Desulfurization of fuels using Ionic Liquids -...

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Desulfurization of fuels using Ionic Liquids

Anabel Tabare de Oliveira

Orientador: Prof. Dr. João Coutinho Co-orientadora: Dr.ª Luciana Tomé

21 de Dezembro 2010

Universidade de AveiroDepartamento de Química

Mestrado Integrado em Engenharia Química


CONTENTS

1. INTRODUCTION1.1 Motivation and Objectives1.2 Ionic Liquids1.3 General Context1.4 Desulfurization Processes

3. MODELING2.1. COSMO-RS predictive model

5. LLE IN BINARY SYSTEMS3.1 Experimental Section3.2 Results and Discussion3.3 Conclusions

7. LLE IN TERNARY SYSTEMS4.1 Results and Discussion4.2 Conclusions

9. FINAL REMARKS

10. FUTURE WORK

2


1. INTRODUCTION

1.1 MOTIVATION AND OBJECTIVES

v Stringent governmental regulations on the sulfur content present on fuels.

v Identify the ILs with potential to be applied in the desulfurization of fuel oils.

v Experimental determination and modeling of phase diagrams of binary systems.

v Modeling of phase diagrams of ternary systems.

Test the ability of COSMO-RS to describe and predict the phase behaviour of this type of systems

3


1. INTRODUCTION

1.2 IONIC LIQUIDS

GENERAL CHARACTERISTICS

v Salts melting at temperatures below 100ºC;v Formed by the combination of large organic cations and organic or inorganic anions of variable nature; v Negligible flammability and vapour pressure; v Good ionic conductivity;v High chemical stability in a wide range of temperature; v High solvation ability;v Easiness in recovery and recycling ;v Environmental benign solvents;v Versatile solvents : By manipulating their structure, a unique set of properties can be explored for specific applications.

“Designer solvents”

4


1. INTRODUCTION

IONIC LIQUIDS APPLICATIONS

v Separation processes

v Chemical reactions

v Lubricants

v Electrolytes in fuel cells

v Solvents for the extraction of S-compounds from transportation fuels

5


1. INTRODUCTION

1.3 GENERAL CONTEXT

6

Fossil

Harmful

SOx

Environmental

Future tendency


vHydrodesulfurizationvSelective oxidationvReactive adsorptionvBiodesulfurizationvPrecipitationvAlkylation

1. INTRODUCTION

1.4 DESULFURIZATION PROCESSES

vExtractive Desulfurization with ILs

ü Carried out at mild conditions;ü Without the need for H2 and catalysts;ü Does not need drastic reaction conditions;ü Does not change the chemical structure of the fuel components.

7


2. MODELING


2. MODELING

Quantum Chemistry+ Statistical Thermodynamic

COSMO-RS Flow Chart

+ -2.1 COSMO-RS PREDICTIVE MODEL

9


( ) ( ) 2'2

'', σσασσ += effmisfit aE

( ) ( )( )HBacceptorHBdonorHBeffHB caE σσσσ −×+= ;0max;0min;0min

( )vdWvdWeffvdW aE 'ττ +=

( ) ( ) ( )( )

−−−= ∫ ')',()',('1

exp'ln σσσσσσµσσµ dEEaRT

pa

RTHBmisfitSeffS

effS

( ) ( ) σσµσµµ dp SXX

SCXS

iii ∫+= ,

2. MODELING

vdWHBmisfit EEEEenergyeraction

++=int

10

( ) ( ) ( )∑

∑==i

Xi

i

Xi

S

SS i

i

Ax

px

A

pp

σσσ'


3. LLE IN BINARY SYSTEMS



v Experimental method: turbidimetry;

v Mixtures of TP and IL were gravimetrically prepared and introduced in Pyrex-glass capillaries with a stirrer;

v Concentration range studied: 0.36<xIL<0.51;

v Three consistent measurements were carried out for each solution.

