Synergic actions of BEA-type zeolites and ultrasonic irradiation in conversion of geraniol

Article abstract of DOI:10.14233/ajchem.2019.21670

The geraniol conversion reaction was initiated by the simultaneous action of micro- and micro-mesoporous BEA-type zeolites and ultrasonic irradiation (UMR-300B hybrid reactor, 25 kHz, 100-900 W; SRF-1, 20-60 kHz, 100 W). Geraniol by ultrasonic irradiation at 27-100 °C, had a low degree of conversion, upto 2 %. Geraniol was a resistant to ultrasound in argon atmosphere solutions of N,Ndimethylformamide and methanol. In methanolic solution, geraniol was actively converted to linalool and to methyl ethers of linalool and nerol with the selectivity of 80 % on zeolite BEA-25 under ultrasonic irradiation in air at 30 °C. Using BEA-type zeolite/ultrasonicassisted reaction was increased the degree of conversion of geraniol, the selectivity and yield to linalool and nerol on the most active RBEA-25 zeolite by prolonged ultrasonic irradiation (1.5-5 h) or under combined ultrasound and microwave irradiation (US 300 W/MW 550 W, 1.5 h, 80 °C).

Full text of DOI:10.14233/ajchem.2019.21670

Asian Journal of Chemistry; Vol. 31, No. 2 (2019), 438-444
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.21670
Synergic Actions of BEA-Type Zeolites and Ultrasonic Irradiation in Conversion of Geraniol
1,*
1
2
3
4
5
TS. RAMISHVILI , V. TSITSISHVILI , I. IVANOVA , N. KOKIASHVILI , T. BUKIA and G. KURTSIKIDZE
1Petre Melikishvili Institute of Physical and Organic Chemistry, Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia
2Department of Chemistry, Laboratory of Kinetics and Catalysis, Lomonosov Moscow State University, Moscow, Russia
3Department of Chemistry, Faculty of Exact and Natural Sciences, Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia
4San Diego State University, Georgia, Tbilisi, Georgia
5Forensic-Criminalistics Department, Ministry of Internal Affairs of Georgia, 0114 Tbilisi, Georgia
*Corresponding author: Tel: +995 597 740434; E-mail: tsiuri.ramishvili@tsu.ge
Received: 28 August 2018;
Accepted: 31 October 2018;
Published online: 31 December 2018;
AJC-19223
The geraniol conversion reaction was initiated by the simultaneous action of micro- and micro-mesoporous BEA-type zeolites and
ultrasonic irradiation (UMR-300B hybrid reactor, 25 kHz, 100-900 W; SRF-1, 20-60 kHz, 100 W). Geraniol by ultrasonic irradiation at
27-100 ºC, had a low degree of conversion, upto 2 %. Geraniol was a resistant to ultrasound in argon atmosphere solutions of N,N-
dimethylformamide and methanol. In methanolic solution, geraniol was actively converted to linalool and to methyl ethers of linalool and
nerol with the selectivity of 80 % on zeolite BEA-25 under ultrasonic irradiation in air at 30 ºC. Using BEA-type zeolite/ultrasonic-
assisted reaction was increased the degree of conversion of geraniol, the selectivity and yield to linalool and nerol on the most active
RBEA-25 zeolite by prolonged ultrasonic irradiation (1.5-5 h) or under combined ultrasound and microwave irradiation (US 300 W/MW
550 W, 1.5 h, 80 ºC).
Keywords: Geraniol, BEA-type zeolite, Ultrasonic activation, Sinergic effect, Isomerization.
chemical processes and the higher yields of products [9,11-
13].
INTRODUCTION
The investigation of the process of isomerization of terpene
alcohols viz. linalool (C10H18O) and its geometric isomer geraniol
is of practical importance since the isomers of obtained equili-
brium mixture are widely used in the perfumery, medicine and
in cosmetic industry [1,2]. Many homogeneous and heterogen-
eous catalysts for the isomerization of geraniol are known e.g.,
inorganic acids, oxo-compounds of transition elements,
especially W, V and Mo [3,4]; catalytic system of alkyl ortho-
vanadate (RO)3V=O and tetrabutylammonium hydroxide
[(Bu)4N+]OH [5].
