Ching-Huei Wang

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.

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.

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.