• Energy Research

This study experimentally investigates the gasification of nickel-preloaded oil palm biomass as an alternative catalytic approach to produce clean syngas. To eliminate the use of catalyst support, nickel was added directly to the oil palm mesocarp fiber via ion-exchange using an aqueous solution of nickel nitrate. Nickel species was found to disperse very well on the biomass at a nano-scale dispersion. The presence of the finely dispersed nickels on biomass enhanced syngas production and reduced tar content in the producer gas during the air gasification of biomass. It is believed that nickel particles attached on the biomass and its char promote the catalytic cracking of tar on their surface and supply free radicals to the gas phase to enhance the radical-driven gas-phase reactions for the reforming of high molecular weight hydrocarbons. The unconsumed nickel-containing char shows great potential to be re-utilised as a catalyst to further enhance the destruction of tar components in the secondary tar reduction process. 

The investigation on the adsorption of metal from aqueous solution onto a biomass is important for several reasons. First, biomass has been widely used as an economical sorbent to remove heavy metals from industrial wastewater. Second, studies have shown that impregnation of metals onto a biomass helps improving thermal conversion of the biomass, for example, by reducing the yields of tar and char and thus enhancing the formation of syngas during biomass gasification. The produced metal-loaded char from thermal conversion of metal impregnated-biomass on the other hand, can be re-used as a catalyst for various reactions such as water-gas shift reaction. In this study, we examine the adsorption of Nickel from aqueous solution onto oil palm mesocarp fiber by varying important parameters such as pH and initial metal concentration. The kinetic study shows that the adsorption of Nickel follows the pseudo-second order kinetic model. Our study also reveals that Nickel disperses well into nano-size particles on the oil palm mesocarp fiber, suggesting the suitability for carrying out thermal conversion of Nickel-loaded oil palm mesocarp fiber in the future. The adsorption of Nickel is lower but sufficient enough to be used as catalyst in biomass thermochemical processes.

Abstract Ni-based catalysts are prone to be deactivated by carbon deposition. This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al2O3 catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production. At a low S/C ratio of 1, the catalytic activity of Ni/α-Al2O3 was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface. While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al2O3 in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion.

Abstract In this work, sugarcane bagasse waste (SBW) was used as a lignocellulosic precursor to develop a high-surface-area activated carbon (AC) by thermal treatment of the SBW impregnated with KOH. This SBW activated carbon (SBWAC) was characterized by crystallinity, porosity, surface morphology and functional groups availability. The SBWAC exhibited Type I isotherm which corresponds to microporosity with high specific surface area of 709.3 m2/g and 6.6 nm of mean pore diameter. Further application of SBWAC as an adsorbent for methylene blue (MB) dye removal demonstrated that the adsorption process closely followed the pseudo-second order kinetic and Freundlich isotherm models. Conversely, a thermodynamic study revealed the endothermic nature and spontaneity of MB dye adsorption on SBWAC with high acquired adsorption capacity (136.5 mg/g). The MB dye adsorption onto SBWAC possibly involved electrostatic interaction, H-bonding and π–π interaction. This work demonstrates SBW as a potential lignocellulosic precursor to produce high-surface-area AC that can potentially remove more cationic dyes from the aqueous environment.

Abstract Bark constitutes an important part of any woody biomass to be used for the production of second generation biofuels and chemicals. Pyrolysis followed by biorefinery is a promising technology for the efficient utilisation of all components from a woody crop. While significant efforts have been devoted to the investigation of the pyrolysis characteristics of wood, relatively less is known about the pyrolysis behaviour of bark. This study aims to clarify the effects of temperature on the yields and composition of bio-oil from the pyrolysis of eucalypts bark. The bark of mallee, a type of eucalypt grown for soil amendment in Western Australia, was pyrolysed between 300 and 580 °C at fast heating rates in a fluidised-bed pyrolysis unit. The bio-oil liquid products separate into two phases. The bio-oil liquid products were analysed by GC–MS, Karl-Fischer titration, UV-fluorescence spectroscopy, ICP-OES and thermogravimetric analysis (TGA). These results are compared, when appropriate, to those obtained from the wood fraction.

The combustion of bituminous coal, bio-oil, and their slurry mixtures were performed under air atmosphere using Thermogravimetric Analyzer (TGA). All samples were run from room temperature to 110°C and held for 10 minutes before the temperature was ramped to 1100°C and held again for 10 minutes at 1100°C at the heating rate of 10°C/min and gas flow rate of 50mL/min. Kinetic evaluation was conducted using a simple Arrhenius-type kinetic model with first-order decomposition reaction. Apparent activation energy, Ea, and pre-exponential factor, A, were calculated from the modelling equation. Results reveal that the reactivity of CBS fuel is higher than a single coal fuel to which the addition of bio-oil helps to increase the combustion performance of the blends. The optimum fuel ratio appears at 50:50 ratio with equal contribution of coal and bio-oil properties that contribute to the increase in volatile matter causing maximum combustion rate achievable at much lower temperature compared to single coal fuel.

This study investigated the characteristics of NO emissions during oxy-coal combustion with wet-recycle, especially in the presence of high H2O concentrations. The oxy-combustion was carried out using two types of coal, namely Leiyang (LY) anthracite and Zhundong (ZD) bituminous coals, inside a 24 kW drop tube furnace under different O2/CO2/H2O atmospheres. The results showed that the NO conversion increased with decreasing CO2 concentration from 70% to 30% and decreased with increasing H2O concentration from 10% to 40%. Under the experimental conditions employed in this study, the fuel-N conversion for both LY and ZD coals under the oxy-coal wet recycled combustion was lower than that under the oxy-coal dry recycled combustion. The results indicated that H2O and CO2 showed a competitive effect on NO emissions, though both of them have positive effect on NO reduction. In order to investigate the effects of H2O/CO2 on recycled NO, oxy-coal combustion experiments were also performed with the initial additio...

Abstract Bio-oil from the fast pyrolysis of biomass can be converted to solid carbon materials, chemicals and syngas by various thermochemical conversion methods. As a first step in all of these processes, bio-oil undergoes drastic components changes due to its exposure to the elevated temperature. Understanding the effects of heating rate on bio-oil transformation during its pyrolysis is therefore crucial for effective utilization of bio-oil. In this study, a bio-oil sample produced from the fast pyrolysis of rice husk at 500 °C was pyrolyzed in a fixed-bed reactor at temperatures between 300 and 800 °C at three different heating rates: fast (≈200 °C/s), medium (≈20 °C/s), and slow (≈0.33 °C/s). In addition to the quantification of coke and tar yields, the tar was characterized with an ultraviolet (UV) fluorescence spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Our results indicate that slow heating rates promote polymerization of bio-oil components, particularly at low temperatures ( 500) were also promoted at fast heating rates via the more intense secondary reactions.