The mentioned active systems are environmentally harm-
ful and not regioselective. In the case of "green" zeolite catalysts
such as MOR OFF, zeolite beta (BEA), mesoporous MCM-41
and micro-mesoporous BEA, the yields of the isomers were
low [6-8]. It is known that ultrasonic and microwave techno-
logies have huge potential in the updating of many processes
[9,10]. The ultrasound and microwave irradiation and the assoc-
iated chemical and physical effects, provide more efficient
Today, more that 3000 chemical reactions are known,
which are proceeded by specific activation during microwave
and ultrasonic irradiation, assuming that they are based on
mechanisms of fast dielectric heating of material [14] and
acoustic cavitation [10,15]. From the viewpoint of fundamental
studies, the chemical synthesis transformations by using ultra-
sound and microwave irradiations are considered as one of the
relatively new "green" and progressive direction of chemistry
similar to the use of high-effective catalytic systems micro-
mesoporous composite zeolite materials; their mesoporous
system (in contradistinction from zeolites) enables selective
transformation of large-size molecules (diameter of section is
more than 1 nm) used in pharmacy, perfumery, etc. industries.
In previous study [8], the investigation showed that the
catalytic converting products of geraniol over BEA-type micro-
and micro-mesoporous zeolites (BEA-25, BEA-150, RBEA-
25 and RBEA-150) contained mainly terpene hydrocarbons
C10H16, linalool and nerol (C10H18O), sesquiterpene alcohols:
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Vol. 31, No. 2 (2019)
Synergic Actions of BEA-Type Zeolites and Ultrasonic Irradiation in Conversion of Geraniol 439
C14H24O, (2E,6E)-6,11-dimethyl- 2,6,10-dodecatrien-1-ol and
C15H26O, trans,trans-farnesol, (2E,6E)-3,7,11-trimethyl-2,6,10-
dodecatrien-1-ol. The yields of isomerization products of
geraniol in linalool and nerol were found to be low (3-12 %)
at 80 ºC.
In present study, the reaction of geraniol conversion carried
out under combined BEA-type zeolite and ultrasound (partly
also microwave) irradiation to promote the activity of zeolites
in the isomerization of geraniol (Scheme-I). The analysis showed
that this influence of irradiation is ambiguous; synergistic effect
is present in case of micro- and micro-mesoporous BEA-type
zeolite samples with high acidity and a large pore surface.
The combination of ultrasonic irradiation and BEA-type zeolite
catalyst RBEA-25 allowed to obtain linalool and nerol in the
isomerization of geraniol at 80 ºC with increased yields up to
31 % and selectivity up to 63.2 % at conversion of 49 %.
(hybrid) Reactor UMR-300B (Shinka, Japan) by ultrasonic
vibration probe of 18 mm diameter, US frequency 25 kHz and
at ultrasound output 200-900 W; the reaction vessel consists
of 50 mL three-necked glass ("Bomex") with a condenser.
The ultrasonic activation and conventional catalytic experi-
ments were conducted in an atmosphere of argon, nitrogen or
air. The convential catalytic conversion of geraniol was carried
out at 30-80 ºC in a 50 mL round bottom flask with a reflux
condenser containing the inlet for introducing of an inert gas
[8], duration of run was 1.5-10 h, catalyst mass range 0.0094
-0.05 g, mass ratio of catalyst/geraniol was 1/26.7-1/142 respec-
tively, i.e. 0.17 - 0.92 mol of geraniol/g of catalyst (1.5 mL-8
mL/0.05 g catalyst). The solid zeolite catalyst was removed
by centrifugation. Geraniol conversion was performed in solvent-
free conditions or in the presence of different polar solvents
e.g., methanol, N,N-dimethylformamide and distilled water.
Catalytic activity: For the comparison of results of conven-
tional thermocatalytic and ultrasonic conversions of geraniol
on micro- and micro-mesoporous BEA-type zeolites experi-
ments was carried out under identical test conditions and the
same catalyst loading of 0.92 mol geraniol/g catalyst. The activ-
ities of studied zeolite catalysts were characterized by conversion
of geraniol and selectivities to linalool and nerol. The selectivities
were evaluated with respect to converted geraniol.
10
1
3
CH2OH
E
OH
4
5
Catalyst (BEA-type zeolite)
2
6
CH2OH +
Nerol
7
8
9
Linalool
Geraniol
Scheme-I: Ultrasonically activated isomerization of geraniol into linalool
Analysis of reaction products:After completion of reaction
and separation of catalyst, the reaction products were analyzed
by GC/MS method (Agilent Technologies GC/MS, 7890B/
5977A, USA), in the EI mode, 70 eV. Methanol was used as
solvent, helium as a carrier gas and capillary column HP-5ms,
Ultra Inert, 30 m × 0.32 mm × 0.25 µm; analyzes were carried
out in program mode: hold at 80 ºC for 5 min, ramp to 210 ºC
at 30º/min, hold at 210 ºC for 10 min.
