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John Yang1 Daniel Harrigan1 Justin Vaughn1 Millind Vaidya2

1, Aramco Research Ctr, Cambridge, Massachusetts, United States
2, R&DC, Saudi Aramco, Dhahran, , Saudi Arabia

Saudi Aramco has a strategic interest in recovering valuable higher hydrocarbons (C3+). These higher hydrocarbons, also known as natural gas liquids (NGLs), can be used to reduce the Kingdom’s reliance on liquid fuel for power generation and can also be used as a feedstock for downstream chemical production. The conventional separation of NGLs from natural gas is typically accomplished through energy intensive refrigeration processes. Polymeric membranes that are selective for C3+ (e.g. propane and butane) relative to methane could provide a lower energy alternative to accomplish such a separation. Currently, polydimethysiloxane (PDMS), a commercially-available silicon-based rubbery membrane material, exhibits prohibitively low C3+//methane selectivities under rigorous testing conditions, hindering their application in industrial gas processing plants. To achieve significant recovery of NGLs from natural gas while reducing capital and operating expenditures, more efficient membranes with improved selectivity are required. This work describes progress to improve the C3+/methane separation efficiency of modified PDMS by incorporating bulky hydrocarbons into the polymer matrix. The effect of polymer backbone modifications and crosslinking agents on membrane physical properties and permeation performance is investigated. Modified PDMS membranes show enhanced gas permeation performance compared to commercial PDMS under industrially-relevant feed streams and testing conditions, including with multicomponent C1-C4 hydrocarbon mixtures up to 800 psi and in the presence of aggressive contaminants, including benzene, toluene, ethylbenzene, and xylene (BTEX). The results of this study aim to advance the rapid development of novel rubbery membrane materials for enhanced NGL recovery from natural gas.

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