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Liquid Phase Dehydration of 1-Butanol to Di-n-butyl ether Experimental Performance, Modeling and Simulation of Ion Exchange Resins as Catalysts

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Liquid Phase Dehydration of 1-Butanol to Di-n-butyl ether Experimental Performance, Modeling and Simulation of Ion Exchange Resins as Catalysts María Ángeles Pérez-Maciá Aquesta tesi doctoral està subjecta
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Liquid Phase Dehydration of 1-Butanol to Di-n-butyl ether Experimental Performance, Modeling and Simulation of Ion Exchange Resins as Catalysts María Ángeles Pérez-Maciá Aquesta tesi doctoral està subjecta a la llicència Reconeixement- NoComercial SenseObraDerivada 3.0. Espanya de Creative Commons. Esta tesis doctoral está sujeta a la licencia Reconocimiento - NoComercial SinObraDerivada 3.0. España de Creative Commons. This doctoral thesis is licensed under the Creative Commons Attribution-NonCommercial- NoDerivs 3.0. Spain License. Liquid Phase Dehydration of 1-Butanol to Di-n-butyl ether Experimental Performance, Modeling and Simulation of Ion Exchange Resins as Catalysts María Ángeles Pérez-Maciá Facultad de Química Departamento de Ingeniería Química LIQUID PHASE DEHYDRATION OF 1-BUTANOL TO DI-N-BUTYL ETHER. EXPERIMENTAL PERFORMANCE, MODELING AND SIMULATION OF ION-EXCHANGE RESINS AS CATALYSTS. Tesis Doctoral María de los Ángeles Pérez Maciá Dirigida por Dra. Montserrat Iborra y Dr. Roger Bringué Barcelona, 15 de septiembre de 2015 Programa de doctorado de Ingeniería y Tecnologías Avanzadas La Dra. MONTSERRAT IBORRA URIOS, profesora titular del Departamento de Ingeniería Química de la Universidad de Barcelona y el Dr. ROGER BRINGUÉ TOMÀS, profesor lector del mismo departamento, CERTIFICAN QUE: El trabajo de investigación titulado LIQUID PHASE DEHYDRATION OF 1-BUTANOL TO DI-N-BUTYL ETHER. EXPERIMENTAL PERFORMANCE, MODELING AND SIMULATION OF ION-EXCHANGE RESINS AS CATALYSTS. constituye la memoria que presenta la Ingeniera Química María de los Ángeles Pérez Maciá para aspirar al grado de Doctor por la Universidad de Barcelona. Esta tesis doctoral se ha llevado a cabo dentro del programa de Doctorado Ingeniería y Tecnologías Avanzadas en el Departamento de Ingeniería Química de la Universidad de Barcelona. Y para que así conste a los efectos oportunos, firman el presente certificado en Barcelona, 15 de septiembre de Dra. Montserrat Iborra y Dr. Roger Bringué Directores de la tesis doctoral i FOREWORD The objectives of the present thesis can be summarized in two main subjects which are clearly represented in the title of this thesis: Liquid phase dehydration of 1-butanol to di-n-butyl ether. Experimental performance, modeling and simulation of ion exchange resins as catalysts. In Chapters 1 and 2 the context of this thesis is defined and the materials and methods utilized in the subsequent chapters are introduced. The next three chapters deal with the first main objective of this thesis, Study of the liquid phase dehydration of 1-butanol to di-n-butyl ether over ion exchange resins. The performance of poly(styrene-divinylbenzene), P(S-DVB), ion exchange resins in the synthesis of di-n-butyl ether from the dehydration of 1-butanol in liquid phase is addressed in Chapter 3. This chapter also discusses the influence of typical 1-butanol impurities (isobutanol or ethanol and acetone, depending on the production route) on the dehydration process. Chapter 4 is devoted to the thermodynamic equilibrium of 1-butanol dehydration. The experimental values of the equilibrium constants for the dehydration of 1-butanol to di-n-butyl ether and for potential side reactions determined by direct measurement of the composition of the liquid mixture at equilibrium are presented. Chapter 5 is dedicated to the chemical kinetics of the dehydration of 1-butanol to di-n-butyl ether over Amberlyst 70, shedding some light on the mechanism of di-nbutyl ether formation. Furthermore, the inhibitory effect of water is investigated. The second general objective of this thesis, Modeling and simulation of ion exchange resin, has been developed in Chapters 6 and 7. Chapter 6 addresses the construction of a realistic model for P(S-DVB) networks. Furthermore, the relationship between the topology of highly crosslinked P(S-DVB) ion-exchange resins and their properties, especially the structural ones is studied by means of molecular dynamics simulations. Chapter 7 deals with the swelling of ion exchange resins in 1-butanol also by means of molecular dynamics simulations. In Chapter 8 a concise summary of the results of this thesis is presented together with suggestions for future work. Finally, at the end of this thesis an extended summary in Spanish can be found. iii OBJECTIVES (1) Check that sulfonic poly(styrene-divinylbenzene), P(S-DVB), ion exchange resins are suitable catalysts for the dehydration of 1-butanol to di-n-butyl ether,, in the liquid phase. (2) Evaluate the influence of the morphological characteristics of P(S-DVB) resins on the synthesis of and, based on