The Effect of the Type and Concentration of the Crosslinking Diene on the Gas Transport Properties of Membranes Based on Polyoctylmethylsiloxane

Abstract

The effect of the type and amount of crosslinking reagent on the gas transport properties of polyoctylmethylsiloxane (POMS) membranes is studied for the first time. 1,7-Octadiene (OD), divinyltetramethyldisiloxane (DMDS), and two samples of polydimethylsiloxane (PDMS 500, PDMS 25000 with the molecular weights of 500, 25000 g/mol, respectively) are used as crosslinking reagents. The permeability, diffusion, and solubility coefficients are measured for n-butane, methane, carbon dioxide, and nitrogen, and the corresponding ideal selectivities of permeability, diffusion, and solubility are calculated. It is shown that the optimal membrane properties of POMS with the use of DMDS as the crosslinking reagent are achieved at a concentration of DMDS of 3%: the maximum values of the permeability coefficient of n-butane (9400 Barrer) and ideal selectivity of permeability of n-butane/methane (26.1). A decrease in both the selectivity of solubility and selectivity of diffusion is observed for the n-butane/methane gas pair in the DMDS, PDMS 500, and PDMS 25000 series of crosslinking reagents with an increase in the fraction of a siloxane crosslinking reagent.

Hydrophobic Ag-Containing Polyoctylmethylsiloxane-Based Membranes for Ethylene/Ethane Separation in Gas-Liquid Membrane Contactor

“…POMS-based membranes with POMS-Ag and without Ag-containing POMS were prepared according to the following method, developed based on earlier studies [45][46][47][48]. To begin, PHMS, 1-octene, and 1,7-octadiene in mole relation to 10:9.4:2.6 were mixed in the presence of 2.3 wt% Carsted catalyst (to pure reactive) in the isooctane media.…”

“…The ethylene/ethane ratio was 20% vol./80% vol. The gas permeability of the flat-sheet membranes was studied, employing the apparatus described in detail in a previous study [47], with the following conditions: temperature, 23.6-25 • C; effective membrane permeation area, 13.8 cm 2 ; downstream membrane pressure, 2-5 cm/Hg; stage-cut, 2-5%. A feed, permeate and retentate analysis was conducted using a gas chromatograph, the Gazokhrom-2000 (Chromatek, Yoshkar-ola, Russia), with a column filled with 20% heptadecane filler on the diatomite carrier.…”

High-Selectivity Polysiloxane Membranes for Gases and Liquids Separation (A Review)

“…Performing the modification and cross-linking by hydrosilylation allows also using a single catalyst, which improves the economic efficiency of this approach. The simplicity of the suggested procedure allowed us to study in our subsequent works how various crosslinking agents influence the gas-transport properties of membranes based on polyoctylmethylsiloxane (POMS) [72] and polydecylmethylsiloxane [73]. As we showed, an increase in the length of the cross-linking agent, divinyltetramethyldisiloxane-PDMS (M n = 25000 g mol -1 ), leads to a decrease in the ideal n-butane/ methane selectivity from 26 to 22 and to an increase in the permeability coefficient (from 9600 to 9800 Barrer at the pressure over the membrane of 0.8 bar) [72].…”