(481f) A Spectro-Kinetic-Hydrodynamic Workflow to Assess Gas-Solid Operando Spectroscopic Cells As Intrinsic Kinetic Reactors
AIChE Annual Meeting
Wednesday, November 16, 2022 - 2:00pm to 2:18pm
We have developed a workflow to analyze the operando spectroscopic cells working with a gas-solid interphase, in the shape of a catalyst disc. These types of reactors are regularly used to examine the catalyst structure, the retained-adsorbed species, and their dynamics using online product analysis and spectroscopic techniques. The information obtained from them has revealed critical to understand the way catalysts work in process conditions. As a case study, we have focused on the methanol-to-hydrocarbon reaction, using a ZSM-5 zeolite catalyst and two spectroscopic cells, one mass spectrometer to analyze the products, and two techniques: FTIR and UV-vis spectroscopies. We propose a framework based on the incremental evaluation of the hydrodynamic-mixing, kinetic, and spectroscopic information: (a) for hydrodynamic-mixing, we performed residence time distributions (RTD) and computational fluid dynamics (CFD) to study the possible occurrence of bypasses or flow uniformities; (b) for the kinetics, we worked with a reference packed bed reactor, develop a kinetic model, and compared the results in different reactors to see which conditions lead to intrinsic kinetic results, in absence of external or internal mass transfer; (c) for the spectroscopic information, we couple all results from the two spectroscopic techniques with their correspondent product analysis to get a rational and holistic model including surface species and deactivation. Our results reveal that these cell reactors approach the behavior of a few mixed flow reactors, they can suffer hydrodynamic maldistribution or severe mass transfer limitations, but when correctly operated, they can provide extremely valuable kinetic and deactivation information. To approach the intrinsic kinetic regime, it is required to work with low partial pressures of reactants, high flow rates, low catalyst loadings (low spacetimes), and differential reactor regimes. The proposed methodology allows us to understand the influence of process parameters and potential design modifications on these instruments.