Optimization of basic catalyst with ammoniated polyethylene glycol for the removal of naphthenic acid from petroleum crude oil by Box–Behnken design

Abstract

Naphthenic acid (NA) removal from petroleum crude oil was investigated and optimized through the utilization of a formulated basic chemical and a basic catalyst. The response surface method (RSM) by Box-Behnken design (BBD) was employed for this purpose. Ammoniated polyethylene glycol (NH3-PEG) and cerium oxide supported on alumina were selected as the basic chemical and basic catalyst, respectively. Synthesizing of the catalyst was conducted through the wet impregnation method, and calcination was performed at temperatures of 400, 700, and 1000 A degrees C. Brunauer-Emmett-Teller analysis (BET), field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), and X-ray diffraction analysis (XRD) were employed for characterizing the catalyst. A preliminary study revealed that the finest catalytic activity was achieved with the calcination of the Ce/Al2O3 catalyst at 1000 A degrees C with a NH3-PEG concentration of 1000 mg/L and a percentage of NH3-PEG/oil mass ratio of 0.40. The optimization of the parameters, which comprise catalyst calcination temperature, concentration of NH3-PEG, and the percentage of NH3-PEG/oil mass ratio on the deacidification of NA, was achieved through the utilization of the response surface method (RSM) by BBD. The optimal conditions were realized at a catalyst calcination temperature of 1,050.54 A degrees C, a NH3-PEG concentration of 853.10 mg/L, and a percentage of NH3-PEG/oil mass ratio of 0.47. With a 0.41 % margin of error, the results from RSM were deemed in good agreement with the experimental values.

Full text

Removal
of
naphthenic
acids
from
high
acidity
Korean
crude
oil
utilizing
catalytic
deacidification
method
Nurasmat
Mohd
Shukri,
Wan
Azelee
Wan
Abu
Bakar *,
Jafariah
Jaafar,
Zaiton
Abdul
Majid
Department
of
Chemistry,
Faculty
of
Science,
Universiti
Teknologi
Malaysia,
81310
UTM
Johor
Bahru,
Malaysia
Introduction
The
presence
of
naphthenic
acids
(NAs)
compounds
contributes
to
the
acidity
of
crude
oils
and
is
one
of
the
major
sources
of
corrosion
in
oil
pipelines
and
distillation
units
in
oil
refineries
[1,2].
Consequently,
crude
oils
with
high
NAs
concentrations
are
considered
to
be
of
poor
quality
and
marketed
at
a
lower
price
[3].
Total
acid
number
(TAN)
is
defined
as
the
number
of
milligrams
of
potassium
(KOH)
required
to
neutralize
the
acid
in
one
gram
of
oil,
and
a
commonly
accepted
criterion
for
the
oil
acidity,
although
the
correlation
with
corrosive
behavior
is
still
controversial
[4].
The
removal
of
NAs
from
crude
oil
is
regarded
as
one
of
the
important
processes
in
heavy
oil
upgrading.
Current
industrial
practices
either
depend
on
dilution
or
caustic
washing
methods
to
reduce
the
TAN
number
of
heavy
crude
oils
[5].
However,
neither
of
these
approaches
is
entirely
satisfactory.
For
instance,
blending
a
high
TAN
crude
oil
with
a
low
TAN
one
may
reduce
the
NAs
content
to
an
acceptable
level,
but
the
acidic
compounds
still
remain.
Caustic
treatment
can
substantially
remove
NAs,
but
the
process
generates
significant
amounts
of
wastewater
and
emulsion
that
are
problematic
to
treat.
In
particular,
once
an
emulsion
is
formed,
it
is
very
difficult
to
remove.
Catalytic
removal
of
NAs
has
been
studied
for
many
years.
It
has
been
reported
that
transition
metal
catalyst
could
reduce
the
acidity
of
crude
oil
under
the
hydrogen
atmosphere
but,
this
process
consumes
large
amount
of
hydrogen
[6]
and
it
has
not
been
commercialized
yet.
Alkaline
earth
metal
oxides
had
been
reported
by
Ding
et
al.
[7]
which
decomposed
the
NAs
in
crude
oil
and
substantially
reduce
the
acidity
of
crude
oil
through
the
decarboxylation
reaction
using
zinc
oxide
(ZnO)
as
catalyst;
however
this
is
a
destructive
method.
Shohaimi
et
al.
[8]
used
Ca
and
Ba
oxide
as
basic
catalysts
and
ammoniated
ethylene
glycol
as
acid
removal
agent
to
remove
the
NAs
in
crude
oil,
unfortunately
this
method
requires
high
concentration
of
basic
chemical
in
order
to
lower
the
TAN
value
below
than
one.
In
addition,
the
use
of
dual
chemical
(ammonia-ethylene
glycol)
is
limited
for
reduction
of
lower
TAN
value
crude
oil.
Catalytic
esterification
was
also
introduced
by
Wang
et
al.
[9]
to
remove
NAs
from
crude
oil
sample
by
converting
the
NAs
to
naphthenate
ester
utilizing
tin
oxide
(SnO)
catalyst.
However,
this
method
requires
higher
reaction
temperature
for
a
successful
catalytic
esterification.
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
A
R
T
I
C
L
E
I
N
F
O
Article
history:
Received
30
December
2014
Received
in
revised
form
5
February
2015
Accepted
7
February
2015
Available
online
12
February
2015
Keywords:
Naphthenic
acids
Korean
crude
oil
Total
acid
number
NH
3
–PEG
Basic
catalyst
A
B
S
T
R
A
C
T
Catalytic
deacidification
is
a
fascinating
method
to
decrease
the
naphthenic
acids
(NAs)
concentration
of
highly
acidic
petroleum
crude
because
these
acids
caused
serious
corrosion
in
refinery
equipment.
