Remarkably Efficient Microwave-Assisted Cross-Metathesis of Lipids under Solvent-Free Conditions

Article abstract of DOI:10.1002/cssc.201601824

Catalytic transformation of renewable feedstocks into fine chemicals is in high demands and olefin metathesis is a sophisticated tool for biomass conversion. Nevertheless, the large-scale viability of such processes depends on the conversion efficiency, energy efficiency, catalytic activity, selective conversion into desired products, and environmental footprint of the process. Therefore, conversions of renewables by using simple, swift, and efficient methods are desirable. A microwave-assisted ethenolysis and alkenolysis (using 1,5-hexadiene) of canola oil and methyl esters derived from canola oil (COME) and waste/recycled cooking oil (WOME) was carried out by using ruthenium-based catalytic systems. A systematic study using 1st and 2nd generation Grubbs and Hoveyda–Grubbs catalysts was carried out. Among all ruthenium catalysts, 2nd generation Hoveyda–Grubbs catalyst was found to be highly active in the range of 0.002–0.1 mol % loading. The conversions proved to be rapid providing unprecedented turnover frequencies (TOFs). High TOFs were achieved for ethenolysis of COME (21 450 min^?1), direct ethenolysis of canola oil (19 110 min^?1), for WOME (15 840 min^?1) and for cross-metathesis of 1,5-hexadiene with COME (10 920 min^?1). The ethenolysis of commercial methyl oleate was also performed with a TOF of 8000 min^?1 under microwave conditions.

Full text of DOI:10.1002/cssc.201601824

Accepted Article
Title: Remarkably Efficient Microvawe-Assisted Cross-Metathesis of
Lipids in Solvent Free Conditions
Authors: Aman Ullah and Muhammad Arshad
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To be cited as: ChemSusChem 10.1002/cssc.201601824
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10.1002/cssc.201601824
ChemSusChem
Remarkably Efficient Microvawe-Assisted Cross-
Metathesis of Lipids in Solvent Free Conditions
Aman Ullah* and Muhammad Arshad
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton,
Canada, T6G 2P5
*Author to whom correspondence should be addressed. Tel. +1 780.492.4845, E-mail:
ullah2@ualberta.ca (Prof. Aman Ullah)
ABSTRACT
Catalytic transformation of renewable feed stocks into fine chemicals is in high demands and
olefin metathesis is one of the sophisticated tools for biomass conversion. Nevertheless, the large
scale viability of such processes depends on the conversion efficiency, energy efficiency,
catalytic activity, selective conversion into desired products and environmental footprint of the
process. Thus, conversions of renewables using simple, swift, and efficient methods are
desirable. A microwave-assisted ethenolysis and alkenolysis (using 1-5 hexadiene) of canola oil
1
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10.1002/cssc.201601824
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and methyl esters derived from canola oil (COME) and waste/recycled cooking oil (WOME) was
carried out using ruthenium based catalytic systems. A systematic study using 1st and 2nd
generation Grubbs (G1, G2) and Hoveyda-Grubbs (HG1 & HG2) catalysts was carried out.
Among all ruthenium catalysts, HG2 was found to be highly active in the range of 0.002-0.1
mol% loadings. The conversions proved to be highly efficient with outstanding values of
turnover numbers (TONs) and turnover frequencies (TOFs). The TONs and TOFs for ethenolysis
of COME (~1.5 million & 26,000), direct ethenolysis of canola oil (~0.6 million & 10,300), for
WOME (>1 million & 17,900) and for cross metathesis of 1,5-hexadiene with COME (1.6
million & 27,500) were achieved. The ethenolysis of commercial methyl oleate was also
performed leading to TONs ~1.2 million and TOFs 20,300 s-1 under microwave conditions.
INTRODUCTION
More than 90% of the raw materials for today’s chemical industry are fossil feedstocks in the
form of oil and gas.[1] Roughly one-tenth of the feedstock comes from renewable resources.[2]
Considering the dwindling fossil fuel resources and increasing importance of sustainability,
chemical industry and academia has focused interest on the development of fuels, chemicals and
materials from renewable resources.[3] Therefore, in order to achieve more sustainable economy,
the transition from petrorefinery to biorefinery is required.[4] Particularly transformation of
vegetable oils, due to their low cost, biodegradability and large scale availability, has received
renewed attention.[5] In 2012-2013, the world supply and distribution of major oil seeds was 462
million metric tons including palm, canola, sunflower and soy bean respectively.[6] In addition to
large scale availability, a wide range of products can be obtained from seed oils which make
them cost-effective and environment friendly alternative.[3b, 7] These attributes make oils a good
fit for a biorefinery which mimics a traditional petrochemical paradigm.[8]
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Figure 1. The Grubbs (G) and Hoveyda-Grubbs (HG) first and second generation (1 & 2)
catalysts used for ethenolysis and alkenolysis.
