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101.
A novel metal monolith reactor for coupling methane steam reforming with catalytic combustion is proposed in this work, the metal monolith is used as a co-current heat exchanger and the catalysts are deposited on channel walls of the monolith. The transport and reaction performances of the reactor are numerically studied utilizing heterogeneous model based on the whole reactor. The influence of the operating conditions like feed gas velocity, temperature and composition are predicted to be significant and they must be carefully adjusted in order to avoid hot spots or insufficient methane conversion. To improve reactor performance, several different channel arrangements and catalyst distribution modes in the monolith are designed and simulated. It is demonstrated that reasonable reactor configuration, structure parameters and catalyst distribution can considerably enhance heat transfer and increase the methane conversion, resulting in a compact and intensified unit. 相似文献
102.
Dimitris K. Liguras Dimitris I. Kondarides Xenophon E. Verykios 《Applied catalysis. B, Environmental》2003,43(4):345-354
The catalytic performance of supported noble metal catalysts for the steam reforming (SR) of ethanol has been investigated in the temperature range of 600–850 °C with respect to the nature of the active metallic phase (Rh, Ru, Pt, Pd), the nature of the support (Al2O3, MgO, TiO2) and the metal loading (0–5 wt.%). It is found that for low-loaded catalysts, Rh is significantly more active and selective toward hydrogen formation compared to Ru, Pt and Pd, which show a similar behavior. The catalytic performance of Rh and, particularly, Ru is significantly improved with increasing metal loading, leading to higher ethanol conversions and hydrogen selectivities at given reaction temperatures. The catalytic activity and selectivity of high-loaded Ru catalysts is comparable to that of Rh and, therefore, ruthenium was further investigated as a less costly alternative. It was found that, under certain reaction conditions, the 5% Ru/Al2O3 catalyst is able to completely convert ethanol with selectivities toward hydrogen above 95%, the only byproduct being methane. Long-term tests conducted under severe conditions showed that the catalyst is acceptably stable and could be a good candidate for the production of hydrogen by steam reforming of ethanol for fuel cell applications. 相似文献
103.
An efficient and compact catalytic membrane reactor for reforming of CH4 was developed by integrating a hydrogen perm-selective silica membrane with an Rh/-Al2O3 catalyst layer. The catalytic layer was sandwiched between the outer surface of the -Al2O3 support tube and the silica membrane with an aim of improving the heat and mass transfer rates through the system and to simplify the reactor geometry. The system showed improved efficiency for reforming of CH4 at comparatively lower operating temperatures and steam to C molar ratios than the conventional fixed-bed steam reforming systems. Under optimized conditions, a nearly 25-30% improvement from the equilibrium conversion level was achieved as a result of abstraction of hydrogen from the product stream by the silica membrane integrated with the catalyst layer. The performance of the system was evaluated as a function of various process parameters. Because of the compactness and efficiency, the present system emerges as a promising alternative to the conventional membrane reactors, which possess separate catalytic and membrane units. 相似文献
104.
Steam methane reforming with oxygen input is simulated in staged‐separation membrane reactors. The configuration retains the advantage of regular membrane reactors for achieving super‐equilibrium conversion, but reaction and membrane separation are carried out in two separate units. Equilibrium is assumed in the models given the excess of catalyst. The optimal pure hydrogen yield is obtained with 55% of the total membrane area allocated to the first of two modules. The performance of the process with pure oxygen input is only marginally better than with air. Oxygen must be added in split mode to reach autothermal operation for both reformer modules, and the oxygen input to each module depends on the process conditions. The effects of temperature, steam‐to‐carbon ratio and pressure of the reformer and the area of the membrane modules are investigated for various conditions. Compared with a traditional reformer with an ex situ membrane purifier downstream, the staged reactor is capable of much better pure hydrogen yield for the same autothermal reforming operating conditions. 相似文献
105.
Nano‐engineered nickel catalysts supported on 4‐channel α‐Al2O3 hollow fibers for dry reforming of methane 下载免费PDF全文
Zeyu Shang Shiguang Li Qingfa Wang Xuehong Gu Xinhua Liang 《American Institute of Chemical Engineers》2018,64(7):2625-2631
A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al2O3 hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh?1gNi?1 at 800°C. NiAl2O4 spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al2O3 ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al2O3 ALD films. Among the Al2O3 ALD coated catalysts, the catalyst with five cycles of Al2O3 ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018 相似文献
106.