Korean
crude
oil
with
a
total
acid
number
(TAN)
of
8.32
mg
KOH/g
was
used
to
test
the
performance
of
catalytic
deacidification
technology.
A
basic
chemical
with
a
dosing
of
4%
ammonia
solution
in
polyethylene
glycol
(NH
3
–PEG)
was
used
as
the
acid
removal
agent
with
concentrations
of
100,
500,
and
1000
mg/L.
Cerium
oxide,
zinc
oxide
and
tin
oxide
based
catalysts
supported
onto
alumina
prepared
with
different
calcination
temperatures
and
types
of
dopants
were
used
to
aid
in
the
deacidification
reaction.
The
potential
catalyst
was
characterized
by
BET,
EPR
and
CO
2
-TPD
for
its
physicochemical
properties.
The
results
showed
93.3%
reduction
for
Korean
crude
oil
using
Cu/Ce
(10:90)/Al
2
O
3
calcined
at
1000
8C.
This
catalyst
has
the
highest
BET
surface
area
of
87.12
m
2
/g
with
higher
dispersion
of
Cu
2+
species
on
the
CeO
surface
detected
using
EPR
spectra
and
higher
total
basic
site
measured
using
CO
2
-TPD.
These
properties
contributed
to
the
excellent
catalytic
performance
which
remove
the
NAs
in
the
Korean
crude
oil
and
concurrently
reduced
the
TAN
value
below
than
one.
ß
2015
The
Korean
Society
of
Industrial
and
Engineering
Chemistry.
Published
by
Elsevier
B.V.
All
rights
reserved.
*Corresponding
author.
Tel.:
+60
13
746
6213.
E-mail
address:
wazelee@kimia.fs.utm.my
(W.A.W.A.
Bakar).
Contents
lists
available
at
ScienceDirect
Journal
of
Industrial
and
Engineering
Chemistry
jou
r
n
al
h
o
mep
ag
e:
w
ww
.elsevier
.co
m
/loc
ate/jiec
http://dx.doi.org/10.1016/j.jiec.2015.02.005
1226-086X/ß
2015
The
Korean
Society
of
Industrial
and
Engineering
Chemistry.
Published
by
Elsevier
B.V.
All
rights
reserved.

Presently,
there
are
no
works
documented
for
the
rare
earth
metal
which
is
cerium
oxide
(CeO)
being
used
as
catalyst
for
the
removal
of
NAs
in
crude
oil
sample.
It
is
well
established
that
cerium
oxide
is
one
of
the
potential
catalyst
in
the
redox
reaction
that
enhance
the
catalytic
activity
due
to
unique
acid-
base
properties
and
high
oxygen
storage
capability/mobility
and
strong
metal-support
interaction.
This
makes
the
CeO
based
materials
very
interesting
for
catalysis
studies
[10,11].
Accord-
ingly,
the
objective
of
this
study
is
to
develop
a
low-temperature
and
cost
effective
method
to
remove
NAs
from
crude
oil
by
using
a
chemical
treatment
with
the
aid
of
suitable
catalyst
to
enhance
the
catalytic
deacidification
process.
CeO,
ZnO
and
SnO
as
based
catalysts
and
manganese
(Mn),
cobalt
(Co),
nickel
(Ni)
and
copper
(Cu)
as
dopants
supported
on
alumina
were
selected
to
evaluate
their
effectiveness
towards
the
removal
of
NAs
and
at
the
same
time
lowering
the
TAN
in
Korean
crude
oil
below
than
one.
Experimental
Materials
In
this
study
the
materials
were
purchased
from
QRe
¨C
TM
and
used
as
supplied.
2-Propanol
and
toluene
were
used
as
solvent
extraction.
Ammonia
solution
28%
combined
with
polyethylene
glycol
was
used
as
deacidifying
agents.
The
indicator
used
in
the
deacidification
study
was
phenolphthalein
solution,
1%
(w/v)
in
ethanol.
Potassium
hydroxide
pellets
and
barium
hydroxide
were
used
as
titrants.
Preparation
of
catalyst
CeO,
ZnO
and
SnO
as
based
catalyst
were
used
in
this
work.
Manganese,
cobalt,
nickel,
and
copper
acted
as
dopant
were
used
to
investigate
the
effect
of
type
of
based
and
dopant
on
the
catalytic
deacidification
activity.
The
ratio
of
based-dopant
used
was
10
(dopant)
to
90
(base).
Calcination
temperatures
of
400
8C,
700
8C,
and
1000
8C
were
used.
The
metal
precursors
used
in
this
research
were
nitrate
salts
for
Ce,
Mn,
Co,
Ni,
Cu
and
Zn
and
chloride
salts
for
Sn
based
catalyst.
Generally,
all
the
samples
in
this
research
were
prepared
by
aqueous
incipient
wetness
impregnation
method
[8].
Each
of
the
metal
salts
was
weighed
in
a
beaker
according
to
the
desired
ratio
and
dissolved
in
small
amount
of
distilled
water.
Then,
the
solutions
were
mixed
together
and
stirred
continuously
by
magnetic
bar
for
30
min
at
27
8C
to
homogenize
the
mixture.
The
alumina
(Al
2
O
3
)
used
as
support
material
was
immersed
into
the
catalysts
solution
for
1
h
and
the
supported
catalysts
were
transferred
onto
an
evaporating
dish
lined
with
glass
wool.
