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Kaewpengkrow P.,Chulalongkorn University | Atong D.,National Metal and Materials Technology Center | Sricharoenchaikul V.,Chulalongkorn University
Bioresource Technology | Year: 2014

The objective of this study was to catalytically upgrade bio-oil from organic vapors of Jatropha wastes using Py-GC/MS. Catalytic testing included Al2O3, ZrO2, TiO2 (rutile, T1) and TiO2 (anatase, T2) supporter catalysts modified with transition metals (Pd, Ru or Ni) by impregnation method. In non-catalytic runs, the main vapor products were fatty acids (60.74%). With the presence of Al2O3 based catalysts, carboxylic acids were obviously reduced to 0.76-19.61% while hydrocarbons were the main products (42.00-64.06%). Comparing among four supporters, total hydrocarbon yields increased with presence of all catalysts. Higher yields were obtained by T2>Al2O3>CA>NiCA>RuCA catalysts. Al2O3 and T2 supports were the most effective for increased hydrocarbons while decreased oxygenated compounds (15%) which is one of the primary aims of this study. The result indicating that high surface area resulted in better catalytic activity but also adversely promoted N-compounds. Therefore these catalysts can be applied to improve properties of pyrolytic products. © 2014 Elsevier Ltd.

Niranatlumpong P.,National Metal and Materials Technology Center | Koiprasert H.,National Metal and Materials Technology Center
Surface and Coatings Technology | Year: 2011

The coating microstructures of electric arc sprayed NiCrBSi-WC and NiBSi-WC coatings were investigated. It was found that, for NiCrBSi-WC coating, the resulting microstructure consists of NiCr, NiCrW solid solutions and WC/W2C as major phases. For NiBSi-WC coating, the major phases are Ni, NiW solid solution and WC/W2C. Some B is present within the coatings as inclusions. The amount of WC/W2C was reduced in both coatings due to the formation of the NiCrW and NiW solid solutions containing a large amount of W. Precipitation of W-rich phase from NiCrW and NiW solutions was also observed but the transformation is restricted by the fast cooling rate characteristic of the spraying process. There is more dissolution of WC/W2C into the matrix in NiBSi-WC coating resulting in a greater reduction in the microhardness of this coating. Wear test results, however, show that even though the NiBSi-WC coating possesses lower microhardness, it is more effective against dry sliding wear than the NiCrBSi-WC coating, owing to better metallurgical bonding between the matrix and the carbide as a result of WC/W2C dissolution. © 2011 Elsevier B.V.

Eswar Prasad K.,Indian Institute of Science | Chollacoop N.,National Metal and Materials Technology Center | Ramamurty U.,Indian Institute of Science
Acta Materialia | Year: 2011

The subsurface microhardness mapping technique of Chaudhri was utilized to determine the shape, size and distribution of plastic strain underneath conical indenters of varying semi-apex angles, α (55°, 65° and 75°). Results show that the elastic-plastic boundary under the indenters is elliptical in nature, contradicting the expanding cavity model, and the ellipticity increases with α. The maximum plastic strain immediately under the indenter was found to decrease with increasing α. Complementary finite-element analysis was conducted to examine the ability of simulations to capture the experimental observations. A comparison of computational and experimental results indicates that the plastic strain distributions as well as the maximum strains immediately beneath the indenter do not match, suggesting that simulation of sharp indentation requires further detailed studies for complete comprehension. Representative strains, εr, evaluated as the volume-average strains within the elastic-plastic boundary, decrease with increasing α and are in agreement with those estimated by using the dimensional analysis. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Papong S.,National Metal and Materials Technology Center | Malakul P.,National Metal and Materials Technology Center | Malakul P.,Chulalongkorn University
Bioresource Technology | Year: 2010

In this study, the life-cycle energy and environmental assessment was conducted for bioethanol production from cassava in Thailand. The scope covered all stages in the life cycle of bioethanol production including cultivating, chip processing, transportation and bioethanol conversion. The input-output data were collected at plantation sites and ethanol plants which included materials usage, energy consumption, and all emissions. From the energy analysis, the results show that cassava-based bioethanol has a negative net energy value with an energy ratio was less than 1, indicating a net energy loss. For the environmental performance, the results show that throughout the life cycle of bioethanol, the conversion stage contributes most to the environmental impacts which is due to the use of coal for power and steam production in the bioethanol plants. It is suggested that a partial substitution of coal with biogas produced from existing wastewater treatment could lead to a significant reduction in the environmental impact. © 2009 Elsevier Ltd. All rights reserved.

