Oxidation of olefins using atmospheric oxygen atoms initiated by tert -butylhydroperoxide or hydrogen peroxide with silver nanoparticles deposited on MCM-41 as catalysts

Article abstract of DOI:10.1039/c5gc03110a

Silver nanosized particles were grown on the surface and in the channels of mesoporous silica (MCM-41) by stirring a mixture of AgNO₃ and polyvinylpyrrolidone (PVP) in ethylene glycol in a 1:20 weight ratio with MCM-41 for 1 h. The heterogeneous product was analysed by BET surface area and X-ray powder diffraction measurements, as well as TEM images which indicated that 5 to 20 nm sized Ag particles were on the surface of MCM-41. The dried material, suspended in a mixture of 1,2-dichloroethane and acetonitrile and in the presence of ^tBuOOH held at 80 °C for 24 h, was capable of the oxidation of the olefins (Z)-cyclooctene, cyclohexene, styrene and indene resulting in a variety of oxidized products. Comparable oxidation was also accomplished in a green solvent mixture consisting of 3% NaCl dissolved in H₂O and ^tBuOH (1:1 by volume). The catalyst was active for five sequential cycles. After the first cycle, H₂O₂ instead of ^tBuOOH could be used as the radical initiator as the Ag nanoparticles were passivated by the formation of AgCl on the surface. This research illustrates a method of oxygen activation allowing for the transfer of an oxygen atom from the atmosphere onto an olefin, presumably via the formation of a peroxide radical.

Full text of DOI:10.1039/c5gc03110a

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Oxidation of olefins using atmospheric oxygen atoms initiated by
tert-butylhydroperoxide or hydrogen peroxide with silver
nanoparticles deposited on MCM-41 as catalysts
Zhichao Chena and Rudy L. Lucka
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Silver nanosized particles were grown on the surface and in the channels of mesoporous silica (MCM-41) by stirring a
mixture of AgNO3 and polyvinylpyrrolidone (PVP) in ethylene glycol in a 1:20 weight ratio with MCM-41 for 1h. The
heterogeneous product was analysed by BET surface area and X-ray powder diffraction measurements, as well as TEM
images which indicated that 5- to 20-nm sized Ag particles were on the surface of MCM-41. The dried material, suspended
in a mixture of 1,2-dichloroethane and acetonitrile and in the presence of tBuOOH held at 80 oC for 24 h, was capable of
the oxidation of the olefins (Z)-cyclooctene, cyclohexene, styrene and indene resulting in a variety of oxidized products.
Comparable oxidation was also accomplished in a green solvent mixture consisting of 3%NaCl dissolved in H2O and tBuOH
(1:1 by volume). The catalyst was active for five sequential cycles. After the first cycle, H2O2 instead of tBuOOH could be
used as the radical initiator as the Ag nanoparticles were passivated by the formation of AgCl on the surface. This research
illustrates a method of oxygen activation allowing for the transfer of an oxygen atom from the atmosphere onto an olefin,
presumably via the formation of a peroxide radical.
www.rsc.org/
have also been reported. There have also been many publications
recently utilizing TBHP as an oxygen source but these have all been
accomplished stoichiometrically.14-22 It is clearly not efficient to
Introduction
The use of tert-butylhydroperoxide (TBHP) and H2O2 to form
epoxides from olefins using various homogenous catalysts such as
MoO2(OPR3)2, M = Mo or W,1-3 and tetranuclear Mo4O4(O2PR2)4 and
heterogenous systems such as nano-sized particles of titanium-
containing mesoporous molecular sieves4 and two-dimensional,
hydrogen bonded cross-linked molybdenum(VI) network polymers
have been previously reported.5 In this article, an oxygen atom
transfer reaction where atmospheric oxygen is used to react with
olefins to form epoxides in the presence of a heterogenous catalyst
consisting of silver nanoparticles deposited inside of and on the
surface of MCM-41 is detailed.
have to synthesize TBHP in order to effect stoichiometric oxygen
atom transfer, though this consideration is not restricting if that is
the only way to synthesize the desired compound.
This report details the synthesis and characterization of Ag
nanoparticles deposited onto MCM-41 and studies on their use as
oxidation catalysts with TBHP. Previous studies demonstrated the
synthesis of Ag nanoparticles using PVP23 and the formation of Ag
wires inside of mesoporous silica including MCM-41.24-27
Interestingly, the adventitious formation of AgCl on the surface of
recycled Ag nanoparticle catalyst permitted the use of H2O2 as an
initiator.
