Antiknock properties of furfural derivatives

Article abstract of DOI:10.1134/S10704272150110063

Preparative amounts of furfuryl alcohol ethers and furfural acetals were prepared from renewable vegetable raw materials. The blending reseach octane numbers of mixing of furan derivatives in straight-run gasoline were estimated: butyl furfuryl ether, 97.8 ± 7; propyl furfuryl ether, 112 ± 6; furfural diethyl acetal, 105 ± 6, furfural ethylene glycol acetal, 108 ± 7; furfurylamine, 194 ± 4. These results demonstrate prospects for using furan derivatives as available biofuels.

Full text of DOI:10.1134/S10704272150110063

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 11, pp. 1778−1782. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © V.E. Tarabanko, M.Yu. Chernyak, I.L. Simakova, K.L. Kaigorodov, Yu.N. Bezborodov, N.F. Orlovskaya, 2015, published in Zhurnal
Prikladnoi Khimii, 2015, Vol. 88, No. 11, pp. 1563−1567.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Antiknock Properties of Furfural Derivatives
V. E. Tarabankoa,b, M. Yu. Chernyaka, I. L. Simakovac, K. L. Kaigorodova,
Yu. N. Bezborodovb, and N. F. Orlovskayab
a Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences,
ul. Akademgorodok 50/24, Krasnoyarsk, 660036 Russia
b Siberian Federal University, pr. Svobodnyi 79, Krasnoyarsk, 660041 Russia
c Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences,
ul. Akademika Lavrent’eva 5, Novosibirsk, 630090 Russia
e-mail: veta@icct.ru
Received April 30, 2015
Abstract—Preparative amounts of furfuryl alcohol ethers and furfural acetals were prepared from renewable
vegetable raw materials. The blending reseach octane numbers of mixing of furan derivatives in straight-run
gasoline were estimated: butyl furfuryl ether, 97.8 ± 7; propyl furfuryl ether, 112 ± 6; furfural diethyl acetal, 105
± 6, furfural ethylene glycol acetal, 108 ± 7; furfurylamine, 194 ± 4. These results demonstrate prospects for using
furan derivatives as available biofuels.
DOI: 10.1134/S10704272150110063
Processing of renewable raw materials into biofuels
is an actively developing field of chemical and biotech-
nological research, a base of chemical technologies of
the future. Products of such type are prepared by either
biochemical (ethanol, butanol, etc.) or chemical (pyrol-
ysis, hydrolysis products, etc.) methods. Acid-catalytic
processes of conversion of hexose carbohydrates are
characterized by relatively high rates compared to en-
zymatic processes and by a narrow range of products
{mainly 5-hydroxymethylfurfural, levulinic (4-oxopen-
tanoic) acid, and their esters [1, 2]} compared to pyroly-
sis processes. Catalytic hydrogenation of these products
and their esters is a route to promising additives to gaso-
lines (2,5-dimethylfuran, octane number 119) [3, 4] and
diesel fuels (butyl levulinate, butyl valerate).
of furfuryl alcohol under the action of zeolite and
sulfuric acid catalysts was demonstrated, and the octane
number of this product was determined (ON 110) [6].
The antiknock properties of other alkyl furfuryl ethers,
e.g., of propyl and butyl furfuryl ethers, have not been
described in the literature. One of the most promising
furfural hydrogenation products, 2-methylfuran (ON
131), in a mixture with gasoline has successfully passed
road trials (90 000 km) [3]. Furfuryl alcohol also has
high octane number (134) [7].
The possibility of using glycerol and arabinose ke-
tals as high-octane components, despite their very low
volatility, was demonstrated [8]. MMA (mono-methyl-
aniline) is a well-known antiknock additive [9]. Furan
analogs of such compounds, furfural diethyl acetal and
ethylene glycol acetal, and also furfurylamine, have
boiling points in the boiling range of gasoline fractions,
but their antiknock properties have not been studied.
In Russia, the development of biofuels based on
furfural, a readily available product of acid-catalytic
conversion of pentose carbohydrates, is only at the initial
step. It should be noted that agricultural grassy plant
wastes, from which the furfural production is the most
efficient, can be cheaper than wood wastes from which
5-hydroxymethylfurfural can be produced [5]. The
possibility of synthesizing 2-ethoxymethylfuran (ethyl
furfuryl ether) in 30–50% yield by direct alkylation
This study was aimed at evaluating the antiknock
properties of furfural derivatives, namely, of its acetals,
propyl, and butyl ethers of furfuryl alcohol and of
furfurylamine, and also at examining the possibility of
preparingalkylfurfurylethersbycatalytichydrogenation
of furfural in alcoholic media.
1778

