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1.
Ni/Al2O3 aerogel catalysts were synthesized by a sol-gel method combined with a supercritical drying route. The catalytic performances of the catalysts in methane reforming with CO2 were investigated in a quartz micro-reactor. The results indicated that the aerogel catalyst showed higher specific surface area and higher dispersivity of nickel species than those of impregnation catalyst. The excellent catalytic performances and stabilities were achieved over the aerogel catalysts in the fluidized bed reactor. Comprehensive characterization with TG, XRD and FESEM revealed that the aerogel catalyst in the fluidized bed had much lower carbon deposition than that in the fixed bed. The fluidization of the aerogel catalyst greatly improved the contact efficiency of gas-solid phase, which accelerated the gasification of the deposited carbon. In contrast, the deactivation of the aerogel catalyst was caused by the carbon deposition due to the catalyst without moving in the fixed bed. Moreover, decreasing activity of the impregnation catalyst in the fluidized bed resulted from the poor fluidization state of catalyst particles and low effective active sites on surface of catalyst. 相似文献
2.
Sufang He Qiangshan Jing Wanjin Yu Liuye Mo Hui Lou Xiaoming Zheng 《Catalysis Today》2009,148(1-2):130
The reaction of combination of CO2 reforming and partial oxidation of methane to produce syngas (CRPOM) was tested over Ni/SiO2 catalysts which were prepared via incipient-wetness impregnation using precursors of nickel citrate and nickel nitrate. The catalysts were characterized by X-ray powder diffraction analysis (XRD) and H2-temperature-programmed reduction (H2-TPR) techniques. It was shown that the nickel citrate precursor strengthened interaction between NiO and support to form nickel silicate like species which could be reduced to produce small crystallites of metallic nickel at high temperatures. The Ni/SiO2 prepared with the nickel citrate precursor exhibited good catalytic performances for its highly dispersed metallic nickel derived from the nickel silicate species. 相似文献
3.
This work investigates the improvement of Ni/Al2O3 catalyst stability by ZrO2 addition for H2 gas production from CH4/CO2 reforming reactions. The initial effect of Ni addition was followed by the effect of increasing operating temperature to 500–700 °C as well as the effect of ZrO2 loading and the promoted catalyst preparation methods by using a feed gas mixture at a CH4:CO2 ratio of 1:1.25. The experimental results showed that a high reaction temperature of 700 °C was favored by an endothermic dry reforming reaction. In this reaction the deactivation of Ni/Al2O3 was mainly due to coke deposition. This deactivation was evidently inhibited by ZrO2, as it enhances dissociation of CO2 forming oxygen intermediates near the contact between ZrO2 and nickel where the deposited coke is gasified afterwards. The texture of the catalyst or BET surface area was affected by the catalyst preparation method. The change of the catalyst texture resulted from the formation of ZrO2–Al2O3 composite and the plugging of Al2O3 pore by ZrO2. The 15% Ni/10% ZrO2/Al2O3 co-impregnated catalyst showed a higher BET surface area and catalytic activity than the sequentially impregnated catalyst whereas coke inhibition capability of the promoted catalysts prepared by either method was comparable. Further study on long-term catalyst stability should be made. 相似文献
4.
Steven Corthals Joris Van Nederkassel Jan Geboers Hendrik De Winne Jasper Van Noyen Bart Moens Bert Sels Pierre Jacobs 《Catalysis Today》2008,138(1-2):28
Dry reforming of methane was studied over Ni catalysts supported on γAl2O3, CeO2, ZrO2 and MgAl2O4 (670 °C, 1.5 bar, 16–20 l CH4 mlcatalyst−1 h−1). It is shown that MgAl2O4 supported Ni catalysts promoted with both CeO2 and ZrO2 are promising catalysts for dry reforming of methane with carbon dioxide. Within a certain composition range, the simultaneous promotion with CeO2 and ZrO2 has great influence on the amount of coke and the catalyst service time. XRD analyses indicate that formation of crystalline CexZr1−xO2 mixed oxide phases occurs on double promotion. In particular, incorporation of low amounts of Zr in the CeO2 fluorite structure provides stable dry reforming catalysis. As shown with TPR, promotion leads to a higher reduced state of Ni. SEM, XRD and TPR analyses demonstrate that highly dispersed, doubly promoted Ni catalysts with a strong metal-support interaction are essential for stable dry reforming and suppression of the formation of carbon filaments. 相似文献
5.
