Syngas Production via CO<sub>2</sub>-Mediated Melamine Pyrolysis
Seong-Heon Cho, Jonghyun Park, Sungyup Jung, Yiu Fai Tsang, Doyeon Lee, Eilhann E. Kwon
Abstract
Melamine is an extensively used fire retardant in various commercial products. Along with its applications, awareness about its toxicity also increases and the accelerated rate of waste generation has become a concern. This study proposes a systematic approach for the conversion of melamine into syngas. For enhanced sustainability of this process, CO 2 was used as the reactive medium during pyrolysis. Before pyrolysis, melamine was examined by using thermogravimetric analysis and pyrolysis-gas chromatography. Subsequent melamine pyrolysis yielded only ammonia and condensed pyrolysates. A double-stage pyrolysis setup was used to optimize the thermal cracking of melamine. Under CO 2 conditions, CO was generated although melamine lacks an inherent oxygen source. The CO evolution under the CO 2 condition is attributed to the homogeneous interaction between CO 2 and volatile pyrolysates. However, the slow kinetics of this homogeneous reaction hinders its complete activation. To expedite the homogeneous reaction, a Ni catalyst was introduced. The concentration of CO from catalytic pyrolysis under the CO 2 condition enhanced 109 times (35 mol %) compared to double-stage pyrolysis setup. Furthermore, melamine completely transformed into gaseous pyrolysates after catalytic pyrolysis under CO 2 conditions. All experimental observations highlighted that melamine pyrolysis under CO 2 and a Ni catalyst could be a useful energy and chemical recovery approach.