Red Mud as an Efficient, Stable and Cost-Free Catalyst for COx-Free Hydrogen Production from Ammonia

Abstract

Red mud, one of the mostly produced industrial wastes, was converted into a catalyst with exceptionally high and stable performance for hydrogen production from ammonia. Results showed that iron species produced after reduction of the HCl digested red mud were converted into ε-Fe2N during the induction period of ammonia decomposition reaction at 700 °C. The catalytic performance measurements indicated that the modified red mud catalyst provides a record high hydrogen production rate for a non-noble metal catalyst at this temperature. For instance, stable hydrogen production rates were measured as 72 and 196 mmol H2 min−1 gcat−1 for the corresponding space velocities of 72 000 and 240 000 cm3 NH3 h−1 gcat−1, respectively, at 700 °C. These results offer opportunities to utilize one of the key hazardous industrial wastes as an eco-friendly, efficient, stable, and almost cost-free catalyst for COx-free hydrogen production from ammonia decomposition.

Turning Waste into Value: Potassium‐Promoted Red Mud as an Effective Catalyst for the Hydrogenation of CO2

“…Thereafter, temperature‐programmed reduction (TPR) was carried out on red mud and 2 wt % K‐promoted red mud (Figure S10). Several differences could be observed upon comparing both samples: i) peaks below 120 °C for the K‐promoted sample, which arise from the decomposition of KHCO 3 that starts at 67 °C; ii) peaks in the region of approximately 370–730 °C, which come from the reduction of iron species: hematite (Fe 2 O 3 ) into magnetite (Fe 3 O 4 ) at 420 °C (vs. 450 °C for the promoted sample), broad reduction of magnetite to iron monoxide at 510–720 °C (vs. 530–730 °C for the promoted sample), and reduction to metallic Fe at 750 °C . In accordance with previously reported results, the addition of K shifts the reduction temperature of iron oxide species to higher temperatures .…”

Interactions of [BMIM][BF4] with Metal Oxides and Their Consequences on Stability Limits

“…SEM images were collected by using a Zeiss Ultra Plus (FEG-SEM) scanning electron microscope with an SE detector, as before. 42 Samples were applied on a carbon tape to protect the supports from charging effects. Images were collected at the magnifications of 30 000× and 100 000× with an accelerating voltage (EHT) of 5 kV for γ-Al 2 O 3 and of 1 kV for SiO 2 and MgO.…”

“…SEM images were collected by using a Zeiss Ultra Plus (FEG-SEM) scanning electron microscope with an SE detector, as before . Samples were applied on a carbon tape to protect the supports from charging effects.…”

Nano-structural effects on Hematite (α-Fe2O3) nanoparticle radiofrequency heating

“…As the most stable iron oxide under acidic [1] and ambient conditions [2], hematite (i.e., α-Fe 2 O 3 ) has been heavily studied for a variety of applications including: waste water treatment [2][3][4][5], catalysis [6], gas sensors [2], and electrodes [7]. Although environmentally benign and biocompatible [8,9], bulk hematite is not suitable for radio frequency (RF) magnetic heating applications because it is weakly ferromagnetic at room temperature [10,11] (i.e., M S,bulk ~ 0.3 emu/g [12]).…”