共查询到20条相似文献,搜索用时 15 毫秒
1.
Micro-channel reactor for steam reforming of methanol seems to be attractive for portable application as one part of fuel processor in fuel cell. In the present study, steam reforming of methanol was performed in one stainless steel micro-channel reactor coated with commercial catalyst. The different sols (alumina, zirconia and mixed sol of alumina and zirconia) as a binder for the catalyst were applied to compare the stability and performance. Among the different sols, mixed sol of alumina and zirconia comparatively produced better stability and performance. 相似文献
2.
This paper focuses on an experimental study of the methanol steam reforming (MSR) reaction. A dense Pd/Ag membrane reactor (MR) has been used, and its behaviour has been compared to the performance of a traditional reactor (TR) packed with the same catalyst type and amount. The parameters investigated are reaction time, temperature, feed ratio and sweep gas flow rate. The few papers dealing with MR applications for the MSR reaction mainly analyse the effect of temperature and pressure on the reaction system. The investigation of new parameters permitted to better understand how the fluid-dynamics of the MR influences the hydrogen separation effect on methanol conversion and product selectivity. The comparison between MR and TR in terms of methanol conversion shows that the MR gives a higher performance than the TR at each operating condition investigated. Concerning hydrogen production, the experiments have shown that the overall selectivity towards hydrogen is identical for both MR and TR. However, the MR produces a free-CO hydrogen stream, which could be useful for direct application in proton exchange membrane fuel cells. A comparison, in terms of methanol conversion versus temperature, with literature data is also included. 相似文献
3.
Tetsuya Fukunaga Naonori Ryumon Nobuyuki Ichikuni Shogo Shimazu 《Catalysis communications》2009,10(14):1800-1803
CuMn-spinel oxide (CuMn(S)) and non-spinel CuMn (CuMn(NS)) oxide have been obtained by calcining the same precursor at 900 °C and 300 °C, respectively. CuMn(S) was composed of Cu1.5Mn1.5O4 spinel and Mn3O4, while CuMn(NS) consisted of CuO and Mn3O4. XRD, EXAFS, and TEM measurements of the samples reduced in hydrogen revealed that both CuMn(S) and CuMn(NS) were reduced to Cu metal dispersed on MnO and that the particle size of Cu metal from the CuMn(S) was smaller than that from CuMn(NS). In methanol steam reforming, the spinel derived catalyst showed higher activity than the non-spinel due to the higher dispersion of the Cu metal. 相似文献
4.
The aim of this work is to study from an experimental point of view the oxidative steam reforming of methanol by investigating the behaviour of a dense Pd/Ag membrane reactor (MR) in terms of methanol conversion as well as hydrogen production. The main parameters considered are the operating temperature and the O2/CH3OH feed ratio. This is a pioneer work in the application of MR to this kind of reaction, whose goal should be to produce a CO-free hydrogen stream suitable for hydrogen fuel cell applications. The experimental results show that the MR gives methanol conversions higher than traditional reactors (TRs) at each temperature investigated, confirming the good potential of the membrane reactor device for this interesting reaction system. 相似文献
5.
Joan Papavasiliou George Avgouropoulos Theophilos Ioannides 《Applied catalysis. B, Environmental》2007,69(3-4):226-234
Steam reforming of methanol was carried out over a series of doped CuO–CeO2 catalysts prepared via the urea–nitrate combustion method. XRD analysis showed that at least part of the dopant cations enter the ceria lattice. The addition of various metal oxide dopants in the catalyst composition affected in a different way the catalytic performance towards H2 production. Small amounts of oxides of Sm and Zn improved the performance of CuO–CeO2, while further addition of these oxides caused a decrease in catalyst activity. XPS analysis of Zn- and Sm-doped catalysts showed that increase of dopant loading leads to surface segregation of the dopant and decrease of copper oxide dispersion. The addition of oxides of La, Zr, Mg, Gd, Y or Ca lowered or had no effect on catalytic activity, but led to less CO in the reaction products. Noble-metal modified catalysts had slightly higher activity, but the CO selectivity was also significantly higher. 相似文献
6.
A. Basile A. Parmaliana S. Tosti A. Iulianelli F. Gallucci C. Espro J. Spooren 《Catalysis Today》2008,137(1):17
The methanol steam reforming (MSR) reaction was studied by using both a dense Pd-Ag membrane reactor (MR) and a fixed bed reactor (FBR). Both the FBR and the MR were packed with a new catalyst based on CuOAl2O3ZnOMgO, having an upper temperature limit of around 350 °C. A constant sweep gas flow rate in counter-current mode was used in MR and the experiments were carried out by varying the water/methanol feed molar ratio in the range 3/1–9/1 and the reaction temperature in the range 250–300 °C. The catalyst shows high activity and selectivity towards the CO2 and the H2 formation in the temperature range investigated. Under the same operative conditions, the MR shows higher conversions than FBR and, in particular, at 300 °C and H2O/CH3OH molar ratio higher than 5/1 the MR shows complete methanol conversion. 相似文献
7.
