Mervin thesis final

Project Report
SYNTHESIS OF Zn IMPREGNATED ZSM-5 CATALYST FOR
THE DIRECT CONVERSION OF n-BUTANE TO ISO-OCTANE
Under the Guidance of
Mr. Rajeshwar Mahajan
Dept. of Chemical Engineering
Submitted by,
MERVIN J
R670211020/500017986
M.Tech - Process Design Engineering
UPES, Dehradun
April, 2013

i
SYNTHESIS OF Zn IMPREGNATED ZSM-5 CATALYST FOR
THE DIRECT CONVERSION OF n-BUTANE TO ISO-OCTANE
A thesis submitted in partial fulfillment of the requirements for the Degree of
Master of Technology
(Process Design Engineering)
By
(MERVIN J)
Under the guidance of
Assistant Professor
Dept. of Chemical Engineering
Approved
Dean
College of Engineering
University of Petroleum & Energy Studies
Dehradun
April, 2013

ii
CERTIFICATE
THE UNIVERSITY OF PETROLEUM AND ENERGY STUDIES
FACULTY OF ENGINEERING
The undersigned certify that they have read, and recommend to the Faculty of Engineering for
acceptance, a thesis entitled “ Synthesis of Zn impregnated ZSM-5 catalyst for the direct
conversion of n-Butane to Isooctane” submitted by Mervin J in partial fulfillment of the
requirements for the degree of M. Tech in Process Design Engineering.
________________
Assistant professor
Department of Chemical Engineering
________________
Dr. Ashutosh Panday
Head of the Department
Department of Chemical Engineering
Date______

iii
ACKNOWLEDGEMENT
I sincerely thank Dr. Ashutosh Pandey, Head of the Department, for his priceless motivations
which has inspired me to contribute the best of mine towards my project.
I would like to thank my mentor Mr. Rajeshwar Mahajan, assistant professor who has guided me
throughout my project inspite of his busy schedule and made it possible to deliver a quality
work. Without his esteemed guidance it is impossible to think where I stand today. As a learner I
came to know about latest advancements in the field of process engineering from him. Working
with him gave me a world class exposure. And I feel it is a life time opportunity to work with
him. I learned to be a positive person which is an essential aspect for one’s life.
I would also like to thank Dr. R.P. Badoni for giving me an opportunity to perform my
experiments in the catalyst development lab and the catalyst characterization lab. I feel very
proud to mention his name in my acknowledgements. His knowledge in the current field has
helped to drive myself in an efficient path.
I would specially thank Dr. G. Gopala Krishnan for his invaluable guidance and his constant
support throughout. It is my pleasure in having his in motivational support and encouragement.
I would also like to acknowledge with much appreciation the role of all faculties who taught
subjects which were the foundation for these works. I would like to thank with sincere gratitude
to Dr. Surbhi Semwal for her help in completion of my experimental work.
I am very thankful to Ms. Remya for helping me by encouraging and advising for the completion
of project. I also thank Mr. Amit Kumar for helping me in conducting experiment trails.
It is not possible to complete my acknowledgements without thanking Dr. Vishal Misra. He is
the person who made me to stand in front of the competitive world.
I would like to express my thanks to all my friends who gave me the possibility to complete this
report. Even though many senior members supported me through all my tough times my friends
especially my roommates, helped me through out my journey by adding extra sugar to my
dessert.
Mervin J
M.Tech - Process Design Engineering

iv
LIST OF FIGURES
Figure 3.1.1 Effect of reaction temperature on the non-catalytic oxidative dehydrogenation of n-butane.
......................................................................................................................................................................9
Figure 3.1.2 Effect of reaction temperature on the oxidative dehydrogenation of n-butane over
Mg3(VO4)2/MgO...........................................................................................................................................10
Figure 3.1.3 Dehydrogenation activity of Zn(imp)/K-ZSM-5 as a function of TOS......................................12
Figure 3.1.4 Feed conversion of different catalysts at WHSV = 6h-1. ........................................................14
Figure 3.1.1 Propene selectivity of different catalysts at WHSV = 0. 6h-1.................................................15
Figure 3.2.1 Conversion of Isobutene to Isooctene by dimerization..........................................................16
Figure 3.2.2 Commercial dimerization plant...............................................................................................17
Figure 3.2.3. Developed dimerization process ...........................................................................................19
Figure 3.2.1. Influence of operating pressure on conversion,....................................................................22
Figure 3.2.2 Influence of reaction temperature on isobutene dimers selectivity......................................23
Figure 3.2.3 Variation of Nickel load over catalysts HY-Zeolite..................................................................24
Figure 3.2.4 Conversion as function of particle size, catalyst HY-Zeolite with 9% of Nickel load catalyst. 25

v
LIST OF TABLES
Table 1.1 Consumption of MTBE ..................................................................................................................3
Table 3.1 BET surface area of the catalysts used........................................................................................13
Table 0.1 Si/Al ration and acidity (mmol/g) of the zeolite frameworks. ....................................................20
Table 0.2 Total pore volume and avg. pore diameter of the impregnated zeolite frameworks with
different Nickel precursor salts...................................................................................................................21
Table 4.1 Proportion of sample ..................................................................................................................26
Table 4.2 BET surface area (m2
/g) and Langmuir surface area (m2
/g) of the calcined zeolite frameworks.
....................................................................................................................................................................30
Table 4.3 Total pore volume (cm3
/g), micro pore volume (cm3
/g) and acidity (mmol/g) of the calcined
zeolite frameworks. ....................................................................................................................................30
Table 4.4 Amount of EDTA consumed for extrudate of sample 2. ............................................................33
Table 4.5 Amount of EDTA consumed for extrudate of sample 3..............................................................33
Table 4.6 Ph and Molarity of the respective Ion exchange. .......................................................................34
Table 5.1 Comparison of Total acidty before and after Zn impregnation. .................................................34

vi
Contents
Certificate...................................................................................................................................................... ii
Acknowledgement....................................................................................................................................... iii
List of figures................................................................................................................................................ iv
List of tables.................................................................................................................................................. v
Nomenclature............................................................................................................................................. vii
Summary.................................................................................................................................................... viii
1. Introduction ......................................................................................................................................1
1.1. Reaction paths ..........................................................................................................................1
1.2. Background of catalysts............................................................................................................2
2. Catalyst development.......................................................................................................................4
2.1. Zeolites......................................................................................................................................4
2.2. Zeolite framework.....................................................................................................................5
2.3. ZSM-5 ........................................................................................................................................5
3. Literature survey...............................................................................................................................6
3.1. Dehydrogenation of alkanes.....................................................................................................6
3.2. Dimerization of alkenes ..........................................................................................................16
4. Experimental methods....................................................................................................................26
4.1. Objectives................................................................................................................................26
4.2. Methodology...........................................................................................................................26
4.3. Temperature programmed desorption...................................................................................29
4.4. Impregnation of extrudates with Zn.......................................................................................31
5. Result and conclusion .....................................................................................................................34
6. Future study....................................................................................................................................35
Bibliography ................................................................................................................................................36