It
was
then
aged
inside
an
oven
at
80–90
8C
for
24
h
to
remove
water
and
allow
good
coating
of
the
metal
on
the
surface
of
the
support.
This
was
then
followed
by
calcination
in
the
furnace
at
400
8C
for
5
h
using
a
ramp
rate
of
5
8C/min
in
order
to
eliminate
all
the
metals
precursor,
excess
water
and
impurities.
Similar
procedure
was
repeated
for
the
other
based
and
dopant
and
catalyst
calcination
temperature.
The
preparation
of
the
best
catalyst
was
then
further
optimized
at
temperatures
of
900
8C
and
1100
8C.
Catalysts
characterization
The
catalyst
surface
area
was
determined
by
using
Brunauer–
Emmett–Teller
(BET).
The
paramagnetic
properties
of
catalyst
were
characterized
by
Electron
Paramagnetic
Resonance
(EPR)
analysis
using
a
JEOL
spectrometer
interfaced
to
a
PC
for
data
acquisition
and
analysis.
The
EPR
was
operated
with
a
center
field
of
2500
G,
modulation
amplitude
of
4.00,
a
time
constant
of
0.25
s,
a
scan
time
equal
to
4
min,
and
a
microwave
power
of
20
mW.
The
total
basicity
measurement
of
the
catalyst
was
carried
out
using
CO
2
-TPD
(Thermo
Scientific).
The
sample
was
cleaned
under
helium
(He)
gas
flow
of
20
cm
3
/min
at
150
8C
for
60
min.
The
temperature
was
then
decreased
down
to
45
8C
prior
to
the
next
step.
CO
2
gas
(100%)
was
flowed
through
the
sample
at
45
8C
for
60
min
to
presaturate
the
active
sites
of
CO
2
.
The
gas
flow
was
changed
to
He
gas
(20
cm
3
/min)
for
another
60
min
at
80
8C
to
remove
weak
physisorbed
CO
2
from
the
surface
of
the
samples.
The
temperature
was
subsequently
ramped
down
to
45
8C
before
the
TPD
step.
TPD
was
carried
out
by
ramping
the
temperature
to
900
8C
at
10
8C/min
and
held
for
10
min
while
the
TPD
response
was
recorded.
Mass
spectrometric
data
was
also
recorded
for
this
TPD
experiment.
Feedstock
and
basic
chemical
The
feedstock
used
in
this
study
was
Korean
crude
oil
which
is
highly
acidic
with
TAN
of
8.32
mg
KOH/g
and
high
viscosity
as
it
freezes
at
the
ambient
temperature
of
27
8C.
Ammonia
solution
in
polyethylene
glycol
with
the
molecular
weight
PEG
of
2000
was
used
as
the
acid
removal
agent
in
the
deacidification
process.
The
concentrations
of
ammonia
solution
in
polyethylene
glycol
were
100,
500
and
1000
mg/L.
Preparation
of
4%
NH
3
–PEG
Ammonia
solution
(40
m
L)
was
added
dropwise
into
an
ice-
soaked
sample
bottle
which
contained
9.96
mL
of
polyethylene
glycol.
The
mixture
was
stirred
vigorously
with
a
magnetic
bar
for
an
hour.
The
reaction
of
NH
3
with
PEG
to
form
NH
3
–PEG
was
hastened
by
the
cold
surrounding.
The
solution
then
was
ready
to
be
blended
with
the
crude
oil
for
catalytic
deacidification
reaction.
The
solution
was
transferred
and
kept
in
a
dark
bottle
to
evade
sunlight.
Total
acid
number
(TAN)
determination
A
0.2
g
Korean
crude
oil
sample
was
measured
and
placed
in
a
titration
beaker.
The
titration
solvent,
40
mL
with
a
mixture
of
toluene:2-propanol:distilled
water
(50:49.5:0.5)
was
poured
into
the
crude
oil
sample
in
the
titration
beaker.
A
4%
NH
3
–PEG,
100
mg/L
was
added
into
an
approximately
0.1–0.15
g
crude
oil
sample
with
the
prepared
catalyst.
The
solution
was
heated
to
35–40
8C
to
stimulate
the
catalyst
in
the
mixture.
The
petroleum
crude
oil
sample
was
then
titrated
with
potassium
hydroxide
solution
(0.01
mol/L).
Total
acid
number
value
for
Korean
crude
(TAN
=
8.32
mg
KOH/g)
was
determined
by
semi-micro
color
indicator
titration
method.
The
indicator
used
was
phenol-
phthalein
solution,
0.1
mL
where
the
stable
red
color
was
observed
and
indicated
the
end-point
for
the
titration
method.
The
titration
method
was
performed
on
Korean
crude
oil
before
and
after
the
catalytic
deacidification
technology.
In
order
to
express
the
results,
TAN
value
of
the
sample
was
calculated
in
milligrams
of
potassium
hydroxide
per
gram
of
sample
(mg
KOH/g)
by
using
the
following
equation:
TAN
¼56:1

c

V
KOH

V
B
ð
Þ
m(1)
where
56.1
is
the
molecular
weight
of
KOH
in
g/mol,
c
is
the
concentration
in
mol/L,
of
standard
volumetric
KOH
solution,
V
KOH
is
the
volume
in
mL,
of
titrant
required
for
the
determination,
V
B
is
the
volume
in
mL,
of
titrant
required
for
the
blank
test,
and
m
is
the
mass
in
grams,
of
the
test
portion.
N.M.
Shukri
et
al.