Yoosuk B.,National Metal and Materials Technology Center | Tumnantong D.,Chulalongkorn University | Prasassarakich P.,Chulalongkorn University
Fuel | Year: 2012

Unsupported sulfide catalysts are a potentially promising approach towards furthering the understanding and development of a better heterogeneous catalytic system capable of performing the hydrodeoxygenation (HDO) of bio-oil proficiently under mild and short reaction conditions and times, respectively. Amorphous unsupported Ni-Mo sulfide, prepared from ammonium tetrathiomolybdate (ATTM) by a one step hydrothermal method, is already sulfided and so does not need a sulfidation step. The addition of the Ni promoter prevents the growth of Mo sulfide particles and causes a reduction in the surface area and a change in the pore characteristics as the amount of added Ni was increased. Ni sulfide alone (no Mo) showed a completely different morphology and properties compared to those of the Mo-containing sulfides, with or without the copresence of Ni. The activity and selectivity of catalysts was investigated using phenol as a model substrate in the direct-deoxygenation (DDO) and hydrogenation (HYD) reactions in a HDO system. The Ni-Mo sulfide catalyst with optimal Ni amount had a significantly higher phenol conversion efficiency (96.2 mol%), and favored a HYD pathway, than that seen for the Mo sulfide one (71.0 mol%) that favored a DDO pathway. H2-temperature programmed desorption (TPD) suggested that this synergy was mainly derived from a change in the quality and not the number of the active sites. The synergetic effect was a function of the stoichiometric composition with the maximum synergetic effect being obtained at a Ni/(Mo + Ni) ratio of 0.3. This could result from the high dispersion of the active species and the generation of a more active Ni-Mo-S phase. © 2011 Elsevier Ltd. All rights reserved.

Methacanon P.,National Metal and Materials Technology Center | Krongsin J.,National Metal and Materials Technology Center | Gamonpilas C.,National Metal and Materials Technology Center
Food Hydrocolloids | Year: 2014

At present, the available information on recovery of pectin from pomelo peel is still limited. Moreover, the extraction parameters depend on the raw material and the preferred functional properties of the pectin. Therefore, in this study, pomelo pectin extraction parameters affecting pectin yield and its properties were investigated by the single factor and central composite design methods. It was found that pH played an important role in controlling pectin yield and its side chain composition, particularly arabinose and galactose. In addition, it is worth pointing out that the neutral polysaccharide side chains of the extracted pomelo pectin mainly consisted of arabinose instead of galactose which was typically found as a principal neutral sugar in those of citrus and apple pectins. Apart from pH, the extraction temperature also showed strong influence on the yield and molecular weight (MW), but not on the degree of esterification (DE). Under the suggested optimal condition, the pectin yield was measured to be 23.19% and its DE and MW values were approximately 57.87% and 353kDa, respectively. Rheological experiments showed that the pomelo pectin dispersions behaved as a viscoelastic solution below 1%w/v and formed a weak gel network at higher concentrations. In addition, the flow behavior of the dispersions below 0.4 %w/v was Newtonian but they exhibited a pseudoplastic with shear thinning characteristic at higher concentrations. © 2013 Elsevier Ltd.

Danwittayakul S.,National Metal and Materials Technology Center | Jaisai M.,Asian Institute of Technology | Dutta J.,Asian Institute of Technology | Dutta J.,Sultan Qaboos University
Applied Catalysis B: Environmental | Year: 2015

Zinc oxide/zinc tin oxide (ZnO/ZTO) nanocomposites were synthesized on porous ceramic support using a simple and economical hydrothermal technique for photocatalytic degradation of organic dyes. One dimensional ZnO nanorods were grown epitaxially on ZnO nanoparticles seeded substrates in a chemical bath with different growth solution concentrations followed by the synthesis of zinc tin oxide (ZTO) in an autoclave. Comparison of photocatalytic activity of pure ZnO nanorod catalysts with different dimensions on the degradation of methylene blue showed that ZnO nanorods (ZnO20mM) with the highest specific surface area (45m2g-1) are 13% more active than those with lower surface areas ZnO nanorod catalysts (ZnO1mM, ZnO5mM and ZnO10mM; 20-39m2g-1). To further enhance photocatalytic activity, we composited ZnO with ZTO and found that ZnO/15ZTO can be a better photocatalyst improving 16% degradation efficiency attributed to the reduction of electron-hole recombination by charge carrier separation in the composites. Moreover, ZnO/15ZTO showed 50% Photocatalytic degradation efficiency and 77% COD removal of textile waste water when irradiated by sunlight. ZnO/ZTO monolith shows much promise to be an attractive photocatalyst for solar photocatalytic application. © 2014 Elsevier B.V.

