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1.
Four silica‐supported nickel catalysts with Ni content of 10 wt% were prepared by impregnation and coprecipitation methods with or without microwave‐assisted calcination. The prepared catalysts were characterized by some techniques (BET, XRD, TEM, XPS, H2‐TPR, etc.) and evaluated with respect to steam reforming of ethanol (SRE) for hydrogen production. The results show that the prepared Ni/SiO2 catalysts are all very active and selective for SRE. The high activity of the four catalysts may benefit from their high specific areas and the good dispersion of active components on the carrier. The rate of carbon deposition decreases with reaction temperature especially below 450 °C. The maximum hydrogen yield of 4.54 mol H2/mol EtOH‐reacted can be obtained over the Ni/SiO2 catalyst by the microwave‐assisted coprecipitation method at a reaction temperature of 600 °C, EtOH/H2O molar ratio of 1:12, liquid hourly space velocity of 11.54 h?1 and time on stream within 600 min. The Ni/SiO2 catalysts with microwave modification exhibits better performances of hydrogen production, stability and resistance to carbon deposition than that without microwave modification preparation, which is mainly attributed to that the microwave‐assisted treatment can decrease the catalyst acidity and enhance the interaction between metal support. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
Catalytic steam reforming of ethanol is considered as a promising technology for producing H2 in the modern world. In this study, using a fixed‐bed reactor, steam reforming of ethanol was performed for production of carbon nanotubes (CNTs) and H2 simultaneously at 600°C on Ni/CaO catalysts. Commercial CaO and a synthetic CaO prepared using sol‐gel were scrutinized for ethanol's catalytic steam reforming. Analysis results of N2 isothermal adsorption indicate that the CaO synthesized by sol‐gel has more pore volume and surface area in comparison with the commercial CaO. When Ni was loaded, the Ni/CaO catalyst shows an encouraging catalytic property for H2 production, and an increase in Ni loading could improve H2 production. The Ni/CaO catalyst with sol‐gel CaO support has presented a higher hydrogen production and better catalytic stability than the catalysts with the commercial CaO support at low Ni loading. The highest hydrogen yield is 76.8% at Ni loading content of 10% for the Ni/sol‐gel CaO catalyst with WHSV of 3.32/h and S/C ratio of 3. The carbon formed after steam reforming primarily consists of filamentous carbons and amorphous carbons, and CNTs are the predominant type of carbon deposition. The deposited extent of carbon on the used Ni/CaO catalyst lessen upon more Ni loading, and the elongated CNTs are desired to be formed at the surface of the Ni/sol‐gel CaO catalyst. Thus, an efficient process and improved economic value is associated with prompt hydrogen production and CNTs from ethanol steam reforming.  相似文献   

3.
The catalyst, Ni nano-particles supported on Y2O3, which was prepared by three methods, was studied. The structural properties of the catalysts were tested through X-ray diffraction and BET area. The catalyst of Ni/Y2O3 exhibits high activity for ethanol steam reforming with conversion of ethanol of 98% and selectivity of hydrogen of 38% at 300°C, conversion of ethanol of 98% and selectivity of hydrogen of 55% at 380°C. With temperature increasing to and above 500°C, the conversion of ethanol increased to 100%, but the selectivity of hydrogen did not increase so much, it was 58% at 600°C. The catalyst has long-term stability for steam reforming of ethanol and is a good choice for ethanol processors for fuel cell applications.  相似文献   

4.
The rich‐hydrogen generation from ethanol steam reforming over NiZr, which is used as an anode material in solid oxide fuel cells, ‐loaded MCM‐48 (NiZr/MCM‐48) catalyst was investigated in this study. We used an impregnation approach to synthesize an MCM‐48 (70.0 wt‐%) support loaded with bimetallic NiZr (30.0‐wt%, Ni:Zr atomic ratio = 4:6, 5:5, and 6:4), and the prepared catalysts were applied to the steam‐reforming reactions of ethanol. These three bimetallic NiZr/MCM‐48 catalysts exhibited significantly higher reforming reactivity than the mono‐metal, Ni‐loaded MCM‐48 (Ni/MCM‐48) catalyst. The hydrogen production was started from 350°C over the three NiZr/MCM‐48 catalysts, compared to above 550°C over the Ni/MCM‐48 catalyst. The catalytic performance was affected by the Zr content. The H2 production and ethanol conversion were maximized at 85% and 95%, respectively, over Ni4Zr6/MCM‐48 at 750°C for 1 h at CH3CH2OH:H2O = 1:1 and a gas hourly space velocity of 4000 h‐1. This high performance was maintained for up to 60 h. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

