vijay ppisr

Mr.Vijaykumar S Marakatti

Guide: Dr. Ganapati Shanbhag

Poornaprajna Institute of Scientific Research(PPISR)

Bangalore

Materials Science Division

Design of Solid acid catalysts for Prins reaction and toluene methylation

1

Thesis Chapters1. Introduction and literature survey

2. Catalyst synthesis and characterization techniques

3. Role of Brönsted and Lewis acid sites on the Prins cyclization over

sulfated zirconia catalyst.

4. Metal ion-exchanged zeolites as solid acid catalysts for the synthesis

of nopol from Prins reaction.

5. Acidic hydrogen bonded hydroxyl groups of Sn(OH)Cl as catalytic

active sites for the Prins reaction.

6. Influence of alkaline metal ion exchanged X-zeolites on o-xylene

selectivity in toluene methylation.

7. Summary2

Chapter 1

Introduction

3

In recent years, environmentally benign chemical processes and methodologies have received much attention from scientists, because they are essential for conservation of global ecosystem.

Most of the chemical industry processes are dependent on catalyst as its said “they are work horses of chemical industry”.

Increases the reaction rate and reduces the activation energyand Selective production routes.

In most of the industrial processes homogeneous catalysts are replaced by heterogeneous catalysts- separation, recycling and reusability

Heterogeneous catalyst for the specialty fine chemical synthesis has become a major area of research in industry and academy.

Introduction

4

5

Based on the mechanism of the reaction suitable catalyst has to be designed for the respective reaction. On the basis on the active site present on catalyst may be classified as acidic, basic, bifunctional and red-ox.

Heterogeneous acid catalysis - petrochemical industry- cracking and refinery process, which is the largest process industrially processes.

Hence , important area of research to design new catalyst or modifying the existing catalysts for acid catalyzed reactions to improve the activity and product selectivity

It is also important to study the properties of the catalysts and correlating it with the activity.

Prins reaction

Toluene methylation

Prins reaction

Hendrik Jacobus Prins, who discovered two new organic reactions, both nowadays carrying the name Prins reaction. The first one, the addition of polyhalogen compounds to olefins, was found during the doctoral research (1911-1912) of Prins, the second one, on the acid-catalyzed addition of aldehydes to olefinic compounds, became of much industrial relevance.New examples of this Prins reaction are still regularly reported

6

The Prins reaction has emerged as a powerful merged C-O and C-C bond forming technique in the synthesis various molecules

Mukaiyama Aldol-Prins CyclizationOxonia-Cope Prins Cyclization Sakurai-Prins-Ritter multicomponent ReactionPrins-pinacol reactionNatural Product Synthesis

O

H H( )n

H+ O

O

Styrene Paraformaldehyde 4-phenyl-1,3-dioxane

Prins cyclization

Industrially high boiling solvent. Plasticizer, curing agent , Pigment dispersant. Protecting group in organic synthesis.Monomer and additives in polymer industry.

Applications

7

Literature survey

Catalyst dioxane yield Yield( %)

Remarks

Sulfuric acid 75 Homogeneous

Heteropolyacids 99 Homogeneous

Trifluromethane sulfonic acid 92 Homogeneous

MoO3/SiO2 73 Heterogeneous, low conversion

SO3H-SBA-15 100 Heterogeneous R. T=120 °C- autoclave

Indium bromide Ionic liquids 91 Separation problem

Organic salt of heteropolyacids 97 Leaching problem

Zeolites 40 Lower activity

Prins cyclization

8

β- pinene

+ (HCHO)n

OH

Paraformaldehyde Nopol

90°C , toluene

Prins condensation

Nopol is optically active, primary alcohol used as aroma

in soap and detergent industries.

Nopol is also used as pesticide in agrochemical industry.

9

Prins condensation

Catalyst Catalyst amount( wt %)a

ß-pineneconversion

( mol %)

NopolYield

( mol %)

Sn-SBA-15 13 99.8 98.7

Sn-MCM-41 51 99.3 98.0

Sn-kenyaite 50 50.8 49.8

Sulfated zirconia 11 99 98.0

Na-ITQ 25 60 52.2

Zr-SBA-15 25 74 74

Zn-Montmorilionite 41 90 87.3

Fe-Zn metal cyanide 10 52 49.9

Zn-MCM-41 50 91 75.5

Literature survey

10

Toluene Methylation

ZSM-5 CH3CH3OH

T=435° C+

ZSM-5CH3

+ +T=435° C+

CH3

CH3

CH3

CH3

FRACTIONAL DISTILLATION 138°C 139°C 144°C

p-xylene m-xylene o-xylene

o-Xylene produced is starting material in the synthesis of phthalic anhydride

Selective synthesis of o-xylene over large pore zeolite - Ca-H-Y , H-beta.

