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1.
Park Joo-Hyoung Cho Hyun Ju Park Sang Jun Nam In-Sik Yeo Gwon Koo Kil Jeong Ki Youn Young Kee 《Topics in Catalysis》2007,42(1-4):61-64
Co/Pt/Ba/γ-Al2O3, Co/Ba/γ-Al2O3, Pt/Ba/γ-Al2O3, Co/Pt/γ-Al2O3, Ba/γ-Al2O3, Pt/γ-Al2O3, and Co/γ-Al2O3 type catalysts were prepared by a conventional impregnation method, and their NO
x
storage capacities were evaluated by colorimetric assay. Co-containing catalysts had a higher NO
x
storage capacity than that of Co-free counterparts. The role of each component, especially Co, for the catalysts prepared
was investigated by using in-situ FTIR. The high NO
x
storage for Co-containing catalysts including Co/Ba/γ-Al2O3 and Co/Pt/Ba/γ-Al2O3 is mainly due to the formation of Co3O4 on the catalyst surface identified by XAFS. 相似文献
2.
Deactivation and coke formation on palladium and platinum catalysts in vegetable oil hydrogenation 总被引:1,自引:0,他引:1
Jonas Edvardsson Petri Rautanen Anders Littorin Mikael Larsson 《Journal of the American Oil Chemists' Society》2001,78(3):319-327
Deactivation of palladium and platinum catalysts due to coke formation was studied during hydrogenation of methyl esters of
sunflower oil. The supported metal catalysts were prepared by impregnating γ-alumina with either palladium or platinum salts,
and by impregnating α-alumina with palladium salt. The catalysts were reused for several batch experiments. The Pd/γ-Al2O3 catalyst lost more than 50% of its initial activity after four batch experiments, while the other catalysts did not deactivate.
Samples of used catalysts were cleaned from remaining oil by repeated extractions with methanol, and the amount of coke formed
on the catalysts was studied by temperature-programmed oxidation. The deactivation of the catalyst is a function of both the
metal and the support. The amount of coke increased on the Pd/γ-Al2O3 catalyst with repeated use, but the amount of coke remained approximately constant for the Pt/γ-Al2O3 catalyst. Virtually no coke was detected on the Pd/α-Al2O3 catalyst. The formation of coke on Pd/α-Al2O3 may be slower than on the Pd/γ-Al2O3 owing to the carrier’s smaller surface area and less acidic character. The absence of deactivation for the Pt/γ-Al2O3 catalyst may be explained by slower formation of coke precursors on platinum compared to palladium. 相似文献
3.
Eun-Yong Ko Eun Duck Park Kyung Won Seo Hyun Chul Lee Doohwan Lee Soonho Kim 《Catalysis Letters》2006,110(3-4):275-279
The preferential CO oxidation (PROX) in the presence of excess hydrogen was studied over Pt–Ni/γ-Al2O3. CO chemisorption, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and temperature-programmed
reduction were conducted to characterize active catalysts. The co-impregnated Pt–Ni/γ-Al2O3 was superior to Pt/Ni/γ-Al2O3 and Ni/Pt/γ-Al2O3 prepared by a sequential impregnation of each component on alumina support. The PROX activity was affected by the reductive
pretreatment condition. The pre-reduction was essential for the low-temperature PROX activity. As the reduction temperature
increased above 423 K, the CO2 selectivity decreased and the atomic percent of Ni in the bimetallic phase of Pt–Ni increased. This catalyst exhibited the
high CO conversion even in the presence of 2% H2O and 20% CO2 over a wide reaction temperature. The bimetallic phase of Pt–Ni seems to give rise to high catalytic activity for the PROX
in H2-rich stream. 相似文献
4.
FTIR and pulse thermal analysis were applied to investigate catalysts containing Pt (1 wt%)/Ba (17 wt%) supported on -Al2O3, SiO2 and ZrO2. The aim was to learn how the support material affects the thermal stability of barium carbonate and its activity in the reaction to bulk Ba(NO3)2. The lower thermal stability of BaCO3 in alumina supported samples was found to influence the formation of barium nitrate during the NO
x
storage process. Quantification of Ba(NO3)2 formed during NO
x
storage indicated that for alumina supported catalysts only ca. 30% of barium present in the sample is involved in the storage process. The low thermal stability found for alumina supported barium nitrite excludes its role in the formation of barium nitrate during interaction of NO
x
with the catalyst at 300 °C. The studies indicate that -Al2O3 plays a major role in influencing the thermal stability of BaCO3 and Ba(NO3)2. This finding seems to be relevant for the higher activity of -Al2O3-supported catalysts in NO
x
storage reduction reactions. 相似文献
5.