5.
Direct ethanol fuel cells (DEFCs) offer an attractive alternative to fossil fuel-powered devices due to their high energy density and environmental benignity. However, high cost and poor stability of catalysts are still the main obstacles for the commercialization of DEFCs. Herein, a novel catalyst comprising PtRh alloys anchored on carbon nanotubes that decorated with tungsten nitride (Pt9Rh-WN/CNTs) was synthesized via impregnation-reduction method and followed by thermal annealing in N2. The X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and transmission electron microscopy (TEM) are employed to characterize the corresponding physico-chemical properties of the as-prepared catalysts. Electrocatalytic performance for ethanol oxidation is evaluated by cyclic voltammetry, linear scan voltammetry, CO-stripping voltammograms, chronoamperometry and chronopotentiometry. The current density on Pt9Rh-WN/CNTs is 484.8 mA mgPt?1, which is much higher than that of Pt9Rh/CNTs (305.7 mA mgPt?1) and Pt/CNTs (135.1 mA mgPt?1). Most importantly, the onset potential for CO oxidation on Pt9Rh-WN/CNTs is 0.27 V, which is more negative than that on Pt9Rh/CNTs (0.37 V) and Pt/CNTs (0.40 V). Therefore, the Pt9Rh-WN/CNTs catalyst displays both outstanding catalytic activity and excellent CO-poisoning tolerance for ethanol oxidation. Synergistic effects arising between WN and PtRh alloy along with nitrogen-doping effects of CNTs with ammonia are proposed to contribute to the outstanding performance of this catalyst in ethanol oxidation.  相似文献   

6.
Ce or Zr promoted CuZn/CNTs (carbon nanotubes) catalysts were synthesized by microwave-assisted polyol, co-precipitation and impregnation methods and were used to generate hydrogen by methanol steam reforming (MSR) process. The physico-chemical properties of the prepared catalysts were analyzed by BET, XRD, FT-IR, TEM, FE-SEM, EDX-dot mapping and H2-TPR methods. The effect of various operating parameters on methanol conversion and selectivity of gaseous products was investigated. The results indicated that the addition of 2 wt% CeO2 promoter on CuZn/CNTs catalyst synthesized by impregnation route (CuZn/CNTs (Imp)) increased its methanol conversion from 81.3 to 85.2%, and decreased its CO selectivity from 6.2 to 3.8% at 300 °C, WHSV of 7.5 h?1 and S/C molar ratio of 2. In addition, the CeCuZn/CNTs catalyst prepared via the microwave-assisted polyol route (CeCuZn/CNTs (Pol)) exhibited the best catalytic activity with 98.2% hydrogen selectivity, 2.6% CO selectivity and 94.2% methanol conversion at 300 °C. Furthermore, a 48 h continuous MSR reaction at 300 °C, identified CeCuZn/CNTs (Pol) as the most stable catalyst due to its higher metal particle dispersion and better interaction between the active phase and the CNTs support.  相似文献   

7.
Na+-intercalated carbon nanotubes (Na-CNTs) were obtained by impregnation of CNTs with sodium acetate followed by annealing at high temperatures under argon. Stable Na-CNTs-supported Pt catalysts (Pt/Na-CNT catalysts) were then prepared for hydrogen purification via preferential CO oxidation in a H2-rich stream (CO-PROX). Characteristic studies show that the content of Na+ species in CNTs is increased with increased annealing temperature and the Pt nanoparticles with an average size of 2–3 nm are uniformly dispersed on the surfaces of Na-CNTs. An optimized Pt/Na-CNT catalyst with 5 wt% Pt loading can completely remove CO from 40 °C to 200 °C. This catalyst also exhibits long-term stability for 1000 h at 100 °C in feed gas containing 1% CO, 1% O2, 50% H2, 15% CO2, and 10% H2O balanced with N2. The electron transfer between the Pt nanoparticles and Na+ species plays an important role in enhancing the CO-PROX performance of the catalyst.  相似文献   

