Achanai Buasri

Preparation and Characterization of Reduced Graphene Oxide Sheets via Water-Based Exfoliation and Reduction Methods

This research studied the synthesis of graphene oxide and graphene via a low-cost manufacturing method. The process started with the chemical oxidation of commercial graphite powder into graphite oxide by modified Hummer’s method, followed by the exfoliation of graphite oxide in distilled water using the ultrasound frequency from a laboratory ultrasonic bath. Finally, the oxygen functional groups on exfoliated graphite oxide or graphene oxide were eliminated by stirring in hot distilled water at 95°C, as a replacement for highly toxic and dangerously unstable hydrazine. The results assured that stirring in hot distilled water could give the product of graphene or reduced graphene oxide. The samples were characterized by FTIR, XRD, TGA, Raman spectroscopy, SEM, and TEM methods.

Biodiesel production from waste cooking palm oil using calcium oxide supported on activated carbon as catalyst in a fixed bed reactor

A reactor has been developed to produce high quality fatty acid methyl esters (FAME) from waste cooking palm oil (WCO). Continuous transesterification of free fatty acids (FFA) from acidified oil with methanol was carried out using a calcium oxide supported on activated carbon (CaO/AC) as a heterogeneous solid-base catalyst. CaO/AC was prepared according to the conventional incipient-wetness impregnation of aqueous solutions of calcium nitrate (Ca(NO3)2·4H2O) precursors on an activated carbon support from palm shell in a fixed bed reactor with an external diameter of 60 mm and a height of 345 mm. Methanol/oil molar ratio, feed flow rate, catalyst bed height and reaction temperature were evaluated to obtain optimum reaction conditions. The results showed that the FFA conversion increased with increases in alcohol/oil molar ratio, catalyst bed height and temperature, whereas decreased with flow rate and initial water content in feedstock increase. The yield of FAME achieved 94% at the reaction temperature 60 °C, methanol/oil molar ratio of 25: 1 and residence time of 8 h. The physical and chemical properties of the produced methyl ester were determined and compared with the standard specifications. The characteristics of the product under the optimum condition were within the ASTM standard. High quality waste cooking palm oil methyl ester was produced by combination of heterogeneous alkali transesterification and separation processes in a fixed bed reactor. In sum, activated carbon shows potential for transesterification of FFA.

Calcium Oxide Derived from Waste Shells of Mussel, Cockle, and Scallop as the Heterogeneous Catalyst for Biodiesel Production

The waste shell was utilized as a bioresource of calcium oxide (CaO) in catalyzing a transesterification to produce biodiesel (methyl ester). The economic and environmen-friendly catalysts were prepared by a calcination method at 700–1,000°C for 4 h. The heterogeneous catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and the Brunauer-Emmett-Teller (BET) method. The effects of reaction variables such as reaction time, reaction temperature, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated. Reusability of waste shell catalyst was also examined. The results indicated that the CaO catalysts derived from waste shell showed good reusability and had high potential to be used as biodiesel production catalysts in transesterification of palm oil with methanol.

Oyster and Pyramidella Shells as Heterogeneous Catalysts for the Microwave-Assisted Biodiesel Production from Jatropha curcas Oil

Microwave-assisted biodiesel production via transesterification of Jatropha curcas oil with methanol using solid oxide catalyst derived from waste shells of oyster and Pyramidella was studied. The shells were calcined at 900°C for 2 h and calcium oxide (CaO) catalyst characterizations were carried out by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), and the Brunauer-Emmett-Teller (BET) surface area measurements. The effects of reaction variables such as reaction time, microwave power, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated. Reusability of waste shell catalyst was also examined. The results indicated that the economic and environmentally friendly catalysts derived from oyster and Pyramidella shells showed good reusability and had high potential to be used as biodiesel production catalysts under microwave-assisted transesterification of Jatropha curcas oil with methanol.

Rapid transesterification of Jatropha curcas oil to biodiesel using novel catalyst with a microwave heating system

We used a microwave heating system to increase Jatropha biodiesel yield, and to reduce both reaction time and energy consumption. The feasibility of converting natural and non-edible feedstocks including arcuate mussel shells and dolomitic rocks, into a novel high-performance, reusable, low-cost and heterogeneous catalyst for the synthesis of biodiesel was also explored. Arcuate mussel shells and dolomitic rocks were first ground and calcined at 900 °C for 2 h. After calcination, calcium oxide (CaO) or a mixed oxide of calcium and magnesium (CaO·MgO) was obtained as white powder, which was then chemically activated to improve the physical, chemical and surface properties, and catalytic activities of the catalysts. By heating CaO from waste shells in an excess dehydrated methanol under 65 °C at 8 h with nitrogen (N2) flow, calcium methoxide (Ca(OCH3)2) catalyst was prepared. The CaO from natural rocks was, however, turned into calcium glyceroxide complex, by combining with methanol and glycerol of the by-product. It was determined that calcium glyceroxide (Ca[O(OH)2C3H5]2) was formed during the transesterification and acted as the most active phase. Catalyst characterization was by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) surface area and basic strength measurements. The reaction parameters, including reaction time, microwave power, methanol/oil molar ratio, catalyst dosage and catalyst reusability, were studied for fatty acid methyl esters (FAME) yield. The results indicated that Ca(OCH3)2 and Ca[O(OH)2C3H5]2 catalysts derived from waste shells and natural rocks showed good reusability, high energy efficient, environmental-friendly, low cost and facile route for the synthesis of biodiesel.

