36 - hydrocracking of used cooking oil for biofuels production
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8/12/2019 36 - Hydrocracking of Used Cooking Oil for Biofuels Production
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Hydrocracking of used cooking oil for biofuels production
Stella Bezergianni *, Aggeliki Kalogianni
Chemical Process Engineering Research Institute CPERI, Center for Research and Technology Hellas CERTH, 6th km Harilaou-Thermi Rd, 57001 Thermi, Thessaloniki, Greece
a r t i c l e i n f o
Article history:
Received 28 January 2009
Received in revised form 11 March 2009
Accepted 12 March 2009Available online 14 April 2009
Keywords:
Hydrocracking
Used cooking oil
Biofuels
a b s t r a c t
Hydrocracking of used cooking oil is studied as a potential process for biofuels production. In this work
several parameters are considered for evaluating the effectiveness of this technology, including hydro-
cracking temperature, liquid hourly space velocity (LHSV) and days on stream (DOS). Conversion and
total biofuels production is favored by increasing temperature and decreasing LHSV. However moderate
reaction temperatures and LHSVs are more attractive for diesel production, whereas higher temperatures
and smaller LHSVs are more suitable for gasoline production. Furthermore heteroatom (S, N and O)
removal increases as hydrocracking temperature increases, with de-oxygenation being particularly favor-
able. Saturation, however, is not favored with temperature indicating the necessity of a pre-treatment
step prior to hydrocracking to enable saturation of the double bonds and heteroatom removal. Finally
the impact of extended operation (catalyst life) on product yields and qualities indicates that all reactions
are affected yet at different rates.
2009 Elsevier Ltd. All rights reserved.
1. Introduction
The use of biofuels as an alternative source of transportation en-
ergy is promoted via national and international legislation and pro-
tective measures, as their production enhances sustainability and
economic growth. Biodiesel is the most common biofuel employed
in Europe and its production (mostly via transesterification) is
mainly based on raw vegetable oil (Panorama of Energy, 2007).
Vegetable oil is produced from oil based crops (rapeseed, soy-bean,
palm, sunflower etc.) which gives moderate yields per hectare.
Besides the importance of producing and using biofuels, there
are several considerations associated with the existing production
processes. The price and availability of the main byproduct glyc-
erin is both an economic but also environmental consideration.
Furthermore, existing technologies demand large biodiesel pro-
duction units which require large investments (Knothe et al.,
2005). However the most important consideration is the price
and availability of vegetable oil, the cost of which might reach up
to 75% of the total production cost (Phan and Phan, 2008). The lat-
ter can be compensated by employing used cooking oil collected
from restaurants and/or homes, the price of which is at least 23
times cheaper than virgin vegetable oils (Zhang et al., 2003).
Used cooking oil has been explored as a feedstock for biodiesel
production only via transesterification techniques. Alkali-catalyzed
transesterification of a single step (Phan and Phan, 2008; Meng
et al., 2008) or of a two step process ( Wang et al., 2007; Sharma
et al., 2008) gives high yields at moderate methanol/oil ratios
and mild temperatures. Another interesting technology is based
on heterogeneous solid catalyst-based transesterification (Cao
et al., 2008; Jacobson et al., 2008; Lou et al., 2008 ) which employs
more environmentally benign catalysts and is effective for used
cooking oil feedstocks, but requires higher temperatures. Enzy-
matic-catalysis-based transesterification exhibits significant yields
at moderate operating conditions (Yagiz et al., 2007; Halim et al.,
2009; Chen et al., 2009; Dizge et al., 2009) and shows significant
potential.
Catalytic hydroprocessing is an alternative technology for biofu-
els production technology which employs the existing infrastruc-
ture of petroleum refineries (Huber and Corma, 2007; Stumborg
et al., 1996), and has already several industrial applications (Neste
oil corporation, 2007; HPInnovations, 2006; Hayashi, 2008). The
technology has significant potential as the produced hydrotreated
vegetable oils have better fuel properties than the biodiesel pro-
duced via transesterification, and their use improves engine fuel
economy (Huber and Corma, 2007). Hydroprocessing of raw vege-
table oil heavy vacuum gas oil mixtures have been explored by
employing hydrotreating (Huber et al., 2007) and hydrocracking
(Bezergianni et al., 2009) catalysts at nominal operating conditions.
Nevertheless, this technology has only been applied to raw vegeta-
ble oil feedstocks.
