Ammonia Synthesis Activity of Alumina-Supported Ruthenium Catalyst Enhanced by Alumina Phase Transformation

Abstract

The increase of alumina calcination temperature from 800 °C to 1300 °C results in the transformation of γ-Al2O3 to α-Al2O3 phase accompanying a decrease of specific surface area and the amount of tetrahedral Al3+ sites. Over Ru–Ba/alumina catalysts, an increase in alumina calcination temperature would broaden the size distribution of Ru particles, enlarge the metal-to-oxide ratio of Ru, decrease the amount of surface hydroxyl groups, as well as lower the temperature for N2 desorption. As a result, the increase of alumina calcination temperature lessens the effect of hydrogen poisoning and decreases the activation energy for ammonia synthesis. The Ru–Ba/Al2O3 catalyst with alumina calcined at 980 °C having both θ-Al2O3 and α-Al2O3 shows ammonia synthesis rate three times higher than that with alumina calcined at 800 °C having a γ-Al2O3 phase.

Photocatalytic water splitting by N-TiO2 on MgO (111) with exceptional quantum efficiencies at elevated temperatures

“…For example, the formed hydrogen if combined with N 2 (from air separation) can be used to produce ammonia which is a highly exothermic reaction. In addition, the hydrogen evolution rate in our LEF-enhanced water- splitting system appears to match well with the ammonia evolution rate 39,40 . Based on our evaluation (see Supplementary Note 2), the heat produced during ammonia synthesis could compensate the energy required for our LEF-enhanced water-splitting system, which gives an exciting possibility to turn the current natural gas-dependent Haber–Bosch process to carbon-free photocatalytic practice for the ammonia synthesis.…”

Highly Effective Ru/BaCeO3 Catalysts on Supports with Strong Basic Sites for Ammonia Synthesis

“…The high percentage of Ru 0 in Ru/BaCeO 3 ‐a indicates a high electron density of Ru species in this catalyst, which is beneficial for the dissociation of N≡N bonds. In addition, the binding energy of Ru 3d 5/2 peaks appears at 279.5 and 280.3 eV for Ru/BaCeO 3 ‐a and Ru/BaCeO 3 ‐b, respectively, which suggests the peak of Ru/BaCeO 3 ‐a shifts to lower values than Ru/BaCeO 3 ‐b, which is also conducive to electron transfer to reverse bond orbitals of N 2 …”

Effect of nitrogen co-doping with ruthenium on the catalytic performance of Ba/Ru–N-MC catalysts for ammonia synthesis

“…6,7 Ruthenium-based catalysts have been intensively studied because they can work under milder conditions than promoted iron catalysts. 8,9 Therefore, extensive efforts have been focused on the development of effective Rubased catalysts. 10,11 Carbon materials, due to its various structures and facile modication, have been intensively investigated as supports for metal-based catalysts.…”