these results, select the most appropriate resin for industrial use. (3) Study the influence that typical 1-butanol impurities have on the dehydration of 1-butanol. (4) Evaluate the equilibrium constant of the dehydration reaction of 1 butanol to and main side reactions. (5) Perform a kinetic study of the dehydration of 1-butanol to over the thermostable ion exchange resin Amberlyst 70 and propose a kinetic equation with mechanistical base. (6) Develop a realistic atomistic model for the crosslinked network of P(S-DVB) ion exchange resins. The model must represent the heterogeneity of the macromolecular multi-chain networks. (7) Study the influence of the polymer topology on the microscopic properties of the resin using molecular dynamic simulations. (8) Study the swelling of ion-exchange resins in 1-butanol by means of molecular dynamics simulations. v TABLE OF CONTENTS 1. INTRODUCTION Oil based economy Reformulation of diesel fuel Di-n-butyl ether () synthesis route butanol synthesis Dehydration of 1-butanol to Ion exchange resins as catalysts Role of computational chemistry in the understanding of materials properties Nomenclature References MATERIALS AND METHODOLOGY Chemicals Catalysts Experimental set up, analysis and procedure Experimental set up Analysis Procedure Computational chemistry Molecular dynamic simulations Force Fields Non-bonded interactions Temperature and pressure couplings Sorption of solvents by polymer matrices Free Energy Calculations Free Energy Perturbation theory Thermodynamic Integration Non-equilibrium method Nomenclature References... 39 vi 3. SYNTHESIS OF DI-N-BUTYL ETHER FROM 1-BUTANOL OVER ACIDIC ION EXCHANGE RESINS Introduction Materials and experimental procedure Results and discussion Reaction scheme of the catalytic dehydration of 1 butanol to Influence of resin morphology on 1-butanol conversion, initial reaction rate, selectivity to and yield Comparison with DNPE, DNHE and DNOE Thermal stability and reusability Influence of typical 1-butanol impurities Influence of 2-methyl-1-propanol (isobutanol) Influence of ethanol and acetone Conclusions Nomenclature References THERMODYNAMIC EQUILIBRIUM Introduction Experimental procedure Results and discussion Equilibrium constants Standard Gibbs free energy, enthalpy, and entropy of reactions Bimolecular dehydration of 1-butanol to Olefins isomerization Olefins hydration to 2-butanol (1-Methylpropoxy) butane formation Conclusions Nomenclature References KINETIC STUDY Introduction Experimental procedure Results and discussion Preliminary experiments Modeling of kinetic data... 92 vii Experiments starting from pure 1-butanol Experiments starting from 1-butanol/water and 1-butanol/ mixtures Modified kinetic models General kinetic models Conclusions Appendix Nomenclature References MODELING AND ATOMISTIC SIMULATIONS OF ION EXCHANGE RESINS Introduction Construction of the polymer network Homogeneous Generation Approach (HGA) Combined Growing Approach (CGA) Computational methods Results and discussion Topology-density relationship Structural properties Distribution of sulfonic groups Relative orientation of the phenyl rings Conclusions Nomenclature References BUTANOL ABSORPTION IN P(S-DVB) RESINS Introduction Methods Computational methods Experimental methods Results Thermodynamic study of 1-butanol absorption in a P(S-DVB) resin Preliminary steps Free energy perturbation. Widom s particle insertion method Thermodynamic integration Fast growth thermodynamic integration viii Thermodynamic estimation Influence of 1-butanol absorption on the macroscopic swelling Influence of 1-butanol absorption on the microscopic swelling Organization of absorbed 1-butanol Conclusions Nomenclature Reference SUMMARY AND OUTLOOK Summary: A unified view Outlook: What s next? RESUMEN DEL TRABAJO (Spanish) LIST OF PUBLICATIONS AGRADECIMIENTOS 1. INTRODUCTION 1. INTRODUCTION Oil based economy In the course of a century, technologies based on oil as a unique, easily handled fuel have shaped the world. Petroleum oil was recognized to be an essential source for illuminating oil in the 1860s followed by its use for heating and other applications including, eventually, electricity generation. It became essential for the production of transportation fuels after the introduction of internal combustion engines for cars and other vehicles, followed by planes and other means of transportation. Nowadays, oil remains the world s leading fuel supplying the 32.4% of the world primary energy consumption 1 chemical products has also gained great significance. The demand for oil continues to expand owing to a growing population and an increase in standard of living (see Figure 1.1). However, oil reserves are limited and the majority of the world s conventional oil reserves are located in the Middle East and other politically sensitive regions settings the trend for great uncertainty. The notion that the world is nearing a peak in oil supplies is a subject of great current interest and debate and, although there is much uncertainty over when oil production will peak as supplies are depleted, no one