For chemical conversion and formation of new carbon–carbon double bonds, olefin metathesis is
considered one of the most versatile and powerful synthetic transformation tools and has been
used in both pure and applied chemistry.[9] The transformative progress in pure and applied
chemistry through metathesis was recognized in 2005 with the award of the Nobel Prize in
Chemistry.[10] Generally olefin metathesis can be classified into ring-opening, ring closing and
cross-metathesis.[11] Metal-catalyzed olefin cross-metathesis has become a standard synthetic
method with numerous industrial uses, including the well-known Shell Higher Olefin Process
(SHOP).[12] Olefin cross-metathesis is a catalytic reaction between two alkene molecules that
results in redistribution of alkylidene groups.[13] The cross-metathesis of an olefinic compound
with ethylene is called ethenolysis and a cross-metathesis with an olefin other than ethylene is
called alkenolysis.[6, 14] Various efforts have been made on the conversion of plant oil derived
fatty acids into products using ethenolysis chemistry.[14-15] The production of olefins through
ethenolysis, the cross metathesis (CM), has been target of many investigations because this
process produces high value linear α-olefins which are direct antecedents to various applications
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including monomers for polymer synthesis, cosmetic ingredients, lubricants, detergents, soaps,
perfumes, antimicrobial agents and renewable fuels.[16] The ethenolysis as well as alkenolysis of
seed-oil derivatives and purified methyl oleate as a model substrate has been investigated.[16b, 17]
However, generally reactions are carried out in organic solvents and a high catalyst loading is
required for effective conversion particularly the ethenolysis.[17a, 17b, 17d, 18] The catalyst turnover
numbers (TONs) greater than 50,000 are required for this process to be viable on larger scale.[17e,
19]
Most of the studies reported to date have used purified methyl oleate as a model substrate for
metathesis. Although high TONs have been reported on the alkenolysis of methyl oleate (MO)
and FAMEs using other olefins as ethylene surrogates and proved to be commercially viable
leading to large scale manufacturing facility.[6, 20] For example, the TONs as high as 192,900 and
470,000 for CM of methyl oleate with propylene and 2-butene have been achieved.[17e, 21]
Nevertheless, the metathesis with higher olefins results in the production of substantial amount
of internal olefins which are considered low value products compared to α-olefins produced
through ethenolysis.[16b] Therefore, recent investigations have been focused on the conversion of
methyl oleate into high value terminal products using ethylene in the presence of different
catalysts in organic solvents.[17a, 18b, 22] More recently, the ethenolysis TONs as high as 340,000
have been achieved using newly synthesized cyclic alkyl amino carbene (CAAC)
complexes[16b]and ethenolysis using efficient molybdenum and tungsten based catalysts have
been reported.[23] Despite the substantial improvements in the metathesis, the solvent free rapid
conversion of plant oils into desired terminal olefins is undoubtedly an important concept for
efficient conversions of plant oil feedstocks into multiple downstream products.
4
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Scheme 1. Products of ethenolysis (A); alkenolysis (B) of canola oil methyl esters (COME)
waste cooking oil methyl esters (WOME) and direct ethenolysis of canola oil (C) under
microwave conditions
Microwaves are considered as green, rapid and environment friendly due to low energy
consumption[24] and lead to enhanced rates, yields, and purities in comparison to reactions
conducted with conventional heating.[25] There has been great success in the field of microwave-
assisted organic synthesis, polymer chemistry, material sciences, nanotechnology, and
biochemical processes.[26] Despite few reports on metathesis particularly ring-closing metathesis
of small molecules,[26a, 26b, 27] to the best of our knowledge, the microwave-assisted metathesis
particularly ethenolysis of natural oils has not been investigated.
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Herein, we report the ethenolysis and alkenolysis of canola oil, methyl esters of canola oil
(COME) and waste/recycled cooking oil (WOME) using ruthenium metathesis catalysts (Figure
1) under microwave irradiation conditions.
RESULTS AND DISCUSSION:
Olefin metathesis (OM) is very popular and useful reaction in chemical synthesis. Recently, use
of OM for the conversion of oleochemicals into valuable products has triggered an explosive
growth of interest due to introduction of the well-defined, functional-group tolerant ruthenium
alkylidene complexes developed by Grubbs and coworkers.[28] Although these catalysts can be
handled in air and react selectively with olefins in the presence of various functional groups.[10a,
29] The efficiency of an olefin metathesis catalyst is determined by the rate of metathesis over the
rate of the catalyst decomposition.[30] The effects of temperature and solvents on catalyst
efficiency and decomposition have been investigated.[31] The catalyst decomposition during
extended reaction times and temperatures significantly affect TONs and product selectivity.[30]
The selectivity of ruthenium complexes for the production of α-olefins has been reported as
poor.[17a] With an aim of rapid conversion of canola oil and mixture of methyl esters COME and
WOME into linear α-olefins under solvent free metathesis conditions, we investigated the
microwave-assisted ethenolysis and alkenolysis using ethylene and a diolefin (1,5-hexadiene).
The reaction conditions including temperature, time, catalysts screening and their concentrations
were optimized. For oils and FAMEs complicated product mixtures are produced therefore
TONs were calculated based on Me9DA (TONMe9DA), a method particularly used for oils and
FAMEs.[17e]
Catalyst Screening and Ethenolysis of COME
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For ethenolysis reactions of COME, initially a group of four different ruthenium based catalysts
G1, G2, HG1 and HG2 (Figure 1) was screened to assess their suitability under microwave
irradiations at a temperature of 50°C for a time span of 8 minutes (3 minutes ramping time + 5
minutes hold time). The initial reactions were performed with catalyst loading of 0.1 mol%. As
can be seen from table 1, the second generation catalysts (G2 & HG2) displayed better
transformation of reactants into metathesis products giving higher conversion rates (96%) (table
1, entry 2 and 10) as compared to first generation catalysts (G1 & HG1) having conversion rates
of 65% and 64% respectively with slightly higher GC% yield and TONs (table 1, entry 1 and 3).
Considering higher conversion rates of second generation catalysts, the G2 & HG2 were further
investigated using lower catalyst loading (0.05 mol%) and shorter reaction times of 3.5 minutes
(3 minutes of ramping time + thirty seconds hold time). Despite 50% decrease in catalyst
loadings of G2 & HG2, the conversion rates did not change significantly (95% and 96%
respectively). However, the decrease in yield for catalyst G2 was observed (table 1, entry 4).
Contrary to catalyst G2, the catalyst HG2 displayed higher yield and improved TONs (318,300)
and TOFs (table 1 and S1 entry 5). So, during the initial screening of four catalysts, HG2 was
found to be the most promising catalyst under solvent free microwave conditions. HG2 catalyst
was further studied at different temperatures (40, 50, 60 and 80°C) and with lower catalyst
loadings to obtain best yield, TONs and TOFs. An efficient conversion (96%) was still reached
at all temperatures with 0.1 mol% of HG2 catalyst loading. A reaction temperature of 40°C
provided less yield and TONs (table 1, entry 9), impeding the catalyst utility. While the
ethenolysis at a temperature of 50°C was found to be most appropriate as compared to reactions
conducted at 60°C and 80°C for the conversion of substrates into metathesis products (table 1).