vii
NOMENCLATURE
Symbol Definition Unit
M1 Molarity of the filtrate No. of moles/ liter of solution
M2 Molarity of the EDTA solution No. of moles/ liter of solution
V1 Volume of the filtrate mL
V2 Volume of EDTA solution mL
Selectivity %
Conversion %
Yield Mass. %
Temperature ◦
C
TOS Min, hr
BET surface area m2
/g
Langmuir surface area m2
/g
Acidity mmol/g
T Temperature °C
WHSV Weight hourly space velocity h-1
Total pore volume cc/g
Micro pore volume cc/g
Avg. Pore diameter Å
Flow rate mL/h
Pressure Psig
Particle size mm

viii
SUMMARY
The main objective is to prepare a catalyst which can efficiently support simultaneous
dehydrogenation of n-butane and dimerization of butenes to give isooctenes and hydrogenation
of octenes to obtain isooctane as product. A catalyst is made using 10 membered ring ZSM-5 and
zinc is impregnated over the catalyst support surface. The impregnation of zinc is done by ion
exchange method, where zinc nitrate hexa hydrate is used as a medium to impregnate. The
sodium ion in the ZSM-5 is replaced by zinc and ammonium ion, from zinc nitrate hexa hydrate
and ammonium chloride respectively. After the ion exchange, the complex is calcined at 500◦
C
where ammonium ions are replaced by protons to increase the bronsted acid sites further. The
hydrogen ions thus contribute to the formation of carbonium ions.

1
CHAPTER 1
1. INTRODUCTION
The world today requires fuel with high efficiency, one way to improve the efficiency of the fuel
is to increase its octane number. Higher the octane number more is the knocking resistance of the
fuel. The recent technologies have made it possible to increase the octane number in an
environment friendly manner. The isooctane is used as a major additive to increase the octane
number of gasoline, which can be obtained from its precursor n-butane. The commercial
production of isooctane is done in petroleum distillation process. Isooctane is used as a raw
material to produce alkyl phenol and isononanic acid.
1.1. REACTION PATHS
There are two reaction paths to obtain isooctane using n-butane as the feedstock.
One is the alkylation process, in which the reaction path follows dehydrogenation of n-butanes to
butenes and its subsequent alkylation with remaining butanes to isooctanes.
Second is the dimerization process, in which butanes are dehydrogenated to butenes followed by
dimerization of butenes to isooctenes and the isooctenes are hydrogenated to yield isooctane.
Both the reaction path involves initiation, propagation and termination steps. The initiation step
in both the reaction path involves the formation of tertiary carbonium ion by the protonation of
butene involving bronsted acid sites. The propagation step in the both the reaction paths involves
the addition of butene to the carbonium ion to form dimeric and oligomeric carbocations. The
termination step in the alkylation reaction path, involves a hydride transfer from isobutane to
carbonium ion to form isoalkenes (2, 4, 4 Trimethyl-2-pentene, 2, 4, 4 Trimethyl-1-pentene) and
tertiary carbonium ion which carries the cycle. The termination step in the dimerization reaction
path, due to the absence of isobutene the carbocation undergoes termination by chain transfer,
thereby releasing the proton which carries the cycle by reacting with another butene and gives
isoalkenes as a product. Selectivity of the dimerization reaction and restricting the oligomers
formed within the allowable gasoline range can be done by optimizing the parameters such as,
WHSV, temperature, composition of feed, catalyst configuration.

2
1.2. BACKGROUND OF CATALYSTS
During the start of the age of industrialization a lot of researches have been done in order to
improve the octane number by trying with various additives. Each additive tend to have an effect
over the environment.
At the very beginning in 1923, the most effective anti-knock agents used were tetraethyl lead or
TEL. By the mid of 1970’s due to the lead poisoning, the use of tetraethyl lead is suppresses. By
1995 it is completely banned in continental US and some of the European countries.
In 1959, manganese based anti-knock agent methylcyclopentadienyl manganese tricarbonyl or
MMT was used. During combustion the manganese present in MMT tends to form manganese
compounds, which settles on spark plugs and combustion chamber. The rest of the compounds
are released into the atmosphere causing air pollution.

3
In 1970, methyl tertiary butyl ether or MTBE has been found as an alternative fuel additive,
mainly for the advantage of phasing out lead. Since 1980’s due to the increase in demand for
premium gasoline, MTBE had remained as a dominant gasoline additive to enhance the octane
number.
Table 1.1 Consumption of MTBE
Year Usage of MTBE (Barrels per day)
1990 83,000
1994 161,000
1997 269,000
The main disadvantage of MTBE is that it is water soluble and do retain in water for long time.
In 2003, US had started using ethanol as an alternative to MTBE as the farmers and agricultural
groups found it to be a safe alternative. But ethanol was found to be affecting the air quality by
causing photochemical smog and the water quality in terms of health oriented problems. A much
safer alternative was found to ETBE, due to the fact that it does not cause smog and its inability
to absorb atmosphere’s moisture. Since ETBE is commercially considered to be expensive, it’s
usage as an anti-knocking agent and oxygenate was not an option. In the recent years isooctane is
found out to be a much more efficient and safer substitute as an anti-knocking agent and also a
better oxygenate used so far. Some of the anti-knocking agents which is in use in the present day
are,
 Tetraethyl lead (TEL)
 Methylcyclopentadienyl manganese tricarbonyl (MMT)
 Ferrocene
 Toluene
 Isooctane

4
CHAPTER 2
2. CATALYST DEVELOPMENT
The catalyst developed must support dehydrogenation and hydrogenation reactions as well as
alkylation and dimerization reactions. Dehydrogenation of alkanes requires relatively a high
temperature range and low pressure for the reaction to take place, whereas dimerization of
alkenes requires a low temperature range for effective dimerization. The catalyst chosen must
remain stable and catalyze the reactions at the specified temperature ranges and also the high
temperature range must not lead to the thermal cracking of coke and other lighter alkanes.
2.1. ZEOLITES
In 1756, Axel Fredrik Cronstedt a Swedish mineralogist, found that the mineral stilbite upon
rapidly heating generated steam in large quantity. The steam was formed due to the water that
had been absorbed by the mineral. He named this mineral as zeolite, from Greek terminology
where zein means - to boil and lithos means - stone.
In the present day the usage of zeolites are in the scale of million tons per annum. A vast portion
of zeolites are used in petrochemical industry mainly as a catalyst for isomerization, dimerization
and cracking of hydrocarbons.
Zeolites are also utilized for domestic purposes such as softening and purification of water by
ion exchange method and in laboratories they are been used to remove gases and solvents. They
are also being used in the field of construction, agriculture and animal husbandry. Each and
every aspect of zeolites applications is concerned about clean and safe environment.
Zeolites are micro porous materials with a well-defined crystalline structure. They exist naturally
as minerals and some of the zeolite framework is synthesized by researchers all over the world
because of the unique properties showcased by the zeolite framework. Their framework
comprises of aluminium, silicon and oxygen. Water is trapped within the pores along with
cations and molecules. In the case of ZSM-5 catalyst sodium molecules are present inside the
pores.