Experimental Setup

3.1 EXPERIMENTAL SECTION

12


N+

[Et3S]+

[C4m4py]+

S

O

O

S

O

O

N F3CCF3

[NTf2]-S+

Sulphonium-based IL

Pyridinium-based IL


N

N

R

R=CnH2n+1 n = 2,4,6

-S N

Imidazolium-based ILs[C2mim][SCN],[C4mim][SCN] and [C6mim][SCN]

BINARY SYSTEMS STUDIED

S-COMPOUND

S

Thiophene

Experimental / Simulated Simulated

N

N

R

R=CnH2n+1 n = 4,6

S

O

O

S

O

O

N F3CCF3

Imidazolium-based ILs[C4mim][NTf2] and [C6mim][NTf2]

13



0 0.15 0.3 0.45 0.6100

150

200

xIL

T / K

Effect of the alkyl chain length of the IL cation

BINARY SYSTEMS EXP COSMO-RS

[C4mim][NTf2]+TP ♦ ----

[C6mim][NTf2]+TP ▲ ----

3.2 RESULTS

14




0 2 4 6 8 10 12180

220

260

300

340

380

xIL

T/K

(*)Domanska, U., Królikowski, M., and Slesinska, K., Phase equilibria study of the binary systems (ionic liquid + thiophene): Desulphurization process. The Journal of Chemical Thermodynamics, 2009. 41(11): p. 1303-1311.

BINARY SYSTEMS EXP(*) COSMO-RS

[C2mim][SCN]+TP ♦ ----

[C4mim][SCN]+TP ▲ ----

[C6mim][SCN]+TP ■ ----

15



Effect of the anion family

0 2 4 6 8 10 12100

140

180

220

260

300

340

380

xIL

T / K

-0.1 -0.00 0.1 0.2 0.3 0.4 0.5100

140

180

220

260

300

340

380

xIL

T / K

BINARY SYSTEMS EXP COSMO-RS

[C4mim][NTf2]+TP ♦ ----

[C6mim][NTf2]+TP ▲ ----

[C4mim][SCN]+TP ▲ ----

[C6mim][SCN]+TP ■ ----16



3.3 CONCLUSIONS

v In general, a poor qualitative and/or quantitative agreement was found between the data predicted with COSMO-RS and the experimental data available in literature.

v COSMO-RS does not provide a good description of the LLE in binary mixtures involving TP and imidazolium [SCN]-based ILs and completely fails on the prediction of the effect of the IL anion on the phase behaviour of the (IL+TP) systems.

v Further investigation on the anion effect is needed.

17


4. LLE IN TERNARY SYSTEMS


S

O

OO

HON+

N

P-O

O-

O

P

O

OO

OH

N+

N

N+

N

-S N

N+

N

S

O

O

S

O

O

N F3CCF3

F

B

FF

F

F

B

FF

F

S

O

O

S

O

O

N F3CCF3

[C1mim][MP] [C2mim]+ [EtSO4]-

[NTf2]-

[BF4]-

[SCN]-

[NTf2]-

[BF4]-

[DEPO4]-

[C4mim]+

[C8mim]+

4. LLE in ternary systems

IONIC LIQUIDS STUDIED

Imidazolium-based ILs

Pyridinium –based IL

N+

S

O

O

S

O

O

N F3CCF3

19

[C63,5dmpy][NTf2]



S-COMPOUNDS STUDIED

S

Thiophene (TP)

S

Dibenzothiophene (DBT)

S

CH3

4-methyl-dibenzothiophene(4-MDBT)

S

CH3

CH3

4,6-dimethyl-dibenzothiophene (4,6-DMDBT)

ALKANES STUDIEDn-hexane

n-heptane

n-dodecane

n-hexadecane

cyclohexane methylcyclohexane 2,2,4-Trimethylpentane

CH3

H3CCH3

CH3

toluene

AROMATIC COMPOUND STUDIED

CH3

20


STUDIED EFFECTS TERNARY SYSTEMS

Alkanes

[C2mim][EtSO4]+TP+alkane

[C8mim][BF4]+TP+alkane

[C8mim][NTf2]+TP+alkane

[C63,5dmpy][NTf2]+TP+alkane

[C2mim][EtSO4]+pyridine+n-hexane

alkanes: n-hexane, n-heptane, n-dodecane, n-hexadecane, cyclohexane,methylcyclohexane, 2,2,4-Trimethylpentane

