Duangduen Atong

Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste

Fly ash from pulp and paper industries was used as a raw material for synthesizing zeolite catalyst. Main compositions of fly ash consisted of 41 wt%SiO2, 20 wt%Al2O3, 14 wt%CaO, and 8 wt% Fe2O3. High content of silica and alumina indicated that this fly ash has potential uses for zeolite synthesis. Fly ash was mixed with 1–3 M NaOH solution. Sodium silicate acting as silica source was added into the solution to obtain the initial SiO2/Al2O3 molar ratio of 23.9. The mixtures were then crystallized at 160°C for 24 and 72 h. Zeolites synthesized after a long synthesis time of 72 h showed superior properties in terms of high crystallinity, less impurity, and small particle size. The catalytic activities of fly ash-derived zeolites were investigated via fast pyrolysis of Jatropha wastes using analytical pyrolysis-gas chromatograph/mass spectrometer (GC/MS). Pyrolysis temperature was set at 500°C with Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Results showed that higher amounts of catalyst have a positive effect on enhancing aromatic hydrocarbons as well as decreasing in the oxygenated and N-containing compounds. Zeolite Socony Mobil-5 (ZSM-5) treated with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4%. The formation of hydrocarbon led to the high heating value of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, and ketones which cause poor quality of bio-oil to only 0.8% while suppressed N-compounds to 1.7%. Overall, the ZSM-5 synthesized from fly ash proved to be an effective catalyst for catalytic fast pyrolysis application.

Pyrolysis and gasification of landfilled plastic wastes with Ni− Mg− La/Al2O3 catalyst

Pyrolysis and gasification processes were utilized to study the feasibility of producing fuels from landfilled plastic wastes. These wastes were converted in a gasifier at 700–900 °C. The equivalence ratio (ER) was varied from 0.4–0.6 with or without addition of a Ni− Mg− La/Al2O3 catalyst. The pyrolysis and gasification of plastic wastes without catalyst resulted in relatively low H2, CO and other fuel gas products with methane as the major gaseous species. The highest lower heating value (LHV) was obtained at 800 °C and for an ER of 0.4, while the maximum cold gas efficiency occurred at 700 °C and for an ER of 0.4. The presence of the Ni− Mg− La/Al2O3 catalyst significantly enhanced H2 and CO production as well as increasing the gas energy content to 15.76–19.26 MJ/m3, which is suitable for further usage as quality fuel gas. A higher temperature resulted in more H2 and CO and other product gas yields, while char and liquid (tars) decreased. The maximum gas yield, gas calorific value and cold gas efficiency were achieved when the Ni− Mg− La/Al2O3 catalyst was used at 900 °C. In general, addition of prepared catalyst resulted in greater H2, CO and other light hydrocarbon yields from superior conversion of wastes to these gases. Thus, thermochemical treatment of these problematic wastes using pyrolysis and gasification processes is a very attractive alternative for sustainable waste management.

Fuel Gas Production by Gasification of Glycerol Waste over Perovskite-Type Oxide Catalysts

Gasification of glycerol waste which is a by-product from biodiesel production was carried out using LaNiO3 and LaCoO3 perovskite-type oxide catalysts in order to enhance the production of fuel gas while reducing tar from the process. This present work showed that perovskite-type oxide could be effectively applied for cracking of tar from gasification of glycerol waste. The perovskite catalysts were prepared by a sol-gel process using PVA. The optimum condition for synthesis of LaCoO3 and LaNiO3 perovskite oxide was identified when the precursor was mixed metal ion and PVA containing a mole ratio of metal ion to PVA monomer unit as 1:1 and dried at 120°C for 20 h. The synthesized materials were calcined at different temperature and the phases were characterized with x-ray diffraction (XRD). The results showed that the single crystalline phase of perovskite without intermediate phases was achieved from calcination at 800°C for LaNiO3 and only 700°C for LaCoO3. The specific surface areas of LaNiO3 and LaCoO3 catalysts were in the range of 2.46-5.55 m2/g and 3.13-7.68 m2/g, respectively. SEM micrographs of catalyst illustrated a fluffy and foam structure with porous network. Catalytic activity of the prepared samples was tested by conversion of glycerol waste in a fixed-bed reactor. The catalytic reaction was carried out at a temperature of 500-800°C. At high temperatures LaNiO3 appeared to be a superior catalyst which enhanced the production of favorable gaseous species. However further gas upgrading may be required because of low LHV and H2/CO ratios obtained at these conditions.

