Hydrogenation of Hydrogen Cyanide to Methane and Ammonia by a Metal Catalyst: Insight from First-Principles Calculations

Abstract

The adsorption and hydrogenation behaviors of hydrogen cyanide to methane and ammonia formation by W(111) catalyst were systematically investigated using the density functional theory method. Based on our calculated consequences, it is found that the WHCN­(T,T-μ2-C,N) is calculated to be the most stable conformer, possessing an adsorption energy of −49.8 kcal/mol, among all calculated structures of HCN/W(111) system. To comprehend the electronic property of its interaction between the adsorbate and substrate, we calculated the electron localization functions, local density of states, and Bader charges; our results were consistent and explicable. Reaction paths in all possible mechanisms were explored in detail, involving the hydrogenation on different orientations of each adsorbate and the scission of the carbon–nitrogen bond. Before forming an imine intermediate (H2CNH(a)), two adsorbed hydrogen atoms will sequentially react with the nitrogen and then carbon atoms in the first and second hydrogenation steps, and the corresponding activation barriers are calculated to be 37.4 and 16.3 kcal/mol, respectively. After yielding an imine intermediate (H2CNH(a)), however, the breaking of carbon–nitrogen bond is likely to proceed at this stage with a pertinent barrier height of 27.5 kcal/mol, forming CH2(a) + NH(a). At elevated temperatures, these resulted adsorbates could be desorbed by further consecutive hydrogenations to generate the final products of methane and ammonia. Our findings provide atomistic-level insight into the novel pathway for surface-assisted synthesis of methane and ammonia via facile hydrogenation reaction of HCN.

Post-plasma catalysis: charge effect on product selectivity in conversion of methane and nitrogen plasma to ethylene and ammonia

“…S4a†) which is possibly due to redirection of activated H 2 species (H, H*) to vinyl hydrogenation. It is important to note that HCN may have been hydrogenated to NH 3 and CH 4 in the presence of the heated catalyst 61,62,25 but the NH 3 concentration does not increase in the plasma reaction with Ag–Pd/CeO 2 when compared to the one with CeO 2 . Additionally, no CH 4 was observed in the product gas mixture in all the three sets of plasma reactions indicating 100% conversion of methane.…”

“…If 0.1% HCN could be added to the reaction feed mixture to exactly match the product gas mixture of the plasma reaction, it may have been hydrogenated to ammonia and methane. 64 Since no ammonia and methane were observed in the product gas mixture of this set of reactions, it can be safely assumed that if HCN was added into the feed, it would have remained unconverted during this reaction possibly due to the low reaction temperature.…”

Multi-Catalytic Route for the Synthesis of (S)-Tembamide

“…Based on our previous studies [36], the enzymatic cascade leading to (S)-3 afforded a crude solution containing approximately 80-85 mM (S)-3, 10-15 mM 2, 5-10 mM 1, 180 mM phenyl benzoate, 40 mM benzoic acid and a maximum of 550 mM HCN. Given the high concentration of HCN and its susceptibility to hydrogenation [62,63], its effect on the hydrogenation of 3 was evaluated. For optimal selectivity, a concentration of 3 in the range of 20 mM was selected, for which the biocatalytic crude reaction mixture would undergo a 4-fold dilution prior to the reduction step.…”

First-Principles Insight into the Mechanistic Study of Electrochemical Cyanide Reduction Reaction on Post-Transition Metal Based Single-Atom Catalysts Anchored by Phthalocyanine Nanosheets

“…Remarkably, substituting nitrogen with cyanide in reduction reactions could resolve complexities by utilizing the latter’s polar attributes, which enhance reactivity and yield a more efficient process. In addition, the cyanide electroreduction reaction (CNRR) culminates not merely resulting in NH 3 formation, but it leads to the production of CH 4 as well; these substances each play significant roles as vital chemical feedstock and combustible materials . Despite the extensive range of advantages associated with the CNRR, there remains a conspicuous scarcity of scholarly research on the topic. − Our recent computational investigation has indicated that employing 3d transition metals (Sc to Zn) as SACs within a doped organic framework of phthalocyanine can manifest superior catalytic reactivity for the CNRR.…”