Testing and Optimization of Nano Particles Reinforced PVAm/PVA Blend FSC Membranes for High Pressure Natural Gas Sweetening

Abstract

Employing gas separation membranes for natural gas sweetening is a cheaper, simpler, more energy ecient and an environmentally friendly alternative to separate CO2 from methane. Signicant advances has been made in membrane science and technology over the last couple of decades, and especially novel polymer-based FSC membranes have the potential of commercialization in the natural gas treatment industry.

In this master's thesis, a selection of nanoparticle reinforced PVAm/PVA blend FSC membranes have been prepared and tested at high pressure for natural gas sweetening. An ultra-thin selective layer was prepared from commercial polyvinyl amine (PVAm) and polyvinyl alcohol (PVA) and incorporated with either carbon nanotubes or fumed silica, and was cast on the support materials polysulfone (PSf), polyvinylidene uoride (PVDF) and cellulose acetate (CA). Permeation tests were carried out at a high pressure pilot scale membrane permeation rig, and the eect of pressure up to 80 bar was investigated. The permeate gas composition was analyzed with a gas chromatograph, and for a total of 11 dierent membranes, the CO2 permeance and CO2/CH4 selectivity was calculated. Scanning electron microscopy was employed to analyze the morphology of the membranes.

Several preparational conditions such as nanoller concentration, solution ltration and selective layer thickness were explored and yielded good results. One membrane in particular showed both high permeance and selectivity at high pressures, with a CO2/CH4 selectivity of 26.9 and a CO2 permeance of 0.034 m3(STP)/m2.h.bar at 60 bar and 30C, with a feed gas ow rate of 0.120 m3/h. The mechanical strength from the nanocomposite PVAm/PVA selective layer with an average thickness 0.670 m on a PSf support showed good permeability and high selectivity for high pressures.