Jingsheng Jia Jin Zhou Chunxi Zhang Zhongshan Yuan Shujuan Wang Lei Cao Shudong Wang 《Applied Catalysis A: General》2008,341(1-2):1-7
Ir-based catalysts on heat-resisting foil supports with different washcoats were investigated for hydrogen production by high-temperature steam reforming of methanol. Al2O3, Ce0.8Zr0.2O2–Al2O3, Ce0.8Zr0.2O2/Al2O3 and Ce0.8Zr0.2O2 coatings were prepared on the metallic supports and iridium was deposited on them as the active component. The samples were characterized by X-ray powder diffraction (XRD), ultrasonic vibration test, scanning electron microscope (SEM) and temperature-programmed reduction (TPR). The performance of the catalysts for steam reforming of methanol was evaluated with a fixed-bed reactor. It was found that the phase structure, the shape of the surface particles and the coating adherence were different from each other for the four kinds of coatings. The activities, selectivities and stabilities of these Ir-based catalysts on metallic supports were compared to select the optimal one for use in high-temperature methanol steam reforming. The results indicated that the Ir/Ce0.8Zr0.2O2/Al2O3/FeCrAl catalyst showed better performance than the other catalysts, which is a promising candidate for hydrogen production via the methanol steam reforming process in Pd membrane reactors. 相似文献
8.
Balamurali Krishna R. Nair 《Chemical engineering science》2006,61(19):6616-6636
Performance analyses are carried out for the palladium membrane fuel processor for catalytic generation of high purity hydrogen. The reactor model includes detailed particle-scale multi-component diffusion, multiple reversible reactions, flow, and membrane transport. Using methanol steam reforming on Cu/ZnO/Al2O3 catalyst as the test reaction, a systematic examination of the effects of operating and reactor design parameters on key performance metrics is presented. Single particle simulations reveal a complex interplay between nonisobaric transport and the reversible reactions (methanol reforming and decomposition, and water-gas shift), which impact overall reactor performance. An analysis of characteristic times helps to identify four different productivity controlling regimes: (i) permeation control, encountered with thick membranes and/or insufficient membrane area; (ii) catalyst pore diffusion control encountered with diffusion of reacting species in larger particles; (iii) reaction control, encountered when intrinsic catalytic rates are too low because of inadequate activity or catalyst loading; and (iv) feed control, encountered when the limiting reactant feed rate is inadequate. The simulations reveal that a maximum in the hydrogen productivity occurs at an intermediate space velocity, while the hydrogen utilization is a decreasing function of space velocity, implying a trade-off between productivity and hydrogen utilization. The locus of productivity maxima itself exhibits a maximum at an intermediate membrane surface to volume ratio, the specific value of which is dependent on the particle size, membrane thickness and reaction conditions. At moderate temperature and total pressure (, 10 bar), particles smaller than 2 mm diameter, Pd membranes with thickness less than , and membrane surface to volume ratio exceeding are needed to achieve viable productivity . A comparison between the packed-bed membrane reactor and conventional packed-bed reactor indicates a modest improvement in the conversion and productivity due to in situ hydrogen removal. 相似文献
9.
Hyung Chul Yoon Jonathan Otero Paul A. Erickson 《Applied catalysis. B, Environmental》2007,75(3-4):264-271
In this paper the limiting mechanisms in the methanol-steam reformation process are analyzed theoretically and compared experimentally as to determine each contribution and limitation to the overall process. Experimental data from steam reformers are presented and analyzed. Models of each mechanism are provided to quantify theoretical times necessary for each process to occur. While the models in this paper are not precise representations of all steam reforming processes, the models do provide enough evidence to conclude that heat transfer is the dominant limiting mechanism in methanol-steam reformation. Further studies quantifying the experimental effects of heat transfer should be pursued with the ultimate goal of properly sizing steam reformers. 相似文献
10.
