Introduction

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1.1 Introduction

Catalysis plays a vital role in providing a society with fuels, commodity and fine

chemicals, pharmaceuticals and means to protect the environment. It is clear that catalysis

has a multidimensional impact on society. The chemical industry largely depends on

catalysis and it is estimated that 80% of the industrial chemical processes in the 21st

century will be based on catalytic processes [1].

Catalysis is a phenomenon by which chemical reactions are accelerated by small quantity

of foreign substances called catalysts. A catalyst is a surface active material i.e. catalysis

occurs at the surface of the material and hence the activity of the catalyst depends very

much on the nature of its surface. Recognizing the exact nature of these surface species

and fine tuning them for still better catalytic performance are the main objectives of

catalyst research.

There are different types of catalysts. They range from a proton, H+ through Lewis acids,

organometallic complexes, organic and inorganic polymers, all the way to enzymes.

Catalysts are divided into three categories: Bio(Enzyme) catalysis, Homogeneous and

Heterogeneous catalysis [2-3].

In biocatalysis enzymes or microorganisms catalyze various biochemical reactions.

Prominent examples of biochemical reactions are isomerization of glucose to fructose by

using enzymes such as glucoamylase immobilized on silicon dioxide. Conversion of

acrylonitrile to acrylamide by coryne bacteria entrapped in polyacrylamide gel. The

classic dupont route to adipic acid and frosts biosynthetic route is followed using a

genetically modified E.Coli cell.

A reaction is called homogeneously catalyzed when the catalysts and the reactants or the

solution form a same physical phase. Typical examples of homogeneous catalysts and the

reaction catalyzed by them are as given below.

Homogeneous catalysts Reactions catalyzed

Organometallic complexes Wilkinson olefin polymerization catalyst

Carbonyls of Fe, Co and Rh Hydroformylation of olefins to corresponding

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aldehydes by carbonyls of Co or Rh.

Metal salts of organic acids Oxidation of toluene to benzoic acid in presence

of Co and Mn benzoates,

Heterogneous catalysis

Heterogeneous catalysis involves systems in which catalyst and reactants form separate

physical phases. In many instances the catalysts are in solid phase whereas, the reactants

are either in vapor or liquid phase. Examples of major industrial process using

heterogeneous catalysts are given below:

Heterogeneous catalysts Reactions catalyzed

Metals Polymerization of olefins by Ti- Zeigler-Natta catalyst

Metals oxides Oxidation of xylene to phthalic acids by Vanadium

oxide catalyst

Supported metal/metal oxides Hydrogenation of propene to propane in the presence of

supported metal catalysts.

Dehydrogenation of alkanes to alkenes by Pt/Al2O3

catalyst.

Zeolites Isomerization of xylenes and toluene’s to p-xylenes by

H-ZSM-5 zeolite.

Clays Cracking of long chain alkanes to alkanes and

alkylation of C3-C5 alkanes to C7-C9 isoalkanes using

clays

The special categories of heterogeneous catalysis are photo catalysis, electro catalysis

and environmental catalysis. In photo catalysis, light is adsorbed by the catalysis or a

reactant during a reaction. One example is utilization of semiconductor catalysts

(titanium, zinc and iron oxides) for photochemical degradation of organic substances on

self-cleaning surfaces. The main aim of environmental catalysis is environment

protection. Examples are reduction of NOx in stack gases with ammonia on V2O5-TiO2

catalyst and the removal of NOx, CO and hydrocarbons from automobile exhaust gases

by using the so called three- way-catalysts consisting of Rh-Pt-CeO2-Al2O3 deposited on

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ceramic honey combs. Electro catalysis involves oxidation/reduction by transfer of

electrons. Example: the use of catalytically active electrodes in electrolysis processes

such as chlor-alkali electrolysis and in fuel cells [2].

One of the key objectives of green chemistry is the waste minimization. Further a

sustainable process is one that optimizes the use of resources, while still leaving

sufficient resources for future generations. Heterogeneous catalysis is an important tool in

both the cases. In fact, as far as chemistry is concerned heterogeneous catalysis is a key to

sustainability.

