Plasma-Catalytic Ammonia Reforming of Methane over Cu-Based Catalysts for the Production of HCN and H₂ at Reduced Temperature

Abstract

Industrial production of HCN from NH 3 and CH 4 not only uses precious Pt or Pt−Rh catalysts but also requires extremely high temperatures (∼1600 K). From an energetic, operational, and safety perspective, a drastic decrease in temperature is highly desirable. Here, we report ammonia reforming of methane for the production of HCN and H 2 at 673 K by the combination of CH 4 /NH 3 plasma and a supported Cu/silicalite-1 catalyst. 30% CH 4 conversion has been achieved with 79% HCN selectivity. Catalyst characterization and plasma diagnostics reveal that the excellent reaction performance is attributed to metallic Cu active sites. In addition, we propose a possible reaction pathway, viz. E-R reactions with N, NH, NH 2 , and CH radicals produced in the plasma, for the production of HCN, based on density functional theory calculations. Importantly, the Cu/silicalite-1 catalyst costs less than 5% of the commercial Pt mesh catalyst.

Low-Temperature Activation of Methane with Nitric Oxide and Formation of Hydrogen Cyanide over an Alumina-Supported Platinum Catalyst

“…Both industrial systems operate at temperatures above 1000 °C and generate HCN from CH 4 and ammonia either with or without oxygen . Recently, low-temperature synthesis of HCN from CH 4 and NH 3 using nonthermal plasma and supported metal catalysts was reported. , In this process, CH 4 and NH 3 are activated by the plasma, resulting in the formation of various CH x and NH x species followed by a C–N coupling reaction. The proposed mechanism for this reaction is based on that occurring during the high-temperature BMA process.…”

“…29 Recently, lowtemperature synthesis of HCN from CH 4 and NH 3 using nonthermal plasma and supported metal catalysts was reported. 30,31 In this process, CH 4 species followed by a C−N coupling reaction. The proposed mechanism for this reaction is based on that occurring during the high-temperature BMA process.…”

Methane to Methanol through Heterogeneous Catalysis and Plasma Catalysis

“…Based on the mechanism of plasma catalysis, the adsorption probability is essential for all surfacemediated reaction mechanisms, namely the Langmuir-Hinshelwood (L-H), Eley-Rideal (E-R) and Mars-van Krevelen (MvK) mechanisms [110]. Recent work on plasma catalysis for HCN production by CH 4 /NH 3 NTP corroborated well with the barrierless Eley-Rideak (E-R) reactions between radicals generated in plasma and adsorbed species over the Cu surface, indicated by DFT calculation [156]. As for DOMTM, it is believed that E-R and L-H mechanism may occur in the case of plasma-catalysis on catalyst surfaces, whereas the L-H mechanism dominates in thermal catalytic reactions [118].…”

Particle Size Effect on Hydrogen Cyanide Synthesis with CH₄ and NO over an Alumina-supported Platinum Catalyst

“…Especially, it is an important industrial intermediate used in many manufacturing processes such as nylon production. In fact, the production of HCN has been increasing with population growth, and the current annual production volume is more than 50 times than that of one in 1956 8), 9) . HCN is mainly produced from methane and ammonia by the Andrussow process and BMA (Blausäure aus Methan und Ammoniak) process requiring high temperature above 1000 °C10)-12) .…”

“…HCN is mainly produced from methane and ammonia by the Andrussow process and BMA (Blausäure aus Methan und Ammoniak) process requiring high temperature above 1000 °C10)-12) . Also, recent studies have reported plasma catalysis with supported Pt or Cu catalysts at comparably lower temperature (400 °C) for HCN synthesis from methane and ammonia 8), 9) . Although low-temperature operation was achieved, it still needs high plasma energy for chemical reaction.…”