The content of reaction products were determined by the
internal standard method [19], where internal standard was 1-
propanol. Also the amount of linalool, geraniol and nerol was
determined from their calibration curves. The conversion degree
of geraniol was calculated by the decreasing of its concentration
in the final products. The calculations of conversion of geraniol,
yield, selectivity of the products are described earlier [8].
and nerol
EXPERIMENTAL
The chemicals viz., geraniol ≥ 97 %, trans-3,7-dimethyl-
2,6-octadien-1-ol, methanol for HPLC (≥ 99.9 %) were purc-
hased from Sigma-Aldrich. The argon and nitrogen used were
of 99.999 % purity (Metihbect, Ukraine). Geraniol was used
without further purification, it contained up to 1 % cis-geraniol
(nerol), small amount of iso-geraniol and 2 % α-citral.
Preparation of catalyst:The micro-mesoporous materials
(RBEA-25 and RBEA-150) was synthesized by recrystallization
[16,17], respectively of starting microporous zeolites NH4-
BEA (nSiO2/nAl2O3 = 25) and H-BEA (nSiO2/ nAl2O3 = 150)
from Zeolyst International, USA.
Catalysts characterization: The chemical composition
of the investigated catalysts and their specific surface area,
volume of micro- and mesopores were previously determined
by X-ray fluorescence analysis [7] and from nitrogen adsorption-
desorption isotherms at 77 K on an automated porosimeter
ASAP 2000 Micromeritics, USA.Acidic properties of catalysts
were characterized using temperature-programmed desorption
of ammonia (TPD NH3) on USGA-101 multipurpose sorption
gas analyzer [16].
The distribution sizes of crystallites of catalysts BEA-150
and RBEA-150, before and after ultrasonic irradiation of geraniol
together with a catalyst were determined on the laser light
scattering particle size analyzer (Laser-Particle SizerAnalysette
12-DynaSizer, Fritsch) as described earlier [18].
RESULTS AND DISCUSSION
Physicochemical characteristics of BEA-type zeolite:
Table-1 shows that the chemical compositions (i.e. molar ratio
of SiO2/Al2O3) of parent BEA zeolites with microporous structure
and corresponding recrystallized (RBEA) zeolites with combined
micro-mesoporous structure are nearly similar. The latter have
a larger total pore volume and a larger proportion of mesopores
with an average pore diameter (by BET) of about 3.5 and 3.9 nm
for samples RBEA-25 and RBEA-150, respectively. The BEA-
type microporous zeolites and their modified micro- mesoporous
forms have similar acid properties and they differ in the charact-
eristics of the porous structure.
The particle sizes distributions of parent (BEA-150) and
ultrasound-irradiated catalysts (BEA-150 and RBEA-150) in
geraniol as solvent are shown in Table-2. They were deter-
mined with Cumulant inversion algorithm in term of volume.
Irradiation with ultrasound (350 W, 1.5 h, 40 ºC) in processor
UMR-300B was carried out.
Catalytic and ultrasonic activation: The conversion of
geraniol was carried out under undirect ultrasonic irradiation
in nitrogen atmosphere in the Multi-frequency Sonoreactor
SRF-1 (20/40/60 kHz, ultrasound output 100W, Shinka, Japan)
and under direct ultrasonic irradiation in Ultrasonic-Microwave

440 Ramishvili et al.
Asian J. Chem.
TABLE-1
PHYSICO-CHEMICAL PROPERTIES OF CATALYSTS USED IN GERANIOL CONVERSION [RReeff.. 88]]
Catalyst
BEA-25
25.0
RBEA-25
23.8
BEA-150
150.0
RBEA-150
176.4
nSiO /nAl
O
2 3
2
SBET (m2 g-1)
558
721
539
822
Total pore volume (V) (cm3/g)
Vmicro/Vmicro + Vmeso
Vmeso/Vmicro + Vmeso
Acidity (a0(NH3), µmol/g):
Total
0.486
0.340
0.662
0.625
0.200
0.800
0.588
0.260
0.743
0.792
0.180
0.824
1200
725
1179
704
180
97
233
95
Weak acid center
Strong acid center
475
475
83
138
TABLE-2
PARTICLE SIZE DISTRIBUTION IN SELECTED CATALYSTS
3.8×107
3.4×107
3.0×107
2.6×107
2.2×107
1.8×107
1.4×107
1.0×107
6000000
2000000
Average particle
size (nm)
Cumulative
volume (%)
Catalysts
BEA-150 (non-irradiated)
BEA-150
RBEA-150
367
103
240
91
96
90
8
5
6.741
10
12
14.143
12.222
Table-2 shows an almost homogeneous distribution of
crystallites by their sizes and by the direct influence of ultrasound,
the crystallites size decreased to the sizes of nanoparticles to
103 nm particularly for BEA-150.
