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This work studied the one-step conversion of ethane (C2H6) to ethylene oxide (EO) in an AC parallel plate dielectric barrier discharge (DBD) system with two frosted glass plates under ambient temperature and atmospheric pressure. EO is directly produced from C2H6 in a single step without the requirement to separate and recycle ethylene. The effects of the applied voltage, input frequency, and O2/C2H6 feed molar ratio on the EO synthesis performance were examined. The results showed that a higher applied voltage and lower input frequency generated more highly energetic electrons, resulting in a higher current. More electrons collided with reactant gas molecules to initiate plasma reactions, increasing C2H6 and O2 conversions. The increased O2/C2H6 feed molar ratio enhanced C2H6 and O2 conversions. The optimum conditions were found to be an applied voltage of 7 kV, input frequency of 550 Hz, and O2/C2H6 feed molar ratio of 1:1, which demonstrated the highest EO selectivity (42.6%), EO yield (19.4%), and lowest power consumption per EO molecule produced (6.7 x 10-18 Ws/molecule).

This work aimed to study the preparation of cerium oxide (CeO2) used as the catalyst for biodiesel production from palm oil. The precipitation method was used in the catalyst synthesis. The effects of oxalic concentrations and stirring rates in the precipitation process were investigated. Oxalic acid was added into cerium (Ce) in ethylenediaminetetraacetic acid solution to form Ce oxalate before the Ce oxalate was calcined to obtain CeO2. The results showed that oxalic concentrations and stirring rates slightly affect the morphology of CeO2. However, these parameters considerably affect the amount of basic sites of CeO2. The basicity of CeO2 plays the main role in catalyzing the transesterification reaction for biodiesel production. When CeO2 was used as the catalyst in biodiesel production from palm oil under operating conditions using a 5% catalyst, methanol-to-oil molar ratio of 30:1, reaction temperature of 150°C, 13.8 bars, and 3-h reaction time, CeO2 obtained from 3% oxalic concentration and 400 rpm stirring rates in the precipitation process provided the highest %FAME in the range of 93.9–94.2% since it had higher basicity. In addition, the decrease in surface area of CeO2 after the use was less severe than that of basicity due to catalyst deactivation.

The study investigated the use of CeO2 extracted from monazite with calcium oxide (CaO) as a solid catalyst for biodiesel production. The wet impregnation method was used to produce CaO@CeO2 mixed-oxide catalysts with 0–50 wt.% CaO. X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, thermogravimetric analysis (TGA), and a Fourier transform infrared spectrometer (FTIR) was used to characterize the catalysts. In order to determine the optimal preparation conditions, the effect of different CaO compositions on the performance of CaO@CeO2 mixed-oxide catalysts was examined. The catalytic activity of the CaO@CeO2 catalyst for the transesterification reaction of palm oil to produce biodiesel was studied. The results show that the optimum yield of biodiesel can reach 97% fatty acid methyl ester over the 30CaO@CeO2 catalyst at the reaction conditions of 5 wt.% catalysts, methanol-to-oil molar ratio of 9:1, with a reaction temperature of 65 °C within 30 min. The results show that the high catalytic activity and stability of the CaO@CeO2 catalyst make it a promising candidate for industrial-scale biodiesel production. Further study is needed to improve the stability and efficiency of catalysts in transesterification reactions to achieve a high FAME yield using long-life-span catalysts. Moreover, it is necessary to investigate the economic feasibility of this process for application in large-scale biodiesel production. [ABSTRACT FROM AUTHOR]

