Valorisation of vegetable oils via metathesis reactions on solid catalysts: Cross-metathesis of methyl oleate with 1-hexene

Article abstract of DOI:10.1016/j.apcata.2015.06.021

Abstract The activity and selectivity of silica-supported Hoveyda-Grubbs (HG) complex for the cross-metathesis of methyl oleate with 1-hexene to obtain 1-decene, methyl 9-tetradecenoate, 5-tetradecene and methyl 9-decenoate were studied in a batch reactor. The HG complex loading was varied between 0.87 and 11.6 wt%. Competitive secondary reactions were the self-metathesis of methyl oleate and the self-metathesis of 1-hexene. The yield to cross-metathesis products (η_C-M) was 47% when a 1-hexene/methyl oleate reactant ratio (R_C6/MO) of one was employed. The η_C-M value increased with increasing 1-hexene initial concentration, reaching 87% for R_C6/MO = 7. The selectivity to terminal olefins also increased at the expense of internal olefins among the cross-metathesis products when the concentration of 1-hexene was increased.

Full text of DOI:10.1016/j.apcata.2015.06.021

Accepted Manuscript
Title: Valorisation of vegetable oils via metathesis reactions on
solid catalysts: Cross-metathesis of methyl oleate with
1-hexene
´
Author: J. Zelin P.D. Nieres A.F. Trasarti C.R. Apesteguıa
PII:
S0926-860X(15)30037-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2015.06.021
APCATA 15433
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
5-5-2015
2-6-2015
16-6-2015
´
Please cite this article as: J.Zelin, P.D.Nieres, A.F.Trasarti, C.R.Apesteguia,
Valorisation of vegetable oils via metathesis reactions on solid catalysts: Cross-
metathesis of methyl oleate with 1-hexene, Applied Catalysis A, General
http://dx.doi.org/10.1016/j.apcata.2015.06.021
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Valorisation of vegetable oils via metathesis reactions on solid
catalysts: Cross-metathesis of methyl oleate with 1-hexene
J. Zelin, P.D. Nieres, A.F. Trasarti, C.R. Apesteguía*
Catalysis Science and Engineering Research Group (GICIC),
INCAPE, UNL-CONICET, Predio CCT Conicet, Paraje El Pozo,
(3000) Santa Fe, Argentina
Sent to Applied Catalysis A: General
* Corresponding author
Prof. Carlos Apesteguía
INCAPE
Predio CCT Conicet, Paraje El Pozo
(3000) Santa Fe, Argentina
Email: capesteg@fiq.unl.edu.ar
Website:http://www.fiq.unl.edu.ar/gicic
Phone: 54-342-451-1370, Fax: 54-342-4531068
1

Graphical abstract
Highlights
 MO/1-hexene cross-metathesis is efficiently promoted on Hoveyda-Grubbs
(HG)/SiO2
 Yields to cross-metathesisproducts of 87% are obtained
 The selectivity to cross-metathesisproductsincreases with the 1-hexene/MO ratio
 HG/SiO2 deactivation is pronounced for 1-hexene/MO ratios higher than 3
Abstract
The activity and selectivity of silica-supported Hoveyda-Grubbs (HG) complex for the
cross-metathesis of methyl oleate with 1-hexene to obtain 1-decene, methyl 9-
tetradecenoate, 5-tetradecene and methyl 9-decenoate were studied in a batch reactor.
The HG complex loading was varied between 0.87 and 11.6 wt%. Competitive
secondary reactions were the self-metathesis of methyl oleate and the self-metathesis of
1-hexene. The yield to cross-metathesis products (ηꢀꢁꢂ) was 47% when a 1-
hexene/methyl oleate reactant ratio (RC6/MO) of one was employed. The ηꢀꢁꢂvalue
2

increased with increasing 1-hexene initial concentration, reaching 87% for RC6/MO= 7.
The selectivity to terminal olefins also increased at the expense of internal olefins
among the cross-metathesis products when the concentration of 1-hexene was increased.
Keywords:Cross-metathesis, Methyl oleate, 1-Hexene, Hoveyda-Grubbs catalysts,
Oleochemistry, FAME
3

