Abstract
The combination of catalytic decomposition of ammonia and in situ separation of hydrogen holds great promise for the use of ammonia as a clean energy carrier. However, finding the optimal catalyst – membrane pair and operation conditions have proved challenging. Here, we demonstrate that cobalt-based catalysts for ammonia decomposition can be efficiently used together with a Pd-Au based membrane to produce high purity hydrogen at elevated pressure. Compared to a conventional packed bed reactor, the membrane reactor offers several operational advantages that result in energetic and economic benefits. The robustness and durability of the combined system has been demonstrated for>1000 h on stream, yielding a very pure hydrogen stream (>99.97 % H2) and recovery (>90 %). When considering the required hydrogen compression for storage/utilization and environmental issues, the combined system offers the additional advantage of production of hydrogen at moderate pressures along with full ammonia conversion. Altogether, our results demonstrate the possibility of deploying high pressure (350 bar) hydrogen generators from ammonia with H2 efficiencies of circa 75% without any external energy input and/or derived CO2 emissions.
Highlights
Over the last decades, the term ‘hydrogen economy’ has gained increasing significance [1–3 4,5]
We demonstrate the industrial potential of the system by running the membrane reactor for over 1000 h
To elucidate the benefits of incorporating a H2-selective membrane to a packed-bed catalytic reactor (PBCR), the catalytic activity was firstly evaluated in the membrane module with the permeate stream opened (PBCMR) and closed (PBCR)
Summary
The term ‘hydrogen economy’ has gained increasing significance [1–3 4,5]. Next to thermodynamic limitations, the considerable endothermicity of the reaction,[6] the inhibitory effect of the produced hydrogen,[64] and the high purity H2 required for most applications (higher than 99.97% [22]), they all point at the in situ removal of hydrogen as the most feasible strategy to efficiently decompose ammonia.[65,66,67,68] the combination of membranes and catalytic ammonia decomposition allows to separate high purity H2 in situ. We demonstrate the industrial potential of the system by running the membrane reactor for over 1000 h
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