Methane Partial Oxidation Over Multifunctional 2-D Materials
Project Number
FE0031878
Last Reviewed Dated
Goal
The goal of this research is to design, synthesize, and evaluate highly selective, active, and stable multifunctional catalysts for the low temperature (< 500 Kelvin (K)) partial oxidation of methane to methanol (MTM) with molecular oxygen.
Performer(s)
University of South Carolina, Columbia, SC 29208
Collaborators
University of Colorado, Boulder, CO 80309
Pajarito Powder, Albuquerque, NM 87109
Background
This project will investigate single atom catalysts embedded and stabilized in two-dimensional materials such as graphene (GR) and "supported" on Group VIII and IB transition metals such as nickel.
Impact
Methane, the primary component of natural gas, is a source of energy and economic growth as well as an environmental concern. Recent developments in horizontal drilling and enhanced extraction methods have resulted in production of an estimated 62.4 trillion m3 of ‘stranded’, or uneconomic, natural gas. Uneconomical natural gas is often flared or vented at remote oil production sites. Leaked, flared, and/or vented gas represents a "lost opportunity" and this research project aims to maximize the value of the resource.
Accomplishments (most recent listed first)
Based on computationally predictions, Rh-GR/Ni and Pt-GR/Ni catalysts were synthesized and evaluated in the high-pressure reactor. Steady state methanol production at 450ºC was observed when flowing CH4 and O2 at higher flow rate (total flow rate equal or higher than 40mL/min). The steady state methanol selectivity is above 35%.
A detailed mechanistic study for the MTM over Rh-GR/Ni, Pt-GR/Ni, and Ir-GR/Ni catalyst models was performed with the aim of identifying other catalysts beyond Rh-GR/Ni(111) that display high methanol selectivity and, importantly, also a high activity at even lower temperatures. The results indicate that the Pt-GR/Ni and Ir-GR/Ni catalysts are also similarly active and selective for MTM compared to the Rh-GR/Ni catalyst. While Pt-GR catalyst can also be selective for MTM conversion, it exhibits two orders of magnitude lower turnover frequencies compared to the Pt-GR/Ni catalyst at 300 ºC.
A high-pressure reactor capable of conducting catalyst evaluations for the high-pressure methane-to-methanol reaction was constructed. The reactor is equipped with a furnace and temperature control capabilities up to > 400ºC. Both electronic pressure gauges and standard pressure gauges were connected to various points in the reactor to enable monitoring of the pressure upstream and downstream of the catalyst bed. A back pressure regulator was installed in the reactor system to control the reactor pressure. Four mass flow controllers were included to control the flow of O2, CH4, and He for the reaction, as well as H2 for catalyst pretreatment. A new in-line gas chromatography system with both flame ionization and thermal conductivity detectors was brought online to measure reactant conversions and product yields. Check valves and particle filters were also built in the reactor system to ensure safety and avoid contamination of the gas chromatograph. The online gas chromatography system is now operational and has been calibrated for the main reactant and product gases of interest (methane, oxygen, methanol, carbon monoxide, carbon dioxide, ethane, etc.). The gas line between the reactor and online gas chromatograph was designed to be heated by to avoid condensation of compounds with high boiling points downstream of the reactor.
Current Status
We are currently in the process of optimizing catalyst composition and reaction temperature. Synthesis of the catalyst continues to be challenging, in the sense that it is desired to have a large fraction of active sites that consist of single metal atoms embedded in a graphene layer and deposited on a Ni surface (versus large metal atom clusters or metal atoms embedded in graphene but not in contact with a Ni surface). Thus, there is also continued effort in simplifying the catalyst system without sacrificing activity and selectivity.
