Flow-synthesis of mesoporous silicas and their use in the preparation of magnetic catalysts for Knoevenagel condensation reactions

Abstract Mesoporous silica MCM-41 was successfully prepared by flow synthesis in a microreactor at shorter reaction times (i.e., minutes versus day) at high yield (i.e., 60% calcined sample) to give particles of more uniform size and shape compared to MCM-41 prepared by conventional batch synthesis. Magnetic iron oxide nanoparticles were incorporated and organic amines (i.e., propylamine and propyl diethylene amine) were grafted to obtain magnetic mesoporous catalysts for the Knoevenagel condensation reactions of benzaldehyde with ethyl cyanoacetate, ethyl acetoacetate and diethyl malonate. The incorporation of magnetic nanoparticles and large organic amines can hinder reactants access to the catalyst resulting in lower reactivity. NH 2 - mag MCM-41 showed superb catalyst activity and selectivity for the all three Knoevenagel condensation reactions studied. The catalyst can be easily dispersed into solution and rapidly removed by a magnet for recovery and reuse.

[1]  M. Jaroniec,et al.  Relations between pore structure parameters and their implications for characterization of MCM-41 using gas adsorption and X-ray diffraction , 1999 .

[2]  D. Brunel,et al.  New trends in the design of supported catalysts on mesoporous silicas and their applications in fine chemicals , 2002 .

[3]  M. Lindén,et al.  In Situ X-Ray Diffraction Study of the Initial Stages of Formation of MCM-41 in a Tubular Reactor. , 1998, Angewandte Chemie.

[4]  J. Santamaría,et al.  Preparation of Magnetic Nanoparticles Encapsulated by an Ultrathin Silica Shell via Transformation of Magnetic Fe-MCM-41 , 2008 .

[5]  Asterios Gavriilidis,et al.  Incorporating zeolites in microchemical systems , 2002 .

[6]  J. Čejka,et al.  Recent Advances in Catalysis Over Mesoporous Molecular Sieves , 2010 .

[7]  King Lun Yeung,et al.  Knoevenagel condensation reaction between benzaldehyde and ethyl acetoacetate in microreactor and membrane microreactor , 2008 .

[8]  K. Parida,et al.  Amine functionalized MCM-41: An active and reusable catalyst for Knoevenagel condensation reaction , 2009 .

[9]  J. Köhler,et al.  Continuous synthesis of gold nanoparticles in a microreactor. , 2005, Nano letters.

[10]  G. Mckay,et al.  Selective Adsorbents from Ordered Mesoporous Silica , 2003 .

[11]  K. Lam,et al.  Selective mesoporous adsorbents for Ag+/Cu2+ separation. , 2008, Chemical communications.

[12]  C. Kirschhock,et al.  Continuous synthesis process of hexagonal nanoplates of P6m ordered mesoporous silica. , 2011, Journal of the American Chemical Society.

[13]  Zhicheng Liu,et al.  Nanosized CaCO3 as Hard Template for Creation of Intracrystal Pores within Silicalite-1 Crystal† , 2008 .

[14]  K. Lam,et al.  Selective removal of chromium from different aqueous systems using magnetic MCM-41 nanosorbents , 2011 .

[15]  T. Welton,et al.  Precise temperature control in microfluidic devices using Joule heating of ionic liquids. , 2004, Lab on a chip.

[16]  Avelino Corma,et al.  State of the art and future challenges of zeolites as catalysts , 2003 .

[17]  R. Sheldon.  Green solvents for sustainable organic synthesis: state of the art , 2005 .

[18]  Y. Yamauchi,et al.  Rational design of mesoporous metals and related nanomaterials by a soft-template approach. , 2008, Chemistry, an Asian journal.

[19]  A. deMello.  Control and detection of chemical reactions in microfluidic systems , 2006, Nature.

[20]  T. Fujii,et al.  Acid—base catalysts derived from weakly acidic ion exchange resin: Efficiency in the Knoevenagel condensation , 1992 .

[21]  A. Gavriilidis,et al.  TS-1 oxidation of aniline to azoxybenzene in a microstructured reactor , 2005 .

[22]  M. Pera‐Titus,et al.  MCM-41 "LUS": Alumina Tubular Membranes for Metal Separation in Aqueous Solution , 2011 .

[23]  G. Chuah,et al.  Organic–inorganic hybrid catalysts for acid- and base-catalyzed reactions , 2000 .

[24]  King Lun Yeung,et al.  Experiments and modeling of membrane microreactors , 2005 .

[25]  Sau Man Lai,et al.  Knoevenagel condensation reaction in zeolite membrane microreactor , 2003 .

[26]  Andrew J deMello,et al.  Microfluidic routes to the controlled production of nanoparticles. , 2002, Chemical communications.

[27]  B. Pan,et al.  Synthesis of Highly Selective Magnetic Mesoporous Adsorbent , 2009 .

[28]  G. Whitesides.  The origins and the future of microfluidics , 2006, Nature.

[29]  Akira Taguchi,et al.  Ordered mesoporous materials in catalysis , 2005 .

[30]  G. Mckay,et al.  An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents. , 2006, Journal of Physical Chemistry B.

[31]  R. Sheldon,et al.  New developments in catalytic alcohol oxidations for fine chemicals synthesis , 2000 .

[32]  Chih-hung Chang,et al.  Convergent synthesis of polyamide dendrimer using a continuous flow microreactor , 2008 .

[33]  D. Cardoso,et al.  Influence of surfactant chain length on basic catalytic properties of Si-MCM-41 , 2007 .

[34]  R. Mokaya,et al.  Highly ordered mesoporous silicon oxynitride materials as base catalysts. , 2003, Angewandte Chemie.

[35]  G. Mckay,et al.  Efficient approach for Cd2+ and Ni2+ removal and recovery using mesoporous adsorbent with tunable selectivity. , 2007, Environmental science & technology.

[36]  A. Corma,et al.  Delaminated zeolite precursors as selective acidic catalysts , 1998, Nature.

[37]  A. Corma,et al.  Zeolites as base catalysts: Condensation of aldehydes with derivatives of malonic esters , 1990 .

[38]  Chih-hung Chang,et al.  High Rate Convergent Synthesis and Deposition of Polyamide Dendrimers using a Continuous-Flow Microreactor , 2007 .

[39]  Paul Watts,et al.  Recent advances in synthetic micro reaction technology. , 2007, Chemical communications.

[40]  Anton P. J. Middelberg,et al.  Nanoparticle synthesis in microreactors , 2011 .

[41]  K. Yeung,et al.  Knoevenagel condensation reaction in a membrane microreactor. , 2003, Chemical communications.

[42]  Xueguang Wang,et al.  Direct synthesis and catalytic applications of ordered large pore aminopropyl-functionalized SBA-15 mesoporous materials. , 2005, The journal of physical chemistry. B.

[43]  D. Brunel.  Functionalized micelle-templated silicas (MTS) and their use as catalysts for fine chemicals , 1999 .