4
11
1
4.861
6
6.020
9
7.9774
Ultrasonic and conventional catalytic activity in geraniol
conversion
13.790
3
2
5.844
5.751
0
5
6
7
8
9
Time
11
12
13
14
Composition of reaction products: The qualitative comp-
osition of the products of geraniol conversion is almost the same
in both for its purely catalytic and under combined ultrasonic
irradiation/catalyst transformations (Fig. 1). Basically, reaction
products of dehydration (terpene hydrocarbons are β-myrcene,
trans-β-cimene, β-ocimene, pseudolimonene), isomerization
(linalool and nerol) and carbon chain-extending (sesquiterpene
alcohols: farnesol, (2E,6E)-3,7,11-trimethyl-2,6,10-dodeca-
trien-1-ol and (2E,6E)-6,11-dimethyl- 2,6,10-dodecatrien-1-
ol.
Fig. 1. TI chromatogram of catalytic conversion products of geraniol on
micro-mesoporous zeolite R-BEA-25 (mcat/mgeraniol=1/142, reaction
carried out under simultaneous microwave and ultrasound irradiation
(MW/US, 550 W/300 W, in a argon atmosphere at 80 °C, run time:
1.5 h): (1) β-myrcene, C10H16, (2) pseudo-limonene, C10H16, (3) trans-
β-ocymene, C10H16, (4) β-ocymene, C10H16, (5) β-linalool, C10H18O,
(6) nerol, C10H18O, (7) cis-isogeraniol, C10H18O, (8) trans-geraniol,
C10H18O, (9) isopulegol, C10H18O, (10) trans,trans-farnesol, (2E,6E)-
3,7,11-trimethyl-2,6,10-dodecatrien-1-ol, C15H26O, (11) succinic acid,
di(neryl)ester, C24H38O4, (12) (2E,6E)-6,11-dimethyl-2,6,10-dodeca-
trien-1-ol, C14H24O
Sonochemical transformation of geraniol and the effect of
various solvents
Upon ultrasonic irradiation of geraniol itself, in contrast
to the conversion of geraniol on BEA-type zeolite, the formation
of any detectable quantities of sesquiterpene alcohols was not
observed viz., trans,trans-farnesol, ((2E,6E)-3,7,11-trimethyl-
2,6,10-dodecatrien-1-ol) and (2E,6E)-6,11-dimethyl-2,6,10-
dodecatrien-1-ol.
Effect of water and catalyst: The conversion of geraniol
(8 mL, 0.046 mol) in the presence of water (2 mL, 0.11 mol)
under the influence of ultrasound (300 W, 1.5 h, air and 71 º C)
showed a slight tendency to increase the conversion of geraniol
and the yield of nerol to 4.5 % and 2 %, respectively.
The conversion of geraniol (0.046 mol) and the yield of
linalool are increased respectively from 2 and 0.9 % to 10.4
and 7.0 % by the sonication (300W, 1.5 h, 71 ºC) in the presence
of the microporous zeolite catalyst (BEA-25, 0.05 g) and water
(0.11 mol).
Effect of ultrasonic and ultrasonic/microwave irradia-
tions: Geraniol (0.0230-0.0461 mol) upon ultrasonic irradi-
ation (argon atmosphere, run time 1.5 h, ultrasonic power 500-
700 W, temperatures 40-100 ºC) and combination of ultrasonic
and microwave irradiations (US 300 W/MW 550 W) was
slightly converted up to 2 %, mainly to terpene hydrocarbons
and also nerol with little yield was formed.
Effect of ultrasonic irradiation time and medium:With
the increasing of the ultrasound power from 350 to 700 W and
the irradiation time up to 1.5 h, the geraniol conversion degree
increases imperceptibly. The ultrasound irradiation at 80 ºC,
initiates oxidation processes with conversion degree of 2 %, a
negligible amount of oxidation products were formed viz., 2-
isopropenyl-5-methylhex-4-enal (C10H18O), 4,8-dimethyl-3,7-
nonadien-2-ol (C11H20O), oxacyclotetradeca-4,11-diyne. By incre-
asing the irradiation time up to 10 h conversion of geraniol was
6.4 % at 80 ºC and synthesized the oxidation product α-citral
with yield 1-2.5 % and terpene hydrocarbon β-myrcene. The
reaction medium (argon, air) has practically no effect on the degree
of conversion of geraniol when it is irradiated with ultrasound.