Bo-Hyuk Jang Tae-Hun Yeon Hyun-Sik Han Yong-Ki Park Jae-Eui Yie 《Catalysis Letters》2001,77(1-3):21-28
Barium-containing NO
x
storage catalyst showed serious deactivation under thermal exposure at high temperatures. To elucidate the thermal deterioration of the NO
x
storage catalyst, four types of model catalyst, Pt/Al2O3, Ba/Al2O3, Pt–Ba/Al2O3, and a physical mixture of Pt/Al2O3 + Ba/Al2O3 were prepared and their physicochemical properties such as BET, NO TPD, TGA/DSC, XRD, and XPS were evaluated while the thermal aging temperature was increased from 550 to 1050°C. The fresh Pt–Ba/Al2O3 showed a sorption capacity of 3.35 wt%/g-cat. but the aged one revealed a reduced capacity of 2.28 wt%/g-cat. corresponding to 68% of the fresh one. It was found that this reduced sorption capacity was directly related to the deterioration of the NO
x
storage catalyst by thermal aging. The Ba on Ba/Al2O3 and Pt–Ba/Al2O3 catalysts began to interact with alumina to form Ba–Al solid alloy above 600°C and then transformed into stable BaAl2O4 having a spinel structure. However, no phase transition was observed in the Pt/Al2O3 catalyst having no barium component, even after aging at 1050°C. 相似文献
6.
Hydrodesulfurization of dibenzothiophene over supported and unsupported molybdenum carbide catalysts
Hea Kyung Park Du Soung Kim Kyung Lim Kim 《Korean Journal of Chemical Engineering》1998,15(6):625-630
A series of γ-Al2O3 supported molybdenum carbides [carbided Mo/γ-Al2O3 (MCS), Co-Mo/γ-Al2O3 (CMCS), and Ni-Mo/γ-Al2O3 (NMCS)] and unsupported molybdenum carbide (MCUS) were prepared by the temperature-programmed carburization of their corresponding
molybdenum nitrides with 20 % CH4/H2. XRD and SEM studies show that unsupported molybdenum carbide catalyst possesses a typical crystalline Mo2C (FCC structure), while supported molybdenum carbide catalysts possess highly dispersed surface molybdenum carbide species
on an alumina oxide support. The results of dibenzothiophene (DBT) hydrodesulfurization over molybdenum carbide catalysts
show that the reactivity is strongly dependent on the type of catalyst. Supported molybdenum carbide catalysts possess a higher
reactivity than the unsupported molybdenum carbide catalyst. In addition, Co or Ni promoted, supported molybdenum carbide
catalyst possesses a higher reactivity than the unpromoted, supported molybdenum carbide catalyst. The reactivity, which is
also dependent on the reaction conditions, increases with increasing reaction temperature and pressure and contact time. The
CO uptakes of the molybdenum carbide catalysts correlate well with overall activity (total rate) for DBT hydrodesulfurization.
The major reaction product is biphenyl, with cyclohexylbenzene next in abundance regardless of the type of catalysts and reaction
conditions. It was also found that the molybdenum carbide catalysts exhibit stable initial reactivity due to the stable and
weak acidic characteristics of these catalysts. 相似文献
7.
Seung-Soo Kim Jinsoo Kim Hwaung Lee Byung-Ki Na Hyung Keun Song 《Korean Journal of Chemical Engineering》2005,22(4):585-590
Spherical nanostructured γ-Al2O3 granules were prepared by combining the modified Yoldas process and oil-drop method, followed by the Pt impregnation inside
mesopores of the granules by incipient wetness method. Prepared Pt/γ-Al2O3 catalysts were reduced by novel method using plasma, which was named plasma assisted reduction (PAR), and then used for methane
conversion in dielectric-barrier discharge (DBD). The effect of Pt loading, calcination temperature on methane conversion,
and selectivities and yields of products were investigated. Prepared Pt/γ-Al2O3 catalysts were successfully reduced by PAR. The main products of methane conversion were the light alkanes such as C2H6, C3H8 and C4H10 when the catalytic plasma reaction was carried out with Pt/γ-Al2O3 catalyst. Methane conversion was in the range of 38–40% depending on Pt loading and calcination temperature. The highest
yield of C2H6 was 12.7% with 1 wt% Pt/γ-Al2O3 catalysts after calcinations at 500 ‡C. 相似文献
8.
