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In this study, we examined the effect of the textural properties of support materials on the palladium-catalyzed hydrogenation of succinic acid using mesoporous supports (MCM-41 and SBA-15). The physicochemical properties of these prepared heterogeneous catalysts were characterized by N2 adsorption–desorption, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). When palladium was loaded into the mesoporous supports by incipient wetness method, most palladium particles was incorporated inside the pore channels of SBA-15 support whereas the majority of particles were formed external to the pores of MCM-41 support. The small size of the palladium particles and the large pores of the Pd/SBA-15 catalyst enhanced the catalytic activity on the hydrogenation of succinic acid and the production of γ-butyrolactone (GBL) and tetrahydrofuran (THF); for Pd/MCM-41 catalyst, it was found that the large Pd particles and the small pore size enhanced the production of 1,4-butanediol (BDO). These catalysts showed promise as sustainable alternatives to current methods of manufacture for hydrocarbon derived products such as GBL, THF and BDO.

This study summarizes the available information on slush hydrogen and answer pending engineering questions that arise in the design of slush hydrogen propellant systems. The four methods for the production of slush are discussed. For storage, slush hydrogen must be pressurized, free from impurities, and continuously upgraded. Slush flowing at low flow rates has a higher viscosity than the liquid, however at higher velocities it approaches the viscosity of neat liquid. For the entire range of natural convection and nucleate boiling, the heat transfer at the triple-point temperature and pressure is nearly the same for the liquid and slush. The natural convection from smooth surfaces for slush can be predicted using available correlations. However, for engineering analysis and design of a system involving a slush cryogenic propellant, reliable information is required on production, flow, heat transfer, and instrumentation of these fluids. Some relevant and important aspects of slush hydrogen which have not yet been fully answered are presented.

Biodiesel is a renewable fuel which can be produced through an esterification reaction. The cost of feedstock which resulted in that of biodiesel is a large problem to be resolved. Dark oil from industrial process can be a better alternative for biodiesel production because of its low price. In spite of this, the study of biodiesel production using the dark oil has not been reported. This study provides technical information and catalytic properties on this system. Among the several catalysts, WO 3 /ZrO 2 catalyst was the most effective catalyst in the esterification of the dark oil to fatty acid methyl esters (FAMEs). The catalytic reaction parameters were optimized that 20 wt.% WO 3 /ZrO 2 has a high FFA conversion of 96% at 150 °C, 0.4 g/ml (oil), 1:9 (oil to alcohol, molar ratio) and 2 h reaction time. The physical and chemical properties of the catalyst were characterized by XRD, Raman spectrometer, BET and NH 3 -TPD.

The coulombic efficiencies of Pd–Au/C catalysts for the electrochemical oxidation of borohydrides were measured and the impregnated states of Pd–Au were characterized by XRD and XPS to find their relevance to the catalytic performances of the catalysts. The Pd–Au/C (metal wt.% = 20%) catalysts showed coulombic efficiencies of 50–70% under the given galvanostatic conditions, with maintaining a current density close to 20% Pd/C at voltammetric test, which is thought to be related to the mixed state of monometallic Au and Pd–Au alloy on the carbon support.

The heterogeneous base-catalyzed transesterification for biodiesel synthesis has been studied intensively over the last decade. This review classifies the solid base catalysts for transesterification into the following six categories based on Hattori’s classification: single metal oxides, mixed metal oxides, zeolites, supported alkali/alkaline earth metals, clay minerals (hydrotalcites), and non-oxides (organic solid bases). The catalysts in each category have acceptable catalytic activities overall, and follow specific catalyst design rules, although not completely systematically, thereby drawing the best activity from them. In parallel, each catalyst is not versatile and has some limitations specifically related to its catalytic structure and properties. This review focuses on the heterogeneous base-catalyzed transesterification in terms of catalyst development, based on the published research, especially over the last decade.

Biodiesel produced by the transesterification of vegetable oils (VOs) has recently become more attractive on account of its environmental and economical benefits. In this work, a heterogeneous catalyst system was developed for the production of biodiesel from used VOs using a continuous process. The free fatty acids (FFA) contained in the used VOs, which cause several severe problems in transesterification catalysis, were converted to fatty acid methyl esters (FAME) before the main biodiesel production process. The activities of several heterogeneous catalysts on the conversion of FFA were tested, with a WO 3 /ZrO 2 catalyst finally being selected. A method for preparing pellet-type catalysts was also developed. The pellet-type WO 3 /ZrO 2 catalyst showed highly active and durable catalytic activities in the continuous flow process. The steady state conversion of ca. 70% was obtained in a 140 h durability test. The acidic property and catalytic activity of WO 3 /ZrO 2 were attributed to the oxidation state of tungsten.