1- Introduction
Metathesis reactions are becoming increasingly attractive in the oleochemistry
industry because they offer novel routes for the valorisation of unsaturated fatty acid
methyl esters (FAME) that are cheap feedstocks obtained by transesterification of
natural oils and fats [1]. Homogeneous catalysis has been successfully employed for
what is FAME metathesis, especially using Grubbs’ Ru complexes [2] and second
generation ruthenium Hoveyda-Grubbs (HG) catalysts (Figure 1) that are remarkably
tolerant to the presence of moisture and oxygen [3,4]. However,the industrial
application of homogeneous olefin metathesis catalysts is hampered bythe expensive
catalyst separation processes needed to obtain high-purity chemicals and the
contamination of products by Ru catalyst residues that are difficult to
eliminate.Therefore, increasing research efforts have been made lately for developing
active and stable immobilized supported complexes that allow straightforward catalyst
separation and recovery. For example, commercial available Ru-alkylidene complexes
immobilized on different supports have been employed without leaching or significant
activity loss for olefin metathesis reactions [5,6,7]. Recently, we reported that silica-
supported HG complexesare stable, highly active and selective catalysts for the self-
metathesisof methyl oleate [8].
.
Cross-metathesis of FAME with lower olefins allows shortening of the long-
chain FAME molecules to form less abundant medium-chain fatty acid esters that are
valuable intermediates in fine chemistry [9]. Most of the work on cross-metathesis of
oil-derived unsaturated esters with simple alkenes has been carried out using
homogeneous ruthenium-based catalysts. In particular, the metathesis of methyl oleate
(MO) with ethylene (ethenolysis) and with 2-butene were investigated on Ru complexes
4

[10,11,12]while the cross-metathesis of MO with 1-hexene was studied on
homogeneousWCl6/(CH3)4Sn catalysts [13]. In heterogeneous catalysis, the ethenolysis
of MO was performed on Re2O7/Al2O3and on CH3ReO3 supported on SiO2-
Al2O3[14,15],but there are no reportson the use of immobilized Ru complexes for
promoting the cross-metathesis of MO with olefins. Precisely, in this work we study the
cross-metathesis of MO with 1-hexene (C6) on second generation RuHoveyda-Grubbs
complexes supported onsilica. This metathesis reaction produces 1-decene (1-DC),
methyl 9-tetradecenoate (9-TDE), 5-tetradecene (5-TDC) and methyl 9-decenoate (9-
DCE), as depicted in Scheme 1.9-TDE is used for the synthesis of pheromones such as
cis/trans-9-tetradecenal and cis-9-tetradecenol, which are non-toxic and biodegradable
chemicals increasingly employed for the control of insect pests[16]. The synthesis route
to pheromones via metathesis reactions is a one- to three-steps alternative to the current
conventional technologies that employ multistep sequences[17]. 9-DCE is a valuable
intermediate for the synthesis of fragrances and prostaglandins and is also employed in
the polymer industry [18,19]. Secondary reactions in the MO/C6 cross-metathesis
reaction network are the self-metathesis of MO that produces 9-octadecene (OCT) and
dimethyl 9-octadecen-1,18-dioate (9-OD),and the self-metathesis of C6 yielding 5-
decene (5-DC) and ethylene (Scheme 1).The results presented in this work show that
high yields (87%) and selectivities (93%) to MO/C6 cross-metathesis products are
obtained on HG/SiO2 catalysts when using high C6 concentrations to suppress
secondary self-metathesis reactions.
5

2- Experimental
2.1- Catalyst preparation and characterization
HG/SiO2catalysts were prepared by impregnating acommercial silica (Sigma-
Aldrich G62, 230 m2/g, 200 mesh) with a solution of HG (Sigma-Aldrich, 97%) in
cyclohexane.The silica impregnation was carried out at 298 K by stirring during 30 min;
the solid colour rapidly changed from white to green and was then filtered and dried in
vacuum. HG/SiO2 samples containing different HG amounts (between 0.87 and 11.6
wt.% HG) were prepared. The HG loading on HG/SiO2 samples was determined by
measuring by UV-vis spectroscopy (Perkin-Elmer Lambda 20 spectrophotometer) the
colorimetric difference of the HG impregnating solution, before and after
impregnation.The crystalline structure of the samples was determined by X-ray
diffraction (XRD) using a Shimadzu XD-D1 diffractometer and Ni-filtered Cu Kα
radiation.
HG/SiO2 samples were characterized by Fourier transform infrared spectroscopy
(FTIR) usinga Shimadzu Prestige 21 spectrophotometer. The spectral resolution was 4
cm-1 and 140 scans were added. Powder sampleswere mixed with KBr and pressed to
thin wafers. Spectra were taken at room temperature by subtracting the background
spectrum recorded previously.
The interaction between the HG complex and the silica support was studied by
diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using a Shimadzu
IRPrestige-21 spectrophotometer, equipped with an in-situ high-temperature/high
pressure SpectraTech cell and a liquid nitrogen-cooled MCT detector. The sample
6