Effect of DMF: There is no sonochemical transformation
of geraniol at temperatures of 40 and 80 ºC, ultrasonic power
350 W, sonication time -1.5 h, in a dry solution of DMF and
under argon atmosphere.
Effect of methanol: In methanol solution with molar ratio
1/38.7 in air under ultrasonic irradiation with power 200-900

Vol. 31, No. 2 (2019)
Synergic Actions of BEA-Type Zeolites and Ultrasonic Irradiation in Conversion of Geraniol 441
TABLE-3
EFFECT OF METHANOL AND ZEOLITE CATALYST ON GERANIOL CONVERSION UNDER ULTRASONIC IRRADIATION
Yield/Selectivity (%)
t,°C/medium/
US power, W/
Run time, h
Content of reaction mixture
(Molar ratio)
Conversion
of G, %
Entry
Linalyl
Nerol
Neryl methyl
ether
β-Linalool
methyl ether
1*
2
4 mL G + 36 mL CH3OH
(0.023 /0.89)
1.5 mL G + BEA-25 (0.17
mol/g cat)
1.5 mL G + BEA-25 + 38.5 mL
CH3OH (0.17 mol/g cat/0.95)
1.5 mL G + BEA-25 + 38.5 mL
CH3OH (0.17 mol/g cat/0.95)
1.5 mL G + BEA-25 + 38.5 mL
CH3OH (0.17 mol/g cat/0.95)
25/Air/200-500-
600-900/0.5-1.5
27/N2 or air/1.0
1-2
3.3
–
0.7
–
–
1.2/36.4
5.8/21.8
5.8/21.5
5.7/21.9
2.1/63.6
–
–
3
30/Air/200/0.5
30/Air/200/1.0
40/Air/500/1.5
26.6
27.0
26.0
–
–
–
4.5/16.9
4.4/16.3
4.3/16.5
16.3/61.3
16.8/62.2
15.8/60.7
4
5
G-Geraniol; 1* - C11H18O, (3Z)-4,8-dimethylnona-3,7-dien-2-one, 0.5-0.9 %, α-citral and cis-iso-Geraniol, 0.4-0.4 %. In cases 2-5, a very small
amount of terpene hydrocarbons (C10H16) was obtained.
80
W, geraniol converted slightly into the oxidation product (3Z)-
Sonicated
4,8-dimethylnona-3,7-dien-2-one (C11H18O) and nerol. In argon
atmosphere, the geraniol molecule is resistant to ultrasound.
Effect of methanol and catalyst: The system consists of
catalyst, solvent and ultrasound, geraniol is actively converted
to linalool and methyl ethers of linalool and nerol (Table-3,
entries 3-5, Fig. 2). With the conversion of geraniol 27 %, the
selectivity for esters was about 80 % and for linalool 21%.
Ar, 40 °C
RBEA-25
BEA-25
RBEA-150
BEA-150
70
60
50
40
30
20
10
0
650000
600000
550000
500000
450000
400000
350000
300000
250000
200000
150000
100000
50000
5
8
3
6.721
6
4
1
6
4
2
7.113
0
2
1
5
4
1
1
Fig. 3. Conversion of geraniol under US irradiation on microporous BEA-
25, BEA-150 and micro-mesoporous RBEA-25, RBEA-150
zeolites, medium – Ar, catalyst loading –0.92 mol of geraniol/g
catalyst. US power –350 W (UMR-300B), run time –1.5 h,
temperature 40 °C
6
2
1
5.741
4.877
7
and 1-2 %, respectively; mainly the dehydration reaction proceeds
with the formation of terpene hydrocarbons of β-myrcene and
cis-β-ocimene. Conventional catalytic activities of these zeolite
catalysts were very small under the specified conditions.
However, degree of conversion of geraniol on BEA-150
and RBEA-150 at 80 ºC by ultrasonic treated is significantly
less than untreated samples (Fig. 4). The likely cause for this
may be a negative effect of temperature increase on the energy
of cavitation. It is a known existence of a temperature optimum
of the cavitation intensity for a particular system [15,20,21].
