Design of Solid acid catalysts for Prins reaction and toluene methylation

1. 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

2. Thesis Chapters
1. 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. Summary
2

3. Chapter 1
Introduction
3

4.  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 energy
and 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. 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

6. 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

7. 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 Cyclization
Oxonia-Cope Prins Cyclization
Sakurai-Prins-Ritter multicomponent Reaction
Prins-pinacol reaction
Natural 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

8. 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

9. 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

10. Prins condensation
Catalyst Catalyst amount
( wt %)a
ß-pinene
conversion
( mol %)
Nopol
Yield
( 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

11. Toluene Methylation
ZSM-5 CH3
CH3OH
T=435° C
+
ZSM-5
CH3
+ +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

12. Literature survey
K. P. Wendlant, H. Bremer, Proceedings of the 8 th International Congress on Catalysis; Verlag-
chemie:Weinheim, Germany, 1998; 507.
12

13. 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

14.  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-xylene
ELUMO and EHOMO (η) is low –Soft acid –p-xylene
 As Si/Al ratio increases – the softness increases para-xylene
selectivity increases.
 Isomorphous substitution of framework aluminum in H-beta zeolite
SiAl <SiGa< SiB o-xylene selectivity due to increase of hardness.
14

15. Chapter 2
Catalyst synthesis and characterization
techniques
15

16. 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

17. Synthesis of Sn(OH)Cl
O Cl
SnSn
Cl Cl O
H
Cl
SnSn Sn
O
H
Sn
O OO
H
pH-2.5 pH-7.5
NH4OHNH4O
NH4OH
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

18. 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

19. 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

20. Chapter 3
Role of Brönsted and Lewis acid sites on Prins
cyclization over sulfated zirconia catalyst.
20

21. Introduction
 Application of anion modified metal oxides
Metal oxide – ZrO2,TiO2,SnO2,Al2O3 etc
Anion - 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

22. 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

23. XRD
Characterization-results and discussions
BET measurements
ZrO2 – monoclinic and tetragonal
SZ - Tetragonal
SZ – mesopores – H2 hysteresis
23

24. Catalyst
( sulfur
content)
Total Acidity
(mmol of
NH3/g)
Acidity
B/L ratio
Conversion
of styrene
(wt % )
Selectivity
for 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 catalysts
Py-FTIR TPD-NH3
24

25. 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 sites
Selectivity depends on the ratio of Brönsted and Lewis acid sites25

26. 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

27. Different substituted olefins
MeO
Cl
N
C6H13
3
12
3
3
10
3
3
8
3
45.1
84.6
92
6
26
0
55.2
88.7
2
Time Dioxane yield
27

28. Recycle study
Optimization of reaction conditions
28

29. Reaction mechanism
29

30. Conclusions
 The SZ showed best performance among different types of acid
catalysts.
 The selectivity for dioxane mainly depends upon the
ratio 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

31. 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

32. Chapter 4
Metal ion-exchanged zeolites as solid acid catalysts
for the synthesis of nopol from Prins reaction.
32

33. 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

34. 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

35. Characterizations-result and discussions
XRD
XRD patterns of a) zinc ion-exchanged zeolites, and b) metal ion-exchanged beta zeolites.
35

36. 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 X
0
10
20
30
40
50
60
70
80
90
100
ConversionofBeta-pinene
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

37. ZSM-5
H-MORDENITE
X and Y zeolite (FAU) H-Beta
Selectivity for nopol over different
zeolites
Y ZSM-5 MOR Beta X
0
20
40
60
80
Selectivityfornopol
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

38. 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

39. 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

40. Effect of different zinc content
Catalyst Zn
(mmol
/g)
Acidity
( mmol of
NH3/g)
Acidity
(B/L)
Conversion
of 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

41. 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

42. Optimization of reaction conditions
Catalyst
cycle
Nopol yield
(mol %)
1 85.5
2 83.7
3 81.8
4 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

