Aqueous-phase reforming of oxygenated hydrocarbons over Sn-modified Ni catalysts
Aqueous-phase reforming of oxygenated hydrocarbons over Sn-modified Ni catalysts
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DOI：
10.1016/j.jcat.2003.10.022
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发表时间：
2004-02
影响因子：
7.3
通讯作者：
J. Shabaker;G. Huber;J. Dumesic
中科院分区：
文献类型：
--
作者：
J. Shabaker;G. Huber;J. Dumesic
在498和538 K的温度下，对Pt/Al2O3、Ni/Al2O3、NiSn/Al2O3、Raney-Ni和Raney-NiSn催化剂上的含氧烃水相重整进行了反应动力学测量。Raney-Ni、Raney-NiSn和Pt/ al2o3催化剂在水相重整过程中表现出良好的稳定性，而al2o3负载的Ni和NiSn催化剂在烧结过程中表现出失活。山梨糖醇、甘油和乙二醇溶液的水相重整在高转化率下产生由50-70 mol% H2、30-40 mol% CO2和2-11 mol%烷烃（干基）组成的流出气流。在Ni:Sn比为270:1的条件下，加入Sn使乙二醇重整制氢的选择性从35%提高到51%，而烷烃的选择性从44%降低到33%。当Ni:Sn比为14:1时，氢的选择性提高到90%，而烷烃的产生几乎消除。当系统压力降低到进料的气泡点（498 K时25.1 bar）时，烷烃的生成量减少，氢的选择性相应提高。在较高的反应器空间速度下操作，氢的选择性也最大。在Ni中加入Sn显著降低了CO键裂解生成甲烷的速率，同时保持了生成氢所需的足够高的CC键裂解速率。在498 K下，raney - ni基催化剂制氢的周转率比CO化学吸附的3 wt% Pt/ al2o3催化剂的周转率低几倍。然而，在498 K时，高CO吸收量和高密度的raney - ni基催化剂导致单位反应器体积产氢率与3wt % Pt/ al2o3相当。XRD、SEM和119sn Mössbauer光谱分析结果表明，Raney-NiSn催化剂由镍锡合金包裹的氧化铝和镍颗粒组成。暴露于反应条件后，锡主要以Ni3Sn合金的形式存在，少量的锡（IV）可能与氧化铝有关。
Reaction kinetics measurements were conducted for aqueous-phase reforming of oxygenated hydrocarbons over Pt/Al2O3, Ni/Al2O3, NiSn/Al2O3, Raney-Ni, and Raney-NiSn catalysts at temperatures of 498 and 538 K. Raney-Ni, Raney-NiSn, and Pt/Al2O3catalysts display good stability with time on stream during aqueous-phase reforming, whereas Al2O3-supported Ni and NiSn catalysts exhibit deactivation caused by sintering. Aqueous-phase reforming of sorbitol, glycerol, and ethylene glycol solutions produces an effluent gas stream composed of 50–70 mol% H2, 30–40 mol% CO2, and 2–11 mol% alkanes (dry basis) at high conversion. Addition of Sn to Ni improves the selectivity for production of H2by ethylene glycol reforming from 35 to 51% at a Ni:Sn ratio of 270:1, while the alkane selectivity is reduced from 44 to 33%. At a Ni:Sn ratio of 14:1, the hydrogen selectivity increases to 90%, while alkane production is nearly eliminated. As the system pressure decreases to the bubble point of the feed (25.1 bar at 498 K), production of alkanes decreases and the hydrogen selectivity increases accordingly. Hydrogen selectivity is also maximized by operation at higher reactor space velocities. The addition of Sn to Ni significantly decreases the rate of methane formation from CO bond cleavage, while maintaining sufficiently high rates of CC bond cleavage required for hydrogen formation. Turnover frequencies for hydrogen production at 498 K over Raney-Ni-based catalysts are several times lower than that over 3 wt% Pt/Al2O3based on CO chemisorption. However, the high CO uptakes and high densities of Raney-Ni-based catalysts lead to comparable rates of hydrogen production per unit reactor volume as 3 wt% Pt/Al2O3at 498 K. Results from XRD, SEM, and119Sn Mössbauer spectroscopy suggest that Raney-NiSn catalysts comprise alumina and nickel particles surrounded by a Ni–Sn alloy. After exposure to reaction conditions, Sn is present primarily as Ni3Sn alloy with small amounts of Sn(IV) probably associated with alumina.