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Raed Abu-Reziq

Institute of Chemistry
Faculty of Science
The Hebrew University, Jerusalem 91904, Israel
Tel: +972-2-6586097; Fax: +972-2-6585469
Email: raed.abu-reziq@mail.huji.ac.il;

Nano-catalysis

Catalysis play a central role in the chemical industry as it is reflected in the fact that more than 90 % of the industrial chemical transformations involve the use of catalysts. The importance of catalysis in not limited to the chemical industry, and it can be also applied in other areas such as energy production and environmental protection. There are two types of catalysis, homogeneous catalysis and heterogeneous catalysis. The homogeneous catalysts require mild operation conditions and they can usually offer excellent reactivity and high selectivity. However, this type of catalysts has limited application in the chemical industry due to the difficulties in their separation and recovery, which can increase the costs of their application in industrial processes. On the other hand, the heterogeneous catalysts can be separated and recovered easily but they need harsh operation conditions due to their reduced reactivity and they usually lead to less selective transformations.

In our research we develop methods to create new catalytic nano-materials that can combine the advantages of homogeneous catalysis (reactivity and selectivity) and heterogeneous catalysis (recovery and recyclability). Some of these methods involve the supporting of organometallic complexes, metal nanoparticles or organocatalysts on magnetic nanoparticles. Additional methods involve the encapsulation of homogeneous catalysts in polymeric or inorganic nanoreactors that can be magnetically separable. For example, highly selective and easily recyclable hydroformylation catalysts could be obtained by tethering rhodium complexes to magnetic nanoparticles. These new catalysts have a great potential to be applied in many industrial process.

In our attempts to develop new catalytic materials that can bridge between homogeneous catalysis and heterogeneous catalysis, we have created new catalyst that is based on encapsulation of magnetic nanoparticles together with palladium nanoparticles in polymeric nanoreactors that is produced by nano-emulsification and interfacial polymerization techniques. This catalyst is active in the hydrogenation of olefinic compounds in water as a medium for these reactions. The catalyst could be isolated easily from the reaction mixture by applying external magnetic field and it could be recycled for several runs without significant change in its activity. Figure 1 shows SEM and TEM images of such catalyst.













Figure 1. Left: SEM image of the poly urea nanoreactors containing magnetic nanoparticles and palladium nanoparticles; Right: TEM image of the polyurea nanoreactors.

In additional research we focus on preparing new catalytic materials by tethering catalysts on periodic mesoporous organosilica (PMO) nanospheres. Periodic mesoporous organosilica (PMO) materials are synthesized by sol-gel process under mild conditions and their preparation is based on the hydrolysis and condensation of bridged organo-alkoxysilane precursor compounds, (OR)3Si-R-Si(OR)3, in the presence of surfactants or block copolymers which assist to create uniform pores in the size of 2-30 nm. The surface area of PMOs can reach up to 1800 m2/g, which makes these materials attractable for catalysis applications. We have developed method for preparation PMO nanospheres that were utilized to support chiral ruthenium catalysts. These catalysts were highly enantioselective in hydrogenation of ketones and could be recycled for several runs without significant decrease in their activity or enantioselectivity. Figure 2 shows SEM image of PMO nanospheres. Currently, we create chiral PMO nanospheres by polymerization of chiral bridging silane monomers and we investigate the effect of these chiral nanospheres on different asymmetric organic transformations.













Figure 2. SEM image of PMO nanospheres, scale bar is 200 nm.

In addition, we have developed a method for the encapsulation of catalysts in solid lipid microparticles (SLM). The catalysts are functionalized with long chain alkyl groups in order to facilitate their immobilization in the lipid particles that can be prepared by hot emulsification technique and then solidification the lipid droplets by quenching with ice. The encapsulated catalysts showed high activity in hydrogenation reaction using water as medium for these reactions. Figure 3 shows SEM image of the catalytic lipid microparticles.













Figure 3. Catalytic solid lipid microparticles. Left: scale bar 100 um, right: scale bar 10 um.

Specific research topics related to Nanoscience and Nanotechnology:

  • Magnetically separable ionic liquid-based nanoreactors
  • Catalytic periodic mesoporous organosilica nanospheres
  • Catalytic solid lipid microparticles
  • Development of methods for microencapsulation based on sol-gel chemistry
  • Publications in Nanoscience and Nanotechnology (2011-2012):

    Magnetically separable base catalysts: heterogeneous vs. quasi-homogeneous catalysis. R. Abu-Reziq and H. Alper, Appl. Sci. 2012, 2, 260-276.

    Five most significant publications in the last five years:

    R. Abu-Reziq, H. Alper, D. Wang and M. L. Post, "Metal Supported on Dendronized Magnetic Nanoparticles: Highly Selective Hydroformylation Catalysts", J. Am. Chem. Soc. 128, 5279-5282 (2006).

    R. Abu-Reziq, D. Wang, M. L. Post and H. Alper, "Platinum Nanoparticles Supported on Ionic Liquid-Modified Magnetic Nanoparticles: Selective Hydrogenation Catalysts", Adv. Synth. Catal. 349, 2145-2150 (2007)

    Separable Catalysts in One-Pot Synthesis for Greener Chemistry. R. Abu-Reziq, D. Wang, M. L. Post and H. Alper, Chem. Mater. 2008, 20, 2544-2550.

    Y. Itzik, R. Abu-Reziq and D. Avnir, "Entrapment of an Organometallic Complex within a Metal: A Concept for Heterogeneous Catalysis", J. Am. Chem. Soc.  130, 11880-11882 (2008).

    A Three-Phase Emulsion/Solid Heterogenization Method for Transport and Catalysis. R. Abu-Reziq, D. Avnir and J. Blum, Angew. Chem. Int. Ed. Eng. 2002, 41, 4132-4134.

    Patents (2009-2011)

    • O. Toledano, H. Sertchook, N. Loboda, R. Abu-Reziq: "Microcapsules comprising active ingredients and a metal oxide shell, a method for their preparation and uses thereof " PCT Int. Appl.  (2010), WO 2010013250
    • 1. D. Avnir, R. Abu-Reziq, R. Ben Knaz, I. Yosef, G. Nesher, G. Marom, Enzyme entrapment within metal matrix for use in the construction of enzymic biosensors. US Pat Appl. (2010), US 20100297724.

    Cooperation with industries and defense projects (2011-2012):

    • Cooperation with Sol-Gel Technologies (Ness-Ziona)

    Cooperation with other researchers/universities in israel:

    • Prof. Shlomo Magdassi, Prof. Avi Bino (within the Hebrew university)

    Research grants

    • 2012 (1 year): Ministry of Agriculture and Rural Development, "Development of environmental-friendly sol-gel formulation for simultaneous slow-release of several pheromones"
    • 2012 (1 year): German-Israeli Foundation for Scientific Research and Development, Young Scientists Program, "Chiral polymeric nanocapsules and their application in organocatalytic transformations"
    • 2012-2013: Niedersachsen Research Cooperation Program, "Bridging between homogeneous and heterogeneous catalysis: catalytic silica nanocapsules combined with continuous flow microreactors"
    • 2008-2013: Sol-Gel Technology, funding a research for developing microencapsulation methods.

    Students, postdocs and researchers:

    Staff scientist: Dr. Gilat Nizri and Dr. Saleh Abu-Lafi
    Junior scientists/post-docs: Dr. Bishnu Dutta
    Ph.D. students: Esti Weiss, Suzana Natour, Suheir Omar
    M.Sc. students: Yafit Schnell, Amani Zoabi, Ahmad Zarour, Sumaya Abu-Ghannam


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