THERMODYNAMIC EQUILIBRIUM 25 52 23

11

Literature survey

K. P. Wendlant, H. Bremer, Proceedings of the 8 th International Congress on Catalysis; Verlag-chemie:Weinheim, Germany, 1998; 507.

12

Increased o-xylene Selectivity

SiAl > SiAlGa >SiGa> SiB

H-Y H-beta

A. Corma, C. Zicovich-Wilson, P. Viruela, J. Phys. Org. Chem., 1994, 7, 364.

A.Corma, G. Sastre, R. Viruela, C. Zicovich-Wilson, J. Catal., 1992, 136, 521

13

Since acid hardness and softness in case of heterogeneous catalysts could not be experimentally determined;

Corma et al. applied quantum chemical methods and calculated the acid hardness and softness.

Energy difference between the ELUMO and EHOMO (η) is high-Hard acid – o-xyleneELUMO and EHOMO (η) is low –Soft acid –p-xylene

As Si/Al ratio increases – the softness increases para-xyleneselectivity increases.

Isomorphous substitution of framework aluminum in H-beta zeoliteSiAl <SiGa< SiB o-xylene selectivity due to increase of hardness.

14

Chapter 2

Catalyst synthesis and characterization techniques

15

Synthesis of sulfated zirconia

Precipitation and impregnation method

ZrOCl2 NH4OH

PH- 8

Zr(OH)4

Zr(OH)4

120°C

H2SO4

SO4-2/ Zr(OH)4

650°C

SO4-2/ZrO2

Acidity of catalyst depends sulfur content 1N,1.5N2N,3N.

16

Synthesis of Sn(OH)Cl

O Cl

SnSn

Cl Cl OH

Cl

SnSn Sn

O

H

Sn

O OOH

pH-2.5 pH-7.5

NH4OHNH4ONH4OH

Tin(II) chloride Basic Tin(II) chloride Hydrous Tin(II) oxide

T-400 ° C

Sn

O

Sn

O OO

OO Sn

T-300 ° C

17

Synthesis of Metal ion exchanged zeolites

10 gram of Zeolite + 100 ml 0.5 M metal nitrate/acetate solution

Reflux for 8 h

Filtered

Dried at 120 °C for 12 h

Calcined at 550 °C for 4 h

2nd ion exchange

Preparation of Ion exchanged zeolites.

Na+, Fe+2,Ni+2,Cu+2,Zn+2, Sr+2,Ag+ ,Cs+

18

1. X-Ray Diffractometer: Phase purity of catalysts

2. N2 Sorption: Pore size, surface area and pore volume

3.Fourier Transform Infra-red Spectroscopy: Functional groups

4.Temperature Programmed Desorption: Acid strength, no of acid sites.

5.Atomic Absorption spectroscopy: Elemental analysis

6.Scanning Electron Microscopy : Particle size and morphology

7. TG-DTA : Stability of the catalyst

8. NMR : To determine the acidity of catalysts.19

Instruments

Chapter 3

Role of Brönsted and Lewis acid sites on Prins

cyclization over sulfated zirconia catalyst.

20

Introduction Application of anion modified metal oxides

Metal oxide – ZrO2,TiO2,SnO2,Al2O3 etcAnion - MoO4

-2 , SO4-2, WO4

-2 .

Among them, sulfated zirconia catalyst attracted much attention due to its high activity in alkane isomerization at low temperatures.

Strong active sites can also be generated on zirconia by modifications of H2SO4 treatment.

H2SO4 treatment on ZrO2 support generates both Brönsted and Lewis acid sites.

Hence , it was interesting to study the role of these acid sites on the Prins reaction of Styrene with PF to form 4-phenyl-1,3 dioxane.

