about omics groupmicrocapsules [pt]/peg@sio 2: selective hydrosilylation catalyst entry solvent...
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About OMICS Group
OMICS Group International is an amalgamation of Open Access publications and worldwide international science conferences and events. Established in the year 2007 with the sole aim of making the information on Sciences and technology ‘Open Access’, OMICS Group publishes 400 online open access scholarly journals in all aspects of Science, Engineering, Management and Technology journals. OMICS Group has been instrumental in taking the knowledge on Science & technology to the doorsteps of ordinary men and women. Research Scholars, Students, Libraries, Educational Institutions, Research centers and the industry are main stakeholders that benefitted greatly from this knowledge dissemination. OMICS Group also organizes 300 International conferences annually across the globe, where knowledge transfer takes place through debates, round table discussions, poster presentations, workshops, symposia and exhibitions.
About OMICS Group Conferences
OMICS Group International is a pioneer and leading science event organizer, which publishes around 400 open access journals and conducts over 300 Medical, Clinical, Engineering, Life Sciences, Pharma scientific conferences all over the globe annually with the support of more than 1000 scientific associations and 30,000 editorial board members and 3.5 million followers to its credit.
OMICS Group has organized 500 conferences, workshops and national symposiums across the major cities including San Francisco, Las Vegas, San Antonio, Omaha, Orlando, Raleigh, Santa Clara, Chicago, Philadelphia, Baltimore, United Kingdom, Valencia, Dubai, Beijing, Hyderabad, Bengaluru and Mumbai.
17.8.2015
The design and synthesis of silica-based
catalytic microreactors
Raed Abu-Reziq
Institute of Chemistry, Casali Center of Applied Chemistry and
The Center for Nanoscience and Nanotechnology
The Hebrew University of Jerusalem, Israel
Ceramics-2015, Chicago, USA
Catalysis
Health
Food
Basic
and fine
chemicals
Environment
Energy
New
Materials
Catalysis shapes our world
Importance of catalysis: more than 90% of the industrial processes
are catalyzed (chemicals, pharmaceutics, materials, polymers, energy, etc.)
Catalysis Homogeneous Heterogeneous
• Organometallic complexes
•Enzymes
•Organocatalysts
• Supported metals
• Supported organometallic complexes
• Metal oxides, sulfides (PtO2, RuO2 etc.)
Homogeneous catalysis Heterogeneous catalysis
K. D. Wiese et al, Top Organomet. Chem., 2006, 18, 1.
H. W. Bohnen et al, Adv. Catal. 2002, 47, 1.
• High activity and selectivity
• Not easily recovered
• Expensive
• Decrease of activity and selectivity
• Easily recovered
• Economic
How to bridge homogeneous and heterogeneous catalysis?!!
Catalysis
Nanocatalysis??
Nanocatalysis; Quasi-homogeneous catalysis; Semi-
heterogeneous catalysis
W. J. Stark et al, Chem. Eur. J., 2010, 16, 8950.
Metal nanoparticles as active catalyst Metal nanoparticles as support
Preparation of heterogeneous catalysts in the nanometer length scale
Nanocatalysis
Size Effects
K. An and G. A. Somorjai, ChemCatChem, 2012, 14, 1512.
Nanocatalysis
Shape Effects
S.U. Son et al, Angew. Chem. Int. Ed. 2007, 46, 1152
Nanocatalysis: Magnetically separable systems
a) V. Polshettiwar et al, Chem. Rev., 2011, 111, 3036. b) S. Shyles et al, Angew. Chem. Int. Ed., 2010, 49, 3428. c) Y. Zhu et
al, ChemCatChem, 2010, 2, 365. d) V. Polshettiwar et al, Green Chem., 2010,12, 743.
Our current research activity
Magnetically separable systems
Supports with well-defined
nanostructures
Nano- and Microreactors
Bridging
homogeneous
and
heterogeneous
catalysis
Nano & Microreactors
Yolk-shell nanoreactors
Y. Yang et al, Angew. Chem. Int. Ed. 2012, 51, 9164. E. V. Shevchenko et al, Adv. Mater. 2008, 20, 4323.
Carbon nanotubes as nanoreactors
S. A. Miners et al, Chem. Commun., 2013, 49, 5586.
m.p. (°C) for NaCl= 803
m.p. (°C) for BMIm[PF6]= -78
Ionic liquid based microreactors
P. Wasserscheid, T. Welton in “ Ionic Liquids in Synthesis” 2002.
• Salts that are liquid at ambient temperatures.
