Haneishi Naoto, Tsubaki Shuntaro, Abe Eriko, Maitani Masato M, Suzuki Ei-Ichi, Fujii Satoshi, Fukushima Jun, Takizawa Hirotsugu, Wada Yuji
Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1 E4-3 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan.
Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8904, Japan.
Sci Rep. 2019 Jan 18;9(1):222. doi: 10.1038/s41598-018-35988-y.
The formation of local high temperature regions, or so-called "hot spots", in heterogeneous reaction systems has been suggested as a critical factor in the enhancement of chemical reactions using microwave heating. In this paper, we report the generation of local high temperature regions between catalyst particles under microwave heating. First, we demonstrated that reaction rate of the dehydrogenation of 2-propanol over a magnetite catalyst was enhanced 17- (250 °C) to 38- (200 °C) fold when heated with microwave irradiation rather than an electrical furnace. Subsequently, the existence of microwave-generated specific local heating was demonstrated using a coupled simulation of the electromagnetic fields and heat transfer as well as in situ emission spectroscopy. Specific high-temperature regions were generated at the vicinal contact points of the catalyst particles due to the concentrated microwave electric field. We also directly observed local high temperature regions at the contact points of the particles during microwave heating of a model silicon carbide spherical material using in situ emission spectroscopy. We conclude that the generation of local heating at the contact points between the catalyst particles is a key factor for enhancing fixed-bed flow reactions under microwave irradiation.
在非均相反应体系中形成局部高温区域，即所谓的“热点”，被认为是利用微波加热增强化学反应的关键因素。在本文中，我们报道了在微波加热下催化剂颗粒之间局部高温区域的产生。首先，我们证明，在用微波辐射而非电炉加热时，磁铁矿催化剂上2-丙醇脱氢反应的速率提高了17倍（250℃时）至38倍（200℃时）。随后，通过电磁场与热传递的耦合模拟以及原位发射光谱法，证明了微波产生的特定局部加热的存在。由于微波电场集中，在催化剂颗粒的相邻接触点产生了特定的高温区域。我们还使用原位发射光谱法，在对碳化硅球形模型材料进行微波加热期间，直接观察到了颗粒接触点处的局部高温区域。我们得出结论，催化剂颗粒接触点处局部加热的产生是增强微波辐射下固定床流动反应的关键因素。