43. Reaction mechanism
43

44. 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

45. Publications
45

46. Chapter 5
Acidic hydrogen bonded hydroxyl groups of Sn(OH)Cl
as catalytic active sites for the Prins reaction.
46

47. 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

48. Synthesis of Sn(OH)Cl
O Cl
SnSn
Cl Cl O
H
Cl
SnSn Sn
O
H
Sn
O OO
H
pH-2.5 pH-7.5
NH4OHNH4O
NH4OH
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

49. Characterization-result and discussions
XRD
SEM
TG-DTA
15 μm
Thin plates
arranged in
spherical particles
49

50. Catalyst phase Surface area
(m2/g)
Calcination
Temperature
(°C)
Conversion
of 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

51. Acidity and Active sites of Sn(OH)Cl
Py-FTIR FTIR
6.94 , 5.43 & 0.12 ppm
1H MAS NMR
6.43 ,5 ppm
Sn2(OH)2OSn (OH) Cl
51

52. Reactant mole ratio Catalyst amount
Reaction conditions :solvent –toluene -5ml ,temp-90°C.12 hr
53
Optimization of reaction conations

53. 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 hr
54

54. H H
O
O
SnSn
H
H H
OH
OH
H
OH
OH
H+
Cl
Reaction mechanism
55

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

56. Publications and confernces
 Posters presented “Tin (II) hydroxychloride: A Novel Solid Brønsted Acid Catalyst for Selected
Condensation Reactions” authored by Vijaykumar S. Marakatti, Ganapati V. Shanbhag, Anand
B.Halgeri in the National Workshop on Catalysis, CSIR-NEERI, Nagpur, Maharashtra
on 4-5, Feb 2014 sponsored by Catalysis Society of India.
57

57. Chapter 6
Influence of alkaline metal ion exchanged X-zeolites
on o-xylene selectivity in toluene methylation.
58

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

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) and
Y zeolite (SAR =5)
60

60. Catalytic activity over Alkaline earth metal cation
exchanged 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

61. 1440 1460 1480 1500 1520 1540 1560 1580
c
b
a
BL
Absorbance(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

62. SEM Analysis
63

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

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-X
Catalyst 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

65. Mg Ca Sr Ba
0
10
20
30
40
50
60
ConversionandSelectivity(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

66. Mg Ca Sr Ba
0
10
20
30
40
50
60
70
Conversionandselectivity(wt%) toluene
p-xylene
m-xylene
o-xylene
a)
Mg Ca Sr Ba
0
10
20
30
40
50
60
70
b)
ConversionandSelectivity(wt%)
toluene
p-xylene
m-xylene
o-xylene
Different alkylating agents
67

67. 0
5
10
15
20
25
30
Si/Al=1.5 Si/Al=2.5 Si/Al=8
0
20
40
60
80
100
Tolueneconversion(wt%)
**
*
Selelctivity(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

68. 0.0 0.5 1.0 1.5 2.0 2.5
0
2
4
6
8
10
12
14
Amount of Sr (mmol/g)
Conversionoftoluene(Wt%)
0
10
20
30
40
50
60
70
80
90
100
Selectivityforortho-xylene(Wt%)
Influence of Sr content
Reaction conditions: Tol :MeOH :4:1, WHSV =2.5 /h ,T =420°C ,N2 flow =10 ml per min , catalyst
=2 g.
69

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
Reaction conditions: Tol :MeOH :4:1, WHSV =2.5 /h ,T =420°C ,N2 flow =10 ml per min , catalyst
=2 g.
70

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

71. Publications and confernces
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

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

73. DrG.V.Shanbhag(Guide), MaterialsScienceDivision,PPISR.
Prof.A.B.Halgeri,Director, PPISR,Bangalore
 DACcommitteemembers
Prof.B.S.JaiPrakash,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,HODChemistry,BIT,Bangalore.
 Prof.B.ViswanathannandK.R.Krishnamurthy,NCCR, IITMadras.
Thanksto FacultyandFriends ofPPISR.
AdmarMuttEducationFoundation(AMEF)forthefellowshipandfacilities
75