1.1.1 Heterogeneous catalysts

The important categories of heterogeneous catalysts, also known as solid catalysts are

metal oxides, supported metal oxides, zeolites, clays, AlPO4 [4-9]. These materials may

be acidic/basic or oxidation/ reduction properties which catalyze a number of organic

transformations. Thus, in principle by suitable selection of a solid catalyst any type of

organic transformation can be catalyzed for the production of bulk and fine chemicals.

Heterogeneous metal catalysis is highlighted, in particular those associated with the

designing and characterization of catalytic materials, the surface science of catalysis,

catalyst testing and green chemistry.

The efficient use of heterogeneous solid catalysts offers many advantages over

conventional homogeneous liquid catalysts. Product isolation is simplified and reactions

often run under milder conditions and give higher selectivity. The atom efficiency of the

reaction is improved, the processes is simplified, precious raw materials used in the

manufacturing of the catalyst are given increased lifetime (through reuse) and the volume

of waste is significantly reduced [10, 11].

1.1.2 Solid acid catalysts

Metal oxides, supported metal oxides, zeolites, AlPO4 possess surface acid sites, and

hence are known as solid acids. The acid sites may be Bronsted or Lewis types. The

concentration and strength of these acid sites depend on texture and structure of the

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solidacids which intern depend on their pre and post synthetic modifications. Types of

solid acids and examples are shown in Table 1[12].

Table 1.Types of solid acid catalysts and examples.

Solid acid catalysts Examples

Simple oxides SiO2, Al2O3, ZrO2, TiO2, Fe2O3, MnOx

Mixed oxides/ supported

oxides

SiO2-Al2O3, ZrO2-Al2O3, ZrO2-SiO2, MgO-Al2O3, MoO-

ZrO2, TiO2-SiO2, ZrO2-MgO

Clays Kaolinite, Montmorillonite

Zeolites and zeotypes HZSM-5, HY, Hβ, mordenite, AlPOs and SAPOs

Mounted acids H2SO4, H3PO4, H3BO3 on silica, alumina, zirconia

Metal deposited/anion

modified oxides

Pt-SO42-

/ZrO2, Fe-SO42-

/ZrO2, Fe-Mn-SO42-

/ZrO2

Metal phosphates (Silicoalumino phosphate) SAPOs, aluminophosphates

(AlPO4)

Cation exchange resins Sulphonic acid group attached to cross-linkedpolystyrene

Heteropoly compounds H3PW12O40.24H2O, Cs2.5H0.5PW12O40

Carbon Activated charcoal, carbon nanotubes.

1.1.3 Supported Catalysts

The solid acid catalysts are used as such or loaded in general on an inert support and

used. Support is an important component in heterogeneous catalysis. When the active

species is not supported on an inactive material i.e unsupported catalysts, the atoms

present on the surface will only be taking part in the catalysis and remaining atoms

present inside the bulk of the unsupported system cannot take part in the reaction, since

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these atomic or molecular species remain inaccessible. In order to overcome this

problem, the active materials are often loaded on a support surface [13, 14].

Some of the important characteristic features of a support are:

Supports provide optimal dispersion of the active component, good acceleribility and

stability. Hence, a porous material which has high surface area is preferred as a

support. The porous nature of the support may also control the transport of the

reactant and the product molecules affecting the overall conversion.

The support diminishes the amount of the active component needed and increases the

effective surface area of the catalyst.

The support holds on its surface the microcrystalline particles of the active

component and prevents its sintering. Hence metal-support interactions are an

important in supported catalysis.

The support may interact with the active component deposited on it and form a new

complex which may have better catalytic activity and selectivity than that of the

support or the active component.

Non porous

Porous

Supported catalysts

1.1.4 Metal oxides in catalysis

Metal oxides make up a large and important class of catalytically active materials.

