Ni、Fe负载CaO催化剂作用下生物油模化物水蒸气催化重整制氢研究

采用浸渍法制备Ni/CaO、Fe/CaO、Ni-Fe/CaO催化剂,用于生物油模化物乙酸水蒸气催化重整反应.对反应前后催化剂进行BET、H2-TPR、CO2-TPD、XRD等表征.通过比较3种催化剂重整反应性能得出Ni/CaO催化剂具有最佳性能.进一步研究在Ni/CaO催化剂参与下反应温度、水碳比(S/C)、液时空速(...     

热裂解气中模型化合物萘的催化转化

用浸渍法制备了一系列不同载体和不同活性组分的催化剂,研究了催化剂载体、活性组分及镍含量对热裂解气中模型化合物萘反应性能的影响,比较了氧气和水蒸气在有催化剂在无催化剂条件下对萘转化率和CO、H2产率的影响,实验发现,Al2O3和Ni分别是萘催化转化催化剂中较好的载体和活性组分,在适当的反应条件和催化剂存在下,萘的转化率可达90%以上。     

Catalytic performance of a high-cell-density Ni honeycomb catalyst for methane steam reforming

The catalysis of methane steam reforming (MSR) by pure Ni honeycombs with high cell density of 2300 cells per square inch (cpsi) was investigated to develop efficient and inexpensive catalysts for hydrogen production. The Ni honeycomb catalyst was assembled using 30-μm-thick Ni foils, and showed much higher activity than that of a Ni honeycomb catalyst with cell density of 700 cpsi at a steam-to-carbon ratio of 1.36 and a gas hourly space velocity of 6400 h^?1 in a temperature range of 873–1173 K. Notably, the activity increased approximately proportional to the increasing geometric specific surface area of the honeycombs. The turnover rate of the Ni honeycomb catalyst was higher than that of supported Ni catalysts. The changes in chemical state of the Ni catalyst during hydrogen reduction and MSR reaction were analyzed by in situ X-ray absorption fine structure spectroscopy, which revealed that deactivation was mainly due to oxidation of the surface Ni atoms. These results demonstrated that the high-cell-density Ni honeycomb catalyst exhibits good performance for MSR reaction, and easy regeneration of the deactivated Ni honeycomb catalyst is possible only via hydrogen reduction.     

Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts for hydrogen production from methane and methanol fuels

In this study, methane and methanol steam reforming reactions over commercial Ni/Al₂O₃, commercial Cu/ZnO/Al₂O₃ and prepared Ni–Cu/Al₂O₃ catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al₂O₃ catalyst with respect to the commercial Ni/Al₂O₃ (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al₂O₃ (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H₂ selectivity, CO₂ and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H₂, with H₂ selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al₂O₃ catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al₂O₃ (8.9%) and commercial Cu/ZnO/Al₂O₃ catalysts (3.5%).     

Hydrogen production by ethanol steam reforming over M-Ni/sepiolite (M = La,Mg or Ca) catalysts

Ethanol steam reforming (ESR) is a technology of great promise for hydrogen production but designing highly efficient, green and inexpensive Ni-based catalysts for inhibiting metal sinter and carbon deposition and increasing catalyst activity and stability is still a key challenge. In this paper, the M-Ni/Sepiolite catalysts (M-Ni/SEP, M = La, Mg or Ca) were synthesized using a hydrothermal-assisted impregnation method. The results from characterizations such as N₂ adsorption-desorption, XRD, H₂-TPR, XPS, HRTEM and NH₃/CO₂-TPD showed that La, Mg and Ca promoters can facilitate the dispersion and exposure of Ni⁰ active sites, enhance the metal-support interaction and modify surface acid/alkaline sites. Furthermore, the results of catalyst activity tests in ESR demonstrated that the Ca–Ni/SEP catalyst exhibited the highest carbon conversion of 95% and hydrogen yield of 65%, attributed to the small mean Ni particle size, strong metal-support interaction, abundant surface Ni⁰ active sites and modified surface alkaline/acid sites. According to the carbon deposition analyses, it was observed in Ca–Ni/SEP that the carbon deposition amount was evidently decreased, and the graphitic degree of coke was increased due to the increased metal site amount.     

乙酸水蒸气重整制氢中载体组成对催化剂性能的影响

采用溶胶–凝胶法结合湿浸渍法制备了Ni/ZrO2、Ni/La2O3-ZrO2和Ni/La2O3催化剂,采用XRD、BET、TG及 H2-TPR等方法对催化剂的结构和性质进行了表征。通过生物油模型物乙酸水蒸气重整反应,探讨了载体组成对催化剂性能和积炭形成的影响。载体组分不同的Ni催化剂具有不同的Ni颗粒尺寸、孔结构和Ni–载体相互作用,这对乙酸水蒸气重整反应路径有重要影响。催化剂Ni/70wt%La2O3-ZrO2在乙酸水蒸重整反应中表现出较好的催化性能和稳定性,在反应时间10 h内,氢气产率保持在76.05%以上;同时,TG和XRD分析结果表明,Ni/70wt%La2O3-ZrO2具有较好的抗烧结能力和较低的积炭率。     