5
2.2. ZEOLITE FRAMEWORK
Zeolite framework structure is formed by a connected group of oxygen atoms with silicon atom
in the middle, to form a tetrahedral frame. The corners of each tetrahedral frame then can be
linked to form the complete framework of the zeolites. A variety of different types of framework
can be synthesized by rearranging the tetrahedral frames. Until now 130 different zeolite
frameworks had been synthesized. Within the framework linked cavities, channels and cages can
be allowed, which determines the pore size of the zeolite. The pore size can be varied in the
range of 3 to 10 A in diameter. One can synthesize a framework of specific pore size and pore
volume according to their need. E.g. Framework of pore size exist such that, ammonia gas is
separated from air.
Even the tetrahedral atom can be replaced so as to obtain a different frame, by replacing the
usual silicon or aluminium atom with the other atoms such as, boron, gallium, germanium,
beryllium, arsenic, aluminophosphates or ALPO’s.
2.3. ZSM-5
ZSM-5 is abbreviated as Zeolite socony mobil. In 1975 it is synthesized and a patent was made
by mobil Oil Company. Its framework is based on alumino silicate. ZSM-5 comprises of sodium,
aluminium, silicon, oxygen and water. The chemical formula is given as NanAlnSi96-
nO192.16H2O. A major usage is found in the petroleum industry as a heterogeneous catalyst to
catalyze dimerization and isomerization reactions.

6
CHAPTER 3
3. LITERATURE SURVEY
3.1. DEHYDROGENATION OF ALKANES
CnH2n+2 → CnH2n+2 + H2 [1]
The dehydrogenation of alkanes requires a higher temperature and relatively low pressure. It is
been done on a large scale simply due the fact that it requires a less capital and also due to its
efficiency in converting the low cost precursors to their corresponding alkenes. Some of the
well-known processes in alkene production include the CATOFIN, the UOP and the
SNAMPROGETTI- YARSINTEZ. [1]
The drawbacks for conversion of alkenes from alkanes as a continuous process in industries
includes,
 Supplying enough heat to the reactor.
 Maintaining temperature to avoid any degradation products and also the conversion must
be at maximum.
 Regenerating catalysts.
This section includes the literature of commercially used catalysts to obtain alkenes from
alkanes by dehydrogenation process.
Dehydrogenation requires a low temperature for alkanes of longer chains whereas lighter
alkanes require relatively higher dehydrogenation temperatures. [6] The lowering of pressure and
addition of diluents can be done to increase the conversion of alkanes. Dehydrogenation
temperatures to obtain equilibrium conversion of 90 % for ethane and hexane to their
corresponding alkenes (ethene and 1-hexene) are 900 ◦
C and 730 ◦
C respectively. [1]
The reactions are not selective because all C-H bonds possess the same bonding energy and
hence all have an equal chance of reacting, which leads to dehydrocyclisation and aromatization
if non neighboring C-H bond tends to undergo dehydrogenation. [1] Aromatization occurs if the

7
alkanes consist of six carbons in their chains. When C-H bonds reacting are from two alkane
molecules, long chained hydrocarbons are formed. If the reactions are unselective the formation
of hydrogen gas and coke formed will be in large, due to unwanted C-H and C-C bond
formation. The coke deposited over the catalyst tends to produce more hydrogen than alkenes
overall. Hence regeneration of catalyst must be done in order to expose more acid sites, so that
selectivity is improved resulting in the conversion of alkanes to alkenes. [1]
The dehydrogenation of alkanes can be done in two paths, oxidative dehydrogenation and non-
oxidative dehydrogenation. [1] The most seeked path is the oxidative dehydrogenation due to the
fact that it offers less limitation thermodynamically. [5] And also oxidative dehydrogenation is
more selective towards alkanes and does not tend to form combustion products and aldehydes or
acids, when compared to non-oxidative dehydrogenation.
The selectivity depends on streaming time. Initially selectivity towards alkenes are very low
hence CO, CO2 are formed. After the induction time, the selectivity towards alkenes increases
up to 90 %. [1]
3.1.1. CHROMIUM OXIDE CATALYST
Alkane dehydrogenation to obtain propene and isobutene with the help of chromium oxide
catalysts in the absence of oxygen is a process of commercial interest. This paper deals with the
usage Cr/Al2O3 catalyst in the commercial production of isobutene and propene. [1]
3.1.1.1. CATALYST PREPARATION
Wet incipient impregnation method is utilized to prepare chromium oxide catalyst on porous
alumina with high surface area using aqueous solution containing chromium (VI) trioxide or
chromium (III) nitrate. K2CrO4 aqueous solution is used, if dopant is required. [1]
3.1.1.2. CATALYTIC CHARACTERIZATION
The dehydrogenation activity is based on Cr loading (in Wt. %) over catalyst, reaction
temperature and streaming time. Initially the activity increases linearly with the Cr loading, but
when the Cr loading is in the range of 4 - 10 % the level of activity remains constant or even
deteriorates.

8
The longer the time of streaming, lower would be the dehydrogenation activity. This is due to the
formation of coke. Also the activity depends upon the number of regeneration- dehydrogenation
cycles. The lifecycle of the catalyst can be increased by increasing the temperature as the time on
stream is increased. [1]
From this paper we conclude that at initial, the dehydrogenation activity increases linearly and
the level of activity remains constant or even detoriates when the Cr loading is in the range of 4 -
10 %. The lifecycle of the catalyst can be increased by increasing the temperature as the time on
stream is increased.
3.1.2. VANADIUM MAGNESIUM OXIDE CATALYST
In this paper the conversion of butene and butadiene from butane is obtained by oxidative
dehydrogenation with MgO supported magnesium vanadate as catalyst. For a better selectivity
orthovanadate phase is been used. A detailed study had been made on catalytic and non-catalytic
dehydrogenation of alkanes in terms of temperature and selectivity. [3]
Catalyst preparation
The catalytic characterization is studied after the following steps been done,
 Impregnation of MgO powder in varying amounts in a solution consisting of 1 Wt. % of
ammonium vanadate and 0.5 Wt. % of ammonium hydroxide is done and evaporated
until a paste is formed. [3]
 The paste obtained is dried at 120 ◦
C for 18 hrs.
 Calcination of the paste is done at 600 ◦
C for 4 hrs.
 Particles of desired size is obtained after the calcined material is paletized, crushed and
sieved.

