Ammonia decomposition catalysis using lithium–calcium imide

Abstract

Lithium-calcium imide is explored as a catalyst for the decomposition of ammonia. It shows the highest ammonia decomposition activity yet reported for a pure light metal amide or imide, comparable to lithium imide-amide at high temperature, with superior conversion observed at lower temperatures. Importantly, the post-reaction mass recovery of lithium-calcium imide is almost complete, indicating that it may be easier to contain than the other amide-imide catalysts reported to date. The basis of this improved recovery is that the catalyst is, at least partially, solid across the temperature range studied under ammonia flow. However, lithium-calcium imide itself is only stable at low and high temperatures under ammonia, with in situ powder diffraction showing the decomposition of the catalyst to lithium amide-imide and calcium imide at intermediate temperatures of 200-460 °C.

Demonstrating hydrogen production from ammonia using lithium imide – Powering a small proton exchange membrane fuel cell

“…Light metal amides and imides have been identified [3,4,5] to be effective at decomposing ammonia into its constituents, hydrogen and nitrogen. Here, we show that this catalytic reaction can be harnessed within a bench-top demonstrator which produced 40 W from a PEM fuel cell.…”

“…We have recently shown [3,4,5] that light metal imides and amides define a new class of catalyst for the effective and efficient decomposition of NH 3 into H 2 and N 2 (equation 1), and that this represents a low-cost approach to on-demand hydrogen production. Δ H = 46 kJ mol -1 (1) Thus integrating an ammonia decomposition reactor based on a light metal imide-amide catalyst into a small-scale power generation system provides an opportunity to illustrate and assess the practicality of this innovative hydrogen production method and to address, in part, the concerns of Thomas and Parks [2].…”

Bulk phase behavior of lithium imide–metal nitride ammonia decomposition catalysts

“…Time-of-flight neutron powder diffraction data of the two samples were collected using the POLARIS diffractometer 14 at the ISIS Pulsed Neutron and Muon Facility, United Kingdom. The experimental setup for these experiments was very similar to that described in previous reports, 7,8 with a detailed description given in the ESI. ‡ Briefly, the powder sample was loaded into a custom-designed stainless steel 'flow over' cell, which itself was housed within a furnace mounted into the diffractometer.…”

“…Since initial reports on the promising performance of sodium amide (NaNH 2 ) as an alternative catalyst to traditional transition metal systems, 6 lithium amide-imide (LiNH 2 -Li 2 NH) has emerged as the most important metal amide/imide ammonia decomposition catalyst, having shown high activity on its own 7 and as part of a mixed metal imide. 8 In both these cases the reported high-temperature ammonia decomposition activity was superior to supported ruthenium and nickel catalysts.…”

“…12 In this study, we use in situ neutron powder diffraction to probe the identity and structural character of two of the most active of these composite catalysts: lithium-imide/ manganese nitride and lithium-imide/iron nitride. These experiments represent a characterisation of the bulk behaviour of these catalyst composites, which is of elevated significance in metal amide/imide systems due to the demonstrated bulk interaction of these catalysts with ammonia, 7,8,12,13 rather than a surfaceconfined reaction. However, it should be clear to the reader that the surface and interface behaviour of the materials is not the subject of this work.…”