(279f) Fundamental research on phase equilibrium of extraction desulfurization

Fundamental
research on phase equilibrium of extraction desulfurizaiton of FCC gasoline

Yuhao Zhang, Liang
Zhao, Jinsen Gao, Chunming Xu

State Key
Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing),
Beijing, China, 102249

Due
to the increasing awareness of protecting environment, the great demand for
ultralow sulfur contents in motor gasoline has become increasingly significant.
Nowadays, many technologies have
the ability to produce clean gasoline to meet the requirement of sulfur content
(<10 ppm). Approaches of desulfurization could be divided into hydrodesulfurizaiton
and non-hydrodesulfurization. Wherein, the hydrodesulfurization processes were well
developed and widely applied in the whole world, such as ISAL, Octgain, Prim-G⁺,
SCAN Fining, and CDTech ^[1-5] processes. Part of non-hydrodesulfurization processes were also gathered
much attention, such as adsorptive desulfurization, extraction desulfurization, oxidative
desulfurization, and biological desulfurization^[6-12]. Wherein, extraction
desulfurization process was well developed because advantages of variety of
solvents, high selectivity, low operating price, low energy
consumption, eco-friendly, et al. Commonly, it was divided into solvent
extraction^[7,13] and extractive distillation^[14-17]
depending
on the mechanism, such as Shen reported a gasoline desulfurization using solvent
extraction^[7] and GTC-BTX Plus technology^[14] by
extractive distillation. In spite of the theory of these two methods were
different, the interaction of phase equilibrium between solvents and key
components of FCC gasoline still plays a significant role to impact the effect
of separation which could be express through liquid-liquid equilibrium or vapor-liquid
equilibrium experiment.

In
this research, the composition of different distillation fractions of FCC
gasoline were analyzed and the feedstock of solvent extraction and extractive
distillation were selected carefully. And then, particular investigated the
properties of different kinds of single solvents using liquid-liquid
equilibrium and vapor-liquid equilibrium experiment to found the fundamental of
extraction desulfurization of FCC gasoline. Furthermore, an optimal compound
solvent were selected using phase equilibrium experiment.

 In
conclusion, the effect of separation performance of different solvents were
studied in several ways. Sulfolane shown a great interaction of aromatics and sulfides.
Furthermore, a best compound solvent was determined which the sulfur separation
rate was 75 % and has the ability to separate C6~C8 olefins into the raffinate
containing a small quantity of aromatics. The results were shown in Figure 1 to
Figure 3.

Figure 1 Selectivity
of olefins and aromatics using different single solvents

k_A shows the ability
to dissolve aromatics; θ shows the ability of selectivity
between aromatics and olefins

Figure 2  Sulfur
separation rate and raffinate yield using compound solvents

Figure 3  Olefin
and aromatics distribution in raffinate using optimal compound solvent

Acknowledgement

This
research is supported by National Natural Science Foundation of China (Grants
21336011, 21476260 and 21236009). And also supported by the Science Foundation
of China University of Petroleum-Beijing (Grants 2462015YQ0311).

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