Aryl Butyl Acetals as Oxygenate Octane-Enhancing Additives for Motor Fuels

Article abstract of DOI:10.1134/S0965544120010107

Abstract: This study is devoted to finding new oxygenate additives improving the quality of motor fuels. Aryl butyl acetals obtained by the addition of phenols to butyl vinyl ethers are used as additives for the first time. The reaction is carried out at

Full text of DOI:10.1134/S0965544120010107

ISSN 0965-5441, Petroleum Chemistry, 2020, Vol. 60, No. 1, pp. 134–139. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Neftekhimiya, 2020, Vol. 60, No. 1, pp. 148–153.
Aryl Butyl Acetals as Oxygenate Octane-Enhancing Additives
for Motor Fuels
L. A. Oparinaa, *, N. A. Kolyvanova, A. A. Ganinab, and S. G. D’yachkovab
aFavorsky Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia
bIrkutsk National Research Technical University, Irkutsk, 664074 Russia
*e-mail: oparina@irioch.irk.ru
Received May 28, 2019; revised August 21, 2019; accepted September 16, 2019
Abstract—This study is devoted to finding new oxygenate additives improving the quality of motor fuels. Aryl
butyl acetals obtained by the addition of phenols to butyl vinyl ethers are used as additives for the first time.
The reaction is carried out at room temperature in the presence of catalytic (0.3–0.6 mol %) amounts of CF3-
CO2H and leads to the formation of the desired products in a quantitative yield. The antiknock properties of
the synthesized compounds have been investigated. It has been found that synthesized aryl butyl acetals pos-
sess quite a high research octane number (RON) (up to 110) and can be promising additives to motor gasoline
for increasing knock resistance, thus, the addition of 3 wt % aryl butyl acetal increases the RON of an n-hep-
tane–isooctane mixture as model fuel and that of the AI-92-K5 base fuel by 1.0–1.2 and 0.1–0.4 points,
respectively. The efficiency of the antiknock additive depends on the structure of the alkoxyl radical in the
aryl butyl acetal molecule, thus, the blending ONs of acetals with a branched isobutoxyl radical is higher than
the values of linear butoxy derivatives by 3.4–6.7 points. Acetals containing the methyl substituent in the phe-
noxy radical have higher ON values.
Keywords: aryl butyl acetals, oxygenate additives, antiknock properties, octane number
DOI: 10.1134/S0965544120010107
The main global trend of the improvement of the
environmental properties and performance of motor
fuels is the use of multifunctional additives, mainly
oxygenates. The presence of oxygen in the fuel com-
position makes it possible to reduce hazardous carbon
monoxide emissions by 30% and emissions of unburnt
hydrocarbons by 15% [1]. In order to increase the anti-
knock properties, components obtained using second-
ary methods of processing of petroleum fractions (cat-
alytic cracking, isomerization, and alkylation) are
added to gasolines or special high-octane additives are
introduced into the fuel.
In recent years, special attention has been paid to
oxygenate additives based on renewable feedstock such
as cellulose, waste products of forest and wood pro-
cessing industries and agriculture, algae, and lignin.
The use of such oxygenates expands fuel resources and
makes it possible to improve their quality by means of
decreasing the toxicity of combustion products [2, 3].
Organic products and liquid fuel (“bio-oil”) [8–11]
have been obtained during the comprehensive pro-
cessing of vegetable feedstock. In particular, fast
pyrolysis of plant biomass leads to the formation of a
mixture of organic oxygen-containing compounds
(25–45% O) including carbohydrates, phenols, alco-
hols, esters, furans, aldehydes, etc. [12]. Many of these
components including compounds of the phenol
series can also be used as oxygenate additives for both
gasoline and diesel fuel [13]. For example, the addition
of anisole (methyl phenyl ether) to gasoline (5 wt %)
increases the octane number of the fuel by 4 points
[14].
Alcohols, ethers, and esters, as well as acetals
including cyclic acetals (1,3-dioxocyclanes) [2, 3], are
the most common among the oxygenates used for
increasing the antiknock properties of fuels. The latter
are classified with low-hazard chemicals capable of
improving the properties of fuels. The technical results
of their use as oxygenate additives are an increase in
both the phase stability of motor fuels upon contact
with water and antiknock rating [4–6]. A decrease in
gum formation is noted in the case of combined use of
alcohols and cyclic ketals in fuel blends [5, 6], and a
synergetic effect of an increase in the ON [7] has been
revealed.