Nickel catalysts over the CeO2-ZrO2 solid solution were successfully prepared by the co-precipitation method for partial oxidation of methane. The structures of the catalysts were systematically examined by N2 adsorption/desorption, CO chemisorption, X-ray diffraction (XRD) and H2-TPR techniques. The catalytic performance and carbon deposition were investigated for partial oxidation of methane as well. The results showed that the Ni/CeO2-ZrO2 catalysts had a large BET area and fine Ni dispersion. By the co-precipitation method, Ni and CeO2-ZrO2 solid solution had strong interaction confirmed by the H2-TPR analysis. The Ni/CeO2-ZrO2 catalysts showed high activity and stability and the Ni/Ce0.25Zr0.75O2 exhibited the best activity and coking resistance among these catalysts. The catalytic activities and coking resistant behaviors of catalysts were affected by the surface and structural properties of the catalysts. 相似文献
6.
Petar Djinovi?Ilja Gasan Osojnik ?rnivec Jurka BatistaJanez Levec Albin Pintar 《Chemical Engineering and Processing: Process Intensification》2011,50(10):1054-1062
In this work, 3% Ru-Al2O3 and 2% Rh-CeO2 catalysts were synthesized and tested for CH4-CO2 reforming activity using either CO2-rich or CO2-lean model biogas feed. Low carbon deposition was observed on both catalysts, which negligibly influenced catalytic activity. Catalyst deactivation during temperature programmed reaction was observed only with Ru-Al2O3, which was caused by metallic cluster sintering. Both catalysts exhibited good stability during the 70 h exposure to undiluted equimolar CH4/CO2 gas stream at 750 °C. By varying residence time in the reactor during CH4-CO2 reforming, very similar quantities of H2 were consumed for water formation. Reverse water-gas shift (RWGS) reaction occurred to a very similar extent either with low or high WHSV values over both catalysts, revealing that product gas mixture contained near RWGS equilibrium composition, confirming the dominance of WGS reaction and showing that shortening the contact time would actually decrease the H2/CO ratio in the syngas produced by CH4-CO2 reforming, as long as RWGS is quasi equilibrated. H2/CO molar ratio in the produced syngas can be increased either by operating at higher temperatures, or by using a feed stream with CH4/CO2 ratio well above 1. 相似文献
7.
Jorge D.A. Bellido Eurico Y. Tanabe Elisabete M. Assaf 《Applied catalysis. B, Environmental》2009,90(3-4):485-488
Supported nickel catalysts of composition Ni/Y2O3–ZrO2 were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y2O3–ZrO2 in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO2 conversion of 61% on the 5NiYZ catalyst at 800 °C, representing a better response than for the catalyst of the same composition prepared by wet impregnation. 相似文献
8.
Sakae Takenaka 《Fuel》2004,83(1):47-57
Methane decomposition into H2 and carbon nanofibers at 823 K and subsequent gasification of the carbon nanofibers with CO2 into CO at 923 K were performed over supported Ni catalysts (Ni/SiO2, Ni/TiO2 and Ni/Al2O3). Supported Ni catalysts were deactivated for CH4 decomposition with time on stream due to deposition of a large amount of carbon nanofibers. Subsequent contact of CO2 with carbon nanofibers on the deactivated catalysts resulted in the formation of CO with a conversion of the carbons higher than 95%. In addition, gasification with CO2 regenerated the activity of supported Ni catalysts for CH4 decomposition, indicating that H2 formation through CH4 decomposition and CO formation through gasification with CO2 could be carried out repeatedly. Conversions of carbon nanofibers into CO were kept higher than 95% in the repeated gasification over all the catalysts, while change in the catalytic activity for CH4 decomposition with the repeated cycles depended on the kind of catalytic supports. Catalytic activity of Ni/SiO2 for CH4 decomposition was high at early cycles, however, the activity decreased gradually with the repeated cycles. On the other hand, Ni/TiO2 and Ni/Al2O3 showed high activity for CH4 decomposition and the activity was kept high during the repeated cycles. These changes of catalytic activities for CH4 decomposition could be explained by changes in particle sizes of Ni metal, i.e. Ni metal particles in Ni/SiO2 aggregated into ones larger than 150 nm with the repeated cycles, while the particle sizes of Ni metal in Ni/TiO2 and Ni/Al2O3 remained at an effective range for CH4 decomposition (60-100 nm). 相似文献
9.
