(326d) Techno-Economic Analysis of Direct Methane Aromatization for Natural Gas Upgrading at Isolated Sites

Inexpensive sources of natural gas have led to a boom in development of technologies taking advantage of C1 chemistry; however, a significant number of potential natural gas sources are stranded and lack the infrastructure for economically-feasible transportation. The resulting gas, which is normally flared, can, in theory, be recovered at the well-site, purified, and then processed to a product which is easier to transport. Gas-to-liquid (GTL) processes exist which can convert the feed to liquid products which can be more easily transported, although there are process constraints due to the need for deployment in remote locations, and several are being commercialized.¹ One such process, direct methane aromatization (DMA), produces significant amounts of benzene, a valuable commodity chemical, and hydrogen. The benzene can be purified on-site and then transported by truck; the hydrogen can be dealt with on-site as well by either transforming it to another transportable chemical, such as ammonia or cyclohexane, or using it to provide heating or electricity.

Previous economic studies of DMA have been reported which either invoke unrealistic assumptions in the process model,^{2, 3} do not consider use of the gaseous hydrogen,^{2, 3} or do not consider the limitations imposed on the process due to remote deployment.⁴ With these issues in mind, a DMA mini-plant processing 1.0 MMSCFD of natural gas was designed with currently available technology to provide a platform for the investigation of process intensified alternatives. The reactor section of the plant uses a pre-carburized DMA catalyst developed at Texas Tech.⁵ The unit was investigated for economic feasibility and sustainability. In particular, the analysis identifies four particular areas which can benefit from intensification: aromatics yield (i.e. one-pass conversion), coke selectivity, hydrogen recovery, and separation and purification of the aromatic products. Although intensified reactor technology for the DMA process is already being investigated for improving the yield with^{6, 7} and without integrated hydrogen recovery^{8, 9}, the process model framework should provide opportunities for investigating additional intensification technologies, particularly in separations.

1. H. Fleisch. [White Paper], World Bank-Global Gas Flaring Reduction Partnership, 2015.
2. Pérez-Uresti, S.I. et al., Processes, 2017, 5, 33.
3. Camilo Corredor, E., P. Chitta, and M. D. Deo. Fuel Pro. Tech., 2019, 183, 55 – 61.
4. Huang, K. et al., Joule, 2018, 2, 349 – 365.
5. Rahman, M., A. Sridhar, and S.J. Khatib. Cat. A Gen., 2018, 558, 67 – 80.
6. Kee, B. et al., Eng. Chem. Res., 2017, 56, 3551 – 3559.
7. Morejundo, S.H. et al., Science, 2016, 353(6299), 563 – 566.
8. Brady, C., B. Murphy, and B. Xu. ACS Catal., 2017, 7(6), 3924 – 3928.
9. Cao, Z. et al., Chem. Int. Ed., 2013, 52, 13794 – 13797.