| Summary: |
Olefin/paraffin separations are one of the most important in the petrochemical industry. Traditional systems used for this separation, e.g. low temperature distillation and extractive distillation, are expensive, energy consuming and only attractive for streams containing high amounts of olefins. This provides an incentive to develop cost effective separations.
Up to very recently, most commercially available membranes for gas separations were polymeric. Polymeric membranes show low to medium selectivities and permeabilities and can operate only in mild conditions. The development of molecular sieve membranes, with pores in the nanometric range, started about two decades ago, with the pioneering work by Soffer (carbon molecular sieve membranes) and by Barrer & Suzuki (zeolite membranes). These two membrane families are expected to exhibit simultaneously higher permeabilities and selectivities when compared with polymeric membranes.
The aim of the present project is to develop a new class of ceramic ultramicroporous membranes, containing fixed site carriers, and also a corresponding catalytic membrane reactor. Despite the very few publications on ceramic ultramicroporous membranes with facilitate transport capabilities, AgNO3 modified ceramic adsorbents are reported to show very good adsorption equilibrium olefin/paraffin selectivities. Also, recently it was launched in the market PSA units using the UOP AgLiLSX zeolite to perform olefin/paraffin separations.
One of the most industrially important olefin/paraffin separations is the propylene/propane. For this separation the olefin is the fastest moving and the most adsorbed species. When this occurs, there is a synergetic separation effect and the effective selectivity (bicomponent one) becomes far higher than the corresponding monocomponent one. There are then reasons for expecting a good performance from the proposed ceramic ultramicroporous membrane with fixed site carriers.
At least two different types of  |
Summary
Olefin/paraffin separations are one of the most important in the petrochemical industry. Traditional systems used for this separation, e.g. low temperature distillation and extractive distillation, are expensive, energy consuming and only attractive for streams containing high amounts of olefins. This provides an incentive to develop cost effective separations.
Up to very recently, most commercially available membranes for gas separations were polymeric. Polymeric membranes show low to medium selectivities and permeabilities and can operate only in mild conditions. The development of molecular sieve membranes, with pores in the nanometric range, started about two decades ago, with the pioneering work by Soffer (carbon molecular sieve membranes) and by Barrer & Suzuki (zeolite membranes). These two membrane families are expected to exhibit simultaneously higher permeabilities and selectivities when compared with polymeric membranes.
The aim of the present project is to develop a new class of ceramic ultramicroporous membranes, containing fixed site carriers, and also a corresponding catalytic membrane reactor. Despite the very few publications on ceramic ultramicroporous membranes with facilitate transport capabilities, AgNO3 modified ceramic adsorbents are reported to show very good adsorption equilibrium olefin/paraffin selectivities. Also, recently it was launched in the market PSA units using the UOP AgLiLSX zeolite to perform olefin/paraffin separations.
One of the most industrially important olefin/paraffin separations is the propylene/propane. For this separation the olefin is the fastest moving and the most adsorbed species. When this occurs, there is a synergetic separation effect and the effective selectivity (bicomponent one) becomes far higher than the corresponding monocomponent one. There are then reasons for expecting a good performance from the proposed ceramic ultramicroporous membrane with fixed site carriers.
At least two different types of precursor for the ceramic ultramicroporous tubular membranes will be selected, characterised, modified for silver introduction and characterised again. The precursors will be selected taking into account the highest selectivity and permeability and suitability for introducing silver fixed carriers. A zeolite Y and silicate membranes will be tested first based on the available best information.
Finally, it will be studied the use of the ceramic tubular membrane module for conducing a reaction and then improving the selective removal of propadiene and propyne traces from propylene a stream and their conversion to propylene. Preliminary studies conducted at LEPAE showed a nearly 100% selectivity hydrogenation of propyne traces to propylene in a propylene/propyne stream, conducted in a polymeric catalytic membrane reactor. The idea is making a silver-zeolite Y selective layer with a nanosized catalyst coating (palladium) in the permeate side. |