• Have stable liquid range of over 300 °C.
• Very low vapour pressure at room temperature.
Ionic Liquids
Applications of ionic liquids:
• Solvent and catalysts (synthesis, catalysis, microwave chemistry, nanochemistry,
multiphasic reactions and extractions)
• Biological uses (biomass processing, drug delivery, biocides, personal care, embalming)
• Engineering (coatings, lubricants, plasticisers, dispersing agents, compatibilisers)
• Physical chemistry ( refractive index, thermodynamics, binary and ternary systems)
• Electrochemistry (metal plating, solar panels, fuel cells, electro-optics, ion propulsion)
N. V. Plechkova, K. R. Seddon, Chem. Soc. Rev. 2008, 37, 123
The high viscosity of ionic liquids limits its applications in industrial processes
Ionic liquid based microreactors
BMIm-PF6@SiO2 microcapsules
Size distribution
TEM image SEM image
E. Weiss et al, Chem. Mater., 2014, 26, 4781.
Particulated ionic liquids: Converting ionic liquids into solid form
BMIm-PF6@SiO2 microcapsules
TGA analysis indicates that the microcapsules are composed of 68% ionic liquid
Parameters affecting the microcapsules synthesis: 1. Type of surfactant
2. Surfactant concentration
3. Ionic liquid: TEOS ratio
BMIm-PF6@SiO2 microcapsules
Brij 78
Tween 80
Triton X-100
Reax 88A Reax 88B
5% Bu-PVP
SDS PS- sulfonated Pluronic 123
BMIm-PF6@SiO2 microcapsules
Characterizations
BMIm-PF6@SiO2 microcapsules
Immobilization of palladium nanoparticles
BMIm-PF6@SiO2 microcapsules
Catalytic applications
Entry Catalyst Solvent Conversion (%) Products (%)
1 Pd/BMIm-PF6@SiO2 water 100 cis-4-octene (88), trans-4-octene (10), n-octane (2)
2 Pd/BMIm-PF6@SiO2 hexane 10 cis-4-octene (10)
3 Pd/BMIm-PF6@SiO2 xylene 100 cis-4-octene (84), trans-4-octene (5), n-octane (11)
4 Pd/BMIm-PF6@SiO2 diethyl ether 100 cis-4-octene (85), trans-4-octene (6), n-octane (9)
5 Pd/C diethyl ether 100 n-octane (100)
6 Pd(OAc)2 BMIm-PF6 100 cis-4-octene (8), n-octane (92)
E. Weiss et al, Chem. Mater., 2014, 26, 4781.
Pd/BMIm-PF6@SiO2 microcapsules
Stability and Recyclability
TEM image SEM image
SEM and TEM images of Pd/BMIm-PF6@SiO2after catalytic applications
Recyclability
BMIm-PF6@SiO2 microcapsules
PEG@SiO2 microcapsules
Surfactants:
Oil phase:
Toluene
Heptane
Cyclohexane
Unpublished results
1 µm
10 µm 1 µm
PEG@SiO2 microcapsules
PEG@SiO2 in toluene PEG@SiO2 in heptane
SEM images SEM image
TEM image TEM image
PEG@SiO2 microcapsules Characterizations
PEG@SiO2 microcapsules [Pt]/PEG@SiO2: Selective hydrosilylation catalyst
Entry Solvent Conversion (%) Selectivity (ratio β:α)
1a Toluene 0 ---
2a Heptane 33 73:27
3a Cyclohexane 57 40:60
4b Cyclohexane >99 92:8
a the catalyst was prepared in the presence of Agrimer AL22 b the catalyst was prepared in the presence of Span 80
Heterogeneous hydrosilylation:
