Synthesis of ethers as oxygenated additives for the gasoline pool

253 Pages·2017·8.91 MB·English

Synthesis of ethers as oxygenated additives
for the gasoline pool

Jordi Hug Badia i Córcoles

Aquesta tesi doctoral està subjecta a la llicència Reconeixement- SenseObraDerivada 3.0.
Espanya de Creative Commons.

Esta tesis doctoral está sujeta a la licencia Reconocimiento - SinObraDerivada 3.0.
España de Creative Commons.

This doctoral thesis is licensed under the Creative Commons Attribution-NoDerivatives 3.0.
Spain License.
Programa de doctorat d’Enginyeria i Tecnologies Avançades

Synthesis of ethers as oxygenated additives
for the gasoline pool

Jordi Hug Badia i Córcoles

Directors:
Dr. Carles Fité Piquer i Dr. Roger Bringué Tomàs
Departament d’Enginyeria Química i Química Analítica, Universitat de Barcelona

Barcelona, setembre de 2016

Contents
Contents
Abstract
1. General introduction .................................................................. 1
1.1 Global energy trends .............................................................. 3
1.2 Biofuels ........................................................................... 4
1.3 Fuel ethers ........................................................................ 5
1.4 Industrial production of fuel ethers ............................................... 8
1.5 Ion-exchange resins .............................................................. 13
1.6 Catalytic activity of acidic ion-exchange resins ................................. 16
1.7 Kinetics of fuel ethers syntheses over ion-exchange resins ...................... 19
1.8 Scope of the thesis ............................................................... 23
1.9 Organization of the thesis ........................................................ 24
2. Experimental section ................................................................. 27
2.1 Chemicals ........................................................................ 29
2.2 Catalysts ......................................................................... 30
2.3 Apparatus and analysis .......................................................... 32
2.3.1 Fixed bed reactor system .................................................. 32
2.3.2 Batch reactor system ...................................................... 34
2.4 Auxiliary devices ................................................................ 35
3. Chemical equilibrium of the liquid-phase etherification of isobutene with C to
1
C linear primary alcohols ........................................................... 37
4
3.1 Introduction ...................................................................... 39
3.2 Experimental ..................................................................... 39
3.2.1 Chemicals and catalysts ................................................... 39
3.2.2 Apparatus and procedure .................................................. 40
3.2.3 Analysis ................................................................... 41
3.2.4 Calculations ............................................................... 41
3.3 Results and discussion ........................................................... 41
3.3.1 Reaction systems .......................................................... 41
3.3.2 Experimental results ...................................................... 44
3.3.2.1 MTBE synthesis .................................................. 44
3.3.2.2 ETBE synthesis ................................................... 46
3.3.2.3 PTBE synthesis ................................................... 47
3.3.2.4 BTBE synthesis ................................................... 49
i
Contents
3.3.3 Thermodynamic properties ................................................ 50
3.4 Conclusions ...................................................................... 56
4. Byproducts formation in the ethyl tert-butyl ether (ETBE) synthesis ................ 57
4.1 Introduction ...................................................................... 59
4.2 Experimental ..................................................................... 60
4.2.1 Chemicals and catalysts ................................................... 60
4.2.2 Apparatus and procedure .................................................. 61
4.2.3 Analysis ................................................................... 61
4.2.4 Calculations ............................................................... 62
4.3 Results and discussion ........................................................... 63
4.3.1 TMP-1 and TMP-2 formation ............................................. 65
4.3.2 DEE formation ............................................................ 67
4.3.3 TBA formation ............................................................ 68
4.3.4 ESBE formation ........................................................... 70
4.3.5 Catalysts comparison ...................................................... 72
4.4 Conclusions ...................................................................... 74
5. Effect of reaction media and ion-exchange resins properties on the liquid-phase
etherification of isobutene with C to C linear primary alcohols ................... 77
1 4
5.1 Introduction ...................................................................... 79
5.2 Experimental ..................................................................... 79
5.2.1 Chemicals and catalysts ................................................... 79
5.2.2 Apparatus, procedure and analysis ........................................ 80
5.2.3 Calculations ............................................................... 80
5.3 Results and discussion ........................................................... 81
5.3.1 Reaction system ........................................................... 81
5.3.2 Preliminary experiments .................................................. 82
5.3.3 Effect of the linear primary alcohol on the alkyl tert-butyl ether
syntheses .................................................................. 84
5.3.4 Relations between swollen-state morphology and catalytic activity ...... 87
5.4 Conclusions ...................................................................... 93
6. Catalytic activity and accessibility of acidic ion-exchange resins in liquid-phase
etherification reactions ............................................................... 95
6.1 Introduction ...................................................................... 97
6.2 Experimental ..................................................................... 98
ii
Contents
6.3 Results and discussion ........................................................... 98
6.3.1 Reactants molecular size and accessibility ................................ 98
6.3.2 Resins swollen-state morphology ....................................... 100
6.3.3 Relations between swollen-state morphology and catalytic activity .... 101
6.3.3.1 MTBE experiments ............................................. 102
6.3.3.2 Generalization of the empirical model .......................... 104
6.4 Conclusions .................................................................... 108
