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Tin(IV) oxide (SnO2) is the catalyst most commonly used for electrochemical reduction of CO2 into formate. However, the electrocatalytic performance of SnO2 is not ensured due to its poor long-term stability. Here, we report our study on the electrochemical stability of SnO2 for 152 h and describe an approach to achieve stable SnO2 electrodes using a γ-alumina (γ-Al2O3) support. The γ-Al2O3 reduces the leaching of Sn from the supported-SnO2 during CO2 electrolysis due to the strong interaction of the support with the electrocatalyst. This maintains the particle size, morphology, and crystallinity of SnO2. Thereby, pulverization of SnO2 is prevented and stable selectivity towards CO2 reduction results. The prepared SnO2/γ-Al2O3 exhibits much more stable Faradaic efficiency (65.0% at 152 h) and partial current density (21.7 mA cm−2 at 152 h) for formate synthesis than does unsupported SnO2 electrocatalyst (14.2% Faradaic efficiency; 4.6 mA cm−2 of partial current density at 152 h).

We report the synthesis of tripodal ligand-based nickel catalysts [Ni(tren)(NO3)2] (1) & [Ni(hmtren)(H2O)](NO3)2 (2) and demonstrate its catalytic hydrogenation of CO2 to formate in a basic medium. 1 exhibited the catalytic activity with a turnover number (TON) of 418 in a triethylamine medium at 120 °C. 2 was synthesized by introducing electron releasing methyl groups in 1, which was found to enhance the production of formate and presented a better TON of 638. The catalytic effects of 1 and 2 in the production of formate with NaHCO3 and KOH bases are discussed, and this study validates the use of a non-precious metal catalyst for CO2 hydrogenation in an aqueous medium.

Supercritical methylcyclohexane cracking of NiAl2O4 spinel-based catalysts with varying Ni/Al deficiencies was investigated. Thus, catalysts with Ni content of 10–50 wt.% were prepared by typical co-precipitation methods. The calcined, reduced, and spent catalysts were characterized by X-ray diffraction, O2 temperature-programmed oxidation, NH3 temperature-programmed desorption, N2 physisorption, O2 chemisorption, scanning and transmission electron microscopy, and X-ray fluorescence. The performance and physicochemical properties of the reference stoichiometric Ni3Al7 catalyst differed significantly from those of the other catalysts. Indeed, the Ni-deficient Ni1Al9 catalyst led to the formation of large Ni particles (diameter: 20 nm) and abundant strong acid sites, without spinel structure formation, owing to the excess Al. These acted with sufficient environment and structure to form the coke precursor nickel carbide, resulting in a pressure drop within 17 min. On the other hand, the additional NiO linked to the NiAl2O4 spinel structure of the Al-deficient Ni5Al5 catalyst formed small crystals (10 nm), owing to the excess Ni, and displayed improved Ni dispersion. Thus, dehydrogenation proceeded effectively, thereby improving the resistance to coke formation. This catalytic behavior further demonstrated the remarkable activity and stability of this catalyst under mild conditions (450 °C and 4 Mpa).

The tire industry has shown an increasing demand for the reduction in rolling resistance. Efforts have been made to improve the viscoelastic properties of tire compounds and reduce the weight of tires through optimization of the vulcanizate structure, which has become extremely complex. In this study, vulcanizates using carbon black and silica as binary fillers were prepared at various curing temperatures. Vulcanizate structures with respect to curing temperature were classified according to the chemical crosslink density by sulfur, carbon black bound rubber (i.e., physical crosslink due to carbon black), and silica-silane–rubber network. All properties exhibited a decreasing trend under the application of high curing temperatures, and the decrease in the crosslink density per unit content of filler with an increase in curing temperature was shown to be greater in carbon black than in silica. Mechanical and viscoelastic properties were also measured to evaluate the impact that the compound variates have on tire tread performance. These results serve as a guideline for determining the content and filler type and for setting the cure condition during the design of actual compound formulations to increase the crosslink density of rubber while retaining the necessary mechanical and viscoelastic properties for practical application.

Hypersonic aircrafts suffer from heat management problems caused by the air friction produced at high speeds. The supercritical catalytic cracking of fuel is endothermic and can be exploited to remove heat from the aircraft surfaces using specially designed heat management systems. Here, we report that an acid/base-treated activated carbon (AC) catalyst shows superior performance to the conventional ZSM-5 catalyst at 4 MPa and 450 &deg, C. Further, under these conditions, coke formation is thermodynamically avoided. Of the prepared catalysts, the AC catalyst treated with NaOH and subsequently with HNO3 (denoted AC-3Na-N) was the most active catalyst, showing the highest selectivity toward light olefins and best heat sink capacity. The acid/base-treated ACs and ZSM-5 catalysts were characterized by scanning transmission electron microscopy, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption, and Fourier-transform infrared spectroscopy measurements. Characterization reveals the importance of acid strength and density in promoting the cracking reaction pathway to light olefins observed over the acid/base-treated AC catalysts, which show comparable activity at 450 &deg, C to that of the ZSM-5 catalyst operated above 550 &deg, C. The low-temperature activity suppressed coke and aromatic compound (coke precursors) formation. The stability of the acid/base-treated activated carbon catalysts was confirmed over a time-on-stream of 30 min.