This paper involves the investigation of used cooking oil as a
hydrocracking feedstock as well as the key parameters affecting
product yield and quality of such process. In particular the effect
of reactor temperature and liquid hourly space velocity (LHSV)
on product yields and quality are studied. Furthermore the depen-
dence of the hydrocracking effectiveness on the catalyst life (days
0960-8524/$ - see front matter 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2009.03.039
* Corresponding author. Tel.: +30 2310 498315; fax: +30 2310 498380.
E-mail address:sbezerg@cperi.certh.gr(S. Bezergianni).
Bioresource Technology 100 (2009) 39273932
Contents lists available at ScienceDirect
Bioresource Technology
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / b i o r t e c h
mailto:sbezerg@cperi.certh.grhttp://www.sciencedirect.com/science/journal/09608524http://www.elsevier.com/locate/biortechhttp://www.elsevier.com/locate/biortechhttp://www.sciencedirect.com/science/journal/09608524mailto:sbezerg@cperi.certh.gr -
8/12/2019 36 - Hydrocracking of Used Cooking Oil for Biofuels Production
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on stream) is also explored. It should be mentioned that it is the
first application of catalytic hydroprocessing on used cooking oil.
2. Methodology
The CPERI hydroprocessing unit is a small-scale pilot plant unit
which is employed for hydrotreating (HDS, HDN) and hydrocrack-
ing of various feedstocks, varying from light gas oil to heavy vac-
uum gas oil. This small-scale pilot plant consists of a feed
system, a reactor system and a product separation system, as sche-
matically depicted inFig. 1(Bezergianni et al., 2009).
The total liquid product is collected and several analyses can
take place in the analytical laboratory of CPERI. The simulated dis-
tillation curve is determined via an Agilent 6890 N-GC according to
the ASTM D-7213 procedure. The density of the total liquid prod-
uct is measured via an Anton-Paar density/concentration meter
DMA 4500 according to ASTM D-1052. The concentration of sulfur
and nitrogen is measured via an Antek 5000 system, according to
ASTM D5453-93 and ASTM D4629 procedures, respectively. Total
carbon concentration is measured via a CHN LECO 800 analyzer. Fi-
nally, hydrogen is measured via an Oxford Instruments NMR MQA
7020. Once total carbon, hydrogen, sulfur and nitrogen wt% are
determined, the oxygen concentration is indirectly determinedassuming its the only significant element contained in the product.
The aforementioned analyses are also performed for the feed-
stocks. The reaction gases are analyzed offline via a Hewlett-Pack-
ard 5890 Series II-GC equipped with two detectors, a Thermal
Conductivity Detector (TCD) and a Flame Ionization Detector
(FID). The TCD is used for the analysis of H2, CO, CO2, O2, N2 and
H2S while the FID is used for CH4 and C2C6, hydrocarbons.
For all experiments the same commercial hydrocracking cata-
lyst and feedstock were employed. The catalyst was pre-sulphided
according to the catalyst providers recommended procedure. Fur-
thermore, in order to maintain constant catalyst activity, DMDS
(Di-Methyl-Di-Sulfide) and TBA (Tetra-Butyl-Amine) were added
to achieve a specific sulfur and nitrogen concentration in each
feedstock. An experiment was considered complete when the reac-tions reached steady state, usually after 56 days on stream. This
was examined by monitoring the product density on a daily basis.
Once the product density was stabilized, the individual effects of
each experiment were considered stable and the study complete.
The product collected during the last day of each study was ana-
lyzed in detail, as it represented that particular condition.
In order to analyze the effectiveness of hydrocracking reactions,
hydrocracking conversion can be employed. Hydrocracking con-
version (%) is defined as the percentage of the heavy fraction of
feed which has been converted to lighter products during
hydrocracking:
Conversion % Feed360 Product360
Feed360100 1
where Feed360and Product360are the wt% of the feed and product,
respectively, which have a boiling point higher than 360 C.
Furthermore, in order to measure the hydrocracking effective-
ness towards the production of a particular product instead of
other products, the measure of selectivity is employed. Selectivity
can be defined for different products (ex diesel, gasoline etc.) based
on the boiling point range which defines these products. For exam-
ple, for a product with initial and final boiling points A and B,
respectively, selectivity is defined as:
Product selectivity% ProductAB FeedAB
Feed360 Product360 100 2
where Feed360and Product360are the wt% of the feed and product,
respectively, which have a boiling point higher than 360C (i.e. hea-
vy molecules of feed and product) and FeedAB and ProductAB are
the wt% of the feed and product, respectively, which have a boiling
point range betweenA and B degrees Celsius. From Eq.(2)selectiv-
ity can be defined for diesel (180360C), kerosene/jet (170
270C) and naphtha (40200 C).