7. Simultaneous liquid-phase etherification of isobutene with ethanol and 1-butanol
over macroreticular acidic ion-exchange resins .................................... 109
7.1 Introduction .................................................................... 111
7.2 Experimental ................................................................... 111
7.2.1 Chemicals and catalysts ................................................. 111
7.2.2 Apparatus, procedure and analysis ...................................... 112
7.2.3 Calculations ............................................................. 112
7.3 Results and discussion ......................................................... 113
7.3.1 Catalyst screening ....................................................... 113
7.3.2 Effect of the initial concentration on the simultaneous etherification ... 117
7.3.3 Effect of temperature on the simultaneous etherification ............... 121
7.3.4 Comparison between simultaneous system and individual syntheses ... 124
7.4 Conclusions .................................................................... 126
8. Kinetics of the liquid-phase synthesis of alkyl tertiary butyl ethers over
AmberlystTM 35 .................................................................... 127
8.1 Introduction .................................................................... 129
8.2 Experimental ................................................................... 130
8.2.1 Chemicals and catalyst .................................................. 130
8.2.2 Apparatus, procedure and analysis ...................................... 131
8.2.2.1 Batch reactor .................................................... 131
8.2.2.2 Fixed-bed reactor ............................................... 132
8.3 Results and discussion ......................................................... 132
8.3.1 Experimental results .................................................... 132
8.3.2 Systematic kinetic modeling ............................................ 134
8.3.3 Model selection and model averaging ................................... 139
8.3.4 Fitting of the kinetic data ................................................ 141
8.3.4.1 Synthesis of PTBE .............................................. 141
8.3.4.2 Synthesis of BTBE .............................................. 146
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Contents
8.3.4.3 Simultaneous syntheses of ETBE and BTBE ................... 156
8.3.5 Comparison of kinetic equations … … ................................. 161
8.4 Conclusions .................................................................... 164
9. Summary and future lines of research .............................................. 165
9.1 Summary of the main conclusions ............................................. 167
9.1.1 Conclusions regarding the chemical equilibrium of alkyl
tert-butyl ethers syntheses .............................................. 167
9.1.2 Conclusions regarding the byproducts formation in the ETBE synthesis .. 167
9.1.3 Conclusions regarding the effect of the reaction media on reaction
rates and the relations between catalysts properties and resins
catalytic behavior ....................................................... 168
9.1.4 Conclusions regarding the isobutene etherification with ethanol and
1-butanol to produce ETBE and BTBE ................................. 169
9.1.5 Conclusions regarding the kinetics of the liquid-phase synthesis of
alkyl tert-butyl ethers over AmberlystTM 35 ............................ 169
9.2 Future lines of research ........................................................ 170
List of publications, work in progress and conference contributions ................. 171
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
I. Additional information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
II. Estimation methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
III. Estimated properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
List of tables and figures .............................................................. 203
Literature.............................................................................. 211
Resum en català ....................................................................... 219
Agraïments ............................................................................ 243
iv
Abstract
Abstract
Functionalized ion-exchange resins are polymer-based materials that can be used as
catalysts, in a wide variety of chemical reactions, to achieve highly selective formation
of desired products at cost-effective rates. Among these catalysts, sulfonic ion-exchange
resins have become critical in major industrial processes, such as the etherification of
isoolefins to obtain branched ethers.
The production of branched ethers, which are oxygenated antiknocking additives for
gasoline, became massive after the phase out of lead-based compounds in the 1990s.
Among the commercial ethers which are used nowadays, the most important ones, in
terms of their global market share, are methyl tert-butyl ether (MTBE) and ethyl tert-
butyl ether (ETBE). These ethers are industrially obtained by means of the catalytic
reaction between 2-methylpropene (isobutene) and methanol or ethanol, respectively,
over sulfonic macroreticular ion-exchange resins.
On the other hand, the use of reactants obtained from renewable feedstocks to produce
fuel components is convenient, since it allows reducing the carbon footprint of
transportation fuels in a context in which the global vehicle fleet is growing. In this
sense, the trend has been to use biomass-derived ethanol as an alternative to carbon-based
alcohols. Nevertheless, this option has generated some concerns regarding its competition
with food supplies. Alternatively, the use of other alcohols, such as 1-propanol and
1-butanol, which can also be obtained through fermentative processes, is becoming more
attractive, given that they would not compete with food supplies. Etherification of
isobutene with these alcohols would produce heavier ethers (i.e., propyl tert-butyl ether,
PTBE, and butyl tert-butyl ether, BTBE, respectively), which have potential benefits as
gasoline additives. Nowadays, this is one of the alternatives at hand to achieve an actual
improvement of the gasoline formulation in the short- midterm.
Even though the industrial-scale production of MTBE and ETBE is today widely spread,
relevant physicochemical aspects regarding ion-exchange resins have not been completely
understood. Therefore, studies aimed at providing a deeper insight into the catalytic
behavior of these materials are of interest. The present PhD thesis contains several studies
related to the catalytic performance of sulfonic macroreticular ion-exchange resins in the
liquid-phase syntheses of MTBE, ETBE, PTBE, and BTBE.
Topics included in the present thesis are related to the chemical equilibrium of the
mentioned reactions, the byproducts formation, the effect of the medium properties on the
etherification reaction rates, the relationships between catalysts properties and catalytic
activity, the simultaneous production of ETBE and BTBE, and the kinetics of some of the
studied reaction systems.

1. General introduction