Isothermal vapor−liquid equilibrium data of the binary system 1,1-difluoroethane (HFC-152a) + propane (R-290) were measured in the temperature range from 273.15 K to 313.15 K at 10 K intervals and in the composition range from 0.2 to 0.8 mole fraction of propane. The temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation-type apparatus. The experimental data were correlated with the Carnahan−Starling−De Santis, Peng−Robinson, and Redlich−Kwong−Soave equations of state. Azeotropic behavior was revealed near 0.73 mole fraction of propane. The vapor pressure of the azeotropic system was compared with those of chlorodifluoroethane (HCFC-22) and the zeotropic mixture of difluoroethane (HFC-32) + pentafluoroethane (HFC-125) (50−50) (alternative refrigerant blend R-410A), the zeotropic mixture of HFC-32 + HFC-125 + 1,1,1,2-tetrafluoroethane (HFC-134a) (23−25−52) (alternative refrigerant blend R-407C), dichlorodifluoromethane (HCFC-12), and HFC-134a. It was found t...

Perovskite-type LaCoO 3 oxides were prepared by spray-freezing/freeze-drying method using citrate precursor. The calcination temperature for a single phase of LaCoO 3 could be lowered to 500 °C without formation of any other oxides and the product had the highest surface area of 23.7 m 2 /g. Below 500 °C, this catalyst with the perovskite structure and the high surface area showed higher activity for complete oxidation of low concentration methane (2000 ppm) and CO (1%) compared to Pt/Al 2 O 3 catalyst.

A method of measuring the thermal diffusivity of semi-infinite solid material at room temperature using photothermal displacement is proposed. In previous works, within the constant thickness of material, the thermal diffusivity was determined by the magnitude and phase of deformation gradient as the relative position between the pump and probe beams. In this study, however, a complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of parameters, such as, radius and modulation frequency of the pump beam and the thermal diffusivity, was studied. We propose a simple analysis method based on the zero -crossing position of real part of deformation gradient and the minimum position of phase as the relative position between two beams. It is independent of parameters such as power of pump beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.

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.

As technology advances with development of new materials, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. The measurement of thermal properties can be done in a non-contact way using photothermal displacement spectroscopy. In this work, the thermal diffusivity was measured by analyzing the magnitude and phase of deformation gradient. We proposed a new data analysis method based on the real part of deformation gradient as the pump-probe offset value. As the result, compared with the literature value, the measured thermal diffusivities of materials showed about 3% error.

In this paper, a novel fast response NDIR analyzer (FRNDIR), which uses an electrically pulsed semiconductor emitter and dual type PbSe detector for the PPM-level detection of carbon dioxide (CO2) at a wavelength of 4.28 μm, is described. Modulation of conventional NDIR energy typically occurs at 1 to 20 Hz. To achieve real time highspeed measurement, the new analyzer employs a semiconductor light emitter that can be modulated by electrical chopping. Updated measurements are obtained every one millisecond. The detector has two independent lead selenide (PbSe) with IR band pass filters. Both the emitter accuracy and the detector sensitivity are increased by thermoelectric cooling of up to —20 degrees C in all semiconductor devices. Here we report the use of semiconductor devices to achieve improved performance such that these devices have potential application to CO2 gas measurement and, in particular, the measurement of fast response CO2 concentration at millisecond level.

A fast response analyzer for measuring carbon dioxide concentration has been developed for transient characteristic and researches tested on internal combustion engine. The analyzer uses the well known NDIR(Non-Dispersive Infrared) method with miniaturized detection system, giving a time constant of approximately 30 microsecond, and sampling module consists of capillary tube. Since the transit time and the time constant of the sampling system depend on the sampling conditions, it is necessary to investigate the characteristics of sampling system before applied to exhaust gas measurement in engine. A unique method was designed to study the influence of the diameter of transfer sample line and operating conditions of the FRNDIR on transit time and time constant. A database of transit time and time constant was built up for different measured and simulated pressure conditions. The database can be used for correcting eventual concentration measurement.

A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of the parameters, such as radius and modulation frequency of the heating beam and the thermal diffusivity, was studied. Usually, thermal diffusivity was determined by the deformation angle and phase angle as the relative position between the heating and probe beams. In this study, we proposed the simple analysis method based on the real part of deformation gradient as the relative position between two beams. It is independent in the parameters such as power of heating beam, absorption coefficient, reflectivity, Poisson`s ratio, and thermal expansion coefficient.

