جداسازي گازهاي اتيلن/اتان و پروپيلن/پروپان با استفاده از غشاي نانو كامپوزيت سلولز استات

چكيده انگليسي :

92 Separation of Ethylene Ethane and Propylene Propane by Cellulose Acatate Silica Nanocomposite Membranes Mahdi Naghsh m naghsh@ce iut ac ir Date of Submission 20 04 2011 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Morteza Sadeghi m sadeghi@cc iut ac ir Ahmad Moheb ahmad@cc iut ac irAbstractEthylene and propylene are the most important feedstock in the petrochemical industry Large quantities ofthese light olefins are used in the production of plastics and chemicals Ethylene and propylene areproduced by different methods such as steam cracking catalytic cracking and dehydrogenation ofparaffins Separation of olefin paraffins mixture is great significance in petrochemical industry andcurrently performed by cryogenic distillation which is expensive and energy intensive duo to the lowrelative volatilities of the components Polymeric membrane separations have been considered as anattractive alternative because of low energy consumption low capital investment and simple operation Inthe last decades improving the performance of polymeric membranes for example by adding inorganicnanofillers is one of the predominant concerns of the researchers In the present work the separation ofethylene ethane and propylene propane by cellulose acetate silica nanocomposite membranes were studied Silica nanoparticles were prepared via the hydrolysis of tetraethoxysilane TEOS Membranes wereprepared by thermal phase inversion method The prepared membranes were characterized using FT IR SEM DSC and TGA methods The results demonstrate a nano scale and good distribution of silica particlesin the polymer matrix This confirms the desirable mixing of the silica in polymer and also a goodcompatibility between the two phases The thermal properties of cellulose acetate membranes were alsoimproved by adding silica particles The performance of prepared membranes in ethylene ethane andpropylene propane separation were measured at pressure of 2 bara and temperature of 35 C The obtainedresults showed that the permeability of ethylene and propylene increased from 0 052 barrer and 0 046 barrerin pure cellulose acetate to 0 11 barrer and 0 098 barrer in the composite membrane containing 30 wtsilica particles The comparison of the selectivities of C2H4 C2H6 and C3H6 C3H8 indicates an increase inthese quantities from 2 16 and 2 55 in pure polymer to 4 07 and 6 12 in composite membrane containing30 wt silica particles The diffusion and solubility coefficients were determined by the time lag method The results showed an increase in solubility coefficient and decrease in diffusion coefficient of gases withincreasing the silica mass fraction For example the diffusion coefficient of ethylene decrease from21 22 10 10 cm2 s in pure cellulose acetate to 14 02 10 10 cm2 s in composite membrane containing 30 wtsilica particles and it s solubility coefficient increased from 2 21 10 3 cm3 STP cm3 cmHg to 7 85 10 3cm3 STP cm3 cmHg In order to investigate possible plasticization phenomena the effect of feed pressureon separation performance and O2 N2 selectivities befor and after exposure of membranes with propylenewas studied With increasing feed pressure the permeability and solubility coefficients of gases decreasedand the diffusion coefficient increased Decreasing permeability with increasing feed pressure is consistentwith the dual mode sorption for glassy polymers and indicates that no plasticization occurs in purecellulose acetate and composite membranes up to 8 bara feed pressure Before the exposure of propylene the pure and composite membrane containing 30 wt silica particles show O2 N2 selectivity of 5 08 and5 77 respectively After the membranes were exposed to propylene O2 N2 selectivity did not change Thisresults showed that no plasticization occurs Keywords Olefin paraffin separation polymeric nanocomposite membrane celluloseacetate silica gas separation

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جداسازي گازهاي اتيلن/اتان و پروپيلن/پروپان با استفاده از غشاي نانو كامپوزيت سلولز استات - سيليكا

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