• Journal of Environmental Science International
• /
• v.17 no.12
• /
• pp.1307-1314
• /
• 2008

Hydrogen gas is used as a fuel for the proton exchange membrane fuel cell (PEMFC). Trace amount of carbon monoxide present in the reformate $H_2$ gas can poison the anode of the PEMFC. Therefore, preferential oxidation (PROX) of CO is essential for reducing the concentration of CO from a hydrogen-rich reformate gas. In this study, conventional Pt/$Al_2O_3$ catalyst was prepared for the preferential oxidation of CO. The effects of catalyst preparation method, additive, and hydrogen on the performances of PROX reaction of CO were investigated. Water treatment and addition of Ce enhanced catalytic activity of the Pt/$Al_2O_3$ catalyst at low temperature below $100^{\circ}C$.

• Journal of Environmental Science International
• /
• v.18 no.10
• /
• pp.1071-1077
• /
• 2009

A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below $100^{\circ}C$. This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was continued by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below $100^{\circ}C$.

• Korean Chemical Engineering Research
• /
• v.51 no.4
• /
• pp.432-437
• /
• 2013

The CO preferential oxidation reaction (PROX) has been done using Cu catalytic active species supported on some of mesoporous silica materials which can facilitate the diffusion of the reactants in order to prevent the poisoning of anode active materials by CO molecules during driving polymer electrolyte fuel cells (PEMFC) in this study. As a result when SBA-15 with large pore used as a support showed excellent CO oxidation activity, especially the activity increased in proportion to the amount of supported Cu. Ti components which was inserted to increase the degree of dispersion of Cu, contributed to improving the performance for CO oxidation at low-temperature. The degree of dispersion of Cu ingredients was the best in the catalyst inserted 20 mol-% Ti into the framework of SBA-15, and CO oxidation activity was also improved.

• Journal of Hydrogen and New Energy
• /
• v.23 no.6
• /
• pp.640-646
• /
• 2012

The effect of Ce promotion over 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts on the CO conversion and $CO_2$ selectivity was investigated in preferential CO oxidation (PrOx) to reduce the CO concentration less than 10 ppm in excess $H_2$ stream for polymer electrolyte membrane fuel cell (PEMFC). Ce-promoted 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts were prepared by incipient wetness impregnation method and the loading amount of Pt was fixed at 1wt%. The content of Ce promoter which has excellent oxygen storage and transfer capability due to the redox property was adjusted from 0 to 1.5wt%. Ce-promoted 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts exhibit high CO conversion and $CO_2$ selectivity at low temperatures below $150^{\circ}C$ due to the improvement of reducibility of surface PtOx species compared with the 1wt% $Pt/{\gamma}-Al_2O_3$ catalyst without Ce addition. When Ce content was more than 1wt%, the catalytic activity was decreased at over $160^{\circ}C$ in PrOx because of competitive $H_2$ oxidation. As a result, 0.5wt% Ce is optimal content not only to achieve high catalytic activity and good stability at low temperatures below $150^{\circ}C$ in the presence of $CO_2$ and $H_2O$ but also to minimize the $H_2$ oxidation at high temperatures.

• Journal of Hydrogen and New Energy
• /
• v.24 no.5
• /
• pp.353-358
• /
• 2013

To develop preferential CO oxidation reaction (PROX) catalyst for small scale hydrogen generation system, supported Pt catalysts have been applied for the target reaction. The supports were systematically changed to optimize supported Pt catalysts. $Pt/Al_2O_3$ catalyst showed the highest CO conversion among the catalysts tested in this study. This is due to easier reducibility, the highest dispersion, and smallest particle diameter of $Pt/Al_2O_3$. It has been found that the catalytic performance of supported Pt catalysts for PROX depends strongly on the reduction property and depends partly on the Pt dispersion of supported Pt catalysts. Thus, $Pt/Al_2O_3$ can be a promising catalyst for PROX for small scale hydrogen generation system.

