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Study on the Reaction Mechanisms of Gas-liquid Phase of Nitrogen-containing Pollutants over Nanoscale Copper Catalyst

by Hung, Chang-Mao

Abstract (Summary)
Ammonia is one of valuable chemicals, which are commonly used, in various industrial factors. It is also a typical pollutant, and has a long-term impact on human health for its toxicity characteristics. This study investigated the reaction mechanism of gas-liquid phase in oxidation of ammonia in WAO and SCO processes over copper catalysts. As for lack of the research on activated center of copper catalyst for a long time, it was still not exactly unknown what center was going on affecting activity. Therefore, we conducted the physical and chemical properties on surface of catalyst to realize conversion/activity in oxidation of ammonia over nanoscale copper catalyst. Achievements in oxidation of liquid phase ammonia in WAO process over nanoscale Cu-La-Ce catalysts are as follows: (1) The raising on conversion of ammonia is significantly by adding the molar ratio 7:2:1 of Cu-La-Ce catalyst. (2) The higher temperature the higher conversion, and the increasing space velocity of influent the lower conversion. (3) The reaction rate in WAO process over 7:2:1 catalyst increases with initial pH increasing of solution, 95% conversion of ammonia can be achieved under alkalinity condition. (4) Oxygen supply can promote the decomposition of ammonia at high temperature, above 95% conversion of ammonia can be achieved when total pressure raises at 4.0 MPa. (5) The characteristic peaks of CuO, La2O3 and CeO2 showed from XRD tests indicate the coordination by three peaks probably causes the excellent activity in Cu-La-Ce catalysts; UV-Vis and FTIR analysis results show CuO species dominates the reaction mechanism of liquid phase of WAO process over Cu-La-Ce catalyst which can be used to adsorb the oxygen atom in proceeding the oxidation of ammonia. (6) AEM and TEM analysis results show the outlook of catalyst sites are almost nearly circular and its particle sizes are concentrated in range of nanoscale level; and by EDS and Mapping tests proof elements of Cu, La and Ce are indeed the major components in this catalyst. Achievements in oxidation of liquid phase ammonia in WAO process over nanoscale Cu-ACF catalysts are as follows: (1) The dose of copper on activated carbon fiber support (denoted by ACF) is important in treatment efficiency of pollutants removal; adding at least 5% of copper dosage which can maintain Cu to be a state of +2, it has the catalytic capacity to convert the ammonia in solution. (2) The optimal conversion obtained in 99% under 463 K and 400 mg/l, shows Cu-ACF is also an alterative catalyst. (3) The higher temperature the higher conversion, and the lower nitrogen is. (4) The higher oxygen pressure the higher conversion. (5) From analysis results of BET, FTIR and EA show ACF support has high BET surface area and oxygen-containing function groups, it causes an increasing activity of metal in reaction for the higher activated sites and metal dispersed uniformly on ACF; XRD tests indicate the coordination by CuO and ACF probably causes the excellent activity over Cu-ACF catalysts; UV-Vis and FTIR analysis results show species CuO and ACF both dominate the reaction mechanism of liquid phase of WAO process over Cu-ACF catalyst. (6) AEM and TEM analysis results show the outlook of catalyst sites are almost Nearly long narrowed tube and its diameters are concentrated in range of nanoscale level; and by EDS and XRF (Mapping) tests proof elements of Cu and P are indeed the major components in this catalyst. Achievements in oxidation of gas phase ammonia in SCO process over nanoscale Cu-Ce catalysts are as follows: (1) The great conversion over Cu-Ce catalyst (molar ratio 6:4) obtained under 463 K and 400 mg/l. (2) The higher initial concentration of ammonia the lower conversion is probably due to the intermediates out of completely decomposed in catalytic reaction. (3) From analysis results of BET and EA show this catalyst have high BET surface area and empty hole of oxygen-containing on surface, it causes an increasing activity of metal in reaction for the higher activated sites; XRD tests indicate the coordination by CuO and CeO2 probably causes good activity over Cu-Ce catalysts; UV-Vis and FTIR analysis results show species CuO and CeO2 both dominate the reaction mechanism of gas phase of ammonia in SCO process over Cu-CeO2 catalyst. (4) AEM and TEM analysis results show the outlook of catalyst sites are almost nearly circular and its particle sizes are concentrated in range of nanoscale level; and by EDS and Mapping tests proof elements of Cu and Ce are indeed the major components in this catalyst. Achievements in oxidation of gas phase ammonia in SCO process over nanoscale Pt-Pd-Rh catalyst coated on ceramics are as follows: (1) The 99% conversion over this catalyst can be obtained at 623 K; the higher initial concentration of ammonia ranging from 500 to 1000 mg/l the lower conversion is found. (2) The large amount of N2 and minor amount of NO and NO2 are found in the products after this reaction. (3) XRD tests indicate the coordination by Pt, PdO, Rh and CeO2 probably causes the excellent activity over this catalyst; UV-Vis and FTIR analysis results show species PdO and CeO2 both dominate the reaction mechanism of gas phase of ammonia in SCO process over Pt-Pd-Rh catalyst. (4) AEM and TEM analysis results show the higher initial concentration the higher aged the ceramic support, and the wider sintering of Al2O3 coating layer is. (5) By EDS, XRF and Mapping tests proof elements of Pt, Pd and Rh are indeed the major components dispersed on this ceramic catalyst.
Bibliographical Information:

Advisor:Ming-Shean Chou; Shui-Jen Chen; Kang-Shin Chen; Wen-Jhy Lee; Jie-Chung Lou; Jimmy C. M. Kao

School:National Sun Yat-Sen University

School Location:China - Taiwan

Source Type:Master's Thesis

Keywords:ammonia containing solution wao proces

ISBN:

Date of Publication:06/25/2003

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