Sitthiphong Pengpanich Vissanu Meeyoo Thirasak Rirksomboon Johannes Schwank 《Catalysis Today》2008,136(3-4):214
In this study, Ni/Ce0.75Zr0.25O2 catalyst was doped with different amounts of Sn by co-impregnation method. The catalysts were characterized by BET, H2 chemisorption, XRD, TPR, TEM, XPS and tested for iso-octane partial oxidation (iC8POX) to H2 in the temperature range of 400–800 °C at atmospheric pressure. The results showed that most of Sn species were present on the surface of Ni particles and did not modify the reducibility of the support. Addition of a small amount of Sn (<0.5 wt.%) lowered the catalytic activity for iso-octane partial oxidation by less than 5% while the extent of carbon deposition was decreased by more than 50%. However, Sn loadings higher than 1 wt.% caused a massive drop in catalytic activity. This indicates that as long as the Ni surface is only partially covered with Sn species, the active sites for the partial oxidation of iso-octane remain intact, while the surface site ensembles required for carbon formation are blocked. 相似文献
10.
A novel plasma-treated Ni/MgO catalyst was prepared by treating coprecipitated NiCO3–MgCO3 with dielectric-barrier discharge plasma. The results by XRD, TEM and N2 adsorption analyses showed that the plasma-prepared Ni/MgO catalyst possessed smaller particle size, enhanced nickel dispersion, and higher specific surface area than a conventionally reduced Ni/MgO catalyst. The plasma-prepared Ni/MgO catalyst also exhibited better catalytic activity for carbon dioxide reforming of methane. More than 20% higher conversions of methane and carbon dioxide were obtained than those over the conventional Ni/MgO catalyst at 700 °C and a space velocity of 96,000 mL/(h?gcat). 相似文献
11.
Qing Zhang Huifang Wang Guosong Sun Kelin Huang Weiping Fang Yiquan Yang 《Catalysis communications》2009,10(14):1796-1799
Ni/AC catalysts promoted with or without CeO2 for vapor phase carbonylation of ethanol to propionic acid were tested and investigated by CO chemisorption, XRD and H2-TPR techniques. The catalytic test results showed that the proper amount of CeO2 addition could remarkably enhance the activity and stability of Ni/AC catalyst. The characterization results indicated that CeO2 added can improve the dispersion and metal area of Ni on the catalyst, suppress the sintering of Ni crystallite and benefit the reduction of Ni, which are closely related to high performance of the Ni/AC catalyst promoted with CeO2. 相似文献
12.
Mesoporous Ni-CaO-ZrO2 nanocomposites with high thermal stability were designed and employed in the CO2/CH4 reforming. The nanocomposites with appropriate Ni/Ca/Zr molar ratios exhibited excellent activity and prominent coking resistivity. The Ni crystallites were effectively controlled under the critical size for coke formation in such nanocomposites. It was found that low Ni content resulted in high metal dispersion and good catalytic performance. Moreover, the basicity of the matrices improved the chemisorption of CO2 and promoted the gasification of deposited coke on the catalyst. 相似文献
13.