• Journal of Hydrogen and New Energy
• /
• v.17 no.3
• /
• pp.293-300
• /
• 2006

KIER has been developing a Ru-based preferential oxidation catalysts and a novel fuel processing system to provide hydrogen rich gas to residential PEMFCs system. The catalytic activity of Ru-based catalysts was investigated at different Ru loading amount and different support structure. The obtained result indicated that 2 wt% loaded Ru-based catalyst supported on ${\alpha}-Al_2O_3$ showed high activity in low temperature range and suppressed the methanation reaction. The developed prototype fuel processor showed thermal efficiency of 78% as a HHV basis with methane conversion of 92%. CO concentration below 10 ppm in the produced gas is achieved with separate preferential oxidation unit under the condition of $[O_2]/[CO]=2.0$. The partial load operation have been carried out to test the performance of fuel processor from 40% to 80% load, showing stable methane conversion and CO concentration below 10 ppm. The durability test for the daily start-stop and 8 h operation procedure is under investigation and shows no deterioration of its performance after 50 start-stop cycles. In addition to the system design and development.

• Journal of Hydrogen and New Energy
• /
• v.17 no.3
• /
• pp.241-247
• /
• 2006

The catalytic performances for CO preferential oxidation in hydrogen-rich fuels were investigated by varying the types of alumina supports, additives excluding platinum, and synthetic methods of impregnation and sol-gel synthesis. The reactions were conducted in the range of $25{\sim}300^{\circ}C$ over Pt, Co, and/or Na impregnated catalysts supported on commercial gamma-alumina, pseudoboehmite, or sol-gel derived xerogels. Catalytic activities were enhanced by cobalt addition due to strong Pt-Co interactions in the bimetallic phase. Additional sodium promoted not only the formation of the Pt-Co bimetallic interphase but also oxygen adsorption capability, giving rise to increase in the CO oxidation rate at lower temperatures. Moreover, chemical interaction between Pt and Co was considerably enhanced by sol-gel synthesis.

• Journal of Hydrogen and New Energy
• /
• v.21 no.5
• /
• pp.390-397
• /
• 2010

0.5wt% Ru/$\alpha-Al_2O_3$ catalysts are prepared by deposition-precipitation method for the preferential CO oxidation In order to investigate the effect of pH on the Ru dispersion and particle size, the pH of precursor solution is adjusted to between 5.5 and 9.5. 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH of 6.5 has high Ru dispersion of 17.9% and small particle size of 7.7nm. In addition, 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH 6.5 is easily reduced at low temperatures below $150^{\circ}C$ due to high dispersion of $RuO_2$ particle and shows high CO conversion over 90% in the wide temperature range between $100^{\circ}C$ and $160^{\circ}C$. Moreover, the deposition-precipitation is a feasible method to improve the Ru dispersion as compared to the impregnation method. The 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared by deposition-precipitation exhibits higher CO conversion than 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts prepared by impregnation due to higher metal dispersion and better reducibility at low temperature.

• Journal of the Korean Society of Combustion
• /
• v.18 no.4
• /
• pp.37-43
• /
• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• Journal of Hydrogen and New Energy
• /
• v.27 no.5
• /
• pp.503-509
• /
• 2016

Fuel cell is a device for producing electricity by using the hydrogen produced by the fuel processor. At this time, CO is also created by the fuel processor. The resulting CO enters the stack where is produce electricity and leads to the adsorption of anode catalyst, finally the CO poisoning occurs. Stack which occurred CO poisoning has a reduction in performance and shelf life are gradually fall because they do not respond to hydrogen. In this paper, experiments that using a PROX reactor to prevent CO poisoning were carried out for removing the CO concentration to less than 10ppm range available in the fuel cell. Furthermore experiments by the PROX reaction was designed and manufactured with a water-cooling heat exchange reactor to maintain a suitable temperature control due to the strong exothermic reaction.