Isostructural [M2(DOBDC)(EG)2] (M = Mg, Co, Ni) frameworks are first synthesized by controlling the pH* in the reaction medium. Coordinated ethylene glycols form a hexagonal OH cluster, which works...

Silica compounds were prepared using non-functionalized solution styrene-butadiene rubber (SSBR) to investigate effect of the functional group of silanes on the silica modification and properties o...

To avoid the main disadvantage of the carbon dioxide (CO2) capture process, namely the large amount of energy consumed to regenerate the amine absorbent using current thermal methods, chemical regeneration has been introduced as a novel method to regenerate the amine. Chemical regeneration deploys a swing in the pH of the amine absorbent rather than the swing in temperature of typical thermal regeneration procedures, and hence reduces the regeneration energy. Here we tested calcium chloride (CaCl2) and calcium hydroxide (Ca(OH)2) as a calcium source for CO2 desorption and a pH swing agent for amine regeneration. After desorbing from the amine, CO2 in our procedures reacted with Ca2+ to form calcium carbonate (CaCO3). Forming precipitated CaCO3 is a permanent way to sequester CO2. Since carbonates have a low energy level compared to CO2, we expect the developed method to be an economical and energy-efficient process.

This study investigates the decomposition of methane using solar thermal energy as a heat source. Instead of the direct thermal decomposition of the methane at a temperature of 1200 °C or higher, a catalyst coated with carbon black on a metal foam was used to lower the temperature and activation energy required for the reaction, and to increase the yield. To supply solar heat during the reaction, a reactor suitable for a solar concentrating system was developed. In this process, a direct heating type reactor with quartz was initially applied, and a number of problems were identified. An indirect heating type reactor with an insulated cavity and a rotating part was subsequently developed, followed by a thermal barrier coating application. Methane decomposition experiments were conducted in a 40 kW solar furnace at the Korea Institute of Energy Research. Conversion rates of 96.7% and 82.6% were achieved when the methane flow rate was 20 L/min and 40 L/min, respectively.

The crystal structures of mono- and dinuclear CuII trifluoromethanesulfonate (triflate) complexes with benzyldipicolylamine (BDPA) are described. From equimolar amounts of Cu(triflate)2 and BDPA, a water-bound CuII mononuclear complex, aqua(benzyldipicolylamine-κ3 N,N′,N′′)bis(trifluoromethanesulfonato-κO)copper(II) tetrahydrofuran monosolvate, [Cu(CF3SO3)2(C19H19N3)(H2O)]·C4H8O, (I), and a triflate-bridged CuII dinuclear complex, bis(μ-trifluoromethanesulfonato-κ2 O:O′)bis[(benzyldipicolylamine-κ3 N,N′,N′′)(trifluoromethanesulfonato-κO)copper(II)], [Cu2(CF3SO3)4(C19H19N3)2], were synthesized. The presence of residual moisture in the reaction medium afforded water-bound complex (I), whereas dinuclear complex (II) was synthesized from an anhydrous reaction medium. Single-crystal X-ray structure analysis reveals that the CuII centres adopt slightly distorted octahedral geometries in both complexes. The metal-bound water molecule in (I) is involved in intermolecular O—H...O hydrogen bonds with triflate ligands and tetrahydrofuran solvent molecules. In (II), weak intermolecular C—H...F(triflate) and C—H...O(triflate) hydrogen bonds stabilize the crystal lattice. Complexes (I) and (II) were also characterized fully using FT–IR and UV–Vis spectroscopy, cyclic voltammetry and elemental analysis.

Catalytic conversion of CO2 to methanol is gaining attention as a promising route to using carbon dioxide as a new carbon feedstock. AlOOH supported copper-based methanol synthesis catalyst was investigated for direct hydrogenation of CO2 to methanol. The bare AlOOH catalyst support was found to have increased adsorption capacity of CO2 compared to conventional Al2O3 support by CO2 temperature-programmed desorption (TPD) and FT-IR analysis. The catalytic activity measurement was carried out in a fixed bed reactor at 523 K, 30 atm and GHSV 6,000 hr−1 with the feed gas of CO2/H2 ratio of 1/3. The surface basicity of the AlOOH supported Cu-based catalysts increased linearly according to the amount of AlOOH. The optimum catalyst composition was found to be Cu : Zn : Al=40 : 30 : 30 at%. A decrease of methanol productivity was observed by further increasing the amount of AlOOH due to the limitation of hydrogenation rate on Cu sites. The AlOOH supported catalyst with optimum catalyst compositions was slightly more active than the conventional Al2O3 supported Cu-based catalyst.