3. Results
A series of experiments were conducted to study the effect of
reactor temperature and liquid hourly space velocity (LHSV) on
hydrocracking of used cooking oil. Moreover the effects of catalyst
deactivation are also explored. The feedstock employed was 100%
used cooking oil. The used cooking oil was mainly collected from
local restaurants, while smaller amounts (
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(with boiling point > 360 C) compose the unconverted part of the
feed that cannot be utilized as liquid biofuels. The product yields in
thisFig. 2indicate that as reactor temperature increases, the pro-
duced liquid biofuels (gasoline and diesel) increase. This is ex-
pected as hydrocracking activity rises with increasing
temperature. As it is evident from this figure, diesel yield is more
than seven times higher than the gasoline yield at all temperatures,
indicating that this technology is more suitable for diesel produc-tion rather than gasoline production. Furthermore gasoline yield
increases monotonically with temperature, while diesel yield is
smaller at the middle temperature (370 C). The minimum diesel
yield observed at 370 C is attributed to the fact that increasing
temperature causes not only heavy molecules but also diesel ones
are cracked into lighter molecules.
The conversion as well as the diesel, kerosene/jet and naphtha
selectivities for the three different hydrocracking temperatures is
depicted inFig. 3. The conversion and selectivities are calculated
from the simulated distillation data of the total liquid product of
each hydrocracking temperature (Table 2), using Eqs.(1) and (2)
respectively. As temperature increases, the conversion increases
from 73% (at 350 C) to 82% (at 390 C). This is an expected out-
come as hydrocracking activity is favoured with temperature.When comparing the product selectivities however, the results
are more interesting. Diesel selectivity has the most significant val-
ues (>90%), as diesel production is most favorable. In the mean
time kerosene/jet and naphtha selectivities are below 20%. Dieselselectivity however, is not favoured with temperature, while the
other two selectivities are clearly favoured. This is expected as
increasing temperature causes more intensive cracking thus not
only heavier molecules but also some diesel molecules are further
cracked into lighter molecules. Therefore milder hydrocracking
temperatures (350 and 370 C) promote diesel rather than kero-
sene/jet or naphtha production.
The hydrogenation effect on the hydrocracked product at the
three reactor temperatures is given inTable 3. Bromine index indi-
cates the presence of olefins or double bonds. According to this ta-
ble, the feed bromine index is significantly reduced for all products.
However the bromine index increases for increasing hydrocracking
temperature, signifying that the saturation of double bonds de-
creases as reactor temperature increases. Therefore catalyst activ-ity is primarily driven towards cracking or other reactions rather
than saturation, which indicates that a hydrotreatment step might
be necessary prior to hydrocracking. The same conclusion is drawn
from the C/H ratio also given in Table 3. The C/H ratio is signifi-
cantly dropped from feed to products. However the C/H ratio in-
creases as hydrocracking temperature increases, indicating that
saturation is not favored with temperature, compared to the other
hydrocracking reactions.
Besides cracking and saturation, heteroatom removal (mainly
sulfur, nitrogen and oxygen) is another group of reactions that take
place during hydrocracking. The concentration of S, N and O for the
hydrocracking feed and products (at the three reactor tempera-
tures) are given inTable 2. The heteroatom removal as percent of
its concentration in the feed for the three different temperaturesis compared inFig. 4. Clearly the efficiency of heteroatom removal
71 69 73
2 6
10
0
10
20
30
40
50
60
70
80
90
100
093073053
Reactor Temperature (deg C)
%o
ftotal
liquidproduct
Gasoline
Diesel
Fig. 2. Temperature effect on diesel and gasoline yield (as vol% of total liquid
product). All experiments were performed at P= 2000 psig (13789.5 kPa),
LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm3/m3).
Table 2
Effect of reactor temperature on product quality. All experiments were performed at
P= 2000 psig (13789.5 kPa), LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm3/m3).