/
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
111

Results
and
discussion
Deacidification
reaction
without
catalyst
TAN
value
for
Korean
crude
oil
was
determined
for
triplicate
samples
due
to
the
unhomogenous
distribution
of
NAs
in
the
crude
oil,
and
a
value
of
8.32
mg
KOH/g
was
obtained.
A
high
TAN
value
of
this
crude
represents
a
higher
number
of
acid
content
in
the
crude
oil.
The
ammonia
solution
in
polyethylene
glycol
with
concentra-
tions
of
100,
500,
and
1000
mg/L
were
synthesized.
The
concentrations
of
NH
3
–PEG
used
were
100,
500,
and
1000
mg/L
and
the
percentage
of
NH
3
in
PEG
per
crude
oil
mass
ratio
of
4
was
used.
As
proven
by
Shohaimi
et
al.
[8]
and
Wang
et
al.
[12],
the
amount
of
NH
3
content
in
crude
oil
at
4%
was
sufficient
enough
to
accomplish
maximum
removal
of
NAs
from
crude
oils
sample.
The
reaction
between
NH
3
–PEG
and
NAs
in
the
crude
oil
produced
water
and
salts.
Fig.
1
shows
the
effect
of
NH
3
–PEG
in
different
concentrations
to
the
TAN
value
reduction.
As
the
concentration
of
NH
3
–PEG
increased,
the
TAN
of
Korean
crude
decreased
from
8.32
to
5.61
mg
KOH/g.
Even
though
the
TAN
value
of
Korean
crude
showed
a
decreasing
trend,
but
it
did
not
meet
the
PETRONAS
requirement
for
TAN
to
be
less
than
one.
Thus,
in
order
to
completely
neutralize
the
acid
in
Korean
crude,
the
effect
of
ammonia
solution
dosing
aided
by
a
catalyst
need
to
be
investigated.
Catalytic
deacidification
reaction
Effect
of
different
based
catalyst
and
calcination
temperatures
of
catalyst
on
the
TAN
value
reduction
A
series
of
catalyst
was
synthesized
to
aid
in
the
deacidifica-
tion
reaction
for
the
removal
of
NAs.
A
series
of
CeO,
ZnO
and
SnO
based
catalysts
were
prepared
using
wetness
impregnation
method
supported
onto
alumina
followed
by
various
calcination
temperatures
at
400,
700,
and
1000
8C
for
5
h.
For
the
catalytic
activity
reaction
in
the
deacidification
process,
the
favorable
temperature
used
was
35–40
8C
because
the
main
components
in
crude
may
vaporize
at
temperature
above
40
8C
as
reported
by
Shohaimi
et
al.
[8].
Thus,
it
is
not
reasonable
for
the
chemical
treatment
to
be
above
this
temperature;
otherwise
some
types
of
NAs
may
start
to
vaporize.
Moreover,
the
chemical
composition
did
not
change
at
the
range
of
treatment
temperature.
Fig.
2a–c
illustrates
the
effect
of
different
based
oxide
catalyst
and
catalyst
calcination
temperature
on
the
TAN
reduction
for
Korean
crude
oil.
CeO
calcined
at
1000
8C
is
the
best
catalyst
that
reduced
the
TAN
in
Korean
crude
oil
by
56.13%
(TAN
=
3.65
mg
-
KOH/g)
when
used
with
1000
mg/L
of
NH
3
–PEG.
A
TAN
value
of
4.21
mg
KOH/g
was
obtained
by
SnO
based
catalyst
and
indicating
this
catalyst
being
the
least
effective
among
the
tested
catalyst.
Excellent
redox
properties
of
CeO
is
due
to
the
very
fast
reduction
of
Ce
4+
/Ce
3+
as
reported
by
Toemen
et
al.
[11]
which
is
correlated
with
the
formation
of
oxygen
vacancies
at
the
surface,
making
the
NAs
removal
more
efficient
and
gave
the
lowest
TAN
value.
Thus,
Ce
calcined
at
1000
8C
was
chosen
as
the
potential
based
catalyst
in
this
study.
Effect
of
type
of
dopant
on
catalytic
deacidification
reaction
Cerium
was
the
best
metal
oxide
to
act
as
a
based
catalyst
for
the
catalytic
deacidification.
Nevertheless,
the
TAN
value
was
still
higher
than
one.
Hence,
a
series
of
transition
metal
of
Mn,
Co,
Ni
and
Cu
was
used
to
serve
as
dopant
to
test
its
effectiveness
towards
the
catalytic
activity
performance.
The
ratio
of
the
dopant
to
base
was
10:90
and
the
reaction
temperature
of
35–40
8C
was
used
and
the
prepared
catalysts
were
calcined
at
1000
8C.
Basically,
a
dopant
acts
as
a
promoter
which
increases
the
catalytic
activity
by
modifying
the
surface
properties
of
catalyst
such
as
increasing
the
surface
area
of
active
sites,
dispersion
of
metal
on
the
catalyst
surface
and
increase
the
basic
or
acidic
properties
of
the
catalyst.
Ayastuy
et
al.
[13]
reported
that
a
promoter
will
enhance
the
catalytic
activity
more
than
the
monometallic
catalyst.
Fig.
3
displays
the
descending
trend
of
the
TAN
value
from
Mn,
Co,
Ni
and
the
higher
TAN
value
reduction
attained
by
Cu
as
dopant
for
this
study.
This
suggests
that
a
synergism
occurs
between
metals
and
CeO,
which
may
possibly
assist
in
the
cleavage
of
C–C
bonds
due
to
the
presence
of
Cu.