Neetha A. Khan Luis E. Murillo Yuying Shu Jingguang G. Chen 《Catalysis Letters》2005,105(3-4):233-238
The low-temperature self-hydrogenation (disproportionation) of cyclohexene was used as a probe reaction to correlate the reactivity
of Co/Pt(111) bimetallic surfaces with supported Co/Pt/γ-Al2O3 catalysts. Temperature-programmed desorption (TPD) experiments show that cyclohexene undergoes self-hydrogenation on the
~1 ML Co/Pt(111) surface at ~219 K, which does not occur on either pure Pt(111) or a thick Co film on Pt(111). Supported catalysts
with a 1:1 atomic ratio of Co:Pt were synthesized on a high surface area γ-Al2O3 to verify the bimetallic effect on the self-hydrogenation of cyclohexene. EXAFS experiments confirmed the presence of Co–Pt
bonds in the catalyst. Using FTIR in a batch reactor configuration, the bimetallic catalyst showed a higher activity toward
the self-hydrogenation of cyclohexene at room temperature than either Pt/γ-Al2O3 or Co/γ-Al2O3 catalysts. The comparison of Co/Pt(111) and Co/Pt/γ-Al2O3 provided an excellent example of correlating the self-hydrogenation activity of cyclohexene on bimetallic model surfaces
and supported catalysts. 相似文献
9.
Seung-Joon Yoo Jung-Woon Lee Un-Yeon Hwang Hyung-Sang Park Dal-Ryung Park Hee-Dong Jang Ho-Sung Yoon 《Korean Journal of Chemical Engineering》2000,17(4):438-443
γ-AlO(OH) sol solution was prepared by aluminum isopropoxide as an initial material. γ-Al2O3 membrane on the α-Al2O3 support was continuously made through coating and thermal treatment from the α-AlO(OH) sol. Previous work [Yoo et al., 1997]
has shown that the aging stage in the sol preparation process mainly affects the characterization of γ-Al2O3 particles as well as γ-AlO(OH) sol. Based on this fact, the γ-Al2O3 membrane was prepared with two aging conditions in the present study. The separation characteristics experiment of the H2/CO2 mixture was performed on these membranes. As a result of the study, the mechanism of gas transport on the two membranes was
proved as Knudsen diffusion. The ideal separation factor was reached at the value of the calculated Knudsen separation factor;
however, permeability increased and selectivity decreased selectivity according to the aging. 相似文献
10.
Chi-Hwan Han Dae-Ung Hong Jihye Gwak Sang-Do Han 《Korean Journal of Chemical Engineering》2007,24(6):927-931
A planar catlytic combustion gas sensor based on Pd/Pt catalyst supported on F-doped SnO2 nano-crystalline materials has been designed and fabricated for hydrogen detection. The sensor consists of platinum heaters
on an alumina plate coated with a catalytic layer and compensating layer. This sensor exhibited better performance than that
of the sensors employing sensing material of Pd/Pt catalyst on γ-Al2O3 and of Pd/Pt catalyst on nano-crystalline SnO2. The detection limit of the sensor at 370 °C is in the concentration range of 0.5–5% (v/v), with an excellent linearity of
signal voltage to the hydrogen gas concentration. 相似文献
11.
Shinjoh Hirohumi Tanabe Toshitaka Sobukawa Hideo Sugiura Masahiro 《Topics in Catalysis》2001,16(1-4):95-99
The catalytic activity of Pt catalyst loaded on -alumina was improved by Ba addition in simulated automotive exhaust gases. On the other hand, the result of Rh catalyst was the opposite. From the results of the partial reaction orders in C3H6–O2 reaction and TPR, it was concluded that the Ba addition to Pt catalyst suppressed the hydrocarbon chemisorption on the Pt catalyst and therefore allowed the catalytic reaction to proceed smoothly. On the other hand, Ba addition to Rh catalyst caused such a strong oxygen adsorption on Rh that rejected the hydrocarbon adsorption and suppressed the reaction. 相似文献
12.
