Arsac F, Bianchi D, Chovelon J M, Ferronato C, Herrmann J M
Laboratoire d'Application de la Chimie à l'Environnement (LACE), UMR 5634, Université Claude Bernard, Lyon-1, Bat. Raulin, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne-France.
J Phys Chem A. 2006 Mar 30;110(12):4213-22. doi: 10.1021/jp057255p.
The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of the PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factors and activation energies). These kinetic parameters are used to evaluate a priori the catalytic activity (turnover frequency, TOF, in s(-1)) of the solid that is compared to the experimental value. The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The microkinetic study shows that only strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The apparent rate constant (1.4 10(-3) s(-1)) of the Langmuir-Hinshelwood elementary step between IPA(sads) and the active oxygen containing species generated by the UV irradiation provides the TOF of the PCO for IPA/O2 gas mixtures. The kinetic parameters of the elementary steps determined by the experimental microkinetic approach allow us to provide a reasonable simulation of the experimental data (coverages of the adsorbed species and partial pressures of the gases of interest) recorded during a static PCO of IPA(sads) species.
本研究涉及一种实验微观动力学方法，该方法是根据先前开发的程序，在纯锐钛矿型TiO₂固体上对异丙醇（IPA）进行光催化氧化（PCO）生成丙酮。主要通过实验确定IPA光催化氧化可能的动力学模型中每个表面基元步骤的动力学参数：吸附物种的性质和数量以及速率常数（指前因子和活化能）。这些动力学参数用于先验评估该固体的催化活性（周转频率，TOF，单位为s⁻¹），并与实验值进行比较。动力学参数是通过使用傅里叶变换红外光谱仪（FTIR）或质谱仪作为检测器的瞬态实验获得的。微观动力学研究表明，只有强吸附的IPA物种（由于IPA的非解离和解离化学吸附分别产生的两种物种，分别表示为nd - IPA(sads)和d - IPA(sads)）参与了IPA的光催化氧化。IPA(sads)与强吸附的丙酮物种之间存在强烈的竞争化学吸附，在IPA(sads)对表面的高覆盖率下，控制了光催化氧化对丙酮的高选择性。IPA(sads)与紫外线照射产生的活性含氧物种之间的Langmuir - Hinshelwood基元步骤的表观速率常数（1.4×10⁻³ s⁻¹）提供了IPA/O₂气体混合物光催化氧化的TOF。通过实验微观动力学方法确定的基元步骤的动力学参数，使我们能够合理模拟在IPA(sads)物种的静态光催化氧化过程中记录的实验数据（吸附物种的覆盖率和感兴趣气体的分压）。
