An efficient process is reported for preparing a state-of-the-art Fe-ferrierite catalyst for N₂O decomposition under industrial tail-gas conditions. In the synthesis procedure, we evaluate the very demanding constraints for scale-up; i.e. large reactor volumes are typically needed, and long processing times and considerable amounts of wastewater are generated. The proposed synthesis minimizes the amount of water used, and therefore, the amount of produced wastewater is minimal; in this approach there is no liquid residual water stream that would need intensive processing. This has remarkable benefits in terms of process design, since the volume of equipment is reduced and the energy-intensive filtration is eliminated. This route exemplifies the concept of process intensification, with the ambition to re-engineer an existing process to make the industrial catalyst manufacture more sustainable. The so-obtained catalyst is active, selective, and very stable under tail-gas conditions containing H₂O, NO, and O₂, together with N₂O, keeping a high conversion during 70 h time on stream at 700 K, with a decay of 0.01%/h, while the standard reference catalyst decays at 0.06%/h; hence, it deactivates 6 times more slowly, with ∼5% absolute points of higher conversion. The excellent catalytic performance is preliminarily ascribed to the differential speciation.

A novel route to prepare highly active and stable N₂O decomposition catalysts is presented, based on Fe-exchanged beta zeolite. The procedure consists of liquid phase Fe(III) exchange at low pH. By varying the pH systematically from 3.5 to 0, using nitric acid during each Fe(III)-exchange procedure, the degree of dealumination was controlled, verified by ICP and NMR. Dealumination changes the presence of neighbouring octahedral Al sites of the Fe sites, improving the performance for this reaction. The so-obtained catalysts exhibit a remarkable enhancement in activity, for an optimal pH of 1. Further optimization by increasing the Fe content is possible. The optimal formulation showed good conversion levels, comparable to a benchmark Fe-ferrierite catalyst. The catalyst stability under tail gas conditions containing NO, O₂ and H₂O was excellent, without any appreciable activity decay during 70 h time on stream. Based on characterisation and data analysis from ICP, single pulse excitation NMR, MQ MAS NMR, N₂ physisorption, TPR(H₂) analysis and apparent activation energies, the improved catalytic performance is attributed to an increased concentration of active sites. Temperature programmed reduction experiments reveal significant changes in the Fe(III) reducibility pattern with the presence of two reduction peaks; tentatively attributed to the interaction of the Fe-oxo species with electron withdrawing extraframework AlO₆ species, causing a delayed reduction. A low-temperature peak is attributed to Fe-species exchanged on zeolitic AlO₄ sites, which are partially charged by the presence of the neighbouring extraframework AlO₆ sites. Improved mass transport phenomena due to acid leaching is ruled out. The increased activity is rationalized by an active site model, whose concentration increases by selectively washing out the distorted extraframework AlO₆ species under acidic (optimal) conditions, liberating active Fe species.