We report the synthesis of cocrystals of a substituted benzoxazole and catechol from a primary amine and 3,5-di-tert-butylbenzoquinone. Fourier transform infrared and NMR spectroscopy studies revealed that cocrystals 2 could be synthesized in excellent yield from 1 and 3,5-di-tert-butylbenzoquinone. Introduction of an amine into the cocrystal structure enhanced the CO2 adsorption capacity of the cocrystals at room temperature from 15.69 to 44.21 mg/g. Our results indicated the ability to use cocrystals for CO2 capture and to easily modify them to enhance their CO2 adsorption capacity.

We report the effects of a series of carbonic anhydrase (CA) model complexes on CO 2 absorption and desorption in an aqueous tertiary amine medium. The CO 2 hydration efficiency was determined under basic conditions by using stopped-flow kinetics experiments. Catalyst 6 was found to exhibit the best CO 2 hydration efficiency (3.130 × 10 3 M −1 s −1 ) in the tertiary amine medium. In a highly concentrated tertiary amine medium, catalyst 2 was found to enhance the absorption and regeneration efficiency of CO 2 by 10% and 24%, respectively. Our results for simple CA model complexes indicate that possible usage of synthesized complexes in post-combustion process.

The regeneration of the CO2 capture system is the most energy-intensive process associated with CO2 capture because high temperatures are required to desorb CO2 from the absorbent. We propose a single process for effective CO2 capture and mineralization as a substitute for desorption of absorbed CO2, producing high value-added CaCO3. A saturated 2-amino-2-methyl-1-propanol (AMP) solution was used as a carbonate source, and calcium chloride (CaCl2) was used as a calcium ion source to precipitate CaCO3. A semi-batch reactor was used to investigate the effects of the mixing rate, temperature, and amount of calcium added during the CaCO3 precipitation process. During the mineralization reaction, the absorbed CO2 in AMP solution instantly converted into white CaCO3 precipitant with 97.4% conversion. The stirring rate provided a reciprocal effect on the crystal size, whereas the temperature and Ca/CO2 molar ratio appeared to affect the crystal morphology.

Amine-based postcombustion CO2 capture technology has a great potential to control CO2 emissions but is expensive because a huge amount of thermal energy is required for solvent regeneration due to...

To replace the thermal regeneration method of absorbent in the CO2 capture system, a novel method of CO2 absorption–mineralization was investigated. In this study, various alkanolamine absorbents, such as monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP), were applied to the CO2 absorption–regeneration process with different regeneration methods via thermal treatment and mineralization. Calcium chloride was added as a calcium source in the mineralization process. Integration of absorption and mineralization defined as a single process was proposed in this study to resolve the excessive requirement of energy in a conventional amine regeneration process, leading to enhanced working capacity and desorption rate without increasing the regeneration temperature. This method provides an increment of working capacity 1.3–3 times higher than the conventional thermal amine-scrubbing process. Among the tested amines, MEA exhibited the highest increase ...

In this work, primary (MEA), secondary (DEA) and tertiary (MDEA) alkanolamine absorbents with a synthesized zinc–metal complex functioning as a carbonic anhydrase (CA) mimetic catalyst were applied to the absorption–desorption of carbon dioxide. Regeneration of carbon dioxide was evaluated by using a semi-batch system and the formation and extinction of bicarbonate and carbamate species were analyzed by FTIR and 13 C NMR spectroscopy. The zinc–metal complex can cause the rapid conversion from bicarbonate to carbon dioxide, confirming that the regeneration rate could be increased substantially.

The direct conversion of n-dodecane to light alkenes with an efficient catalyst can enhance the combustion efficiency and cooling performance of endothermic heat sinks for the development of propellants suitable for supersonic vehicles. In this work, a pretreated activated charcoal showed excellent performance as a novel cracking catalyst superior to the conventional ZSM-5 zeolite catalyst. Activated charcoal was oxidized at 298, 473, and 673 K, leading to surface modification, and n-dodecane cracking experiments were carried out at 4 MPa and 723 K. The activated charcoal exhibited a higher light alkene selectivity and heat sink capacity compared with the conventional ZSM-5. The charcoal oxidized at 673 K showed the highest light alkene selectivity of 28% among the tested catalysts, exceeding that of the reference ZSM-5 by 18%. The oxidizing pretreatment of the charcoal at high temperatures was found to generate carboxylic functional groups acting as Brӧnsted acid sites based on characterization by X-ray photoelectron spectroscopy, FT-IR, and temperature-programmed desorption with NH3. The activated charcoal oxidized at 673 K had the largest amount of strong acid sites and Brӧnsted acid sites, which led to the highest conversion of n-dodecane and the selectivity of light alkene.

Electrochemical reduction of carbon dioxide (CO2) to formate (HCOO–) in aqueous solution is studied using tin–lead (Sn–Pb) alloys as new electrocatalysts. In electrochemical impedance spectroscopy (EIS) measurements, lower charge-transfer resistance is observed for the alloy electrodes when compared to the single metal electrodes such as Sn and Pb. The results of X-ray photoelectron spectroscopy (XPS) and cyclic voltammetric (CV) analysis show that the Sn in the Sn–Pb alloys facilitates the formation of oxidized tin (SnOx) and metallic lead (Pb0) on the alloy surface by inhibiting the formation of low-conductive lead oxide (PbO) film. The CV analysis confirms that the Sn–Pb alloys exhibit higher reduction current than the single metal electrodes under CO2 atmosphere. The Faradaic efficiency (FE) and the partial current density (PCD) of HCOO– production on the alloy electrodes is investigated by electroreduction experiments at −2.0 V (vs Ag/AgCl) in an H-type cell. As results, respectively more than 16% an...

