university of twente research information 65 3.1 introduction 66 3.2 results and discussion 67 3.2.1

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    Roberto Ricciardi

  • Members of the committee:

    Chairman: Prof. dr. ir. J.W.M. Hilgenkamp (University of Twente)

    Promotor: Prof. dr. ir. J. Huskens (University of Twente)

    Assistant promotor: Dr. W. Verboom (University of Twente)

    Members: Prof. dr. J.F.J. Engbersen (University of Twente)

    Prof. dr. J.G.E. Gardeniers (University of Twente)

    Prof. dr. H. Hiemstra (University of Amsterdam)

    Prof. dr. R. Luisi (University of Bari)

    Prof. dr. ir. P. Jonkheijm (University of Twente)

    The research described in this thesis was performed within the laboratories of the Molecular Nanofabrication (MnF) group, the MESA+ institute for Nanotechnology, and the Department of Science and Technology (TNW) of the University of Twente. This research was supported by the Netherlands Organization for Scientific Research (NWO).

    Catalysis in Flow Microreactors with Wall Coatings of Acidic Polymer Brushes and Dendrimer-Encapsulated Nanoparticles

    Copyright © 2015, Roberto Ricciardi, Enschede, The Netherlands All rights reserved. No part of this thesis may be reproduced or transmitted in any form, by any means, electronic or mechanical without prior written permission of the author. ISBN: 978-90-365-3848-0

    DOI: 10.3990/1.9789036538480 Cover art: Jenny Brinkmann Printed by: Gildeprint Drukkerijen - The Netherlands






    to obtain

    the degree of doctor at the University of Twente,

    on the authority of the rector magnificus

    Prof. dr. H. Brinksma,

    on account of the decision of the graduation committee,

    to be publicly defended

    on Friday May 8, 2015 at 14.45 h


    Roberto Ricciardi Born on May 1, 1986

    in Santeramo in Colle, Bari, Italy

  • This dissertation has been approved by:

    Promotor: Prof. dr. ir. J. Huskens

    Assistant promotor: Dr. W. Verboom

  • “It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure.”

    Albert Einstein

    Alla mia famiglia, con affetto

  • Table of contents

    Chapter 1: General introduction 1

    1.1 References 5

    Chapter 2: Nanocatalysis in flow 7

    2.1 Introduction 8 2.2 Packed-bed reactors 10

    2.2.1 Hydrogenations 11 2.2.2 Cross-coupling reactions 14 2.2.3 Oxidations 16 2.2.4 Other catalytic reactions 19

    2.3 Monolithic flow-through reactors 22 2.3.1 Hydrogenations 22 2.3.2 Cross-coupling reactions 27 2.3.3 Monolith-supported alloy nanoparticles 29

    2.4 Wall-functionalized microreactors 31 2.4.1 Hydrogenations 32 2.4.2 Redox reactions 42 2.4.3 Other catalytic reactions 45

    2.5 Other approaches 47 2.5.1 Metal catalysts supported by magnetic nanoparticles 47 2.5.2 Catalytic membranes 48 2.5.3 Nanomaterial-supported catalysts 50

    2.6 Conclusions and outlook 56 2.7 References 58


  • Chapter 3: Heterogeneous acid catalysis using a perfluorosulfonic acid monolayer-functionalized microreactor


    3.1 Introduction 66 3.2 Results and discussion 67

    3.2.1 Catalytic monolayer preparation 67 3.2.2 Sulfonic acid-catalyzed reactions 69

    3.3 Conclusions 74 3.4 Experimental 75

    3.4.1 Materials and equipment 75 3.4.2 Flow apparatus 76 3.4.3 Functionalization of flat silicon dioxide surface and

    microreactor 76

    3.4.4 Catalytic studies inside the microreactor 77 3.5 Acknowledgments 78 3.6 References 78

    Chapter 4: Improved catalytic activity and stability using mixed sulfonic acid and hydroxy- bearing polymer brushes in microreactors


    4.1 Introduction 82 4.2 Results and discussion 83

    4.2.1 Flat surface and microreactor functionalization 83 4.2.2 Catalytic activity 87

    4.3 Conclusions 94 4.4 Experimental 94

    4.4.1 Materials and equipment 94 4.4.2 Flow apparatus 95 4.4.3 Polymer brush functionalization of flat silicon

    dioxide surface and microreactor 95

    4.4.4 Catalytic reactions inside the microreactor 97 4.5 Acknowledgments 97 4.6 References 98


  • Chapter 5: Dendrimer-encapsulated Pd nanoparticles for continuous-flow Suzuki-Miyaura cross-coupling reaction