There are many literature examples of oxygen atom transfer
(OAT) reactions using transition metal catalysts and H2O2 and N2O
as oxygen sources.6 Recently, other more complex molecules have
been utilized to effect OAT such as iodosobenzene (PhIO),7
dimethyldioxirane (DMDO),7 2-tert-butylsulfonyliodosobenzene
(sPhIO),8 all requiring various iridium catalysts, and AcOOH and
KHSO5 which require a manganese based metalloenzyme to
accomplish benzylic oxygenation and olefin epoxidation.9 In these
cases, the nature of the OAT agent and/or the catalyst is complex
and certainly cannot be considered suitable from a “green”
chemistry10 perspective. Epoxidations with gold particles supported
on graphite, TiO2 and SiO2 surfaces11, 12 and on polyoxometalates13
Experimental
General method
A Scintag XDS2000 powder diffractometer was used to confirm the
formation of MCM-41 and the deposition of silver particles. The BET
surface area of MCM-41 and its derivatives were measured on an
ASAP 2000 physisorption analyzer. TEM images were taken with a
JEOL-JEM-2010 transmission electron microscope. The thermal
stability of Agnp-MCM-41 was tested using a Shimadzu TGA-50. A
Shimadzu GCMS-QP5050 was used to identify substrates and their
oxidation products resulting from catalysis. Infrared spectra were
obtained on a PerkinElmer Frontier FTIR. Most chemicals including
polyvinylpyrrolidone (PVP, mw=55000), silver nitrate (99%),
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tetraethyl orthosilicate (TEOS, 98%), hexadecyltrimethylammonium
bromide (CTAB, 99%), cyclohexene (99%), styrene (99%), indene
(99%), dodecane (99%) were purchased from Sigma-Aldrich.
Ethylene glycol (EG) and sodium hydroxide (NaOH, 98.0%) were
purchased from Fisher Scientific. (Z)-cyclooctene (95%), tert-butyl
hydroperoxide (TBHP, 70% solution in water), and sodium chloride
were purchased from Alfa Aesar, Acros Organics and Macron
respectively. All solvents were used as received.
adaptation. Ag+ was reduced by ethylene glycol with the added PVP
regulating the size of the nanoparticles, the reduction growth rate
and hindering agglomeration.29 A TGA curve on the almost dried
material, Fig. S1, revealed a small weight loss of 1.2% up to 150 °C
due to solvent residue and then decomposition from 250 to 470 °C,
resulting in a weight loss of 18.8% presumably due to organic
combustion.
As noted previously, the nature of the particles can be controlled
by varying the reduction time, Ag+ and PVP concentrations, and
temperature29 and our synthetic conditions produced the most
active catalyst. The final cured product did contain some PVP
sticking to the surface of the desired Agnp-MCM-41 as the product
mass of 0.34 g (i.e., for the cured product) was slightly more than
the theoretical of 0.33 g. Calcining at 550 °C for 24h did not remove
this but the product did change color after use as a catalyst
suggesting that adsorbed PVP could be removed by washing.
Transmission electron microscope. The TEM images of synthesized
Agnp-MCM-41 indicated that spherical silver particles were found
deposited inhomogeneously on the surface of MCM-41 with
diameters mostly ranging from 5 nm to 20 nm as shown in the
particle size distribution displayed as the inset in Figure 1. However,
some particles are at 100 nm (Figure 1b). The MCM-41 channels
were measured to be around 3.1 nm wide which is consistent with
literature results. Silver particles were also found inside the MCM-
41 channels (Figure 1c). The recycled Agnp-MCM-41 material has
larger particles (50-200 nm) with a few particles found under 50 nm
in diameter (Figure 1d). This is probably due to the agglomeration
of silver particles during the 72h reaction.33
Preparations
Synthesis of MCM-41. MCM-41 was synthesized with CTAB as the
template in the compositional ratio: 1.0 TEOS/0.1 CTAB/0.3
NaOH/60 H2O as reported previously.28 The mixture was kept
unstirred in a Parr bomb at 110 °C for 96h, filtered, washed with
deionized water and dried in an oven at 80 °C. MCM-41 was
obtained by calcining the solid at 550 °C for 24h.