The rise in atmospheric CO2 levels due to the effects of human activities poses a serious threat to the world's ecosystems because of global warming and climate change. Efficient methods are needed to limit the elevation of CO2 levels in the atmosphere. Here, we propose an improved CO2 sequestration method that uses new catalysts, specifically a series of tertiary amine nitrate salts, in an aqueous tertiary amine medium. We synthesized the new catalysts and characterized them by using 1H and 13C NMR, single crystal X-ray analysis, and FT-IR spectroscopy. The effects of the catalysts on CO2 absorption were assessed by using a stopped-flow spectrophotometer, and their heats of absorption and CO2 absorption capacities were measured with a differential reaction calorimeter (DRC) at high concentrations of the tertiary amine medium. The CO2 hydration rate constants were determined under basic conditions and the catalysts were found to exhibit higher absorption of CO2 (a highest value of 430 M−1 s−1) than the tertiary amine medium (133 M−1 s−1). The increased absorption of CO2 and the low heat absorption energies of the new catalysts suggest that they could be used in post-combustion processes.

To prevent car accidents, it is important to evaluate the thermal stability of tire rubbers, such as natural rubber (NR), butadiene rubber (BR), and styrene–butadiene rubber (SBR). Controlling the glass transition temperature (Tg) is the main factor for obtaining desirable thermal stability. Here, we developed an optimized equation for the prediction of the Tg of the various rubber systems using molecular dynamics (MD) simulations. We modeled a random copolymer system, blended monomers, and calculated the Tg of butadiene isomers in each composition. From these results, we designed the Tg contour of ternary cis–trans–vinyl butadiene and derived an equation of Tg for the ternary system. Moreover, we developed an equation to evaluate the pseudo-ternary Tg of quaternary SBR and plotted it. Our results present a novel way of predicting the Tg of ternary BR and quaternary SBR, which is critical for rational tire design with optimized thermal and mechanical stability.

The in situ sequestration of CO2 using alkanolamine and organometallic calcium (OMC) offers an ecofriendly method for synthesizing a diverse range of calcite, vaterite, and aragonite polymorphs of CaCO3. Aqueous N-methyldiethanolamine (MDEA) has high CO2 loading capacity with low regeneration energy, but rate of CO2 absorption was found to be slow. The driving force for the binding between CO2 and MDEA could be enhanced by the presence of bovine carbonic anhydrase (bCA). The absorbed CO2 was converted to stable carbonates through the addition of an OMC. The bCA enzyme both accelerated the CO2 absorption and mineralization in the amine–CO2–OMC system and improved the catalytic efficiency to 1.07 × 104 M–1 s–1. The enthalpy of in situ mineralization, the mechanism underlying the CO2 absorption process, and the formation of an aggregated composition of CaCO3 were examined using calorimetric, NMR, and X-ray diffraction techniques, respectively. The crystal formation depended crucially on the mineralization pr...

The solubility of CO2 in three ionic liquids which contains three different number of cyanide anions, 1-ethyl-3-methylimidazolium thiocyanate ([c2mim][SCN]), 1-ethyl-3-methylimidazolium dicyanamide ([c2mim][N(CN)2]), 1-ethyl-3-methylimidazolium tricyanomethanide ([c2mim][C(CN)3]) was measured in order to investigate the effects of cyanide anions on the solubility of CO2. The solubility of CO2 was determined by measuring the bubble point pressure at the temperature ranges from 303.15 to 373.15 K in 10 K intervals. Also, the measured data were correlated with the PR-EoS (Peng-Robinson equation of state) incorporated with the conventional van der Waals one fluid mixing rule. The critical properties of ionic liquids were estimated using the modified Lydersen–Joback–Reid method. As a result, the calculated data were comparatively well commensurate with the experimental results and, as is commonly known, the solubility of CO2 was observed to increase with increasing pressure and with decreasing temperature. Moreover, the results also show that the highest solubility was obtained by [c2mim][C(CN)3] among those three experimented ionic liquids while [c2mim][SCN] has the lowest. It implies that the CO2 solubility is affected by the number of cyanide anions contained in ionic liquid. From this result, it is concluded that the cyanide anion enhances the CO2 solubility in ionic liquid and that the ionic liquid which contains more cyanide anion has higher CO2 solubility.