Moreover,
as
verified
by
Ayastuy
et
al.
[13]
the
higher
catalytic
activity
of
this
catalyst
is
based
on
the
high
oxygen
mobility
capacity
of
the
fluorite-type
and
the
synergism
between
copper
and
cerium
oxide,
related
to
the
Ce
4+
+
Cu
1+
$
Ce
3+
+
Cu
2+
redox
system,
which
gave
high
oxygen
storage
capacity.
Shohaimi
et
al.
[8]
also
reported
that
Cu
was
the
most
suitable
dopant
for
NAs
removal
from
crude
oil
sample.
Optimization
of
catalytic
deacidification
reaction
Optimization
of
catalyst
The
most
potential
catalyst
in
this
study
was
Cu/Ce
(10:90)/
Al
2
O
3
calcined
at
1000
8C.
This
catalyst
was
then
optimized
based
on
their
calcination
temperatures;
900
8C
and
1100
8C
in
order
to
find
its
optimum
calcination
temperature
that
gave
a
great
impact
on
the
deacidification
reaction
in
order
to
reduce
the
TAN
in
crude
oil
sample
to
a
TAN
value
less
than
one.
Fig.
4
shows
that
the
best
calcination
temperature
was
at
1000
8C
as
the
TAN
value
obtained
was
2.81
mg
KOH/g
with
a
percentage
reduction
of
66.23%
utilizing
NH
3
–PEG
concentration
of
1000
mg/L
for
the
catalytic
deacidification
of
Korean
crude
oil.
Increasing
the
catalyst
calcination
temperature
to
1000
8C
gave
an
increased
reduction
of
TAN
in
crude
oils
because
of
the
larger
surface
area
obtained
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
using
BET
analysis
which
provides
more
surface
area
for
catalytic
activity
to
occur
effectively.
Furthermore,
EPR
spectra
for
Cu/Ce
(10:90)/
Al
2
O
3
catalyst
at
1000
8C
showed
higher
dispersion
of
copper(II)
species
on
cerium
oxide
supported
on
alumina,
and
also
more
basic
sites
was
detected
using
CO
2
-TPD
on
this
catalyst
compared
to
other
calcination
temperatures.
These
are
the
reasons
for
the
higher
catalytic
deacidification
activity.
This
suggests
that
a
synergism
occurs
between
metals
and
CeO,
which
may
possibly
involve
in
the
cleavage
of
C–C
bonds
due
to
the
presence
of
Cu.
Cerium
is
amphoteric
in
nature,
an
addition
of
a
basic
dopant
will
lead
to
a
basic
catalyst.
In
this
work,
copper
(Cu
2+
)
was
used
8.32
5.61
0
1
2
3
4
5
6
7
8
9
0 mg/L
100 mg/L
500 mg/L
1000 mg/L
TAN, mg KOH/g
[NH3-PEG],
mg/L
Fig.
1.
TAN
reduction
of
Korean
crude
oil
by
using
various
dosing
concentrations
of
4%
NH
3
–PEG.
N.M.
Shukri
et
al.
/
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
112

to
induce
the
basicity
of
the
cerium
as
based
oxide
catalyst
that
lead
to
the
moderate
basic
catalyst.
Since
NAs
is
a
weak
acid,
a
moderate
basic
surface
of
the
catalyst
is
superior
to
deacidify
the
NAs.
The
worst
catalyst
was
the
one
calcined
at
1100
8C
using
1000
mg/L
of
NH
3
–PEG
showing
a
TAN
reduction
from
8.32
to
3.65
mg
KOH/g
(56.13%).
This
is
associated
with
smallest
surface
area
as
measured
using
BET
analysis.
Moreover,
EPR
spectra
showed
the
presence
of
bulky
form
of
Cu
2+
which
leads
to
poor
performance
of
deacidification
activity
for
this
catalyst.
Also,
the
total
basicity
sites
for
this
catalyst
as
recorded
by
CO
2
-TPD
were
the
least
amount.
Energy
Dispersive
X-ray
(EDX)
analysis
conducted
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C
showed
the
amount
of
total
Cu
and
Ce
on
the
alumina
support
was
0.00376
based
on
the
three
beads
(0.01128
g)
used.
Thus,
the
loading
of
the
total
catalyst
metal/Ce/Al
2
O
3
with
respect
to
the
mass
of
the
oil
(0.0564:1)
was
used
in
this
study.
Optimization
of
combined
basic
(co-basic)
chemical
agent
Although
the
TAN
value
for
Korean
crude
can
be
reduced
to
2.81
mg
KOH/g
from
an
initial
TAN
of
8.32
mg
KOH/g
using
4%
NH
3
–PEG
with
the
aid
of
the
most
potential
catalyst
which
is
Cu/
Ce
(10:90)/Al
2
O
3
calcined
at
1000
8C.
The
requirement
of
PETRONAS
for
TAN
to
be
lower
than
one
was
still
not
achieved.
Therefore,
a
combined
basic
chemical
agent
known
as
co-basic
chemical
agent
consisting
of
KOH
and
4%
NH
3
–PEG
was
fabricated
and
prepared
to
tackle
this
problem.
From
previous
study
[8],
it
stated
that,
addition
of
KOH
solution
alone
as
a
basic
chemical
would
lead
to
a
serious
emulsion
problem
to
the
crude
oil
sample
after
treatment.
In
this
study,
a
minimum
amount
of
concentrated
KOH
was
injected
into
the
basic
chemical
solution
to
increase
the
basicity
of
the
basic
chemical
solution.