Cation alkyl chain length ([C2mim] or [C8mim]) [NTf2]+TP+n-heptane

([C4mim] or [C8mim]) [BF4]+TP+n-heptane

Cation family

([C63,5dmpy] or [C8mim]) [NTf2]+TP+n-heptane

([C63,5dmpy] or [C8mim])[NTf2])+TP+2,2,4-Trimethylpentane

([C63,5dmpy] or [C8mim]) [NTf2]+pyridine+n-hexane


21



STUDIED EFFECTS TERNARY SYSTEMS

Anion family

[C2mim]([EtSO4] or [NTf2])+TP+n-heptane

[C4mim]([BF4] or [SCN])+TP+n-heptane

[C8mim]([BF4] or [NTf2])+TP+n-hexane

[C8mim]([BF4] or [NTf2])+TP+n-heptane

[C8mim]([BF4] or [NTf2])+TP+cyclohexane

[C8mim]([BF4] or [NTf2])+TP+methylcyclohexane

[C8mim]([BF4] or [NTf2])+TP+2,2,4-Trimethylpentane

[C8mim]([BF4] or [NTf2])+pyridine+n-hexane

S-compounds [C2mim][EtSO4]+DBT/4-MDBT/4,6-DMDBT+n-dodecane

Aromatic compound[C2mim][EtSO4]+TP+toluene

[C8mim][BF4]+TP+toluene

Temperature [C2mim][EtSO4]+DBT/4-MDBT/4,6-DMDBT+n-dodecane22


[C2mim][EtSO4]+TP+alkane EXP COSMO-RS

n-hexane ● ---- ◑ ----

n-heptane ▲---- ⨹ ----

n-dodecane ■ ---- ◪ ----

n-hexadecane ▲---- ⨹ ----


Effect of the alkanes

4.2 RESULTS

23




Ternary system EXP COSMO-RS

[C2mim][NTf2]+TP+n-heptane ▲---- ⨹ ----

[C8mim][NTf2]+TP+n-heptane ■ ---- ◪ ----

[C4mim][BF4]+TP+n-heptane ■ ---- ◪ ----

[C8mim][BF4]+TP+n-heptane ▲---- ⨹ ----24


Effect of the cation family



[C63,5dmpy] [NTf2]+TP+n-heptane ● ---- ◑ ----

[C8mim][NTf2]+TP+n-heptane ■ ---- ◪ ----25





[C2mim][EtSO4]+TP+n-heptane ● ---- ◑ ----

[C2mim][NTf2]+TP+n-heptane ▲ ---- ⨹ ----


[C8mim][BF4]+TP+n-heptane ▲---- ⨹ ----

26






[C4mim][SCN]+TP+n-heptane ● ---- ◑ ---- 27


Effect of the S-compounds


[C2mim][EtSO4]+S-compound+n-dodecane

EXP COSMO-RS

DBT ♦ ---- ⬗ ----

4-MDBT ● ---- ◑ ----

4,6-DMDBT ■ ---- ◪ ---- 28


Effect of aromatic: toluene


Ternary systemEXP COSMO-RS

[C2mim][EtSO4]+S-compound+n-dodecane ⬥ ---- ⬗ ----

29



4.3 Conclusions

v Good COSMO-RS descriptions of the LLE of the ternary systems are obtained for low concentrations of TP.

v Better predictions of the LLE for the systems containing:üalkanes with small alkyl chains;ü short chain IL cations;üanions such as [NTf2]-, [EtSO4]- and [BF4]- .

v Worst descriptions of the LLE for [SCN]-.

v The quality of the simulations of the LLE is dependent on the type of interactions that are established between the compounds.

v The ability of the model to simulate the LLE is dependent on the particular combination of species present in the systems.

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COSMO-RS model should be used with precaution!!!!

Experimental studies on LLE in binary/ternary systems are still scarce, further investigation is

needed!!!!

COSMO-RS: POTENTIAL TOOL!!!!

5. FINAL REMARKS

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6. FUTURE WORK

v Measurement of the S-partition coefficients between Ionic Liquids and oils;

v Measurement of the solubility of the ILs in alkanes;

v Perform other experimental measurements of the LLE in (IL+TP) binary systems, concerning other type of anions and its modeling with COSMO-RS;

v Perform further experimental measurements of the LLE in ternary systems to compare with COSMO-RS predictions.

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Acknowledgments

Prof. João Coutinho Dr.a Luciana

Eng.ª Ana Rute

Grupo PATH

Ped

ro

Eng.ª Maria Jorge Dr. Bernd

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