The Thai domestic rare earth oxides, including cerium, lanthanum, and neodymium oxides, with the effects of calcination temperatures (500–1000 °C), were utilized as catalysts for twelve Jatropha biodiesel alternatives via an esterification reaction. This study applied life cycle assessment (LCA) methodology from well-to-wheel analysis to assess energy efficiency and the global warming impact with and without land use change. The results of the life cycle analysis showed that the Jatropha biodiesel alternatives using the La2O3 catalyst in all conditions (0.89–1.06) were found to be potential fuel substitutes for conventional diesel (0.86) in terms of net energy ratios; however, the results showed that they generated a higher global warming impact. Considering the improvement process of Jatropha biodiesel in the utilization of waste heat recovery, the Jatropha biodiesel reduced the impacts of the net energy ratios and the global warming impact by 22–24% and 34–36%, respectively. The alternative Jatropha biodiesel using the La2O3 catalyst with a calcination temperature of 600 °C was shown to be the most environmentally friendly of all the studied fuels; relatively, it had the highest energy ratios of 1.06–1.37 (with and without waste heat recovery) and the lowest total global warming impact of 47.9–70.7 kg CO2 equivalent (with land use change). The integration of the material and process development by domestic catalysts and the recovery of waste heat would improve the sustainability choices of biofuel production from renewable resources for transportation fuels in Thailand. [ABSTRACT FROM AUTHOR]

Generation of oxygen using pressure swing adsorption (PSA) has been commercialized for a few decades. However, the efficiency of the adsorption process in purifying O2 has typically dropped with operating times. In this study, the reasons for the loss of adsorption capacity of zeolite samples collected from a commercial PSA-based O2 generator were investigated. It was illustrated that the adsorption of H2O molecules on a lithium-exchanged low silica X zeolite (Li zeolite) and the replacement of Li+ with Na+ in the zeolite structure were major causes for the loss of selective adsorption of the zeolite. While the H2O molecules could be desorbed and the surface area of the adsorbent could be regained by vacuum heating at 200 °C and 90 kPa, the N2/O2 separation efficiency of the adsorbent could not be recovered. An elemental composition analysis showed that when an active Li zeolite was placed in a high salinity, wet air flow, there occurred vapor-phase ion exchange between Na+ and Li+ cations. The results from this study showed that airborne salinity in a working environment was detrimental to adsorption processes with Li zeolite as the adsorbent. [ABSTRACT FROM AUTHOR]

This study reports the mass concentrations, elemental characterization and identification of the possible sources of PM2.5 and PM10 at a suburban site in Pathum Thani, Thailand. The sampling was done from 18 February 2021 to 14 September 2021. PM2.5 concentrations were between 0.39 μg/m3 and 174.26 μg/m3, while PM10 concentration ranged from 12.75 μg/m3 to 242.02 μg/m3. The average concentration of PM2.5 in the wet season (61.96 μg/m3) in the study area exceeded the national ambient air quality standards (NAAQS). Particle-induced X-ray emission (PIXE) was used to measure the element concentrations. The main elements, namely Fe, K, Cr and Ca, in both PM2.5 and PM10 showed significantly higher concentrations in the summer season. A qualitative inter-elemental correlation analysis, principal component analysis (PCA) and cluster analysis (CA) were applied for source identification of PM2.5 and PM10. The results for the three procedures were in good agreement. Four and three factors of sources were isolated by the PCA for PM2.5 and PM10, respectively. The main sources identified by PCA were, for PM2.5, soil dust and biomass burning (32%), road dust and industrial emission (25%), vehicle and industrial emission (10%) and soil dust (9%); for PM10, road dust and industrial emission (36%), crustal and biomass burning (30%) and industrial sources (10%). [ABSTRACT FROM AUTHOR]

This paper presents a simple microwave digestion method for soil samples leading to correct determination of the rare earth elements (Ce, La, Nd, Sc), uranium (U) and thorium (Th) using inductively coupled plasma mass spectrometry (ICP-MS). Six soil samples were collected from different depths (0-0.1, 0.1-0.3, 0.3-1.0, 1.0-2.0, 2.0-3.0 and 5.0-8.0 m) in Phuket province, Thailand. The samples were decomposed using microwave-assisted acid digestion at four different acid conditions including (I) 20 mL concentrated nitric acid; (II) 20 mL concentrated hydrochloric acid; (III) mixture of 8 mL nitric acid and 12 mL hydrochloric acid; and (IV) mixture of 12 mL nitric acid and 8 mL hydrochloric acid. Instrumental neutron activation analysis (INAA) was also applied for determination of REEs, U and Th in those soil samples to compare the results. It was found that the concentrations of Ce, La, Nd, Sc, U and Th in all soil samples obtained by ICP-MS using concentrated nitric acid had acceptable agreement with INAA results. The measured concentrations of Ce, La, Nd, Sc, U and Th in the soil samples ranged within 260-461, 153-922, 87-632, 10-16, 33-134 and 156-323 mg/kg, respectively. [ABSTRACT FROM AUTHOR]