Accordingly,
a
co-basic
chemical
with
various
percentages
(1–5%)
10
M
KOH
was
added
into
the
4%
NH
3
–PEG
solution
to
obtain
the
optimum
concentration
that
could
reduce
TAN
below
4.44
8.32
4.77 5.33
0
1
2
3
4
5
6
7
8
9
0 mg/L
100 mg
/L
500 mg/L
1000 mg/L
Ce oxide based Zn
oxide based
Sn oxide
baseda)
3.93
8.32
4.44 4.77
0
1
2
3
4
5
6
7
8
9
0 mg/L
100 mg/L 500
mg/L
1000 mg/L
Ce oxide based Zn
oxide ba
sed Sn
oxide based
b)
3.65
8.32
3.93 4.21
0
1
2
3
4
5
6
7
8
9
0 mg
/L
100 mg/L 500
mg/L
1000
mg/L
Ce oxide based Zn
oxide ba
sed Sn
oxide based
c)
TAN, mg KOH/g
TAN, mg KOH/g
[NH3-PEG], m
g
/L
[NH3-PEG], m
g
/L
[NH3-PEG], m
g
/L
TAN, mg KOH/g
Fig.
2.
TAN
reduction
of
Korean
crude
oil
by
using
various
metal
oxide
catalyst
using
different
concentration
of
NH
3
–PEG
at
calcination
temperature
of
(a)
900
8C,
(b)
1000
8C
and
(c)
1100
8C
at
reaction
temperature
of
35–40
8C.
Fig.
3.
TAN
reduction
of
Korean
crude
oil
by
using
several
dopants
using
Ce
oxide
as
based
catalyst
with
different
concentration
of
NH
3
–PEG
at
reaction
temperature
of
35–40
8C.
N.M.
Shukri
et
al.
/
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
113

than
one.
Concentrated
KOH
was
used
in
this
experiment
in
order
to
minimize
the
amount
of
the
KOH
solution
injected
into
the
basic
chemical
solution
and
at
the
same
time
to
prevent
emulsion
problem.
Surprisingly,
upon
the
addition
of
co-basic
chemical
aided
by
a
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C,
the
TAN
value
was
successfully
reduced
to
0.56
mg
KOH/g.
The
optimum
concentration
to
reduce
the
TAN
value
below
than
one
was
found
by
using
1%
of
10
M
KOH
+
4%
of
NH
3
–PEG
solution
with
a
93.3%
of
TAN
reduction.
Fig.
5
shows
a
dramatic
decreased
of
TAN
value
when
the
percentage
of
KOH
was
increased
from
0.2
to
1%
10
M
KOH
and
plateaued
at
1.2%.
This
proved
that
1%
of
10
M
KOH
is
suitable
to
be
added
in
the
4%
of
NH
3
–PEG
to
increase
the
basicity
of
basic
chemical
and
react
effectively
with
NAs
on
the
active
site
surface
provided
by
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C.
Characterization
of
a
potential
catalyst
Brunauer–Emmett–Teller
analysis
(BET)
analysis
One
of
the
most
important
physicochemical
properties
of
the
surface
of
a
solid
is
its
ability
to
adsorb
gases
and
vapors.
The
fresh
Cu/Ce
(10:90)/Al
2
O
3
at
various
calcination
temperature
of
900,
1000
and
1100
8C
catalyst
were
characterized
by
nitrogen
adsorption
analysis.
Table
1
summarizes
the
BET
surface
area
of
these
catalysts.
The
fresh
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C
gave
the
highest
surface
area
of
87.12
m
2
/g
followed
by
72.28
m
2
/g
for
the
same
catalyst
calcined
at
900
8C.
BET
surface
is
deem
to
surge
when
there
is
still
generation
of
new
active
sites
and
transformation
of
active
species
occurred
during
the
catalytic
reaction
[10].
Meanwhile,
fresh
Cu/Ce
(10:90)/
Al
2
O
3
calcined
at
1100
8C
gave
the
lowest
surface
area
of
16.85
m
2
/g.
When
the
catalyst
was
calcined
at
higher
tempera-
ture
(1100
8C),
the
catalyst
tends
to
generate
a
bulky
form
which
lead
to
a
decrease
in
the
surface
area
of
catalyst
as
shown
in
EPR
spectra
in
Fig.
6.
Therefore
Cu/Ce
(10:90)/Al
2
O
3
calcined
at
1000
8C
was
the
best
catalyst
due
to
larger
surface
area
formation
that
will
lead
to
increment
of
active
sites
and
thus
will
boost
the
catalytic
activity.
Electron
paramagnetic
resonance
(EPR)
analysis
EPR
analysis
is
a
very
effective
technology
to
identify
paramagnetic
Cu
2+
species
in
the
catalysts,
even
in
a
trace
amount
and
characterized
the
dispersed
Cu
2+
species
in
different
matrix
[13].
Detailed
studies
of
copper-based
catalysts
generally
revealed
the
existence
of
two
types
of
copper
species:
(i)
isolated
Cu
2+
ions
incorporated
into
or
on
the
catalyst
surface
and
localized
in
tetrahedral
or
octahedral
sites;
(ii)
CuO
clusters
or
particles
irregularly
distributed
on
the
catalyst
surface
[14].
For
EPR
analysis,
different
calcination
temperatures
of
Cu/Ce
(10:90)/Al
2
O
3
catalyst
were
investigated
and
the
spectra
are
shown
in
Fig.
6.
