Evaluation of catalysts supported on carbon nanotubes and kinetic modeling of the process for the Water-Gas Shift (WGS) reaction: macro and microkinetic approaches and use of machine learning techniques for catalyst selection.

Author(s)

Fábio Machado Cavalcanti

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2023-12-20

Examining board members

Rita Maria de Brito Alves; Robson Pablo Sobradiel Peguin; José Carlos Costa da Silva Pinto; Joris Thybaut; Fabio Souza Toniolo

• Advisor: Reinaldo Giudici; Rita Maria de Brito Alves

Abstract

The Water-Gas Shift (WGS) reaction is one of the most important routes for hydrogen production. It has received great importance due to the use of H2 in the main chemical industries and main clean energy source in the future. Although there are already wellestablished industrial catalysts for the WGS reaction, several new ones have been developed for improving process performance and stability with noble metals at nanoscale supported on oxides. To assist with these numerous catalysts, Artificial Neural Networks (ANNs) were used to build a model based on catalytic data from the literature. In this context, a novel catalyst, Co/CeO2-Sr nanoparticles supported on Multi-Walled Carbon Nanotubes (MWCNTs), was developed. The use of Co resulted in a high activity and sulfur-tolerance, while CeO2 has a high oxygen storage capacity as a result of its reducibility, and Sr acts as a promoter. The use of carbon nanotubes as catalyst support has shown to be advantageous due to their high surface area, conductive properties, and the low availability of some oxides. The catalytic activity was evaluated in an industrially relevant temperature range under atmospheric pressure, presenting better performances at higher temperatures (300-450oC), and achieving near-equilibrium CO conversion. Furthermore, kinetic data was collected by varying the species concentrations. Conventional power-law, mechanistic ratedetermining step, and microkinetic models were adjusted to them, for discriminating the best formulation to fully understand the chemical reaction. The redox mechanism was identified as most suitable and allows explaining the catalyst role during the WGS reaction, providing oxidation and reduction cycles from the availability and mobility of O* species on its surface. All this work is a robust consultancy material to assist in future catalyst design and optimization for industrial reactor projects. (AU)

• FAPESP's process: 17/11940-5 - Evaluation of catalysts supported on carbon nanotubes and kinetic modeling of the process for the Water-Gas-Shift reaction (WGS)
• Grantee: Fábio Machado Cavalcanti
• Support Opportunities: Scholarships in Brazil - Doctorate