(214a) Process Design and Economic Evaluation of Aromatics Manufacturing By Using an Oxidative Coupling-Dehydroaromatization Reactor

Natural gas is an important fossil fuel resource, and its global demand is projected to grow significantly, driven in part by the shale gas revolution in the United States. This revolution has unlocked access to vast reserves of shale gas, positioning natural gas as an abundant, versatile, and economically attractive feedstock when compared to conventional fuels [1,2,3]. In addition to cost competitiveness, natural gas offers the advantage of lower carbon emissions, making it a promising candidate for the sustainable production of value-added chemicals. Over the past decades, various technologies have been developed for the conversion of methane (CH₄)—the primary component of natural gas—into higher-value products. These conversion pathways can be broadly categorized into direct and indirect routes. While indirect routes typically involve the reforming of methane into synthesis gas (syngas) followed by downstream conversion, direct routes aim to convert methane into valuable products without syngas intermediates [1,3]. Among these, the oxidative coupling of methane (OCM) has emerged as a promising direct method, enabling the formation of C₂ hydrocarbons such as ethane, ethylene, etc. These C₂ products can then be further upgraded via catalytic aromatization to produce aromatic hydrocarbons including benzene, toluene, xylene, and naphthalene.

This project investigates the novel oxidative coupling–dehydroaromatization (OC-DHA) technology. In this approach, methane is oxidatively coupled over a chemical looping catalyst to form ethane or ethylene. A zeolite catalyst is then used to convert C₂ products to form aromatics. The catalyst is regenerated in air. The oxidate coupling of methane/regeneration steps provide heat enabling autothermal operation. In this study, a plant-wide process model is developed in Aspen Plus v14. The OC-DHA reactor is modeled by using in-house experimental data. The process utilizing three reactors in series to complete OCM, DHA and SHC (selective hydrogen combustion) reactions. Following the reactor, the product stream is cooled and subjected to phase separation via condensation and water decanting to recover the hydrocarbon liquid phase enriched in aromatics. The aromatics are then separated as naphthalene, benzene, toluene, and xylene through distillation process. The process model is benchmarked and validated against a base-case configuration available in the literature on non-oxidative methane aromatization process [4]. To reduce the carbon footprint of the system, two process configurations were developed and evaluated. In Option 1, carbon dioxide (CO₂) generated from the process is captured using either cryogenic separation or conventional carbon capture methods. In Option 2, a methanation unit based on the Sabatier reaction is incorporated to convert CO₂ into methane, which is then recycled into the process feed, improving overall carbon efficiency.

A detailed techno-economic analysis (TEA) is performed using Aspen Process Economic Analyzer v14 to assess the economic viability of the proposed process under various operating scenarios. Sensitivity analyses are conducted to evaluate the impacts of key variables such as feedstock and product pricing, electricity costs, and carbon reduction technologies. The results indicate that the process can be economically feasible under specific conditions. Furthermore, a greenhouse gas (GHG)-only life cycle assessment (LCA) is performed, indicating the sustainability potential of the process by highlighting its ability to reduce carbon emissions relative to conventional aromatic production routes.

References:

1. Li, D.; Baslyman, W.S.; Siritanaratkul, B.; Shinagawa, T.; Sarathy, S.M.; Takanabe, K. Oxidative-Coupling-Assisted Methane Aromatization: A Simulation Study. Eng. Chem. Res., 2019, 58, 22884-22892.
2. Damasceno, S.; Trindade, F.J.; Fonseca, F.C.; de Florio, D.Z.; Ferlauto, A.S. Oxidative coupling of methane in chemical looping design. Fuel Proc. Tech., 2022, 231, 107255.
3. Corredor, E.C.; Chitta, P.; Deo, M.D. Techno-economic evaluation of a process for direct conversion of methane to aromatics. Fuel Proc. Tech., 2019, 183, 55-61.
4. Huang, K.; Maravelias, C.T. Synthesis and Analysis of Nonoxidative Methane Aromatization Strategies. Energy Technology, 2019, 1900650.