ANTIKNOCK PROPERTIES OF FURFURAL DERIVATIVES
1779
EXPERIMENTAL
(Bruker Avance III NMR spectrometer, 600 MHz) at
the Center for Shared Use of the Krasnoyarsk Research
Center, Siberian Branch, Russian Academy of Sciences.
The research octane numbers of the solutions of the
synthesized compounds in straight-run gasoline were
determined with a Waukesha CFR F1/F2 universal in-
stallation for octane number determination (the United
States).
In our study, we used furfuryl alcohol and
furfurylamine (98% main substance, Acros Organics),
butanol, butyl iodide, and propyl iodide of analytically
pure grade.
To determine the octane number, we used as diluent
straight-run gasoline with the following characteristics:
research octane number 63; density 0.719 g mL–1;
weight fraction of sulfur 0.017%; initial and final boiling
points 35 and 216°С, respectively; limits of 10, 50, and
90% evaporeted distillation of 65, 112, and 170°С,
respectively.
RESULTS AND DISCUSSION
Data on the antiknock properties of the furan
derivatives in ~10% solutions in straight-run gasoline
are given in Table 1.
Propyl and butyl furfuryl ethers were synthesized
by the procedure described in [10]. Equimolar amounts
of furfuryl alcohol and propyl iodide (20 and 37 g,
respectively) were placed in a 250-mL conical flask
equipped with a reflux condenser. An equimolar amount
of KOH (15–17 g) was gradually added with stirring.
After that, the mixture was heated on a water bath to
50°С. After the evolution of gaseous by-products
ceased, an additional 30 g of propyl iodide was added,
and the heating was continued for 1 h. After the process
completion, the reaction mixture was washed with water
to remove residual furfuryl alcohol, dried over sodium
sulfate, and distilled under reduced pressure. Synthesis
of butyl furfuryl ether was performed similarly. Yields
of propyl and butyl furfuryl ethers were 45–55 and 70–
80% of theory, respectively. The main substance content
of the synthesized products was no less than 95%,
according to GLC and NMR data.
The blending research octane number (BRON) of the
substances was evaluated by the increment of the octane
number of their solutions in gasoline, assuming linear
correlation between the weights of the components in
the solution and the octane number of the solution in
accordance with the equation
BRONх = [RONsoln · (mх + mg) – RONgmg]/mх,
where BRONх and RONg are the octane numbers of the
test substance and gasoline, respectively, RONsoln is the
octane number of the solution of the substance in gaso-
line, and mх and mg are the weights of the test substance
and gasoline.
The results of measuring the octane number of
toluene coincide with the published data (115.7 [11])
within the experimental accuracy.
Furfural diethyl acetal was prepared by two proce-
dures: reaction of furfural with triethyl orthoformate
[11] and direct reaction of furfural with ethanol. In the
latter case, to shift the equilibrium, a solution of furfural
in ethanol (molar ratio 1 : 3) was kept at room tempera-
ture for 30–60 days in a desiccator with calcium oxide
placed on the desiccator bottom. With calcium oxide
loaded directly into the furfural–ethanol solution, the
acetalization does not occur to noticeable extent.
The octane numbers of all the oxygen-containing
furan derivatives that we studied are in the interval
97–113, i.e., are 20–30 points lower compared to mono-
and dimethylfuran. The octane number determined for
propyl furfuryl ether virtually coincides with the known
value for its homolog, ethyl furfuryl ether.
The antiknock activity of the acetals studied is
virtually independent of their composition and is only
slightly (by approximately 5 points) inferior to that of
propyl and ethyl furfuryl ethers.
Furfural ethylene glycol acetal was prepared by the
known procedure [11] by refluxing a solution of furfural,
ethylene glycol, and toluene with the removal of the
released water from the condensate using a Dean–Stark
trap (180–190°С).
For furfurylamine, the antiknock activity appeared
to be considerably higher (octane number 194). This
parameter is approximately two times lower than that
of monomethylaniline [9]: Addition of 1.3 wt % MMA
increases the octane number of gasoline by 3.5 points
The compounds obtained were identified by GLC–
MS (Agilent 7890a gas chromatograph–mass spectrom-
eter with Agilent 5975с quadrupole detector) and NMR
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TARABANKO et al.
Table 1. Results of determination of blending research octane numbers (BRON) of furan derivatives and toluene
ON
Concentration of
additive, wt %
Substance boiling
point, °C
Substance
of solution
of substance
Furfural diacetal
12.2
9.53
11.8
11.6
12.2
10.3
–
68.2 ± 0.3
67.3 ± 0.3
67.1 ± 0.3
68.7 ± 0.3
79.0 ± 0.3
68.2 ± 0.3
63.0 ± 0.3
105 ± 6
108 ± 7
190
206
Furfural ethylene glycol acetal
Butyl furfuryl ether
Propyl furfuryl ether
Furfurylamine
97.8 ± 7
189–190
174–175
145
112.4 ± 6
194 ± 4
Toluene
113.2 ± 6.5
63.0 ± 0.3
110.6
Initial gasoline
Table 2. Effect of alcohol and catalyst on the composition of products of catalytic hydrogenation of furfural in butanol and
propanol. Process conditions: 0.53 g of furfural, 19.2 g of alcohol, 400 mg of catalyst, 110°C, 6 h, 1 MPa, H2