Ebrahim Salehi Fakhry Seyedeyn Azad Thomas Harding Jalal Abedi 《Fuel Processing Technology》2011,92(12):2203-2210
Catalytic steam reforming of bio-oil was investigated in a fixed bed tubular reactor for production of hydrogen. Two series of nickel/alumina (Ni/Al2O3) supported catalysts promoted with ruthenium (Ru) and magnesium (Mg) were prepared. Each catalyst of the first series (Ru–Ni/Al2O3) was prepared by co-impregnation of nickel and ruthenium on alumina. They were examined to investigate the effect of adding ruthenium on the performance of the catalysts for hydrogen production. The effect of the temperature, the most effective parameter in the steam reforming of bio-oil, on the activity of the catalysts was also investigated. Each catalyst of the second series (Ni–MgO/Al2O3) was prepared by consecutive impregnation using various preparation procedures. They were tested to determine the effect of adding magnesium as well as the effect of the preparation procedure on the outlet gas concentrations. It was shown that in both series, the catalysts were more efficient in hydrogen production as well as carbon conversion than Ni/Al2O3 catalysts. The highest hydrogen yield was 85% which was achieved over Ru–Ni/Al2O3 at 950 °C. It was also found that the effect of adding a small amount of ruthenium was superior to that of nickel on the yield of hydrogen when the nickel content was equal to or greater than 10.7%. 相似文献
14.
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
15.
Katsutoshi Nagaoka Kulathuiyer Seshan Kazuhiro Takanabe Ken-ichi Aika 《Catalysis Letters》2005,99(1-2):97-100
CH4/CO2 reforming over Pt/ZrO2, Pt/CeO2 and Pt/ZrO2 with CeO2 was investigated at 2 MPa. Pt/ZrO2, which shows stable activity under 0.1 MPa, and Pt/CeO2 showed gradual deactivation with time at the high pressure. The deactivation was suppressed drastically on Pt/ZrO2 with CeO2 prepared by different impregnation order (co-impregnation of Pt and CeO2 on ZrO2, and consecutive impregnation of Pt and CeO2 on ZrO2). The amount of coke deposition was found insignificant and similar among all the catalysts (including Pt/ZrO2 and Pt/CeO2). Catalytic activity after the reaction for 24 h was in agreement with Pt particle size after the reaction for same period, indicating that the difference of the catalytic stability is mainly dependent on the extent of Pt aggregation through catalyst preparation, H2 reduction, and the CH4/CO2 reforming. Pt aggregation and the amount of coke deposition were least pronounced on (Pt–Ce)/ZrO2 prepared by impregnation of CeO2 on Pt/ZrO2 and the catalyst showed highest stability. 相似文献
16.
The steam reforming of liquefied petroleum gas (LPG) over Ni- and Rh-based catalysts supported on Gd-CeO2 (CGO) and Al2O3 was studied at 750-900 °C. The order of activity was found to be Rh/CGO > Ni/CGO ∼ Rh/Al2O3 > Ni/Al2O3; we indicated that the comparable activity of Ni/CGO to precious metal Rh/Al2O3 is due to the occurring of gas-solid reactions between hydrocarbons and lattice oxygen () on CGO surface along with the reaction taking place on the active site of Ni, which helps preventing the carbon deposition and promoting the steam reforming of LPG.The effects of O2 (as oxidative steam reforming) and H2 adding were further studied over Ni/CGO and Ni/Al2O3. It was found that the additional of these compounds significantly reduced the amount of carbon deposition and promoted the conversion of hydrocarbons (i.e., LPG as well as CH4, C2H4 and C2H6 occurred from the thermal decomposition of LPG) to CO and H2. Nevertheless, the addition of too high O2 oppositely decreased H2 yield due to the oxidizing of Ni particle and the possible combusting of H2 generated from the reaction, while the addition of too high H2 also negatively affect the catalyst activity due to the occurring of catalyst active site competition and the inhibition of gas-solid reactions between the gaseous hydrocarbon compounds and on the surface of CGO (for the case of Ni/CGO). 相似文献
17.