By the conversion values of geraniol at 80 ºC (Figs. 4 and
5), the following relative series of activity are obtained:
(A) RBEA-25 (24.6 %) ≥ RBEA-150 (23.9 %) > BEA-
25 (16.7 %) > BEA-150 (13.5 %), (conventional catalytic
activity, run time: 1.5 h).
(B) RBEA-25 (42.0 %) > BEA-25 (28.4 %) > RBEA-150
(6.9 %) > BEA-150 (1.5 %), (ultrasonic activation, ultrasonic
irradiation: 1.5 h).
Also conversion values for RBEA-25 was 49 %, (ultra-
sonic activation, ultrasonic irradiation: 5 h) and for RBEA-25
54.7 % (combined treated with microwave/ultrasonic 550 W/
300 W, 1.5 h).
Time
Fig. 2. TI Chromatogram of catalytic conversion products of geraniol on
microporous zeolite BEA-25 (mcat/mgeraniol = 1/26.7, reaction carried
out under ultrasound irradiation (US, 200 W, solvent – 38.5 mL
methanol, medium–air, temperature 30 °C, run time–1 h). 1 – β-
myrcene, C10H16, 2 – β-ocymene, C10H16, 3 – β-linalool, C10H18O, 4
– linalool, methyl ether, 5 – nerol, methyl ether, C11H20O, (2Z)-1-
methoxy-3,7-dimethylocta-2,6-diene, 6 – nerol, C10H18O, 7 – cis-
isogeraniol, C10H18O, 8– trans-geraniol, C10H18O
With the same quantity of BEA-25 (0.17 mol geraniol/g
catalyst), the conversion of geraniol is small i.e. 3.3 % (Table- 3,
entry 2) and increases nine times (entries 3-5) after the irradiation
with ultrasonic.
Sonochemical conversion of geraniol on micro-and micro-
mesoporous BEA-type zeolites
Effect of temperature under ultrasound irradiation:
The conversion of geraniol was achived by using ultrasonic
irradiation on micro- and micro-mesoporous beta-type zeolites
at 40 ºC (Fig. 3). It is obvious from Fig. 3 that at 40 ºC, nerol
is formed only on a microporous catalyst BEA-150 and the
conversion of geraniol and yields of linalool and nerol on ultra-
sonic irradiated zeolite catalysts at 40 ºC were small, 4-10.5

442 Ramishvili et al.
Asian J. Chem.
Non-irradiated, Ar, 80 °C
Sonicated, Ar, 80 °C
case of irradiated reactions, selectivity of isomerization from
conversion changes peculiarly; in particular with conversion
growth the selectivity increases on micro-mesoporous catalysts
(Fig. 6).
70
60
50
40
30
20
10
0
70
Conversion
60
Isomerization selectivity
50
40
30
20
10
0
RBEA-150
BEA-150
Fig. 4. Comparison of the conventional catalytic activity of zeolites (BEA-
150 and RBEA-150) with activity in irradiated reaction of geraniol
conversion; medium – US power –350 W (UMR-300B), Ar
atmosphere, catalyst loading– 0.92 mol of geraniol/g catalyst, run
time –1.5 h, temperature 80 °C
Fig. 6. Geraniol conversion under US (350 W, 1.5 and 5 h) and combined
US/MW (300 W/550 W, 1.5 h) irradiation in the presence of micro-
and micro- mesoporous beta-type zeolites. Effect of ultrasound
irradiation time on degree of geraniol conversion and selectivity
both to linalool and to nerol undividedly; reaction conditions: catalyst
loading – 0.92 mol of geraniol/g catalyst, argon atmosphere, run
time 1.5 h, 5.0 h, temperature 80 °C
60
1.5 h, non-irradiated
50
40
30
20
10
0
US, 1.5 h
US, 5 h
MW/US, 1.5 h
As the irradiation time increases from 1.5 to 5 h on RBEA-
25, the conversion of geraniol increases respectively from 42 to
49%, the isomerization selectivity almost does not change,
ratio of selectivity of linalool to selectivity of nerol (L/N) was
nearly same as 1.3 and 1.1, respectively (Figs. 6 and 7). At the
simultaneous combined irradiation of geraniol by ultrasound
and microwaves (US 300 W/MW 550 W) in case of RBEA-
25, conversion increased to 54.7 % with isomerization selec-
tivity up to 49.7 % with 47 % being the isomerization selectivity
for linalool (Figs. 6 and 7).