Monazite ore is mainly composed of rare earth elements (such as Ce, Nd, La, etc.). These rare earth elements are widely used in several high technology and industrial products. Thailand Institute of Nuclear Technology has performed research on the separation and purification of rare earth elements from Thai monazite ore for supporting industrial applications. In this work, the raw material, intermediate and by-product samples obtained from Thai monazite ore processing were characterized by various physicochemical techniques (WDXRF, XRD and SEM-EDS) for understanding their structural and morphological characteristics. The WDXRF analysis showed that the monazite ore sample contained primarily cerium (30.37 wt% of CeO2) which matched well with the XRD result. An increase in CeO2 concentration up to 39.19 wt% and 64.62 wt% in the intermediate mixed rare earth and cerium hydroxide cake samples were observed after alkali digestion and nitric acid leaching of monazite ore, respectively. No rare earth elements could be detected in the tri-sodium phosphate by-product. Thorium oxide at 6.34% in uranium cake sample was observed. A considerable amount of NaOH in thorium cake sample was noticed. [ABSTRACT FROM AUTHOR]

This work aimed to investigate plasma-assisted CO2 reforming of CH4 in a parallel plate dielectric barrier discharge (DBD) system for production of high H2/CO ratio syngas. The effects were studied of operating parameters (discharge frequency and applied voltage), Al2O3 and Ni/Al2O3 catalysts on the CH4 dry reforming performance in terms of reactant conversion, coke, product selectivity, energy consumption, and energy efficiency. In order to improve H2/CO ratio of the produced syngas, a high CH4/CO2 feed molar ratio of 4/1 was tested for the dry reforming of CH4. As compared to a DBD-alone system, a combined Al2O3 catalyst-DBD system operating at an applied voltage of 11 kV, a discharge frequency of 750 Hz and an Al2O3 packing of 6.4 g gave an improved H2 and CO selectivity of 79% and 28%, respectively, with a fraction of syngas of 0.97 and a relatively high H2/CO ratio of 2.4. An application of 5 wt% Ni/Al2O3 catalyst in the DBD further improved the H2 selectivity to 84% and the CO selectivity to 47%. In addition, the syngas fraction increased to 0.98 with an H2/CO ratio of 1.5, while the amount of coke decreased from 4.7 to 3.7 wt%. [ABSTRACT FROM AUTHOR]

The aim of this research was to determine the optimum parameters for synthesis and characterization of mixed rare earth hydroxide (for use as a catalyst) through co-precipitation, with sodium hydroxide as precipitation agent at pH 12. The effects of precipitation temperature (30, 60 or 100 oC) and stirring speed (400 or 600 rpm) on the chemical composition, crystal structure and surface characteristics of the catalyst were investigated. The chemical composition of the catalyst was analyzed using X-ray fluorescence (XRF), and it was composed of CeO2, Nd2O3, La2O3, and Y2O3. X-ray diffraction (XRD) studies indicated that all samples had cubic structure of CeO2. The optimal temperature and stirring speed for precipitation of mixed rare earth catalyst were 60 oC and 400 rpm, respectively, giving large specific surface after calcination at 300 oC. The high 190 m2 g-1 BET surface area and 1220 mol g-1 total basic sites were achieved, indicating small crystallite sizes and large amount of active sites in the catalyst. From the above results, the optimized catalyst is considered a promising solid catalyst for biodiesel production. [ABSTRACT FROM AUTHOR]