holder was placed inside a dome with CaF2 windows. The DRIFT spectra were
collected in Ar (60 ml/ min). The spectrum of silica support was previously collected.
The IR spectrashowed in this paper for HG/SiO2samples are the difference spectra
where the SiO2 spectrum served as the reference.
2.2 Catalytic reactions
The cross-metathesis of methyl oleate (Sigma-Aldrich, 99%) with 1-hexene
(Sigma-Aldrich, 99%)was carried out at 303 K and 101.3 kPa in a glass batch reactor
under Ar atmosphere. Cyclohexane (Sigma-Aldrich, anhydrous 99.5%) previously
dehydrated withmetallic Na and benzophenone under reflux was used as solvent.The
reactor was loaded at room temperature with variable amounts of MO, C6 and catalyst
together with cyclohexane (10 ml) and n-dodecane (internal standard). Then the reaction
mixture was stirred and heated to the reaction temperature in a thermostatic bath.
Reaction products were analyzed by ex-situ gas chromatography in an Agilent 6850 GC
chromatograph equipped with a flame ionization detector and a 50 m HP-1 capillary
column (50 m × 0.32 mm ID, 1.05 μm film). Samples from the reactionsystem were
collected periodically for 40-250 min.Product identification was carried out using gas
chromatography coupled with mass spectrometry (Varian Saturn 2000) both equipped
with a VF5-HT capillary column. Besides the cross-metathesis reaction products (1-DC,
9-TDE, 5-TDC and 9-DCE) it was detected the formation of 9-OD and 9-OCT from the
self-metathesis of MO, and 5-DC from the self-metathesis of C6. All the product yields
were calculated in carbon basis. The yield to MO/C6 cross-metathesis products (ꢃꢄꢁꢅ
,
C atoms of cross-metathesis products formed/C atoms of MO fed) was determined
∑
 ꢇ
ꢆ
ꢆ
asꢃꢄꢁꢅ
=
, where niare the moles ofproductiformed from the cross-metathesis
ꢊ

ꢇ
ꢈꢉ
ꢈꢉ
7

reaction, ithe number of C atoms in the product i molecule, ꢋꢅꢍ ꢌthe initial moles of
MO, and OMthe number of C atoms in the MO molecule. The yield to MO self-
∑
 ꢇ
ꢏ
ꢏ
metathesis products was obtained as ꢃꢎꢁꢅꢌ
=
, where njare the moles of
ꢊ

ꢈꢉ
ꢇ
ꢈꢉ
product j formed from the MO self-metathesis reaction andj number of C atoms in the
product j molecule. The yield to C6 self-metathesis productswas calculated as ꢃꢎꢁꢄꢐ
=
∑
 ꢇ
ꢑ
ꢑ , where nkare moles of product k formed from the C6 self-metathesis reaction,
ꢊ

ꢒꢓ
ꢇ
ꢒꢓ
kthe number of C atoms in the product k molecule, n0 the initial moles of C6, and
C6
C6the number of C atoms in the C6 molecule. The selectivity to MO/C6 cross-
ꢕ
ꢈꢒ
metathesis products wasobtained as ꢔꢄꢁꢅ
=
, where Xꢂꢗ is the conversion of MO;
ꢖ
ꢈꢉ
similarly the selectivities to the self-metathesis products of MO and C6 where
ꢕ
ꢕ
calculated as ꢔꢎꢁꢅꢌ
= =
ꢘꢙꢈꢉ and ꢔꢎꢁꢄꢐ ꢘꢙꢒꢓ , respectively.
ꢖ
ꢖ
ꢒꢓ
ꢈꢉ
The self-metathesis of methyl oleate and 1-hexene were carried out using the
same reaction unit, analysis system and operation conditions than those described above
for the MO/C6 cross-metathesis reaction.
3- Results and Discussion
3.1 Catalyst characterization
The HG loading of HG/SiO2 samples used in this work was between 0.87 and
11.6 %wt. We determinedexperimentally the HG monolayer value by
successivelyadding at 298 Ksmall amounts of a 0.68x10-3 M HG/cyclohexane solution
8