Catalytic characterization
The characterization is done with the residence time of 0.6 s.
Non-catalytic oxidative dehydrogenation
As the temperature is increased from 410
31 %) decreases drastically. Butadiene was not detected. The selectivity for combustion products
(CO2) increases slightly and for the cracki
Figure 3.1.1 Effect of reaction temperature on the non
n-butane conversion (●) and selectivities
Catalytic oxidative dehydrogenation
As the temperature is increased from 450
31 %) decreases slightly and the selectivity to butadiene increases (f
selectivity for combustion products (CO
9
The characterization is done with the residence time of 0.6 s.
ve dehydrogenation
As the temperature is increased from 410 ◦
C to 550 ◦
C, the selectivity for butenes (from 89 % to
decreases drastically. Butadiene was not detected. The selectivity for combustion products
(CO2) increases slightly and for the cracking products it increases (9 % to 53 %).
Effect of reaction temperature on the non-catalytic oxidative dehydrogenation of n
butane.
●) and selectivities for butenes (□), CO2 (◊) and cracking products (∆).
Catalytic oxidative dehydrogenation
As the temperature is increased from 450 ◦
C to 550 ◦
decreases slightly and the selectivity to butadiene increases (from 17 % to 32 %). The
selectivity for combustion products (CO2) decreases and the cracking products increase
decreases drastically. Butadiene was not detected. The selectivity for combustion products
ng products it increases (9 % to 53 %). [3]
ive dehydrogenation of n-
◊) and cracking products (∆).
rom 17 % to 32 %). The
increase. [3]

Figure 3.1.2 Effect of reaction temperature on the oxidative dehydrogenation of n
n-butane conversion (●), total selectivity for dehydrogenation products (TDS) (■) and selectivities
for butenes (□), butadiene (x), CO2 (
From this paper we conclude that, in the non
for butenes (from 89 % to 31 %)
550 ◦
C).
In the catalyzed oxidative dehydrogenation, with
selectivity for butenes decreases slightly (from 39 % to 31 % ) as the temperature is increased
(450 ◦
C to 550 ◦
C). Maximum conversion of butane to butene is obtained at 550
3.1.3. ZINC MODIFIED ZSM
For the dehydrogenation of n-butane to n
exchange of potassium ions before the zinc metal impregnation, since the acid sites are active in
cyclodimerization and dimerization reactions. The zinc metal contributes to the dehydrogenation
activity of n-butane. [4]
The ZSM-5 catalyst is synthesized
10
Effect of reaction temperature on the oxidative dehydrogenation of n
Mg3(VO4)2/MgO.
●), total selectivity for dehydrogenation products (TDS) (■) and selectivities
□), butadiene (x), CO2 (◊) and cracking products (∆).
From this paper we conclude that, in the non-catalyzed oxidative dehydrogenation, the selectivity
%) decreases drastically as the temperature is increased (450
dehydrogenation, with MgO-supported Mg3(VO3)2
decreases slightly (from 39 % to 31 % ) as the temperature is increased
C). Maximum conversion of butane to butene is obtained at 550 ◦
ZINC MODIFIED ZSM-5 CATALYST
butane to n-butene, the bronsted acid sites must be replaced with
synthesized in the Si/Al ratio of 40.
Effect of reaction temperature on the oxidative dehydrogenation of n-butane over
●), total selectivity for dehydrogenation products (TDS) (■) and selectivities
◊) and cracking products (∆).
oxidative dehydrogenation, the selectivity
decreases drastically as the temperature is increased (450 ◦
C to
2 as catalyst, the
decreases slightly (from 39 % to 31 % ) as the temperature is increased
◦
C. [3]
sted acid sites must be replaced with

11
Impregnation of zinc over ZSM-5 catalyst can be done in two ways.
First way is, initially the calcination is done with nitrogen for 7 hrs and later calcination is done
for 8 hrs with air. The ZSM-5 is ion exchanged in 1M KNO3 solution for a duration of 24 hrs at
room temperature and it is impregnated with Zn(NO3)2.6H2O.
The other way is, ion-exchange is done with 1M Zn(NO3)2.6H2O solution for a duration of 48
hrs. The calcination is done at 500 ◦
C for 4 hrs. [4]
Catalyst characterization
The yield of n-butene isomers decreases (from 14 to 5 Mass. %) drastically as the time on stream
is increased (from 10 to 175 min). The yield of isobutane and 1, 3- butadiene almost is the same
with a very slight decrease as the time on stream is decreased. There is no change in the aromatic
products yield. [4]

3.1.4. PT/SN ZSM-5 CATALYST
In this paper, the catalytic dehydrogenation of
studied with the help of Pt impregn
main product to be attained is propene.
The H-ZSM-5 powder is synthesized
Figure 3.1.3 Dehydrogenation activity of Zn(imp)/K
The WHSV of n- butane in the experiment was 2h
12
5 CATALYST
In this paper, the catalytic dehydrogenation of mixed alkanes to their corresponding alkenes is
studied with the help of Pt impregnated and Pt/Sn impregnated over ZSM-5 as the catalyst. The
main product to be attained is propene. [2]
synthesized with the Si/Al ratio of 140.
Dehydrogenation activity of Zn(imp)/K-ZSM-5 as a function of TOS.
butane in the experiment was 2h-1
.
mixed alkanes to their corresponding alkenes is
5 as the catalyst. The

13
Monometallic catalyst
The Pt metal of 0.5 wt. % is impregnated over the H-ZSM-5 with the aqueous solution of 0.03 M
H2PtCl6 at 60 ◦
C.
After the impregnation, the sample is dried at 100 ◦
C for duration of 4 hrs. Followed by drying of
sample, calcination is done at 500 ◦
C for 4 hrs in a muffle furnace. [2]
Bimetallic catalyst
For the preparation of bimetallic catalyst impregnation is done twice.
Initially, the Sn metal of 0.1 wt. % is impregnated over the H-ZSM-5 powder with the aqueous
solution of 0.16 M SnCl2.2H2O at 80 ◦
C. After the impregnation, the sample is dried at 100 ◦
C for
4 hrs. Followed by drying of sample, calcination is done at 500 ◦
C for 4 hrs.
Secondly, the Pt metal of 0.5 wt. % is impregnated on the Sn impregnated catalyst with aqueous
solution of 0.03 M H2PtCl6 at 60 ◦
C. The second impregnation is ended with drying of sample.
Both the catalysts are crushed and dechorination is done at 480 ◦
C for 4 hrs in the presence of
steam. Each and every catalyst sets are reduced in the presence of hydrogen at 510 ◦
C before the
reaction tests. [2]
The BET surface area (m2
/g) is analyzed and found out that it is increasing in the order as
follows: bimetallic (Pt-Sn/ZSM-5), monometallic (Pt/ZSM-5) and ZSM-5 without impregnation.
[2]
Table 3.1 BET surface area of the catalysts used.
Catalyst type BET surface area (m2
/g)
Bimetallic (Pt-Sn/ZSM-5) 354.1
Monometallic (Pt/ZSM-5) 346.9
Simple ZSM-5 341.9

