Jumras Limtrakul

Publications (3)4.58 Total impact

• Article: Size control of nanostructured silica using chitosan template and fractal geometry: effect of chitosan/silica ratio and aging temperature

  Thongthai Witoon, Metta Chareonpanich, Jumras Limtrakul
  [show abstract] [hide abstract]
  ABSTRACT: The uses of low cost, renewable, environmentally friendly chitosan biopolymer as the structural template to control the size of silica particles in the range of nanometer scales are attractive for their practical industrial applications. In this paper, the nanostructured silica was synthesized using sodium silicate as the silica source and chitosan as the template under mild conditions. Effects of chitosan/silica ratio and aging temperature on the formation and the control of nanostructured silica was investigated by using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), N2-sorption measurement, and transmission electron microscopy (TEM). It was found that the silica products were composed of the aggregates of primary silica nanoparticles and nanostructured silica units. At low aging temperature, the size of nanostructured silica was decreased when increasing the chitosan/silica ratio from 0.1 to 0.4. In contrast, the reverse trend was observed at the chitosan/silica ratio of higher than 0.4. The increase of aging temperature led to the formation of larger primary silica nanoparticles and nanostructured silica, and also promoted the formation of silica/chitosan composites. The fractal dimension calculated using modified FHH method found the linear correlation at two different regimes which might reflect the aggregates of silica products at different length scales. KeywordsChitosan concentration-Aging temperature-Fractal analysis-Aggregates-Nanostructured silica
  Journal of Sol-Gel Science and Technology 04/2012; 56(3):270-277. · 1.63 Impact Factor
• Article: Production of aromatic hydrocarbons from Mae-Moh lignite

  Metta Chareonpanich, Tippanakarin Boonfueng, Jumras Limtrakul
  [show abstract] [hide abstract]
  ABSTRACT: Lignite from Mae-Moh basin in Thailand was used as raw feed to produce value-added chemicals, especially aromatic hydrocarbons. It was found that the hydropyrolysis of Mae-Moh lignite in atmospheric pressure of hydrogen gas is suitable for aromatic hydrocarbon production. For the hydropyrolysis of Mae-Moh lignite at 600 °C and the heating rate of 15 °C/s, 15 wt.% (dry, ash-free basis; daf) of benzene, toluene and xylenes (BTX) and decalin, tetralin and naphthalene (DTN) was produced. To enhance the yield of aromatic fractions, the upgrading of coal volatile over HY zeolite at 500 °C was investigated. The yield of BTX and DTN was 14 wt.% (daf). The attempt was made to convert aliphatic hydrocarbons to aromatic products by reforming of aliphatic products from the above hydropyrolysis/upgrading process over H-ZSM-5 zeolite. The calculated yield of BTX and DTN after this treatment was 20 wt.% (daf).
  Fuel Processing Technology.
• Article: Effect of hierarchical meso-macroporous silica supports on Fischer-Tropsch synthesis using cobalt catalyst

  Thongthai Witoon, Metta Chareonpanich, Jumras Limtrakul
  [show abstract] [hide abstract]
  ABSTRACT: Hierarchical meso-macroporous (HS-X) silica with different mesopore diameters synthesized by using rice husk ash as a silica source and chitosan as a natural template were applied for the first time as the cobalt support for Fischer–Tropsch synthesis. Unimodal mesoporous silica (MS-X) supports with equivalent mesopore diameters to HS-X supports have also been prepared for comparison. Effects of diffusion in MS-X and HS-X supports of different particle sizes on the catalytic activity and hydrocarbon selectivity were investigated. The cobalt crystallite sizes were increased with increasing mesopore diameters, whereas the highest amount of H2 chemisorbed was found for the catalyst with the medium mesopore diameter. The HS-X supports revealed lower surface area and higher macroporosity which led to the formation of larger cobalt crystallite size and less chemisorbed H2. However, the catalytic activity was much higher for cobalt supported on HS-X silica of both small and large catalyst particle sizes. Moreover, with the large catalyst particle size, the C5+ selectivity of cobalt supported on HS-X silica was much higher than that on MS-X silica, indicating the influence of mass transfer of reactants and products in macropores of HS-X supports.Research highlight► Hierarchical meso-macroporous silica as cobalt support for Fischer–Tropsch synthesis. ► Unimodal mesoporous silica with equivalent diameters was prepared for comparison. ► Checking internal particle diffusion by using two different catalyst particle sizes. ► Hierarchical meso-macroporous silica gave higher activity and C5+ selectivity. ► Macropores diminishes mass transfer resistance of reactants and products.
  Fuel Processing Technology 92(8):1498-1505. · 2.94 Impact Factor