to 100 mg of SiO2 placed in 3 ml of cyclohexane into a stirred beaker. We analyzed the
supernatantsolution after every HG addition by UV-vis spectroscopy following the 570
nm absorbance signal (maximum absorbance of HG complex) until detecting the
presenceof the HG complex. The value of the HG monolayer obtained from this
experiment was about 11.6% (Fig.2).
In Fig.3 we present the XRD diffractograms corresponding to SiO2, HG complex
[20],and HG/SiO2 samples containing 0.87, 2.24, 6.0 and 11.6 %HG. All the HG/SiO2
samples exhibited only the amorphous halo of SiO2 support. The absence of XRD peaks
due to HG crystalline structure suggests that the HG complex is highly dispersed on the
silica support, as it was reported previously[5].
Fig.4shows the FTIR spectra of HG complex, SiO2, HG(6.0%)/SiO2 and
HG(11.6%)/SiO2obtained in the 500-800 cm-1 region. In this region, the HG complex
exhibits the 748 cm-1band characteristics of the Ru=C bond stretch, and the absorption
band at 580 cm-1 resulting from the Ru-C vibration [21]. Both IR bands at 748 and 580
cm-1were also detected on HG/SiO2 samples thereby suggesting that the HG structure
was preserved after its deposition on silica.
More knowledge on the interaction between the HG complex and the support
was obtained using DRIFT spectroscopy. Spectra of the HG complex and HG/SiO2
samples (0.87, 6.0 and 11.6 %HG) obtained at 303 K in the 1000-3500 cm-1 region, are
shown in Fig. 5. In agreement with literature [22], the main absorption bands of the HG
complex appeared in the 1200-1700 cm-1and 2800-3200 cm-1 regions.In the 1200-1700
cm-1 region, the bands at 1454 cm−1, 1392 cm-1and 1298 cm−1are attributable tov(C=C)
1
aromatic, δ(CH3) and δ(CH2), respectively.In the 2800-3200 cm− zone, the IR bands at
1
1
2945 cm− and 2976 cm− correspond to v(CH3, CH2) asymmetric and v(CH3, CH2)
symmetric stretches. Fig. 5 shows that the main absorption bands of the HG complex
9

appeared in the spectra of HG(6.0%)/SiO2 and HG(11.6%)/SiO2 samples,thereby
confirming that the HG ligands and structure were conserved after the HG impregnation
on the support. In contrast, the IR bands characteristics of the HG complex were not
detected on HG(0.87%)/SiO2, probably because of the low HG loading.
3.2 Catalytic results
3.2.1 Self-metathesis of methyl oleate and 1-hexene
The reaction network inScheme 1 shows that the self-metathesis of MO and C6 are
detrimental secondary reactions when the research goal is to selectively produce MO/C6
cross-metathesis products. Therefore, we initially investigated the activity of HG/SiO2
catalysts for both self-metathesis reactions. It is significant to note here that in a
previous study of the self-metathesis of MO on HG/SiO2 catalysts [8] we verified that
there is not lixiviation of the HG complex when cyclohexane is used as the solvent,
which in agreement with results reported by other authors [5]. Details of the
experiments carried out for verifying that the results obtained for metathesis reactions
in cyclohexane on HG/SiO2 catalysts effectively reflect the activity of immobilized HG
complex are reported in [8].Fig. 6 presents the conversion vs time curves obtained on
HG(0.87%)/SiO2 at 303 K.The MO conversion rapidly reached the equilibrium value of
50% [8] indicating that HG(0.87%)/SiO2is very active for the self-metathesis of MO.
The self-metathesis of C6 is not limited by equilibrium because one of the reaction
products, ethylene, is continuously removed from the gas phase. However, the C6
conversion on HG(0.87%)/SiO2 remained almost constant (XC6 3%)after 90 min on
stream, thereby suggesting a rapid in situ catalyst deactivation.The deactivation of HG-
based catalysts in presence of terminal olefins has also been observed by other authors
10

and was attributed to the low stability of methylidene intermediatesleading to hydride
species that suppress the metathesis cycle[23, 24].
3.2.2. Reaction equilibrium
Cross-metathesis reactions are often limited by equilibrium. Here, we
determined experimentally the equilibrium of the reaction depicted in Scheme 1because
there are no data in this regard to our knowledge. The MO/C6 cross-metathesis reaction
was carried out at 303 K using dissolved HG and HG(1.12%)/SiO2catalysts. Similar HG
amounts were employed in both catalytic tests; results are shown in Fig.7. When the
reaction was performed in homogeneous phase, XMO remained constant after rapidly
reaching a value of 0.67 (Fig.7a); to verify that the reaction had reached the equilibrium,
we added to the reactor 5.4x10-7 mol of the HG complex after 120 min ofreaction and
we observed that XMO was not modified by the additionof catalyst. The MO conversion
on HG(1.12%)/SiO2 reached initially only 51%, but following the addition of 30 mg of
catalyst after 175 min of reaction XMO increased to 67% and remained constant even
after a second addition of catalyst (Fig.7b). From the results ofFig.7it is inferred that the
MO equilibrium conversion for the reaction of Scheme 1, at 303 K and a reactant ratio
RC6/MO=1, is 67%. By employing ꢚꢛꢜ = 0.67, we calculated the equilibrium constant
ꢅꢌ
corresponding to the reaction of Scheme 1 that involves three competitive reactions: the
MO/C6 cross-metathesis, the self-metathesis of MO and the self-metathesis of C6; we
obtained a value of KEq = 0.69. Finally, using the KEq valueof 0.69 we calculated the
XMOequilibrium conversions for other RC6/MOratios used in this work; the obtained
ꢚꢅꢛꢜꢌvalues are included in Table 1.
It is worth noting here that the rapid catalyst deactivation noticed in Fig. 6for the
self-metathesis of C6 was not observed in Fig. 7b for the MO/C6 reaction on
11