Their surface properties and chemistry is determined by their composition and structure,

the bonding character, the co-ordination of surface atoms and hydroxyl groups in exposed

terminating crystallographic faces. Metal oxides may be acidic or basic and also exhibit

redox properties. They may have simple composition like in simple and binary oxides,

but many technologically important oxide catalysts are complex and multicomponent

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materials. Metal oxides form an important class of industrial catalysts due to their

versatile nature [15]. Among the metal oxides which are widely employed as catalysts

and supports, the prominent ones are alumina, silica, zirconia and titania (Al2O3, SiO2,

ZrO2 and TiO2) [16].

These oxides form a set of catalysts encompassing a wide spectrum of catalytic activity

because of their acid-base and redox properties in their unmodified forms. Modification

of these simple oxides have opened up new vistas in the field of catalysis and

revolutionized the chemical industry giving rise to even solid super acids.

Realizing the boundless potential that has remained yet unexplored in the domain of

metal oxides, a lot of work is being done over alumina and zirconia catalyst systems. A

brief description of preparation, properties and catalytic applications of alumina, and

zirconia, their modified forms are given in the following section.

1.2 Alumina as catalyst and catalyst support

1.2.1 Preparation of alumina (Al2O3): The most important methods in practice for

laboratory preparation of alumina [17, 18] are

(a) Hydrolysis of an aluminum salt usually the nitrate using aqueous ammonia

Al(NO3)3 + Aq NH3→Al(OH)3+ NH4NO3

(b) Hydrolysis of an aluminum isopropoxide by water

3Al(OC3H7)3+ 3H2O →3Al(OH)3+3 C3H7OH

(c) Thermal decomposition of aluminum isopropoxide and

∆

Al(OC3H7)3→Al2O3

(d) Decomposition of aqueous Na/K-aluminate by CO2 etc.

2NaAlO2+ CO2→ Al2O3 + Na2CO3

1.2.2 Crystalline phases of alumina

Generally, the starting material for aluminum oxide is a precipitated hydroxide-

gibbsite or bayerite, both having the composition Al(OH)3. The hydroxide may be

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crystalline or amorphous. When the hydroxide is subjected to calcination at different

temperatures various phases of alumina are formed. The α-phase is the only

thermodynamically stable oxide of aluminium and is the final product of the calcination

process which follows the bayer treatment. The nature of these phase transformations has

now been studied for many years, and the pathways involved in the calcination include:

Gibbsite → boehmite (γ-AlOOH) → γ-alumina (γ-Al2O3) → δ-alumina (δ-Al2O3) → θ-

alumina (θ-Al2O3) → α-alumina. [19, 20] (Figure 1).

Figure 1. Thermal transformation sequence of aluminum hydroxides.

Each transition phase exhibits a distinct powder X-ray diffraction pattern. These phase

transformations are of fundamental importance in determining their catalytic activity

[21]. Thus the catalytic activity of alumina is influenced by the conditions at which it is

prepared such as the source from which alumina is obtained, precipitation and aging of

the hydroxide, preheating time and temperature and final calcinations temperature [22-

24].

1.2.3 Acidic and basic properties of alumina

Precipitated aluminum hydroxide has surface hydroxyl groups, on dehydroxylation

defects are generated. Defects may also be caused by anion addition. These defects are

potential sites of catalytic activity. The defect sites strongly influences the chemical

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properties of the remaining hydroxyls on the surface. Little is known about the electronic

and geometric structure of these defects or the specifics and their influence on the

reactivity of working catalyst. There are five different types of hydroxyl groups in

alumina as observed by Khozinger and P. Rathnaswamy (figure 2).The occurrence and

number of each type depends on the relative contribution of specific crystal faces. The

various OH groups are expected to have varying chemical properties. Type III should

exhibit the highest acidity, while types IA and IB should be the most basic.Lewis and

Bronsted acidity in aluminum hydroxide may be generated by subjecting it to heat

treatment figure 3. [25].

Figure 2. Types of OH groups and planes of alumina as observed by H. Knozinger and P.

Rathnaswamy.