The reactions at increased temperature probably induced the early decomposition of catalyst,
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which may account for reduced TONs. These investigations indicate that the solvent free
microwave-assisted metathesis reactions at lower or higher temperature than 50°C are of
minimal benefits in terms of yield and TONs. Therefore the temperature of 50°C was found to be
the most appropriate or optimal for metathesis reactions to get effective conversions.
Further ethenolysis reactions of COME were performed with lower concentration of HG2
catalyst. Lowering the catalyst loading of HG2 from 0.05 to 0.01 mol% resulted in a substantial
increase in TONs (~1.5 million), TOFs (26,000 s-1) (table 1 and S1 entry 6). By decreasing
catalyst loading to 0.005 mol% (table 1, entry 7), it is worth noting that HG2 still maintained
higher conversion rate (95%), with slightly lower yield, TONs (~1.1 million) and TOFs (19400
s-1) values. A significant decrease in conversion rate, TONs and TOFs was observed by lowering
the concentration of HG2 to 0.002 mol% (table 1 and S1 entry 8) suggesting that further
decrease in catalyst is not useful. The possible terminal and internal olefins obtained after
catalytic transformation of COME with ethylene are shown in scheme 1, and were characterized
by GCMS analysis (figure 2). A fraction of volatile components was also collected after reaction
completion and identified by GCMS (figure S1). For complete identification of all liquid
components, the reaction mixture was subjected to silica gel column chromatography and
obtained ethenolyzed hydrocarbons fraction (figure S2) and ethenolyzed methyl esters fraction
(figure S3) were characterize by GCMS. The separated pure diester 6 (figure S6) was
characterized by proton NMR.
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Table 1. Ethenolysis of renewable canola methyl esters derived from canola oil.
Loading
[mol%]
Temperature Hold time
Conv.
[%]
GC% yield
Entry
Catalyst
TONMe9DA
[°C]
50
50
50
50
50
50
50
50
40
50
60
80
[min.]
of Me9DA
22.8
24.4
34.7
7.7
1
2
G1
0.1
0.1
5
5
65
96
64
95
96
96
95
69
96
96
96
96
126,500
130,900
263,500
82,500
G2
3
HG1
G2
0.1
5
4
0.05
0.05
0.01
0.005
0.002
0.1
0.5
0.5
1
5
HG2
HG2
HG2
HG2
HG2
HG2
HG2
HG2
21.8
21.3
16
318,300
1,561,500
1,165,600
573,300
136,200
165,000
150,100
171,700
6
7
1
8
1
9.4
9
3
18.7
22.7
20.6
23.6
10
11
12
0.1
1
0.1
1
0.1
1
Although increased TONs from ~0.16 million to ~1.5 million without decrease in conversion rate
was achieved by lowering the catalyst loading from 0.1 mol% to 0.002 mol%, but yield gradually
decreased as depicted in table 1. It has also been observed that decrease in reaction times under
microwave irradiation resulted in unprecedented TOFs 26,000 s-1 (table S1, entry 6).
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2.0x108
1.8x108
1.6x108
1.4x108
1.2x108
1.0x108
8.0x107
6.0x107
4.0x107
2.0x107
0.0
1
C18:1C
COME
Ethenolysis products
2
7
16
C16:0
8
15
C18:1t
6
C18:2
C16:0
C18:3
15
20
25
30
35
40
45
50
55
60
65
70
75
Retention time (min)
Figure 2. GCMS spectrum of canola oil methyl esters (COME) and ethenolysis products
Investigation on Ethenolysis of WOME
Ethenolysis of WOME was carried out using conditions already optimized for ethenolysis of
COME but using different concentrations of HG2 (table 2). The conversion of 96% was
observed using different catalyst loadings from 0.1 mol% to 0.005 mol%. With 0.1 mol% of
catalyst loading ~0.1 million TONs and 1790 s-1 TOFs were achieved. Decreasing the catalyst
contents to 0.005 mol% still provided TONs (~1.0 million) and TOFs (17,900 s-1) as shown in
table 2 and S2, entry 3. The product components obtained after ethenolysis of WOME were
characterized by GC analysis (figure 3) and found to be similar to those described for the
ethenolysis of COME (scheme 1).
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Table 2. Ethenolysis of methyl fatty esters (WOME) derived from waste cooking oil.
Loading
[mol%]
Temperature Hold time
Conv.
[%]
GC% yield
of Me9DA
Entry
Catalyst
HG2
TONMe9DA
107,500
[°C]
[min.]
