Shiow-Shyung Lin

Wet air oxidation of a reactive dye solution using CoAlPO4-5 and CeO2 catalysts

Wet air oxidation of a prepared reactive dye solution was performed to assess the efficacy of CoAlPO(4)-5 and CeO(2) as catalysts in the reaction. Via adsorption and oxidation of dye, CoAlPO(4)-5 effectively decreased American Dye Manufacturers Institute and chemical oxygen demand (COD) values in the dye solution. At a reaction temperature of 135 degrees C and an applied pressure of 1.0 MPa, color and COD removal were as high as 95% and 90%, respectively, after 2 h. Active sites on the outer surface of CoAlPO(4)-5 are responsible for adsorption and decomposition of dye while active sites in the pores dominate further destruction and oxidation of intermediate products. Since the outer surface only represents a minor part of the total surface, the color removal does not increase appreciably with loading of CoAlPO(4)-5. The CeO(2) catalyst, calcined from cerium chloride under high thermal impact (type A CeO(2)) was very effective in removing color and COD from the solution. This catalyst demonstrated near 100% color removal at temperatures above 135 degrees C and the COD removal could be above 95% at 165 degrees C. With both CoAlPO(4)-5 and CeO(2) catalysts, COD rose and then fell back during the reaction, a feature typical of a consecutive reaction. In contrast to prepared CeO(2), a commercial CeO(2) did not exhibit any catalytic ability for the removal of color and COD. The durability of both CoAlPO(4)-5 and prepared CeO(2) is considered to be fair.

The promoter effect and a rate expression of the catalytic incineration of (CH3)2S2 over an improved CuO–MoO3/γ-Al2O3 catalyst

The CuO-MoO3/gamma-Al2O3 catalyst, confirmed previously as having good activity in the catalytic incineration of (CH3)2S2, was employed as the principal catalyst in this study. With the aim of improving catalyst activity and resistance to deactivation by sulfur compounds, a promoter was added either before adding the precursors of Cu and Mo or together with Cu and Mo onto the gamma-Al2O3. Promoters included transition metals and elements from groups IA-VIIA in the chemical periodic table. Experimental results reveal Cr2O3 as the most effective promoter, with an optimal composition of 5 wt.% Cu, 6 wt.% Mo and 4 wt.% Cr (designated as Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3). Knowing that higher acidity can improve activity, we further investigated the effect of acid treatment on the performance of the Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3 catalyst. Experimental results indicate the H2SO4-treated catalyst (Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3) has a better activity and durability. A study for finding an appropriate rate expression for the catalytic incineration of (CH3)2S2 by Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3 was carried out in a differential reactor. The results show that the Mars-Van Krevelen model is applicable to this destructive oxidation reaction. Results additionally reveal that competitive adsorption of CH4 reduces conversion of (CH3)2S2.

Catalytic wet air oxidation of phenol using CeO2 as the catalyst. Kinetic study and mechanism development

ABSTRACT Using a CeO2 catalyst prepared from CeCl3 ċ 7H2O under high thermal impact, the catalytic wet air oxidation (CWAO) of phenol was effectively implemented. With initial phenol concentrations of between (400 and 2500) mg/L, and at a temperature of 160°C, the rate of phenol conversion increased with increased catalyst loading (0.2 g/L–1.0 g/L) and oxygen pressure (0.5 MPa–1.5 MPa). Even at an initial concentration of 2500 mg/L, conversion of phenol was as high as 95% after 3 h reaction. The effect of phenol concentration, catalyst loading, and oxygen pressure on the initial rate of phenol conversion was evaluated in a kinetic study. The initial rate equation derived from kinetic study is: R o = k 1 × [Ph]1.3–1.4 × W0.5–0.6 × Po 2 0.9–1.1, where k 1 is a rate constant, and [Ph], W and Po 2 refer to phenol concentration, catalyst loading and oxygen pressure, respectively. A free-radical involved reaction mechanism was proposed and an initial rate expression based on this mechanism was derived: R o = k 2 × [Ph]1.5 × W0.5, where k 2 is also a rate constant. Fitting of experimental data with the theoretically derived initial rate equation resulted in good correlation: the coefficient is greater than 0.99.

Effect of oxygenates on exhaust emissions from two-stroke motorcycles.

ABSTRACT The advantages of adding oxygenates to gasoline include their raising of the octane rating and their ability to reduce toxic compounds in the gasoline. A study of impacts of various oxygenates used in 50 cc two-stroke motorcycle fuel was conducted, using the two most popular motorcycles in Taiwan, to determine the effect of oxygenates on exhaust emissions. Oxygenates used in the study were methanol, ethanol, benzene, methyl tert-butyl ether (MTBE) and isopropyl ether (IPE). Addition of oxygenates effectively reduced exhaust emissions. Of the oxygenates tested, with oxygenate content 7% by volume, MTBE was found to be the most suitable for reducing exhaust emissions. Results showed that total hydrocarbon (THC), CO, and NO x emissions decreased by 50%, 70%, and 60%, respectively, compared with emissions without any oxygenate added.

THE KINETICS OF CATALYTIC INCINERATION OF (CH3)2S2 OVER THE CuO–MoO3/γ-Al2O3 CATALYST

ABSTRACT In this study, by varying reaction conditions including particle size, space velocity, reactant concentration and reaction temperature, the kinetics of catalytic incineration of (CH3)2S2 catalyzed by the CuO–MoO3/γ-Al2O3 catalyst was investigated. Three kinetic models, i.e., the power-rate law model, Langmuir-Hinshelwood model and Mars-Van Krevelen model, were applied to best fit the experimental results. It was shown that the Mars-Van Krevelen model was more appropriate than the other two models for describing the mechanism of catalytic incineration of (CH3)2S2 on the CuO–MoO3/γ-Al2O3 catalyst. The reaction expression of the Mars-Van Krevelen model was as follows: where α is 5.5 and C R and C O represent concentrations of (CH3)2S2 and O2, respectively. The enlarged difference between experimental and predicted data was observed at higher operating temperatures. This might be due to the dominating mechanism at this temperature region was different.

