(560dn) Kinetic Modeling of Catalytic Cracking of Paraffinic Naphtha with Molecular Mechanism

Title: kinetic modeling of catalytic
cracking of paraffinic naphtha with molecular mechanism.

Author: Ha-Nui Jo¹, KiWoong Kim²,
Jinsu Kim¹, Yoojin Han³, Jae-Wook Shin²,
Young-Seek Yoon³* and In-Beum Lee¹**

1) Department of Chemical Engineering, Pohang
University of Science and Technology, Pohang, South Korea

2) Korea Research Institute of Chemical
Technology, Daejeon, South Korea

3) Graduate Institute
of Ferrous Technology, Pohang University of Science and Technology, Pohang,
South Korea

*E-mail: ysyoon@postech.ac.kr

**E-mail: iblee@postech.ac.kr

Light olefins such as ethylene and
propylene are the basic component in the petrochemical industry. These light
olefins can be obtained by catalytic cracking of naphtha. However, the pathway
of Naphtha-to-Olefin (NTO) reaction has not yet been defined because naphtha
consists of various compositions of hydrocarbons and the reaction rate is very
fast. For the interpretation of the NTO reaction, mechanistic mechanism and
molecular mechanism can be used. The mechanistic mechanism is a reaction path
that covers all of the detailed reaction paths including carbenium and
carbonium ions, which are intermediates formed on the catalyst surface. Based
on this mechanism, intrinsic reaction rates can be derived, which does not
change depending on the experimental conditions. However, this mechanism has
more than 2000 reaction pathways, which not only includes unobservable intermediate
such as carbenium ion but also increases the computation load for estimating
reaction rate parameters. In addition, this makes it difficult to derive
accurate reaction parameters because vast amounts of experimental data are
required to estimate all of the reaction parameters accurately for more than
2000 reactions. As an alternative to this, the molecular mechanism can be
considered, which configures the reaction pathway only with observable molecules.
In the existing studies, simple reaction pathways are presented, which focuses
on the high predictability of light olefins. However, these reaction paths do
not include all the actual reaction paths and they can yield results that are
inconsistent with the experimental data at different reaction conditions.

In this paper, we proposed a reaction path
that is constructed with the molecular mechanism by converting the mechanistic
mechanism, which is the actual reaction mechanism. Therefore, this reaction
mechanism included all the reaction pathways while it was composed with
observable molecules. It made the estimated reaction parameters to have
robustness depending on the experimental conditions such as feedstock
composition and temperature. In addition, we initially used experimental data
with single hydrocarbon feed to estimate reaction parameters with high
accuracy, which is less complex than a normal naphtha cracking. By using these
parameters as a criterion to determine other parameters at a complex cracking
reaction of normal naphtha, the difference of reaction rate by carbon number
and reaction type was reflected as constraints. This approach can derive the
reaction rate parameters with physical meaning, not derive the numbers simply
fitting the values of the experimental data and model.

Acknowledgement

This work was supported by the National Research Council of
Science & Technology (NST) grant by the Korea government (MSIT) (No. CRC-14-01-KRICT).