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EFFECT OF PARTIAL METAL REDUCTION ON THE CATALYTIC PROPERTY OF Fe/SiO2 IN CO HYDROGENATION
Moon, Sang Heup,Park, Chul Woong,Shin, Hyun Khil,Nam, In Sik,Lee, Jae Sung,Chung, Jong Shik 한국화학공학회 1991 Korean Journal of Chemical Engineering Vol.8 No.2
Effect of partial metal reduction on the property of supported iron catalysts has been studied using 9.1 wt% Fe/SiO₂ as a model catalyst and CO hydrogenation as a test reaction. The extent of iron reduction does not alter the intrinsic activity of iron nor distribution of the hydrocarbon products with specific carbon numbers, but significantly changes the olefin/paraffin ratio among the products. This kinetic behavior agrees with the result of gas chemisorption that the H₂/CO adsorption ratio decreases as the catalyst is reduced poorly. Well-reduced iron catalysts deactivate during the reaction because the carbon species deposited on the surface gradually transform into less-reactive ones as observed in the TPSR experiments.
Simulation of Silicon Film Growth by Silane Decomposition at Low Pressures and Temperatures
Moon, Sang Heup,Lee, Ju Hyung,Rhee, Shi Woo 한국화학공학회 1992 NICE Vol.10 No.3
Silicon film deposition by silence decomposition in LPCVD(Low Pressure Chemical Vapor Deposition) process has been simulated by numerical computation of the governing transport and reaction equations, assuming that the rate of silane decomposition in the gas phase controls the overall film growth rate. The film grouch rate and the film uniformity increase with the reattain flow rate when the flow rate is restively low, but they decrease at higher flow rates due to the negalive effect of the reduced reaction time in the reactor. Accordingly, the film deposition process is optimized 1y controlling the reactants flow rate so that the position of the maximum SiH₄-decomposition rate in the gas phase is located above the substrate region. With a larger degree of the substrate tilting, the growth rate decreases but the film uniformity is improved. The film uniformity is also improved when the pressure is low.
Moon, Sang Heup,Lee, Wha Young,Song, In Kyu 한국화학공학회 1991 NICE Vol.9 No.2
Changes in the structural and surface properties of 12-molybdophosphoric (abbreviated as PMo) and 10-molybdo-2-vanadophosphoric (abbreviated as PMo_(10)-V) acids as they are decomposed at high temperatures have been studied by IR, XRD. XPS, and TPD experiments. PMo_(12) simply decomposes into MoO₃ by heat-treatment at 580℃, but PMo yields a mixed oxide whose properties are different from those of either MoO₃, or V₂O_5. After the thermal decomposition, PMo_(12) loses the initial acidic and redox properties almost completely but PMo_(10)-V₂ retains some extent of the redox capability that is larger than that of MoO₃ and V₂O_5. The redox capability of the mixed oxide obtained by PMo_(10)-V₂ decomposition is correlated with its catalytic activity in oxidation processes.
Moon, Sang Heup,Lee, Ju Hyung,Rhee, Shi Woo 한국화학공학회 1992 NICE Vol.10 No.3
Deposition of silicon film by a mercury-sensitized photo-CVD process has been simulated by numerical solution of governing equations with proper boundary conditions. the results indicate that the film deposition rate is controlled by homogeneous decomposition of the reactants, silane, in the gas phase. The growth rate increases but the film uniformity decreases with the increase of reactants inlet concentration. Increase in the reactants flow rate decreases the deposition rate but gives no effect on the film uniformity. Among process variables, the light intensity and the mercury-saturator temperature are important parameters.
The Crystalline Quality of Si Films Prepared by Thermal - and Photo - CVD at Low Temperatures
Moon, Sang Heup,Rhee, Shi Woo,Chung, Chan Hwa,Han, Jae Hyun 한국화학공학회 1996 NICE Vol.14 No.2
Various silicon films were prepared by thermal and UV photo-CVD processes. The reactants were SiH₄, Si₂-H_6, SiH₂F₂, SiF₄, and H₂. Silicon films grown at temperatures below 5000 were either amorphous or crystalline depending on the process conditions, and the growth rates ranged between 5 and 80 Å/min. The film obtained by photo-CVD using fluoro-silanes as the reactants was crystalline even when the deposition temperature was as low as 250℃. Analyses o1 the film by RBS, SIMS, XRD, and ex-situ IR indicated that the film grown from silanes was contaminated by oxygen and other impurities while one from fluoro-silanes was relatively low in the impurities. The film crystallinity was higher in the latter case than the former.
Effect of Partial Metal Reduction on the Catalytic Property of Cobalt
Moon, Sang Heup,Yoon, Kwang Euy 한국화학공학회 1988 NICE Vol.6 No.3
Effect of partial metal reduction on the catalytic property of cobalt has been studied for Co/Al₂O₃ catalyst reduced to different extents. The sample catalysts have been tested for CO and HZ adsorption, CO hydrogenation, and Temperature Programmed Surface Reaction (TPSR). Major effect of the incomplete metal reduction on the surface property of cobalt is that hydrogen adsorption is significantly suppressed. This behavior is responsible to enhanced olefin production and retarded CO dissociation as observed for the catalysts of lower metal reduction. Changes in the kinetic parameters of CO hydrogenation on partially reduced cobalt may be explained from its gas adsorption behavior.
Removal of Organic Impurities from the Silicon Surface by Oxygen and UV Cleaning
Moon, Sang Heup,Chung, Chan Hwa,Kim, Chang Koo 한국화학공학회 1996 NICE Vol.14 No.4
We have studied the effect of oxygen and water vapor on the removal of organic impurities from the porous silicon surface under UV irradiation. Infrared spectrum observations of the treated surface suggest that decomposition of oxygen to produce ozone, atomic oxygen, and hydroxyl radical is a rate determination step for the overall cleaning process.