Natural Hydroxyapatite (NHAp) Derived from Pork Bone as a Renewable Catalyst for Biodiesel Production via Microwave Irradiation

The use of waste materials for producing biodiesel via transesterification has been of recent interest. In this study, the pork bone was used as the raw materials for natural hydroxyapatite (NHAp) catalyst. The calcination of animal bone was conducted at 900 °C for 2 h. The raw material and the resulting heterogeneous catalyst were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effects of reaction time, microwave power, methanol/oil molar ratio, catalyst loading and reusability of catalyst were systematically investigated. The optimum conditions, which yielded a conversion of oil of nearly 94%, were reaction time 5 min and microwave power 800 W. The results indicated that the NHAp catalysts derived from pork bone showed good reusability and had high potential to be used as biodiesel production catalysts under microwave-assisted transesterification of Jatropha Curcas oil with methanol.

The Photocatalytic Reduction of Hexavalent Chromium by Controllable Mesoporous Anatase TiO2 Nanoparticles

Titania (TiO2) nanoparticles with periodical mesopore size (up to 150 A) have successfully been synthesized by sol-gel template method, using titanium(IV) tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different quantities of activated carbon (0%, 5%, and 10% by weight) were used as templates to control the porosity and particle size of titania nanoparticles. The templates were completely removed during the calcination in air at 500°C for 3 hr. The results showed that the specific surface area of titania is increased with increasing activated carbon content. The optical bandgap of synthesized titania exhibits a blue shift by 0.3–0.6 eV when compared to the reported value for the bulk anatase and rutile phases. The photocatalytic activity of porous titania is determined with its reduction efficiency of hexavalent chromium (Cr6

Utilization of Waste Enamel Venus Shell as Friendly Environmental Catalyst for Synthesis of Biodiesel

Calcium oxide (CaO) is one of the most promising heterogeneous alkali catalysts since it is cheap, abundantly available in nature, and some of the sources of this compound are renewable (waste material consisting of calcium carbonate (CaCO3)). In this study, the waste enamel venus shell was used as the raw material for CaO catalyst. The calcination of bio-waste was conducted at 900 °C for 2 h. The raw material and the resulting CaO catalyst were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effects of reaction variables such as reaction time, microwave power, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated by gas chromatograph-mass spectrometry (GC-MS). From the experimental results, it was found that the CaO catalysts derived from waste material showed good catalytic activity (the conversion of oil of nearly 93%, a very similar catalytic activity with laboratory CaO) and had high potential to be used as biodiesel production catalysts in transesterification of Jatropha Curcas oil with methanol.

Effects of Carbonization Temperature and Nanoporous Silica Templating on the Synthesis of Porous Carbon from Commercial Sugar

Porous carbons were synthesized from commercial sugar via microporous silica template method in order to control the micropore structure of carbon. The silica template used in this study had a uniform particle size, a specific surface area of 991 m2/g and an average pore size of 2 nm. The effects of carbonization temperature and the content of silica template were investigated. The results showed that the carbonization temperature of 800→C and 50%SiO2/C yielded the maximum methylene blue and iodine adsorption capacity. However, due to microporous nature, a partial dissolution of the silica template with HF solution occurred and blocked the pore entrance, reducing the adsorption capacity and specific surface area of carbon. The specific surface area as high as 1,134 m2/g was, therefore, achieved with porous carbons synthesized without nanoporous silica template.

The Fabrication of Multicolor Electrochromic Device Based on RGO/BOPP Using Ag Nanoparticles

In this research, we focused on silver (Ag) nanoparticles that exhibit various colors on the basis of their localized surface plasmon resonance (LSPR). The effects of step-voltage parameters on the coloration of the Ag deposition-based electrochromic device were investigated. Further, we report the use of reduced graphene oxide (RGO)/biaxially oriented polypropylene (BOPP) as the transparent conductive electrode. RGO was synthesized directly from graphite under a microwave heating system. BOPP film was coated with RGO by drop-casting method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), electrical resistance measurements and cyclic voltammetry (CV). The SEM and TEM images exist as typical wrinkled structure, folded region, transparent, indicating these layers are exfoliated to a very large extent. Our results primarily indicate that the novel BOPP/RGO/Ag/RGO/BOPP configuration presents an easy and expeditious way of preparing the voltage-tunable multicolor electrochromic device. The electrochromic device can be switched from the transparent state to the black state and yellow state.