The use of natural gas for power generation and seawater desalination, as well as for chemical feedstock, provides opportunities for Saudi Aramco to diversify beyond crude oil. Heavy hydrocarbons (C3+), often referred to as natural gas liquids (NGL), must be separated from natural gas through energy intensive refrigeration processes. Alternatively, commercially available siloxane membranes separate NGL from natural gas using significantly less energy. Due to their high permeabilities, these membranes can reject N2 and concentrate C3+ in membrane permeate streams. However, current state-of-the-art PDMS membranes exhibit lower C3+/C1 selectivities due to swelling under aggressive testing conditions. Here, we demonstrate strategies to overcome this limitation by developing more efficient siloxane membranes with improved C3+/C1 selectivity for heavy hydrocarbon separation and recovery. Novel PDMS membrane materials comprised of vinylmethylsiloxane terpolymers were prepared via an addition curing or grafting-hydrolysis-polycondensation process by controlling polymer backbone and side-chain structures, crosslinking moieties, and crosslinked networks in the membrane matrix. This talk compares these novel PDMS structures to commercially available PDMS under industrially relevant conditions, including the use of C1-C5 multicomponent hydrocarbons in the presence of N2, CO2 and BTEX contaminants at 800 - 850 psi. These results demonstrate the strong dependence of C3+/C1 selectivity on feed compositions, operating parameters and PDMS chemical structure. The results of this study aim to advance the development of these promising siloxane membrane materials for aggressive natural gas separations.

Development of novel PDMS membranes for C3+ hydrocarbon recovery from natural gas

2019 Spring National Meeting

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