Synthesis of Agnp-MCM-41. The nano-sized Ag particles were
prepared, eqn 1, based on an adaptation to a literature procedure29
where instead of preparing solutions of Ag nanoparticles, Ag+ was
reduced with PVP in ethylene glycol in the presence of already
formed MCM-41.30, 31 The reaction of Ag+ and PVP in solution is
believed to result in PVP-capped Ag nanoparticles.32 0.047g AgNO3
(0.27 mmol) were dissolved in 20 mL of ethylene glycol, to which
0.98 g PVP (0.018 mmol) and 0.30 g MCM-41 were subsequently
added. The mixture was stirred at room temperature for 30 min and
then heated at 180 °C for 1h. Upon filtration and washing, a
brownish yellow powder (0.39 g) was obtained which was dried at
100 °C in a furnace. This material referred to as Agnp-MCM-41 was
used as the catalyst. The cured Agnp-MCM-41 (0.34g) was prepared
by calcination at 500 °C under air for 4 hours.
Powder X-ray diffraction. The formations of MCM-41 and silver
particles were also confirmed by powder X-ray diffraction
spectroscopy. The signals from MCM-41 are much stronger than
those of silver particles as only 10% of silver to MCM-41 by weight
was used in the reduction process (Figure 2). The signal-to-noise
ratio is weak for Agnp-MCM-41 probably due to organics (PVP) from
the reduction reaction. This ratio can be slightly enhanced by
calcination at 500 °C for 4h which results in the removal of organics.
The 2-theta signals at 38.1°, 44.5°, 64.4° and 77.5° are the (1,1,1),
(2,0,0), (2,2,0) and (3,1,1) indexed planes for Ag particles.34
After the catalytic reaction, the spectrum for recycled Agnp-MCM-
41 indicated formation of AgCl with 2-theta peaks at 27.8° (1,1,1),
32.2° (2,0,0), 46.1° (2,2,0).35, 36 There was also a peak at 18.1o which
is not observed in the spectrum when the reaction is conducted in a
mixture of 3%NaCl in H2O/tBuOH as solvent, Fig. S2. Additionally,
only the FTIR spectrum of the solid catalyst recycled from the
dichloroethane/acetonitrile solvent mixture contains two
absorptions at 1151 and 1206 cm-1 perhaps indicating the presence
of C-O bonds, Fig. S3. It is possible that a polyether compound
formed in the reaction, perhaps PEG, coating the Agnp. A study on
the synthesis of silver nanoparticles in PEG assigned a 2θ peak at
19° to PEG on the silver surface.37
Catalytic epoxidation reaction. 0.05 g Agnp-MCM-41 were placed in
a two-neck flask fitted with a condenser, and 4.6 mmol of substrate
in a 1,2-dichloroethane (5.0 mL) and acetonitrile (0.5 mL) solution
were added. Next, 0.3 mL dodecane (2.9 mmol) which is the
internal standard and 0.03 mL 70% TBHP (0.24 mmol) in H2O were
added. The mixture was heated to 80 °C and kept there for three
days. For each reaction, two samples, after 24h and then 72h were
collected for GC-MS measurements. The catalyst was recovered by
filtration and washed first with 1,2-dichloroethane and then
acetonitrile. A white solid was obtained and dried in a furnace at
100 °C for 4-5 hours. The recycled catalyst was then used under the
conditions mentioned above with freshly loaded reactants. This
recycling procedure was repeated four times. A comparison
reaction using (Z)-cyclooctene as the substrate was conducted
under pure nitrogen instead of air.
The presence of AgCl was also confirmed by a qualitative analysis
method. A white suspension was observed upon addition of a few
drops of HNO3 to the filtrate from recycled Agnp-MCM-41 and an
ammonia solution mixture. Silver chloride has been reported to
Results
Catalysts characterization. The synthesis of MCM-41 followed a
literature procedure28 but the deposition of the Agnp consisted of an
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Table 1. (Z)-cyclooctene epoxidation catalyzed by Agnp-MCM-41 or cured
Agnp-MCM-41 with TBHP as initiator
Period
Catalyst
Weight
(mg)
51
Conversion
(%)
16.9
Selectivity
(%)
86.2
Agnp-MCM-41 (1st cycle)
Agnp-MCM-41 (2nd cycle)
cured Agnp-MCM-41
Agnp-MCM-41 (1st cycle)
Agnp-MCM-41 (2nd cycle)
Agnp-MCM-41 (3rd cycle)
Agnp-MCM-41 (4th cycle)
Agnp-MCM-41 (5th cycle)
cured Agnp-MCM-41
24h
48
50
52
49
42
37
26
50
35.2
27.8
74.8
67.3
63.6
67.7
61.8
59.7
85.1
86.6
96.8
99.4
96.1
98.9
97.2
96.1
72h
Catalysis
Epoxidation of (Z)-cyclooctene to (1S,8S)-9-
oxabicyclo[6.1.0]nonane. (Z)-cyclooctene, in the presence of the
Agnp-MCM-41 catalyst under the stated experimental conditions,
reacted to form epoxide products (16.9% conversion, 86.2%
selectivity) after a 24h period (Table 1). These values increased to
74.8% and 96.8% respectively after 72 hours. Since insufficient
TBHP (5%) was used in the reaction, molecular oxygen from the air
is the major oxygen atom source for the formation of epoxides as
noted previously with studies on gold nanoparticles.13 Chlorine
atoms can also serve as promoters for ethylene epoxidation by
modifying the electronic environments and number of active sites
on the surface of a silver nanopowder catalyst.40 This could explain
the better conversion (35.2%) observed for the recycled Agnp-MCM-
41.