In this study, a combined test of the WGS (water–gas shift) reactor and a Pd-based composite membrane was carried out for pre-combustion CO 2 capture in a coal gasifier. The two series of WGS reactions, i.e., a high-temperature shift and a low-temperature shift, were performed under a gas composition of 60% CO and 40% H 2 at 2100 kPa to imitate coal gasification. The CO 2 enrichment and H 2 recovery tests at 673 K and 2100 kPa with the high-pressure membrane module after the WGS reaction presented the enriched CO 2 concentration and H 2 recovery ratios of ∼92% and ∼96%, respectively. The long-term stability test showed that the CO 2 concentration decreased to 78.2%, and CO was generated and reached to 8.8% in the retentate stream after 47 h because of reverse WGS and CO 2 hydrogenation reaction on 316L stainless steel module. The stability test for ∼3137 h showed that these catalytic activities could be successfully prevented using steel with higher Cr and Ni contents, such as 310S. The WGS-membrane combination test using the outlet gas from a real coal gasifier was continued for ∼100 h and showed that the WGS catalysts and membrane module made of 310S would be stable under real conditions.

The chemical compatibility of perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) oxides with Cr2O3 has been examined between room temperature and 1,100 °C. Differential thermal analysis and thermogravimetric analysis were used to analyze the thermal behavior of BSCF–Cr2O3 binary mixtures in all composition ranges (0–100 mass% BSCF). The reaction products were identified by X-ray analysis after heating at 700–1,100 °C. As we expected, it was found that perovskite-type BSCF oxide had a poor chemical compatibility with the Cr2O3 oxide. In particular, the decomposition process of the BSCF–Cr2O3 binary mixture is quite complex and it starts at about 700–750 °C. The mixtures of BSCF and Cr2O3 oxides reacted forming mixed complex oxides based on (Ba/Sr)FeO3, (Co/Fe)CrO4, and (Ba/Sr)CrO4 mixtures.

The Fischer–Tropsch reaction was performed using a pilot-scale slurry bubble column reactor (SBCR) and a lab-scale continuous stirred tank reactor (CSTR). In contrast to the CSTR, a transitory induction period was observed in the SBCR. In this study, we investigated the catalyst performance during the induction period focusing on the hydrodynamic parameter changes inside the reactor. We measured the hydraulic pressure for the constant slurry thickness during FTS reaction. The FT wax product was regularly withdrawn using a metal filter and analyzed for density, oxygen concentration, and compositional analysis. The liquid density was affected by the dilution of the initial liquid media by fresh FT product for the whole reaction time of 180 h. On the other hand, the oxygen concentration increased sharply for the initial 85 h and then reached the steady state. Accordingly, the gas hold-up and CO conversion were enhanced for the same period. The increase in the gas hold-up could be explained by the coalescence inhibition effect of oxygenated compounds, which were the main byproducts when iron-based catalysts were used. The dynamic gas disengagement technique was employed to identify the coalescence inhibition effect of alcohol in the hydrocarbon system using a cylindrical acrylic bubble column.

In a trayed bubble column, the structure of the partitioning plate plays an important role on the bubble behavior. This study examined the effect of the opening ratio and pore size of the plate on the bubble break-up frequency and bubble size distribution. The sieve tray was used as the partitioning plate. The opening ratio was closely related to gas cap development. The stagnation of bubble flow and a gas cap were observed with an opening ratio less than 48.5%. The gas cap increased with decreasing opening ratio and increasing superficial gas velocity. The main effect of the sieve tray could be categorized into the additional drag force and bubble break-up depending on the sieve pore size. When the sieve pore size was smaller than the Sauter diameter of the bubble swarm, the movement of rising bubbles was interrupted by the drag force applied by the surrounding mesh lines. On the other hand, when the sieve pore size was larger than the Sauter diameter, the bubbles were affected by the additional bubble break-up. After the bubbles penetrated the sieve tray, the bubble size distribution shifted to a smaller one and the Sauter diameter decreased.

Fischer–Tropsch synthesis was carried out over precipitated iron-based catalysts with different amounts of CO2 in the feed stream while maintaining both total reaction pressure (1.5 MPa) and partial pressure of H2 + CO (0.75 MPa) using an inert balance gas, N2. The CO2 in the feed stream decreased the rate of hydrocarbon formation, but it had no significant influence on the carbon number distribution of hydrocarbons. The CO2 in the feed stream also suppressed CO2 formation, decreasing both CO conversion and CO2 selectivity. We attribute the decreased reaction rate to the partial competition in the adsorption behavior between CO and CO2 as revealed in the temperature-programmed desorption.

The pre-reforming of higher hydrocarbon, propane, was performed to generate hydrogen from LPG without carbon deposition on the catalysts. A Ru/Ni/MgAl2O4 metallic monolith catalyst was employed to minimize the pressure drop over the catalyst bed. The propane pre-reforming reaction conditions for the complete conversion of propane with no carbon formation were identified to be the following: space velocities over 2400 h−1 and temperatures between 400 and 450 °C with a H2O/C1 ratio of 3. The combined pre-reformer and the main reformer system with the Ru/Ni/MgAl2O4 metallic monolith catalyst was employed to test the conversion propane to syngas where the reaction heat was provided by catalytic combustors. Propane was converted in the pre-reformer to 52.5% H2, 27.0% CH4, 17.5% CO, and 3.0% CO2 with a 331 °C inlet temperature and a 482 °C catalyst outlet temperature. The main steam reforming reactor converted the methane from the pre-reformer with a conversion of higher than 99.0% with a 366 °C inlet temperature and an 824 °C catalyst outlet temperature. With a total of 912 cc of the Ru/Ni/MgAl2O4 metallic monolith catalyst in the main reformer, the H2 production from the propane reached an average of 3.25 Nm3h−1 when the propane was fed at 0.4 Nm3h−1.