We have earlier studied the use of synthetic butyl
alcohols of domestic manufacture as the oxygenate
additives to motor fuels [15] as well as have found the
possibility for the use of aryl vinyl ethers (the modified
products of the catalytic lignin destruction) as the
additives increasing the antiknock rating of gasolines
[16]. The aim of this work is the search for new oxy-
134

ARYL BUTYL ACETALS AS OXYGENATE OCTANE-ENHANCING ADDITIVES
Table 1. Synthesis of alkyl aryl acetals
Vinyl ether Yield of 3, %
135
Phenol
OH
Alkyl aryl acetal
Me
98
99
99
O
Me
1a
2a
2a
O
O
Me
3a
Me
OH
OH
Me
O
Me
O
O
Me
1b
1a
Me
3b
Me
O
Me
Me
O
O
Me
2b
3c
Me
OH
Me
Me
O
97
Me
Me
O
O
1b
Me
2b
Me
3d
gen-containing compounds acceptable as the anti- ture (~after 30 min), and target aryl butyl acetal 3 was
knock additives to motor fuel. To achieve the goal in obtained after the removal of the salt.
hand, aryl butyl acetals were synthesized, and their
1-(n-Butoxy-1-phenoxy)ethane (3a). Yield 47.55 g
(98%).
influence on the change in the fuel octane number was
assessed.
nD24
1.4805. IR (ν, cm−1): 3065, 3036, 2956,
2935, 2873, 1595, 1491, 1464, 1383, 1349, 1292, 1234,
1171, 1130, 1083, 1030, 971, 924, 813, 754, 694, 611,
510. 1H NMR, δ, ppm: 7.30 m (2H, Ph), 7.02 m (3H,
Ph), 5.41 q (1H, J = 5.3 Hz, OCHO), 3.75 and 3.50 m
(1H each, OCH2), 1.58 m (2H, CH2Et), 1.52 d (3H,
J = 5.3 Hz, MeCH), 1.38 m (2H, CH2Me), 0.92 t
EXPERIMENTAL
The synthesis methods of aryl butyl acetals with
different structures are presented below. The formulae
of the initial substances and final reaction products are
presented in Table 1 below.
(3H, J = 7.3 Hz, Me). 13C NMR, δC, ppm: 13.7
(MeCH2), 19.2 (CH2Me), 20.1 (MeCH), 31.7
(CH2Et), 65.5 (OCH2), 99.5 (OCHO), 117.3 (C3,5),
Synthesis of Aryl Butyl Acetals 3a–3d (General
121.7 (C4), 129.3 (C2,6), 157.0 (C1). Found, %: C
74.02; H 9.31. Calculated for C12H18O2, %: C 74.19; H
9.34.
Procedure)
0.10–0.18 g (0.3–0.6 mol %) of CF3CO2H was
added to phenol 2 (0.25 mol), and freshly distilled
vinyl ether 1 (0.25 mol) was added dropwise to the
obtained mixture over 15–20 min upon vigorous stir-
ring. The reaction was accompanied by an exothermic
effect. The maximum temperature of 60–65°C was
controlled by the speed of addition of vinyl ether.
1-(Isobutoxy-1-phenoxy)ethane (3b). Yield 47.98 g
nD24
(99%).
1.4790. IR (ν, cm−1): 3065, 3036, 2958,
2914, 2875, 1594, 1491, 1385, 1344, 1292, 1235, 1165,
1129, 1084, 1033, 1003, 922, 804, 754, 694, 610, 511.
Upon the completion of the reaction, the acid catalyst 1H NMR, δ, ppm: 7.30 m (2H, Ph), 7.03 m (3H, Ph),
was neutralized by 0.1 g of K2CO3 during the sponta- 5.40 q (1H, J = 5.3 Hz, OCHO), 3.50 m and 3.24 dd
(2H, J = 9.0, 6.8 Hz, OCH2), 1.85 m (1H, CH), 1.51
neous decrease in the temperature to room tempera-
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136
OPARINA et al.
d (3H, J = 5.3 Hz, MeCH), 0.89 and 0.91 d (3H each, (State Standard) 8226-2015 “Fuel for engines.
J = 7.0 Hz, Me2CH). 13C NMR, δC, ppm: 19.3
(Me2CH), 20.0 (MeCH), 28.4 (CHMe2), 72.3
(OCH2), 99.5 (OCHO), 117.3 (C3,5), 121.7 (C4), 129.3
Research method for determination of octane num-
ber”. The blending RONs were calculated according
to the formula
(C2,6), 157.0 (C1). Found, %: C 74.08; H 9.40. Calcu-
lated for C12H18O2, %: C 74.19; H 9.34.
RONbase+additive − RONbaseωbase
RONblend
=
,
ωadditive
1-(n-Butoxy)-1-(3-methylphenoxy)ethane
(3c).