The
spectra
for
the
catalyst
at
both
calcination
temperatures
showed
a
single
peak
at
g
value
of
2.07
exhibiting
‘‘wings’’
on
both
sides
which
was
attributed
from
the
Cu
2+
ions
[14].
EPR
signal
of
the
catalyst
at
900
8C
and
1000
8C
appears
to
be
isotropic
with
indication
of
an
octahedron
structure
of
the
paramagnetic
Cu
2+
ion
[15]
and
exhibits
well
dispersed
Cu
2+
species
on
ceria
supported
alumina
surface
catalyst.
Higher
dispersion
of
Cu
2+
will
provide
a
bigger
surface
area
for
better
catalytic
deacidification
performance
as
calculated
by
Brunauer–
Emmett–Teller
(BET)
analysis
of
the
surface
area
of
Cu/Ce
(10:90)/
Al
2
O
3
catalyst
calcined
at
900
8C.
A
surface
area
value
of
72.28
m
2
/g
was
recorded,
and
generating
an
increased
to
87.12
m
2
/g
with
increasing
calcination
temperature
to
1000
8C.
This
characteristic
of
Cu
2+
species
contributed
to
the
enhancement
of
catalytic
8.32
3.37
0
1
2
3
4
5
6
7
8
9
0 mg/
L 100
mg/
L500
mg/
L10
00 mg/L
8.32
2.81
0
1
2
3
4
5
6
7
8
9
0 mg/
L
100 mg/
L
500 mg/
L1000
mg/L
b)
8.32
3.65
0
1
2
3
4
5
6
7
8
9
0 mg/
L
100
mg/
L50
0 mg/
L 1000
mg/L
a)
c)
TAN, mg KOH/g
TAN, mg KOH/g
TAN, mg KOH/g
[NH3-PEG],
mg/L
[NH3-PEG], mg/L
[NH3-PEG],
mg/L
Fig.
4.
TAN
reduction
of
Korean
crude
oil
by
using
Ce
oxide
as
based
catalyst
and
Cu
as
dopant
at
different
calcination
temperature
(a)
900
8C,
(b)
1000
8C
(c)
1100
8C
with
different
concentration
of
NH
3
–PEG
at
reaction
temperature
of
35–40
8C.
2.81
0.56
0
0.5
1
1.5
2
2.5
3
0.0 0.2 0.4 0.8 1.0 1.2
% of
KO
H
TAN, mg KOH/g
Fig.
5.
TAN
reduction
of
Korean
crude
oil
using
different
percentage
of
10
M
KOH
in
4%
NH
3
–PEG
aided
by
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C
using
reaction
temperature
of
35–40
8C.
Table
1
BET
surface
area
of
fresh
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
900
8C,
1000
8C
and
1100
8C
for
5
h.
Catalyst
calcination
temperature
(8C)
Surface
area
(m
2
/g)
1100
16.85
1000
87.12
900
72.28
N.M.
Shukri
et
al.
/
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
114

deacidification
activity
due
to
the
more
basic
sites
present
to
serve
for
an
effective
catalytic
activity.
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C
exhibited
lower
EPR
intensity
and
moreover
the
peak
was
broadened
and
the
g-value
slightly
shifted
to
higher
values
(2.50)
which
suggests
the
higher
presence
of
bulk
CuO,
as
compared
to
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
900
8C
and
1000
8C.
The
intensity
of
the
peak
observed
became
weaker
as
the
calcination
temperature
increased
which
implies
a
decreased
in
the
paramagnetic
properties
of
the
catalyst
and
bulk
form
of
Cu
2+
species
[13].
BET
analysis
gave
the
smallest
surface
area
value
of
16.85
m
2
/g
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C
due
the
presence
of
bulky
form
of
Cu
2+
when
the
catalyst
was
calcined
at
higher
temperature.
Smallest
surface
area
will
produce
smallest
basic
sites,
thus
hindering
the
catalytic
deacidification
activity.
This
is
probably
one
of
the
reasons
the
catalytic
deacidification
activity
become
lower
with
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C.
The
K
signal
for
which
the
hyperfine
structure
is
highly
resolved
has
been
attributed
to
a
pair
of
two
equivalent
copper(II)
ions
separated
by
a
distance
of
3.4
A
˚,
which
is
smaller
than
Ce–Ce
distance
of
5.41
A
˚,
in
the
ceria
lattice
indicating
that
one
cannot
have
two
Cu
2+
ions
at
two
nearby
substitutional
lattice
positions
[16].
Carbon
dioxide-temperature
programmed
desorption
(CO
2
-TPD)
analysis
The
basicity
measurements
of
Cu/Ce
(10:90)/Al
2
O
3
catalyst
were
carried
out
by
the
temperature
programmed
desorption
of
CO
2
.
Fig.
7
shows
the
CO
2
-TPD
curves
for
Cu/Ce/Al
2
O
3
catalyst
at
different
calcination
temperatures
of
900
8C,
1000
8C
and
1100
8C.
The
CO
2
uptakes
by
various
catalysts
with
different
basic
strengths
are
reported
in
Table
2.
The
TPD
results
also
suggested
that
the
strength
of
the
basic
sites
plays
a
crucial
role
in
determining
the
catalytic
activity
[17].
The
basicity
of
the
various
Cu/Ce
(10:90)/Al
2
O
3
catalyst
measured
by
the
CO
2
-TPD
method
was
found
to
increase
with
an
increase
in
calcination
temperature
up
to
1000
8C
and
decrease
with
further
increase
in
calcination
temperature
as
shown
in
Table
2.
