(6f) Light Alkanes Transformation through Ammonia-Assisted Reforming

Hydrogen is a clean energy carrier. It is expected to play a pivotal role in a clean, secure, and affordable energy future and is currently enjoying unprecedented political and business momentum worldwide. Currently, steam reforming stands for more than 90 % of H₂ supply, which, however, produces stoichiometric amounts of CO and CO₂ from hydrocarbons. Consequently, it requires additional water-gas-shift reactors and a methanation reactor to obtain CO_x-free H₂. Here, we show that CO_x-free H₂ can be produced from ammonia assisted reforming (ammoreforming) of natural gas liquids (C_nH_2n+2 + nNH₃ = nHCN + (2n + 1) H₂, n = 2 or 3) at the same conditions as the steam reforming. Such a process co-produces HCN, which can be easily separated (through absorption by water) from H₂ and used as value-added chemicals (for polymer synthesis) or for NH₃ recycling through hydrolysis.

The proposed ammoreforming of ethane and propane was realized over the Re-modified HZSM-5 zeolite rather than the traditional Pt-based catalyst for the BMA process (methane ammoreforming). The specific activity of the Re/HZSM-5 catalysts at 650ºC is up to 1 mol_H2/g_Re/min (or 180 min^-1) during ethane ammoreforming, which is significantly higher than the steam reforming of ethane or propane and ammonia decomposition for H₂ production. Additionally, the Re/HZSM-5 catalyst is highly coke-resistant for the ethane and propane ammoreforming, no significant catalyst deactivation was observed with time-on-stream up to 20 h. Characterization of the fresh and used catalysts by X-ray absorption and Raman spectroscopies suggested that the isolated ReO_x site grafted by AlO₄^‒ tetrahedral in the zeolite framework is responsible for the outstanding catalytic performance.

The present catalytic system demonstrated superior performance to the conventional steam reforming (for H₂) and the commercial BMA and Shawinigan processes (for HCN), so appears to have considerable potential for industry application.