1
2
3
0.1
0.05
0.005
50
1
96
96
96
14.7
HG2
50
50
1
1
14.0
14.7
205,200
HG2
1,078,100
2.0x108
C18:1C
1.8x108
1.6x108
1.4x108
1.2x108
1.0x108
8.0x107
6.0x107
4.0x107
2.0x107
0.0
1
WOME
ethenolysis product
2
C16:0 C18:1t
7
C15:1
8
6
C16:0
C18:2
C14:0
C18:0
C18:3
15 20 25 30 35 40 45 50 55 60 65 70 75
Retention time (min)
Figure 3. GCMS spectrum of waste cooking oil methyl esters (WOME) and its metathesis
products with ethylene
Study on Metathesis of COME with 1,5-Hexadiene
Alkenolysis, the cross metathesis reactions of longer chain internal and terminal olefins other
than ethylene, have been investigated using propene, butene and octene with purified methyl
oleate and FAMEs of different plant oils and higher TONs compared to ethenolysis have been
reported.[17e, 19, 21, 31c] Despite higher TONs, alkenolysis with higher olefins results in significant
amounts of undesired internal olefins.[16b] The cross-metathesis with diolefin such as 1,5-
hexadiene should result in terminal metathesis products due to the presence of both terminal
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double bonds (figure 4). There are no reports in literature on the use of 1,5-hexadiene therefore
alkenolysis of canola methyl esters with 1,5-hexadine was also performed using microwave
radiations. Similar to ethenolysis, four catalysts G1, G2, HG1 and HG2 were screened with 0.1
mol% catalyst loadings at 50°C temperature. No reaction products were observed with 0.1 mol%
of first generation catalysts (G1 & HG1) for 8 minutes reaction time under microwave
conditions. Surprisingly, second generation catalysts (G2 & HG2) gave the highest conversion
rate of 99% within ~ 8 minutes (~3 minutes of ramping time + 5 minutes hold time) with
effective TONs of 84,100 and 133,800 respectively (table 4, entry 2 and 4). Both these catalysts
were further studied at lower loading of 0.05 mol% for a reaction time of ~3.5 min (~ 3 min
ramping time + 30 seconds hold time). Using catalyst G2, a sharp decrease in conversion rate
and yield while slight increase in TONs was observed (table 3, entry 5). However, with HG2, the
conversion rate was maintained at 99% with slightly lower yield and improved TONs as well as
TOFs (table 3 and S3, entry 6). These results also suggest HG2 as most effective catalyst for
alkenolysis of fatty esters under microwave conditions.
The alkenolysis reactions were also carried out at 45°C, 60°C and 80°C using 0.1 mol% of HG2
catalyst. At 45°C and 80°C, a good yield and TONs were obtained, but conversion rate was
decreased to 82% and 93% respectively (table 1, entry 8 and 10). These results suggested 50°C
as an optimal temperature for alkenolysis reactions.
Further alkenolysis reactions were carried out at 50°C at lower concentration of HG2 catalyst.
Decreasing the catalyst loading to 0.01 mol% still provided highest conversion rate and a
remarkable increase in TONs (~1.6 million) and TOFs (27,500 s-1) values (table 3 and S3, entry
7). Further lowering of catalyst below 0.01 mol% resulted in very low conversions for
alkenolysis reactions.
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Table 3. Cross metathesis of renewable FAME's derived from canola oil with 1,5-
hexadiene.
Loading
[mol%]
Temperature Hold time
Conv.
[%]
GC% yield
of Me9DA
Entry
Catalyst
TONMe9DA
[°C]
50
50
50
50
50
50
50
45
60
80
[min.]
1
2
G1
0.1
0.1
5
5
0
0
0
G2
99
0
15.6
0
84,100
0
3
HG1
HG2
G2
0.1
5
4
0.1
5
99
27
99
98
82
99
93
18.4
9.7
133,800
104,100
234,700
1,655,400
189,100
83,600
196,400
5
0.05
0.05
0.01
0.1
0.5
0.5
1
6
HG2
HG2
HG2
HG2
HG2
16.1
22.6
26.0
11.5
27.0
7
8
5
9
0.1
1
10
0.1
1
1.8x108
1.6x108
1.4x108
1.2x108
1.0x108
8.0x107
6.0x107
4.0x107
2.0x107
0.0
C18:1C
1
COME
Metathesis products
2
16
14
8
C16:0
15
C18:1t
7
6
11
12
C18:2
C16:0
C18:3
15
20
25
30
35
40
45
50
55
60
65
70
75
Retention time (min)
Figure 4. GCMS spectrum of COME and alkenolysis products
Direct Ethenolysis of Canola Oil
Direct ethenolysis of canola oil was also studied under similar conditions as described above for
ethenolysis of COME. More than 94% conversions were obtained (table 4) with two different
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loadings of HG2 catalyst (0.05 mol%, and 0.01 mol%). Anomalous behavior can be seen in table
4, despite higher conversion rate, due to substantial transformation of cis-oleate (C18:1 C, figure
5) to trans-oleate (C18:1 t) lower yield was obtained. A notable increase in TONs (form 48,400
to 618,700) and TOFs (from 800 to 10,300 s-1) were observed when catalyst was decreased from
0.05 mol% to 0.01 mol% (table 4 and S4). The raw product mixture obtained after ethenolysis
(Scheme 1C) was transesterified with methanol prior to its characterization with GCMS (figure
5). The products obtained were similar to those obtained for ethenolysis of COME.
Table 4. Ethenolysis of canola oil (TAG's).
Loading
[mol%]
Temperature Hold time
Conv.
[%]
GC% yield
of Me9DA
Entry
Catalyst
HG2
TONMe9DA
48,400
[°C]
[min.]
1
2
0.05
0.01
50
1
95
94
1.1
5.7
HG2
50
1
618,700
1.6x108
1.4x108
1.2x108
1.0x108
8.0x107
6.0x107
4.0x107
2.0x107
0.0
1
7
C18:1t
Canola Oil
Ethenolysis products
2
C16:0
8
6
16
15
C18:0
C18:1C
C17:0 (standard)
C18:2
C16:0
C18:0
C18:3
15 20 25 30 35 40 45 50 55 60 65 70 75
Retention time (min)
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Figure 5. GCMS spectrum of canola oil and its ethenolyzed products after transesterification
with methanol.
Methyl Oleate Ethenolysis
An extensive work has been reported on ethenolysis of methyl oleate[15a, 18b, 32]. To compare the
ethenolysis results of renewable fatty esters, ethenolysis of methyl oleate was performed using
similar conditions as described for canola oil methyl esters. Cross metathesis of methyl oleate
with ethylene results in the formation of two cross products, methyl 9-decenoate (1) and 1-
decene (2) and two self-products dimethyl 9-octadecene-1,18-dioate (6) and 9-octadecene (7) as
presented in scheme 1. Ethenolysis of methyl oleate was conducted using HG2 catalyst with two
different concentrations of 0.005 and 0.01 mol% providing almost 94% conversion in all cases
(table 5). The highest value of TONs (~1.2 million) were obtained with 0.01 mol% loading of
catalyst (table 5, entry 3), whereas decreasing catalyst loading to 0.005 mol%, a substantial
decrease in yield and TONs were observed (table 5, entry 2). The less yield and TONs even with
higher conversion rate in case of 0.005 mol% loading of catalyst are due to formation of trans
methyl oleate during the reaction. A good number of TOFs values were also observed in
ethenolysis of methyl oleate (table S5) providing the highest TOFs value of 20,300 s-1 with
catalyst loading of 0.01 mol% (table S5, entry 3).