disagrees that the threat is real. Besides concerns about oil reserves limitation and the reliance on foreign and its use as a raw material for petrochemical and Source: U.S. Energy Information Administration. International Energy Statistics, April Figure 1.1. Total oil supply and total petroleum consumption resources, awareness of the importance of environmental issues (exhaust emissions, oil splits, climate change, etc.) has become more and more central to the thinking of the oil industry and regulators in the last decades. As a result, the European Union introduces increasingly stringent specifications for: million barrels per day 95 Oil Production 90 Oil Consumption Quality of petrol, diesel and gas-oil (Directive 2009/30/EC). Emissions from light passenger and commercial vehicles (Regulation EC 715/2007). Promotion of the use of energy from renewable sources, setting a mandatory 10% minimum target to be achieved by all Member States for the share of biofuels in transport petrol and diesel consumption by 2020 (Directive 2009/28/EC). 4 1. INTRODUCTION Although very efficient, diesel engines have had difficulties achieving desirable emission targets, especially for soot and NO x formation. 3 Reformulation of diesel fuel to include oxygenates has proven to be an effective way to provide satisfactory engine power and cleaner exhaust without modification of existing diesel engines Reformulation of diesel fuel A number of different oxygenates have been considered as components for diesel fuel. These oxygenates include various alcohols, ethers and esters. Alcohols have several drawbacks: high water solubility, which can cause phase separation problems; high Reid vapor pressure (RVP), which may lead to the plugging of the fuel flow by increasing the vapor pressure; high volatility, which increases the volatile organic compounds emissions; high latent heat of vaporization, which raises cold start-up and drivability issues; and low heating value. 8 Vegetable oil methyl esters have a number of properties not typical of diesel fuels such as higher boiling point, viscosity, and surface tension that may contribute to increase the NO x emissions. 9 On the contrary, ethers, especially linear monoethers, show good conditions to be added to diesel given its high cetane number, cold flow properties and mixture stability. 10 Linear ethers are also known to be effective additives to reduce diesel exhaust such as CO, particulate matter and unburned hydrocarbons and to substantially improve the trade-off between particulate and NO x due to the presence of oxygen in the ether molecules. 11 Recently, di-n-butyl ether () has been identified as an important candidate biofuel which can be produced from lignocellulosic biomass. 12, Di-n-butyl ether () presents excellent properties to be blended with diesel fuel (see Table 1.1). 14 It has a particularly high cetane number (CN) indicating short ignition delay times which at the end translates into a relatively longer combustion process and thus less unburned hydrocarbons; its moderate boiling point allows facile vaporization of the fuel after injection while minimizing the volatile organic compounds emissions during transportation, storage and refueling; and its volumetric energy content is comparable to that of petroleum fuels providing satisfactory engine power in un-modified diesel engines. Besides, can be produced from lignocellulosic biomass such as residues from agriculture, energy crops and forest refuse. This residual biomass is produced in abundance and worldwide and it has no direct competition with food, thus being an attractive, inexpensive, renewable resource for the production of next generation biofuels. 1. INTRODUCTION 5 Table 1.1. Properties of and diesel. Commercial Diesel Cetane Number Boiling point [ºC] Density [kg/m 3 ] CP a [ºC] CFPP b [ºC] Flash point [ºC] a CP (Cloud point): temperature where components form crystals and become visible forming a hazy or cloudy suspension. b CFPP (Cold filter plugging point): lowest temperature at which a given volume of fuel passes through a standardized filtration device synthesis route Linear symmetrical ethers can be produced by bimolecular dehydration of primary alcohols over acid catalysts. 15,16 Consequently, can be produced through the bimolecular dehydration of 1 butanol butanol synthesis 1-butanol can be synthesized following biological or petrochemical routes: Biological routes Biobutanol can be produced from biomass by either fermentation or thermochemical routes, as it can be seen in Figure 1.2. Currently, biobutanol is being produced on industrial scale by the ABE fermentation process in which biomass fermentation by microorganisms of the genus Clostridium gives place to 1-butanol along with acetone and ethanol. 17,18 Biobutanol can also be produced from biomass by condensation of bioethanol and/or biomethanol (Guerbet Catalysis). 19 Figure 1.2 shows that this route is still a developing technology which is not yet commercialized. 