WET AIR OXIDATION OF A DIRECT DYE SOLUTION CATALYZED BY CoAlPO4-5. PERFORMANCE ASSESSMENT AND KINETIC STUDY

Wet air oxidation (WAO) of a prepared direct dye solution was tested by using the CoAlPO4-5 catalyst. Addition of CoAlPO4-5 could effectively improve rate of color removal and the activation energy of color removal could decrease from about 110 kJ/mole to about 75 kJ/mole as the catalyst loading was increased from 0.0 g/L to 3.0 g/L. Performance of WAO on color removal would somewhat increase with catalyst loading at 145°C whereas the effect of catalyst loading was not significant at 135°C. With no addition of CoAlPO4-5, the chemical oxygen demand (COD) value was low. This was due to difficulty of exactly measuring the true COD value of dye solution if the dye was not degraded. Via CoAlPO4-5, COD of dye solution could be effectively decreased. The rate of COD removal would increase with catalyst loading, oxygen pressure and reaction temperature. Furthermore, a maximum COD value observed, which was due to catalyzed degradation of dye molecule via CoAlPO4-5, could be characterized by a consecutive reaction scheme. Kinetic study of color removal is expressed as follows: rate = k × [dye]0.8 × W 0.5 × P n (145°C) or rate = k × [dye]0.8 × W 0 × P n (135°C); where k means rate constant, [ ] means concentration, W means catalyst loading, P means oxygen pressure and n means uncertain number.

Effect of catalyst preparation conditions on the hydrodesulfurization of thiophene over Co-Mo/γ-Al2O3

ABSTRACT The purpose of this research was to study the effects of preparation conditions on the catalytic properties of the Co-Mo/γ-Al2O3 catalyst. The work included catalyst preparations and reactions. In the preparations, cobalt-impregnated Mo/γ-Al2O3 (designated as IcIM) was found to have a promoting effect on the hydrodesulfurization (HDS) of thiophene. Activity and stability of IcIM was higher than that of Mo/γ-Al2O3. Conversely, when cobalt was added onto Mo/γ-Al2O3 by the mechanical mixing method, no promoting effect was observed. Mo/γ-Al2O3 was also prepared using the two different methods (incipient impregnation or mechanical mixing). The differently prepared Mo/γ-Al2O3 resulted in no obvious difference in activity of IcIM. It was further found that Co-Mo/γ-Al2O3 activity initially increased appreciably with Mo content and leveled off at Mo contents above 9 wt.%. The catalyst exhibited a maximum activity at Co/Mo ratio 0.3. The order in which metal species were added had a great influence on the activity of the Co-Mo/γ-Al2O3 catalyst. Higher activity was obtained when Co was added into Mo/γ-Al2O3 as opposed to Mo added into Co/γ-Al2O3.

Study on Catalytic Incineration of Methane Using Cr2O3/γ-Al2O3 as the Catalyst

Abstract A fixed bed reactor was employed to investigate the catalytic incineration of CH4 by various supported transition metal oxide catalysts, with a view of finding the optimal one. Results indicated that the active species, the support, the metal content, the weight hourly space velocity (WHSV), and the inlet CH4 concentration were all important factors affecting CH4 oxidation. Cr2O3/γ-Al2O3 was found to be the most active catalyst among the seven γ-Al2O3-supported metal oxide catalysts tested. With Cr2O3 as the active species, γ-Al2O3 was the most suitable of six supports tested. Furthermore, the optimal Cr content of Cr2O3/γ-Al2O3 was 9 wt.%. X-ray diffraction (XRD) patterns showed that it was formation of Cr2O3 crystals that caused a decline in catalyst activity at Cr content above 9 wt.%. Using the optimal Cr2O3/γ-Al2O3 catalyst, CH4 was completely oxidized at about 390°C, much lower than the temperature required by noble metal catalysts for the same outcome. The stability of Cr2O3/γ-Al2O3 was good and was not affected by the reaction temperature, demonstrated by a nearly constant conversion rate of CH4 of 57% at 350°C and 97% at 380°C during a 20 h on-stream test. However, WHSV and inlet concentration of CH4 did affect CH4 conversion noticeably. For complete oxidation of CH4, the reaction temperature required increased with WHSV and inlet CH4 concentration.

Gas transport properties of CoAlPO4‐5/PC membranes

The transport phenomena of oxygen and nitrogen across a pure polycarbonate (PC) and CoAlPO4-5/PC membranes were studied. Various CoAlPO4-5 membranes with different cobalt content were added to polycarbonate membranes to improve the gas transport performance. Oxygen and nitrogen isotherms were studied. Solubility of oxygen and nitrogen was greatly increased by adding CoAlPO4-5 to the membranes, which also resulted in a higher solubility ratio of oxygen to nitrogen. It might be that a pinhole of the membrane caused the increase in diffusivity and a decrease in selectivity when excess CoAlPO4-5 was added. The results also showed that CoAlPO4-5 with a higher cobalt content would more effectively increase the gas solubility, but make only a minor change in the solubility ratio of oxygen to nitrogen. It was found that the increase in oxygen to nitrogen selectivity was mainly due to an increased diffusivity ratio of oxygen to nitrogen when CoAlPO4-5 was added into the membranes.