M. Chauhan et al, J. Organomet. Chem. 2002, 645,1.
PEG@SiO2 microcapsules [Pt]/PEG@SiO2: Selective hydrosilylation catalyst
Unpublished results
Chiral ruthenium catalyst@ magnetically separable
silica microreactors
SEM image TEM image
A. Zoabi et al, Eur. J. Inorg. Chem., 2015, 2015
200 nm_ 500 nm_
a b
200 nm_ 500 nm_
a b
Chiral ruthenium catalyst@ magnetically separable
silica microreactors
29Si CP-MAS NMR
XRD pattern STEM/EDS analysis
Characterizations
Chiral ruthenium catalyst@ magnetically separable
silica microreactors Characterizations 13C NMR and 13C CP-MAS NMR
Entry Surfactant
Conversion (%) Enantioselectivity (ee %)
1 Non 0 -
2 CTAB 100 95
3 CTAC 100 95
4 SDS 57 91
5 Bu-PVP 88 92
6 Brij 78 89 93
Chiral ruthenium catalyst@ magnetically separable silica
microreactors
Chiral ruthenium catalyst@ magnetically separable silica
microreactors
Postulated mechanism for the transportation of the reactants to the core of
catalytic microreactors
Surfactant Zeta potential (mv)
Non -26.4
CTAC +44.4
Bu-PVP -3.2
SDS -41.2
Chiral ruthenium catalyst@ magnetically separable silica
microreactors
Entry Catalyst Yield Enantiomeric
excess (%)
1 Microreactors 90 86
2 Empty capsule anchored catalyst 8 N/A
3 Sol-gel anchored catalyst 41 76
Chiral ruthenium catalyst@ magnetically separable silica
microreactors
Tethering the catalyst in the homogeneous zone of the microreactors is
required for obtaining high reactivity and selectivity
Comparison of catalytic activity of the microreactors versus sol-gel entrapped and
anchored catalyst in the asymmetric transfer hydrogenation of 4-bromoacetophenone
Our current research activity
Magnetically separable systems
Supports with well-defined
nanostructures
Nano- and Microreactors
Bridging
homogeneous
and
heterogeneous
catalysis
Palladium nanoparticles supported on magnetically
recoverable hybrid organic-silica nanoparticles
Preparation of Pd(nano)/MNP@IL-SiO2 catalytic hybrid nanoparticles :
Magnetically separable systems
S. Omar et al, J. Phys. Chem. C, 2014, 118, 30045
Characterizations
200 nm
100 nm
100 nm
20 nm
SEM of MNP@IL-SiO2
TEM of MNP@IL-SiO2
TEM of Pd(nano)/MNP@IL-SiO2
STEM of Pd(nano)/MNP@IL-SiO2
Pd(nano)/MNP@IL-SiO2
Si O
Fe Pd
Pd(nano)/MNP@IL-SiO2
Characterizations TGA
XRD
δ (ppm)
δ (ppm)
29Si CP-MAS NMR
13C CP-MAS NMR
Pd(nano)/MNP@IL-SiO2
Catalytic applications
Pd(nano)/MNP@IL-SiO2
Catalytic applications
S. Omar et al, J. Phys. Chem. C, 2014, 118, 30045
0
20
40
60
80
100
1 2 3 4 5
Co
nv
ersi
on
%
Number of cycles
500 nm
Suzuki reaction between bromonenzene and phenyl boronic acid
Heck reaction between iodobenzene and ethyl acrylate
SEM images of recycled catalyst
after 4 cycles
Pd(nano)/MNP@IL-SiO2
Recycling of the catalysts
Conclusions:
•Two methods for preparing new materials based on ionic liquids or PEG encapsulated
in silica shells were developed
•The methods enable particulating ionic liquids or PEGs and converting them in
powder form.
•The methods give opportunities to design ionic liquids or PEGs with new properties.
•The methods enable controlling selectivity and reactivity of catalysts
•Magnetically separable nanocatalysts were designed and applied successfully in
different organic transformations.
Group members:
1. Suheir Omar
2. Esti Weiss
3. Suzana Natour
4. Amani Zoabi
5. Charlie Batarseh
6. Ahmad Zarour
7. Sumaya Abu-Ghannam
8. Diana Gertopski
9. Dr. Maneesh Gupta
Thank You!
Funding support
1. Dr. Gilat Nizri
2. Dr. Saleh Abu-Lafi
3. Dr. Bishnu Dutta
4. Dr. Khalil Hamza
5. Rony Schwarz
6. Yafit Schnell
Former group members:
Casali Foundation Ministry of Science and Culture of Lower Saxony