Figure 3. Co-ordination of alumina.

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1.2.4 Catalytic applications of alumina

The catalytic applications of alumina are based on its surface acidic and basic properties,

these applications have been extensively reviewed and reported [13]. Metal oxide and

anion modified alumina are used in many catalytic applications like opening of aliphatic

epoxides [26], as auto-exhaust catalyst [27], nitration of aromatic compounds [28],

solvent free esterification of carboxylic acid [29], selective catalytic oxidation of

ammonia in gasified biomass [30], isomerization of alkenes, dehydration of alcohols,

hydrogenation of aromatic compounds, dehydrogenation, isomerization, oxidation,

reduction, esterification and trans-esterification reactions [31-38].

1.3 Zirconia as catalyst and catalyst support

1.3.1 Preparation of zirconia (ZrO2): Different routes, such as chemical precipitation,

hydrothermal, gas-condensation, sonochemical, and sol-gel processes are employed for

the synthesis of zirconium hydroxide which in turn is converted into zirconia by

calcination [39-43].

1.3.2 Crystalline phases of Zirconia

Figure 4. Thermal transformation sequence of Zirconia.

ZrO2 exist in three polymorphic forms: these are

Cubic (c) which has a fluorite structure in which Zr atoms are coordinated to

eight oxygen atoms

Monoclinic (m) it sometimes referred to as the baddeleyite structure and

Tetragonal (t) which has distorted fluorite structure whose diffraction patterns

can be indexed to a face centered tetragonal cell.

< 1170 °C 1170°C-2370 °C >2370

Monoclinic Tetragonal Cubic

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A schematic crystal structure of the above three forms are showed in figure 5.

Figure 5. Crystal structure of monoclinic (a), tetragonal (b) and cubic zirconia(c). Source:

[44].

1.3.3 Phase transformation in zirconia:

Tetragonal phase of zirconia has been found to be catalytically active. Several

attempts have been made to stabilize this phase. Zirconia has been found to change

phases under certain temperatures and pressures. At normal atmospheric pressure the

oxide is monoclinic at room temperature. It then transforms to the tetragonal and cubic

phases with an increase in temperature. The monoclinic-tetragonal phase transformation

has been extensively studied due to its theoretical and practical importance [45-50]. The

monoclinic to tetragonal phase transformation rate depends on the particle size of the

zirconia powder and process of powder preparation [51, 52]. The larger the particle size

of the prepared zirconia, the faster the phase transformation occurs.

Addition of sulfate anions can also play an important role in phase

transformation. Bridging sulfate ions stabilize the structure of zirconia since it can retard

the formation of oxo-bonds between zirconium atoms and oxygen atoms (figure 6). This

will prevent sintering at high temperature and hence, prevent rapid phase transformation

and will stabilize the surface area [53, 54]. Factors like precursor, pH, and aging time

influence the phase transformation [55]. The sample precipitated at low pH exhibited fast

phase transition from tetragonal to monoclinic. Furthermore, the phase transformation

occurred more rapidly in an oxygen environment than in an inert gas atmosphere.

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Figure 6. Structure of sulphated zirconia [56]

1.3.4. Acidic and base properties of zirconia

Zirconia is amphoteric oxides which possess strong acid-base properties. The

existence of co-coordinately unsaturated cations is responsible for Lewis acidity.

Adsorption of water molecules results in the reversible transformation of Lewis acid sites

into Bronsted acid sites. Bronsted acid sites and Lewis acid sites are the probable forms

of acidity at lower and higher temperatures respectively [57]. Its application has however

been limited by the presence of mild acidic and basic sites on its surface. In this regard

recent years, there are many investigations on increasing the acid strength of zirconia by

surface as well as structural modification. The most prominent among them is anchoring

catalytically active metal oxides, addition of cationic or anionic substances such as WO3,

SO42-

and MoO3 at sub-monolayer level to generate newer acidic sites.