    5.1 Introduction 102 5.2 Results and discussion 104

    5.2.1 Functionalization of flat surfaces and microreactor channel walls


    5.2.2 Catalytic activity 108 5.3 Conclusions 113 5.4 Experimental 114

    5.4.1 Materials and equipment 114 5.4.2 Flow apparatus 115 5.4.3 Dendrimer-encapsulated Pd NP functionalization of

    flat surfaces and microreactors 115

    5.4.4 Continuous flow Suzuki-Miyaura cross-coupling reaction


    5.5 Acknowledgments 117 5.6 References 118

    Chapter 6: Dendrimer-encapsulated Pd nanoparticles as catalysts for C-C cross-couplings in flow microreactors


    6.1 Introduction 122 6.2 Results and discussion 124

    6.2.1 Microreactor functionalization 124 6.2.2 Reaction scope of Pd DEN-microreactors 125 6.2.3 Substituent effect for the Suzuki-Miyaura cross-

    coupling reaction 128

    6.3 Conclusions 132 6.4 Experimental 133

    6.4.1 Materials and equipment 133 6.4.2 Flow apparatus 133 6.4.3 Dendrimer-encapsulated Pd NP functionalization of

    flat surfaces and microreactors 133

    6.4.4 Continuous flow Sonogashira cross-coupling reaction



  • 6.4.5 Continuous flow Mizoroki-Heck couplings 134 6.4.6 Continuous flow Suzuki-Miyaura cross-coupling

    reactions 134

    6.5 Acknowledgments 135 6.6 References 136

    Chapter 7: Influence of the Au/Ag ratio on the catalytic activity of dendrimer-encapsulated bimetallic nanoparticles in microreactors


    7.1 Introduction 140 7.2 Results and discussion 141

    7.2.1 Flat surface and microreactor functionalization 141 7.2.2 Influence of metal ratio on the catalytic reduction of

    4-nitrophenol 146

    7.3 Conclusions 152 7.4 Experimental 153

    7.4.1 Materials and equipment 153 7.4.2 Flow apparatus 153 7.4.3 Functionalization of flat silicon dioxide surfaces and

    microreactor inner walls by dendrimer-encapsulated Au/Ag alloy NPs


    7.4.5 Continuous flow reduction of 4-nitrophenol 155 7.5 Acknowledgments 155 7.6 References 156

    Summary 159

    Samenvatting 163

    Acknowledgents 165

    About the author 171


  • Chapter 1

    General introduction

    Microreactor technology associated with continuous flow processes has brought

    about a paradigm shift in the way chemical synthesis is perceived and carried

    out.1,2 The main change pertains to the equipment through which a chemical

    reaction is performed: from conventional batch scale synthesis using round-bottom

    flasks to meso- and microreactors manufactured for an intended application (Figure

    1.1).3,4 This has led to an array of new possibilities owing to the properties of

    microstructured reactors. The miniaturization of the reaction vessel (lateral

    dimensions in the order of tens to hundreds of micrometers), in fact, offers

    significant improvements in mixing, heat management, energy efficiency, safety,

    access to a wide range of reaction conditions, multistep synthesis, reduction of

    waste generation, and many more.5,6 As a consequence, continuous-flow processes

    performed in microreactors are more effective than standard batch protocols in

    facilitating the transition towards more sustainable chemical processes.7-9

    Figure 1.1 Continuous-flow microreactor (from


  • General introduction

    The development of this technology started as Lab-on-a-Chip research in the

    early 1990s with the main focus on the miniaturization of the whole reaction

    system.10,11 Nowadays microfluidic reactors are characterized by the quest to

    enable new functions and open new opportunities in chemistry, the so-called Novel

    Process Windows defined by Hessel.12 In particular, flow chemistry exerts its full

    potential in all those processes that cannot be performed with conventional

    equipment or require harsh conditions, such as dangerous chemical

    transformations, flash chemistry, multistep synthesis, and drug discovery, among


    Heterogeneous catalysis is pivotal in numerous transformations in a wide range

    of applications, especially from an industrial point of view.17 In a continuous

    process, the catalyst can be fixed within the microreactor and the reaction mixture

    can flow over it, combining reaction and separation in a single step.18 Additionally,

    the increased surface-to-volume ratio leads to improved contact between reagents

    and catalysts resulting in high catalytic activities.19


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