Isothermal vapor−liquid equilibrium data of the binary system pentafluoroethane (HFC-125) + propane (R-290) were measured in the temperature range from 273.15 K to 313.15 K at 10 K intervals and in the composition range from 0.1 to 0.8 mole fraction HFC-125. Temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation-type apparatus. The experimental data were correlated with the Carnahan−Starling−De Santis, Peng−Robinson, and Redlich−Kwong−Soave equations of state. Azeotropic behavior was revealed near 0.77 mole fraction HFC-125. The vapor pressure of the azeotropic system is between those of chlorodifluoromethane (HCFC-22) and the zeotropic mixture of difluoroethane (HFC-32) + HFC-125 (50−50). This azeotropic system hasu good potential to replace the use of HCFC-22 as a refrigerant.

Isothermal vapor−liquid equilibrium data of the binary system difluoromethane (HFC-32) + pentafluoroethane (HFC-125) were measured in the temperature range from 268.15 K to 308.15 K at 10 K intervals and in the composition range from 0.1 to 0.8 mole fraction. Temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation type apparatus. The experimental data were correlated with the Carnahan−Starling−De Santis, Peng−Robinson, and Redlich−Kwong−Soave equations of state.

Isothermal vapor-liquid equilibrium data of the binary system of difluoromethane (HFC-32) + 1,1,1-trifluoroethane (HFC-143a) were obtained in the temperature range from 263.15 K to 313.15 K. Temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation type apparatus. The experimental data were correlated with the Canahan-Starling-De Santis, Peng-Robinson, and Redlich-Kwong-Soave equations of state.

The oxidation behavior of U-10 at% Zr alloy was studied using an X-Ray Diffractometer (XRD) and a thermogravimetric analyzer in the temperature range from 300 to 500 ‡C in air. From XRD, Infrared Spectroscopy (IR) and chemical analysis studies it was found that U-Zr alloy after complete oxidation was converted to U3O8 and ZrO2 broken into several pieces of thin plates and some blocks. From the slope value (l/n=0.562-0.872) of the log-log plots of the weight gain against time, the oxidation kinetics was analyzed by a paralinear equation. The activation energy of 20 % conversion of U-Zr alloy to U3O8 and ZrO2 was 57.02 kJ/mol and the oxidation rate per unit time and area was obtained to be : $$dw/dt = 1.41 \times 10^6 e\left( {\frac{{ - 57.02kJ/mol}}{{RT}}} \right)mg/min - cm^2 ,$$ (1) , where w, t and T are weight gain, time and temperature, respectively.

The thermodynamic properties of ideal gas air at low pressure (0.1 MPa) are newly calculated, using the most recent spectroscopic data for its components. The components of the 'ideal air' are nitrogen, oxygen and argon, with appropriate volume fractions. The thermodynamic properties of the components are computed by means of statistical thermodynamics using the molecular, physical and spectroscopic data in the new set of Joint Army-Navy-Air Force (JANAF) tables. Therefore, the resulting air table is thermodynamically consistent with the JANAF tables. The reference temperature of enthalpy and entropy is zero degrees kelvin and the reference pressure is 0.1 MPa. The temperature range of the table is 100-4000 K, which covers most engineering interests. In order to speed up the computation, approximate models are developed without any significant loss of accuracy. The new air tables are available in interactive computer codes format for microcomputers as well as in the conventional number-listing tables format. The enthalpy and specific heat of this study are within 0.05% of those of Keenan et al. (1980). The entropy of this study differs from that of Keenan et al. by a constant (=1.164 kJ kg -l K -l ). If the entropy of Keenan et al. is augumented by 1.164 kJ kg -1 K -1 , thermodynamic properties of Keenan et al. are in full agreement with those of this study. The enthalpy, specific heat and entropy of this study are also in full agreement with those of the NBS table and Vargaftik's table (1975) for real gas air.