Thermal Degradation and Kinetic Characterizations of Jatropha Waste under Isothermal and Dynamic Experiments

Thermal decomposition characteristic of waste material from oil extraction of Jatropha (physic nut), including shell and kernel, was investigated using thermogravimetric analysis (TGA) and pyrolysis experiments. Effects of heating rate (5-90°C/min), reaction temperature (500-900°C) and hold time at final temperature (3-15 min) on the feature of thermogram, kinetic parameters as well as product distribution were evaluated. Thermal conversion of this residue composed of cellulose, hemicellulose, and lignin degradation steps with maximum weight losses around 250 to 450°C. The order of reaction increased with temperature from 0.28 at 250°C to 0.81 at 450°C. The activation energies ranging from 105-184 kJ/mol depend on the stage of devolatilization. The amount of gas product increased with temperature with the expense of reducing char and liquid from secondary heterogeneous cracking reactions. More than 14% of hydrogen in residue was converted to H2 during pyrolysis at 900°C. Major hydrocarbon gases are those of C4+ species with measurable amount of CH4 and C2 derivatives. Increase in reaction temperature can lead to a noticeable increase of hydrogen and hydrocarbon gas yields. Addition of catalyst and steam would promote the formation of fuel gas from this waste material.

Physicochemical Properties of Carbons Prepared from Physic Nut Waste by Phosphoric Acid and Potassium Hydroxide Activations

Char derived from pyrolysis of physic nut waste at 400-800°C was used for the preparation of activated carbon by chemical impregnation of phosphoric acid and potassium hydroxide. The original char exhibited the BET surface area in the range of 120-250 m2·g-1. The surface area increased to 480 and 532 m2·g-1 when activated with H3PO4 and KOH, respectively. Equilibrium adsorption data was found to be best represented by the Langmuir isotherm with maximum monolayer adsorption capacity of 560.13 mg·g-1 at 30°C. The adsorption capacity of the physic nut residue activated carbon was comparable to commercial activated carbon.

Comparison on Pore Development of Activated Carbon Produced from Scrap Tire by Potassium Hydroxide and Sodium Hydroxide for Active Packaging Materials

Activated carbons were prepared by chemical activation from scrap tire with two chemical reagents, NaOH and KOH. The activation consisted of different impregnation of a reagent followed by carbonization in nitrogen at 700°C. The resultant activated carbons were characterized in terms of BET surface area, methylene blue adsorption and iodine number. The influence of each parameter of the synthesis on the properties of the activated carbons was discussed, and the action of each hydroxide was methodically compared. It is the first time that preparation parameters and pore texture characteristics are simultaneously considered for two closely related activating agents of the same char precursor. Whatever the preparation conditions, it was shown that KOH led to the most microporous materials, having surface areas and adsorption properties (methylene blue adsorption and iodine number) higher than those obtained with NaOH, which was in agreement with some early works. However, the surface areas, methylene blue adsorption and iodine number obtained in the present study were much higher than in previous studies, up to 951 m2/g, 510 mg/g and 752 mg/g, respectively, using scrap tire waste char:KOH equal to 1:1. The thorough study of the way each preparation parameter influenced the properties of the final materials bought insight into the activation mechanisms. Each time it was possible; the results of scrap tire waste chemically activated with hydroxides were compared with those obtained with anthracites; explanations of similarities and differences were systematically looked for.

Bimetallic LaNi1-xCoxO3 (x=0, 0.3, 0.5, 0.7, and 1) Perovskite Catalysts for Tar Reforming to Syngas

Perovskite-type oxide with transition metal as active site presented a promising potential catalyst for tar elimination in gasification process. LaNi1-xCoxO3 (x= 0, 0.3, 0.5, 0.7, and 1) were prepared by sol-gel method. The XRD profiles of the calcined catalysts revealed the mixed metal oxide forms including LaNiO3 and LaCoO3 rhombohedral structures. Good dispersion of La, Ni, and Co with homogenous structure was observed in synthesized catalyst. The particle size and surface area were in the range of 12.64-21.86 μm and 3.89-11.69 m2 /g, respectively. Activity of prepared catalysts on tar elimination was carried out using steam reforming of toluene as tar model compound at 500, 600, 700, and 800°C. Product distributions obtained from reforming reaction with LaNi1-xCoxO3 were between 40.24-88.84% of gas, 10.99-59.59% of liquid, and 0.15-0.17% of solid. Conversion to CO and H2 were found to increase with the reaction temperature. The maximum carbon and hydrogen conversion to syngas, CO and H2, of approximately 78.42% and 83.49% with acceptable heating value were occurred at 800oC using LaNiO3 as catalyst. Crystal structure of used catalysts clearly showed destruction of perovskite structure and transformation to metallic Ni and Co at effective temperature.

