Okorn Mekasuwandumrong

Formation of CoAl 2 O 4 nanoparticles via low-temperature solid-state reaction of fine gibbsite and cobalt precursor

Nanocrystalline cobalt aluminate (CoAl2O4) was synthesized by the solid-state reaction method with cobalt chloride hexahydrate (CoCl2 ċ 6H2O) as the source of Co and gibbsite (Al(OH)3) as the source of Al, respectively. The effects of particle size of the starting fine gibbsite (0.6 and 13 µm) and calcination temperatures (450, 550, and 650°C) on the properties of CoAl2O4 were investigated by means of X-ray diffraction (XRD), thermogravimetry analysis and differential thermal analysis (TG/DTA), X-ray photoelectron spectroscopy (XPS), UV-visible absorption spectroscopy (UV-Vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Increasing of calcination temperature promoted the insertion amounts of Co2+ in alumina matrix in CoAl2O4 structure, which resulted in the brighter blue particles and increasing of UV spectra band. The lowest temperature for the formation of nanocrystalline CoAl2O4 particles was 550°C for the solid-state reaction of cobalt chloride and 0.6 µm fine gibbsite.

TRANSESTERIFICATION OF PALM OIL AT NEAR-CRITICAL CONDITIONS USING SULFONATED CARBON-BASED ACID CATALYST

This study aims to investigate the production of biodiesel by transesterification of purified palm oil (PPO) at near-critical conditions using a carbon-based catalyst, synthesized by incomplete carbonization of naphthalene in sulfuric acid. The catalyst shows good activity for the reaction; with the most suitable condition found to be at a methanol-to-PPO molar ratio of 12:1, a carbon-based catalyst-to-PPO mass ratio of 0.5 wt.%, a reaction time of 30 min, and a reaction temperature of 270°C. This resulted in a FAME yield of about 95%. However, FAME yields were found to decrease after each reaction cycle from around 95% in the first to 61% in the second cycle, and to only 45% in the third cycle, as a result of catalyst deactivation due to acid leaching.

CHARACTERISTICS OF ACTIVATED CARBONS DERIVED FROM DEOILED RICE BRAN RESIDUES

This research focuses on investigation of the characteristics of activated carbons derived from deoiled rice bran residues, a major by-product of the rice bran oil industry. The preparation of activated carbons consists of two steps; the first step is the pre-carbonized acid-leaching (H2SO4) process and the second step is chemical activation using H3PO4 or ZnCl2 as an activating agent for the development of the micropores. The effects of preparation parameters including the types of activating agent (H3PO4 and ZnCl2) and temperature of chemical activation were studied. The physical properties of samples were examined by means of XRD, SEM, TGA, and N2-physisorption. The maximum BET surface areas obtained from ZnCl2 and H3PO4 activation are 1404 m2/g and 1187 m2/g, respectively. All activated carbons exhibited mostly microporous and partly mesoporous structures. These experimental results indicated that deoiled rice bran residues can be a promising economical source for the preparation of activated carbon.

One-Step FSP Synthesis of Nanocrystalline Fe/Al2O3 and Fe-Ce/Al2O3 Catalyst for CO2 Hydrogenation Reaction

Nanocrystalline Fe/Al2O3 and Fe-Ce/Al2O3 catalysts doped with various amounts of cerium were prepared using the one-step flame spray pyrolysis (FSP) technique. The characterization of the catalysts was measured by several methods such as X-ray diffraction, nitrogen physisorption and hydrogen temperature programmed reduction (H2-TPR) techniques. The results revealed that the FSP-made catalyst exhibited the characteristic pattern of FeAl2O4 phase without any phases of aluminum or iron oxide. In addition, cerium (Ce) dopant did not alter crystal structure at low content. However, 7 wt% content of cerium dopant resulted in the formation of ceria (CeO) and iron oxide (Fe2O3) phase. The catalytic performance of the FSP-made catalyst was tested in carbon dioxide hydrogenation for selective production of long chain hydrocarbon, and was compared to conventional impregnation-made catalysts. In the comparison, the FSP-made catalyst exhibited lower catalytic activity but possessed a higher long chain hydrocarbon selectivity. After doping with Ce, the catalytic activity was improved while the hydrocarbon selectivity was decreased and shifted to the short chain hydrocarbon product. In the case of conventional-made catalysts, the activity remained unchanged but the hydrocarbon selectivity was decreased. Among all catalysts, the FSP-made Fe-Ce/Al2O3 catalyst with 3% Ce-promoted catalyst exhibited the best performance in terms of selectivity to long chain hydrocarbon.

Grafting of TiO2 on PMMA Film and Reusability in Photodegradation of Organic Dye

Grafting TiO2 on PMMA was studied by atom-transfer radical-polymerization (ATRP). Each step in grafting process was monitored by fourier transform infrared spectroscopy (FT-IR), 1H NMR and 13C NMR spectra. The glass temperature of grafted-PMMA film was determined by using differential scanning calorimetry (DSC). The morphology and bulk composition were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The surface composition was characterized by X-ray photoelectron spectroscopy (XPS). As results, a novel method of grafting TiO2 on PMMA was successfully grafted and confirmed in various techniques. The photocatlytic activity was evaluated under UV and visible light irradiation. The reusability of TiO2-g-PMMA films was studied in details.

Solvothermal-Derived Nanocrystalline TiO2 Supported Co Catalysts in the Hydrogenation of Carbonmonoxide

Nanocrystalline TiO2 with the average crystallite sizes of 9 and 18 nm were synthesized by the solvothermal method and employed as supports for preparation of Co/TiO2 catalysts for CO hydrogenation reaction with various Co loadings between 5-20 wt%. For a similar Co loading, the use of larger crystallite size TiO2 resulted in higher higher CO hydrogenation activities with no influences on the product selectivities. However, an optimum amount of cobalt loading that maximized CO hydrogenation activity of Co/TiO2 was determined to be at ca. 15 wt.% for both TiO2 crystallite sizes.