The oxidation of U 3 Si was studied using a thermogravimetric analyzer and an XRD in the temperature range from 250 to 400°C in air. From XRD studies it was found that U 3 Si converted to UO 2 , U 2 O 5 and Si after 200 h at temperatures up to 275°C and it converted to UO 2 , U 3 O 7 , SiO and SiO 2 after 200 h at the temperature of 300°C. U 3 O 5 began to be formed at the temperature of 325°C. The linear reaction rate was observed at lower temperatures up to 275°C in the experimental range of reaction time. For higher temperatures, however, the reaction rate was nearly linear at initial stage of reaction and more sharply increased after a certain time due to cracking, breaking and pulverizing in the specimen. The reaction was controlled by diffusion rather than chemical reaction kinetics. The averaged rate assuming a linear rate equation could be expressed with activation energies that were 122.29 kJ/mol and 69.65 kJ/mol the temperature ranges of 250≤ T (°C) ≤ 300 and 300 ≤ T (°C) ≤ 400 respectively.

Tungsten oxide zirconia, sulfated zirconia and Amberlyst-15 were examined as a catalyst for a conversion of used vegetable oils (VOs) to fatty acid methyl esters (FAMEs). Among them, tungsten oxide zirconia was a promising heterogeneous catalyst for the production of biodiesel fuels from used VOs because of high activity in the conversion over 93% and no leaching WO 3 in the esterification reaction. The reaction conditions were optimized. A study for optimizing the reaction parameters such as the reaction temperature, stirring speed, WO 3 loading over ZrO 2 and reaction time, was carried out. The catalyst was characterized by BET, XRD, FT-IR, and NH 3 -TPD. With increasing WO 3 loading over ZrO 2 , the triclinic phase of WO 3 increased and the tetragonal phase of zirconia was clearly generated. The highest acid strength of 20 wt% tungsten oxide zirconia catalyst was confirmed by NH 3 -TPD analysis and the result was correlated to the highest catalytic activity of the esterification reaction.

In Korea Depleted Uranium(DU) is used in manufacturing a metallic nuclear fuel for the Korean Multi-Purpose Research Reactor(KMRR). In the manufacturing processes it produces DU chips and scraps as a waste material which composed of U-Ti, U-Zr, U-Mo and U-Si intermetallic compound. In this study Air Controlled Oxidizer(ACO) has been developed which facilitates DU to be converted into U308, the most stable form of uranium. Since DU chips oxidize rapidly and their heat of oxidation is very high(4.199kJ/g, U3O8), the inside temperature of the oxidizer is likely going up rapidly. Therefore the oxidizer must be able to be cooled properly or temperature increasement of the oxidizer must be under control. Kang et al.[1] reported for the oxidation of U-0.75wt%/o Ti chips in air that U308 was detected at the temperature above 350°C. And they[2] also reported that the maximum heat generation per unit time during oxidation was as follows:where Q was the maximum heat generation per unit timeWDU was the weight of DU loaded in ACOdw/dt was the reaction rateVair was the flow rate of input airR was the universal gas constantand T was the absolute temperature.From eq.(1) the maximum heat generation per unit time during oxidation is only function of the weight of DU loaded in ACO and the oxidation rate which is dependent on the oxidation temperature or the flow rate of input air.The ACO consists of an air flow meter, an air heater, an oxidation chamber with inner heater(capacity 7.5kW), an ash collection tank, a fly ash collector, a pressure gauge, a safety valve, and a soaking tank. The air flow meter is used to control the flow rate of input air below theoretical air requirement limit for the complete oxidation of DU. The inner heater is used to heat the inside of the oxidizer to an optimum oxidation temperature. The ash collection tank is used to collect uranium oxide powder after completion of oxidation. The fly ash collector is used both to collect flying ashes and to condense vaporized uranium oxide. Also, in ACO, DU chips are not ignited directly in order to prevent rapid temperature increasement. The oxidation environment only is achieved by heating the inside of oxidizer.To find effect of the oxidation temperature on the temperature of the oxidation chamber during treatment of DU, we conduct the experiment by changing heating rates of inner heater, 3, 4, 5 and 6kW, respectively. We conduct experiments for 120 minute with 2/min input air. However, it turned out that the complete oxidation is reached within 60 minute. After complete oxidation the weight gains of the DU chips is from 4.5 to 5.0 wt0/o and the DU chips are pulverized and they are converted to U 08 and 979 Mat. Res. Soc. Symp. Proc. Vol. 506 1998 Materials Research Society During the oxidation, maximum temperature increases to 470, 497.5, 572.5 and 6771C for heating rates 3, 4, 5 and 6kW, respectively. As the temperatures of the oxidation chamber outside surface are not exceed 1501C, however, DU chips are treated safely. In each experiment, weight before and after oxidation, the oxide forms of the product and the maximum temperature in the oxidation chamber during oxidation are shown in table 1. The maximum temperature profiles of the chamber inside and surface for time and heating rates are shown in Fig. I and 2, respectively.