Feed 350 C 370 C 390 C
Density (kgr/m3) 0.9011 0.7734 0.7758 0.7719
S (wppm) 27070 278.6 156.8 109.2
N (wppm) 551.70 1.95 1.31 0.10
H (wt%) 11.29 14.62 14.63 14.62
C (wt%) 73.37 83.49 84.78 84.90
O (wt%) 12.58 1.86 0.57 0.47
IBP (C) 298.2 147.0 101.2 124.0
5% (C) 526.6 268.8 195.8 171.6
10% (C) 565.0 284.2 270.6 201.0
20% (C) 600.6 300.0 289.0 268.0
30% (C) 605.2 303.2 302.8 287.6
40% (C) 608.4 304.6 305.2 299.0
50% (C) 610.2 306.4 306.6 304.6
60% (C) 611.8 316.4 318.2 309.8
70% (C) 613.0 328.4 331.4 318.6
80% (C) 614.0 434.0 397.6 346.8
90% (C) 617.8 461.8 459.6 409.0
95% (C) 641.2 474.0 474.8 457.8
FBP (C) 733.4 590.0 571.0 571.2
0
10
20
30
40
50
60
70
80
90
100
350 355 360 365 370 375 380 385 390
Reactor Temperature (deg C)
Convers
ion
/S
elec
tiv
ities
(%)
Conversion
Diesel SelectivityKero/Jet Selectivity
Naphtha Selectivity
Fig. 3. Conversion and selectivities at different hydrocracking temperatures. All
experiments were performed atP= 2000 psig (13789.5 kPa), LHSV = 1.5 h1 and H2/
oil = 6000 scfb (1068 nm 3/m3).
Table 3
Bromine index and carbon-to-hydrogen (C/H) ratio of hydrocracking feed and
products at three different reactor temperatures. All experiments were performed
at P= 2000 psig (13789.5 kPa), LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm3/m3).
Feed Product
350 C 370 C 390 C
Br index 49,100 158.2 224.4 425
C/H 6.499 5.711 5.795 5.806
S. Bezergianni, A. Kalogianni/ Bioresource Technology 100 (2009) 39273932 3929
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for all three species (S, N and O) is high and is increasing with
hydrocracking temperature. Deoxygenation is particularly favor-
able to hydrocracking temperature, as the oxygen removal percent
of oxygen contained in feed increases from 85.2% to 96.3% between
350 and 390 C.
3.2. Effect of LHSV
The Liquid Hourly Space Velocity (LHSV) is an important oper-
ating parameter for regulating catalyst effectiveness and also cata-
lyst life expectancy. The effect of LHSV on cracking is the main
premise of this analysis. This study on product quality and yields
was performed on hydrocracking of used cooking oil at five differ-
ent LHSVs, i.e. 0.5, 1, 1.5, 2 and 2.5 h1. For this study three differ-
ent experimental runs were employed using the same
hydrocracking catalyst (used also for the study described in Section
3.1) and the same operating parameters i.e. T= 370 C,
P= 2000 psig (13789.5 kPa), and H2/oil = 6000 scfb (1068 nm3/m3).
The product yields at the five different LHSVs are given inFig. 5.
The product yields in this figure are not as variable with LHSV as
they were in the case of reactor temperature (Fig. 2). However an
overall decreasing trend is observed with increasing LHSV, which
is expected, as increasing LHSV implies smaller residence time of
the feed in the catalyst section (reactor) and therefore smaller
reaction time. FromFig. 5it is evident that diesel yield is signifi-
cantly higher than gasoline yield at all LHSVs.
The conversion as well as the diesel, kerosene/jet and naphtha
selectivities for the five different LHSVs are presented in Fig. 6.
As temperature increases the conversion decreases from 80% (at
LHSV = 0.5 h1) to 74% (at LHSV = 2.5 h1). This conversion de-
crease for increasing LHSV is anticipated since high LHSVs result
in smaller reaction time. Regarding individual product selectivities,
on one hand the diesel selectivity exhibits once again the most sig-
nificant values (>93%). On the other hand the kerosene/jet and
naphtha selectivities are below 20% for all LHSVs. Furthermore die-
sel selectivity is favoured with LHSV while kerosene/jet and naph-
tha selectivities are not. This is also expected as increasing LHSV(therefore decreasing reaction time) causes less cracking and
therefore a smaller production of the lighter products (kerosene/
jet and naphtha). Therefore higher LHSVs (P1.5 h1) promote die-
sel than kerosene/jet or naphtha production.
