Production of BHD (Bio Hydrofined Diesel) with Improved Cold Flow ...

Production of BHD (Bio Hydrofined Diesel) with Improved Cold
Flow Properties
Hideki Ono, Hideshi Iki, Akira Koyama, Yasutoshi Iguchi
Central Technology Laboratory, Nippon Oil Corporation
8, Chidoricho, Naka-ku, Yokohama, 231-0815 Japan
e-mail: hideki.ono@eneos.co.jp
ABSTRACT
With its potential benefits of primary energy diversification and CO 2 reduction, there is growing
interest in using Biomass Fuels for transportation. FAME (Fatty Acid Methyl Ester), obtained from
fats and oil such as vegetable oil using a transesterification reaction with methanol, is recently
becoming popular as a bio-diesel. As FAME contains unsaturated carbon-carbon bonds from the feed
materials, its storage stability is an issue. There are also other points of concern, namely, poor cold
flow properties and FAME’s effects on car components.
In this current situation, technologies to produce high quality fuels from renewable sources,
especially from vegetable oils, using petroleum refinery processes should be promising. We
previously managed to obtain BHD (Bio Hydrofined Diesel), a hydrocarbon nearly identical to
conventional diesel oil, by hydrogenating palm oil. However, poor cold flow properties were still an
issue.
We have now improved the cold flow properties of BHD, using hydroisomerization
technologies. In this paper, we present our study of hydroisomerization technologies, covering
reactivity, distillate yields, evaluation of the obtained fuel, and its applicability as an automotive fuel.
1. INTRODUCTION
Sustainable automotive fuels are fuels that satisfy the conditions of "3E", namely, they are
“economical”, “environmentally-friendly”, and promote "energy security". Over the last few decades,
there has been ongoing development aimed at improving the environmental properties (i.e. exhaust
gas reduction) of automotive fuels made from crude oil, which is excellent in terms of supply and
economical efficiency. While the exhaust gas problem is largely a thing of the past thanks to
ultra-deep desulfurization technology, the focus has shifted to issues of supply stability (diversification
of resources) and environmental compatibility (CO 2 reduction), against a backdrop of spiraling crude
oil prices and the global warming problem.
Many experts see the introduction of biomass fuels as a promising solution. We are beginning to
see rapid adoption in Europe and America, and introduction of biomass fuel is planned in Japan as
well. Experts anticipate growing use of biomass, and studies of technologies for producing
automotive fuels from vegetable oil are also progressing rapidly. The prevailing technology today is
to use FAME (fatty acid methyl ester), produced by reacting vegetable oil with methanol (ester
exchange reaction). With this method, it is possible to turn vegetable oil into light oil with a

consistency similar to diesel oil. FAME is mixed with diesel and used to fuel diesel vehicles, mainly
in Europe. But due to its poor oxidative stability, FAME can only be mixed with diesel in limited
quantities; what are needed are biomass fuels with properties superior to FAME.
We previously managed to obtain BHD (Bio Hydrofined Diesel), a hydrocarbon very similar to
conventional diesel oil, by hydrogenating palm oil. BHD has superior oxidation stability compared to
FAME. However, poor cold flow properties were still an issue. The production of BHD from palm
oil will be described in the second section. In this study, we isomerized BHD to improve its cold flow
properties. Details of these examinations will be presented in the third section.
2. PRODUCTION OF BHD FROM PALM OIL
2.1 Hydrogenation conditions
The feed oil was pretreated (decolorized, degummed, etc.), purified palm oil. The properties of
the feed oil are shown in Table 1. Reaction temperature: 240–360°C; reaction pressure: 3-10 MPa;
LHSV: 0.5 h -1 . A hydrodesulfurization catalyst common in petroleum refining was used.
Table 1
Properties of the Feed Oil
Purified Palm Oil
Density g/cm3 0.9159
Higher Calorific Value MJ/kg 39.5
Carbon mass% 77.0
Hydrogen mass% 11.5
Oxygen mass% 11.4
Nitrogen mass%

100
Component Ratio ,%
80
60
40
20
C18
C16
C18
C17
C16
0
Alkyl Chain
of Palm Oil
Hydrogenated
Palm Oil (280℃)
C15
Hydrogenated
Palm Oil (320℃)
Fig. 1
Carbon Number of Hydrogenated Palm Oil (BHD)
This is thought to be caused by the progression of decarbonation in the hydrodeoxygenation
reaction. That is, in the decarbonation reaction, oxygen is eliminated in the form of CO 2 , and thus the
carbon number of the hydrogenated oil decreases by one, and straight chain hydrocarbons of C15 and
C17 are formed (Fig. 2). The proportion of C15 and C17 increases as the reaction temperature rises,
that is, decarbonation selectivity increases as the reaction temperature rises in the hydrogenation of
palm oil. Looking at the effects of pressure, we found that decarbonation selectivity increases as
pressure becomes lower (Fig. 3).
Vegetable Oil
Palm Oil:
R=C15, C17
RCOOCH 2
RCOOCH
RCOOCH 2
Fatty Acid
Glycerin
+12H 2
Dehydration
+3H 2
Decarbonation
3 R-CH 3 6H 2 O 3 R-H 3 CO 2
CH 3 -CH 2 -CH 3
CH 3 -CH 2 -CH 3
Fig. 2
Scheme of Hydrodeoxygenation Reaction

