(715e) Carbon Dioxide Separation from Syngas Using Polymeric and Mixed Matrix Membranes

Greenhouse gases are major contributors to climate change and CO₂ emissions are responsible for huge percentage of these greenhouse gas emissions. Fuel combustion has been shown to be the major cause of increase in CO₂ emissions into the atmosphere. This has increased interest in developing means of decreasing the net CO₂ emissions. These technologies include carbon capture and storage (CCS), as well as carbon recycle into fuels and valuable chemicals.

This study centers around post combustion strategy whereby stored CO₂ after combustion is used to produce hydrocarbons through Reverse Water Gas Shift (RWGS) reaction and Fischer-Tropsch reaction. It is important to separate CO₂ from CO and H₂ (syngas) in between these reactions. This can be done using membranes, which is the focus of this study.

Poly Vinyl alcohol (PVA) membranes were chosen to be studied due to their good film forming ability and their chemical and thermal stabilities. Formaldehyde cross-linker is chosen due to the previously promising results observed with their use. Mixed matrix membranes were synthesized with the addition of carbon dots. The synthesized membranes were supported by Polyacrylonitrile (PAN) support and 2wt% of PVA is used with 10wt% of carbon dots with some of these membranes to produce mixed matrix membranes (MMM). The permeability of CO₂ has been shown to decrease with increase in pressure difference and that of CO and H₂ has been shown to increase. Also, the addition of formaldehyde and other mobile cross-linkers increase the permeability of the membrane for CO₂ while not changing the permeability for CO and H₂, thus increasing the selectivity of the membrane for CO₂ over CO and H₂. This effect was furthered with the addition of carbon dots into the matrix of the PVA membrane with much higher selectivity values observed for CO₂ over CO and H₂.