Comparison of catalysts in terms of dehydrogenating capability
The conversion of feed is way better when bimetallic catalyst is compared with monometallic
and simple ZSM-5 catalyst. The dehydrogenating capability of simple ZSM
the monometallic catalyst is higher than simple ZSM
bimetallic catalyst is way better than simple ZSM
Figure 3.1.4 Feed conversion of different catalysts at WHSV = 6h
Comparison of propene selectivity for Pt
and time on stream (TOS):
For bimetallic catalyst, the ideal temperature for maximum selectivity to propene is 550
the start, the selectivity to propene is 25 % and as the time on stream incre
jumps to 55 %. Likewise a comparison is made for propene selectivity at temperatures of 575
600 ◦
C and 625 ◦
C. [2]
However the time on stream is increased from 1 to 10 hrs, the yield
significantly.
The major product to be obtained is the propene and initially its yield increases drastically (from
3 % to 8 %) for 1 hr time on stream. After one hour however the time on stream is increased,
there is no increase in the yield. [2]
14
Comparison of catalysts in terms of dehydrogenating capability:
5 catalyst. The dehydrogenating capability of simple ZSM-5 is very low and of
lyst is higher than simple ZSM-5. The dehydrogenating capability of
bimetallic catalyst is way better than simple ZSM-5 and monometallic catalysts.
Feed conversion of different catalysts at WHSV = 6h-1.
selectivity for Pt-Sn/ZSM-5 at different temperatures
and time on stream (TOS):
For bimetallic catalyst, the ideal temperature for maximum selectivity to propene is 550
the start, the selectivity to propene is 25 % and as the time on stream increases the selectivity
jumps to 55 %. Likewise a comparison is made for propene selectivity at temperatures of 575
However the time on stream is increased from 1 to 10 hrs, the yield of butene
or product to be obtained is the propene and initially its yield increases drastically (from
[2]
5 is very low and of
nating capability of
[2]
1.
5 at different temperatures
For bimetallic catalyst, the ideal temperature for maximum selectivity to propene is 550 ◦
C. At
ases the selectivity
jumps to 55 %. Likewise a comparison is made for propene selectivity at temperatures of 575 ◦
C,
of butene does not vary
or product to be obtained is the propene and initially its yield increases drastically (from

Figure 3.1
1.
15
3.1.1 Propene selectivity of different catalysts at WHSV =Propene selectivity of different catalysts at WHSV = 0. 6h-

3.2. DIMERIZATION OF ALKE
Dimerization is a process of producing
presence of catalyst. It is utilized
precursor in the production of isooctanes. Since 2006 iso
scale of 40,000 tons per year at a plant in Kawasaki, Japan. The octane number (RON) of octene
is 115. [7]
Figure 3.2.1 Conversion of Isobutene to Isooctene by dimerization.
The formation of oligomers from n
is a difficult task. As the conversion of iso
corresponding dimers. [9] The main objective of today’s researchers is to develop a catalyst
which has a high selectivity to dimers. For decades solid acid catalysts have been used as the
catalyst for dimerization, especially catalysts consisting of Ni over zeolite framework, oxides and
organo metallic nickel complexes.
isooctane are isoether process developed by Snamprogetti and CDIsoether technology by
CDTECH. [7, 8] In the latter process, butenes
etherified to obtain iso-octane. [9]
16
DIMERIZATION OF ALKENES
of producing dimer by attaching two similar monomers together in the
ilized in the production of isooctenes. İsooctenes are used as a
cursor in the production of isooctanes. Since 2006 isooctenes are produced commercially on a
40,000 tons per year at a plant in Kawasaki, Japan. The octane number (RON) of octene
Conversion of Isobutene to Isooctene by dimerization.
The formation of oligomers from n-butane is a consecutive process and obtaining only the dimer
task. As the conversion of isobutenes increases less is the chance of obtaining their
The main objective of today’s researchers is to develop a catalyst
as a high selectivity to dimers. For decades solid acid catalysts have been used as the
organo metallic nickel complexes. [10] Some of the commercial available methods to obtain
octane are isoether process developed by Snamprogetti and CDIsoether technology by
In the latter process, butenes are dimerized, partially dimeriz
[9]
dimer by attaching two similar monomers together in the
octenes are used as a
octenes are produced commercially on a
40,000 tons per year at a plant in Kawasaki, Japan. The octane number (RON) of octene
Conversion of Isobutene to Isooctene by dimerization.
is a consecutive process and obtaining only the dimer
butenes increases less is the chance of obtaining their
The main objective of today’s researchers is to develop a catalyst
as a high selectivity to dimers. For decades solid acid catalysts have been used as the
ble methods to obtain
octane are isoether process developed by Snamprogetti and CDIsoether technology by
are dimerized, partially dimerized or partially

Figure
Significance of Lewis and Bronsted acid sites in dimerization
Unsaturated compounds forms if strong lewis acid sites are present, where
to the formation of essential carbenium ions for dimerisation to occur.
İsobutene are adsorbed at lewis acid sites and near the bronsted acid sites alkene formation
increases. The formation of alkenes at the bronsted acid sites increases the chance of
dimerization. In all the catalyst both the bronsted and lewis acid sites must be high.
3.2.1. NOVEL PHOSPHORIC ACI
In this paper the developed catalyst is compared with silica alumina catalyst. In general when the
catalyst used is silica alumina, as the conversion of iso
isooctenes decreases. But when novel phosphoric acid is used
increases even at higher conversion of iso
17
Figure 3.2.2 Commercial dimerization plant
Significance of Lewis and Bronsted acid sites in dimerization
Unsaturated compounds forms if strong lewis acid sites are present, where these compounds lead
to the formation of essential carbenium ions for dimerisation to occur. [8]
NOVEL PHOSPHORIC ACID CATALYST
a, as the conversion of isobutenes increases the chance of obtaining
octenes decreases. But when novel phosphoric acid is used, the selectivity towards iso
ven at higher conversion of isobutenes. [7]
these compounds lead
ses the chance of obtaining
the selectivity towards isooctenes

18
Reaction mechanism
The reaction mechanism followed by both the catalyst explains the reason in the dimer
selectivity. The former catalyst leads to the formation of alkyl cation, the carbonium ion’s
reactivity does not depend upon the number of carbon atoms. Hence the reaction does not limit
to dimers. The dimer formed undergoes polymerization to form polymers. [7]
The latter one leads to the formation of acid ester, formed from the reaction between isobutene
and phosphoric acid. The phosphoric acid ester has a three dimensional structure which restricts
the reaction to yield dimers. There is no room for alkyl groups to form polymers. The ortho
phosphoric acid monomer supported over silica has more acidity and selectivity towards
isooctene than compared to SPA (Solid phosphoric acid) catalyst.
Factors affecting the activity
The developed catalyst life is affected by factors including outflow of phosphoric acid and
change in state due to condensation- dehydration of phosphoric acid. The outflow can only be
controlled by careful optimization of the operation. The reason for the outflow is that, the
phosphoric acid monomer is not chemically bonded to the silica support.
The moisture level in the reactor also affects the acidity and selectivity of the catalyst. At low
moisture level, the phosphoric acid monomer changes to polymer due to dehydration. The
moisture density can be maintained by adding sufficient amount of water to the butene feedstock.
[7]
Regeneration of catalyst
Since phosphoric acid in SPA catalyst is chemically bonded, the process regenerating is
impossible. On the other hand, the developed catalyst can be regenerated due to fact that
phosphoric acid monomer is not chemically bonded to the silica support. Regeneration can be
done by immersing the support in the solution of phosphoric acid. The usage of developed
catalyst is cost effective, it makes possible to obtain large amount of isooctene in a single step. In
general, at low conversion of butenes the selectivity towards isooctene is high.
Hence in the case of low selective catalyst, the conversion is kept low in the first reactor so as to
obtain maximum dimer. The unreacted butenes are removed by distillation and it is fed into the