The results achieved in recent years are quite remarkable considering the fact that

strength of the order of 100% H2SO4 can be achieved by these modifications which is

rarely found in any heterogeneous catalyst [58]. The grafting of sulfated species on ZrO2,

strong acidic sites are developed on their surfaces which are termed as “super acidic.

Tungsten oxide species dispersed on zirconia supports (WOx-ZrO2) comprise another

interesting class of solid acids [59]. The strong acid sites originates on these materials when

zirconia oxyhydroxide (ZrOx(OH)4-2x) is impregnated with solutions containing tungstate

anions and then oxidized at high temperatures.

1.3.5 Catalytic applications of zirconia

ZrO2 has been used as an acid-base catalyst and also as an catalyst support for numerous

organic reactions in heterogeneous catalysis. Abundant literature is available in catalysis

where zirconia based solid acids are employed in organic transformations [60-64].

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1.4 Oxides of manganese and its catalytic applications

Manganese oxides represent a group of transition metal (TM) oxides which hold

promising properties for a range of chemical reactions. Due to the variable valence of

manganese cations, the chemistry of its compounds is very rich. This holds true for

manganese oxides as well. The common manganese oxides stable at ambient conditions

are: Mn3O4, Mn2O3 and MnO2 and MnO.

The thermodynamic stability of these oxides increases in the given order with increasing

temperature and decreasing partial pressure, a fact which can be made use of while

preparing the different oxides [65]. Manganese oxide has been used as a substitute for the

noble metal catalysis, but, because of the lower surface area the catalytic activity was

often disturbed [66, 67]. Therefore, there has been tremendous research interest on the

laboratory synthesis of manganese oxides with various structures to improve the surface

area and catalytic ability. The surface area of manganese oxide is not very high,

especially at high temperatures. So manganese oxides mixed with or supported on other

high surface area materials are extensively investigated. MnOx-ZrO2 system has been

shown to have a better reducibility compared to MnOx supported on other materials, such

as alumina, titania, and silica [68].

1.4.1 Effect of calcination on manganese oxide

As the calcination temperature increases, the surface area decreases and the phase

also changes (the Mn ions transform from higher oxidation state to lower state). The heat

treatment at various temperatures leads to the decomposition of the manganese oxide.

According to the phase diagram (Figure 7.) the occurrence of phase depends on the

temperature and oxygen partial pressure. In the ambient pressure, from about room

temperature to 400oC, the stable phase is MnO2 between 400 and 700

oC, the stable phase

is Mn2O3. Mn2O3 further decomposes to Mn3O4 and then MnO above 700oC. The

literature data showed that the crystalline manganese oxide was MnO2 or Mn2O3 after

synthesis and low temperature calcination (~300oC. And indeed the crystalline phases

changed with calcination temperatures and atmosphere for pure manganese oxide or

supported manganese oxide [69-71].

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Figure 7: Thermodynamic phase diagram of manganese oxide, the different lines are the

phase boundary proposed by different researchers [71].

Applications of manganese oxide as catalyst

Manganese oxides are one of the largest families of porous materials with various

structures as found in manganese oxide minerals all over the world. Manganese oxide

dispersion depends on the Mn-precursor, loading, preparation method, thermal treatment

and the presence of foreign ions [72, 73]. Manganese oxide is an active catalyst for the

decomposition of ozone [74], nitrous oxide [75] and isopropanol [76]; the oxidation of

methanol [77], ethanol [78], benzene [79], CO [80] and propane [81]; the reduction of

nitric oxide [82] and nitrobenzene [83]; and the combustion of volatile organic

compounds (VOC) [84, 85]. Apart from these it is also used in ozone decomposition [86],

selective oxidation of CO, photocatalytic oxidation of organic pollutants and waste water

treatment. The high activity of manganese oxides is attributed to their redox property and

their oxygen storage capability (OSC). The oxygen adsorption and desorption abilities are

due to the wide range of oxidation states available (from +2 to +4) for manganese in

MnOx.

