Page 30 - Industrial Plants 2014

metathesis reactions;
• Methanol to propylene or olefins (MTP/MTO).
However over the last years, the shale gas advent in
the USA is pushing towards a change in the
worldwide economy. Shale gas recovery by
horizontal drilling and the use of fracking technology
has resulted in the US having an abundance of
natural gas. Once natural gas is available, it is
fractioned to separate ethane from the rest of the
natural gas; the separated ethane is then fed into
the pipeline. The consequent change of feedstock
will greatly affect the product distribution in the
effluent of a liquid cracker. The amount of propylene
produced in an ethane-consuming steam cracker is
about 10 times less than what is produced when
consuming naphtha-range material. Therefore, the
shift towards shale gas would result in constrained
Fig. 8 - Feed being the precursor of polypropylene, which is used propylene supply for petrochemical consumption
conversions against in such everyday products as packaging materials and a potential price increase.
oxygen to carbon and outdoor clothing. On the other hand, according to
ratio. Comparison At present time, steam cracking with market analysis experts, the global
between standalone Among the olefns,
and integrated feedstocks as naphtha and ethane propylene is the demand for propylene is expected to
configuration and fluid catalytic cracking (FCC) world’s second increase between 3% and 6% over
with feedstock as gas oil and residue largest petrochemical the next three years. Given the trend
represent the main technologies for commodity, being discussed above, the alternative of
the production of propylene, which in the precursor of on purpose technologies and their
this case is obtained as by-product polypropylene, which is intensification are becoming
of ethylene production. Steam used in such everyday increasingly well positioned to meet
crackers and FCC cover respectively products as packaging the growing demand for propylene.
for 55 and 30% of the total demand materials and outdoor Among these technologies, selective
Fig. 9 - Propane of propylene. The remaining 15% is clothing PDH is believed to have a great
conversion to ensured by the following “on potential as a propene booster in the
propylene in a purpose” technologies, which are future.
membrane integrated
reactor as a function optimized to produce propylene as main product: The thermodynamic constraints of the reaction limit
of membrane • Propane DeHydrogenation (PDH); alkane conversion, hence the necessity to operate
permeance • Olefins Conversion Technology (OCT) or at high temperature in order to reach a sustainable
reactant conversion. In spite of the huge efforts into
the direction to increase process selectivity, avoiding
in particular coke formation, the severe operating
conditions still lead to coke deposition on the
catalyst, thus to its deactivation. This is the reason
why in the commercialized process a periodic
regeneration of the catalyst is required. Accordingly,
the complexity of the overall plant limits the potential
for this technology of scale down to 1/5 of the
original capacity. The possibility to strongly decrease
the amount of carbonaceous compound deposited
on the catalyst is linked to the possibility to attain
sustainable propane conversion at temperature
lower than 550 °C, overcoming the thermodynamic
limitations, hence the use of membrane reactors
(figure 9).
A patent application was filed by KT in 2011 where
the membrane reactors are still arranged in a non
integrated approach [8]. The great importance and
potentiality of this novel approach is linked to the

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