second reactor so as the process is
dimer selectivity can be obtained in a single step reaction with the help of single reactor.
Figure
3.2.2. NICKEL MODIFIED ZEOL
In this paper zeolites with three different frameworks HY
taken and nickel is impregnated over the zeolites using three prescursor salts including NiCl
NiSO4 and NiCO3. The acidic properties of nickel modified zeolite
stability, acidity and the selectivity towards iso
NiCO3 is the most effective modified
compared to the other modified catalysts
19
process is repeated. [7] Whereas in the developed catalyst case, high
r selectivity can be obtained in a single step reaction with the help of single reactor.
Figure 3.2.3. Developed dimerization process
NICKEL MODIFIED ZEOLITES
In this paper zeolites with three different frameworks HY-zeolite, Hβ zeolite, H
taken and nickel is impregnated over the zeolites using three prescursor salts including NiCl
. The acidic properties of nickel modified zeolites are responsible for the
and the selectivity towards isooctene. The Ni impregnated HY
is the most effective modified catalyst; the selectivity towards dimerization
compared to the other modified catalysts. The Ni contributes to the acidity of the catalyst by
Whereas in the developed catalyst case, high
r selectivity can be obtained in a single step reaction with the help of single reactor.
zeolite, Hβ zeolite, H-mordenite are
taken and nickel is impregnated over the zeolites using three prescursor salts including NiCl2,
s are responsible for the
octene. The Ni impregnated HY-zeolite with
dimerization is more when
. The Ni contributes to the acidity of the catalyst by

20
replacing the aluminium ion present in the zeolite. The Si/Al ratio of the framework also affects
the acidity.
Table 0.1 Si/Al ration and acidity (mmol/g) of the zeolite frameworks.
Zeolite framework Si/Al ratio Acidity (mmol/g)
HY-zeolite 5.2 0.82
Hβ zeolite 150 0.82
H-mordenite 90 0.37
All the zeolite frameworks are immersed in solutions of NiCl2, NiSO4 and NiCO3. The solutions
are then filtered and the precipitate obtained is for duration of 12 hr at 373 K. Followed by
drying, calcination is done for 5 hr at 773 K. The impregnation of Ni over the framework is done
so that the concentration range is 0 to 16.5. Wt. % [8]
Influence of precursors over total pore volume and average pore diameter.
In the characterization part the properties including BET total area, total acidity, pore size
distribution, pore volume and average pore diameter are determined by TPD analysis.
The avg. pore size diameter of the HβZ catalyst when compared to the other catalyst as HM,
HYZ is almost double the size. [8] Whatever the precursor salt used to impregnate Ni over the
zeolite framework does not vary the pore size diameter at large.

21
Table 0.2 Total pore volume and avg. pore diameter of the impregnated zeolite frameworks with
different Nickel precursor salts.
Precursor salt/support Total pore volume (cc/g) Avg. Pore diameter (Å)
NiSO4.6H2O/HM 0.003 35.6
NiSO4.6H2O/HβZ 0.94 89.7
NiSO4.6H2O/HYZ 0.124 36
NiCl2.6H2O/HM 0.003 35.6
NiCl2.6H2O/HβZ n.m n.m
NiCl2.6H2O/HYZ 0.2097 36.34
NiCO3.2Ni(OH)2.4H2O/HM 0.178 35.9
NiCO3.2Ni(OH)2.4H2O/HβZ 1.005 88.31
NiCO3.2Ni(OH)2.4H2O/HYZ 0.4085 36.12
HM 0.0086 36.2
HβZ 0.886 87.54
HYZ 0.1654 36.08
The total pore volume of the framework happens to be dependent upon the nickel precursors
used. When we compare the HM catalysts which is impregnated with different precursors, the
nickel carbonate salt used as the precursor have high total pore volume.
In case of HβZ catalysts, the nickel carbonate salt used as precursor have high total pore volume
when compared to the other precursors used. [8]
In case of HYZ catalysts, the nickel carbonate salt used as precursor have high total pore volume
when compared to the other precursors used.
We conclude than NiCO3.2Ni(OH)2.4H2O when used as the precursor improves the total pore
volume irrespective of the zeolite framework used.

Influence of operating pressure on conversion
We know that increasing the pressure tend
isobutene there will be an increase in conversion due to the increase in con
and isobutene. But increase in pressure has
octene. The ideal operation pressure is found out to be 90 psig
The B6 zeolite sample is chosen and a graph is plotted for conversion
for the following reaction conditions T = 25
mL/h. [8]
Figure 3.2.1. Influence of operating pressure on conversion,
Operation condition: T = 25
Influence of operation temperature on selectivity
At low temperature range, the selectivity towards dimers ten
carried out room temperature.
For the B6 zeolite sample a graph is plotted for conversion
following reaction conditions P = 15 psig, WHSV = 0.09 h
22
Influence of operating pressure on conversion
We know that increasing the pressure tends to induce condensation of isobutene. By condensing
butene there will be an increase in conversion due to the increase in contact between acid sites
. But increase in pressure has a direct effect in reducing the selectivity towards
octene. The ideal operation pressure is found out to be 90 psig.
The B6 zeolite sample is chosen and a graph is plotted for conversion vs. time on stream (TOS)
for the following reaction conditions T = 25 ◦
C, WHSV = 0.09 h-1
and isobutene flow = 9.6
. Influence of operating pressure on conversion,
T = 25 ◦C, WHSV = 9h-1 and isobutene flow = 9.6 mL/h, B6 catalyst.
Influence of operation temperature on selectivity
At low temperature range, the selectivity towards dimers tends to be less. Hence the reaction is
For the B6 zeolite sample a graph is plotted for conversion vs. time on stream (TOS) for the
following reaction conditions P = 15 psig, WHSV = 0.09 h-1
and isobutene flow = 9.6 mL/h.
s to induce condensation of isobutene. By condensing
tact between acid sites
educing the selectivity towards
time on stream (TOS)
and isobutene flow = 9.6
1 and isobutene flow = 9.6 mL/h, B6 catalyst.
ds to be less. Hence the reaction is
time on stream (TOS) for the
and isobutene flow = 9.6 mL/h.

