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宁夏大学硕士生考试考查卷面纸
～～
学年度第
学期
姓
名
学
号
院
（
所
、
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）
年
级
专
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研
究
方
向
课
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考
试
方
式
主考教师评语
成绩
主考教师签名：
200
年
月
日
Supercritical Fluid
Extraction
Abstract:
Solvent
extraction
is
an
important
mass
transfer
unit
operation.
Supercritical fluid extraction (SFE), a
sustainable green technology leads a wide range of
applications since the past decade.
Background of supercritical fluid extraction
technology
was introduced and overview
of the technology of supercritical fluid
extraction was also
introduced.
Focused on the method of enhanced
extraction and industrial
applications
of
supercritical fluid
extraction technology.
Keywords:
solvent
extraction,
supercritical
fluid
extraction
technology,
enhance,
industrial
application
宁夏大学硕士课题论文
Supercritical
fluid
extraction
Supercritical
Fluid Extraction
1.
The background of solvent extraction
Extraction
techniques
play
a
unique
role
in
analytical
chemistry.
At
the
same
time,
extraction generally
is relegated to a support role and it has just
been within the past 15
years or so
that the importance of extraction technology has
been recognized for its role in
the
generation of quality analytical information [1].
Solvent
extraction
is
an
important
mass
transfer
unit
operation.
In
this
process,
the
solute
is
of
different
distributions
between
two
immiscible
or
partially
miscible
in
the
liquid
phases, which can achieve the purpose of
separating or purifying the liquid mixtures
[2]. Solvent extraction is usually
operated at room temperature or low temperature.
With
the
characteristics
of
low
energy
consumption,
it
is
more
suitable
for
the
separation
of
heat-sensitive
substances
and
easily
realizing
the
economic
countercurrent
operation,
which is
conducive to continuous mass production. Its range
of applications throughout the
field of
petroleum,
chemical, hydrometallurgy,
medicine, nuclear, biological
engineering,
mew materials,
environmental protection, etc.. Solvent extraction
method has advantages
of high
selectivity and efficient separation.
Solvent
extraction
began
in
the
1840s.
According
to
historical
records,
there
were
researchers
extracted
uranyl
nitrate
with
diethyl
ether
in
the
analysis.
During
the
early
twentieth
century,
using
solvent
extraction to
run
the aromatics extraction process
in
the
Oil
Industry, it indicated the starting of industrial
application. From 60 years 20th Century,
solvent extraction technology has
been
applied in
Petrochemical
and Hydrometallurgical
Industry on great scale. So far, the
solvent extraction has developed in several
aspects as
supercritical
fluid
extraction
[3],
two-phase
aqueous
extraction,
microwave
extraction,
membrane
extraction,
reversed
micellar
extraction,
electro-
extraction,
ultrasonic
solvent
extraction,
predispersed solvent extraction, nonequilibrium
solvent extraction.
2.
The development of supercritical fluid
extraction
Supercritical fluid
extraction (SFE), a sustainable green technology
leads a wide range
of
applications
since
the
past
decade.
It
is
a
more
developed
technique
which
uses
a
supercritical
fluid
as
extraction
solvent.
It
derived
from
1960s
and
developed
rapidly
in
chemical
separation
techniques.
SFE
is
an
innovative,
clean
and
environmental
friendly
technology with
particular interest for the extraction of
essential oil from plants and herbs
[4].
SFE
can
be
used
on
separation,
purification,
concentration,
drying,
the
sterilization
process, the polymerization reaction,
and the actual production. Its scope of
application has
been
included
organic
chemicals,
petroleum,
pharmaceutical,
food,
environmental
protection,
analytical chemistry, textile dyeing, pulp and
paper, paint, fine ceramics, wood
processing corrosion and other fields.
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宁夏大学硕士课题论文
Supercritical
fluid
extraction
SFE
is
based
on
the
solvating
properties
of
supercritical
fluid
(SF),
which
can
be
obtained by employing
pressure and temperature above the critical point
of a compound,
mixture
or
element.
Extraction
by
SF
depends
on
some
intrinsic
tunable
natures
of
supercritical
fluid
like
temperature,
pressure
and
some
extrinsic
features
like
the
characteristics
of
the
sample
matrix,
interaction
with
targeted
analysts
and
many
environmental factors [5,6]. By proper
controlling of SFE parameters, the extractability
of
supercritical fluid can also be
modified which enable this process to find its
field from food
to
pesticide
researches
[7].
Mo
r
eover,
a
higher
degree
of
freedom
can
be
obtained
in
extraction
by
SFE
than
the
conventional
methods,
which
means
the
number
of
tunable
properties goes higher in SFE. Thus,
the tunable properties of SFE make this process
more
unique, sensitive and specific in
compared with conventional extraction methods [8].
It
says
that
the
main
technical
feature
of
SFE
is
the
use
of
SF
at
the
critical
temperature and the
critical pressure, which have the ability to
dissolve many substances.
The almost liquid-like density of
supercritical fluids promotes solubility, and the
gas-like
viscosity and diffusivity make
extraction and purification faster compared to
extraction and
purification by
conventional (liquid) solvents [9]. In addition,
supercritical fluids have no
interfacial
surface
tension,
because
of
the
absence
of
liquid/gas
phase
boundary
in
supercritical state. High product
quality can be accomplished by fine-tuning
pressure and
temperature conditions of
the supercritical fluid. The extraction can be
selective to some
extent
by
controlling
the
density
of
the
medium
and
the
extracted
material
is
easily
recovered
by
simply
depressurizing,
allowing
the
supercritical
fluid
to
return
to
the
gas
phase
leaving
no
or
little
solvent
residues.
Temperature
increases
lead
to
the
improved
extraction capabilities of more
traditional techniques such as Soxhlet extraction.
The new
generation of enhanced
extraction technologies is based on the use of
temperatures above
the atmospheric
boiling point of the extracting solvent. In SFE,
pressure is applied to the
extraction
system so that these high temperatures (critical
temperatures) can be achieved.
Thus,
the
specific
components
can
be
isolated
from
a
liquid
or
a
solid.
Further,
supercritical extracts were often
recognized of superior quality when compared with
those
produced
by
hydro-distillation
or
liquid-solid
extraction.
The
common
SCF
are
carbon
dioxide
(CO
2
),
ammonia,
ethylene,
propylene,
and
water
etcetera.
Compared
with
traditional
separation
methods,
SFE
is
of
high
speed
on
separation
and
high
extraction
efficiency. SCF possess dual
characteristics of both gas and liquid. With a
strong ability to
dissolve,
smooth
flowing
property
and
delivery
performance,
it
?
s
easy
to
adjust
the
extraction
process.
Its
low
power
consumption
making
it
suitable
for
the
extraction
and
purification of the less volatile and
heat-sensitive substances.
Supercritical CO
2
is selective, there is no associated waste
treatment of a toxic solvent,
and
extraction times are moderate. SFE has
traditionally focused on carbon dioxide as the
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