Tunable Syn-gas ratio via bireforming over coke-resistant Ni/Mo2C catalyst

Abstract

This study demonstrates the ability of Ni/Mo 2 C to catalyze the Methane Bireforming Reaction (combined Dry Methane Reforming Reaction, CH 4 + CO 2  2H 2 + 2CO, and Steam Methane Reforming Reaction, CH 4 + H 2 O  3H 2 + CO). By varying the ratio of CO 2 :H 2 O, the resulting H 2 :CO ratio could be tuned from 0.91 to 3.0, covering a wide range of Syn Gas (H 2 + CO) ratios relevant to various hydrocarbon syntheses. We also document the unusual deactivation behavior of Ni/Mo 2 C in this system. The catalytic activity would change from very high (greater than 50% conversion) to very low (less than 10% conversion) within 10 minutes. Despite running under conditions typically favorable for coking with a Ni catalyst (high temperature, 950°C, and excess methane), XRD, TGA, TEM, SEM, and EDX results clearly show no evidence of coking during the reaction or after deactivation. In addition, the changes to the Ni/Mo 2 C catalyst seen after deactivation (oxidation of Mo 2 C to MoO 2 , Ni-phase changes, and catalyst morphology changes) could not be seen in the catalyst subjected to reaction conditions that were halted before deactivation could occur. This suggests a sudden, rapid deactivation "event" occurs in this catalytic system as opposed to gradual catalyst deactivation, a behavior more typically seen with catalysts.

Theoretical Insights of Ni2P (0001) Surface toward Its Potential Applicability in CO2 Conversion via Dry Reforming of Methane

“…In recent years, interstitial compounds of metal carbide, nitride, and phosphides have received attention for catalyst development . Among these interstitial compounds for DRM, predominant attention has been drawn to Mo-based carbide, nitride, and phosphide catalysts. − Especially, extensive studies on Mo 2 C have shown that this compound has similar activities compared with noble metals (Pd, Pt) at slightly elevated pressures (2 bar) in DRM. − However, for single-metal carbides, high reaction pressures are required to achieve good activity, as the catalyst deactivates at low pressures because of oxidation by CO 2 to form ineffective oxides. − Recently, Fu et al showed that bimetallic Ni- and Co-doped molybdenum nitride exhibited high catalytic activity and are resistant to oxidation at atmospheric pressure . Similarly, a study of DRM with molybdenum phosphide (MoP) catalyst showcased high coking and oxidation resistance with better stability compared with Ni/Mo 2 C catalyst .…”

A comprehensive review on improving the production of rich-hydrogen via combined steam and CO2 reforming of methane over Ni-based catalysts

“…Brush and co-workers explored the performance of Ni/Mo2C for bi-reforming reaction with CH4 and CO2 conversion of 70.5% and 99.8% respectively. They also observed no signs of coking despite conducting the reaction with excessive methane at high temperature [57].…”

Advances in catalytic conversion of methane and carbon dioxide to highly valuable products

“…Furthermore, the variation of CO 2 /H 2 O ratio can tune the produced H 2 /CO ratio from 0.91 to 3.0, covering a wide range of syngas composition for various downstream hydrocarbon synthesis. So far, efforts for the bireforming have been mainly focused on Ni‐based catalysts …”