Steam reforming of methane, kerosene and heavy oil over a nickel/alumina commercial catalyst and other materials such as limestone,
dolomite and iron ore, was studied using a 5 cm i.d. fluidized bed reactor. The effects of operating parameters on conversion,
hydrogen yield, product gas composition and elutriation of fine catalysts were investigated. It was found that a fluidized
bed is flexible enough to handle various feedstocks, including hydrocarbons heavier than naphtha, because it permits the addition
of catalyst to, or withdrawals of, coked catalyst from the bed. The yield of hydrogen obtained from fluidized bed steam reforming
of heavy oil at 800‡C over limestone was similar to that obtained over commercial nickel-based catalyst. This indicates that
limestone could be a promising catalyst for the production of hydrogen from heavy oil. However, hydrogen yield decreased with
reaction time in the experiments using the limestone catalyst. The main cause of the decrease in hydrogen yield was elutriation
of fine catalysts from the bed during the reaction. 相似文献
11.
Methane steam reforming in a Pd-Ru membrane reactor 总被引:2,自引:0,他引:2
Suk Woo Nam Sung Pil Yoon Heung Yong Ha Seong-Ahn Hong Anatoly P. Maganyuk 《Korean Journal of Chemical Engineering》2000,17(3):288-291
Methane steam reforming has been carried out in a Pd-Ru membrane reactor at 500–600 ‡C. The membrane reactor consisted of
a Pd-6%Ru tube of 100 mm wall thickness and commercial catalysts packed outside of the membrane. The methane conversion was
significantly enhanced in the membrane reactor in which reaction equilibrium was shifted by selective permeation of hydrogen
through the membrane. The methane conversion at 500 ‡C was improved as high as 80% in the membrane reactor, while equilibrium
conversion in a fixed-bed reactor was 57%. The effect of gas flow rate and temperature on the performance of the membrane
reactor was investigated and the results were compared with the simulated result from the model. The model prediction is in
good agreement with the experimental result. In order to apply the membrane in practice, however, the thickness of the membrane
has to be reduced. Therefore, the effect of membrane thickness on performance of the membrane reactor was estimated using
the model. 相似文献
12.
Katsuki Kusakabe Shigeharu Morooka Hideaki Maeda 《Korean Journal of Chemical Engineering》2001,18(3):271-276
The purpose of this article is to demonstrate the applicability of microreactors for use in catalytic reactions at elevated
temperatures. Microchannels were fabricated on both sides of a silicon wafer by wet chemical etching after pattern transfer
using a negative photoresist. The walls of the reactor channel were coated with a platinum layer, for use as a sample catalyst,
by sputtering. A heating element was installed in the channel on the opposite surface of the reactor channel. The reactor
channel was sealed gas-tight with a glass plate by using an anodic bonding technique. A small-scale palladium membrane was
also prepared on the surface of a 50-Μm thick copper film. In the membrane preparation, a negative photoresist was spin-coated
and solidified to serve as a protective film. A palladium layer was then electrodeposited on the other uncovered surface.
After the protective film was removed, the resist was again spin-coated on the copper surface, and a pattern of microslits
was transferred by photolithography. After development, the microslits were electrolitically etched away, resulting in the
formation of a palladium membrane as an assemblage of thin layers formed in the microslits. The integration of the microreactor
and the membrane is currently under way. 相似文献
13.
A miniaturized methanol steam reformer with a serpentine type of micro-channels was developed based on poly-dimethylsiloxane (PDMS) material. This way of fabricating micro-hydrogen generator is very simple and inexpensive. The volume of a PDMS micro-reformer is less than 10 cm3. The catalyst used was a commercial Cu/ZnO/Al2O3 reforming catalyst from Johnson Matthey. The Cu/ZnO/Al2O3 reforming catalyst particles of mean diameter 50-70 μm was packed into the micro-channels by injecting water based suspension of catalyst particles at the inlet point. The miniaturized PDMS micro-reformer was operated successfully in the operating temperatures of 180-240 °C and 15%-75% molar methanol conversion was achieved in this temperature range for WHSV of 2.1-4.2 h−1. It was not possible to operate the micro-reformer made by pure PDMS at temperature beyond 240 °C. Hybrid type of micro-reformer was fabricated by mixing PDMS and silica powder which allowed the operating temperature around 300 °C. The complete conversion (99.5%) of methanol was achieved at 280 °C in this case. The maximum reformate gas flow rate was 30 ml/min which can produce 1 W power at 0.6 V assuming hydrogen utilization of 60%. 相似文献
14.
《Ceramics International》2017,43(8):6201-6213
In this study a series of CuO-ZnO-Al2O3-ZrO2 nanocatalysts were prepared using hydrothermal, thermochemical, coprecipitation and hybrid coprecipitation-plasma methods. The impacts of argon glow discharge plasma on physicochemical properties and performance of nanocatalysts in methanol steam reforming for H2 production were investigated. The samples were characterized using XRD, FESEM, EDX, BET and FTIR techniques. According to XRD patterns, the peaks intensity of the plasma-treated sample were decreased and a little widened, possibly due to smaller particle size and better particle dispersion. The FESEM images showed no evident agglomeration on the surface of plasma-treated sample and good dispersion of this sample was noticed in EDX results. Besides, according to BET analysis, this nanocatalyst had higher specific surface area than other samples. Smaller particle size, more uniform distribution of particles and higher surface area, resulting from the glow discharge plasma treatment, caused higher hydrogen yield and methanol conversion at all temperatures. Consequently, methanol conversion for plasma-treated sample reached 100% at 240 °C and the performance of this sample remained constant for a duration of 24 h. 相似文献
15.