Yellow-colored exhaust gas streams from internal engines or gas turbines, frequently referred to as “yellow plume,” contain nitrogen dioxide (NO2) at concentrations as low as 15 ppm. The process developed in this work for decolorizing the yellow plume is based on reduction of NO2 to NO utilizing a combination of a Pt catalyst and a reducing agent. A stoichiometric excess of carbon monoxide, diesel oil, methanol or ethanol were used as reducing agents. Depending on the type of the reductant, the active temperature window of NO2 reduction was varied with methanol and CO being active at lower temperatures and ethanol and diesel oil at higher temperatures. By changing the Pt loading of the catalysts the active temperature window of NO2 reduction was also changed, higher loading Pt catalysts being active at lower temperatures. This scheme of NO2 reduction process was verified in a pilot-scale test with the real exhaust gas from the gas turbine power plant, showing 96% of NO2 reduction at the stack temperatures of 102–123 °C and at space velocities of 28,000–95,000 h−1 with inherent CO in the exhaust gas as the reducing agent.

The developed diesel fuel reformer presented in this study consists of three components: a fuel injection part working with an air-blown nozzle; a fuel vaporizing part; catalytic converting part. The injected diesel fuel was vaporized on the surface of the electrically heated cylindrical metallic monolith cell (EHC; electrically heated cell). With our injection and vaporization systems, fast start-ups within 4 min were accomplished at low energy consumption in the stand-alone mode; this proved practicable for transportation applications. The palladium-based catalyst was prepared by the dip coating method. All SEM, TEM, and XPS analyses showed that an intensive and uniform catalyst layer was formed on the metallic monolith surface, composed of palladium oxide crystallite impregnated on alumina support. The catalytic partial oxidation of n-hexadecane was carried out by varying the C/O ratio and steam/C ratio within the GHSV in the range of 30,000–100,000 h−1. Both TPO and XPS analyses were performed for tracing the reaction mechanism of the partial oxidation of n-hexadecane into synthesis gas under the palladium-based catalyst. Partial oxidation over the palladium catalyst was proposed to proceed via the Mars & van Krevelen two-stage redox mechanism. Addition of CeO2, BaO, and SrO promoters to the Pd/Al2O3 catalyst improved thermal stability, as well as the ability of instant re-oxidation of metallic Pd to PdO during the redox cycles, which gave rise to an increase in catalytic activity for higher synthesis gas productivity of higher H2/CO ratios and lower CO2 selectivity.

The gas hold-up variation and regime transition were investigated with different liquid viscosities ranging from 1.0 mPa s to 31.5 mPa s using a 0.15-m-in-diameter bubble column. In contrast to common observations, the gas hold-up graph with the superficial gas velocity could be categorized into three flow regimes: homogeneous, pseudo-homogeneous and heterogeneous flow regimes. The formation of large bubbles caused a transition from the homogeneous to the pseudo-homogenous flow regime, in which large bubbles rose vertically without oscillatory turbulence. According to the results from the dynamic gas disengagement (DGD) technique, large bubbles began to form at the transition superficial gas velocity to the pseudo-homogeneous flow regime. The transition to a heterogeneous flow regime was initiated by the turbulent movement of large bubbles. The transition superficial velocities to pseudo-homogeneous and heterogeneous flow regimes, u t1 and u t2 , decreased with increasing liquid viscosity below a critical viscosity and converged to a certain value above that viscosity. However, the correlations from the literatures could not make a reasonable estimation of the transition superficial velocities because they did not consider the possible transition to a pseudo-homogeneous flow regime. Therefore, the two transition points should be predicted separately.

Mass transfer limitations on fixed-bed for Fischer–Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10 − 4 m s − 1 to 3.39 × 10 − 3 m s − 1 . As a result, the synthesis gas superficial velocity of 3.39 × 10 − 3 m s − 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount ( W cat / F ) were discussed. The large catalyst pellet showed higher C 5+ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α -olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount ( W cat / F ) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g ( W cat / F = 45 g cat min L − 1 ) was most appropriate for liquid hydrocarbon formation.

