Richard S. Horng

Preparation of activated carbons from raw and biotreated agricultural residues for removal of volatile organic compounds.

ABSTRACT Activated carbons with diverse physical and chemical properties were produced from four agriculture residues, including raw barley husk, biotreated barley husk, rice husk, and pistachio shell. Results showed that with adequate steam activation (30–90 min, 50% H2O(g)/50% N2), activated carbons with surface areas between 360 and 950 m2 g−1 were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Biotreated agricultural residues were found to be suitable precursors for producing mesoporous activated carbons. The oxygen content of activated carbons increased with increasing activation time. Results from X-ray photoelectron spectroscopy examination further suggested that H2O molecules react with the carbon surface, enhancing the deconvoluted peak area of carbonyl and carboxyl groups. Equilibrium adsorption of toluene indicated that the adsorption capacities increased with an increase in the inlet toluene concentration and a decrease in temperature. The adsorption isotherms were successfully fitted with Freundlich, Langmuir, and Dubinin– Radushkevich equations. Activated carbons derived from agricultural residues appear to be more applicable to adsorb volatile organic compounds at a low concentration and high-temperature environment. IMPLICATIONS This paper presents data on the preparation of activated carbons from agricultural residues, especially the waste from biohydrogen generation. Experimental results indicated that with proper carbonization and steam activation, activated carbons with diverse characteristics can be produced from various agricultural residues. The resulting activated carbons effectively adsorb toluene. This work provides useful information for reutilization of these agricultural residues, helping in decreasing the cost of biological waste treatment and providing a cost-effective alternative to conventional adsorbent production and application.

Thermal performance and durability properties of the window glazing with exterior film(s)

Solar control film is usually positioned on the interior side of the window to reduce heat radiation into buildings. This work, in contrast, investigates the thermal performance and durability properties of window glazing with film on the exterior side and glazing with an additional TiO2 layer, as a protective film, on the exterior side. A small-sized hot-box was developed to evaluate the performance of glass samples: low-E glass, clear glass with solar film and tinted glass with TiO2 coating. It was concluded that the glass with coating facing toward outdoor could result in a reduction of interior surface temperature by 2℃–7℃. The thermal discomfort caused by these exterior films for the occupants would therefore be lowered. Experiments on surface properties found that heat treatment could provide improved durability properties for low-E and TiO2 glass samples. Adding another TiO2 layer to the low-E or solar films was found to exhibit even lower interior temperatures. An energy analysis showed that the heat transfer rate to the building inside was reduced by 25.8% for TiO2/solar film on the exterior compared to the low-E glass with film facing inside. TiO2/solar film placed on the exterior side is therefore highly recommended for window glazing by this study.

Multicriteria Evaluation of the Selection of Green Glazing Material by Using the Analytic Hierarchy Process (AHP)

The window glazing system provides comfortable living environment for residents and also exhibits the esthetics of architectural design. Its quality is dependent upon glass material selection; there are many factors determining glazing material selection, which might further affects the building safety and energy savings. An analytic hierarchy process (AHP) is used to analyze the trade-off of these impact factors. In the survey, both positive and negative impact factors on the glazing material selection are considered. The results, based on 40 expertise questionnaires, indicated that “performance”, in overall, was perceived to be most important core selection criterion for the green glazing material, but among all assessed items, “hazardous substance release” was concerned the most. The “appearance” was regarded as a minor factor in this analysis. In addition, BIPV alternative was also ranked in the first position regardless of criteria weight variations. The results provide valuable information for building material manufacturers, architects and interior designers in selecting glass material in their the glazing system.

