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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

Unraveling the promoter role of Ba in Co–Ce catalysts for ammonia decomposition using microkinetic modeling

by Lezcano, Realpe, Kulkarni, Sayas, Cerrillo, Morlanes, Mohamed, Velisoju, Aldilajan, Katikaneni, Rakib, Solami, Gascon, Castaño
Chem. Eng. J. Year: 2023 DOI: https://doi.org/10.1016/j.cej.2023.144623

Abstract

Ammonia decomposition is an attractive process for decarbonized hydrogen production. Alkalis are known to promote the reaction, which is especially important to enable non-noble metal catalysts to achieve similar performances to the benchmark Ru catalyst. Herein, we evaluate the kinetic contribution of Ba as a promoter in Co–Ce catalysts, using a microkinetic approach to investigate the influence of the promoter on the elementary steps of ammonia decomposition. For this purpose, we performed experiments over a wide range of conditions with two Co–Ce catalysts, with and without Ba. The results were used to fit microkinetic models with enthalpy–entropy constraints for parameters such as prefactors, activation energies, and sticking coefficients. Based on the differences in these parameters, we compared surface coverages and partial equilibrium indices to show how Ba enhances the rate of N2 desorption, one of the two kinetically relevant steps, along with the NH2 dehydrogenation.

Keywords

AMD MKM