‘‘thesis’’ --- 2007/1/31 22:24 --- page i (#1) A CATALYSIS-ENGINEERING APPROACH TO SELECTIVE HYDROGENATION ‘‘thesis’’ --- 2007/1/31 22:24 --- page ii (#2) ii ‘‘thesis’’ --- 2007/1/31 22:24 --- page iii (#3) A CATALYSIS-ENGINEERING APPROACH TO SELECTIVE HYDROGENATION PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Delft op gezag van de Rector Magnificus prof. dr. ir. J.T. Fokkema, voorzitter van het College voor Promoties, in het openbaar te verdedigen op dinsdag 13 maart 2007 te 12:30 uur door Martinus Mathilda Pieter Zieverink scheikundig ingenieur geboren te Sittard ‘‘thesis’’ --- 2007/1/31 22:24 --- page iv (#4) Dit proefschrift is goedgekeurd door de promotoren: Prof. dr. J.A. Moulijn Prof. dr. F. Kapteijn Samenstelling promotiecommissie: Rector Magnificus voorzitter Prof. dr. J.A. Moulijn Technische Universiteit Delft, promotor Prof. dr. F. Kapteijn Technische Universiteit Delft, promotor Prof. dr. W. Buijs Technische Universiteit Delft Dr. T. Boger Corning, Inc. Dr. E. Schwab BASF A.G. Prof. dr. J.M. Winterbottom University of Birmingham Dr. ir. M.T. Kreutzer Technische Universiteit Delft Dr. ir. M.T. Kreutzer heeft als begeleider in belangrijke mate aan de totstandkoming van het proefschrift bijgedragen. This research was financially supported by BASF A.G. and Corning, Inc. c 2007 by M.M.P. Zieverink All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilised in any form or by any means, electronic or mechanical, including protocopying, recording or any information storage and retrieval system, without written permission of the author. ISBN: 978-90-5335-113-0 Keywords: Heterogeneous Catalysis / Hydrogenation / Isomerization / Edible oil ‘‘thesis’’ --- 2007/1/31 22:24 --- page v (#5) Ter nagedachtenis aan Frans Otten en Tinus Zieverink ‘‘thesis’’ --- 2007/1/31 22:24 --- page vi (#6) vi ‘‘thesis’’ --- 2007/1/31 22:24 --- page vii (#7) CONTENTS 1 Introduction 1 1.1 Catalytic hydrogenation and diffusion effects . 1 1.2 Vegetable oil hydrogenation with monolithic catalysts . 3 1.3 Engineering monolithic catalysts . 3 1.4 Thesis outline and scope . 4 2 Isomerization Reactions in the Hydrogenation of 1-Dodecene 7 2.1 Introduction and motivation . 7 2.2 Experimental . 10 2.3 Results and discussion . 13 2.4 Conclusions . 24 2.5 Nomenclature . 24 3 Diffusional Effects on Isomerization Reactions: Hydrogenation of Methyl Oleate and Derivatives 27 3.1 Introduction . 27 3.2 Previous work and literature overview . 30 3.3 Experimental . 35 3.4 Results . 39 3.5 Modelling the effects of diffusion limitations . 49 3.6 Discussion . 51 3.7 Conclusions . 56 3.8 Nomenclature . 56 4 Kinetics of the Hydrogenation and Isomerization of 1,5,9-cis,trans,trans- Cyclododecatriene 61 4.1 Introduction . 61 4.2 Previous work . 65 4.3 Experimental . 66 4.4 Results . 70 4.5 Discussion . 72 4.6 Conclusions . 87 vii ‘‘thesis’’ --- 2007/1/31 22:24 --- page viii (#8) CONTENTS 4.7 Nomenclature . 88 5 Introduction to Edible Oils and Hydrogenation Processes 91 5.1 The history of edible oil use . 91 5.2 Occurrence . 92 5.3 The chemistry of fats and oils . 92 5.4 Analysis of fats . 93 5.5 The invention of edible oil hydrogenation . 95 5.6 Hydrogenation processes . 96 5.7 Hydrogenated oil products . 97 5.8 Health issues associated with hydrogenated oil . 98 5.9 Conclusions . 100 6 Monolith Catalysts as Alternative to Slurry Systems: Hydrogenation of Ed- ible Oil 103 6.1 Introduction . 103 6.2 Experimental . 105 6.3 Results and discussion . 111 6.4 Economic evaluation of add-on unit . 119 6.5 Conclusions . 124 6.6 Nomenclature . 125 7 High(er) Performance Monoliths: Proof of Principle 131 7.1 Improving monolithic catalysts . 131 7.2 Experimental . 133 7.3 Results and discussion . 136 7.4 Conclusions . 138 7.5 Nomenclature . 138 8 Summary and Evaluation 141 8.1 Diffusion effects on hydrogenation and isomerization . 141 8.2 Concerning the use of monoliths . 145 8.3 Catalysis engineering . 146 8.4 Outlook on fat harding . 148 Samenvatting 149 Dankwoord 152 Publications and Presentations 154 Curriculum Vitae 156 viii ‘‘thesis’’ --- 2007/1/31 22:24 --- page ix (#9) ‘‘thesis’’ --- 2007/1/31 22:24 --- page x (#10) ‘‘thesis’’ --- 2007/1/31 22:24 --- page 1 (#11) Chapter 1 Introduction ’Les Chimistes forment encore un peuple distinct, tres-peu` nombreux, ayant sa langue, ses lois, ses mysteres,` & vivant presque isole´ au milieu d’un grand peuple peu curieux de son commerce n’attendant presque rien de son industrie’ Paul Henry Thiry (1723-1789) in ‘Encyclopedie,´ ou dictionnaire raisonne´ des sciences, des arts et des metiers’´ 1.1 Catalytic hydrogenation and diffusion effects The father of catalytic hydrogenation is without doubt Paul Sabatier. He was the first to recognize the formation of unstable reaction intermediaries and discovered the use of finely divided metal catalysts, in addition to the introduction of