Anusorn Seubsai

Bio: Anusorn Seubsai is an academic researcher from Kasetsart University. The author has contributed to research in topics: Catalysis & Propylene oxide. The author has an hindex of 15, co-authored 58 publications receiving 790 citations. Previous affiliations of Anusorn Seubsai include Sumitomo Chemical & University of California, Los Angeles.

High-Performance Asymmetric Supercapacitors of MnCo2O4 Nanofibers and N-Doped Reduced Graphene Oxide Aerogel.

Abstract: The working potential of symmetric supercapacitors is not so wide because one type of material used for the supercapacitor electrodes prefers either positive or negative charge to both charges. To address this problem, a novel asymmetrical supercapacitor (ASC) of battery-type MnCo2O4 nanofibers (NFs)//N-doped reduced graphene oxide aerogel (N-rGOAE) was fabricated in this work. The MnCo2O4 NFs at the positive electrode store the negative charges, i.e., solvated OH–, while the N-rGOAE at the negative electrode stores the positive charges, i.e., solvated K+. An as-fabricated aqueous-based MnCo2O4//N-rGOAE ASC device can provide a wide operating potential of 1.8 V and high energy density and power density at 54 W h kg–1 and 9851 W kg–1, respectively, with 85.2% capacity retention over 3000 cycles. To understand the charge storage reaction mechanism of the MnCo2O4, the synchrotron-based X-ray absorption spectroscopy (XAS) technique was also used to determine the oxidation states of Co and Mn at the MnCo2O4 el...

Charge storage mechanisms of manganese oxide nanosheets and N-doped reduced graphene oxide aerogel for high-performance asymmetric supercapacitors.

Abstract: Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGOae) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO2 during the charging process is 7.4 μg cm-2. Whilst, the mass change of the solvated ions at the N-rGOae electrode is 8.4 μg cm-2. An asymmetric supercapacitor of MnO2//N-rGOae (CR2016) provides a maximum specific capacitance of ca. 467 F g-1 at 1 A g-1, a maximum specific power of 39 kW kg-1 and a specific energy of 40 Wh kg-1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO2//N-rGOae supercapacitor may be practically used in high power and energy applications.