At room temperature, the selectivity is steady and is high and also there is a slight increase when
the time on stream is increased.
for a few hours initially and as the time on stream increases the selectivity falls. At intermediate
temperature like 60 ◦
C, the selectivity increases with time on stream.
Figure 3.2.2 Influence of react
Operation condition: P = 15 psig, WHSV = 0.9 h
Influence of Ni loading on co
A set of HY-Zeolites are taken and their Ni loading is varied. All the sets are compared by
plotting a graph between conversion and time on stream for operation
= 25 ◦
C and WHSV = 0.09 h-1
. [8]
The catalyst set with Ni loading of 3.2 % shows higher conversion and it remains almost the
same whatever the time on stream is. Even when the
increases, the selectivity towards the desired products
23
m temperature, the selectivity is steady and is high and also there is a slight increase when
[8] For temperatures as high as 184 ◦
C the selectivity increases
and as the time on stream increases the selectivity falls. At intermediate
C, the selectivity increases with time on stream.
Influence of reaction temperature on isobutene dimers selectivity
P = 15 psig, WHSV = 0.9 h-1
, isobutene flow = 9.6 mL/h, B6
Influence of Ni loading on conversion
Zeolites are taken and their Ni loading is varied. All the sets are compared by
raph between conversion and time on stream for operation conditions
[8]
same whatever the time on stream is. Even when the conversion reduces as the time on stream
increases, the selectivity towards the desired products is high.
m temperature, the selectivity is steady and is high and also there is a slight increase when
C the selectivity increases
and as the time on stream increases the selectivity falls. At intermediate
mers selectivity.
, isobutene flow = 9.6 mL/h, B6 catalyst.
Zeolites are taken and their Ni loading is varied. All the sets are compared by
s of P = 5 psig, T
as the time on stream

Figure 3.2.3 Variation of Nickel
Operational condition:
Influence of particle size on conversion
The mass transfer resistances can be avoided by choosing very small particle size (0.7 mm as
maximum). For HY-zeolite consisting of 9 % Ni loading and at operation conditions of T = 25
◦
C, P = 4 psig and WHSV = 0.09 h
particle size. [8]
The conversion is high when the catalyst particle is very less. As the size of the particle increases
the conversion decreases along with it. From 0.7 mm onwards as the particle size increases the
conversion remains constant.
24
Variation of Nickel load over catalysts HY-Zeolite.
Operational condition: WHSV = 0.09 h-1
, T = 25 ◦
C, P = 5 psig.
ence of particle size on conversion
zeolite consisting of 9 % Ni loading and at operation conditions of T = 25
C, P = 4 psig and WHSV = 0.09 h-1
, a graph has been plotted between conversion and catalyst
zeolite consisting of 9 % Ni loading and at operation conditions of T = 25
nversion and catalyst

Figure 3.2.4 Conversion as function of particle size, catalyst HY
Operational condition:
25
Conversion as function of particle size, catalyst HY-Zeolite with 9% of Nickel load
catalyst.
Operational condition: P = 4 psig, T = 25 ◦
C, WHSV = 0.09 h-1
.
with 9% of Nickel load

26
4. EXPERIMENTAL METHODS
4.1. OBJECTIVES
The main focus is to develop a 10 membered ring ZSM-5 catalyst support and impregnate it with
Zn metal to increase the total acidity. Higher the acidity of the catalyst higher the conversion will
be. A set of three catalyst supports are prepared with different proportions of binding agent.
4.2. METHODOLOGY
4.2.1. PREPARATION OF CATALYST SUPPORT
Extrudation
A set of three samples are extruded with the following proportions of Pural SB and Al(OH)3 as
the alumina class binders. In all the samples to provide a better integrity and strength kaolin
another binder is used.
Table 4.1 Proportion of sample
Sample number Proportion
1
ZSM-5 extruded with
5 % Al(OH)3 + 5 % Pural SB + 5 % Kaolin
2
ZSM-5 extruded with
3
ZSM-5 extruded with
Peptization is done using 1.5 % acetic acid solution. For each sample 10 mL of 1.5 % acetic acid
solution is made by adding 0.15 mL of acetic acid to 10 mL of distilled water.

27
The extrudates are made in the mortar. In the mortar, the alumina binding agents are made a
paste by adding the prepared acetic acid solution. To the paste made ZSM-5 is added and well
grinded to obtain a homogenous paste. The paste been made is extruded with the help of the
extruder.
Material balance of extrudate preparation:
1st sample:
Weight of ZSM-5 = 20 g
Weight of hydrated alumina = 1 g
Weight of Pural SB = 1 g
Weight of kaolin = 1 g
1st sample weight in mortar = 20 + 1 + 1 + 1 = 23 g
Weight of 1st extrudate = 1.632 g
2nd sample:
2nd sample weight in mortar (initial) = 21.368 g
To the paste in the mortar, 1 g of Pural SB is added and 10 mL of 1.5% of acetic acid solution
made is also added so as to obtain a homogenous mixture.
2nd sample weight in mortar = 21.368 + 1 = 22.368 g
2nd sample extrudate weight = 4.585 g
3rd sample:
3rd sample weight in mortar (initial) = 17.783 g

28
To the remaining paste in the mortar, 1 g of kaolin is added and 10 mL of 1.5% of acetic acid
solution made is also added to obtain a homogenous mixture.
3rd sample weight in mortar = 17.783 + 1 = 18.783 g
3rd sample extrudate weight = 5.612 g
4.2.2. DRYING OF THE EXTRUDED SAMPLE
The extruded sample is dried at room temperature until it becomes free from moisture. After a
significant amount of moisture is removed, drying of extrudates is done using a vacuum oven. In
the oven extrudates are placed for a duration of 8 hrs at 110 ◦
C. Due to the extrudates are exposed
to high temperature, most of the water content are removed. The weight of the sample before and
after drying indicates the amount of water content removed.
Sample 1:
Weight before drying = 1.582 g
Weight after drying at 110◦ C = 1.509 g
Sample 2:
Sample 3:

29
4.2.3. CALCINATION OF DRIED EXTRUDATES
Calcination is done in the muffle furnace for an intermediate stay of every half an hour 100◦
C is
increased and when 500 ◦
C is reached the extrudate sample is maintained at for duration of 5 hrs.
After calcination, the oxides and the other impurities present are burnt off.
Weight of the sample after calcination:
Weight of sample 1 = 1.487 g
4.3. TEMPERATURE PROGRAMMED DESORPTION
TPD analysis helps us to determine the number, type and strength of acid sites on the catalyst
surface by keeping track of the amount of gas desorbed at various temperatures.
TPD procedure is as follows,
 Degassing of the sample is done to remove the moisture content by introducing Ar/He
gas mixture at 120 ◦
C for duration of 30 minutes.
 The degassed sample is exposed to a gas mixture of NH3 and He at room temperature for
30 minutes. At this point, the NH3 occupies the acid sites present on the surface.
 The NH3 gas which is not adsorbed is flushed by passing He gas for 1 hr.
 The temperature of the sample is raised linearly from 120 ◦
C to 800 ◦
C. When the
activation energy is reached the bond between the adsorbate and the adsorbent are broke
and the ammonia gas is desorbed from the surface.
The desorbed gas is sensed through the TCD. The volume of gas desorbed is directly
proportional to the acid sites.

