(75d) Establishment and Kinetic Analysis of an in-Situ Crystallized Catalyst Based FCC Lump Kinetic Model

Nowadays, FCC units face
increasing pressure to convert more inferior and heavy oil into clean fuels and
light olefins as worsening qualities of feedstock and ever stricter
environmental regulations. Undoubtedly, catalyst is always one of the key
factors for FCC process and different catalysts could lead to significant
differences in product distribution. Besides, compared with technical reform
and plant revamp, replacement of the FCC catalyst is the most economical and
efficient way for FCC units to obtain a better product distribution. According
to the preparation method, FCC catalysts can be classified as semi-synthesized (gel
method) and in-situ crystallized FCC catalyst. As reported in some literatures,
in-situ crystallized FCC catalyst exhibited attractive prospect for inferior
and heavy oil processing, and was featured with better dispersion of zeolites,
smaller crystal size of zeolite, better thermal and hydrothermal stability
compared with semi-synthesized FCC catalyst.

Currently, BASF
Catalysts LLC (former Engelhard Corp.) and Catalyst Plant of China National
Petroleum Corporation (CNPC) Lanzhou Petrochemical Corporation are the main two
companies providing in-situ crystalized FCC catalyst worldwide, and the
research and development of in-situ crystalized FCC catalysts have made a lot
of progresses in near half a century. However, most of the studies of catalyst
design and corresponding operation optimization were mainly based on personal
experience and laborious experiments.

Kinetic study is a
powerful tool for a better understanding of the catalyst. As for the
complicated FCC reaction system, a method known as lump kinetic modelling is
needed. Actually, several lump kinetic models were reported for catalytic
cracking of heavy oil. However, those models were generally based on
semi-synthesized FCC catalysts and cannot reveal the kinetic characteristics of
the in-situ crystallized FCC catalysts. Moreover, lump kinetic modelling can
easily provide useful insights into operation optimization without laborious
experiments. Hence, it is necessary to establish a lump kinetic model of the
in-situ crystallized FCC catalyst.

In this work, the
kinetic characteristics of an in-situ crystallized FCC catalyst were reported
for the first time. A six-lump kinetic model containing 24 kinetic parameters,
one parameter for basic nitrogen poisoning, another parameter for aromatics
adsorption and other two parameters for catalyst deactivation was established.
Kinetic parameters were estimated based on experimental data at 460, 480, 500
and 520 °C by fourth order Runge-Kutta algorithm and
the least square method. Frequency factors and apparent activation energies
were then calculated according to Arrhenius equation. The predicted data of
product distribution showed good agreement with experimental data, and the
relative errors were mainly within 10 %. Model analysis indicated that a
relative low temperature was more suitable for the production of light oil.