Enhanced Microwave Induced Thermochemical Conversion of Waste Glycerol for Syngas Production

Glycerol waste from biodiesel production can be converted to syngas (CO+H2) via a thermochemical conversion process. In this study, microwave was used to initiate a glycerol conversion reaction in a specially fabricated quartz tube reactor with a silicon carbide bed as the microwave absorber. A nickel-based catalyst and steam were added to the reacting bed to enhance production of hydrogen. By adjusting the microwave power level from 110 to 880 watt (W), the reaction temperature of 500°C to more than 1400°C could be rapidly achieved within a few minutes, which is much faster than heating by conventional furnaces. The gasification reaction commenced by feeding raw material continuously through the hot silicon carbide bed at a rate of 1 g/min with the O2 to fuel ratio varying from 0-0.25. The overall time for each trial was 20-30 minutes including preheating of the bed material. In contrast to typical biomass gasification, char and tar yields were small in most runs. In general, glycerol waste yielded higher syngas when compared with pure glycerol conversion. Complete conversion to gas product may be achieved at a power level of 440W. The maximum syngas production from glycerol waste without a catalyst was more than 23.98 L over 20 min run at 660 W with 0.25 O2 to fuel ratio. Overall content of other hydrocarbon gases was around 3-28 vol.% depending on operating conditions and raw material. Lower heating values (LHV) of product gas for glycerol waste were much higher for runs at 1.0 L/min carrier gas flow, ranging from 3.75-17.64 MJ/m3 while relatively stable LHV of 1.96-5.88 were obtained from 2.0 L/min flow. The addition of a catalyst significantly increased gas production at lower wattage runs where overall conversions were comparable to those of higher wattage experiments without catalysts. The maximum total conversion and LHV were obtained from 1%Ni/SiC catalyst at a reaction temperature of 600°C (330W) and no external O2 with a gas product heating value of 9.18 MJ/m3 and 1.32 H2 to CO ratio. From these results, the novel microwave-induced heating technique can be considered as an efficient option for conversion of glycerol waste via the gasification process to acceptable quality syngas.

The effect of alkali on the product distribution from black liquor conversion under supercritical water

ABSTRACT Lignin in chemical pulping waste, or black liquor (BL), can be converted into various products via supercritical water gasification (SCWG). However, the inherited alkaline contents from the pulping chemicals may affect the product yields and properties. In this research, the influence of the residual alkali on the product distribution via SCWG of soda BL and kraft BL was evaluated. The SCWG was performed in a batch quartz reactor for 10 min at various temperatures (673, 773 and 873 K) and pressures (250, 300 and 400 bar). The highest hydrogen (H2) production occurred at 873 K for the soda BL. The water–gas shift reaction with sodium ions played an important part in the H2 production, while only small amounts of methane and carbon monoxide were detected. Hydrocarbons, carboxylic acids and esters were the dominant substrates in the liquid products, which denoted the potential of this method for bond cleaving of the lignin macromolecule. As a result, BL, which typically contains alkali salt, was an appropriate feedstock for the SCWG reaction to produce renewable fuel. This method not only has a positive influence on the generation of value added products from highly corrosive waste but also helps avoid some technical problems commonly encountered with direct firing in a recovery boiler.

Steam reforming of tar model compound using Pd catalyst on alumina tube.

Gasification processing of biomass as a renewable energy source generates tar in the product gas. Tar leads to foul-up of the process equipment by corrosion and deposit formation. Catalytic elimination of tars is a crucial step to improve fuel gas quality from the process. In this study, a palladium catalyst on alumina (Pd/Al2O3) was used in steam reforming of benzene as a biomass gasification tar model compound. The reaction was carried out in a laboratory-scale tube reactor made of stainless steel to study the effect of reaction temperature, catalyst loading, quantity of palladium catalyst tubes, steam to carbon ratio (S/C), and residence time on catalytic performance and stability. Pd/Al2O3 showed high efficiency of benzene decomposition and enhanced the formation of fuel gas. Hydrogen and carbon conversions increased with reaction temperature. Although the benzene concentration increased from 2000 to 5000 mg/l, the catalytic performance at 600 °C and 800 °C was similar. 1.0 wt% Pd/Al2O3 showed excellent catalytic activity with the highest hydrogen and carbon conversions of 83% and 81%, respectively at 800 °C. This result is attributed to the smooth surface of the palladium, as noted from scanning electron microscopy imaging. An S/C of 2 provided the highest conversion. The addition of catalyst from four and seven tubes did not result in any great difference in terms of benzene cracking efficiency. The fourth cyclic usage of 1.0 wt% Pd/Al2O3 exhibited a higher conversion than that of 0.5 wt%.