3.3. Effect of catalyst life (days on stream)
The industrial hydrocracking unit run length is one of the most
crucial parameters of catalyst selection and is mainly limited by
Catalyst Life. Catalyst Life or Catalyst Aging is mostly attributedto extended operation or by blockage of active sites attributed to
80
82
84
86
88
90
92
94
96
98
100
350 355 360 365 370 375 380 385 390
Reactor Temperature (deg C)
He
teroa
tom
Remova
l(%o
ffee
d)
Sulphur
Nitrogen
Oxygen
Fig. 4. Heteroatom (sulfur, nitrogen and oxygen) removal at different hydrocrack-
ing temperatures. All experiments were performed at P= 2000 psig (13789.5 kPa),LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm
3/m3).
71 70 69 70 71
9 86 7 5
0
10
20
30
40
50
60
70
80
90
100
0.5 1 1.5 2 2.5
LHSV (1/hr)
%o
ftotal
liqu
idpro
duc
t
Gasoline
Diesel
Fig. 5. LHSV effect on diesel and gasoline yield (as vol% of total liquid product). All
experiments were performed at P= 2000 psig (13789.5 kPa), LHSV = 1.5 h1 and H2/
oil = 6000 scfb (1068 nm3/m3).
0
10
20
30
40
50
60
70
80
90
100
0.5 1 1.5 2 2.5
LHSV (1/hr)
Convers
ion
(%)
Conversion
Diesel Selectivity
Kero/Jet Selectivity
Naphtha Selectivity
Fig. 6. Conversion and Selectivities at different LHSVs. All experiments were
performed at T= 370 C, P= 2000 psig (13789.5 kPa) and H2/oil = 6000 scfb
(1068 nm3/m3).
72.62 73.97
81.88
73.6570.8072.72
0
10
20
30
40
50
60
70
80
90
100
390370350
Reactor Temperature (deg C)
%C
onvers
ion
RUN-A
RUN-B
9 DOS 26 DOS 16 DOS 34 DOS
23 DOS
37 DOS
Fig. 7. Effect of DOS on hydrocracking conversion at different hydrocracking
temperatures. All experiments were performed at P= 2000 psig (13789.5 kPa),
LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm3/m3).
3930 S. Bezergianni, A. Kalogianni/ Bioresource Technology 100 (2009) 39273932
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the feedstock components. As it is extremely important to antici-
pate typical reasons for deactivation, this study aims to assess this
technology during an early stage and a latter stage of the experi-
ment. For this analysis two experimental runs were employed
using the same hydrocracking catalyst (used also for the previous
studies described in Sections3.1 and 3.2) and the same operating
parameters i.e. T= 350, 370 and 390 C, P= 2000 psig
(13789.5 kPa), LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm3/
m3). The only difference between the two runs was that data from
RUN-A were collected at an early stage of the experimental run
while data from RUN-B were collected at a latter stage of the
experimental run.
Conversion is a key assessment measure of catalyst activity and
its stability on increasing operation time indicates good catalyst
life expectancy. Increasing operation time in pilot plant experi-
mental protocols is expressed as increasing number of days that
feedstock is flowing over the catalyst, i.e. days on stream or DOS.
InFig. 7conversion at three hydrocracking temperatures is com-
pared for the two experimental runs. For RUN-A conversion grad-
ually increases with temperature as expected, since increasing
temperature favors cracking. However, conversion exhibits a dif-
ferent behaviour at higher DOS. For RUN-B conversion at 370 C
is smaller than the one of RUN-A, while it is even smaller than con-
version of RUN-B at 350
C. Therefore after at least 34 DOS the cat-alyst activity is decreased and increasing temperature is not able to
compensate for this activity loss, possibly due to catalyst blockage
by the large feed molecules. For RUN-B, conversion at the highest
hydrocracking temperature (390C) is higher than the one at the
middle temperature, but still significantly smaller than the conver-
sion calculated as smaller DOS (RUN-A).
The hydrogenation effectiveness at increasing DOS is examined
inFig. 8. In particular for both runs the decrease of C/H ratio % of C/
H of feed is monotonically decreasing with increasing temperature
as it was discussed in Section 3.1, since saturation is not favored
with temperature. However in the case of higher DOS (RUN-B) this
C/H ratio decrease is dramatic at the DOS = 37, indicating that after
at least 37 DOS the ability of the catalyst to allow saturation is hy-
drant significantly. Therefore, the extended DOS cause an increas-
ing inhibition of saturation activity.