HG(1.12%)/SiO2. This result strongly suggests that the competitive adsorption between
MO and C6 for the HG(1.12%)/SiO2active sites decreases the rate of deactivation
reaction that takes place when 1-hexene is the only reaction reactant.
3.2.3. Cross-metathesis of methyl oleate with 1-hexene
We initially studied the effect of the HG loading on the MO conversion rate for
the cross-metathesis of MO with C6 using HG/SiO2 catalystscontaining between 2.24
and 3.36 %HG. Fig. 8 shows the evolution of XMO as a function of parameter
tWHG/ꢋꢅꢍ ꢌ(h gHG/mol) where t is the reactiontime, WHGis the HGloading, and ꢋꢅꢍ ꢌ are
the initial moles of MO.The local slope of each curve in Fig.8 gives the MO conversion
rateat a specific value of MO conversion and reaction time. The curves of Fig.8
exhibitedthe same initial slopes, i.e. the same initial MO conversion rates (ꢝꢅꢍꢌ, mol/h
gHG).This result reveals that the HG complex deposited on silica was completely
accessible and active for promoting the MO/C6 cross-metathesis reaction. The ꢝꢅꢍꢌvalue
determined from the curves of Fig. 8 was 2.4 mol/h gHG. On HG(3.36%)/SiO2, XMO
rapidly reached the equilibrium value for RC6/MO = 5 (91%). In contrast, XMO attained
only 81% and 77% on HG(2.80%)/SiO2 and HG(2.24%)/SiO2, respectively, thereby
indicating that both samples were deactivated during the progress of the reaction,
probably because of the presence of 1-hexene as it was observed for the C6 self-
metathesis reaction in Fig. 6.
AdditionalMO/C6 cross-metathesis catalytic runs were performed on
HG(3.36%)/SiO2at 303 Kto determine the reaction order with respect to1-hexene.The
reaction order was obtained from Equation 1 that represents the initial MO conversion
rate:
12

ꢝꢅꢍꢌ = ꢞ (ꢟꢄꢍꢐ)ꢠ(ꢟꢅꢍꢌ
)
(1)
ꢡ
The dependence of ꢝꢅꢍꢌ upon C6 was studied by varying C6 between 0.058 and 0.203
mol/L at ꢟꢅꢍꢌ= 0.029 mol/L.The plot representing ln ꢝꢅꢍꢌ as a function of lnꢟꢄꢍꢐis shown
in Fig. 9. Reaction order determined from the logarithmic plot ofFig. 9 was slightly
negative, about -0.1.
The effect of the RC6/MOreactant ratio on the MO/C6 cross-metathesisreaction
was studiedon HG(3.36%)/SiO2at 303 K, using the same initial MO concentration,Cꢂꢍ ꢗ
=
0.029 M; RC6/MOwas varied between 1 and 7. In Fig. 10we show the evolution as a
function of time of MO and C6 conversions (XMO, XC6) and yields to cross-metathesis
(C-M), MO self-metathesis (S-MO) and C6 self-metathesis (S-C6) products obtained for
RC6/MO = 1. When XMO reached the equilibrium(67%), the C-M and S-MO values were
46 and 21%, respectively.With the aim of improving the yield to cross-metathesis
products, we decidedto perform additional runs at increasing RC6/MO reactant ratios.We
speculated that C-Mmay increase by increasing the C6 concentration because of the
following reasons: i) the equilibrium of the MO/C6 cross-metathesis reaction is shifted
to higher MO conversions whenRC6/MO is increased; ii)the rate of MO self-metathesis
probably will diminish with C6 concentration because the competitive C6 adsorption on
the catalystwould reduce the pairs of adjacent surface active sites required for
promoting this reaction.The values of MO and C6 conversions, yields, selectivities and
carbon balances obtained at the end of the runs forRC6/MOreactant ratios between 1 and 7
are presented in Table 1.As shown in Table 1, the MO equilibrium conversionincreases
from 67% (RC6/MO =1) to 97% (RC6/MO = 7); the MO conversions obtained in the
catalytic runs reached the Xꢢꢣ valuesfor RC6/MO between 1 and 5 and close to Xꢂꢢꢣꢗfor
ꢂꢗ
RC6/MO 6 and 7. C-M increased from 46% (RC6/MO =1) to 87 % (RC6/MO = 7) at the
13