Silicon carbide supported nickel catalysts for CO methanation were prepared by impregnation method. The activity of the catalysts was tested in a fixed-bed reactor with a stream of H2/CO = 3 without diluent gas. The results show that 15 wt.% Ni/SiC catalyst calcined at 550 °C exhibits excellent catalytic activity. As compared with 15 wt.% Ni/TiO2 catalyst, the Ni/SiC catalyst shows higher activity and stability in the methanation reaction. The characterization results from X-ray diffraction and transmission electron microscopy suggest that no obvious catalyst sintering has occurred in the Ni/SiC catalyst due to the excellent thermal stability and high heat conductivity of SiC. 相似文献
18.
Toshihiko Osaki Tatsuro Horiuchi Toyohiko Sugiyama Kenzi Suzuki Toshiaki Mori 《Catalysis Letters》1998,52(3-4):171-180
Uniform and monolithic NiO–Al2O3 aerogels were prepared from cyclic nickel glycoxide, (CH2O)2Ni, and boehmite sol, AlOOH, and the catalyst performance of the aerogels for the CO2-reforming of methane was investigated. The NiO–Al2O3 aerogels showed higher activity than impregnation NiO/Al2O3 catalysts, while the aerogels exhibited much less activity for coking than the impregnation catalysts. Less deactivation
was also observed on the aerogel catalysts than on the impregnation catalysts in the continuous-flow reaction. The Ni was
uniformly incorporated throughout alumina where both the metal and the support exist in the aerogel form, i.e., Ni–O–Al bond
was considered to be formed in the aerogels. As a result, fine Ni particles appeared after H2 reduction throughout the alumina support with high dispersion, which brought about not only higher activity but also much
less activity for coking on the aerogels. Retardation of catalyst deactivation was ascribed to the suppression of both coking
and sintering of Ni particles on the aerogels.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
All silicious MCM-41 was investigated as a support or a support precursor for Pd/SiO2 and prepared catalysts were tested for methanol synthesis from CO and H2. The methods of Pd loading on the MCM-41 were impregnation, seed impregnation and chemical vapor deposition (CVD). For both impregnations, most Pd existed outside of the pore as large particles, and only a small part of Pd was inserted into the pore of MCM-41 retaining the initial structure. On the contrary, in the catalyst prepared by CVD method, the MCM-41 structure was completely destroyed to become amorphous SiO2. Yet the average Pd particle size in this catalyst was smaller and its distribution was narrower than those of the catalysts prepared by impregnation methods. In the methanol synthesis from CO hydrogenation the catalyst prepared by CVD showed higher methanol selectivity than other MCM-41-derived catalysts. This result was considered to be due to the more uniform distribution of the Pd particle size. 相似文献
20.
Chunshan Li Daisuke Hirabayashi Kenzi Suzuki 《Applied catalysis. B, Environmental》2009,88(3-4):351-360
Newly synthesized nickel calcium aluminum catalysts (Ni/Ca12Al14O33) were tested in a fixed bed reactor for biomass tar steam reforming, toluene as tar destruction model compound. Four catalysts (Ni/Ca12Al14O33) were prepared with Ni loading amount from 1, 3, 5 to 7 wt%, even 1% loading catalyst also showed excellent performance. Catalysts aged experiments in the absence (60 h on stream) and presence of H2S were characterized by BET, X-ray diffraction (XRD), and Raman spectra. It was observed that Ni/Ca12Al14O33 showed excellent sustainability against coke formation due to the “free oxygen” in the catalysts. It also exhibited higher H2S-poisoning resistance property compared to the commercial catalysts Ni/Al2O3 (5%) and Ni/CaO0.5/MgO0.5. Raman spectra revealed that “free oxygen O2− and O22−” in the structure of the catalysts could be substituted by sulfur then protected Ni poisoning on some degree, but reactivation experiments by O2 flowing showed that the sulfide Ni/Ca12Al14O33 was difficult to completely restore, incorporation of sulfur in the structure only partly regain by O2. The kinetic model proposes, as generally accepted, a first-order reaction for toluene with activation energy of 82.06 kJ mol−1 was coincident with the literature data. The Ni/Ca12Al14O33 catalyst was effective and relative cheap, which may be lead to reduction in the cost of hot gas cleaning process. 相似文献