Tantirungrotechai J.,Center for Catalysis | Thepwatee S.,Center for Catalysis | Yoosuk B.,National Metal and Materials Technology Center
Fuel | Year: 2013

Sr/MgO catalysts for biodiesel production were synthesized by the wet impregnation method. The formation of basic sites on the catalysts was investigated by thermal analysis, XRD, and Hammett indicator method. The calcination temperature and Sr/MgO molar ratio affect the structure as well as the catalytic activities. Among the catalysts tested, the best performance catalyst was prepared with a 0.10 Sr/MgO molar ratio and a calcination temperature of 600 °C. This catalyst had a base strength in the range of 15.0-18.4 and was also active for biodiesel synthesis at room temperature. The catalytic activities under various reaction variables were also evaluated. The biodiesel yield of 93% was achieved within 30 min from the transesterification of soybean oil with methanol at 65 °C using 5 wt.% loading of the synthesized catalyst and methanol to oil molar ratio of 12:1. © 2013 Elsevier Ltd. All rights reserved.

Regonini D.,University of Bath | Regonini D.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Bowen C.R.,University of Bath | Jaroenworaluck A.,National Metal and Materials Technology Center | Stevens R.,University of Bath
Materials Science and Engineering R: Reports | Year: 2013

This paper reviews the state of the art of anodized titanium dioxide nanotubes (TiO2 NTs), with an emphasis on the growth mechanism leading to their formation and the effect of heat treatment on their structure and properties. The discussion is primarily focused on TiO2 NTs grown in fluoride containing electrolytes, although the mechanism of formation of NTs in fluoride free solutions via Rapid Breakdown Anodization (RBA) is briefly covered. After an initial overview of progress made on the synthesis of anodized TiO2 NTs the review provides an analysis of the factors affecting the anodizing process (fluoride concentration, electrolyte type, applied potential and anodizing time). Details of the current-time transient, the chemistry of the process and the chemical composition of the anodic films are described which provide key information to unveil the nanotube growth mechanism. The main debate is whether NTs growth in fluoride containing solutions occurs via field-assisted plastic flow (i.e. a constant upward displacement of the oxide to form the NTs) combined with field-assisted ejection of the Ti 4+ ions (i.e. ions are ejected into the electrolyte without oxide formation) or via field-assisted dissolution (i.e. preferential dissolution at the pore base where the field is stronger) or whether both processes play a role. Whenever anodization takes place in organic solutions the experimental evidence supports the plastic flow model, whereas in aqueous media field-assisted (and chemical) dissolution occur. The mechanism of rib formation on the walls of the NTs is also reviewed, and it clearly emerges that the applied potential and water content in the electrolyte are key factors in determining whether the NTs are ribbed or smooth. There also appears to be a relationship between the presence of ribs and the evolution of oxygen bubbles at the anode. The impact of thermal treatment on the properties of the NTs is also described. A variety of crystalline structures are present in the NTs (i.e. anatase or rutile), depending on the heat treatment temperature and atmosphere and the resulting electrical properties can be varied from dielectric to semi-metallic. A heat treatment temperature limit ranging from 500 to 800 C exists, depending on preparation history, above which sintering of nanoscale titania particles occurs leading to collapse of the NTs structure. Future work should aim at using annealing not just to influence the resulting crystalline phase, but also for generating defects to be exploited in specific applications (i.e. photocatalysis, water splitting and photovoltaics). © 2013 Elsevier Ltd. All rights reserved.

Yoriya S.,National Metal and Materials Technology Center
International Journal of Electrochemical Science | Year: 2012

This work presents the formation of TiO2 nanotube arrays fabricated by electrochemical anodization of titanium in the fluoride-based diethylene glycol (DEG) electrolyte, with an aim towards elucidating how variation of inter-electrode spacing affects changes in electrolyte properties and corresponding morphological features of TiO2 nanotube array films. Enlargement of nanotube morphologies of DEG fabricated nanotubes is attainable through a simplified synthesis technique and manipulation of electrolyte properties. Electrolyte conductivity and titanium concentration are found to drastically increase with decreasing anode-cathode separation. Resulting titania nanotube array morphologies also tends to increase significantly, particularly observed in intertubular spacing that increases by a factor of 15 as reducing the electrode spacing from 4.5 cm to 0.5 cm under a fixed electrolyte condition. Due to the combination effect of electrolyte properties and high field strength between the electrodes, the self-enlargement potential is believed to be a driving force for nanotube separation. The unique characteristic of discrete, well-separated nanotube structure is expected to extend and enhance the applications of anodic TiO2 nanotube array films. © 2012 by ESG.

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