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Modeling and scaling processes to generate high-pressure hydrogen (H2) from ammonia

Problem statement

The increasing world energy demand accelerates the depletion of fossil fuels, which consequently boosts the research and development of alternative and viable energy sources. Ammonia (NH3) is a dense, carbon-free energy and hydrogen vector. It can provide on-site hydrogen via catalytic decomposition or cracking.

Our work covers the fundamentals of the microkinetics (using benchmark catalysts such as Ru-based and cheaper, novel alternatives such as Co-Ba-Ce-based) to the reactor modeling.

We use DFT-guided and microkinetic modeling to help understand the rates and catalyst performance. Whereas the reactor modeling from the laboratory scale to the industrial-scale mandates considering the heat-mass transfer effects for efficient implementation of the process.

Goals

  • Develop a microkinetic modeling framework to analyze the catalyst performance and the effect of the role of promoters
  • Dimensionless number analysis to transcend the scale of operation and scale up
  • Using reactive computational fluid dynamics and process modeling: model and simulate an ammonia cracker unit at different scales, including a repurposed steam reformer
  • Model and simulate different reactor configurations, such as packed bed reactors with and without membranes
AMD

Related People

Gontzal Lezcano
Juan David Trueba
Natalia Realpe
Shekhar R. Kulkarni

Related Publications

Elucidating the rate-determining step of ammonia decomposition on Ru-based catalysts using ab initio-grounded microkinetic modeling

by Kulkarni, Realpe, Yerrayya, Velisoju, Sayas, Morlanes, Cerrillo, Katikaneni, Paglieri, Solami, Gascon, Castaño
Catal. Sci. Technol. Year: 2023 DOI: https://doi.org/10.1039/D3CY00055A

Abstract

Decarbonizing the current energy system requires a shift toward renewable energy sources, among which ammonia is a remarkable hydrogen carrier. However, developing an efficient process for the catalytic decomposition of ammonia is still required. Here, we propose a combined modeling–experimental approach to elucidate the rate-determining step in ammonia decomposition on Ru-based catalysts. We characterize and test two supported Ru and Ru–K catalysts in the reaction. We develop several microkinetic models based on ab initio calculations considering different rate-determining steps and validate them with the results of packed bed experiments. For the method validation, we develop a fitting strategy based on modifying the lowest number of parameters from those initially obtained theoretically. A good agreement between the simulated and measured experimental ammonia conversions is obtained, thus widening our understanding of this critical hydrogen production process. The approach presented here allows distinguishing the rate-determining step accurately, and it could be applied to other catalytic systems used in ammonia decomposition to avoid over-relying on empirical models.

Keywords

AMD MKM