21

Precipitation and impregnation method

ZrOCl2 NH4OH

PH- 8

Zr(OH)4

Zr(OH)4

120°C

H2SO4

SO4-2/ Zr(OH)4

650°C

SO4-2/ZrO2

Acidity of catalyst depends sulfur content 1N,1.5N2N,3N.

Synthesis

22

XRD

Characterization-results and discussions

BET measurements

ZrO2 – monoclinic and tetragonalSZ - Tetragonal

SZ – mesopores – H2 hysteresis

23

Catalyst( sulfur

content)

Total Acidity(mmol of NH3/g)

AcidityB/L ratio

Conversion of styrene

(wt % )

Selectivityfor dioxane

(wt %)

ZrO2 --- --- 2.5 74

SZ-1N (0.92) 3.5 0.69 100 75.8

SZ-1.5N (1.12) 1.7 1.15 100 80.2

SZ-2N(1.48) 1.4 1.4 99.8 92.3

SZ-3N(1.70) 0.8 1.52 72 95

Screening of SZ catalystsPy-FTIR TPD-NH3

24

Catalyst Acidity

B/L

Conversion of

styrene

Wt%

Selectivity for

dioxane

Wt%

SO4-2/ZrO2 1.4 99.8 93

H-Beta(25) 1.92 22 88

WO3/ZrO2 1.98 96 85

Amberlyst-15 2.18 100 86

Montomorlonite-K-10 2.30 100 67

Cs3.5H0.5PW12O40 3.96 97 68

H-ZSM-5(38) 2 1 30

H-Y(16) 3.2 1 50

H-Mordenite(16) 1.4 2 46

Reaction conditions: 20 mmol styrene, 60 mmol paraformaldehyde, solvent: Dichloroethane =10ml, catalyst

weight: 7 wt% of reactants . Reaction time: 6hr. Reaction temperature: 80°C.

Screening of solid acid catalyst with SZ

Conversion depends on Total acidity - No of acid sitesSelectivity depends on the ratio of Brönsted and Lewis acid sites 25

Effect of nature of solvents

Solvent Dielectri

c

constant

Acceptor

Number

(A.N)

Donor

Number

(D.N)

Yield for

4-Phenyl-1,3

dioxane

No solvent --- --- --- 56

Cyclohexane 2.6 0 0 47

Toluene 2.4 8 0 64

1,2-dichloro ethane 10.1 16.7 0 92

Nitrobenzene 34.8 14.8 4.4 22

Acetonitrile 36 18.9 14.1 0

Tri ethyl amine 2.4 1.4 61 0

Isopropyl alcohol 18.3 33.8 21.1 0

Reaction conditions: 20 mmol styrene, 60 mmol paraformaldehyde, solvent: Dichloroethane

=10ml, catalyst weight: 7 wt% of reactants . Reaction time: 6hr. Reaction temperature: 80°C.26

Different substituted olefins

MeO

Cl

N

C6H13

312

3

310

3

38

3

45.184.6

92

626

0

55.288.7

2

Time Dioxane yield

27

Recycle study

Optimization of reaction conditions

28

Reaction mechanism

29

Conclusions

The SZ showed best performance among different types of acid catalysts.

The selectivity for dioxane mainly depends upon theratio of Brönsted and Lewis acidity (B/L), and sulfur content.

The conversion of styrene mainly depends upon the total number of acid sites and acid strength.

The presence of solvent with high acceptor and low donor number is necessary for SZ catalyst to show high activity and selectivity in Prins reaction

The catalyst was recycled thrice with negligible decrease in the yield of 4-phenyl-1,3-dioxane.

30

Publications and confernces

1. Presented the Poster entitled “Prins reaction of styrene with paraformaldehyde using

SZ as catalyst for the selective synthesis of dioxane derivative” in Indo – German

conference held at ICT, Mumbai.

2. Presented a poster “The role of Brönsted and Lewis acid sites in the selective synthesis

of dioxane from Prins reaction of styrene using sulfated zirconia” at 21st National

Symposium on Catalysis with the theme “Catalysis for Sustainable Development”, Indian

Institute of Chemical Technology (IICT), Hyderabad on Feb-11-13, 2013. 31

Chapter 4Metal ion-exchanged zeolites as solid acid catalysts

for the synthesis of nopol from Prins reaction.

32

Introduction Zeolites are crystalline micro porous aluminosilicates.