8.
Replacement of precious platinum (Pt) or ruthenium oxide (RuO2) catalysts with efficient, cheap and durable electrocatalysts from earth-abundant elements bifunctional alternatives would be significantly beneficial for key renewable energy technologies including overall water splitting and hydrogen fuel cells. Despite tremendous efforts, developing bifunctional catalysts with high activity at low cost still remain a great challenge. Here, we report a nanomaterial consisting of core-shell-shaped Fe–Co3O4 grown on carbon nanotubes (Fe–Co3O4/CNTs) and employed as a bifunctional catalyst for the simultaneous electrocatalysts on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The Fe–Co3O4/CNTs electrocatalyst outperforms the commercial RuO2 catalyst in activity and stability for OER and approaches the performance of Pt/C for HER. Particularly, it shows superior electrocatalytic activity with lowering overpotentials of 120 mV at 10 mA cm?2 for HER and of 300 mV at 10 mA cm?2 for OER in 1 M KOH solution. The superior catalytic activity arises from unique core-shell structure of Fe–Co3O4 and the synergetic chemical coupling effects between Fe–Co3O4 and CNTs.  相似文献   

9.
Hydrogen production by steam reforming of ethanol (SRE) was studied using steam-to-ethanol ratio of 3:1, between the temperature range of 150–450 °C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al2O3). The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures. The idea to develop CNT-based catalysts that have high selectivity for H2 is one of the driving forces for this study. The catalytic performance was evaluated in terms of ethanol conversion, product gas composition, hydrogen yield and selectivity to hydrogen. The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied. Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 °C. The highest hydrogen yield of 2.5 is, however, obtained over the Co/CNT catalyst at 450 °C. The formation of CO and CH4 was very low over the Co/CNT catalyst compared to all the other tested catalysts. The Pt and Rh CNT-based catalysts were found to have low activity and selectivity in the SRE reaction. Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e.g. the fuel cell applications.  相似文献   

10.
In order to improve hydrogen production and reduce tar generation during the biomass gasification, a catalyst loaded Fe‐Ce using calcined olivine as the support (Fe‐Ce/olivine catalysts) was prepared through deposition‐precipitation method. The characteristics of catalysts were determined by XRF, BET, XRD, and FTIR. Syngas yield, hydrogen yield, and tar yield were used to evaluate the catalyst activity. Meanwhile, the stability of catalysts was also studied. The results showed that the specific surface area and pore volume of olivine after calcined at high temperature were improved which was beneficial for the load of metals. α‐Fe2O3 and CeO2 were the main active component of Fe‐Ce/olivine catalyst. The Fe‐Ce/olivine catalyst displayed a good performance on the catalytic gasification of pine sawdust with a syngas yield of 0.93 Nm3/kg, H2 yield of 21.37 mol/kg, and carbon conversion rate of 55.14% at a catalytic temperature and gasification temperature of 800°C. Meanwhile, the Fe‐Ce/olivine catalyst could maintain a good stability after 150 minutes used.  相似文献   

11.
In the study, a different support material based on ZnCl2‐treated Spirulina microalgal strain (SSMS‐ZnCl2) was prepared. Then, the SSMS‐ZnCl2‐CoB catalysts were used as a very efficient catalyst to produce hydrogen via the SB methanolysis. The SB concentration, Co metal percentage in the supported‐catalyst, ZnCl2 concentration, ZnCl2 impregnation time, temperature, and reusability experiments were performed. The maximum hydrogen generation rates (HGR) for the SSMS‐ZnCl2‐CoB at 30°C and 60°C were found to be 9266 and 36 366 mL min?1 gcat?1, respectively. In addition, TOF values for 30°C and 60°C were calculated 33 and 110 L·molH2·molCo?1·min?1 for the methanolysis of SB with SSMS‐ZnCl2‐CoB catalyst. The activation energy was 31.13 kJ mol?1. The reusability experiments were repeated five times under the same conditions. The almost 100% conversion was obtained at each use. XRD, FTIR, TEM, SEM‐EDX, and ICP‐MS analysis were performed for SSMS‐ZnCl2‐CoB characterization.  相似文献   