20 However, the company Abengoa developed and patented a catalyst that enables the manufacture of biobutanol competitively and, in November 2013, announced its plans to start commercial-scale production of butanol in The thermochemical routes for biobutanol production go through biomass gasification followed by syngas catalysis. 6 1. INTRODUCTION Figure Butanol biological synthesis routes (source: Carcone, ). Petrochemical route Nowadays, the most important petrochemical route on industrial scale for the synthesis of 1-butanol is based on the Oxo process which consists of selective hydroformylation and hydrogenation of linear olefins from fluid catalytic cracking in the presence of Rh and Co phosphines. 21 The reaction (see Figure 1.3) involves the addition of CO and hydrogen to the terminal double bond of propylene to yield n-butyraldehyde and iso-butyraldehyde. Subsequently, aldehydes are hydrogenated to yield 1-butanol. With this hydrogenation step 1-butanol is obtained together with 2-methyl-1-propanol (isobutanol) as byproduct. Figure Butanol petrochemical synthesis route. 1. INTRODUCTION Dehydration of 1-butanol to As it was previously mentioned, di-n-butyl ether can be synthesized through the bimolecular dehydration of 1-butanol over an acid catalyst. So far, the dehydration of alcohols has been industrially catalyzed by sulfuric acid. 22 However, environmental concerns associated with safe handling and disposal of corrosive wastes (derived from product recuperation) have encouraged the development of safer and non-waste producing alternatives for applications in catalysis. There is also a strong economic driver to use a solid catalyst instead of a liquid. The advantages of a solid include reduced equipment corrosion; ease of product separation; less potential contamination in waste streams; and recycle of the catalyst. Using a solid may also increase the number of processing options such as a gas flow reactor and a fixed bed. The selectivity may also be improved in going to a solid acid catalyst. There are some examples available in the bibliography (Table 1.2) of the utilization of heterogeneous catalyst for the dehydration of 1-butanol. Table 1.2. Published works on 1-butanol heterogeneous catalytic dehydration. Catalyst Operation conditions / Catalyst activity Reference AlPO 4 Zeolite H-ZSM-5 Amorphous aluminosilicate η alumina Niobium silicate Heteropolyacids T = 300 ºC; P =1 atm; gas phase At high conversions the major products are butenes. T = ºC; P = 1 atm; gas phase Selectivity to ether decreases remarkably with increasing conversion. T = ºC; P = 1 atm; gas phase Major products: butenes. T = ºC; P = 0 4 MPa; gas phase Selectivity is highly dependent on conversion decreasing as 1-butanol conversion increases. T = ºC; P = 1 atm; gas phase High selectivity to butenes. T = 200 ºC; P = 30 bars; liquid phase Selectivity to higher than 80% 1-butanol conversions ranging from 30 to 80% , 28 As it can be seen in Table 1.2, all the works found in the bibliography regarding the catalytic dehydration of 1-butanol report high selectivity to butenes (except works carried out in liquid phase over heteropolyacids 27,28 ). On the other hand, over the last years several works have demonstrated that acidic ion exchange resins are highly selective catalysts (97-99%) to produce linear symmetrical ethers from n-alcohols, avoiding byproducts as olefins However, to the 8 1. INTRODUCTION best of our knowledge, the synthesis of di-n-butyl ether has not been reported on ion exchangers. Thus, one of the aims of this work is to study the liquid-phase dehydration of 1-butanol to over ion exchange resins Ion exchange resins as catalysts Conventional ion exchange resins consist of a cross-linked polymer matrix with a relatively uniform distribution of ion-active sites (functional groups) throughout the polymeric structure. The polymeric matrix consists in hydrocarbon chains bonded together forming a three-dimensional hydrophobic structure, while functional groups are of hydrophilic nature. This structure makes ion exchange resins insoluble in solvents that do not break the carboncarbon bonds of the matrix. Most ion exchange resins are based on cross-linked poly(styrenedivinylbenzene) copolymers, P(S-DVB) (Figure 1.4 shows a schematic representation of P(S-DVB) resins). Other ion exchanging materials include Nafion (a perfluorinated polymer containing sulfonic acid heads) and acrylic based resins. CH CH 2 CH CH 2 CH CH 2 CH CH 2 CH CH 2 X-Y X-Y X-Y CH CH 2 CH CH 2 CH CH 2 CH CH 2 CH CH 2 X-Y X-Y X-Y CH CH 2 CH CH 2 CH CH 2 CH CH 2 CH CH 2 CH CH 2 X-Y X-Y X-Y Figure 1.4. Schematic representation of the P(S-DVB) matrix. X-Y represents a functional group. Most common functional groups are SO -H, CO -Na, NR -Cl, NH -OH All the experiments included in the present thesis were performed using P(S-DVB) resins functionalized with sulfonic acid groups. Acidic styrene divinylbenzene resins P(S-DVB) resins are commercially prepared in spherical (bead) form. A major large-scale industrial methodology for the production of P(S-DVB) resin beads is based on the suspension polymerization technique. 33 Typically, a styrene
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