The effect of noble metal addition on the catalytic properties of Co/Al2O3 was evaluated for the steam reforming of methane. Co/Al2O3 catalysts were prepared with addition of different noble metals (Pt, Pd, Ru and Ir 0.3 wt.%) by a wetness impregnation method and characterized by UV–vis spectroscopy, temperature programmed reduction (TPR) and temperature programmed oxidation (TPO) of the reduced catalysts. The UV–vis spectra of the samples indicate that, most likely, large amounts of the supported cobalt form Co species in which cobalt is in octahedral and tetrahedral symmetries. No peaks assigned to cobalt species from aluminate were found for the promoted and unpromoted cobalt catalysts. TPO analyses showed that the addition of the noble metals on the Co/Al2O3 catalyst leads to a more stable metallic state and less susceptible to the deactivation process during the reforming reaction. The Co/Al2O3 promoted with Pt showed higher stability and selectivity for H2production during the methane steam reforming. 相似文献
16.
This paper presents an investigation into the complex interactions between catalytic combustion and CH4 steam reforming in a co-flow heat exchanger where the surface combustion drives the endothermic steam reforming on opposite sides of separating plates in alternating channel flows. To this end, a simplified transient model was established to assess the stability of a system combining H2 or CH4 combustion over a supported Pd catalyst and CH4 steam reforming over a supported Rh catalyst. The model uses previously reported detailed surface chemistry mechanisms, and results compared favorably with experiments using a flat-plate reactor with simultaneous H2 combustion over a γ-Al2O3-supported Pd catalyst and CH4 steam reforming over a γ-Al2O3-supported Rh catalyst. Results indicate that stable reactor operation is achievable at relatively low inlet temperatures (400 °C) with H2 combustion. Model results for a reactor with CH4 combustion indicated that stable reactor operation with reforming fuel conversion to H2 requires higher inlet temperatures. The results indicate that slow transient decay of conversion, on the order of minutes, can arise due to loss of combustion activity from high-temperature reduction of the Pd catalyst near the reactor entrance. However, model results also show that under preferred conditions, the endothermic reforming can be sustained with adequate conversion to maintain combustion catalyst temperatures within the range where activity is high. A parametric study of combustion inlet stoichiometry, temperature, and velocity reveals that higher combustion fuel/air ratios are preferred with lower inlet temperatures (≤500 °C) while lower fuel/air ratios are necessary at higher inlet temperatures (600 °C). 相似文献
17.
针对甲醇蒸汽的微通道重整催化反应过程,建立了三维稳态多组分传输反应模型;利用数值模拟分析,分别研究了平行阵列微通道和仿蜂巢分叉微通道在Zn_Cr/CeO2/ZrO2催化剂下的反应情况。通过双速率模型考察这两种流道中操作条件对甲醇蒸汽重整制氢输运规律的影响,发现这两种微通道反应器均可促进甲醇转化率和氢气产率的提高。与常规平行微通道的比较发现,仿蜂巢分叉微通道内反应气流动所需的泵功较小;在相同的加热面积下所能吸收的热量更大,而且更有利于反应器内温度的均匀分布,从而提高甲醇的转化率、减小出口CO的含量。研究结果表明,仿蜂巢分叉微通道结构具有较好的重整制氢综合性能,并可改善氢气产出的品质。 相似文献
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20.
Low temperature steam reforming of methane mainly to hydrogen and carbon dioxide (CH4 + 2H2O → 4H2 + CO2) has been performed at 773 and 823 K over a commercial nickel catalyst in an equilibrium-shift reactor with an 11-μm thick palladium membrane (Mem-L) on a stainless steel porous metal filter. The methane conversion with the reactor is significantly higher than its equilibrium value without membrane due to the equilibrium-shift combined with separation of pure hydrogen through the membrane. The methane conversion in a reactor with an 8-μm membrane (Mem-H) is similar to that with Mem-L, although the hydrogen permeance through Mem-H is almost double of that through Mem-L. The amount of hydrogen separated in the reaction with Mem-H is significantly large, showing that the hydrogen separation overwhelms the hydrogen production because of the insufficient catalytic activity. 相似文献