14-01-2013, 03:52 PM
Suspension catalytic distillation of simultaneous alkylation and transalkylation for producing cumene
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Abstract
This work deals with the improvement of the suspension catalytic distillation (SCD) process. An improved process that
alkylation and transalkylation reactions for producing cumene are carried out simultaneously in a SCD column, was put forward.
The kinetic data of alkylation of benzene with propylene over a modified -zeolite catalyst, YSBH-01, were determined in
a fixed-bed laboratory micro-reactor. On this basis, the equilibrium stage (EQ) model (MESHR equations) is established to
simulate the SCD column. The performance of the SCD column is discussed. The innovation present in this work for the SCD
process is also suitable for the fixed-bed catalytic distillation (FCD) process for producing cumene.
Introduction
The distillation process coupled with reaction,
namely reactive distillation (RD), has been devised
for many years. The RD process has been applied in
the industry, e.g. the manufactures of methyl acetate
and methyl tert-butyl ether [1–4]. In general, the RD
process is divided into two categories: homogeneous
and heterogeneous catalytic distillation. Moreover,
heterogeneous catalytic distillation is a more recent
development and has attracted researchers’ attention
because the separation between products and catalyst
is easy to accomplish. In recent years a new-type
heterogeneous catalytic distillation process,
The improved SCD process
The original SCD process, in which alkylation reaction
takes place in SCD column, but transalkylation
reaction in another fixed-bed reactor, is shown
in Fig. 2. In this work, an improved SCD process,
in which alkylation and transalkylation reactions take
place simultaneously in a SCD column, is proposed
and illustrated in Fig. 3.
In the improved SCD process, distillation and reaction
always take place at the same time in the
SCD column. But the upper section of this column
is used for alkylation reaction and the lower section
for transalkylation reaction. Transalkylation of DIPB
having a high boiling point is more concentrated in
the lower section than in the upper section of the
column in terms of vapor–liquid equilibrium (VLE).
The solid–liquid mixture leaving from the bottom is
treated by a gas–liquid separator (i.e. a static sedimentary
tank). The separated catalyst is recycled, and
some of them is regenerated from time to time.
Simulation of the SCD column
It is evident that the SCD column is the key in the
SCD process and should be paid more attention in
the simulation of the SCD process. It is interesting to
explore whether it is possible to integrate alkylation
with transalkylation into a single SCD column in terms
of the models. Both EQ and non-equilibrium stage
(NEQ) models [8–11] are able to adopted to simulate
the SCD column. However, building a NEQ model for
a RD process is not as straightforward as it is for the
EQ stage model in which we need to simply add a term
to take account of the effect of reaction on the mass
balances. As well-known, NEQ model is more complicated
than EQ model. In this study the EQ model was
established to simulate the SCD column.
Conclusion
The SCD process has just been present for a few
years and the research on it is still preliminary. In the
original SCD process, only alkylation reaction is carried
out in a SCD column. In this work, an improved
SCD process, in which alkylation and transalkylation
reactions are simultaneously carried out in a single
SCD column, is put forward. It is evident that by
adopting the novel process, the equipment investment
and energy consumption can be saved and the process
is convenient to operate, which has more industrial
benefits. To simulate the SCD column for producing
cumene with benzene and propylene, an EQ model
(MESHR equations) was adopted, in which the kinetic
model was established based on the experimental
data obtained in a fixed-bed laboratory micro-reactor.
Evidently.