Production of Cyanide Using Thermal Plasma: Thermodynamic Analysis and Process-Specific Energy Consumption

Abstract

A plasma process for making cyanide from nitrogen and hydrocarbon (methane and propane) has been successfully demonstrated, which can directly fix atmospheric nitrogen into hydrocarbons. Nitrogen serves as both the plasma gas and the primary reactant. The thermodynamic analysis as well as the experimental outcome indicates that it is feasible to achieve very high conversion of hydrocarbons into cyanide by increasing the partial pressure of nitrogen gas within the reaction mixture, but the high conversion comes at a cost of an increase in total energy consumption and was detrimental to process energy efficiency. Hence, the process was optimized based on specific energy consumption (SEC) instead of conversion. The conversion with respect to nitrogen and hydrocarbon ratio follows thermodynamic prediction. The primary byproducts obtained were hydrogen, acetylene, and soot. The laboratory system was stable and could be run for extended periods, achieving a minimal SEC of approximately 15.5 kW h/kg NaCN.

Plasma‐catalytic synthesis of acrylonitrile from methane and nitrogen

“…Interestingly, the results in Figure 3 are already competitive with the few results that have been reported for thermal plasmas for this reaction. 15,16 The comparison to thermal plasma is encouraging in that nonequilibrium plasmas, which have a lower background gas temperature compared to thermal plasmas and therefore require less bulk gas heating and can offer faster quenching, may ultimately be more energy efficient.…”

“…A system with a larger RF power supply and higher flow rate capacity would be required to test the hypothesis that the specific energy requirement continues to decrease at higher applied powers and higher total flow rates. Interestingly, the results in Figure 3 are already competitive with the few results that have been reported for thermal plasmas for this reaction 15,16 . The comparison to thermal plasma is encouraging in that nonequilibrium plasmas, which have a lower background gas temperature compared to thermal plasmas and therefore require less bulk gas heating and can offer faster quenching, may ultimately be more energy efficient.…”

Plasma-catalytic synthesis of acrylonitrile from methane and nitrogen

“…Interestingly, the results in Figure 3 are already competitive with the few results that have been reported for thermal plasmas for this reaction. 14,15 The comparison to thermal plasma is encouraging in that nonequilibrium plasmas, which have a lower background gas temperature compared to thermal plasmas and therefore require less bulk gas heating, may ultimately be more energy efficient.…”

Recent Advances in Plasma Catalysis

“…Moving further into the utilization of NH 3 , Yi et al present the plasma-catalytic reforming of methane with NH 3 for the production of HCN and H 2 under moderate temperature conditions, when compared to the industrial process . In the same vein, the thermodynamic analysis of such plasma processes to produce cyanide from N 2 and hydrocarbons (such as methane and propane) is reported by Henderson et al Plasma–catalyst combinations are applied to chemical transformations other than the previously mentioned C and N chemistries. For example, Al Qahtani et al coupled DBD with alumina-supported sulfides for low-temperature reduction of sulfur dioxide to elemental sulfur, using hydrogen or methane .…”