel can be reduced by coupling the microalgae cultivation with wastewater treatment. In the present study, the nutrients source for microalga Chlorella vulgaris was replaced by municipal wastewater from wastewater treatment plant located at USM Engineering Campus, Penang. All cultivation experiments were conducted in 5 L photobioreactors (PBRs) under indoor condition with illumination from artificial lights and compressed-air aeration. The growth performances of microalga C. vulgaris and nutrients uptake from wastewater were monitored throughout a 13-day cultivation period. The nutrients removal efficiency (NRE) for total nitrogen (TN) and total phosphorus (TP) by microalgae are 72.1 wt% and 89.7 wt%, respectively under the optimum cultivation conditions. Subsequently, microalgae biomass was collected by flocculation method, followed by extraction of lipid and transesterified to biodiesel. It was found that the biomass collected under optimum cultivation conditions achieved a maximum biomass dry weight density (N) of 0.76 g/L (or an equivalent biomass daily productivity, P of 58.6 mg/(L･d)).
Viscosity of a solution is a convenient method to indirectly estimate the size of the solute in the solution. The current work investigates the viscosity of the solutions with different vegetable oil concentrations in two solvents, i.e., methyl ethyl ketone and tetrahydrofuran. The Huggins equation has been then applied to determine the intrinsic viscosity and the Huggins constant which are related to the size of the solute and the intermolecular interaction of solute in the solution, respectively. According to the results, intrinsic viscosities of vegetable oils increase following the order coconut oil (CO), sunflower oil (SF), and palm oil (PO). However, the intermolecular interaction is following the reverse order. This result is in accordance with our previous research on the relationship between molecular weight of triglyceride and its transesterification reaction rate in methyl ethyl ketone.
Recently, Rubber Seed Oil (RSO) has been considered as a promising potential oil source for biodiesel production. However, like other non-edible feedstocks, RSO contains a significant amount of high free fatty acids which affect the process of biodiesel production. In the present work, microwave-assisted esterification process was conducted as a pre-treatment step to reduce the high free fatty acid (FFA) content of RSO from 40.14% to less than 1%. Response surface methodology (RSM) involving central composite design (CCD) was employed in the design of experiments (DOE) and the optimization of esterification reaction. The optimum conditions were found at 60°C, with methanol to oil molar ratio of 19.94:1, H2SO4 catalyst of 7.93 wt% and reaction time of 23 min. The result shows that methanol to oil molar ratio was the most influencing parameter towards the FFA reduction followed by temperature, whereas the catalyst loading and the reaction time both were observed to be insignificantly effective.
Liquefaction of oil palm trunk (OPT) in ethylene glycol and glycerol, with H2SO4 as a catalyst, at a temperature of 150°C was conducted based on Design of Experiment (DoE) aided by software Stat-Ease Inc., Design-Expert® Version 7. A 24-1 fractional factorial design was used. The results showed that factors such as types of solvents, percentage of H2SO4 catalyst and liquefaction time influenced the final liquefaction yield. Liquefaction of OPT in glycerol gave higher amount of liquefied yield. Besides, higher percentage of H2SO4 catalyst and longer liquefaction time also gave higher liquefaction yields.
Preparation, characteristic, and activity of CuO/γ-Al2O3 as re-generable SO2 adsorbent have been studied. The model gas containing SO2 of about 2,500 mg/m3 (700 mmHg, and 27°C) was made to simulate the flue gas from combustion of algae biomass: Enteromorpha and Chlorella. Experiments were carried out in a tubular reactor electrically heated to maintain adsorption temperature of 300, 350, 400 or 450°C. Amount of adsorbent was 1, 2, 4, or 8 g, and the gas flow rate was set at 1.21 L/min (700 mmHg, and 27°C). Adsorbent with CuO content of about 7.5%-mass could adsorb SO2 successfully and release the outlet gas with a SO2 concentration to meet the national standard of SO2 emission of 750 mg/Nm3. Naturally, the more amount of adsorbent in the reactor, the more complete conversion of SO2 and the lower utilization of CuO.