(199c) Light Alkanes Transformation through Ammonia Reforming over Intermetallic Catalyst

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 accounts for more than 90 % of the H₂ supply, which, however, produces stoichiometric amounts of CO and CO₂ from hydrocarbons. Consequently, additional water-gas-shift reactors and a methanation reactor are required to obtain CO_x-free H₂. Here, we show that CO_x-free H₂ can be produced from light alkane ammonia reforming (AmmoReform) (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.

We show that a Ni₃Ga₁ intermetallic compound (IMC) catalyst is highly efficient for the proposed AmmoReform, realizing efficient conversion of C₁−C₃ alkanes at 575− 750 °C. At 650 °C and an alkane/ammonia ratio of 1/2, ethane and propane conversion of ∼20% and methane conversion of 13% were obtained (with nearly 100% HCN selectivity for methane and ethane) over the unsupported Ni₃Ga₁ IMC, which also shows high stability due to the absence of coke deposition. Additionally, the structure of the fresh and used Ni₃Ga₁ IMC catalysts has been extensively characterized by in situ/ex situ synchrotron X-ray techniques, including XRD, XAS, and PDF. The characterization results suggested that while C might penetrated the octahedral interstices of the Ni₃Ga₁, such C dissolution shows negligible influence on the stability of the Ni₃Ga₁ IMC.

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.