Fischer–Tropsch synthesis (FTS) was carried out in a fixed bed reactor with a highly effective cobalt catalyst for wax production. The procedure for reducing the inactive cobalt oxide to the active cobalt catalyst was examined by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results showed that 300 ml/min H 2 at 350 °C for 16 h was suitable for reducing the inactive Co oxides to active metallic Co sites. In the case of the powder and pellet type cobalt catalysts with a reactant (H 2 /CO = 2:1) flow rate of 15 g cat min L −1 , catalyst deactivation occurred as a result of mass transfer limitations of the hydrocarbon and water produced on the catalyst. On the other hand, the pellet type cobalt catalyst with a reactant flow rate of 45 g cat min L −1 showed activity not only for liquid hydrocarbon (C 5+ ) formation but also for gas product (CH 4 and CO 2 ) formation. In particular, the methane yield reached almost 20% due to heat transfer limitation in the catalyst. Considering the heat and mass transfer limitations in the cobalt catalyst, a Co-foam catalyst with an inner metallic foam frame and an outer cobalt catalyst was developed. SEM–EDS Co-mapping revealed the cobalt atoms to be distributed equally over the surface of the Co-foam catalyst. The Co-foam catalyst was highly selective toward liquid hydrocarbon production and the liquid hydrocarbon productivity at 203 °C was 52.5 ml kg cat - 1 h −1 , which was higher than that by the Co-pellet. In addition, the chain length probability, α , by the Co-foam catalyst was 0.923 and wax formation was especially favored.

Fischer-Tropsch synthesis (FTS) was carried out using Al2O3-supported Co catalyst coated on metallic monolith. Considering the liberation of a large amont of heat from the highly exothermic FTS reaction, catalytic activity of Co catalyst coated on metallic monolith was tested and compared with that of pellet-type catalysts. The reaction was carried out in a conventional tubular fixed-bed reactor and simulated distillation (SIMDIS) analysis method was used to determine the liquid products distribution. Proper control of degree of reaction, as well as the reaction temperature gave rise to a shift of products selectivity toward higher hydrocarbons, especially C13−C18 diesel range hydrocarbons.

In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which stable and fast start-ups (within 4 min) were achieved. Gas hourly space velocity and O2/CH4 governed, methane conversion, while H2O/CH4 controlled H2/CO ratio. A methane conversion of approx. 96%, H2+CO selectivity of approx. 85%, and H2/CO of approx. 2.6 were obtained under the conditions of gas hourly space velocity (GHSV) at 103000 h−1, O2/CH4=0.7 and H2O/CH4=0.35.

Esterification of acrylic acid (AA) with 1,4-butanediol (BD) was carried out over a solid acid catalyst to produce 4-hydroxybutyl acrylate (HBA), an environmentally benign coating agent. The Amberlyst 15 catalyst was more active for the reaction than other ion exchanged resin catalysts such as Amberlyst 35 and DOWEX HCR-S(E). The quasi-homogeneous model was chosen to express the esterification reaction kinetics over Amberlyst 15. The stirring speed was changed from 300 rpm to 750 rpm and the reaction rate showed no influence of external mass transfer. The reaction temperature was varied from 100°C to 120°C to calculate activation energies of the reactions. The calculated activation energies were 58.3 kJ/mol and 86.7 kJ/mol for HBA and BDA (1,4-butanediol diacrylate, by-product) productions, respectively. The catalyst concentration was also changed from 0.0043 g/ml to 0.0171 g/ml to find its effect on the rate constant. The complete kinetic equation of esterification to produce HBA over the Amberlyst 15 catalyst based on the quasi-homogeneous model was developed.

Four different modifications of alumina were prepared for use as the support for a Pd catalyst used for the partial oxidation of methane to syngas. The catalysts were washcoated on a metallic monolith in order to determine their activities at high gas flow rates. Compared with the Pd/Al 2 O 3 catalyst, enhanced partial oxidation activities were observed with the Pd/CeO 2 /Al 2 O 3 , Pd/CeO 2 /BaO/Al 2 O 3 and Pd/CeO 2 /BaO/SrO/Al 2 O 3 catalysts. The palladium particles were better dispersed in the presence of CeO 2 and SrO. Adding BaO, CeO 2 and BaO–CeO 2 to γ-Al 2 O 3 prevented the transformation of the alumina phase during the 3-day aging process at 1000 °C, providing the support with some level of thermal stability. The addition of small amounts of SrO to the CeO 2 /BaO/Al 2 O 3 support enhanced the thermal stability of the Pd particles and minimized their sintering. The triply promoted Pd catalyst studied in this work was effective in carrying out partial oxidation at high temperatures, with BaO and CeO 2 promoting the thermal stability of the support, CeO 2 and SrO dispersing the Pd particles and SrO anchoring the Pd particles strongly to the support. The composition of the catalyst which gave both the highest partial oxidation activity and the best thermal stability was Pd(2)/CeO 2 (23)/BaO(11)/SrO(0.8)/Al 2 O 3 .

A commercial Ni-based catalyst is wash-coated on a monolith made of 50 μm-thick fecralloy plates. Compared with the same volume of coarsely powdered Ni catalysts, the monolith wash-coated Ni catalysts give higher methane conversion in the steam reforming reaction, especially at gas hourly space velocities (GHSV) higher than 28,000 h −1 , and with no pressure drop. A higher conversion of the monolith catalyst is obtained, even though it contains a lower amount of active catalyst (3 g versus 17 g for a powdered catalyst), which indicates that the heat-transfer capability of the wash-coated Ni catalyst is significantly enhanced by the use of a metal monolith. The efficacy of the monolith catalyst is tested using a shell-and-tube type heat-exchanger reactor with 912 cm 3 of the monolith catalyst charged on to the tube side and hot combusted gas supplied to the shell side in a counter-current direction to the reactant flow. A methane conversion greater than 94% is obtained at a GHSV of 7300 h −1 and an average temperature of 640 °C. Nickel catalysts should first be reduced to become active for steam reforming. Doping a small amount (0.12 wt.%) of noble metal (Ru or Pt) in the commercial Ni catalyst renders the wash-coated catalyst as active as a pre-reduced Ni catalyst. Thus, noble metal-doped Ni appears useful for steam reforming without any pre-reduction procedure.