Ion-exchange has been used to introduce different metal cations into zeolites, which creates new Lewis acidic and redox properties in the zeolites.

The transition metal exchanged zeolites have been extensively studied for the various organic transformations

The ion-exchange of zinc in zeolites generates Lewis acid sites, by replacing strong Brönsted acid sites.

Zeolites and their ion-exchanged form have not been studied so far for Prins condensation reaction.

Effort is put to study the Prins reaction over different Zn+2

exchanged zeolites 33

Catalyst preparation

10 gram of Zeolite + 100 ml 0.5 M metal nitrate/acetate solution

Reflux for 8 h

Filtered

Dried at 120 °C for 12 h

Calcined at 550 °C for 4 h

2nd ion exchange

Preparation of Ion exchanged zeolites.

Na+, Fe+2,Ni+2,Cu+2,Zn+2, Sr+2,Ag+ ,Cs+

34

Characterizations-result and discussions

XRD

XRD patterns of a) zinc ion-exchanged zeolites, and b) metal ion-exchanged beta zeolites.

35

ZSM-5

H-MORDENITE

X and Y zeolite (FAU) H-Beta

2. Catalytic activity

1. Conversion over different types of zeolites

Y ZSM-5 MOR Beta X0

10

20

30

40

50

60

70

80

90

100

Co

nvers

ion

of

Beta

-pin

en

e H-zeolite

Na-zeolite

Zn-zeolite

Reaction conditions: 1.4 g = Beta-Pinene, 0.6 g = Paraformaledehyde , T=90

°C , Solvent = Benzonitrile =5 ml. Catalyst weight =0.4 g.

36

ZSM-5

H-MORDENITE

X and Y zeolite (FAU) H-Beta

Selectivity for nopol over different zeolites

Y ZSM-5 MOR Beta X0

20

40

60

80

Sele

cti

vit

y f

or

no

po

l

H-Zeolite

Na- zeolite

Zn-Zeolite

Reaction conditions: 1.4 g = Beta-Pinene, 0.6 g = Paraformaledehyde , T=90

°C , Solvent = Benzonitrile =5 ml. Catalyst weight =0.4 g.

37

Zeolite SAR

(SiO2/Al2O

3)

Amount of

Zn

(mmol/g)

Pore size

(A°)

Nopol yield

(mol %)

TON*

Zn-Na-X 3 1.58 7.4*7.4 65.7 20.8

Zn-H-Y 16 1.58 7.4*7.4*7.4 83.7 26.5

Zn-H-BEA 30 0.31 5.6 *5.6 & 7.7*6.6 85.5 138

Zn-H-ZSM-5 38 0.35 5.1*5.6 35.2 50.3

Zn-MOR 32 0.63 6.5*7 & 2.9*5.7 17.8 14.1

Different Zn2+ exchanged zeolites for the Prins reaction

12 memebered ring Zn-Y and Zn-Beta showed the good conversion and selectivity. 12 memebred Zeolite like X zeolite showed moderate yield for nopol.

10 and 8*12 memebered ring containing zeolite Zn-ZSM-5 and Zn-MOR showed least yield for nopol.

Reaction conditions: 1.4 g = Beta-Pinene, 0.6 g = Paraformaledehyde , T=90 °C , Solvent = Benzonitrile =5 ml.

Catalyst weight =0.4 g.

38

Different metal ions exchanged H-betaDifferent metal ions exchanged H-beta

Metal exchanged

zeolite-beta

Amount of metal (mmol/g)

Acidity(B/L ratio)

Yield for nopol

(mol %)

Chemical

Hardness

Zn2+ 0.31 0.13 85.5 10.8

Mn2+ 0.40 0.18 56.8 9.3

Ni2+ 0.32 0.28 48.9 8.5

Ca2+ 0.50 0.30 45.6 --

Na+ 0.78 0.54 44.4 --

Ag+ 0.013 0.65 32.9 6.9

K+ 0.23 0.87 43.4 --

Cs+ 0.12 1.26 38.2 --

Cu2+ 0.52 1.54 31.9 8.3

Fe2+ 0.35 1.75 34.8 7.3

H+ -- 2.39 36.4 --

Reaction conditions: 1.4 g = Beta-Pinene, 0.6 g = Paraformaledehyde , T=90 °C , Solvent =