Ce0.75Zr0.25O2 solid solutions doped with Y3+ or Pr4+/Pr3+ were prepared by the co-precipitation method, and their physicochemical properties were characterized by means of N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, FT-Raman, and H2 temperature-programmed reduction and thermogravimetric analysis. Their performance in CH4–CO2 reforming was also tested in an atmospheric fixed-bed reactor. Ce0.75Zr0.25O2 and Y3+ or Pr4+/Pr3+ doped Ce0.75Zr0.25O2 solid solutions are of CaF2 structure, and the thermal stability of Ce0.75Zr0.25O2 is enhanced by doping Y3+ or Pr4+/Pr3+. Comparing with Ce0.75Zr0.25O2, the migration of bulk lattice oxygen species become easier and the content of surface oxygen species is higher in the doped Ce0.75Zr0.25O2, which is due to either oxygen vacancies or/and structural distortion resulted from the doping. The activity of the solid solutions in CH4–CO2 reforming is closely related to the surface oxygen species. Y3+ or Pr4+/Pr3+ doped Ce0.75Zr0.25O2, especially the former, show higher activity than Ce0.75Zr0.25O2, and Y3+ doped Ce0.75Zr0.25O2 possesses better stability. All of the catalysts have good coke resistance. The catalyst deactivation is mainly due to the catalyst sintering. 相似文献
107.
Hydrogen production was prepared via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system. Low-cost catalyst dolomite was chosen for the primary steam reforming of bio-oil in consideration of the unavoidable deactivation caused by direct contact of metal catalyst and bio-oil itself. Nickel-based catalyst Ni/MgO was used in the second stage to increase the purity and the yield of desirable gas product further. Influential parameters such as temperature, steam to carbon ratio (S/C, S/CH4), and material space velocity (WBHSV, GHSV) both for the first and the second reaction stages on gas product yield, carbon selectivity of gas product, CH4 conversion as well as purity of desirable gas product were investigated. High temperature (> 850 °C) and high S/C (> 12) are necessary for efficient conversion of bio-oil to desirable gas product in the first steam reforming stage. Low WBHSV favors the increase of any gas product yield at any selected temperature and the overall conversion of bio-oil to gas product increases accordingly. Nickel-based catalyst Ni/MgO is effective in purification stage and 100% conversion of CH4 can be obtained under the conditions of S/CH4 no less than 2 and temperature no less than 800 °C. Low GHSV favors the CH4 conversion and the maximum CH4 conversion 100%, desirable gas product purity 100%, and potential hydrogen yield 81.1% can be obtained at 800 °C provided that GHSV is no more than 3600 h− 1. Carbon deposition behaviors in one-stage reactor prove that the steam reforming of crude bio-oil in a two-stage fixed bed reaction system is necessary and significant. 相似文献
108.
Dae Hyun Kim Jung Shik Kang Yun Joo Lee Nam Kuk Park Young Chul Kim Suk In Hong Dong Ju Moon 《Catalysis Today》2008,136(3-4):228
Steam reforming of n-hexadecane, a main constituent of diesel, over noble metal-modified Ni-based hydrotalcite catalyst was carried out in a temperature range of 700–950 °C, at an atmospheric pressure with space velocity of 10,000–100,000 h−1 and feed molar ratio of H2O/C = 3.0. The catalysts were prepared by a co-precipitation and dipping methods. The noble metal-modified Ni-based hydrotalcite catalyst displayed higher resistance for the sintering of active metal than the Ni-based hydrotalcite catalyst prepared by the conventional method. It was found that the Rh-modified Ni-based catalysts showed high resistance to the formation of carbon compared to Ni-based catalysts. The results suggest that Rh-modified Ni-based catalyst can be applied for the steam reforming (SR) reaction of diesel. 相似文献
109.
Xin-Rong Zhang Lu-Cum Wang Cheng-Zhang Yao Yong Cao Wei-Lin Dai He-Yong He Kang-Nian Fan 《Catalysis Letters》2005,102(3-4):183-190
The impact of preparation methods on the structure and catalytic behavior of Cu/ZnO/Al2O3 catalysts for H2 production from steam reforming of methanol (SRM) has been reported. The results show that the nanostructured Cu/ZnO/Al2O3 catalyst obtained by a novel gel-coprecipitation of oxalate precursors has a high specific surface area and high component dispersion, exhibiting much higher activity in the SRM reaction as compared to the catalysts prepared by conventional coprecipitation techniques. It is suggested that the superior catalytic performance of the oxalate gel-coprecipitation-derived Cu/ZnO/Al2O3 catalyst could be attributed to the generation of “catalytically active” copper material with a much higher metallic copper specific surface as well as a stronger Cu–Zn interaction due to an easier incorporation of zinc species into CuC2O4 · x H2O precursors as a consequence of isomorphous substitution between copper and zinc in the oxalate gel-precursors. 相似文献
110.
This paper deals with an experimental investigation concerning steam reforming of methanol at 280, 340 and 380 °C over NiAl
and Ni (Au, Rh or Ir)Al layered double hydroxides (LDHs) derived catalysts. Incorporation of noble metal ions into the NiAl-LDH
framework was evidenced by XRD, TGA and TEM techniques. High selectivity to H2 and CO2 with less than 5% (volume) CO and trace CH4 was observed over the NiAl-LDH catalyst. Whereas CO and H2 are major products at lower temperatures after addition of Au, Rh and Ir to the NiAl-LDH system. They are significantly reduced
with the concomitant increase in CH4 and CO2 as the temperature increased. 相似文献