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首页> 外文学位 >Catalytic kinetics and thermal management in microchemical systems for distributed energy and portable power generation.
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Catalytic kinetics and thermal management in microchemical systems for distributed energy and portable power generation.

机译：微化学系统中的催化动力学和热管理，用于分布式能源和便携式发电。

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Catalytic kinetics and thermal management in fabricated microreactors were studied for the design of distributed energy and portable power production systems. Specifically, kinetically relevant experimental data was generated for the following chemistries: preferential oxidation (PROX) of CO in excess H2, water-gas shift (WGS), reverse water-gas shift (RWGS), and H2, CO, syngas, CH4, C2H 6, and C3H8 oxidation over a supported Pt/Al 2O3 catalyst. The effect of wall material properties and reactor configuration was also determined through the modeling, design, fabrication, and experimentation of microcombustors for integration with thermoelectrics and enhancement of thermal stability from heat recirculation.;CO oxidation over Pt was found to be structure sensitive, as the observed turnover frequency (TOF) rate increased with larger Pt crystallite sizes. A multisite, microkinetic model (containing reaction and diffusion steps) developed using density functional theory (DFT) energy barriers and thermodynamically consistent preexponentials for terraces (Pt(111)) and steps (Pt(211)) also predicts this trend. An excessive fraction of H2 was shown to enhance and inhibit CO oxidation at low and high temperature, respectively. By increasing the CO:O2 ratio in the presence of excess H2, CO conversions above the equilibrium value were observed and rationalized with a microkinetic model. WGS and RWGS experiments were performed at high temperatures (where RWGS is favorable) and positive order kinetics were observed for H2O and H2 in WGS and RWGS, respectively. In the catalytic combustion of syngas mixtures (1:1 and 1:3 for coal gas and methane reformate, respectively), high CO selectivities were observed at low temperatures. CO and H2 catalytic combustion experiments were also performed for comparison purposes. H2 catalytic oxidation was strongly inhibited by the presence of CO. Hysteresis was also observed at high H2 conversions and is discussed. Kinetic parameters were estimated for lean CH4, C 2H6, and C3H8 catalytic combustion. The relative activity was observed to be C3H8> C 2H6> CH4 and the catalytic combustion of small alkanes over Pt/Al2O3 was found to follow a homologous series. Thermal management of an integrated thermoelectric/single channel, catalytic microcombustor was studied using H2, CH3OH, and C3H8 fuels. Electrical power generation (maximum 0.65 W) with a thermal efficiency up to ∼ 1.1% was measured. Thermal management strategies, such as heat recirculation, were exploited with fabricated microreactors designed via computational fluid dynamics (CFD) for C3H8 combustion. It was shown through both experiments and simulation that catalytic heat recirculation burners have similar stability to single channel burners in the limit of highly conductive walls. In contrast, for low conductivity walls, heat recirculation proved to be effective at increasing combustion stability relative to single channel burners.
机译：研究了用于制造分布式能源和便携式发电系统的微型反应器的催化动力学和热管理。具体而言，针对以下化学物质生成了动力学相关的实验数据：过量H2中的CO的优先氧化（PROX），水煤气变换（WGS），反向水煤气变换（RWGS）和H2，CO，合成气，CH4，负载的Pt / Al 2O3催化剂上的C2H 6和C3H8氧化。还通过微燃烧器的建模，设计，制造和试验来确定壁材料性能和反应器配置的影响，以使其与热电一体化，并提高热再循环的热稳定性。发现Pt上的CO氧化对结构敏感，因为Pt晶粒尺寸越大，观察到的周转频率（TOF）速率越高。使用密度泛函理论（DFT）的能垒和阶地（Pt（111））和阶跃（Pt（211））的热力学一致的指数分布开发的多站点微动力学模型（包含反应和扩散步骤）也预测了这一趋势。过量的H2被证明分别增强和抑制了低温和高温下的CO氧化。通过在过量氢气存在下增加CO：O2的比例，可以观察到CO转化率高于平衡值，并通过微动力学模型进行了合理化。 WGS和RWGS实验在高温下进行（其中RWGS是有利的），并且在WGS和RWGS中分别观察到H2O和H2的正序动力学。在合成气混合物的催化燃烧中（煤气和甲烷重整产品分别为1：1和1：3），在低温下观察到高的CO选择性。为了比较目的，还进行了CO和H 2催化燃烧实验。 CO的存在强烈抑制了H2催化氧化。在高H2转化率下也观察到磁滞现象并进行了讨论。估算了贫CH4，C 2H6和C3H8催化燃烧的动力学参数。观察到相对活性为C 3 H 8＞ C 2H 6＞ CH 4，并且发现小烷烃在Pt / Al 2 O 3上的催化燃烧遵循同源序列。使用H2，CH3OH和C3H8燃料研究了集成热电/单通道催化微型燃烧器的热管理。测量了热效率高达〜1.1％的发电功率（最大0.65 W）。借助通过计算流体力学（CFD）设计的用于C3H8燃烧的微型反应器来开发热管理策略，例如热循环。通过实验和模拟都表明，在高导热壁的限制下，催化热循环燃烧器具有与单通道燃烧器类似的稳定性。相反，对于低电导率壁，相对于单通道燃烧器，热再循环被证明可以有效地提高燃烧稳定性。

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