expense of S-MO, thereby confirming that the self- metathesis of MO is inhibited when
the C6 concentration is increased. Consistently, the selectivity to cross-metathesis
products, SC-M, increased from 59 to 93% when RC6/MO was varied from 1 to 7. As
expected, the yield and selectivity to C6 self-metathesis products increased with
increasing C6 concentration. In all the cases, the carbon balance was  94%.
In Fig. 11we present the i vs time curves obtained for four different RC6/MO
ratios (2, 4, 5 and 7), where i is the yieldof productiformed from the conversion of MO
via either the MO/C6 cross-metathesis orthe MO self-metathesis.The yields to 9-OCT
and 9-OD, the products of self-metathesis of MO, clearly decreased when RC6/MOwas
increased. Regarding the MO/C6 cross-metathesis products, Fig.11reveals that the yield
to terminal olefins 1-DC and 9-DCE increaseswhile that to internal olefins 9-TDE and
5-TDC remains almost constant when RC6/MOis increased. In Fig. 12we have
represented theyield to MO/C6 cross-metathesis products as a function of RC6/MO
,
discriminating between terminal and internal olefins. The yield to terminal olefins
increased from 28% (RC6/MO = 1) to 62% (RC6/MO = 7); in contrast, the yield to internal
olefins oscillated between 23 and 27% in this RC6/MO range.The preferential formation
of terminal olefins among the MO/C6 cross-metathesis products with RC6/MO is probably
related to the concomitant increase of the concentration of C6 self-metathesis products,
in particular ethylene [Table 1]. In fact, the concentration of 5-DC increased from
3.7x10-3mol/L (RC6/MO = 1) to 13.5x10-3 mol/L (RC6/MO = 7) and similar ethylene
amounts are formed from C6 self-metathesis reaction (Scheme 1). The consecutive
metathesis of ethylenewith internal olefins 9-TDE and 5-TDC would produce then C6
and terminal olefins 1-DC and 9-DCE.In summary, increasing the C6 concentration
improves the yield and selectivity to MO/C6 cross-metathesis products, in particular to
terminal olefins.
14

However, results in Fig. 8and Table 1(columns 3 and 4) indicate that the
deactivation of HG/SiO2 catalysts becomes significant when high RC6/MOratios are used.
In order to gain more knowledge on the effect ofRC6/MOon catalyst deactivation, we
performed additional catalytic runs of the MO/C6 cross-metathesis reaction using
ꢛꢜ
HG(1.12%)/SiO2 catalysts. We employed the parameter (ꢚꢅꢛꢜꢌ − ꢚꢅꢤꢌ) ꢚꢅꢌ as a
ꢥ
quantitative measure of catalyst deactivation, where ꢚꢅꢤꢌis the OM conversion achieved
at the end of the 120-min runs. Results are presented in Fig. 13and show that the HG
complex is deactivated during the progress of the reaction. The catalyst deactivation
increased with RC6/MO ratio,which supports the assumption that the presence of terminal
olefins may suppress the metathesis cycleon HG-based catalysts, as noted above.Fig.
13also suggests that deactivation of HG/SiO2 catalysts may be critical when
RC6/MOratios higher than three are employed.
4- Conclusions
The selective synthesis of methyl oleate/1-hexene cross-metathesisproducts (1-
decene, methyl 9-tetradecenoate, 5-tetradecene and methyl 9-decenoate) on HG/SiO2
catalysts is improved by using high 1-hexene/methyl oleate ratios. The increase of 1-
hexene concentration shifts the reaction equilibrium to high MO conversion equilibrium
values and concomitantly suppresses the MO self-metathesis competitive reaction.
Thus, the yield and selectivity to MO/C6 cross-metathesis products reported in this
work on HG(3.36%)/SiO2for a RC6/MO ratioof seven are 87% and 93%, respectively. The
product distribution also depends on RC6/MO ratio; in fact, the yield to terminal olefins
(9-decenoate, 1-decene) increases from 28% (RC6/MO = 1) to 62% (RC6/MO = 7) while
15