24
where RONblend is the blending octane number of the
additive, RONbase + additive is the octane number of the
base with the addition of the additive determined by
the research method, RONbase is the octane number of
the base, ωbase is the weight fraction of the base (0.97),
and ωadditive is the weight fraction of the additive (0.03).
Yield 51.50 g (99%).
1.4819. IR (ν, cm−1): 3035,
nD
2986, 2955, 2933, 2872, 2735, 1595, 1488, 1456, 1382,
1348, 1283, 1258, 1160, 1126, 1085, 1029, 954, 912,
1
875, 854, 778, 743, 693, 618, 445. H NMR, δ, ppm:
7.17 m (1H, C6H4), 6.82 m (3H, C6H4), 5.38 q (1H,
J = 5.4 Hz, OCHO), 3.74 and 3.49 m (1H each,
OCH2), 2.34 s (3H, MeC6H4), 1.58 m (2H, CH2Et),
1.50 d (3H, J = 5.4 Hz, MeCH), 1.38 m (2H,
CH2Me), 0.92 t (3H, J = 7.0 Hz, Me). 13C NMR, δC,
ppm: 13.7 (Me), 19.2 (CH2Me), 20.1 (MeCH), 21.3
The IR spectra of the synthesized compounds were
recorded in a thin film on a Bruker JFS-25 spectrom-
1
13
eter in a region of 400–4000 cm−1. H and C NMR
spectra were recorded at room temperature on a
(MeC6H4), 31.6 (CH2Et), 65.3 (OCH2), 99.4 Bruker-DPX-400 instrument with the operating fre-
(OCHO), 114.0 (C6), 118.0 (C2), 122.4 (C4), 129.0
(C5), 139.2 (C3), 157.0 (C1). Found, %: C 75.00; H
9.60. Calculated for C13H20O2, %: C 74.96; H 9.68.
quencies of 400.13 and 100.62 MHz, respectively; the
solvent was CDCl3. The chemical shifts of 1H and 13C
NMR were recorded relative to CDCl3 as the internal
standard (δ 7.27 and 77.0 ppm, respectively). The ele-
mental analysis was performed on a Flash EA 1112
Series analyzer.
1-(Isobutoxy)-1-(3-methylphenoxy)ethane
(3d).
24
Yield 50.43 g (97%).
1.4794. IR (ν, cm−1): 3036,
nD
2958, 2925, 2874, 2734, 1595, 1486, 1466, 1383, 1351,
1283, 1256, 1157, 1125, 1086, 1035, 1007, 953, 897,
777, 693, 617, 496, 444. 1H NMR, δ, ppm: 7.21 m (1H,
C6H4), 6.86 m (3H, C6H4), 5.41 q (1H, J = 5.3 Hz,
OCHO), 3.27 and 3.53 m (1H each, OCH2), 2.36 s
(3H, MeC6H4), 1.89 m (1H, CHMe2), 1.53 d (3H, J =
5.3 Hz, MeCH), 0.94 and 0.95 d (6H, J = 7.0 Hz,
RESULTS AND DISCUSSION
The atom-efficient reaction of electrophilic addi-
tion of OH reagents to vinyl ethers [17] deserves spe-
cial attention among the known methods of prepara-
tion of acetals. This technique is universal. By varying
substituents in vinyl ether and protogenic reagent, var-
ious and often hardly accessible by other methods
13
Me2CH). C NMR, δC, ppm: 19.3 (Me2CH), 20.0
(MeCH), 21.3 (MeC6H4), 28.4 (CHMe2), 72.2
(OCH2), 99.4 (OCHO), 114.1 (C6), 118.0 (C2), 122.4 symmetrical and unsymmetrical acetaldehyde acetals
(C4), 129.0 (C5), 139.2 (C3), 157.0 (C1). Found, %: C
74.80; H 9.73. Calculated for C13H20O2, %: C 74.96; H
9.68.
can be obtained.
Aryl butyl acetals required for the study can be
obtained either from butyl alcohols and aryl vinyl
The RON values were determined on a standard ethers (reaction 1) or from butyl vinyl ethers and phe-
unit with one-cylinder engine according to GOST nols (reaction 2).
OAr
2) H+
1) H+
+
+
Me
ArOH.
BuOH
BuO
ArO
OBu
Reaction 1 requires harsh conditions because of the ether, which eventually decreases the yield of the tar-
decreased electron density of the double bond of aryl get product. As a result of this, the samples of acetals 3
vinyl ethers. The experiments showed that n-BuOH for their investigation as additives to motor fuels were
does not add to vinyl m-cresyl ether in the presence of prepared according to reaction 2, namely, from butyl
a catalyst, 0.5 mol % CF3CO2H (60°C, 4 h). The for- vinyl ethers 1a and 1b and phenols 2a and b.