Figure 1. TEM image of Agnp-MCM-41 (a, b, c) and recycled Agnp-MCM-41 (d).
form on silver particles during catalytic ethylene epoxidation
reactions.38 Therefore, AgCl formation, evident at the end of a
catalytic cycle, is due to the presence of chlorinated solvents
reacting with Agnp
.
BET surface area test. BET measurements on the initially prepared
MCM-41 established a surface area of 925 m2/g which is consistent
with literature results.28 With Agnp-MCM-41, silver particles in the
mesoporous channels and on the surface decreased the surface
area to 338 m2/g. It has been reported that 1% Ag nanowires in
MCM-41 channels decreased the surface area from 965 m2/g to 751
m2/g.39 The possibility that organics from the silver reduction
process, coating the surface or deposited within the channel in
Agnp-MCM-41, also contributed to the surface area decrease cannot
be ruled out. The surface area further decreased to 208 m2/g for
the recycled Agnp-MCM-41 material.
The Agnp-MCM-41catalyst was recycled four times and remained
active with a noteworthy selectivity to epoxide of over 95% after a
72h period. The decrease in conversion is likely due to the loss of
catalytic particles during the recycling process. The experimental
conditions utilized to recycle the catalyst, specifically drying in a
furnace at 100 oC for 4-5 hours, are not sufficient to remove
organics adsorbed either on the surface or within the channels of
Agnp-MCM-41 as observed by the 25.3% decrease in weight
measured by TGA, see Fig. S4. Reductions in weight due to
adsorbed molecules within MCM-4141and also on functionalized
MCM-4142 have been previously described. The cured Agnp-MCM-41
sample resulted in a lower conversion (59.7%) during a 72h period
probably because the silver particles sintered upon calcination at
500 °C. An attempt to use H2O2 instead of TBHP as the initiator was
not successful with freshly prepared Agnp-MCM-41 since H2O2
decomposed immediately upon addition of the catalyst. However,
the H2O2 initiated reaction worked with recycled catalyst resulting
in a 76.7% conversion and 88.1% selectivity to (1S,8S)-9-
oxabicyclo[6.1.0]nonane. As confirmed by powder X-ray diffraction
and qualitative analysis of the recycled material, silver chloride
forms and may have covered the surface of the silver nanoparticles,
preventing H2O2 decomposition on a pure silver atom surface.
There is a great difference in the rates of the reaction depending
on if they are conducted under oxygen or nitrogen as a plot of
Figure 2. Powder X-ray diffraction of Agnp-MCM-41 (top), cured Agnp-MCM-41
(middle) and recycled Agnp-MCM-41 from 1,2-Dichloroethane-acetonitrile (10:1)
solvent (bottom). : peaks of Ag, : peaks of AgCl.
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Table 2. Conversion and selectivity to cis-9-oxabicyclo[6.1.0]nonane in
different solvents*
period. These reactions can also be efficiently conducted in a more
green solvent44 mixture consisting of 3%NaCl in a H2O/tBuOH (1:1
by volume) solvent mixture (Table 2).
Solvents
Conversion (%)
16.9
Selectivity (%)
86.2
Agnp-MCM-41 catalysis on other substrates containing C=C bonds.
