Startup and Transients in Millisecond Chemical Reactors

短接触时间化学反应器对于以更高的效率、更低的成本和更少的污染将轻质烷烃转化为有用的化学品具有很大的希望。 该技术的重要应用是将天然气转化为液体燃料和将烷烃燃料重整为燃料电池用氢。 这项技术的实施需要表征的过程和机制。 稳态行为是相当好的理解，和以前的赠款特点的性能和这些过程的机制。 然而，瞬变的特点，必须制定起燃协议，并进一步了解在短接触时间的化学反应器中的烷烃氧化的机制。我们有一个系统的程序来检查短接触时间化学反应器的瞬态行为。 这项研究有两个主要目标：（1）使用瞬态实验，以进一步表征这些过程的机制和（2）的快速点火和瞬态的应用，如小型燃料电池的燃料处理的方法的发展。实验将涉及质谱和温度测量响应饲料和同位素切换的阶跃变化。 我们将通过流动气体滴定法研究催化剂上碳和氧的形成和去除。 启动瞬变也将通过不同气体混合物的点火进行检查，这些气体混合物可以催化反应或均匀反应，以快速加热到点火温度。 其他实验将涉及在不同频率下的组合物的周期性强制，在短接触时间下的气-液反应，以及涉及使用燃料喷射器的燃料的闪蒸的反应。 我们还将发展能力，以检查时间依赖性和分叉行为的启动和熄灭的快速耦合放热和吸热过程中的催化壁反应器。这些实验将通过计算流体动力学进行分析，使用基本步骤模型模拟启动和瞬变过程中的温度和覆盖率。 这将导致更基本的基本步骤模型和这些系统中的分岔行为的表征，这将是必不可少的，在开发新的短接触时间的化学过程。燃料电池将不会是实用的单位燃料重整方法和快速点火战略的发展，这项研究将是一个关键因素，在这些任务。

Short contact time chemical reactors have great promise for conversion of light alkanes into useful chemicals with greater efficiency, lower cost, and less pollution. Important applications of this technology are conversion of natural gas to liquid fuels and reforming of alkane fuels to hydrogen for fuel cells. Implementation of this technology requires characterization of the processes and mechanisms. Steady state behavior is fairly well understood, and the previous grant characterized performance and mechanisms of these processes. However, transients must be characterized to develop lightoff protocols and to further understand the mechanisms of alkane oxidation in short contact time chemical reactors. We have a systematic program to examine the transient behavior of short contact time chemical reactors. This research has two major objectives: (1) use of transient experiments to further characterize the mechanisms of these processes and (2) the development of methods for fast lightoff and transients in applications such as fuel processing for small fuel cells. Experiments will involve mass spectrometric and temperature measurement of responses to step changes in feeds and isotope switching. We will examine carbon and oxygen formation and removal on the catalyst by titration with flowing gases. Startup transients will also be examined by ignition with different gas mixtures that react either catalytically or homogeneously to attain rapid heating to ignition temperatures. Other experiments will involve periodic forcing of composition at different frequencies, gas-liquid reactions at short contact time, and reactions involving flash vaporization of fuel using fuel injectors. We will also develop capabilities to examine time dependences and bifurcation behavior in startup and extinction of fast coupled exothermic and endothermic processes in the catalytic wall reactor. These experiments will be analyzed by computational fluid dynamics using elementary step models to simulate temperatures and coverages in startup and with transients. This will lead to more fundamental elementary step models and characterization of bifurcation behavior in these systems that will be essential in developing new short contact time chemical processes. Fuel cells will not be practical unit fuel reforming methods and fast lightoff strategies are developed, and this research will be a key ingredient in these tasks.