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首页> 外文会议>Pacific Rim Meeting on Electrochemical and Solid-State Science >Reaction Kinetics of Catalytic Dry Reforming of Methane on Spinel-Derived Nickel Catalyst at Low-Temperature Using an in-Situ Stagnation-Flow Reactor
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Reaction Kinetics of Catalytic Dry Reforming of Methane on Spinel-Derived Nickel Catalyst at Low-Temperature Using an in-Situ Stagnation-Flow Reactor

机译：用原位停滞 - 流动反应器在低温下尖晶石衍生镍催化剂催化干重整的反应动力学

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Dry reforming of methane (DRM) has been implemented to hydrocarbon-fueled ceramic fuel cells. This reduces their carbon footprint by utilizing carbon dioxide as a reactant. However, its application to low-temperature ceramic fuel cells has not been investigated, in which sluggish reforming kinetics and low durability induced by carbon coking should be resolved and overcome. In this study, DRM at low-temperature is examined by using spinel-derived nickel catalyst on aluminum oxide employed in a stagnation-flow reactor. With increasing calcination temperature, homogeneous mixture of nickel oxide and aluminum oxide show phase transition from mechanically mixed Ni/Al_2O_3 to chemically packed crystallite Ni/Al_2O_4 spinel structure. Due to their chemical structure, they have two different size of active nickel particle on aluminum oxide under reducing environment and show different catalytic activity. To elucidate the fundamental surface properties of fabricated catalysts, surface characterization technique such as XRD, TEM, BET, TPR, and CO-chemisorption are used. After surface characterization, their performance for DRM and reaction mechanism are examined by powder setup with gas chromatography and in-situ stagnation-flow reactor with mass spectrometer. The stagnation-flow reactor enables micro quartz-probe sampling of the compositional boundary layer in the vicinity of the catalyst surface. The vertical distance of micro quartz-probe from the catalytic surface is manipulated by a step-motor, and sampled gas are quantitatively analyzed with a quadrupole mass spectrometer. This configuration also makes it relatively simple to resolve numerically the complex reacting flow environment coupled with mass/momentum/energy transport phenomena. A numerical model can examine quantitatively the net production rate of each elementary step (48-step surface reaction mechanism) with varying operating conditions. Intrinsic reaction parameters such as a sticking coefficient of reactant adsorption, pre-exponential factor and activation energy of each reaction step are tuned by using experimental measurements. To determine the main reaction pathways and rate-determining steps, partial equilibrium, activation energy of C-H bond in methane and C-O bond in carbon dioxide, a sensitivity analysis with respect to reaction parameters is conducted. It is elucidated that the dry reforming of methane is pre-dominantly rate-determined by methane dehydrogenation steps. Especially, at low temperature region, an apparent activation energy of methane conversion increases sharply with the temperature, whereas that of carbon dioxide shows a trivial increase. The simulation results also show the dependence of thermal/fluidic effects on reaction kinetics including the catalyst temperature, reactant flow rates, mass/thermal diffusion in a porous catalyst layer. In this study, the detailed elementary reaction steps are developed, which enables predicting the effect of the reacting-flow environment on the overall reaction kinetics of dry reforming of methane.
机译：甲烷（DRM）的干燥重整已实施至烃燃料陶瓷燃料电池。通过利用二氧化碳作为反应物，这降低了碳足迹。然而，尚未研究其在低温陶瓷燃料电池中的应用，其中应解决并克服由碳焦化引起的缓慢改造动力学和低耐久性。在该研究中，通过在停滞 - 流动反应器中使用的氧化铝上使用尖晶石衍生的镍催化剂来检查低温下的DRM。随着煅烧温度的增加，氧化镍和氧化铝的均匀混合物显示出从机械混合的Ni / Al_2O_3到化学填充的微晶Ni / Al_2O_4尖晶石结构的相转变。由于它们的化学结构，在还原环境下，它们在氧化铝上具有两种不同的活性镍颗粒，并显示出不同的催化活性。为了阐明制造催化剂的基本表面性质，使用表面表征技术，例如XRD，TEM，BET，TPR和共培养。表面表征后，通过用气相色谱法和原位停滞 - 流动反应器与质谱仪进行粉末设定检查其对DRM和反应机理的性能。停滞 - 流动反应器使得在催化剂表面附近的组成边界层的微石英探针采样。通过阶梯式电动机操纵来自催化表面的微石英探针的垂直距离，用四极谱质谱仪定量分析取样气体。这种配置还使得在数值上解析与质量/动量/能量传输现象的复杂反应流动环境相对简单。数值模型可以通过不同的操作条件定量地检查每个基本步骤（48步表面反应机制）的净生产率。通过使用实验测量，调节固有反应参数，例如反应性吸附的粘附系数，预指数因子和每个反应步骤的活化能。为了确定主要反应途径和速率确定步骤，部分平衡，C-H键在二氧化碳中的C-H键和C-O键的活化能，对反应参数进行敏感性分析。阐明甲烷的干燥重整是通过甲烷脱氢步骤预先统治的。特别是在低温区域，甲烷转化的表观激活能量随温度急剧增加，而二氧化碳的甲烷转化率急剧增加。仿真结果还显示了热/流体效应对包括催化剂温度，反应物流率，多孔催化剂层中的质量/热扩散的反应动力学的依赖性。在该研究中，开发了详细的基本反应步骤，这使得能够预测反应流动环境对甲烷干燥重整的总反应动力学的影响。

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