catalytic supports. For his work he was awarded the Nobel Prize in Chemistry for 1912, sharing the prize with Victor Grignard who won it for discovering the reagent later named after him. Sabatier’s work laid the foundation for industrial processes such as methanol synthesis and vegetable oil hydrogenation. At first, it was thought that hydrogenation could only take place in the vapour phase, but Wilhelm Normann’s 1903 patent made clear that fatty acids could also be hydrogenated in the liquid phase (Normann, 1903). Working in the liquid phase of course has huge advantages; reaction volumes can be much smaller and no energy needs to be expended for vaporization. It does however add a layer of complexity: instead of a gaseous hydrogen/reactant mix flowing over a catalyst, hydrogen needs to be dissolved into the liquid in such a way that hydrogen and reactant can come into contact with the catalyst surface. However, since diffusivity in a liquid is at most one hundredth of that in a gas, the existence of gradients inside a porous catalyst particle cannot be ignored anymore. At some point, the reaction rate inside the catalyst will outstrip the rate at which the products can diffuse away. The first to treat this quantitatively was Ernest Thiele in a landmark paper (Thiele, 1939). He introduced a dimensionless number, later termed the Thiele modulus, that describes the effectiveness of a catalyst particle. This Thiele modulus is the ratio of the reaction rate that would be obtained without gradients, and the diffusion rate: 1 ‘‘thesis’’ --- 2007/1/31 22:24 --- page 2 (#12) CHAPTER 1 Figure 1.1: Catalyst effectiveness as a function of a dimensionless number. Figure taken from Thiele (1939). This number was later named Thiele modulus, symbolized by φ. r r φ L (1.1) = Def f C where L is the diffusion length, Def f the effective diffusivity inside the catalyst and C the reactant concentration. For a first order reaction r kC and = s k φ L (1.2) = Def f The effectiveness of a catalyst particle can be determined for a given geometry. Thiele showed that for a slab-like catalyst, the effectiveness η can be calculated with tanh φ η (1.3) = φ Results of these calculations for different situations are illustrated in Figure 1.1 which is taken from the original paper. An extension of Thiele’s theory can also be applied to consecutive reactions A B C, where the maximum amount of intermediate B that is formed will decrease by→ an→ increase of the ratio of reaction rate/diffusion rate. The first one to recognize this was Wheeler (1951), and experimental proof of Wheeler’s the- ory was given by Weisz and Swegler (1955) for the dehydrogenation of cyclohexane to cyclohexene and benzene. Hydrogenation of carbon-carbon double bonds present in for example olefins or fatty acids can also result in isomerization of these double bonds. They can shift position 2 ‘‘thesis’’ --- 2007/1/31 22:24 --- page 3 (#13) INTRODUCTION and change conformation from cis to trans and vice versa. In this thesis, the effects of diffusion limitations are considered, not only for consecutive hydrogenations, but also on the isomerization reactions that accompany them. 1.2 Vegetable oil hydrogenation with monolithic catalysts The explosive growth of the world population in the late nineteenth century posed a serious problem; the demand for butter and associated products could not be met solely from animal sources. Although large amounts of vegetable oils were available, these did not lend themselves towards applications where solid fats where wanted. The invention of fat-hardening in the beginning of the twentieth century changed all that; it was now possible to take a liquid vegetable oil and reduce the amount of unsaturation of the fats in a way such that a solid product remained. Vegetable oil hydrogenation is a consecutive reaction; tri-unsaturated fats are hydro- genated into di-unsaturates and so on. Fats are large molecules ( 2 nm) and as a result diffusion will often dominate the hydrogenation process, resulting≈ in increased formation of the final saturated product. However, it is often desired to remove the poly-unsaturates selectively; depending on the desired properties of the product, a certain distribution of poly- and mono-unsaturates is aimed at. To some extent, hydrogenation is always accom- panied by isomerization; the double bonds that have the cis conformation in vegetable oils can be isomerized into trans double bonds. Both saturated fats and trans fats are becoming increasingly suspect because of their adverse effects on human health (Mann, 2002). The fat-’hardening’ process, consisting of mixing oil, hydrogen and slurry catalyst in large stirred tanks operated in fed-batch mode has remained largely unchanged. Continu- ous processes were developed quite early (Lush, 1923; Bolton, 1927) but have not taken root.