Zhong-Wen Liu Ki-Won Jun Hyun-Seog Roh Sang-Eon Park Young-Sam Oh 《Korean Journal of Chemical Engineering》2002,19(5):735-741
Partial oxidation of methane (POM) was systematically investigated in a fixed bed reactor over 12 wt% Ni catalysts supported
on α-A12O3, γ-A12O3 and θ-A12O3 which were prepared at different conditions. Results indicate that the catalytic activity toward POM strongly depends on
the BET surface area of the support. All the Ni/ θ-Al2O3 catalysts showed high activity toward POM due to the less formation of inactive NiAl2O4 species, the existence of NiO, species and stable θ-Al2O3 phase. Although Ni/γ-Al2O3 showed the highest activity toward POM, long-time stability cannot be expected as a result of the deterioration of the support
at higher temperature, which is revealed from BET results. From the reaction and characterization results, it is inferred
that the optimal conditions for the preparation of θ-Al2O3 are 1,173 K and 12 h. 相似文献
13.
Pt/γ- Al2O3, Co/γ- Al2O3 and Pt- Co/γ- Al2O3 with different Pt : Co atomic ratios have been prepared with a total metal content of 10 wt% and characterised by hydrogen
chemisorption. The activities of the prereduced catalysts were studied for the reaction of cyclohexanol at 523 K and WHSV
of 4.82 and 7.7 h-1. The Pt-Co/γ-Al2O3 catalyst with 1 : 1 Pt : Co atomic ratio shows typical high metal dispersion and cyclohexanone selectivity.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Hongbin Ma Shufen Li Boyang Wang Ruihong Wang Songjiang Tian 《Journal of the American Oil Chemists' Society》2008,85(3):263-270
The heterogeneous base catalyst, γ-Al2O3 loaded with KOH and K (K/KOH/γ-Al2O3) was first prepared and used in the transesterification of rapeseed oil with methanol to produce biodiesel. The prepared
catalyst was characterized by X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller method, infrared spectroscopy
and X-ray photoelectron spectroscopy. It was found that when γ-Al2O3 is loaded with KOH and K, the Al–O–K species is produced, resulting in an increase in the catalytic activity. The impacts
of catalyst preparation conditions on the catalytic activities of K/KOH/γ-Al2O3 were investigated. The results demonstrate that the catalyst K/KOH/γ-Al2O3 has high catalytic activity when the added amounts of KOH and K are 20 and 7.5 wt% respectively. The transesterification
of rapeseed oil to biodiesel with the prepared heterogeneous base catalyst was optimized. It was found that the yield of biodiesel
can reach as high as 84.52% after 1 h reaction at 60°C, with a 9:1 molar ratio of methanol to oil, a catalyst amount of 4 wt%,
and a stirring rate of 270 g. 相似文献
15.
Toshitaka Tanabe Yasutaka Nagai Kazuhiko Dohmae Nobuyuki Takagi Naoki Takahashi Hirohumi Shinjoh 《Topics in Catalysis》2009,52(10):1433-1439
Operando X-ray absorption fine structure (XAFS) investigations were performed on Pt/γ-Al2O3 during the total oxidation of C3H6 in reducing and oxidizing atmospheres. Study of the Pt valance state and catalytic conversion behavior as a function of temperature
revealed that both the creation of metallic Pt sites and the activation of adsorbed species on Pt are important for the functioning
of the catalytic reaction at low temperature. 相似文献
16.
A Pt/γ-Al2O3 catalyst was tested in simultaneous hydrodesulfurization (HDS) of dibenzothiophene and hydrodearomatization (HDA) of naphthalene reactions. Samples of it were subjected to different pretreatments: reduction, reduction–sulfidation, sulfidation with pure H2S and non-activation. The reduced catalyst presented the best performance, even comparable to that of Co(Ni)Mo catalysts. All catalyst samples were selective to the HDS reaction over HDA, and to the direct desulfurization pathway of dibenzothiophene HDS over the hydrogenation reaction pathway of HDS. The effect of H2S partial pressure on the functionalities of the reduced Pt/γ-Al2O3 catalyst was studied. The results showed that an increase in H2S partial pressure does not cause poisoning, but an inhibition effect, without changing the catalyst selectivity. Accordingly, the activity trends were ascribed to adsorption differences between the different reactive molecules over the same catalytic active site. TPR characterization along with a thermodynamics analysis showed that the active phase of reduced Pt/γ-Al2O3 is constituted by Pt0 particles. However, presulfidation of the catalyst leads to a mixture of PtS and Pt0 which has a negative effect on the catalytic performance without changing catalyst functionalities. 相似文献
17.