RBEA-25
BEA-25
Fig. 5. Comparison of catalytic activities (at 80 °C, medium – Ar) of non-
irradiated and irradiated with ultrasound zeolites (RBEA-25 and
BEA-25) in reaction of geraniol conversion by • irradiation during
1.5 h, US power- 350 W, • irradiation during 5 h, • with combined
US/MW irradiation during 1.5 h, US power - 300 W, MW power-
550 W
60
Conversion
50
Selectivity to Linalool
Selectivity to Nerol
40
30
20
10
0
Under both conditions, the thermocatalytic conversion of
geraniol and its ultrasonic activation on the investigated catalysts,
the largest conversion of geraniol (42 % and 24.6 %, respectively)
was on a micro-mesoporous catalyst RBEA-25 and the smallest
on a microporous BEA-150 (13.5 and 1.5%, respectively). The
first of them has the highest total acidity (1179 µmol/g) and a
large pore surface (721 m2/g) (Table-1).
The investigated zeolites easily dissolved in geraniol and
after ultrasonic irradiation of geraniol/zeolite solution, a time-
stable ultra-disperse systems of zeolite were formed. The soni-
cation leads to an increase in the degree of dispersion of zeolite
samples; for example, for BEA-150 and RBEA-150, grain sizes
after sonication are reduced to 103 and 240 nm, respectively,
whereas for non-irradiated BEA-150 sample they are 367 nm
(Table-2). An established opinion in the literature that the
cavitation can lead to a structural change in the catalytic centers
of a solid and to change even the direction of the process [11].
Effect of ultrasonic and combined ultasonic/microwave
irradiations on conversion and isomerization selectivity:
On the most active catalysts RBEA-25 and BEA-25 in the
Fig. 7. Geraniol conversion under US (350W) and combined US/MW (300
W/550 W) irradiations in the presence of micro- and micro-
mesoporous beta-type zeolites. Effect of ultrasound irradiation time
on degree of geraniol conversion and selectivity to linalool and to
nerol; reaction conditions – catalyst loading –0.92 mol of geraniol/g
catalyst, argon atmosphere, run time 1.5 h, 5.0 h, temperature 80 °C
In conventional catalytic conversion of geraniol on zeolites
investigated at 80 ºC, the ratio L/N decreases from micro-
mesoporous catalysts to the corresponding microporous samples;

Vol. 31, No. 2 (2019)
Synergic Actions of BEA-Type Zeolites and Ultrasonic Irradiation in Conversion of Geraniol 443
60
upon the ultrasound irradiation of geraniol on zeolite catalysts
there is a large tendency of growth of nerol selectivity; in parti-
cular, at a contact time of 1.5 h for non-irradiated reaction for
RBEA-25 ratio L/N was 3.7 at conversion 24.6 % and selec-
tivity for nerol 4.5 % at 80 ºC. Under the same conditions by
the sonicated reaction for this catalyst, the ratio L/N was less,
equal 1.3, conversion 42 % and selectivity to nerol 28.8 %. By
microwave/ultrasonce irradiation on RBEA-25 the ratio L/N
was very large, equal to 17.4, however, accordingly the selec-
tivity for nerol was less, equal to 2.7 and for linalool 47 %. Thus
in this case there is regioselectivity by linalool (Figs. 7 and 8).
Conversion
Linalool
C15H26O
C14H24O
C10H16
50
40
30
20
10
0
Nerol
Squalene
RBEA-25
70
Conversion (%)
60
Isomerization
selectivity (%)
50
Isomerisazion
products yields (%)
40
Ratio of selectivities,
Fig. 9. Comparison of geraniol conversions and yields of products in
reactions on beta-type zeolite catalysts. Reaction conditions:
ultrasonic irradiation (350 W, 1.5 h; 5 h), without it (non-irradiated,
1.5 h) and simultaneous MW/US (550 W/300 W, 1.5 h) irradiation;
catalyst loading – 0.92 mol of geraniol/g catalyst, argon atmosphere,
run time –1.5 h, 5.0 h, temperature – 80 °C
L/N
30
20
10
0
MW/US 1.5 h
US 5 h
US 1.5 h
Non-irradiated
1.5 h
atmosphere (argon, nitrogen, air) does not affect the conversion
degree of geraniol. In argon atmosphere and in DMF and methanol
solutions, geraniol is resistant to ultrasound. Due to synergy
of action in the system: zeolite catalyst BEA-25, solvent CH3OH
and ultrasound irradiation (200 W, 0.5 h, air, 30 ºC), geraniol
is actively converted (27 %) to linalool and linalyl and finally
to neryl methyl ethers with the yields of 6 and 21 %, respectively
at 30 ºC. In the conversion of geraniol (0.9220 mol of geraniol/g
catalyst) on the zeolite catalyst BEA-25 by presence of water
and by sonication (300W, 1.5 h, air, 71 ºC), the conversion
and yield of linalool reached up to 10.4 and 7.0 %, respectively.