12.
Uniformly dispersed Ni catalysts supported on SiO2 wash-coated Ni foams were synthesized by the wet impregnation method and successfully applied for methane catalytic decomposition (MCD) at atmospheric pressure. All the prepared catalysts exhibited high catalytic stability. The effects of reaction temperature, space velocity, Ni loading on the MCD performance and the morphologies of the as-prepared CNTs were investigated. The results show that high reaction temperature, low space velocity, and high Ni loading enhanced the hydrogen concentration in the outlet gases. Additionally, SEM and TEM observations indicate that the size (diameter) distribution of the as-prepared CNTs became broader with increasing reaction temperature and Ni loading, respectively. The uniform nickel-foam-supported CNTs and relatively high concentration of hydrogen were obtained simultaneously at 650 °C and at a weight hourly space velocity of 1 L g−1cat h−1 by the catalyst with 20 wt% Ni. Raman spectroscopy reveals that the uniform MCNTs had a high degree of amorphization.  相似文献   

13.
In the present work acid‐treated Ni catalyst was investigated for the steam reforming (SR) of bio‐ethanol. Influential factors, such as reaction temperature, water‐to‐ethanol molar ratio and liquid hourly space velocity (LHSV), were investigated. The conversions were always complete at temperatures above 773 K, regardless of the changes of the reaction conditions. The yield to hydrogen increased with the increase in temperature and H2O/C2H5OH molar ratios. The hydrogen yield up to 84% was reached under conditions: 923 K, LHSV of 5.0 ml g−1 h−1, H2O/C2H5OH ratio of 10 over the acid‐treated Ni catalyst. The effects of the influential factors on the side reactions and the distribution of byproducts were discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

14.
A series of Ni/MgO catalysts have been prepared by a urea–nitrate combustion method, studied for the ethanol steam reforming, and compared with Ni/ZnO and Ni/Al2O3. The results show that Ni/MgO is superior to the latter two types of catalysts, especially in terms of H2 yield. Influential factors, including Ni loading, temperature, water‐to‐ethanol molar ratio, and liquid hourly space velocity, are investigated with the Ni/MgO catalyst. The conversions are always complete at temperatures above 773 K, regardless of the changes of the other reaction conditions. The hydrogen yield increases with increasing temperature and H2O/C2H5OH molar ratios, with up to 75% being obtained at 873 K, liquid hourly space velocity (LHSV) of 5.0 ml g–1 h–1 and H2O/C2H5OH molar ratio of 10. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
Ni-based catalysts were synthesized in water, methanol and ethanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst for the first time was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid and acetic acid including different concentrations. The maximum hydrogen production rates obtained in the hydrolysis reaction including 0.5 M phosphoric acid and 0.1 M acetic acid of the Ni-based catalyst prepared in ethanol solvent were 5214 and 3650 ml g?1 min?1, respectively.  相似文献   

16.
Formic acid (FA, HCOOH), a convenient and safe hydrogen storage material, has the great potential for fuel cell applications. However, hydrogen generation of FA is inefficient in the presence of heterogeneous catalysts at relatively low temperatures, which remains a big challenge. Herein, La2O3-modified highly dispersed AuPd alloy nanoparticles (AuPdLa2O3) with small particle size have been successfully anchored on carbon nanotubes (CNTs) by a facile co-reduction route. Moreover, the catalyst exhibits excellent catalytic activity and 100% hydrogen selectivity for hydrogen generation in the formic acid/sodium formate (FA/SF) system with the initial turnover frequency (TOF) value of 589 mol H2 mol?1 catalyst h?1 at 50 °C and 280 mol H2 mol?1 catalyst h?1 even at room temperature (25 °C). The present Au0.3Pd0.7-(La2O3)0.6/CNTs with superior catalysis on FA dehydrogenation without any CO generation at room temperature can not only pave the way for practical application of hydrogen storage system, but also can be extended to other catalysis system.  相似文献   

17.
Hydrogen peroxide (H2O2) and the reduction/oxidation by‐products of peroxide are non‐toxic to humans and the environment. Simple, low‐concentration hydrogen‐peroxide solutions used as fuel and direct peroxide/peroxide fuel cells (DPPFCs) face significant challenges in the development of a new class of power generators. A power density of 10 mWcm?2 at a cell potential of 0.55 V have been achieved with a DPPFC composed of carbon‐paper‐supported nickel as the anode catalyst and carbon‐paper PbSO4 as the cathode catalyst. The catalysts have been prepared by electroless deposition. Using non‐precious metals rather than platinum in our FC makes the cell cost effective comparable to that of PEMFCs. Additionally, as a low‐price fuel, H2O2 reduces the cost of this FC. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