From the results (table 5), it can be seen that ethenolysis of methyl oleate displayed less
conversion rate, yield and TONs compared to ethenolysis of COME. With catalyst loading of
0.01 mol%, the observed ethenolysis TONs (1.2 million) for methyl oleate (table 5, entry 3) were
found to be 20% less than the TONs (1.5 million) obtained after ethenolysis of COME (table 1,
entry 6). During ethenolysis of methyl oleate, lowering the catalyst loading to 0.005 mol%
resulted in a significant decrease in TONs to 0.79 million (table 5, entry 2), while ethenolysis of
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COME still displayed an efficient value of 1.16 million, (table 1, entry 7). The less conversions
rate, yield and TONs in case of methyl oleate ethenolysis can be attributed to less purity of
methyl oleate (commercial MO without purification was used) which affects the efficiency of
reaction[33]
.
Table 5. Ethenolysis of methyl oleate.
Loading
[mol%]
Temperature Hold time
[a]Conv.
[%]
GC% yield
of Me9DA
Entry
Catalyst
HG2
TONMe9DA
372,300
[°C]
[min.]
1
2
0.005
0.005
50
1
94
94
3.9
8.3
HG2
50
1
794,200
3
4
HG2
HG2
0.01
0.01
50
50
1
1
94
92
12.8
10.2
1,222,800
972,300
Conclusion
Use of microwave electromagnetic radiations for the CM of fatty esters of vegetable oils with
ethylene and 1,5-hexadiene brought a dramatic increase in the conversion rates, TONs and TOFs
in a very short reaction time under solvent free conditions and low catalysts loadings.
Ethenolysis of WOME also provided promising results. Among four catalysts, HG2 was found
to be most promising catalyst at 50°C generally providing efficient conversions and TONs
during ethenolysis and alkenolysis reactions. Unprecedentedly, more than 1.5 million TONs and
up to 26,000 s-1 TOFs for ethenolysis of COME, around ~0.6 million TONs and 10,300 s-1 TOFs
for direct ethenolysis of canola oil, above one million TONs and 17900 s-1 TOFs for ethenolysis
of WOME, more than 1.6 million TONs and above 27,500 s-1 TOFs for the cross metathesis of
1,5-hexadiene with COME were achieved. Ethenolysis of methyl oleate was also performed for
comparison with COME and WOME. The highest value of TONs ~1.2 million and TOFs 20,300
s-1 were also attained for the ethenolysis of methyl oleate. These results demonstrate that
microwave-assisted conversion of renewable oils and their fatty acid derivatives could be an
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appropriate and rapid process for the production of various starting materials for the chemical
industry.
EXPERIMENTAL
General Considerations
All of the reactions were performed on a CEM-Discover (120 V, Matthews, USA), a source of
microwave irradiation in 10 mL sealed tube, while infrared mode was used to measure the
temperature of the reaction contents. To identify the components, GC-MS analyses of all
samples were conducted on Agilent 6890N (USA) gas chromatograph, fitted with a fused silica
capillary column SP2560 (100m × 0.25mm × 0.2 μm film thickness) and detector 5975B inert
XL MSD. The sample volume of 2 μL was injected, the injector temperature was set to 240 °C
and a split mode with ratio of 20:1 was used. The initial temperature of oven was set to 45 °C
and held for 4 minutes. The temperature was then increased to 175 °C with a ramp rate of 13 °C
min-1; held for 27 minutes and further ramped at 4 °C min-1 to 215 °C and held for 35 minutes.
The mass scanning range of 30-1000 amu at 1.55 scan per second was performed. Helium gas
was used as a mobile phase with a constant flow rate of 1.3 mL/min.
They hydrocarbon fractions were characterized on Agilent 7980A (USA) instrument using HP5
column (30m × 0.32mm × 0.25 μm film thickness), coupled with inert EI MSD with triple axis
detector (5975C, Agilent, USA). The injection volume of 1 μL was used with injector
temperature of 250 °C in a splitless mode. The oven initial temperature of 50 °C was set and held
for two minutes. The temperature was increased at a ramp rate of 5°C min-1 to 325 °C and then
held for five minutes. The MS scanning range of 50-600 amu was applied with a scan rate of
2.66 per second. A constant flow rate of 4.4 mL/min of helium gas was used as mobile phase.
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While Perkin Elmer GC-FID Clarus 500 instrument (USA) equipped with flame ionization
detector was used for quantitative analysis to measure the conversion rate, selectivity and yield
of all samples. The temperature was set at 280 °C for detector, while 240 °C for injector. The air
and hydrogen gases were used as a carrier with the flow rate of 450 and 45 mL/min respectively.
The column used and all other conditions were same as mentioned above for GC-MS instrument
Agilent 6890N.
1H NMR spectra of selected samples were recorded after dissolving in deuterated chloroform at
400 MHz frequency on a Varian INOVA instrument at a temperature of 27 °C.
The conversion rates of all metathesis reaction were calculated using formula given below;
Conversions = 100 -[(final moles of reactants)100/(initial moles of reactants),
The turnover numbers (TONs) and turnover frequencies (TOFs) in all cases were calculated on
methyl-9-deceneoate (Me9DA) bases reported below
TONMe9DA (turnover numbers based on Me9DA) = 10,000 × (GC% yield of Me9DA)/(catalyst
loading in mol ppm)
TOFMe9DA = TONs / time (sec.).