The
CO
2
-spectra
recorded
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
900
8C
consists
of
two
lower
deconvulated
peaks
with
the
first
peak
is
centred
at
109.3
8C,
and
the
second
peak
at
235.1
8C.
The
highest
amount
of
CO
2
was
desorbed
from
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C
with
a
value
of
0.493.
The
CO
2
-TPD
pattern
of
this
catalyst
was
spanned
in
the
temperature
range
of
100–300
8C
and
consists
of
two
resolved
maxima.
The
first
peak
was
centred
at
127.6
8C,
while
the
maximum
of
the
second
one
was
at
243.1
8C.
There
were
three
unresolved
deconvulated
peaks
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C,
desorption
amount
of
CO
2
reached
a
maximum
at
306
8C
and
decreases
slowly.
Based
on
the
temperature
of
the
peak
for
desorbed
CO
2
molecule,
the
behavior
of
different
CO
2
species
during
the
course
of
desorption
from
Cu/Ce
(10:90)/Al
2
O
3
catalyst
was
determined.
Both
Cu/Ce
(10:90)/Al
2
O
3
catalyst
at
900
8C
and
1000
8C
calcination
temperatures
have
the
peak
in
the
range
of
109–243
8C
which
produced
the
mixture
of
unidentate
and
bidentate
carbonate
molecule.
A
new
form
of
carbonate
molecule
from
bidentate
to
inorganic
carboxylate
was
con-
verted
at
the
desorption
temperature
from
306–592.8
8C.
Thus,
the
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C
have
three
species
consisting
of
unidentate,
bidentate
and
inorganic
carboxylate.
Rao
et
al.
[17]
recorded
the
desorbed
peak
of
CO
2
being
deconvoluted
into
three
temperature
regions
which
can
be
classified
into
three
types
of
sites:
(i)
57–227
8C
is
weak
basic
sites,
(ii)
227–423
8C
is
moderate,
and
(iii)
>423
8C
corresponds
to
strong
basic
sites.
Both
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
900
8C
and
1000
8C
consists
of
weak
and
moderate
-750
-550
-350
-150
50
250
010
020
030
040
0
500 600
g
a=b
c
K
g
Intensity
Magnet
ic Fiel
d
Fig.
6.
ESR
spectra
of
Cu/Ce
(10:90)/Al
2
O
3
catalyst
at
calcined
at
(a)
900
8C,
(b)
1000
8C,
(c)
1100
8C
for
5
h.
-0.002
0
0.002
0.004
0.006
0.008
0.01
0.012
0
200 40
060
080
010
00
a
c
TCD Signal (A.U)
Tempe
ratur
e (oC)
b
Fig.
7.
CO
2
-TPD
curves
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
at
calcined
at
of
(a)
900
8C,
(b)
1000
8C,
(c)
1100
8C
for
5
h.
Table
2
Amount
of
CO
2
desorbed
for
fresh
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
900
8C,
1000
8C
and
1100
8C
for
5
h.
Catalyst
calcination
temperature
(8C)
Temperature
of
desorbed
peak
CO
2
(8C)
Quantity
of
desorbed
CO
2
(mmol/g)
Total
amount
of
desorbed
CO
2
(mmol/g)
900
109.3
0.030
0.379
235.1
0.349
1000
127.6
0.053
0.493
243.1
0.440
1100
125.0
0.002
0.097
306.0
0.066
592.8
0.029
N.M.
Shukri
et
al.
/
Journal
of
Industrial
and
Engineering
Chemistry
28
(2015)
110–116
115

basic
sites,
but
the
mixture
of
weak,
moderate
and
strong
basic
sites
was
found
for
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1100
8C.
Since
NAs
are
weak
acids,
the
catalyst
with
more
amount
of
weak
and
moderate
basic
sites
were
needed
to
aid
in
the
deacidification
reaction.
The
Cu/Ce
(10:90)/Al
2
O
3
catalyst
which
calcined
at
1000
8C
was
the
most
potential
catalyst
due
to
the
greater
amount
of
weak
and
moderate
basic
sites.
Conclusion
TAN
in
Korean
crude
oil
was
successfully
reduced
to
be
less
than
1
by
deacidification
reaction
of
the
crude
with
the
developed
base
chemical
which
are
ammonia
solution
in
polyethylene
glycol
with
the
addition
of
1%
10
M
KOH
as
co-
basic
removal
agent.
Cu/Ce
(10:90)/Al
2
O
3
catalyst
calcined
at
1000
8C
was
the
most
potential
catalyst
that
could
enhance
the
reduction
of
TAN
in
Korean
crude
oil.
As
the
NH
3
–PEG
concentration
is
increased,
the
acid
number
in
crude
sample
was
reduced.
Physical
characterization
by
BET
analysis
showed
that
this
catalyst
has
the
largest
surface
area.
EPR
analysis
exhibited
higher
dispersion
of
Cu
2+
species
on
the
Ce
surface
giving
higher
catalytic
activity
for
this
catalyst
and
CO
2
-TPD
profiles
proved
that
the
total
basic
sites
for
this
catalyst
was
the
highest
compared
to
the
same
catalyst
calcined
at
900
8C
and
1100
8C.
Acknowledgements
The
authors
gratefully
acknowledge
Universiti
Teknologi
Malaysia
(UTM),
Ministry
of
Education
(MOE),
for
the
financial
support
given
under
Fundamental
Research
Grant
Scheme
(FRGS,
Vote
no.:
4F225)
and
Ministry
of
Science,
Technology
and
Innovation
(MOSTI)
for
MyBrain
15
scholarship
to
Nurasmat
Mohd
Shukri.
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