Microwave plasma-assisted catalytic reduction of SO2 by CO was studied over four catalysts. The activities of the four catalysts under microwave plasma decreased in the order
of CoO/γ-Al2O3>>SnO2> copper wires > iron wires, which was consistent with the results under conventional heating. By comparing the activity of
CoO/γ-Al2O3 catalyst in the microwave plasma mode with that in the conventional mode, it is demonstrated that the temperature at which
the full SO2 conversion was obtained in the microwave plasma mode was about 200 °C lower than that under the conventional heating mode.
Moreover, an increase of space velocity had little effect on SO2 conversion and sulfur selectivity under microwave plasma; while under conventional heating mode, both SO2 conversion and sulfur selectivity significantly decreased with an increase of space velocity. 相似文献
18.
Jeong Gil Seo Min Hye Youn Sunyoung Park Joohyung Lee Sang Hee Lee Howon Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(1):95-98
An Al2O3-ZrO2 support was prepared by grafting a zirconium precursor onto the surface of commercial γ-Al2O3. A physical mixture of Al2O3-ZrO2 was also prepared for the purpose of comparison. Ni/Al2O3-ZrO2 catalysts were then prepared by an impregnation method, and were applied to the hydrogen production by steam reforming of
liquefied natural gas (LNG). The effect ZrO2 and preparation method of Al2O3-ZrO2 on the performance of supported nickel catalysts in the steam reforming of LNG was investigated. The Al2O3-ZrO2 prepared by a grafting method was more efficient as a support for nickel catalyst than the physical mixture of Al2O3-ZrO2 in the hydrogen production by steam reforming of LNG. The well-developed tetragonal phase of ZrO2 and the high dispersion of ZrO2 on the surface of γ-Al2O3 were responsible for the enhanced catalytic performance of Ni/Al2O3-ZrO2 prepared by way of a grafting method. 相似文献
19.
The activity and selectivity in the catalytic reduction of NO by a mixture of CO and H2 of three PdO-MoO3/-Al2O3 catalysts are compared in the presence of varying amounts of oxygen at reaction temperatures from 100 to 550°C. The catalysts were prepared by different methods and contain about 2% Mo and 2% Pd. Results are compared with those for PdO/-Al2O3, PdO-MoO3/-Al2O3 containing 2% Pd and 20% Mo, and a commercial Pt-Rh catalyst. The PdO-MoO3/-Al2O3 catalysts are more active for the selective reduction of NO to N2 and N2O than PdO/-Al2O3 under slightly oxidizing conditions at temperatures from 300 to 550°C. At these reaction conditions, the fresh PdO-MoO3/-Al2O3 catalysts are comparable with a commercial Pt-Rh catalyst. The improved activity of PdO-MoO3/-Al2O3 relative to PdO/-Al2O3 is believed to be due to the interaction between Pd and Mo. The effect of O2 on the activity and selectivity of these catalysts is different in the reduction of NO by H2, by CO, and by a mixture of H2 and CO. The results using the mixture of reductants cannot be inferred from the results with the single reductants. 相似文献
20.
Characterization of supported Pd-Cu bimetallic catalysts by SEM, EDXS, AES and catalytic selectivity measurements 总被引:2,自引:0,他引:2
Pd-Cu/γ-Al2O3 bimetallic catalysts were prepared according to different impregnation sequences of γ-Al2O3 and characterized by XRD, SEM, EDXS and AES. The catalysts were tested for the selective hydrogenation of aqueous nitrate
solutions to nitrogen. The reaction selectivity was found to be dependent on the catalyst preparation procedures, which affect
the spatial distribution of metallic copper and palladium phases. A catalyst prepared by impregnating γ -Al2O3 with copper followed by palladium gives higher selectivity to nitrogen than a catalyst prepared by impregnating the support
with palladium followed by copper. The AES examination shows that in the catalyst exhibiting a higher nitrogen production
yield, a reaction zone for the liquid-phase nitrate reduction is located in the interior of particles and covered by a layer
of Pd atoms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献