Materials
Canola oil, methyl oleate (99%), Grubbs catalyst 1st generation (G1, 97%), Grubbs catalyst 2nd
generation (G2), Hoveyda- Grubbs catalyst 1st generation (HG1), Hoveyda- Grubbs catalyst 2nd
generation (HG2, 97%), 1,5-hexadiene (97%), ethyl vinyl ether (≥98%), potassium hydroxide
(≥85%), sodium chloride (≥99.5%), anhydrous sodium sulphate (≥99%), methanol (≥99.8%) and
acetone (≥99.9%) were obtained from sigma Aldrich. The ethylene gas (Mathesons, polymer
grade, CAS: 74-85-1), silica gel used for column chromatography (70-230 mesh, 60 Å), flash
silica (Silicycle, 40-63 μm, 230-400 mesh), thin layer aluminium chromatographic plates
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(Macherey-Nagel, 0.20 mm thick, 20 × 20 cm size, UV254), ethyl acetate (fisher, 99.9%), n-
hexane (Caledon) were purchased and used as such.
Methanolic Transesterification of Canola Oil and Waste Cooking Oil
Methanolic transesterification of canola oil and waste cooking oil into their fatty esters was
performed using KOH as a base according to the previously reported method. [34]
Separation of Saturated Esters by Crystallization Method
For best results in metathesis reactions, saturated esters were removed from transesterified
canola methyl esters (COME) and waste cooking oil methyl esters (WOME) by crystallization
method. For their separation, these esters were dissolved in acetone and kept overnight at a
temperature of -5°C. The volume of acetone used was equal to the volume of esters. The
saturated esters get solidified at this lower temperature and were separated by filtration carried
out at same temperature. This process was repeated three times to remove maximum amount of
saturated esters. The obtained esters which were mostly unsaturated were dried and passed
through a column of flash silica before proceeding for metathesis reactions.
General Procedure for Ethenolysis of Methyl Fatty Esters
Specific amount of methyl fatty esters were charged in a 10 mL glass vial having teflon coated
stirring bar and was purged with nitrogen gas for five minutes. An appropriate amount of catalyst
(table 1) was weighed in a glove box under an atmosphere of nitrogen and was added into the
reaction vial. The reaction vial was sealed and brought to the ethylene line. The reaction vessel
was purged with ethylene gas for five minutes and then ethylene was liquefied into the reaction
vial to a volume of about 0.5 mL by cooling the vial in liquid nitrogen. The reactions were
conducted in sealed reaction vessels at specified temperatures. The power is usually adapted by
the instrument to reach and maintain the set temperature. The reactions in duplicate and in some
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10.1002/cssc.201601824
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cases in triplicate runs were carried out. The pressure variation during ethenolysis was between
5.5 bar to 8.3 bar, with an average pressure of 6.9 bar. The set maximum power for the
instrument was 250 W. The reaction was run for specific time interval at a suitable temperature
to get maximum conversions of reactants into product components. The ramp time to attain the
required temperature was ~ 3 minutes. After reaction completion, ethyl vinyl ether (0.5 mL) was
added into the reaction mixture to deactivate the catalyst and was passed through a plug of flash
silica to remove the catalyst. The product components were characterized by GCMS and
quantified with GC-FID by considering naturally occurring methyl palmitate (C16:0) in the
canola oil and/or methyl heptadecanoate (C17:0) as an internal standard.
Ethenolysis of Canola Oil
Canola oil was first passed through a column of flash silica and anhydrous magnesium sulphate
to remove colored pigments and moisture contents. Afterwards, it was proceeded for cross
metathesis reactions with ethylene in the presence of catalyst HG2 using identical conditions
and/or methodology as mentioned for ethenolysis of methyl fatty esters. The obtained metathesis
products were transesterified with methanol prior to GC analysis used for characterization and
quantification of product components.
Separation of Components after ethenolysis of COME
A volatile fraction was collected right after the completion of ethenolysis reaction containing
1,4-petadiene (4) and 1-butene (5) and was characterized by GCMS (figure S1). The remaining
mixture of ethenolyzed components were separated into three major fractions; ethenolyzed
hydrocarbons fraction (EHF), ethenolyzed methyl esters fraction (EMEF) and pure dimethyl
octadec-9-enedioate (6) with the help of silica gel column chromatography using an eluent
system of 1-5% ethyl acetate in hexane. These fractions were further characterized by GCMS
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(figure S2 and S3). The hydrocarbon and methyl esters fractions were subjected to distillation
1
separately to purify some of the major components. H NMR of those purified components is
provided in the supporting information (figures S4, S5 and S6).
Cross Metathesis of Canola Oil Methyl Esters with 1,5-Hexadiene
In a glove box under an inert atmosphere, an appropriate amount of catalyst (table. 4) was
weighed and added into the reaction vial containing purified canola methyl esters (1 Eq.)
degassed with nitrogen and equipped with a stirring bar. The reaction vessel was sealed and
purged with nitrogen gas for five minutes followed by the addition of 1,5-hexadiene (2 Eq.) with
the help of purged glass syringe. The sealed reaction vessel was placed in a microwave reactor
under similar reaction conditions as described above for ethenolysis of methyl fatty esters. After
reaction completion, ethyl vinyl ether (0.5 mL) was added into the reaction mixture to deactivate
the catalyst and was passed through a plug of flash silica to remove the catalyst contents. The
product components were characterized by GCMS and quantified with GC-FID by considering
naturally occurring methyl palmitate (C16:0) in the canola oil and methyl heptadecanoate
(C17:0) as an internal standard.
Acknowledgements Authors gratefully acknowledge the financial support for current work by
The Alberta Innovates Bio Solutions (AI Bio).
Supporting Information
The GCMS plots for the volatile components, ethenolyzed hydrocarbons fraction (EHF),
ethenolyzed methyl esters fraction (EMEF), TOF's table of all metathesis reactions and proton
NMR spectra of purified components 1, 6 and 7 are provided.
