Panel I - Innovative Process and its modalities
Paper N1.1 - Transformation of the old process: ethylbenzene
to styrene with CO2 dilution
Min Che Chon, Chon International Company, Ltd. Republic of
Korea
Abtsract: This invention originated from the idea of utilization
of carbon dioxide, a representative global warming gas, as the soft
oxidant in oxidative catalysis. Before starting this research, most
studies on catalytic conversion of CO2 have been concentrated
on the utilization as a carbon source through catalytic reduction
processes with hydrogen, but this approach was found to be economically
non feasible unless more efficient process for H2 production
is developed. So, the present inventors paid attention to another
possibility to utilize oxygen atoms of a carbon dioxide molecule
for not only the oxidant to abstract hydrogen atom in dehydrogenation
of hydrocarbons but also an oxygen transfer agent in partial oxidation
of hydrocarbons. The C-H bond dissociation through the hydrogen
abstraction with oxygen species is generally accepted to be the
rate-determining step in dehydrogenation of hydrocarbons. To date,
styrene has been mainly produced by the EB dehydrogenation using
potassium-promoted iron oxide catalysts with a large excess of superheated
steam. It is one of the ten most important industrial processes.
This reaction is generally carried out in vapor phase at 600 - 650oC
under steam, so that this commercial process using expensive steam
consumes a large amount of latent heat of steam upon condensation
at a liquid-gas separator following a reactor. Moreover, it is thermodynamically
limited besides energy consuming. Use of traditional oxidant, oxygen
is able to allow the overcome of the thermodynamic limitation, but
a process with direct use of oxygen for oxidative dehydrogenation
is not been realized yet because of a significant loss of styrene
selectivity by the production of carbon oxides and oxygenates. Judging
from such reasons described above and characteristics of carbon
dioxide, the utilization of CO2 as the soft oxidant can offer
many beneficial advantages in styrene production.
Based on these ideas, researchers of KRICT (Korea Research Institute
of Chemical Technology) developed a novel process for dehydrogenation
of ethylbenzene to produce styrene using carbon dioxide as soft
oxidant, so-called KRICT-DECSO process. In addition to the above
advantages, it is advantageous in the KRICT-DECSO process that very
cheap carbon dioxide thus obtained from by-product of petrochemical
oxidation or reforming process is utilized without further purification
instead of using expensive steam dilution agent. The dehydrogenation
catalyst employed comprises oxygen-deficient iron oxide and many
promoters with transition metal oxides.
The KRICT-DECSO process is under verification through pilot-scale
work so that process and engineering data necessary for the industrial
application should be further collected. On-site mini-pilot plant
is operating at Samsung General Chemicals Co., Ltd. (SGC). The scale
of the pilot plant is 100kg of styrene monomer per day.
The project to develop and establish the KRICT-DECSO process was
performed for the Greenhouse Gas Research Center, one of the Critical
Technology-21 Programs, funded by the Ministry of Science and Technology
(MOST) of Korea. A Korean small company has participated in this
research as a partial financial sponsor, which has a plan to take
a property for catalyst production of this process. And SGC has
joined the project as a cooperating company and recently constructed
pilot-scale demonstration unit in the Daesan Petrochemical Complex
and is still testing catalyst performance for this process. Development
of preparation method and scale-up technology of the commercial-type
dehydrogenation catalyst to be sufficiently stable for the industrial
application would be a key for the success of the process.
In spite of many beneficial roles of steam as dilution agent the
main problems in the present ethylbenzene dehydrogenation process
are confronted with thermodynamic limitation of the process and
the use of steam. However, it is demonstrated that a decrease by
up to 50oC in reaction temperature
through equilibrium alleviation could be accomplished using CO2
as the oxidant. And considering energy saving effects due to a drop
of reaction temperature and replacement of steam with CO2,
it estimated by process simulation that the energy consumption required
for the EB dehydrogenation using carbon dioxide would be much lower
than that for the currently operating process using steam. Now,
the KRICT inventors are trying to verify such beneficial effects
in mini-pilot plant work at petrochemical complexes.