1
mation of acetal 3c was not detected in the H NMR
spectrum even in trace amounts. Harsher reaction
conditions (10 mol % CF3CO2H, 60°C, 8 h) lead to
The most universal preparation method of alkyl
vinyl (in particular, butyl vinyl) ethers is the addition
reaction of alcohols to acetylene in the presence of
side processes such as disproportionation of unsym- basic catalysts which gained scientific and industrial
metrical acetal 3c and telomerization of aryl vinyl development in the 1930s–1970s [18–20]. With the
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ARYL BUTYL ACETALS AS OXYGENATE OCTANE-ENHANCING ADDITIVES
137
Table 2. Blending research octane numbers of acetals 3 (3 wt %) in the model fuel blend*
Additive
RON
Gain in RON
Blending RON
None
70.0
71.0
–
70.0
1.0
103.3
O
O
Me
Me
3a
71.1
1.1
106.7
Me
O
O
Me
Me
3b
71.0
71.2
1.0
1.2
103.3
110.0
Me
O
O
Me
Me
3c
Me
Me
O
O
Me
Me
3d
* The ON values were obtained using the results of three measurements.
1H NMR spectra gives evidence for the absence of dis-
proportionation of adducts 3 under the synthesis con-
ditions.
discovery of a new principle of increasing the reactiv-
ity of nucleophilic reagents by means of the use of cat-
alytic media consisting of a strong base and a polar
nonhydroxylic complexing solvent by Academician
B.A. Trofimov, it turned out to be possible to intensify
the classical base-catalyzed reactions of acetylene and
to perform them at moderate temperatures and
reduced (down to atmospheric) pressures [21, 22].
Synthesized alkyl aryl acetals 3a–3d are colorless
thin liquids with a pleasant odor, they are highly solu-
ble in hydrocarbons and form homogenous solutions
with gasoline. The density of these compounds (0.95–
0.97 g/cm3) slightly depends on the structure of the
Butyl vinyl ethers react with phenols much more alkyl and aryl parts and is close to the density of aryl
readily and selectively. Under standard conditions vinyl ethers. The boiling point is 250–270°C, and it is
(room temperature, equimolar ratio of the reactants, higher than that of the corresponding aryl vinyl ethers.
and 0.3–0.6 mol % CF3CO2H), n-butyl vinyl ether It is expected that 15.3–16.5% oxygen (21.6% in butyl
(1a) and isobutyl vinyl ether (1b) interact with phenol
(2a) and m-cresol (2b) to form corresponding aryl
butyl acetals 3a–3d in quantitative yield (Table 1).
alcohols) will promote a decrease in the concentration
of oxides and harmful substances in the exhaust
fumes.
The influence of synthesized acetals 3a–3d on the
change in the ON was evaluated using an n-heptane–
isooctane model system at a ratio of 3 : 7 (ON 70) and
unleaded gasoline of the AI-92-K5 brand (Angarsk
Petrochemical Company) taken as a base fuel. This
brand of gasoline is the most common in Russia [23].
The reaction progress was monitored via IR spec-
troscopy by the disappearance of the absorption bands
of the OH group of phenols 2 (in a region of
3400 cm−1) and the vinyloxy group of ethers 1 (3119,
1639, 1612, and 1204 cm−1) in the reaction mixtures.
The presence of just one quartet of the protons of the
methine group (δ ~ 5.4 ppm) and a doublet of the
The tests on a standard unit showed that the intro-
methyl group (δ ~ 1.5 ppm) of the acetal moiety in the duction of acetals 3a–3d (3.0 wt %) into the model
PETROLEUM CHEMISTRY Vol. 60 No. 1 2020

138
OPARINA et al.
Table 3. Blending research octane numbers of acetals 3
(3 wt %) in base gasoline AI-92-K5*
slightly depends on the structure of the aromatic radi-
cal.
In summary, the studied oxygenates, the adducts of
butyl vinyl ethers and phenols, possess quite high
RONs (up to 110) and hold promise as motor gasoline
additives increasing the knock resistance and improv-
ing the performance characteristics.
Additive
RON
Growth in RON Blending RON
None
3a
90.3
90.4
90.5
90.4
90.6
–
–
0.1
0.2
0.1
0.3
93.3
96.7
93.3
100.0
ACKNOWLEDGEMENTS
3b
The work is performed with the use of material and tech-
nical facilities of the Baikal Shared-Use Analytical Center,
Siberian Branch, Russian Academy of Sciences.
3c
3d
CONFLICT OF INTEREST
* The ON values were obtained using the results of three measure-
ments.
The authors declare no conflict of interest to be dis-
closed in this paper.
fuel blend provided a gain in the RON by 1.0–
1.2 points (Table 2).
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