A three-pronged attack on zeolites for the petrochemical industry

In the petrochemical industry the separation of propylene from propane is both an important and challenging process. The current process, cryogenic distillation, is one of the most energy demanding in the whole refinery. One possible solution is to use zeolites - microporous minerals already used in many industrial processes. Acting as tiny sieves, zeolites can selectively trap molecules in a cage like structure, making them particularly useful in catalysis and separation processes. A group from the Institute of Chemical Technology (ITQ) at the Universidad Politecnica de Valencia have been using three ISIS instruments, TOSCA, MARI and LET, to study a new zeolite material, ITQ-29, that could be used to tackle the propane/propylene problem.

The demand for propylene in chemical processes is increasing, so the petrochemical industry has been scrutinising the separation process in order to improve future refineries. Conventional zeolites aren’t suitable due to the presence of aluminium in the framework which causes them to develop acidic properties. This can result in the zeolite pores becoming blocked, and the process of unblocking is energy consuming.

An alternative is to use pure silica zeolites, which do not become acidic and are very stable and easy to regenerate if the pores do become blocked. The group have been studying ITQ-29, a form of pure silica zeolite developed at the Institute of Chemical Technology (ITQ) in Valencia, to see if it can be used in propane-propylene separation. Further, they have refined ITQ-29 by substituting Ge for Si in the zeolite framework, allowing them to fine-tune the pore opening.

Professor Rey led the experiment. He says, “It is of fundamental and applied interest to understand the interaction behaviour of propane and propene with Ge-containing and pure silica ITQ-29 zeolites. To our knowledge, this is the first time that Neutron Scattering techniques have been used for propane and propylene separation studies.  Our aim is to understand the influence of framework composition and/or pore aperture in this industrially relevant separation process using non-charged zeolites as adsorbents. Identifying and quantifying the hydrocarbon - zeolite interactions could provide useful information for improving future refinery processes.”

Sara Fletcher

Research date: May 2013

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