Benzonitrile =5 ml. Catalyst weight =0.4 g. 39

Effect of different zinc content

Catalyst Zn(mmol

/g)

Acidity( mmol of

NH3/g)

Acidity

(B/L)

Conversionof ß-pinene

(mol %)

Selectivity(mol %)

nopol A B C D

H-beta 0 1.56 2.4 57.0 64 3.8 5.4 3.3 23.5

Zn-beta 0.14 1.62 0.45 66.6 78 2.2 3.5 2.8 13.7

Zn-beta 0.18 2.10 0.20 75.6 87 0.9 2.4 1.7 7.9

Zn-beta 0.25 2.23 0.06 91.0 92 0.6 1.6 1..0 6.8

Zn- beta 0.31 1.97 0.08 92.0 93 1.0 1.5 1.1 3.4

Zn-beta 0.57 1.75 0.1 87.0 94 1.0 1.5 1.0 3.5

ZnO -- -- -- 10.1 40 1.0 2.3 4.0 52.7

ZnCl2 -- -- -- 100 86 0.2 2.4 0.5 10.8

Reaction conditions: 1.4 g = Beta-Pinene, 0.6 g = Paraformaledehyde , T=90 °C , Benzonitrile =5 ml.

Catalyst weight =0.4 g.

A= α-pinene, B= Limonene, C= Camphene, D= Mixture of β-pinene isomerized products such as terpinenes and terpinolenes

40

Solvent Dielectr

ic

Consta

nt (DC)

Acceptor

Number

(AN)

Donor

Number

(DN)

ß-pinene

conversion

(mol %)

Product selectivity

(mol %)

Nopol A B C D

No solvent -- -- -- 100 20.0 14.4 22.1 2.6 60.9

Cyclohexane 2.0 0 0 94.0 16.0 13.3 20.5 2.1 48.1

Toluene 2.4 8.2 0 99.6 12.0 8.9 17.6 2.6 58.9

dichloroethane 10.4 16.7 0 100 8.2 4.8 14.8 2.4 69.8

Nitrobenzene 34.8 14.8 4.4 99.0 35.0 4.5 10.4 1.7 48.4

Benzonitrile 26.0 15.5 11.9 76.4 89.0 1.0 1.5 0.9 7.6

Acetonitrile 37.5 18.9 14.1 69.5 80.7 0.6 1.5 2.4 14.8

DMF 36.7 16.0 26.6 5.0 39.0 0.2 0.5 0.3 60

Triethylamine 2.4 1.4 61 0 0 0 0 0 0

Effect of Nature of solvent

A= α-pinene, B= Limonene, C= Camphene, D= Mixture of β-pinene isomerized products such as terpinenes and terpinolenes

41

Optimization of reaction conditions

Catalyst cycle

Nopol yield(mol %)

1 85.52 83.73 81.84 80.4

Reaction conditions: β-pinene = 40 mmol, PF=80 mmol, solvent = benzonitirle =20ml, Catalyst amount = 20 wt %, temp =90 °C,

time= 10 h

Catalyst recycle study

42

Reaction mechanism

43

Conclusions

Large pore zeolites like Zn-beta, Zn- X and Zn-Y exhibited high activity compared to Zn-ZSM-5 and Zn-mordenite.

Among different metal ions screened, Zn2+ showed highest activity and selectivity for Prins reaction.

As the Brönsted to Lewis acidity (B/L) ratio of metal ion-exchanged beta catalyst decreased, the yield of nopol increased indicating that Lewis acidic metal ion is the active site for Prins reaction.

Solvents like acetonitrile and benzonitrile with both acceptor and donor numbers in the range of 10 to 20 are necessary to enhance the performance of the catalyst.

The catalyst designed in the present work was prepared by non-toxic metal with environmentally friendly zeolite as its backbone and thus made synthesis of nopol, a green process.

44

Publications

45

Chapter 5

Acidic hydrogen bonded hydroxyl groups of Sn(OH)Cl

as catalytic active sites for the Prins reaction.

46

Introduction There has been an increasing interest in recent years to develop novel solid catalysts and modify them for selective synthesis of value added chemicals.

In the present work we are for the first time reporting tin(II)hydroxychloride as a solid acid catalyst and evaluating , its catalytic properties for Prins reaction, ketalization and claisen-schmidt condensation reaction.