Oxidative Coupling of Methane by Nanofiber Catalysts

Abstract: The direct utilization of methane, the main component in natural gas (NG), as an alternate chemical feedstock to petroleum is a highly desirable but difficult goal in industrial catalysis. Many direct and indirect methods have been proposed and studied to convert CH4 into more-useful products, including olefins (e.g. C2H4, C3H6) and higher-molecular-weight hydrocarbons and liquids (e.g. benzene and gasoline), as discussed in a recent review. The production of ethylene (C2H4) from NG represents a particularly desirable process because of its massive worldwide use as an intermediate in the production of plastics, such as polyethylene and polyvinylchloride (PVC). In addition, ethylene can be oligomerized into liquid hydrocarbons, thereby enabling the efficient utilization of natural gas in remote parts of the world. The global production rate of ethylene is over 100 million tons per year, which represents an annual business in excess of $110 billion (July 2012). All indirect NG-conversion routes utilize a high temperature, endothermic, and costly steam-reforming process as the first step, from which synthetic gas (H2/CO mixtures) is produced. This step is followed by the synthesis of useful products through various catalytic processes. Although direct methods avoid the use of costly syngas, they remain uneconomical, owing, in part, to low yields of C2+ compounds, high temperatures, and low throughputs. High temperatures are particularly detrimental because they result in catalyst deactivation and create problems for reactors. In the oxidative coupling of methane (OCM), CH4 is directly converted into C2H6, C2H4, and water in the presence of O2 and a suitable catalyst. The first step involves the abstraction of H from CH4 by the catalyst to form methyl radicals (CH3C). [2, 3] The coupling of two CH3C radicals creates C2H6, followed by its dehydrogenation to afford C2H4. Some C3 hydrocarbons are also formed by the addition of a CH3C radical to C2H4. [4] However, undesirable surface reactions and gas-phase combustion reactions also lead to CO and CO2 (COx). Because high temperatures promote homogeneous gas-phase free-radical reactions, which are detrimental for C2+ products, the development of new catalysts that can operate at low temperatures is crucial for the economic viability of the OCM. Since the pioneering works of Keller and Bhasin, Hinsen and Baerns, and Ito and Lunsford, the OCM has received immense global attention, as evidenced by the large number of catalysts that have been investigated for this transformation: The oxides of almost all of the metals on the periodic table, either individually or in various combinations, have been considered and analyzed as OCM catalysts. Even the best catalysts have been reported to require feed-gas temperatures (Tf) of 700–850 8C and reaction times of 0.2–5.5 s, with C2+ yields of less than 25 %. Gas temperatures within the catalytic zones were found to be 100–200 8C higher than this range, owing to the exothermicity of this process. The actual catalyst-surface temperature is likely to be even higher still because of heattransfer considerations. An important common feature of all of these OCM catalysts is that they are based on quasi-spherical nanoparticles (powders) 2] and, thus, are prone to metal dispersion, agglomeration, and sintering. All of these problems retard catalytic activity. Herein, we report a new fabric catalyst that is comprised of La2O3 CeO2 nanofibers; this catalyst is capable of negating these problems and promoting the ignition of the OCM at a Tf value of 470 8C. The nanofibers were prepared by electrospinning. An analogous La2O3 CeO2 powder catalyst was also prepared by co-precipitation for comparison. Powders of this binary system have previously been studied by Dedov et al. and have been reported to show OCM activity at significantly higher Tf values (715–830 8C). Shown in Figure 1 (left) is the calcined La2O3 CeO2 nanofiber fabric (La/Ce, 15:1 w/w) that was used in the OCM experiments. A SEM image of this fabric (Figure 1, right) shows the formation of highly uniform La2O3 CeO2 nanofibers with diameters in the range 50–75 nm. This fabric had a low BET area of about 26 m g , which suggested that the nanofibers were dense and did not possess any internal porosity. The SEM image also shows the presence of large voids between the fibers, which enhances fabric diffusivity and decreases sintering. The XRD data for La2O3 CeO2 nanofibers and powders, both before and after the test conditions, are presented in Figure 2 (A, B and C, D), along with those for individual La2O3 (E) and CeO2 (F) fibers and powders. From these data, several interesting features are revealed: First, both the La2O3 fibers (Fig-

Removal of Heavy Metal Ions Using Modified Celluloses Prepared from Pineapple Leaf Fiber

Abstract: Since large amounts of pineapple leaves are abandoned after harvest in agricultural areas, the possibility of developing value-added products from them is of interest. In this work, cellulose fiber was extracted from pineapple leaves and modified with ethylenediaminetetraacetic acid (EDTA) and carboxymethyl (CM) groups to produce Cell-EDTA and Cell-CM, respectively, which were then used as heavy metal ion adsorbents. A solution of either lead ion (Pb2+) or cadmium ion (Cd2+) was used as wastewater for the purpose of studying adsorption efficiencies. The adsorption efficiencies of Cell-EDTA and Cell-CM were significantly higher than those of the unmodified cellulose in the pH range 1-7. Maximum adsorptions toward Pb2+ and Cd2+ were, for Cell-EDTA, 41.2 and 33.2 mg g-1, respectively, and, for Cell-CM, 63.4 and 23.0 mg g-1, respectively. The adsorption behaviors of Cell-CM for Pb2+ and Cd2+ fitted well with a pseudo-first-order model, but those of Cell-EDTA for Pb2+ and Cd2+ fitted well with a pseudo-second-order model. All of the adsorption behaviors could be described using the Langmuir adsorption isotherm. Desorption studies of Pb2+ and Cd2+ on both adsorbents using 1 M HCl suggested that regenerability of Cell-EDTA was, for both adsorbates, better than that of Cell-CM. Moreover, adsorption measurements in a mixture of Pb2+ and Cd2+ at various ratios showed that for both adsorbents the adsorption of Pb2+ was higher than that of Cd2+, while the adsorption selectivity for Pb2+ of Cell-CM was greater than that of Cell-EDTA. This study showed that the modified cellulosic adsorbents made from pineapple leaves were able to efficiently adsorb metal ions.

Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes.

Abstract: The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry

Abstract: Oxidation catalysis not only plays a crucial role in the current chemical industry for the production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to the establishment of novel green and sustainable chemical processes. This review is devoted to dealing with selective oxidation reactions, which are important from the viewpoint of green and sustainable chemistry and still remain challenging. Actually, some well-known highly challenging chemical reactions involve selective oxidation reactions, such as the selective oxidation of methane by oxygen. On the other hand some important oxidation reactions, such as the aerobic oxidation of alcohols in the liquid phase and the preferential oxidation of carbon monoxide in hydrogen, have attracted much attention in recent years because of their high significance in green or energy chemistry. This article summarizes recent advances in the development of new catalytic materials or novel catalytic systems for these challenging oxidation reactions. A deep scientific understanding of the mechanisms, active species and active structures for these systems are also discussed. Furthermore, connections among these distinct catalytic oxidation systems are highlighted, to gain insight for the breakthrough in rational design of efficient catalytic systems for challenging oxidation reactions.

Methane activation: the past and future

Abstract: The conversion of methane to more valuable chemicals is one of the most intensively studied topics in catalysis. The direct conversion of methane is attractive because the process is simple, but unfortunately its products are chemicals that are more reactive than methane. The current status of this research field is discussed with an emphasis on C–H bond activation and future challenges.

Combinatorial and High-Throughput Screening of Materials Libraries: Review of State of the Art

Abstract: Rational materials design based on prior knowledge is attractive because it promises to avoid time-consuming synthesis and testing of numerous materials candidates. However with the increase of complexity of materials, the scientific ability for the rational materials design becomes progressively limited. As a result of this complexity, combinatorial and high-throughput (CHT) experimentation in materials science has been recognized as a new scientific approach to generate new knowledge. This review demonstrates the broad applicability of CHT experimentation technologies in discovery and optimization of new materials. We discuss general principles of CHT materials screening, followed by the detailed discussion of high-throughput materials characterization approaches, advances in data analysis/mining, and new materials developments facilitated by CHT experimentation. We critically analyze results of materials development in the areas most impacted by the CHT approaches, such as catalysis, electronic and fun...

Core–shell structured catalysts for thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2

Abstract: Catalytic conversion of CO2 to produce fuels and chemicals is attractive in prospect because it provides an alternative to fossil feedstocks and the benefit of converting and cycling the greenhouse gas CO2 on a large scale. In today's technology, CO2 is converted into hydrocarbon fuels in Fischer-Tropsch synthesis via the water gas shift reaction, but processes for direct conversion of CO2 to fuels and chemicals such as methane, methanol, and C2+ hydrocarbons or syngas are still far from large-scale applications because of processing challenges that may be best addressed by the discovery of improved catalysts-those with enhanced activity, selectivity, and stability. Core-shell structured catalysts are a relatively new class of nanomaterials that allow a controlled integration of the functions of complementary materials with optimised compositions and morphologies. For CO2 conversion, core-shell catalysts can provide distinctive advantages by addressing challenges such as catalyst sintering and activity loss in CO2 reforming processes, insufficient product selectivity in thermocatalytic CO2 hydrogenation, and low efficiency and selectivity in photocatalytic and electrocatalytic CO2 hydrogenation. In the preceding decade, substantial progress has been made in the synthesis, characterization, and evaluation of core-shell catalysts for such potential applications. Nonetheless, challenges remain in the discovery of inexpensive, robust, regenerable catalysts in this class. This review provides an in-depth assessment of these materials for the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2 into synthesis gas and valuable hydrocarbons.