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1.5 Experimental aspects of catalysis

One of the important aspects of catalysis research is the identification of catalytic activity

and structure relationship of the catalyst. Up to date in most cases this remains as an

unsolved problem. A rational design of a catalyst is governed by, in general three

interconnected principles: preparation, characterization and reactivity. A triangular

relationship between these three principles has been shown by many authors in the design

of the catalyst for a specific application. (Figure 8)

Figure 8. The scheme of interconnectivity of catalyst design on synthesis characterization

and reactivity [1]

The above diagram shows how preparation of a catalyst is related to characteristics and

reactivity and reactivity depends on both preparation and characteristics. The following

aspects of catalyst design are briefly described:

Preparation of heterogeneous catalyst

Characterization techniques

Catalytic activity studies.

1.5.1 Preparation of catalysts

The preparation method of catalysts has a strong influence on their final properties [87].

Various method of preparation of heterogeneous catalysts, principles of the methods with

Reactivity

Preparation characterization

Catalyst design

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specific examples has been published by Selim Senkan [88]. The preparation parameters

that influence the physico-chemical properties of the precipitate are shown in the figure 9.

Figure 9. Parameters affecting the properties of the precipitate and the main properties

influenced.

Precipitation-impregnation and co-precipitation are the most commonly employed

methods for the preparation of heterogeneous catalysts.

Precipitation

In the precipitation method the metal salts are dissolved in water and the precipitation is

carried out by slow addition of required amount of precipitating agent like ammonium

hydroxide or sodium carbonate at room temperature until the pH reaches a required

value. The precipitate thus obtained is washed with distilled water to remove all anions

present, dried overnight at 110-120ºC. After precipitation/impregnation, the catalyst mass

is normally subjected to drying and calcination at desired temperature.

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Impregnation

In this procedure a certain volume of solution containing known amount of the precursor

of active phase is contacted with a previously weighed solid support. The amount of

metal ions that interactively remain bound to the support surface depends on the

adsorption capacity of the support, the period of impregnation and temperature of

impregnation. Wet impregnation and incipient wetness impregnation are the two methods

used in catalyst preparation, which can be distinguished depending on the volume of the

solution. In wet impregnation excess solution is generally used. After a certain time, the

solid is separated and the excess solvent is removed by evaporation. In the incipient

wetness impregnation the volume of solution of appropriate concentration is equal to or

slightly less than the pore volume of the support.

Co-precipitation

In Co-precipitation method two or more metal salts are completely dissolved in water and

the precipitation is carried out by slow addition of required amount of precipitating agent

until pH reaches required value. The precipitate thus obtained is aged for required

duration, washed with distilled water to remove all anions present, dried overnight at

100-120ºC. The catalyst mass are finely ground and subjected to calcinations at desired

temperature depending on the catalyst material prepared.

1.5.2 Catalyst characterization techniques

Characterization is an important field in catalysis. Spectroscopy, microscopy, diffractions

and methods based on adsorption or desorption and bulk reactions, all offer tools to

investigate the nature of an active catalyst. With such information we can understand the

catalyst better, so that modify them or even design new catalyst.

For the development of active, selective and stable catalyst we need to identify the

structural property that discriminates efficient from less efficient catalyst.

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Various spectroscopic and non-spectroscopic techniques have been employed to

characterize the solid acid catalysts include:

Fourier Transform infrared (FT-IR) spectroscopy

Powder X-ray diffraction studies (P-XRD)

N2 adsorption for BET surface area

Temperature programmed desorption of ammonia (TPD-NH3) and

n-butyl amine back titration method

Temperature programmed reduction (TPR)

Scanning electron microscopy (SEM)

Transmission electron microscopy (TEM)

Inductively coupling plasma (ICP).

A detail description of the principles and applications of the above techniques employed

in catalyst characterization is published by I. Chorkendorff et al. [3]

1.5.3 Catalytic activity determination

The activity of a catalyst in a chosen organic transformation is determined mainly by two

methods: Liquid phase and vapour phase catalytic activity studies.