The tin(II)hydroxychloride -mineral - abhurite , but its application was overlooked.

Insolubility in water and organic solvents generated curiosity to study its properties and application as heterogeneous catalyst.

The weak hydrogen bonded –OH groups of Sn(OH) Cl are active to catalyse the Prins reaction of ß-pinene with PF to produce selectively nopol.

Strong acid sites will lead to more side products in the reaction.47

Synthesis of Sn(OH)Cl

O Cl

SnSn

Cl Cl OH

Cl

SnSn Sn

O

H

Sn

O OOH

pH-2.5 pH-7.5

NH4OHNH4ONH4OH

Tin(II) chloride Basic Tin(II) chloride Hydrous Tin(II) oxide

T-400 ° C

Sn

O

Sn

O OO

OO Sn

T-300 ° C

48

Characterization-result and discussionsXRD

SEM

TG-DTA

15 μm

Thin plates arranged in

spherical particles

49

Catalyst phase Surface area(m2/g)

CalcinationTemperature

(°C)

Conversionof ß-pinene

(mol %)

Selectivity for nopol

(mol %)

Blank -- 0 0

Sn (OH) Cl 8 180 98 99.2

SnO2 9 400 32 94

Sn2(OH)2O 18 180 3.8 83

SnO 13 300 35 96

SnO2 16 500 33 92

Catalytic activity of tin catalysts in Prins reaction

Reaction conditions : 10mmol –beta pinene ,20mmol –paraformaldehyde , catalyst-0.23g ,solvent –toluene -5ml

,temp-90°C.12 hr 50

Acidity and Active sites of Sn(OH)ClPy-FTIR FTIR

6.94 , 5.43 & 0.12 ppm

1H MAS NMR

6.43 ,5 ppm

Sn2(OH)2OSn (OH) Cl

51

Reactant mole ratio Catalyst amount

Reaction conditions :solvent –toluene -5ml ,temp-90°C.12 hr53

Optimization of reaction conations

Leaching test

Recycle Conversion Selectivity

1 91.4 96

2 91 97

3 88 94

Recyclable test

Sn(OH)Cl a) Fresh catalyst b)after 3 recycle

Reaction conditions : 10mmol –beta pinene ,20mmol –paraformaldehyde , catalyst-0.23g ,solvent –toluene -5ml

,temp-90°C.12 hr54

H H

O

O

SnSn

H

H H

OHOH

H

OH

OH

H+

Cl

Reaction mechanism

55

Conclusions

The present study describes the synthesis, characterization and application of Sn(OH)Cl as a heterogeneous catalyst.

The characterization by FT-IR pyridine adsorption and 1H MAS NMR showed the presence of Brønsted acidity in the catalyst.

This Brønsted acidity in Sn(OH)Cl is attributed to a strong hydrogen bonding between the –OH and Cl groups

The higher activity of Sn(OH)Cl compared with Sn2(OH)2O, SnO and SnO2 is due to the presence of Brønsted acidity.

The catalyst is truly heterogeneous and can be used up to 3 recycles with minimal decrease in activity.

56


Posters presented “Tin (II) hydroxychloride: A Novel Solid Brønsted Acid Catalyst for Selected Condensation Reactions” authored by Vijaykumar S. Marakatti, Ganapati V. Shanbhag, AnandB.Halgeri in the National Workshop on Catalysis, CSIR-NEERI, Nagpur, Maharashtraon 4-5, Feb 2014 sponsored by Catalysis Society of India.

57

Chapter 6

Influence of alkaline metal ion exchanged X-zeolites

on o-xylene selectivity in toluene methylation.

58

Introduction

Shape selective catalysts, the geometric factor is a critical parameter in governing the selectivity of xylenes.

Shape selectivity is ruled out over , large pore zeolites as their pore size is much bigger than molecular dimensions of xylenes.

Only factor that could explain the change in selectivity is acid strength of zeolite.

Corma et. al have reported toluene methylation over Y zeolite with similar acid strength and have observed different selectivity for xylenes.

The concept of hard and soft acidities in zeolite has to be considered.

The influence of alkaline earth metal cation exchanged zeolites on toluene methylation and HSAB principle was correlated.