Finally the heteroatom removal effectiveness for extended DOS
is explored in Fig. 9. The removal of all atoms (S, N and O) is
decreasing for increasing DOS but the effect of DOS is different
for all atoms. In the case of sulfur and nitrogen removal it is clear
that after at least 26 days the ability of the catalyst to remove these
atoms is decreased as the results between RUN-A and RUN-B are
different even at the smallest temperature. Specifically in the case
of nitrogen removal the difference is significant, indicating that the
effectiveness of nitrogen removal is hindered earlier than the one
of sulfur removal. However the effect of catalyst life on the removal
390370350
12.13
10.6710.84
3.35
11.1212.10
0
2
4
6
8
10
12
14
Reactor Temperature (deg C)
C/Hra
tio
(%o
ffee
d)
RUN-A
RUN-B
9 DOS 26 DOS
16 DOS 34 DOS 23 DOS
37 DOS
Fig. 8. Effect of DOS on carbon-to-hydrogen ratio.
9 DOS 16 DOS 23 DOS
26 DOS 34 DOS 37 DOS
60
65
70
75
80
85
90
95
100
390370350
Reactor Temperature (deg C)
Su
lfur
Remova
l(%
offee
d)
23 DOS16 DOS SOD73SOD9 34 DOS
26 DOS
60
65
70
75
80
85
90
95
100
Reactor Temperature (deg C)
Nitrogen
Remova
l(%
offee
d)
9 DOS
16 DOS 23 DOS
26 DOS
34 DOS37 DOS
60
65
70
75
80
85
90
95
100
Reactor Temperature (deg C)
Oxygen
Remova
l(%
offee
d)
RUN-A
RUN-B
9 DOS 16 DOS 23 DOS
26 DOS 34 DOS 37 DOS
60
65
70
75
80
85
90
95
10023 DOS16 DOS SOD73SOD9 34 DOS
26 DOS
60
65
70
75
80
85
90
95
100
9 DOS
16 DOS 23 DOS
26 DOS
34 DOS37 DOS
60
65
70
75
80
85
90
95
100
390370350
390370350
Fig. 9. Effect of DOS on heteroatom removal (S, N and O) at different hydrocracking temperatures. All experiments were performed at P= 2000 psig (13789.5 kPa),LHSV = 1.5 h1 and H2/oil = 6000 scfb (1068 nm
3/m3).
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of these atoms is constant as the difference between the RUN-A
and RUN-B results are relatively constant. Finally the effect of
DOS on de-oxygenation is observed a little later, i.e. after 34 DOS.
However the effect of catalyst life is stronger for oxygen removal
as a significant increase of the difference between RUN-A and
RUN-B is observed for increasing DOS.
4. Conclusions
Hydrocracking of used cooking oil is a prominent process for the
production of biofuels. This work considers several parameters for
evaluating the effectiveness of this technology, mainly hydrocrack-
ing temperature, liquid hourly space velocity (LHSV) and days on
stream (DOS).
Conversion and overall biofuels yield is favored with increasing
temperature and decreasing LHSV, as cracking activity is increased.
However, moderate reaction temperatures and LHSVs are more
attractive if diesel production is targeted, whereas higher temper-
atures and smaller LHSVs should be employed if gasoline produc-
tion is also important. Heteroatom (sulfur, nitrogen and oxygen)
removal is also increasing as hydrocracking temperature increases,
with de-oxygenation particularly favorable. Saturation however is
not favored with temperature indicating a necessity of a pre-treat-
ment step prior to hydrocracking, to enable saturation of the dou-
ble bonds prior to cracking and heteroatom removal.
Finally, catalyst deactivation was observed by monitoring con-
version, heteroatom removal and saturation effectiveness with
increasing DOS. In all cases catalyst effectiveness was decreased
with increasing DOS but at different rates. Sulfur and nitrogen re-
moval are affected earlier than all other reactions. Saturation
reactions are affected only after the maximum DOS studied. Con-
version and oxygen removal are also significantly affected and
their loss of effectiveness appears more rapid than the other reac-
tion mechanisms.
Acknowledgements
The assistance of Mr Athanasios Demetriades in conducting the
experiments presented in this paper is gratefully acknowledged.
The authors also wish to express their appreciation for the financial
support provided by the program MOHLOS, funded partially from
the European Regional Development Fund by 75% and from the
Greek General Government by 25%, in conjunction with the Mea-
sure 1.3, Action 1.3.1.
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