(491f) Synthesis and Multicomponent Permeation Evaluation of Functionalized PDMS Membranes for Enhanced NGL Recovery from Natural Gas

Saudi Arabia owns the 5^th largest proven reserves of natural gas in the world. Most of this resource is utilized for domestic energy production. For decades, glassy membrane technology has been successfully applied to remove CO₂ from natural gas. More recently, commercially available poly(dimethylsiloxane) (PDMS) rubbery membranes, have been utilized for natural gas liquid (NGL) recovery from natural gas. NGL can be utilized as a liquid fuel for power generation and can also be used as a feedstock for chemical production. Due to their high permeability properties, PDMS membranes can at the same time reject nitrogen and concentrate heavy hydrocarbons (C₃₊) from both wet sour gas and sweet dry gas in the membrane permeate streams, which can be then routed to a NGL recovery unit. However, the current state-of-the-art PDMS membranes exhibit low C_3+//methane selectivities under industrially-relevant feed streams and testing conditions. In order to achieve significant enhanced recovery of NGL from natural gas while reducing capital and operating expenditures, more efficient membranes with improved selectivity are desired.

This talk seeks to provide detailed investigation of separation performance of modified PDMS type composite membranes for enhanced NGL recovery under rigorous testing conditions, in order to more closely approximate those encountered in a gas plant. A new type of functionalized PDMS membrane material containing Si-C-C-Si internal network and Si-diphenyl or Si-fluorine side chains in the membrane matrix was synthesized over a porous support of polyacrylonitrile. These functionalized PDMS composite membranes demonstrate superior NGL separation performance as compared to traditional PDMS membrane at all conditions tested (e.g. multicomponent C₁-C₅ hydrocarbon mixtures, up to 850 psi feed pressure, temperature, feed gas composition, presence of aggressive BTEX contaminants). The C₃₊/methane mixed gas selectivities were observed to be significantly enhanced by the substitution of rigid backbone and crosslinking moieties. The results of this study aim to advance the development of novel rubbery membrane materials for aggressive natural gas separations.