Content, mol % based on initial furfural
Catalyst
Alcohol
furfural/furfural
acetal
furfuryl ether
2-methylfuran
furfuryl alcohol
8% CuRu/Ca
8% CuRu/Ca
8% CuRu/C
Butanol
''
43/54b
66/13
27/54
–
–
–
–
–
9.3
9.5
11.1
8.3
Propanol
3% Pt/C
''
''
''
–
–
–
16.3
18.9
15.9
29.4
27.2
34.4
8.7
3% Pt + 3% Ni/C
3% Pt + 3% Re/C
30.3
20.5
a 200 mg of the catalyst.
b Nitrogen atmosphere.
[9], and recalculation of the data in Table 1 gives for
the same amount of the added furfurylamine the ON
increment of 1.7 points. Such relationship may be due
to the fact that the amino group in furfurylamine, in
contrast to monomethylaniline, is not conjugated with
the π-system of the aromatic ring. Hence, the dissociation
energy of the N–H bond in the first compound is higher
than in the second compound, and MMA compared to
furfurylamine is a more effective inhibitor of radical-
chain oxidation.
to hydrocarbons and hence the lower combustion rate,
and the latter parameter determines the octane number
[12]. The second explanation consists in the previously
revealed correlation between the ionization potentials of
compounds of different classes, including oxygenates,
and their antiknock properties [13].
High octane numbers obtained for propyl and
butyl furfuryl ethers (Table 1) and similar published
data for ethyl furfuryl ether [6] show that such ethers
are promising as high-octane components of gasoline.
The existing methods for their production, however,
either are extremely expensive and labor-consuming
[10] or have low selectivity: Acid-catalytic alkylation
of furfuryl alcohol with ethanol occurs with no more
than 30–50% selectivity [6]. The low selectivity is due
Two explanations, not contradicting each other,
can be offered to account for the data obtained on the
antiknock activity of the furan compounds studied. The
first explanation is that oxygen-containing compounds,
oxygenates, have lower heat of combustion compared
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ANTIKNOCK PROPERTIES OF FURFURAL DERIVATIVES
1781
to the occurrence of the well-known side acid-catalytic
processes of furfuryl alcohol tarring and its conversion
into levulinic acid.
complete conversion on platinum catalysts, whereas
on copper–ruthenium systems the conversion is on
the level of 20%. The yield of propyl furfuryl ether on
platinum catalysts reaches 16–19%, whereas only no
more than 5% ether is formed under these conditions
from a solution of furfuryl alcohol in propanol. This
fact means that alkyl furfuryl ethers in the furfural–
alcohol system are mainly formed via hydrogenolysis
of acetals, rather than via alkylation of the furfuryl
alcohol formed:
Attempts were made to synthesize furfuryl ethers
directly by catalytic hydrogenation of furfural in
alcoholic media (Table 2). Under these conditions,
furfural in the reaction mixture undergoes acetalization,
and the fraction of acetals in the products can exceed
50 mol %. After this step, both furfural and its acetal
undergo hydrogenation. Furfural and acetals undergo
It should be noted that, on copper–ruthenium
catalysts, which are less active than platinum catalysts,
the selectivity of the formation of alkyl furfuryl ethers
is on the level of 50 mol % (Table 2). Similar possibility
of catalytic hydrogenation of 5-butoxymethylfurfural
and its dibutyl acetal into the corresponding ether,
2,5-dibutoxymethylfuran, was demonstrated recently
[14].
CONCLUSIONS
(1) The blending research octane numbers of butyl
furfuryl (98) and propyl furfuryl (112) ethers, furfural
diethyl acetal (105) and ethylene glycol acetal (108),
and furfurylamine (194) were determined.
(2) The possibility of preparing ethyl furfuryl ether
by catalytic hydrogenation of furfural in ethanol with up
to 50% selectivity was demonstrated.
Hydrogenation of acetals into ethers is seldom
considered in the literature [15] for two reasons.
First, the acetal group is very inert and is used for the
protection of the carbonyl group in hydrogenation of
other moieties in complex molecules. Second, in most
cases, with rare exceptions such as furfuryl alcohol,
ethers can be readily synthesized by direct alkylation.
(3) A preparative method for synthesizing furfural
diethyl acetal by direct reaction of the aldehyde and
alcohol in the presence of calcium oxide as dehydrating
agent was suggested.
ACKNOWLEDGMENTS
The octane numbers obtained are high; therefore, the
furan derivatives studied show promise as high-octane
gasoline components. The substances studied are rela-
tively high-boiling, but their boiling points are neverthe-
less in the boiling range of gasoline (<200°С). The re-
vealed possibilities of catalytic hydrogenation of furfu-
ral into alkyl furfuryl ethers in alcoholic solutions open
the possibility of the development of new methods for
their synthesis. Thus, our results will be useful for trans-
forming the technologies of motor fuel production from
petroleum raw materials to renewable vegetable raw
materials, i.e., to the technologies of “green chemistry.”
The authors are grateful to the Russian Foundation
for Basic Research for the financial support of this study
(project no. 13-03-00754).
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