References:
[1]
S. Mecking, Angew. Chem. Int. Ed. 2004, 43, 1078-1085.
21
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10.1002/cssc.201601824
ChemSusChem
[2]
[3]
a) D. R. Dodds, R. A. Gross, Science 2007, 318, 1250-1251; b) S. Chikkali, S. Mecking, Angew.
Chem. Int. Ed. 2012, 51, 5802-5808.
a) P. T. Anastas, M. M. Kirchhoff, Acc. Chem. Res. 2002, 35, 686-694; b) A. Corma, S. Iborra, A.
Velty, Chem. Rev. 2007, 107, 2411-2502; c) P. N. R. Vennestrom, C. M. Osmundsen, C. H.
Christensen, E. Taarning, Angew. Chem. Int. Ed. 2011, 50, 10502-10509.
B. Kamm, M. Kamm, P. R. Gruber, S. Kromus, in Biorefineries - industrial processes and products :
status quo and future directions, Wiley-VCH Verlag GmbH, 2008, pp. 1-40.
B. Ö. Öztürk, B. Topoğlu, S. Karabulut Şehitoğlu, Eur. J. Lipid Sci. Tech. 2015, 117, 200-208.
A. Nickel, R. L. Pederson, in Olefin Metathesis: Theory and Practice (Ed.: K. Grela), John Wiley &
Sons, Inc., 2014, pp. 335-348.
[4]
[5]
[6]
[7]
a) M. A. R. Meier, J. O. Metzger, U. S. Schubert, Chem. Soc. Rev. 2007, 36, 1788-1802; b) A. S.
Carlsson, J. L. Yilmaz, A. G. Green, S. Stymne, P. Hofvander, Eur. J. Lipid Sci. Tech. 2011, 113, 812-
831; c) U. Biermann, W. Friedt, S. Lang, W. Lühs, G. Machmüller, J. O. Metzger, M. Rüsch gen.
Klaas, H. J. Schäfer, M. P. Schneider, Angew. Chem. Int. Ed. 2000, 39, 2206-2224.
P. A. Schieb, Biorefinery 2030 : future prospects for the bioeconomy, Springer Berlin Heidelberg,
2015.
a) Y. Takahira, Y. Morizawa, J. Am. Chem. Soc. 2015, 137, 7031-7034; b) R. H. Grubbs, A. G.
Wenzel, D. J. O'Leary, E. Khosravi, Handbook of metathesis, Vol. 2, Second edition. ed., Wiley-
VCH: Weinheim, 2015. .
[8]
[9]
[10]
[11]
a) R. H. Grubbs, Angew. Chem. Int. Ed. 2006, 45, 3760-3765; b) Y. Chauvin, Angew. Chem. Int. Ed.
2006, 45, 3740-3747; c) R. R. Schrock, Angew. Chem. Int. Ed. 2006, 45, 3748-3759.
a) S. Basra, S. Blechert, in Strategies and Tactics in Organic Synthesis, Vol. 4 (Ed.: H. Michael),
Academic Press, 2004, pp. 315-346; b) A. H. Hoveyda, A. R. Zhugralin, Nature 2007, 450, 243-
251.
[12]
a) E. F. Lutz, J. Chem. Educ. 1986, 63, 202; b) W. Keim, Angew. Chem. Int. Ed. 2013, 52, 12492-
12496; c) S. J. Connon, S. Blechert, Angew. Chem. Int. Ed. 2003, 42, 1900-1923.
N. Calderon, Acc. Chem. Res. 1972, 5, 127-132.
[13]
[14]
[15]
J. C. Mol, Green Chem. 2002, 4, 5-13.
a) K. A. Burdett, L. D. Harris, P. Margl, B. R. Maughon, T. Mokhtar-Zadeh, P. C. Saucier, E. P.
Wasserman, Organometallics 2004, 23, 2027-2047; b) J. Julis, S. A. Bartlett, S. Baader, N.
Beresford, E. J. Routledge, C. S. J. Cazin, D. J. Cole-Hamilton, Green Chem. 2014, 16, 2846-2856.
a) M. B. Herbert, V. M. Marx, R. L. Pederson, R. H. Grubbs, Angew. Chem. Int. Ed. 2013, 52, 310-
314; b) V. M. Marx, A. H. Sullivan, M. Melaimi, S. C. Virgil, B. K. Keitz, D. S. Weinberger, G.
Bertrand, R. H. Grubbs, Angew. Chem. Int. Ed. 2015, 54, 1919-1923; c) R. W. Jenkins, L. A.
Sargeant, F. M. Whiffin, F. Santomauro, D. Kaloudis, P. Mozzanega, C. D. Bannister, S. Baena, C.
J. Chuck, ACS Sustain. Chem. Eng. 2015, 3, 1526-1535; d) L. Montero de Espinosa, M. A. R. Meier,
Eur. Polym. J. 2011, 47, 837-852.
[16]
[17]
a) R. M. Thomas, B. K. Keitz, T. M. Champagne, R. H. Grubbs, J. Am. Chem. Soc. 2011, 133, 7490-
7496; b) S. C. Marinescu, R. R. Schrock, P. Müller, A. H. Hoveyda, J. Am. Chem. Soc. 2009, 131,
10840-10841; c) J. Patel, J. Elaridi, W. R. Jackson, A. J. Robinson, A. K. Serelis, C. Such, Chem.
Commun. 2005, 5546-5547; d) F. van der Klis, J. Le Nôtre, R. Blaauw, J. van Haveren, D. S. van Es,
Eur. J. Lipid Sci. Tech. 2012, 114, 911-918; e) A. Nickel, T. Ung, G. Mkrtumyan, J. Uy, C. W. Lee, D.
Stoianova, J. Papazian, W.-H. Wei, A. Mallari, Y. Schrodi, R. L. Pederson, Top. Catal. 2012, 55,
518-523.
[18]
a) J. Zhang, S. Song, X. Wang, J. Jiao, M. Shi, Chem. Commun. 2013, 49, 9491-9493; b) D. R.