18.
The hydrogen safety issue is spotlighted as the hydrogen process is extended. For this reason, we studied catalysts for H2 oxidation at room temperature to ensure hydrogen safety. Catalysts were prepared by different preparation methods and compared to evaluate the role of Pt and Pd in Pt–Pd/TiO2 catalysts. The catalytic activity was significantly enhanced when activity metal size was small and it was exposed to catalyst surface to a high Pd ratio. For the 0.1%Pt-0.9%Pd/TiO2 catalyst, high hydrogen conversion of 90% was obtained under the condition of 0.5% hydrogen injection. To understand the correlation between activity and characteristics of catalyst, the physicochemical characteristics of the various catalysts were investigated by X-ray photoelectron spectroscopy (XPS), temperature-programmed oxidation and reduction (TPOR) and Field Emission-Transmission Electron Microscope (FE-TEM) analysis. From these analysis, it was found that Pt served the role of highly dispersion of active metal (Pt–Pd) and as with increasing Pd ratio of active metal, hydrogen activity was increased, which indicates that hydrogen oxidation had proceeded on the Pd site. Finally, the valence state of the Pd influenced hydrogen oxidation activity of Pt–Pd/TiO2, which increased with increasing ratio of Pd0/PdTotal.  相似文献   

19.
Zirconia supports were prepared by a sol–gel method (S-ZrO2) and by a templating sol–gel method (M-ZrO2). Nickel catalysts supported on zirconia were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. For comparison, a commercial zirconia (C-ZrO2) was also employed as a support for nickel catalyst. The effect of preparation method of zirconia on the catalytic property and catalytic performance of supported nickel catalysts (Ni/C-ZrO2, Ni/S-ZrO2, and Ni/M-ZrO2) was investigated. The crystalline and physical property of zirconia supports and the catalytic performance of supported nickel catalysts were strongly affected by the preparation method of zirconia. BET surface area and pore volume were decreased in the order of M-ZrO2 > S-ZrO2 > C-ZrO2. Both M-ZrO2 and S-ZrO2 supports showed only tetragonal phase of ZrO2, while C-ZrO2 support exhibited tetragonal and monoclinic phases of ZrO2. Crystalline size of nickel species in the Ni/ZrO2 catalysts decreased with increasing surface area and pore volume of ZrO2 supports. All the Ni/ZrO2 catalysts exhibited 100% conversion of ethanol at 500 °C, while product distributions over the Ni/ZrO2 catalysts were different depending on the preparation method of zirconia. Among the catalysts tested, the Ni/M-ZrO2 catalyst showed the best catalytic performance in hydrogen production by auto-thermal reforming of ethanol. Well developed mesopore, high surface area, and pure tetragonal phase of ZrO2 were responsible for fine nickel dispersion and high catalytic performance of Ni/M-ZrO2. C–C bond cleavage reaction and methane steam reforming reaction were also accelerated over the Ni/M-ZrO2 catalyst.  相似文献   

20.
In this study, sorption-enhanced methanol steam reforming (SEMSR) was applied to generate high-purity hydrogen. The mesoporous MCM-41 as support and CuO, ZnO, CeO2, ZrO2 as active agents and promoters were employed for the catalyst preparation. In addition, (Li–Na–K) NO3·MgO as a CO2 adsorbent was prepared by the wet mixing method. The fresh and used catalysts were characterized by XRD, BET, FTIR, FESEM, TEM, H2-TPR and TGA analyses. Also, the CO2 sorbent was studied by XRD, BET, FESEM, TEM and TGA analyses before and after the reaction. The SEMSR performances of the synthesized catalyst and adsorbent were evaluated experimentally in a fixed-bed reactor. The effect of various conditions such as temperature, WHSV, feed molar ratio and sorbent/catalyst ratio were investigated. The best results were obtained at 300 °C, a feed molar ratio (water/methanol) of 2:1, a WHSV of 1.62 h?1, and the sorbent/catalyst ratio of 8:1, which produced 99.8% hydrogen, 25% more than the hydrogen production during conventional methanol steam reforming. Moreover, the cyclic stability of the catalyst and the sorbent was studied for 10 cycles.  相似文献   

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