Catalytic features of Ni/Ba–Ce0.9–Y0.1 catalyst to produce hydrogen for PCFCs by methane reforming

Methane reforming in steam (SR), auto-thermal (ATR) and partial oxidation (POX) conditions over Ni/Ba–Ce_0.9–Y_0.1 catalyst was investigated in the temperature range 500–700 °C. Catalyst presents a satisfying activity in POX condition only. BCY carrier was not stable in the presence of CO₂ and, irrespective of reaction conditions, it reacts with CO₂ giving rise to the formation of BaCO₃ and CeO₂. The very low activity observed in SR conditions was due to the negative role exerted by water strongly absorbed on catalyst surface, limiting so the accessibility and reduction state of Ni active sites. In POX condition catalyst is active and satisfying H₂ yield can be reached by operating at T = 700 °C. A significant reduction of coke formation was observed by operating in POX at 700 °C. On the contrary, in ATR condition at the same reaction temperature huge amount of filamentous coke was observed.     

生物油水蒸气催化重整制氢研究进展

氢气作为一种环境友好的清洁能源,人们对它的关注度越来越高。生物油水蒸气催化重整制氢是未来制氢的一种可行性方案。本文综述了近年来生物油水蒸气重整制氢的研究进展。主要从重整制氢反应机理、热力学分析、催化重整催化剂、代表性的重整反应器方面进行讨论,指出催化重整中的主要问题是碳沉积导致催化剂失活。研制高活性、高稳定性、高选择性的催化剂是生物油催化重整制氢的关键。     

Oxidative steam reforming of ethanol over Ru–Al2O3 catalyst in a dense Pd–Ag membrane reactor to produce hydrogen for PEM fuel cells

This study focuses on the influence of oxygen addition on ethanol steam reforming (ESR) reaction performed in a dense Pd–Ag membrane reactor (MR) for producing hydrogen directly available for feeding a polymer electrolyte membrane fuel cell (PEMFC). In particular, oxygen addition can prevent ethylene and ethane formation caused by dehydration of ethanol as well as carbon deposition. The MR is operated at 400 °C, H₂O:C₂H₅OH = 11:1 as feed molar ratio and space velocity (GHSV) ∼2000 h⁻¹. A commercial Ru-based catalyst was packed into the MR and a nitrogen stream of 8.4 × 10⁻² mol/h as sweep gas was flowed into the permeate side of the reactor. Both oxidative ethanol steam reforming (OESR) and ESR performances of the Pd–Ag MR were analyzed in terms of ethanol conversion to gas, hydrogen yield, gas selectivity and CO-free hydrogen recovery by varying O₂:C₂H₅OH feed molar ratio and reaction pressure. Moreover, the experimental results of the OESR and ESR reactions carried out in the same Pd–Ag MR are compared in order to point out the benefits due to the oxygen addition. Experimentally, this work points out that, overcoming O₂:C₂H₅OH = 1.3:1, ethanol conversion is lowered with a consequent drops of both hydrogen yield and hydrogen recovery. Vice versa, a complete ethanol conversion is achieved at 2.5 bar and O₂:C₂H₅OH = 1.3:1, whereas the maximum CO-free hydrogen recovery (∼30%) is obtained at O₂:C₂H₅OH = 0.6:1.     

Cu/La2O3/Al2O3催化剂上甲醇水蒸气重整制氢反应

研究以并流共沉淀法制备Cu/La2 O3 /Al2 O3 系列催化剂催化甲醇水蒸气重整制氢反应过程 ,考察了La2 O3含量、反应温度、水醇比、液体空速 (WHSV)等因素对催化剂活性的影响。结果表明 :催化剂表现出较好的低温活性、高氢气选择性和稳定性。La2 O3 质量分数为 15 % ,在 2 5 0℃反应时 ,催化剂活性表现最佳 ,甲醇摩尔转化率为94 .5 % ,氢气选择性为 10 0 % ,CO摩尔分数为 1.0 5× 10 -7。     

Thermodynamic analysis and heat integration for hydrogen production from bio-butanol for SOFC application: Steam reforming vs. autothermal reforming

Thermodynamic analysis of hydrogen production by steam reforming and autothermal reforming of bio-butanol was investigated for solid oxide fuel cell applications. The effects of reformer operating conditions, e.g., reformer temperature, steam to carbon molar ratio, and oxygen to carbon molar ratio, were investigated with the objective to maximize hydrogen production and to reduce utility requirements of the process and based on which favorable conditions of reformer were proposed. Process flow diagram for steam reforming and autothermal reforming integrated with solid oxide fuel cell was developed. Heat integration with pinch analysis method was carried out for both the processes at favorable reformer conditions. Power generation, electrical efficiency, useful energy for co-generation application, and utility requirements for both the processes were compared.