Removal of toxic HCN and recovery of H₂-rich syngas via catalytic reforming of product gas from gasification of polyimide over Ni/Mg/Al catalysts

The recycling of N-containing plastics by pyrolysis or steam-reforming is typically complicated by the generation of toxic HCN. In this study, polyimide, as an example of an N-containing plastic, was gasified and the product gas was reformed over various Ni/Mg/Al catalysts. Effects of catalyst properties, steam, and temperature on the HCN removal and H₂-rich syngas production were investigated. More than 99% HCN removal (compared with pyrolytic conditions) and ∼3000 mL g⁻¹of H₂-rich syngas with a H₂/CO ratio of 10.4 were simultaneously achieved at 800 °C in the presence of a reduced-Ni_1.0Mg_3.6Al_4.8catalyst, then HCN was mainly converted into N₂. On the other hand, non-reduced same catalyst enhanced hydrolysis of HCN into NH₃with more than 98% HCN removal at 800 °C, which is also a beneficial finding to recover useful NH₃from HCN, directly. Therefore, the present work achieved that the improvement of the H₂-rich syngas yield and quality, and conversion of toxic HCN into non-toxic N₂or useful NH₃using the same catalyst, simultaneously.