In liquid phase studies, the reactant/s is/are taken in a suitable reaction vessel is mixed

with the catalyst to be evaluated. The reaction mixture is analyzed for the progress of the

reaction using a suitable analytical technique. In vapour phase studies, pre-heated

reactant or a mixture of reactants is passed over a solid catalyst bed maintained at a

definite temperature. The reaction products are condensed and analyzed using a suitable

analytical technique.

The degree of activity of a catalyst is described by the turn over number (TON) and the

catalytic efficiency by the turnover frequency (TOF) [1-3].

Turnover Number (TON): The turnover number specifies the maximum use that can be

made of a catalyst for a special reaction under defined conditions by a number of

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molecular reactions or reaction cycles occurring at the reactive center up to the decay of

activity.

The relationship between TOF and TON is:

TON = TOF [time–1

] .Lifetime of the catalyst [time] [–]

For industrial applications the TON is in the range 106-10

7.

Turnover Frequency (TOF): The turnover frequency TOF quantifies the specific

activity of a catalytic center for a special reaction under defined reaction conditions by

the number of molecular reactions or catalytic cycles occurring at the center per unit

time. For heterogeneous catalysts the number of active centers is derived usually from

sorption methods.

For most relevant industrial applications the TOF is in the range 10–2

- 102S

–1

(enzymes103-10

7S

-1).

1.6 Objectives and the scope of the proposed research work

It is evident from the reported literature that alumina, zirconia, modified forms of these

materials (as supported oxides as well as their anion modified forms) are extensively

investigated for their catalytic activity. However the reports on manganese oxide

modified alumina and zirconia as catalytic materials in organic transformations are

scarce. Application of the catalyst with respect to particular phase of the materials is less

i.e application of oxy-hydroxy phase of alumina (Boehmite) in organic transformations

and stabilization of the tetragonal phase of zirconia which is highly unstable and

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catalytically active could be achieved by modification by loading with some metal

oxides. Further the correlation between catalytic activity and the texture of the material

prepared need to be clearly understood. Thus this topic of study is still a rewarding and

demanding.

The main objectives of the present work are:

To prepare manganese oxide modified alumina and zirconia catalysts with different

percentage of manganese oxide.

To investigate the surface and bulk properties of the materials by suitable

characterization techniques.

To understand the precise role of manganese oxide on acid-base properties of

alumina and zirconia support.

To develop recyclable, ecofriendly and selective solid acid catalysts to synthesize a

few pharmacologically important organic fine chemicals.

To examine the structure-catalytic activity relationship if any.

To achieve the above objectives, the following methodology was adopted.

1.7 Methodology

Preparation alumina and zirconia supports and those containing different percentages

of manganese using precipitation-impregnation method and co-precipitation method

using ammonia as precipitating agent.

Physico-chemical characterization of these catalysts by various techniques such as

BET surface area, TPD-NH3, XRD, FT-IR, ICP, SEM and TEM.

Evaluation of the catalytic activity in organic transformations which involves

synthesis of benzimidazoles, benzodiazepines, bis(indolyl)methane,

dihydropyrimidinone, biphenylurea and quinoxalines.

Comparison of the catalytic activity and selectivity of these catalysts with their

physico-chemical properties.

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1.8 Organization of the thesis

The work carried out in the present doctoral work has been organized into five chapters.

Chapter I Introduction

Chapter II Preparation and characterization of alumina, zirconia,

manganese oxide modified alumina and zirconia catalysts and

their catalytic activity in the synthesis of Benzimidazoles and

Benzodiazepines

Chapter III Section A: Selective synthesis of Bis(indolyl)methanes using

Mn/Al2O3 and Mn/ZrO2 catalysts: The role of surface acidity

and particle morphology

Section B: Synthesis of Dihydropyrimidinones using modified

alumina and zirconia as catalysts

Chapter IV Synthesis of Quinoxalines: Role of catalyst acidity of various

solid acids

Chapter V Non phosgene method for the synthesis of Biphenyl urea using

alumina based catalysts prepared by different methods

Summary and Conclusion

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