SGER: Thermal Effects in Microwave Enhanced Catalysts

摘要CTS-9907322 J。托马斯/VPI这个研究项目的目的是提供答案的基本问题时，微波能量用于促进负载金属催化剂上的化学反应的热产生和传输。 这些材料由分布在多孔陶瓷基底内的纳米尺寸的金属颗粒组成。 微波场在化学反应中感兴趣的温度下不耦合到陶瓷载体，但由于电子量子限制，它们可以强烈耦合到金属颗粒。 这种现象提供了选择性地将催化剂颗粒加热到高于基质的温度的机会。 选择性加热可以导致对化学反应的更大控制和对所需产物的可能的高选择性。 微波增强化学催化的选择性增加已被报道，但原因尚不清楚。 由于难以测量纳米尺寸颗粒的温度，尚未实现选择性加热的直接验证。 该项目将采用基于中子吸收的理论建模和新的实验技术来确定催化剂颗粒是否容易受到微波的选择性加热。 纳米尺寸颗粒的温度测量不能通过常规技术来完成。 采用中子共振射线照相技术对催化剂颗粒和载体的温度进行解析。 该方法的成功可能为开发催化反应开辟一条新途径。

AbstractCTS-9907322J. Thomas/VPIThis research project is directed toward providing answers to fundamental questions concerning heat production and transport when microwave energy is used to promote chemical reactions on supported metal catalysts. These materials consist of nanometer-sized metallic particles distributed within a porous ceramic substrate. Microwave fields do not couple to the ceramic support at temperatures of interests in chemical reactions, but they may couple strongly to the metallic particles because of electron quantum confinement. This phenomenon offers the opportunity to selectively heat the catalyst particles to temperatures higher than the matrix. Selective heating can result in greater control over chemical reactions and possibly high selectivity for desirable products. Increased selectivity in microwave-enhanced chemical catalysis has been reported, but the causes are unclear. Because of the difficulty of measuring temperatures of nanometer-sized particles, no direct verification of selective heating has yet been achieved. This project will employ theoretical modeling and a novel experimental technique based on neutron absorption to determine whether catalyst particles are susceptible to selective heating by microwaves. Temperature measurement of nanometer-sized particles cannot be done by conventional techniques. Neutron resonance radiography will be used to resolve the temperatures of catalyst particle and support. The success of this method could open a new avenue for developing catalytic reactions.