59

10 gram of Zeolite + 100 ml 0.5 M metal nitrate solution

Reflux for 8 hr

Filtered

Dried at 120 °C for 12 hr

Calcined at 550 °C for 4 hr

2nd ion exchange

Preparation of Ion exchanged zeolites.Na, Mg+2,Ca+2,Sr+2,Ba+2

Preparation of catalysts

X ( SAR=3) andY zeolite (SAR =5)

60

Catalytic activity over Alkaline earth metal cationexchanged X-Zeolites

Reaction conditions: Tol :MeOH :4:1, WHSV =2.5 /h ,T = 420°C ,N2 flow =10 ml per min , catalyst=2 g.

Why Conversion decreased ?...

Why Selectivity increased ?...

61

1440 1460 1480 1500 1520 1540 1560 1580

c

b

a

BL

Ab

so

rban

ce (

a.u

)

Wavenumber (cm-1)

a-MgX

b-CaX

c-SrX

Why Conversion decreased ?...CaX >Mg-X> Sr-X>Ba-X

Catalyst % of

ion exchange

Surface area

(m2/g)

Acidity

(mmol of NH3/g)

Brönsted

Acidity (mmol

NH3/g)

NaX -- 433 1.1 0.04

MgX 70.9 269 0.6 0.10

CaX 89.0 455 1.3 0.19

SrX 79.5 462 1.3 0.13

BaX 83.8 480 0.4 0.02

Reaction conditions: toluene: methanol =4:1, WHSV = 2.5 /h, Temperature = 420 °C, N2 flow =10 ml per min, catalyst weight =2

g, reaction time = 3 h.

62

SEM Analysis

63

Hirschler–Plank mechanism

Ca2+ Y−2 + nH2O −−−−−−> Ca(OH)+ + H+ + (n − 1)H2O + 2Y−

2Y− + Ca(OH)+ + H+ −−−→ H − Y + Ca(OH)+ + Y−

Generation of acid sites

Basic Strength

Ba-X >Sr-X > Ca-X>Mg-X 64

Soft acid sites

Hard acid sites

Concept of Hard soft acid base in catalysis

p-xylene

o-xylene

ELUMO – EHOMO = low value

ELUMO – EHOMO = high value

Mg-X

Ba-XCatalyst ELUMO – EHOMO O-xylene

Selectivity

MgX 2.009 28.9

CaX 2.147 36.2

SrX 2.155 52.4

BaX 2.157 57.7

Why o-xylene Selectivity increased ?... Mg-X <CaX < Sr-X<Ba-X

P. Mondal, K. K. Hazarika, A. Deka, R.C Deka, Molecular Simulations 34 (2008) 1121.65

Mg Ca Sr Ba0

10

20

30

40

50

60

Co

nvers

ion

an

d S

ele

cti

vit

y (

wt

%)

ethyl benzene

m-diethyl benzene

p-diethyl benzene

o-diethyl benzene

C2H5OH+

Influence of alkaline earth cation exchange of X zeolite on ethylbenzene ethylation

66

Mg Ca Sr Ba0

10

20

30

40

50

60

70

Co

nvers

ion

an

d s

ele

cti

vit

y (

wt

%)

toluene

p-xylene

m-xylene

o-xylene

a)

Mg Ca Sr Ba0

10

20

30

40

50

60

70

b)

Co

nvers

ion

an

d S

ele

cti

vit

y (

wt

%)

toluene

p-xylene

m-xylene

o-xylene

Different alkylating agents

67

0

5

10

15

20

25

30

Si/Al=1.5 Si/Al=2.5 Si/Al=80

20

40

60

80

100

To

luen

e c

on

vers

ion

(wt %

)

**

*Sele

lcti

vit

y (

wt

%)

p-xylene m-xylene o-xylene

Influence of different Si/Al

Reaction conditions: Tol :MeOH :4:1, WHSV =2.5 /h ,T =420°C ,N2 flow =10 ml per min , catalyst=2 g.