that of internal olefins (9-tetradecenoate, 5-tetradecene) does not change significantly.
Nevertheless, deactivation of HG/SiO2 catalysts also increases with 1-hexene
concentration and for C6/OM reactant ratios higher than three becomes more
pronounced.
Acknowledgements
Authors thank the Universidad Nacional del Litoral (UNL), Consejo Nacional de
Investigaciones Cientificas y Tecnicas (CONICET), and Agencia Nacional de
Promoción Cientifica y Tecnologica (ANPCyT), Argentina, for the financial support of
this work
.
References
[1] J.C. Mol, Top. Catal. 27 (2004) 97-104.
[2] T.M. Trnka, R.H. Grubbs, Acc. Chem. Res. 34 (2001) 18-29.
[3] S.B. Garber, J.S. Kingsbury, B.L. Gray, A.H. Hoveyda,J. Am. Chem. Soc. 122
(2000)8168-8179.
[4] S. Gessler, S. Randl, S. Blechert, Tetrahedron Lett. 41 (2000) 9973-9976.
[5] B.Van Berlo, K. Houthoofd, B.F. Sels, P.A. Jacobs, Adv. Synth. Catal. 350 (2008)
1949-1953.
16

[6] H. Balcar, T. Shinde, N. Zilkova, Z. Bastl, Beilstein J. Org. Chem. 7 (2011) 22-28.
[7] T. Shinde, N. Zilkova, V. Hankova, H. Balcar, Catal. Today 179 (2012) 123- 129.
[8] J. Zelin, A.F. Trasarti, C.R. Apesteguía, Catal. Comm. 42 (2013) 84-88.
[9] A. Rybank, M.A.R. Meier, Green Chem. 9 (2007) 1356-1361.
[10] K.A. Burdett, L.D. Harris, P. Margl, B. R. Maughon, T. Mokhtar-Zadeh, P.C.
Saucier, E.P. Wasserman, Organometallics 23 (2004) 2027-2047.
[11] R.M. Thomas, B.K. Keitz, T.M. Champagne, R.H. Grubbs, J. Am. Chem. Soc. 133
(2011) 7490-7496.
[12] J. Patel, S. Mujcinovic, W. Roy Jackson, A.J. Robinson, A.K. Serelis, C. Such,
Green Chem. 8 (2006) 450-454.
[13] B. Matyska, A. Dosedlova, L. Petrusova, H. Balcar Collect. Czech. Chem.
Commun. 54 (1989) 455-461.
[14] M. Sibeijn, J.C. Mol,J. Mol. Catal. 76 (1992) 345-358.
[15] D. Mandelli, M. J. D. M. Jannini, R. Buffon, U. Schuchardt, J. Am. Oil Chem. Soc.
73(1996) 229-232.
[16] J. Gillespie, S. Herbig, R. Beyerinck, in: F.R. Hall, J.W. Barry (Eds.), Biorational
Pest Control Agents,ACS Symposium Series, Vol. 595, 1995,pp 208-212.
[17] D. Banasiak, J. Mol. Catal. 28, (1985) 107-115.
[18] J.C. Mol, J. Mol. Catal. 90 (1994) 185-199.
[19] J.C. Mol, Green Chem. 4 (2002) 5-13.
[20] G. Wilson, M. Caruso, N. Reimer, S.White, N. Sottos, J. Moore, Chem. Mater. 20
(2008) 3288-3297.
[21] S. Garber, J. Kingsbury, B. Gray, A. Hoveyda, J. Am. Chem. Soc. 122 (2000)
8168-8179.
[22] A. Keraani, C. Fischmeister, T. Renouard, M. Le Floch, A. Baudry, C. Bruneau, M.
17

Rabiller-Baudry, J. Mol. Catal. A Chem. 357 (2012) 73-80.
[23]W.J.van Rensburg, P. J. Steynberg, W.H. Meyer, M.M. Kirk, G.S. Forman,J. Am.
Chem. Soc. 126(2004) 14332-14333.
[24]H. Hong, A. Wenzel, T. Salguero, M. Day, R. Grubbs, J. Am. Chem. Soc. 129
(2007) 7961-7968.
18

19

Table 1:Cross-metathesis of methyl oleate with 1-hexene. Catalytic results on HG(3.36%)/SiO2
Reactant
ratio
Initial C6
Equilibrium
Conversiona
Yield a
Selectivitya
Carbon a
balance
concentration
conversion
ꢢꢣ
ꢂꢗ
Cꢀꢍꢐ
b
CB
X
ꢦꢀꢐ/ꢂꢗ
Xꢂꢗ
Xꢀꢐ
ηꢀꢁꢂ ηꢧꢁꢂꢗ ηꢧꢁꢀꢐ
Sꢀꢁꢂ Sꢧꢁꢂꢗ Sꢧꢁꢀꢐ
(% C)
(mol/L)
(%)
(%)
(%)
(%)
(%)
(%)
(%) (%)