30
Table 4.2 BET surface area (m2
/g) and Langmuir surface area (m2
/g) of the calcined zeolite
frameworks.
Proportion
BET surface
area (m2
/g)
Langmuir
surface area
(m2
/g)
ZSM-5 extruded with
346.0706 504.4675
ZSM-5 extruded with
349.9457 518.6510
ZSM-5 extruded with
5 % Al(OH)3 + 10 % Pural SB + 10 %
Kaolin
319.3378 467.7131
Table 4.3 Total pore volume (cm3
/g), micro pore volume (cm3
/g) and acidity (mmol/g) of the
calcined zeolite frameworks.
Proportion
Total pore
volume
(cm3
/g)
Micro pore
volume
(cm3
/g)
Acidity
(mmol/g)
ZSM-5 extruded with
0.20505 0.10262 0.2363
ZSM-5 extruded with
0.2471 0.08015 0.2436
ZSM-5 extruded with
0.2056 0.08879 0.3361

31
4.4. IMPREGNATION OF EXTRUDATES WITH ZN
The calcined sample is impregnated with Zn by ion exchange method. The Zn ion contributes to
the dehydrogenation of the alkanes to alkenes. The Zinc nitrate hexa hydrate [Zn(NO3)2.6H2O] is
utilized for impregnating Zn over the catalyst and the ammonium chloride [NH4Cl] is used to
increase the acid sites.
4.4.1. ION EXCHANGE SOLUTION PREPARATION
0.5 M solutions of Zinc nitrate hexa hydrate and ammonium chloride are made by dissolving
74.372 g of Zinc nitrate hexa hydrate and 13.372 g of ammonium chloride in 500 mL of distilled
water respectively.
4.4.2. APPARATUS SETUP
Two necked round bottom flask is placed in an oil bath. A thermometer is fixed to one of the
neck with an aid of cork. It is fitted such that the bulb is just immersed in the solution to measure
the solution’s temperature. To the other neck water Liebieg condenser is fitted. The experimental
setup is placed over a magnetic stirrer with hot plate.
4.4.3. ION EXCHANGE METHOD
4 g of the extrudates sample and 100 mL solutions of zinc nitrate hexa hydrate and ammonium
chloride solutions made are taken in the round bottom flask. A magnetic bead is used to stir the
solution to achieve efficient impregnation. The solutions are maintained at 75 ◦
C for 3 hrs, while
the magnetic stirrer stirs the bead inside the solution. The Liebieg condenser circulates water
with the help of immersed pump to reduce the vapor losses After 3 hrs the filtrate is withdrawn
from the flask and stored in a conical flask for further titration.
The experiment is repeated in the same manner for 2 more times continuously and their
corresponding filtrates are withdrawn and stored in separate conical flasks.
In the process of ion exchange a significant amount of sample are dissolved in the filtrate due to
the attrition experienced by the sample.

32
4.4.4. DRYING OF IMPREGNATED SAMPLE
The extrudate sample in the two necked round bottom flask after impregnation is withdrawn and
dried at room temperature in order to remove the moisture content from the extrudates. After
drying at room temperature, the extrudates are dried in the vacuum oven at 110 ◦
C for 3 hrs.
Weight of sample 2 after drying = 1.815 g
Weight of sample 3 after drying = 2.610 g
4.4.5. CALCINATION OF IMPREGNATED SAMPLE
The impregnated sample are calcined in a muffle furnace, for an intermediate stay of every half
an hour 100 ◦
C is increased and when 500 ◦
C is reached the extrudate sample are maintained at
for a duration of 5 hrs. After calcination, the oxides and the other impurities present are burnt off.
The Na+
ion in ZSM-5 which is replaced by NH4+
ion are replaced by H+
ion. Thus the calcined
extrudate sample’s acidity increases.
Weight of sample 2 after calcination = 1.701 g
Weight of sample 3 after calcination = 2.468 g
4.4.6. TITRATION
The amount of Zn which is impregnated in the catalyst by replacing sodium ions of the zeolite
framework is found out by titrating the collected filtrate against the EDTA solution.
Solution preparation
0.01 M EDTA solution is prepared by dissolving 1.865 g in 500 mL of distilled water. The EBT
is used as an indicator; it is prepared by dissolving 0.5 g of EBT in 50 mL of methanol. The
buffer solution of 10 Ph is prepared by dissolving 17.5 g of NH4Cl in 117 mL of NH4OH and
133 mL distilled water.
Titration procedure
In the conical flask 1 mL of the filtrate, 1 mL of buffer solution and 2 drops of indicator are
added. The solution initially is blood red in colour and it is titrated against EDTA solution till the

33
solution changes colour from blood red to iodine blue in colour. The titration procedure is done
to all the filtrate set obtained.
Calculation of the molarity of the filtrate
The volume of EDTA consumed while titrating against the filtrate which is obtained after the
impregnation process is noted down.
Table 4.4 Amount of EDTA consumed for extrudate of sample 2.
Filtrate number Volume of EDTA used (mL)
1 12
2 13.3
3 13.1
Table 4.5 Amount of EDTA consumed for extrudate of sample 3.
Filtrate number Volume of EDTA used (mL)
1 12
2 12.9
3 14

34
Table 4.6 Ph and Molarity of the respective Ion exchange.
SAMPLE
ION EXCHANGE 1 ION EXCHANGE 2 ION EXCHANGE 3
Ph Molarity (M) Ph Molarity (M) Ph Molarity (M)
2 3.5 0.24 3.5 0.266 3.5 0.262
3 4 0.24 4 0.258 4 0.28
5. RESULT AND CONCLUSION
For the Ist phase of ion exchange concentration of Zn present in filtrate is less than the
concentration of Zn in the starting of ion exchange solution. This indicates Zn is transferred from
ion exchange solution to the zeolite.
In the consequent ion exchange phase II & III the concentration od Zn in the filtrate after ion
exchange is more than the concentration of Zn in the starting ion exchange solution. This
indicates the Zn ion is coming back from zeolite into the aqueous phase.
Table 5.1 Comparison of Total acidty before and after Zn impregnation.
Sample Number Proportion
Total acidity
before
impregnation
(mmol/g)
Total acidity
after
impregnation
(mmol/g)
1
ZSM-5 extruded with
5 % Al(OH)3 + 5 % Pural SB
+ 5 % Kaolin
0.2363 N/A
2
ZSM-5 extruded with
5 % Al(OH)3 + 10 % Pural
SB + 5 % Kaolin
0.2436 N/A
3
ZSM-5 extruded with
5 % Al(OH)3 + 10 % Pural
SB + 10 % Kaolin
0.3361 0.363

35
From the data obtained from TPD analysis for the sample 3, the total acidity of the sample after
impregnation has become high when compared to the total acidity of the sample after
impregnation. This indicates that the availability of H+ ions for the formation of carbenium ions
has increased which in turn contributes to the conversion of n-butane to isooctane. And the
maximum NH3 desorption is found at 223.9 ◦
C.
6. FUTURE STUDY
The ion exchanged zeolites have to be analysed for its Zn content so as to verify the material
balance of Zn ions.

36
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