Given the high selectivity to form the oxidized product with (Z)-
cyclooctene, reactions with other substrates containing C=C bonds
were also explored, namely cyclohexene, styrene and indene. The
results indicate that the selectivity of the products, obtained from
oxidation reactions catalysed by Agnp-MCM-41, vary depending on
the substrate (Table 3). A high conversion (93.6%) in a 24h period
1,2-Dichloroethane-
acetonitrile (10:1)
1,2-Dichloroethane
Hexane
17.1
0.2
89.9
88.9
82.0
75.5
67.6
86.3
Ethanol
0.2
T-butanol
Toluene
0.1
was observed for cyclohexene with 68.3% selectivity to 2-
cyclohexen-1-one and 24.8% to 2-cyclohexen-1-ol. The desired
epoxide, 7-oxabicyclo[4.1.0]heptane, accounted for 3.2% of the
products obtained, a much lower desired selectivity than that for
the (Z)-cyclooctene reaction. Benzaldehyde (50.8%) and
benzeneacetaldehyde (38.4%) were the two major products from
oxidation of styrene under similar conditions. The oxidation of
indene catalysed by Agnp-MCM-41 resulted in a decent yield of 1,3-
dihydro-2H-inden-2-one in a 24h period with a high selectivity
(84.6%) determined by GC-MS.
2.5
3% NaCl in water-tert-
butanol (1:1)
16.2
*Reaction condition: 4.6 mmol (Z)-cyclooctene, 0.05 g Agnp-MCM-41, 0.24
mmol TBHP, 5.5 mL solvent, 80 °C, air, 24h.
conversion rate for the production of (1S,8S)-9-
oxabicyclo[6.1.0]nonane illustrates, Fig. S5. Essentially, oxidation
products under nitrogen were not detected in the first 1h of
reaction and only a 1.1% conversion resulted after 5h. In
comparison, the reaction under air is faster with a 3.3% conversion
during a 5h period. This suggests that (1S,8S)-9-
Mechanism
A radical mechanism for (Z)-cyclooctene epoxidation catalysed by
the MCM-41 supported silver nanoparticles catalyst (Scheme 1)
similar to what was noted previously is proposed.11, 45, 46 The
reaction is initiated by t-BuO∙ or t-BuOO∙ radicals resulting from the
thermolysis of TBHP on the surface of silver particles.47 A hydrogen
atom is then abstracted from (Z)-cyclooctene by the radical to form
an allylic radical 1, followed by an oxidation reaction with
oxabicyclo[6.1.0]nonane is mostly generated through the proposed
free radical mechanism, Scheme 1, which requires atmospheric
oxygen. The decomposition of THBP to generate free radicals is
usually considered the rate determining step.43 Conducting
thereaction under pure nitrogen for longer periods resulted in 5.8%
(24h) and 6.5% (72h) conversions, conclusively demonstrating that
oxygen molecules from the air participate and oxidize (Z)-
cyclooctene in the reaction.
atmospheric oxygen atoms to form radical 2. Radical 2 can abstract
a hydrogen atom from (Z)-cyclooctene, resulting in a cyclooctene
hydroperoxide 3 and regenerating radical 1. Cyclooctene
Solvents effect. Solvents were found to affect the efficiency of (Z)-
cyclooctene epoxidation. Similar results were reported for a gold
catalyst.13 Catalytic reactions carried out in pure 1,2-dichloroethane
or the 1,2-dichloroethane-acetonitrile (10:1) solvent mixture
showed higher conversions compared to reactions conducted in
hexane, ethanol and t-butanol (Table 2). The use of toluene is not
appropriate as approximately 1.6% of toluene was oxidized to
benzaldehyde (68.3%) and benzyl alcohol (28.0%) during a 24h
hydroperoxide could decompose to form an enone product,12 or to
form an HO∙ radical and a radical 4 on the surface of the silver
nanoparticles. 2-Cycloocten-1-ol product forms via hydrogen
abstraction from (Z)-cyclooctene by radical 4. Radical 4 could also
attack the C=C bond of (Z)-cyclooctene to form an intermediate 5,
resulting in the desired epoxide product via cleavage.
Table 3. Agnp-MCM-41 catalysis on different substrates containing C=C bonds initiated by TBHP*
Substrate
24h
72h
Conversion (%)
16.9
Selectivity (%)
Cis-9-oxabicyclo[6.1.0]nonane: 86.2
2-Cycloocten-1-ol: 1.5
Conversion (%)
74.8
Selectivity (%)
Cis-9-oxabicyclo[6.1.0]nonane: 96.8
2-Cycloocten-1-ol: 0.3
(Z)-cyclooctene
2-Cycloocten-1-one: 9.1
2-Cycloocten-1-one: 2.7
Cyclohexene
93.6
7-Oxabicyclo[4.1.0]heptane: 3.2
2-Cyclohexen-1-ol: 24.8
99.5
7-Oxabicyclo[4.1.0]heptane: 0.7
2-Cyclohexen-1-ol: 18.1
2-Cyclohexen-1-one: 68.3
2-Cyclohexen-1-one: 59.7
Styrene
Indene
45.7
24.6
Benzaldehyde: 50.8
Benzeneacetaldehyde: 38.4
1,3-Dihydro-2H-inden-2-one: 84.6
86.5
66.1
Benzaldehyde: 35.9
Benzeneacetaldehyde: 25.3
1,3-Dihydro-2H-inden-2-one: 62.2
*Reaction condition: 4.6 mmol substrate, 0.05 g Agnp-MCM-41, 0.24 mmol TBHP, 5 mL 1,2-dichloroethane, 0.5 mL acetonitrile, 80 °C, air.