68

0.0 0.5 1.0 1.5 2.0 2.50

2

4

6

8

10

12

14

Amount of Sr (mmol/g)

Co

nvers

ion

of

tolu

en

e (

Wt%

)

0

10

20

30

40

50

60

70

80

90

100

Sele

ctiv

ity fo

r orth

o-x

yle

ne(W

t %)

Influence of Sr content


69

Catalyst Si/

Al

Amount

of Sr

mmol/g

Conversio

n

(wt %)

Selectivity (wt %)

o-

xylene

p-

xylene

m-

xylene

o+p-

xylene

Mixed

xylene

SrX 1.5 1.98 9.1 52.4 26 21.6 78.4 80

Sr-Y 2.5 1.20 15.4 32.5 33.1 34.4 65.6 69.5

Sr-beta 12 0.40 18 24.6 26 49.4 50.6 68.4

Sr-ZSM-5 19 0.24 16 15.3 36.7 48 52 74.2

H-beta 12 -- 31.3 20.8 26.4 52.7 47.2 60.5

H-ZSM-5 19 -- 39.7 23.5 23.5 52.9 47 63.9

Catalytic activity of different zeolites on toluene methylation


70

Conclusions

First time, alkaline earth cation exchanged X-zeolite is studied as an acid catalyst for ring alkylation of toluene to get xylenes

The substitution of exchangeable cations by alkaline earth metal ions was found to influence the acid hardness and softness in X-zeolite.

Experimental results further confirmed the theory of basic strength and polarizing ability of metal ions as the factors for controlling soft and hard surface sites of the catalysts.

The difference in p/o ratios observed over alkaline earth metal ion exchanged zeolite X could be explained by HSAB principle.

71


Manuscript under communication

“A PROCESS FOR THE PREPARATION OF ISOMERS OF XYLENE” invented by R. Ravishankar, P V. C. Rao, N. V. Choudary, G.V. Shanbhag, V. S. Marakatti, A. B. Halgeri, G. SriGanesh, Indian patent application number 2754/MUM/2013, PCT application

number PCT/IN2013/000651. 72

74

• Sulfated zirconia; an efficient and reusable acid catalyst for the selective synthesis of 4-phenyl-1,3-dioxane” by

Prins cyclization of styrene. Vijaykumar S. Marakatti, G. V. Shanbhag* and A. B. Halgeri, Applied Catalysis A:

General. Volume 451, 2013, 71.

• Condensation reactions assisted by acidic hydrogen bonded hydroxyl groups in solid tin(II)hydroxychloride

Vijaykumar S. Marakatti, G. V. Shanbhag* and A. B. Halgeri,

RSC Advances, Volume 3, 2013, 10795.

• Metal ion-exchanged zeolites as solid acid catalysts for the green synthesis of nopol from Prins reaction

Vijaykumar S. Marakatti, G. V. Shanbhag* and A. B. Halgeri

Catalysis Science and Technology, Volume 4, 2014, 4065.

• Influence of alkaline earth cation exchanged X-zeolites towards ortho-selectivity in alkylation of aromatics

Vijaykumar S. Marakatti, Peddy V. C. Rao, Nettem V. Choudary, Gandham SriGanesh, Sanjeev P. Maradur, A. B.

Halgeri, Ganapati V. Shanbhag* and Raman Ravishankar

(Manuscript under communication)

• Metal ion-exchanged zeolites as highly active solid acid catalysts for the green synthesis of glycerol carbonate from

glycerol Vijaykumar S. Marakatti* and A. B. Halger RSC Advances, 2015, DOI: 10.1039/C4RA16052E.

• A process for the preparation of isomers of xylene. Filed an “Indian patent” and “International Patent”

invented by Ravishankar Raman, Peddy Venkat Chalapathi Rao, Nettem venkateswarlu Choudary, Shanbhag

Ganapati, Marakatti Vijaykumar, Halgeri Anand & Gandham Sriganesh in collaboration with HPCL R&D,

Bengaluru. Patent application No. 2754/MUM/2013, PCT application No. PCT/IN20130651.

List of Publications

Dr G.V. Shanbhag(Guide) , Materials Science Division , PPISR.

Prof . A. B. Halgeri ,Director, PPISR, Bangalore

DAC committee members

Prof. B.S. Jai Prakash, Director, Institute of Environment and Hazardous

Materials Management (IEHM), Bangalore

Prof. H.N. Vasan, Principal Research Scientist

SSCU, Indian Institute of Science , Bangalore

Prof . Y. S. Bhat , HOD Chemistry , BIT, Bangalore.

Prof . B. ViswanathannandK . R. Krishnamurthy , NCCR, IIT Madras.

Thanks to Faculty and Friends of PPISR.

AdmarMutt Education Foundation (AMEF) for the fellowship and facilities75