Anderson, T. Ung, G. Mkrtumyan, G. Bertrand, R. H. Grubbs, Y. Schrodi, Organometallics 2008,
27, 563-566.
22
This article is protected by copyright. All rights reserved.

10.1002/cssc.201601824
ChemSusChem
[19]
[20]
Y. Schrodi, T. Ung, A. Vargas, G. Mkrtumyan, C. W. Lee, T. M. Champagne, R. L. Pederson, S. H.
Hong, Clean. 2008, 36, 669-673.
PR Newswire: http://www.prnewswire.com/news-releases/elevance-renewable-sciences-
announces-joint-venture-with-wilmar-international-to-build-world-scale-biochemical-refinery-
97299669.html 2010.
[21]
[22]
J. Patel, S. Mujcinovic, W. R. Jackson, A. J. Robinson, A. K. Serelis, C. Such, Green Chem. 2006, 8,
450-454.
D. R. Anderson, V. Lavallo, D. J. O'Leary, G. Bertrand, R. H. Grubbs, Angew. Chem. 2007, 119,
7400-7403.
[23]
[24]
[25]
http://cen.acs.org/articles/94/i4/Elevance-Advances-Metathesis-Route.html.
R. Hoogenboom, T. F. A. Wilms, T. Erdmenger, U. S. Schubert, Aust. J. Chem. 2009, 62, 236-243.
a) C. Samojłowicz, E. Borré, M. Mauduit, K. Grela, Adv. Synth. Catal. 2011, 353, 1993-2002; b) C.
O. Kappe, Angew. Chem. Int. Ed. 2004, 43, 6250-6284; c) M. B. Gawande, S. N. Shelke, R. Zboril,
R. S. Varma, Acc. Chem. Res. 2014, 47, 1338-1348; d) V. Polshettiwar, M. N. Nadagouda, R. S.
Varma, Aust. J. Chem. 2009, 62, 16-26; e) A. de la Hoz, A. Diaz-Ortiz, P. Prieto, in Alternative
Energy Sources for Green Chemistry, The Royal Society of Chemistry, 2016, pp. 1-33.
a) P. Appukkuttan, W. Dehaen, E. Van der Eycken, Org. Lett. 2005, 7, 2723-2726; b) F. C.
Bargiggia, W. V. Murray, J. Org. Chem. 2005, 70, 9636-9639; c) C. O. Kappe, A. Stadler, D.
Dallinger, in Microwaves in Organic and Medicinal Chemistry, Wiley-VCH Verlag GmbH & Co.
KGaA, 2012, pp. 1-7; d) G. B. Dudley, R. Richert, A. E. Stiegman, Chem. Sci. 2015, 6, 2144-2152.
a) C. Yang, W. V. Murray, L. J. Wilson, Tetrahedron Lett. 2003, 44, 1783-1786; b) T. Morris, D.
Sandham, S. Caddick, Org. Biomol. Chem. 2007, 5, 1025-1027; c) S. Garbacia, B. Desai, O.
Lavastre, C. O. Kappe, J. Org. Chem. 2003, 68, 9136-9139.
[26]
[27]
[28]
[29]
C. P. Casey, J. Chem. Educ. 2006, 83, 192.
a) S. T. Nguyen, R. H. Grubbs, J. W. Ziller, J. Am. Chem. Soc. 1993, 115, 9858-9859; b) P. Schwab,
R. H. Grubbs, J. W. Ziller, J. Am. Chem. Soc. 1996, 118, 100-110; c) T. M. Trnka, R. H. Grubbs, Acc.
Chem. Res. 2001, 34, 18-29.
[30]
[31]
S. H. Hong, A. G. Wenzel, T. T. Salguero, M. W. Day, R. H. Grubbs, J. Am. Chem. Soc. 2007, 129,
7961-7968.
a) M. Ulman, R. H. Grubbs, J. Org. Chem. 1999, 64, 7202-7207; b) S. K. Collins, in Handbook of
Metathesis, Vol. 1 (Eds.: R. H. Grubbs, A. G. Wenzel, D. J. O'Leary, E. Khosravi), Wiley-VCH Verlag
GmbH & Co. KGaA, 2015, pp. 343-377; c) Y. Schrodi, in Handbook of Metathesis, Vol. 1 (Eds.: R.
H. Grubbs, A. G. Wenzel, D. J. O'Leary, E. Khosravi), Wiley-VCH 2015, pp. 323-342.
a) G. S. Forman, A. E. McConnell, M. J. Hanton, A. M. Z. Slawin, R. P. Tooze, W. J. van Rensburg,
W. H. Meyer, C. Dwyer, M. M. Kirk, D. W. Serfontein, Organometallics 2004, 23, 4824-4827; b) G.
W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106, 4044-4098; c) S. C. Marinescu, R. R.
Schrock, P. Müller, A. H. Hoveyda, J. Am. Chem. Soc. 2009, 131, 10840-10841.
J. Patel, S. Mujcinovic, W. R. Jackson, A. J. Robinson, A. K. Serelis, C. Such, Green Chem. 2006, 8,
450-454.
[32]
[33]
[34]
M. Arshad, S. Saied, A. Ullah, RSC Adv. 2014, 4, 26439-26446.
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Graphical Abstract
Remarkably Efficient Microvawe-Assisted Cross-
Metathesis of Lipids in Solvent Free Conditions
Aman Ullah* and Muhammad Arshad
Rapid and effective conversion of lipids: A swift solvent free conversion of lipids into multiple
high value products based on microwave-assisted metathesis approach is developed. The high
conversions (upto 99%) were achieved within few minutes. The unprecedented turnover
numbers and turnover frequencies for ethenolysis of canola esters (~1.5 million & 26,000),
canola oil (~0.6 million & 10,300), and waste cooking oil (~ 1 million & 17,900) and for
alkenolysis of canola esters (~1.6 million &, 27500) were achieved.
24
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