4 | J. Name., 2012, 00, 1-3
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To test for the heterogeneity of the reaction and the stability
of Agnp on MCM-41 during the reaction, a hot filtration at 80 °C
was performed after 24h of reaction.48, 49 The filtrate was stirred
for another 48h, resulting in a 64.0% conversion which is lower
than the 74.8% conversion after 72h for a standard reaction
conducted without filtration, Fig. S6. This demonstrates that
catalyst particles leached out into the solution during reaction.
In comparison, the filtrate from a cold filtration, conducted at
room temperature, resulted in a lower conversion of 46.0%. This
reveals that the leached silver catalyst nanoparticles can be
reabsorbed onto the solid to some extent when the reaction
cools down to room temperature.
Agnp-MCM-41 after 24h of reaction, to the rate for a solution
which was not filtered.
Acknowledgements
We gratefully acknowledge the assistance of Wei Wei from the
laboratory of Professor Yuhang Hu in conducting the BET
measurements. Constructive and helpful suggestions by
reviewers are noted.
Conclusion
Silver nanoparticles supported on mesoporous MCM-41 have
been synthesized via the reduction of AgNO3 by ethylene glycol
in the presence of PVP. The catalytic particles are found to be
located in the channels and on the surface of MCM-41. With
substoichiometric TBHP (5%) as the initiator, the catalyst is
capable of using oxygen atoms from the atmosphere for the
epoxidation of (Z)-cyclooctene. The catalyst is recyclable with
selectivity to the desired epoxide cis-9-oxabicyclo[6.1.0] nonane
higher than 85% and was found to have AgCl on the surface of
the Ag nanoparticles which allowed for the use of H2O2 as
radical initiator. Other alkenes, such as cyclohexene, styrene and
indene, resulted in a variety of oxidized products. Under
reaction conditions, silver particles dissociated off of the Agnp
MCM-41 material and these were also capable of catalysis.
-
Scheme 1. Proposed mechanism for (Z)-cyclooctene epoxidation on
MCM-41 supported Ag catalyst.
Supplementary materials
Fig. S1. TGA curve of freshly prepared Agnp-MCM-41 under air at
a heating rate of 10 °C/min. Fig. S2. Powder X-ray diffraction of
recycled Agnp-MCM-41 from an H2O/tBuOH (1:1) solvent
mixture containing 3% NaCl and a 1,2-dichloroethane-
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acetonitrile (10:1) solvent mixtures. Fig. S3. Infrared spectra of
Agnp-MCM-41, recycled Agnp-MCM-41 from a 1,2-
dichloroethane-acetonitrile (10:1) solvent mixture and recycled
Agnp-MCM-41 from an H2O/tBuOH (1:1) solvent mixture
containing 3% NaCl. Fig. S4. TGA curve of recycled Agnp-MCM-
41 under air at a heating rate of 10 °C/min. Fig. S5. Comparison
of Agnp-MCM-41 catalyzed (Z)-cyclooctene epoxidation rate for
the first 5h of reaction conducted under air and under nitrogen.
Fig. S6. Comparison of (Z)-cyclooctene epoxidation rates for
solutions that were hot filtered and cold filtered to remove solid
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Green Chemistry
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DOI: 10.1039/C5GC03110A
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Green Chemistry
View Article Online
DOI: 10.1039/C5GC03110A
Oxidation of olefins using atmospheric oxygen atoms initiated by tert-
butylhydroperoxide or hydrogen peroxide with silver nanoparticles deposited
on MCM-41 as catalysts
Zhichao Chen,a Rudy L. Lucka
Graphical Abstract
The 20 word sentence
Silver nanoparticles on MCM-41 oxidize olefins using atmospheric oxygen
initiated by peroxides with 3% NaCl in H2O/tBuOH as solvent.