Hawkins Alexander P, Edmeades Amy E, Hutchison Christopher D M, Towrie Michael, Howe Russell F, Greetham Gregory M, Donaldson Paul M
Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory Didcot Oxon OX11 0QX UK
Department of Chemistry, University of Aberdeen Aberdeen AB24 3UE UK.
Chem Sci. 2024 Feb 7;15(10):3453-3465. doi: 10.1039/d3sc06128k. eCollection 2024 Mar 6.
Combining pulsed laser heating and time-resolved infrared (TR-IR) absorption spectroscopy provides a means of initiating and studying thermally activated chemical reactions and diffusion processes in heterogeneous catalysts on timescales from nanoseconds to seconds. To this end, we investigated single pulse and burst laser heating in zeolite catalysts under realistic conditions using TR-IR spectroscopy. 1 ns, 70 μJ, 2.8 μm laser pulses from a Nd:YAG-pumped optical parametric oscillator were observed to induce temperature-jumps (T-jumps) in zeolite pellets in nanoseconds, with the sample cooling over 1-3 ms. By adopting a tightly focused beam geometry, T-jumps as large as 145 °C from the starting temperature were achieved, demonstrated through comparison of the TR-IR spectra with temperature dependent IR absorption spectra and three dimensional heat transfer modelling using realistic experimental parameters. The simulations provide a detailed understanding of the temperature distribution within the sample and its evolution over the cooling period, which we observe to be bi-exponential. These results provide foundations for determining the magnitude of a T-jump in a catalyst/adsorbate system from its absorption spectrum and physical properties, and for applying T-jump TR-IR spectroscopy to the study of reactive chemistry in heterogeneous catalysts.
将脉冲激光加热与时间分辨红外（TR-IR）吸收光谱相结合，提供了一种在从纳秒到秒的时间尺度上引发和研究多相催化剂中热活化化学反应及扩散过程的方法。为此，我们使用TR-IR光谱在实际条件下研究了沸石催化剂中的单脉冲和脉冲串激光加热。观察到来自Nd:YAG泵浦光学参量振荡器的1 ns、70 μJ、2.8 μm激光脉冲在纳秒内可在沸石颗粒中引起温度跃升（T-jumps），样品在1-3 ms内冷却。通过采用紧密聚焦的光束几何结构，通过将TR-IR光谱与温度相关的红外吸收光谱进行比较以及使用实际实验参数进行三维传热建模，证明从起始温度可达145 °C的T-jumps。模拟提供了对样品内温度分布及其在冷却期间演变的详细理解，我们观察到其为双指数形式。这些结果为根据催化剂/吸附质系统的吸收光谱和物理性质确定T-jump的大小，以及将T-jump TR-IR光谱应用于多相催化剂中的反应化学研究奠定了基础。
