Moment-Based Analysis of Transient Response Catalytic Studies (TAP Experiment)

Abstract

A new moment-based theoretical approach for the analysis of TAP (temporal analysis of products) pulse-response data is described. The distinguishing feature of this approach is that the variables of the set of ordinary differential equations that comprise the model are moments instead of concentrations. The moments are functions of the reactor axial coordinate, whereas concentrations are functions of space and time. The theoretical framework for the extraction of kinetic parameters using this approach is developed, and is used to determine kinetic parameters for CO oxidation over platinum powder. A new phenomenon, called “TAP equilibrium” is described. This phenomenon is governed by the interplay between reaction and Knudsen diffusion.

TAP studies of Pt–Sn–K/γ-Al2O3 catalyst for propane dehydrogenation

“…This quantity is called the normalized flow and is used in the analysis of pulse response experiments. So, the normalized flow of component i is given by F i /N pA where F i is the exit flow of gas i and N pA is the number of moles of limiting reactant gas A in the inlet pulse [3]. Taking this into account, the propane conversion at a temperature T was obtained from the following mass balance, assuming no propane conversion at 300 • C:…”

“…Quantitative information of the phenomena in the reactor can be extracted from the size and shape of the responses by the use of appropriate mathematical models [1][2][3][4][5][6][7][8]. Kinetic evaluation of TAP experiments is typically based on analytical or numerical solution of partial differential equations describing chemical and diffusion process in the micro-reactor.…”

“…Kinetic evaluation of TAP experiments is typically based on analytical or numerical solution of partial differential equations describing chemical and diffusion process in the micro-reactor. Different methods have been proposed in the literature, including moment analysis [2][3][4], thin-zone model [5,6] and a numerical solution [7]. In a previous study, the first order rate constant for the propane conversion over stable samples (no coke) has been evaluated by moment analysis, the thinzone model and regression analysis of the full pulse response for different catalyst bed lengths and temperatures.…”

Techniques for Fabricating Nanoscale Catalytic Circuits

“…In TAP data analysis, moments have proven to be the most effective and straightforward mathematical language for characterizing the flow time-dependence that is characteristic of TAP pulse response curves [25][26][27][28]35]. Experimentally, the moments are integral characteristics of the observed exit flow time dependencies.…”

Assessment of kinetic modeling procedures of TAP experiments

“…Gleaves and coworkers [28,46,51,52] derived for a number of reactor configurations and typical mechanisms, analytical solutions as well as the expressions for the zeroth and first moments. Expressions for the different moments have also been reported in the case of porous catalyst samples [53,54].…”