Decarbonation Selectivity,%
50
40
30
20
10
0
3MPa
6MPa
100 200 300 400
Reaction Temperature,℃
Fig. 3
Reaction temperature and decarbonation selectivity
From Fig. 2, it can be seen that the decarbonation reaction requires less hydrogen than the
dehydration reaction, for the same amount of deoxygenation. Also, decarbonation is less of an
exothermal reaction than dehydration. Therefore, reaction conditions of high decarbonation selectivity
are better from the standpoint of the suppression of hydrogen consumption and exothermicity.
However, when decarbonation selectivity increases, the carbon number of the produced hydrocarbon
decreases and gas oil yields decrease, and carbon dioxide emissions increase; these are disadvantages.
When designing a process of BHD production, we should consider all of these aspects.
2.3 Test run using BHD
We conducted a field test using an actual vehicle, whose fuel contained BHD produced by the
method stated above. The test was conducted from October 2007 to March 2008 in collaboration with
the Tokyo government, Toyota and Hino. The field test was completed with no problems. The details
of the test are described in the paper; "Verification Test of Bio Hydrofined Diesel by Tokyo City
Hybrid Bus" JSAE 20085928.
2.4 Comparison between BHD and FAME
The accelerated oxidation test results for BHD and FAME are shown in Table 4. Oxygen was
bubbled through the oil for 16 hours at 115°C. Acid numbers were measured before and after the test.
Compared to FAME, BHD showed a much smaller acid number increase in the accelerated
oxidization test, confirming its superior oxidation stability. This is because the oil’s unsaturated bonds
have been hydrogenated, and we can say that this allays concerns currently held about problems with
FAME use.
Table 4
Oxidation Stability of BHD and FAME

Acid Number
(before test)
Acid Number
(after test)
Palm
BHD
Palm
FAME
Conventional
Diesel Oil
mgKOH/g 0.00 0.26 0.00
mgKOH/g 0.03 10.40 0.07
The cold flow properties of the BHD are shown in Table 5. The cloud point of the BHD is about
20°C, slightly worse than FAME. Cloud point is the temperature at which wax (paraffin) begins to
separate when and oil is chilled to a low temperature, and it serves as an important indicator of
practical performance in automotive applications in low temperatures. The cloud point of BHD
(20°C) is much higher than the value prescribed in the JIS (Japan Industrial Standard) standard, and
thus BHD cannot be used by itself in winter.
Table 5
Cold Flow Properties of BHD
Palm
BHD
Palm
FAME
Conventional
Diesel Oil
Cloud Point ℃ 20 15 -6
Pour Point ℃ 20.0 12.5 -30.0
CFPP ℃ 22 11 -9
This poor low-temperature performance is due to the fact that hydrogenated oil is a straight chain
hydrocarbon (normal paraffin). In the field test, the fuel contained only 10% BHD, and its cold flow
properties were acceptable. However, the poor cold flow properties of BHD are an issue when we
increase the BHD content or use the BHD-blended diesel in very cold areas. In order to improve the
cold flow properties of BHD, we isomerized BHD (normal paraffin) into iso-paraffin, which has
branched chains in its molecular structure. In the next section, we discuss the examinations.
3. ISOMERIZATION OF BHD
3.1 Isomerization conditions
We conducted reaction experiments involving BHD isomerization using our pilot plants. The
feed BHD was made using the method described in the second section. Two kinds of noble metal
catalysts (amorphous type and zeolite type) were used. Reaction temperature: 300°–340°C; reaction
pressure: 3-10 MPa; LHSV: 1 h -1 .
3.2 Compositions of isomerization products
Typical compositions of isomerization products are shown in Fig. 5. Feed BHD is isomerized into
iso-paraffin and simultaneously cracked into light fractions whose carbon numbers are lower than
C14. This means that the gas oil fraction will decrease as we proceed with the isomerization reaction,
which is necessary to improve cold flow properties. Therefore, when we design the process of BHD

isomerization, we should select a reaction system which has moderate isomerization and minimal
cracking.
Compositions, mass%
100
90
80
70
60
50
40
30
20
10
0
Feed BHD 300℃ 320℃
Gas+Nap
C11-C14
isoC15
isoC16
isoC17
isoC18
nC15
nC16
nC17
nC18
Fig. 5
Catalyst : Zeolite Type
Compositions of Isomerization Products
We compared the reactivity of two catalysts, one being zeolitic and the other amorphous. The
activity of the zeolitic catalyst was higher than that of the amorphous type (Fig. 6).
Feed Conversion, mass%
100
80 Zeolite Type
60
40
20
Amorphous Type
0
290 300 310 320 330 340 350
Reaction Temperature, ℃
Fig. 6
Activity of two kinds of catalyst
Focusing on the relation between isomerization and cracking, we compared cracking ratios at the
same isomerization ratio (Fig. 7). The amorphous catalyst had a lower cracking ratio in the low
conversion region, but the zeolitic catalyst had a lower cracking ratio in the high conversion region.