The synergism between the action of ultrasonic irradiation (US
power 350 W, 1.5 h, Ar, 80 ºC) and BEA-type zeolite catalyst
RBEA-25, caused to obtain increased yields up to 31 % and
selectivity for linalool and nerol up to 63.2 % at conversion of
49 % in the isomerization of geraniol; while the yields of sesqui-
terpene alcohols C14H24O and C15H26O remain at the level of
the non-irradiated reaction (about 15 %).
In comparison with non-irradiated reaction on RBEA-25,
the combined action of ultrasound and zeolite, also increased
selectivity towards nerol from 4.5 to 30 %. Due to the synergic
effect between catalyst RBEA-25 and ultasonic/microwave
(US 300 W MW 550 W/, 1.5 h, Ar, 80 ºC), conversion to 54.7
%, yields of linalool and nerol to 27.2 and sesquiterpene alcohols
to 21.9 % were increased; at the same time, the selectivity
ratio linalool/nerol (L/N) increased to 17.4 and the regiosel-
ectivity for linalool is manifested. The combination of ultasonic
irradiation separately with RBEA-150 and BEA-150 catalysts
gives an inhibitory effect i.e. a decrease in the conversion and
yields of reaction products, a strong increase in the L/N ratio.
Under ultasonic irradiation on samples of micro- and micro-
mesoporous zeolites of BEA-type with a higher acidity and a
pore surface, activation of catalytic properties (conversion,
selectivity, yields) in isomerization of geraniol is observed;
on samples of the same catalysts with low acidity and pore
surface, there is in the same reaction inhibition of the catalytic
properties of the zeolite.
Fig. 8. Comparison of activities of different combined systems with micro-
mesoporous zeolite RBEA-25 in the conversion of geraniol. Reac-
tion conditions: catalyst loading – 0.92 mol of geraniol/g catalyst,
argon atmosphere, run time –1.5 h, 5.0 h, temperature – 80 °C, US
(350 W), US/MW (300 W/550 W)
Effect of ultrasonic and hybrid ultrasonic/microwave
irradiations on yields of products of geraniol conversion:
In case of irradiated reactions, the yields of linalool and nerol
increased along with the conversion (Fig. 9).Yields of isomeri-
zation reaction products (linalool and nerol), under ultrasonic
activation were higher on zeolites studied with a higher total
acidity on RBEA-25 and BEA-25, 26 and 15.8 %, respectively,
which is almost 3-5 times greater than in non-irradiated reaction.
In case of RBEA-150 and BEA-150 yields of linalool and nerol
were insignificant: 1.6 and 0.8 %. Under the same conditions,
in non-irradiated reaction on RBEA-25 and BEA-25 yields of
linalool and nerol were smaller: 5.2-5.3 %. On RBEA-25 and
BEA-25 in non-irradiated and irradiated reactions yields of
sesquiterpene alcohols (C14H24O and C15H26O) were almost
identical, 17 and 12 %, respectively.
With an increase in irradiation time from 1.5 to 5 h, the
yields of linalool and nerol on RBEA-25 increased to 31 %, mainly
due to the formation of linalool. By ultrasonic/microwave irradi-
ation on RBEA-25 the yields of isomerization products increased
to 27.2 % and of sesquiterpene alcohols (C14H24O and C15H26O)
to 21.9 % (Fig. 9).
Conclusion
The geraniol conversion reaction was initiated by the
simultaneous action of micro- and micro-mesoporous beta-
type zeolites and US irradiation with a power of 200-900 W
and a ultasonic frequency of 25 kHz (UMR-300B hybrid reactor,
Shinka, Japan) and in the ultrasonic reactor SRF-1(Shinka)
with a US power of 100 W and a different frequency (20, 40,
60 kHz). Upon ultrasonic irradiation (100-900 W, 27-100 ºC)
geraniol was slightly converted up to 2 %, mainly in terpene
hydrocarbons and also in nerol with little yield. The irradiation

444 Ramishvili et al.
ACKNOWLEDGEMENTS
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The authors gratefully acknowledge the financial support
from Shota Rustaveli National Science Foundation of Georgia
(Project #217868).
CONFLICT OF INTEREST
https://doi.org/10.1039/cs9972600443.
The authors declare that there is no conflict of interests
regarding the publication of this article.
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