1
2
3
4
5
0.029
0.058
0.087
0.016
0.145
67
75
84
88
91
67
75
84
88
91
66
61
56
50
40
46
55
69
78
83
21
20
15
10
8
23
22
20
22
19
59
73
82
89
91
41
27
18
11
9
34
37
39
44
48
94
96
95
97
95
6
7
0.174
0.203
96
97
92
93
34
28
86
87
6
6
17
15
93
93
7
7
50
54
95
99
T = 303 K; Cꢂꢍ ꢗ= 0.029 M, Wcat = 100 mg, cyclohexane (10 ml)
a At the end of catalytic runs
b Molar ratio
20

Captions to Schemes and Figures
Scheme 1:Cross-metathesis of methyl oleate with 1-hexene and self-metathesis of
methyl oleate and 1-hexene
Figure 1: Ru Hoveyda-Grubbs catalyst used in this work
Figure 2:Determination of the HG monolayeron SiO2 support
Figure 3:XRD diffractograms of the HG complex, SiO2 and HG/SiO2 samples
Figure 4:FTIR spectra of the samples in the 500-800 cm-1region.
Figure 5:DRIFT spectra of HG complex and HG/SiO2 samples (0.87, 6.0 and 11.6
%HG)
Figure 6:Self-metathesis of methyl oleate and 1-hexene onHG(0.87%)/SiO2 [T = 303
K,Cꢂꢍ ꢗ= 0.029M, Cꢀꢍꢐ= 0.029 M, Wcat = 30 mg, solvent: cyclohexane].
Figure 7: Cross-metathesis of methyl oleate with 1-hexene. (a) Catalyst: HG
(dissolved), 0.336 mg; (b) Catalyst: HG(1.12%)/SiO2, 30 mg [T = 303 K, Cꢂꢍ ꢗ= 0.029
M, RC6/MO = 1, RC6/HG= 540, solvent: cyclohexane]
Figure 8: Cross-metathesis of methyl oleate with 1-hexene: Effect of %HG [T = 303
K,Wcat = 100 mg, Cꢂꢍ ꢗ= 0.029 M, RC6/MO = 5, solvent: cyclohexane]
21

Figure 9:Dependence of MO conversion rate upon C6 concentration [T = 303 K,Wcat =
100 mg, Cꢂꢍ ꢗ= 0.029 M, solvent: cyclohexane]
Figure10:Evolution as a function of time ofMO and C6 conversions (XMO, XC6) and
yields to cross-metathesis (C-M), MO self-metathesis (S-MO) and C6 self-metathesis
(S-C6) products [catalyst: HG(3.36%)/SiO2, T = 303 K,Wcat = 100 mg,Cꢂꢍ ꢗ= 0.029 M,
RC6/MO = 1, solvent: cyclohexane].
Figure11: Effect of RC6/MO ratio on product distribution [catalyst: , T = 303 K,Cꢂꢍ ꢗ
=
0.029 molar, Wcat = 100 mg, solvent: cyclohexane]
Figure 12: Yields of terminal (9-DCE, 1-DC) and internal (5-TD, 9-TDE) olefins as a
function of RC6/MO ratio [T = 303 K; Cꢂꢍ ꢗ= 0.029 molar, Wcat = 100 mg, solvent:
cyclohexane]
Figure 13: MO/C6 cross-metathesis: Deactivation of HG(1.12%)/SiO2as a function of
RC6/MO [T = 303 K; Wcat =100 mg, Cꢂꢍ ꢗ= 0.029 molar, solvent: cyclohexane].
22

Scheme 1
C6 Self-metathesis
MO Self-metathesis
MO/C6 Cross-metathesis
23

Figure 1
CH3
H3C
N
N
Cl
H3C
CH3
Ru
O
CH3
H3C
Cl
24

Figure 2
18
16
14
12
10
8
Monolayer
6
4
2
0
0
5
10
15
20
25
-6
Moles of HG added (x10 )
25

Figure 3
HG(11.6%)/SiO
HG(6.0%)/SiO
2
)
(
2
HG(2.24%)/SiO
HG(0.87%)/SiO
2
2
SiO
2
HG
10
20
30
40
50

2
26

Figure 4
580
748
HG(11.6%)/SiO2
HG(6%)/SiO2
SiO2
HG
750
700
650
 (cm-1)
600
550
500
27

Figure 5
HG
HG(11.6%)/SiO2
HG(6%)/SiO2
HG(0.87%)/SiO2
3200
2800
1600
1200
(cm-1)
28

Figure 6
0.6
0.5
0.4
0.3
0.2
0.1
Self-metathesis of MO
Self-metathesis of C6
0.0
0
50
100
150
200
250
Time (min)
29