Cracking Ratio, mass%
40
35
30
25
20
15
10
5
0
Amorphous Type
Zeolite Type
0 20 40 60 80 100
Isomerization Ratio, mass%
Fig. 7
Relationship between Isomerization and Cracking
The relationship between reaction pressure and feed conversion is shown in Fig. 8. Activity is
higher under low pressure conditions. It is thought that this is because dehydrogenation of normal
paraffin, which is the origin of the isomerization reaction, occurs more readily at lower pressure.
Feed Conversion, %
Fig. 8
100
80
60
40
20
0
3MPa
6MPa
10MPa
280 300 320 340 360
Reaction Temperature, ℃
Relationship between Reaction Pressure and Feed Conversion
3.3 Properties of isomerization products
Table 6 shows the properties of the isomerized BHD (isomerization ratio: 50%), which was made
by distilling off the fraction lighter than 185°C. The isomerized BHD has greatly improved cold flow
properties compared to the normal BHD. The cetane number was slightly lower after isomerization,
but the isomerized BHD still has a cetane number higher than that of conventional diesel oil, and
should have good ignition properties.
Table 6
Properties of Isomerized BHD

Isomerized BHD BHD
Density 15℃ g/cm3 0.781 0.783
Viscosity 30℃ mm2/s 3.9 4.1
Pour Point ℃ +5.0 +20.0
Cloud Point ℃ +4 +21
Cetane Number 90.3 101
3.4 Property of isomerized BHD-blended diesel oil
The isomerized BHD described in Table 6 was blended with conventional diesel oil, and a variety
of mixtures were evaluated. As shown in Table 7, the cold filter plug point (CFPP) of diesel oil
containing isomerized BHD was lower than that of normal BHD, even when the isomerized BHD
content is 20 vol%. Looking at the cetane index, isomerized BHD-blended diesel has a lower cetane
index than normal BHD-blended diesel in the case of the 10 vol% blend. However, the blend
containing 20 vol% isomerized BHD had a cetane index the same as that of the 10 vol% normal
BHD blend. We found that a diesel oil which contains 20 vol% of isomerized BHD (isomerization
ratio: 50%) would have properties as good or better than those of conventional diesel oil.
Table 7
Properties of Isomerized BHD-Blended Diesel Oil
Normal BHD 50% Isomerized BHD Conventional
BHD Content 10vol% 10vol% 20vol% Diesel Fuel
Density g/cm3 0.8103 0.8198 0.8140 0.8283
Viscosity mm2/s 2.828 3.330 3.250 3.254
Distillation T90 ℃ 326.0 330.0 324.5 337.5
CFPP ℃ -10 -14 -12 -9
Cetane index 62.0 58.2 61.3 58.1
4. CONSIDERATION
Through the reaction experiments involving BHD isomerization, we were able to obtain
isomerized BHD, and showed that the isomerization ratio can be controlled over a wide range
through careful selection of the catalysts and reaction conditions. In BHD isomerization, the cracking
reaction occurs as a sub reaction. It is important to select a catalyst system and reaction conditions that
minimize cracking, while staying within a range in which the isomerization ratio is sufficient.
Isomerization improved the cold flow properties of BHD, and expanded the range of usable BHD
blend ratios. One of the advantages of BHD is a high cetane number. Isomerization does not cause a
major decline in cetane number, meaning that isomerized BHD still has the same advantage.
Palm oil and other vegetable oils (rapeseed, sunflower, soybean, corn, etc.) are used as cooking
oils all over the world. If these oils are to be used for automotive fuels, it will probably not happen by
getting people to use less for cooking. And if we simply increase cultivation, there is a risk of serious
environmental destruction. We need to thoroughly consider how sources of raw materials can be

secured, also looking at the use of non-edible vegetable oils such as Jatropha oil and algae oil.
5. CONCLUSION
In our study of BHD production (hydrogenation of palm oil) and BHD isomerization, the
following things became clear.
a) By hydrogenating palm oil, it is possible to obtain from vegetable oil a hydrocarbon nearly equal
in many respects to conventional diesel oil.
b) BHD is a straight chain hydrocarbon derived from the alkyl chains of the vegetable oil.
c) BHD has higher oxidation stability than FAME.
d) A 14,000 km test run using an actual vehicle car was conducted using diesel oil which contained
10% BHD.
e) It is possible to produce isomerized BHD whose iso-paraffin content is controllable.
f) Isomerization greatly improved the cold flow properties of BHD.
g) BHD isomerization increases the range of usable blend ratios for BHD with diesel oil.
h) A diesel oil containing 20% isomerized BHD shows properties nearly the same as those of
conventional diesel oil.
6. REFERENCE
1) "Verification Test of Bio Hydrofined Diesel by Tokyo City Hybrid Bus" JSAE 20085928