Thermal and optical properties of semi-transparent amorphous silicon BIPV for building application

A new type of poly-crystalline amorphous thin film photovoltaic module with high visible light transmittance was developed for use in a building. The method of PECVD (Plasma-enhanced chemical vapor deposition) was applied to produce satisfactory high color rendering index (HCRI) BIPV module of good quality with visible light transmittance as high as 26.9%, solar radiation absorptance below 60% and shading coefficient equal to 54%. The thermal and optical properties of HCRI BIPV module are studied in some detail and the results reported. The thermal conductivity and diffusivity of HCRI BIPV module are less than that of Si-based BIPV. The HCRI-BIPV module appeared to be effective in improving the visible transmittance and reducing the absorptance, but the value of SC of HCRI-BIPV module was higher than that of Si-based BIPV. This indicates that there is still a trade-off between day lighting and thermal insulation for designing an optimal BIPV module. Further thermal performance work conducted by a small-sized hot-box with a solar simulator lamp revealed that heat is mostly absorbed by the HCRI-BIPV and a small amount of heat is conducted into building. The surface temperature on both sides of Si-based BIPV reached a steady state is faster than that of HCRI-BIPV due to the higher thermal diffusivity. This can have important practical implications on the fabrication of low-cost, high visible light transmittance of BIPV module.

Chemical sensors using surface acoustic wave devices on proton-exchanged LiNbO/sub 3/

Waveguides provide several advantages such as acoustic beam confinement, prolongation of delay time, and high acoustic intensity to acoustic devices. Using proton exchange, waveguides on Z-cut and Y128/spl deg/-cut LiNbO/sub 3/ crystals were applied to investigate chemical detection in a dilute conductive solution. The changes in velocity and the attenuation as a function of conductivity of the solution are discussed. Theoretical calculations obtained through perturbation theory are compared with experimental results. From the measurement, it is clearly indicated that the surface acoustic wave can be used to detect the conductivity of the dilute electrolyte. For Z-cut LiNbO/sub 3/, proton-exchanged devices exhibit higher sensitivity than unexchanged devices. The dielectric constant of proton-exchanged layer is not easily directly measured; however, it can be calculated from the critical conductivity.

Pressure influences on CO2 reaction with cyclohexylamine using ionic liquid as reaction medium and catalyst

Abstract Inserting carbon dioxide (CO2) into ammonia molecules to produce urea is a traditional CO2 utilization method. An ionic liquid (IL), 1-butyl-3-methylimidazolium bromide ([Bmim]Br), was used as reaction medium and [Bmim]Br/KOH as catalyst. This study investigates CO2 carbonylation of cyclohexylamine and its reaction performance in a number of low- and high-pressure CO2/IL systems. The reaction yield was greatly increased as pressure ranges changed from 15–50 bar to 80–100 bar; the physiochemical properties of substrates and catalyst were greatly affected by CO2 in supercritical state. The yield was improved from 69% at 30 bar to 91.6% at 100 bar, much better than a previous study result of 53.5%, but as pressures further increased, a significant decrease was observed. The reaction activation energy was calculated to be 3.942 and 4.354 kcal/mol in mild and supercritical conditions. This process shows a low threshold reaction energy and great potential for industrial applications to store CO2 in amine molecular structures.

Stepwise Inhibition Effect of Multinitroxyl Radicals on Styrene Polymerization

Several nitroxides are used for study of their inhibiting effect on styrene polymerization. These nitroxides contain different nitroxyl moieties within molecules. Molecules with multinitroxyl centers within a single molecule possess stepwise radical killing reactivity. Each of these nitroxyl centers exhibits slightly different inhibitory capabilities in terminating the growth of polymer chains. A kinetic model is developed to calculate individual inhibition constants for each molecules nitroxyl center and to characterize their kinetic behavior.

Surface Acoustic Wave Sensors on Proton-Exchanged Z-Cut LiNbO3

Waveguides provide several advantages such as acoustic and optical beam confinement, prolongation of delay time, and high acoustic intensity for the acoustic devices. Using proton exchange (PE) with benzoic acid, we have investigated the surface acoustic wave (SAW) properties of a PE waveguide using Z-cut LiNbO3. With this tight energy confinement, the acoustic waveguide structure enables the guided SAW to be in a suitable mode for dilute electrolyte sensing. Furthermore, it is noteworthy that the dielectric constant of a PE layer can be deduced from the critical conductivity.