Globally, the elevation of carbon dioxide (CO2 ) levels due to the anthropogenic effect poses a serious threat to the ecosystem. Hence, it is important to control and/or mitigate the level of CO2 in the atmosphere, which necessitates novel tools. Herein, it is proposed to improve CO2 sequestration by using model complexes based on the enzyme carbonic anhydrase (CA) in aqueous tertiary amine medium. The effect of substituents on the model CA model complexes on CO2 absorption and desorption was determined by using a stopped-flow spectrophotometer to follow pH changes through coupling to pH indicator and a continuous stirred-tank reactor (CSTR). The CO2 hydration rate constants were determined under basic conditions and compound 6, which contained a hydrophilic group, showed the highest absorption or hydration levels of CO2 (2.860×10(3) L mol(-1) s(-1) ). In addition, CSTR results for the absorption and desorption of CO2 suggest that simple model CA complexes could be used in post-combustion processing.

Biodiesel produced by the transesterification of vegetable oils (VOs) is a promising alternative fuel to diesel regarding the limited resources of fossil fuel and the environmental concerns. In this work, an environmentally benign process for the production of biodiesel from VOs using heterogeneous catalyst was developed. Na/NaOH/γ-Al2O3 heterogeneous base catalyst was firstly adopted for the production of biodiesel. A study for optimizing the reaction conditions such as the reaction time, the stirring speed, the use of co-solvent, the oil to methanol ratio, and the amount of catalyst, was performed. The Na/NaOH/γ-Al2O3 heterogeneous base catalyst showed almost the same activity under the optimized reaction conditions compared to conventional homogeneous NaOH catalyst. The basic strength of Na/NaOH/γ-Al2O3 catalyst was estimated and the correlation with the activity towards transesterification was proposed.

Sulfur-deficient iron sulfide, ${\mathrm{Fe}}_{1.04}$S, has been studied in comparison with FeS by M\"ossbauer spectroscopy at various temperatures ranging from 82 to 600 K. It is found that the 4 at. % sulfur vacancy makes the crystallographic \ensuremath{\alpha} transition from the (NiAs,MnP) structure to a superstructure take place abruptly within 5 K with the superstructure stable up to 410 K. The spin-rotation transition of ${\mathrm{Fe}}_{1.04}$S takes place at 455 K, which is higher by 63 K than that of FeS. The N\'eel temperature is not affected appreciably by the sulfur vacancy concentration.

Matrix metalloproteinases(MMP) are a family of proteolytic enzymes that mediate the degradation of extracellular matrix macromolecules, including interstitial and basement membrane collagens, fibronectin, laminin, and proteoglycan core protein. The major cell types(fibroblasts, keratinocytes, endothelial cells, and macrophages) in periodontal tissue are capable of responding to growth factors and cytokines, as well as to products released from the microbial flora by induction of transcription of one or more MMP genes1). These MMPs share some common properties: 1) secretion from the cell in a latent form(proenzyme) with its subsequent activation in the extracellualr space; 2) containing zinc cation at the active site; 3) inhibition by chelators of calcium(e.g., EDTA), and zinc(e.g., 1, 10 phenanthroline); 4) inhibition by tissue inhibitors of metalloproteinases(TIMP); and 5) degrading at least one component of the extracellular matrix(e.g., collagen)2). One prominent member of these MMPs, MMP-3(stromelysin-1) is capable of degrading the numerous extracellular matrix macromolecules(ECM) including fibronectin, laminin, proteoglycan core protein, collagen IV, V, IX, X, and elastin3). Increase of MMP-3 activity associated with several chronic inflammatory disease appear to be the result of specific inductive mechanisms. One of the mediators in induction of MMP-3 is interleukin-1(IL-1), cell product that has important regulatory functions mediating the body's response to microbial invasion, inflammation, and tissue injury4,5,6,7). Especially, IL-1 is thought to play a important role in the tissue destruction associated with inflammatory diseases such as rheumatoid arthritis and periodontal disease8,9). As periodontitis is specifically associated with the destruction of periodontal connective tissues, it is closely related to both IL-1 and MMPs. Gingivitis can trigger the initial cascade of periodontal destruction. The human gingival fibroblast is prominent cell type in the gingival connective tissue and products cytokines inducted by microbial infection in periodontal disease. In the periodontal disease, the upregulation of MMP expression in response to locally released IL-1 may provide one component of this pathologic process. IL-1 has been identified in both the gingiva and gingival crevicular fluids of periodontitis patients10,11). In Vitro, fibrob