I. SYNTHESIS, CHARACTERIZATION, AND BASE CATALYSIS OF NOVEL ZEOLITE SUPPORTED SUPER—BASIC MATERIALS

II. OXIDATIVE DEHYDROGENATION OF ETHANE OVER REDUCED HETEROPOLYANION CATALYSTS

Thesis by

Jonathan M. Galownia

In Partial Fulfillment of the Requirements

for the degree of

Doctor of Philosophy

CALIFORNIA INSTITUTE OF TECHNOLOGY

Pasadena, California

2005

(Defended May 27, 2005)

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provided by Caltech Theses and Dissertations

ii

You make a living by what you earn. You make a life by what you give.

- Sir Winston Churchill

To the glory of God

iii

ACKNOWLEDGEMENTS

I feel blessed to have spent five years at Caltech working with, and around, so many

talented and unique individuals. The constant stream of discoveries coming from this small

campus never fails to astound me. If you have a good idea, you can pursue it here, and you

will find many people willing to help out in any way they can. So, as much as I would like

to believe that I made it all on my own, there were numerous people supporting and

encouraging me throughout my stay here. I will mention some of the more influential

relationships I’ve made while pursuing my degree, but make no claim that this is a

comprehensive list.

I feel particularly fortunate to have been able to work with my advisor Mark Davis.

The unceasing stream of ideas produced by Mark is an inspiration and has allowed (and

sometimes pushed!) me to learn about far more than zeolite supported base catalysis or the

oxidative dehydrogenation of ethane. My experience here would not have been nearly as

rich as it was without Mark’s mentorship.

Another person who has been through all the projects and side-projects is Jay

Labinger, also on my thesis committee. Jay is never lacking of a thoughtful question or

quick and relevant insight into whatever problem or result is being discussed. Stacey

Zones, another member of my committee also brings thoughtful advice and more than

occasionally, a good laugh. I would also like to thank Rick Flagan for serving on my thesis

committee after a rapid-fire introduction to my research.

iv John Bercaw served on my candidacy committee and swapped car stories with

me. He even made it out to an autocross once to watch me make a fool of myself after

adjusting some suspension settings. I must also thank the Bercaw lab for educating me in

the use of very clean dry boxes.

If it were not for Brian Santora, a long since departed post-doctoral scholar in the

lab, teaching me how to handle solid sodium and potassium I surely would have caught

something on fire during my first few syntheses. Sonjong Wang of the solid state NMR lab

was always willing to run a sample for me or help me to interpret NMR results.

My colleagues in the Davis lab have also been good friends, especially my

officemate of the last two years Hyunjoo Lee who will go on to be great scientist wherever

she ends up. I’ll miss our conversations about life, relationships, and God during our

ritualistic morning journey to the C-store for diet Coke or the Red Door for a cup of coffee.

Alex Blanc, our recently departed French post-doctoral scholar, was extremely helpful in

the synthesis of catalytic materials and a great pleasure to work with. Alex, Hyunjoo, and I

found ourselves discussing topics from French music to the creation of the universe as a

result of one of Alex’s questions or remarks. I shared numerous discussions with Andrea

Wight, now a proud mother or two working for Exxon-Mobil in Louisiana. John Murphy

and his wife Kate swapped dinner parties and recipes with me and my wife, Niki. John

always seemed to find that amusing website or article to share with the lab. No one has

been able to fill the gap since his departure to Harvard for law school, although Steve

Popielarski, Swaroop Mishra, and I have all tried. Jeremy Heidel, Derek Bartlett, and Dr.

Siwen Hu were my chaperones to the mouse lab. Joe Holles and Chris Dillon introduced

vme to the joy of taking data at a synchrotron and provided friendly banter while sharing an

office with me in the first two years of my stay here.

Outside of the lab, it was always nice to visit Mike Roy in the machine shop and

trade suspension tuning secrets and be tempted by the latest road racing time trial event. If

it weren’t for Mike, Rick Gerhart in the glass shop, and Tom Dunn in the electronics shop,

none of my equipment would ever have continued working long enough for me to

graduate. Mike even helped me fix and fabricate some car parts in the off-hours.

I gratefully acknowledge the sponsors of my research. The National Science

Foundation Fellowship provided me support for the first three years of my work. A grant

from BP-Amoco funded my research for the remaining two years.

I thank my parents, who have always believed in me and provided the best

education they could have while I was young. I thank my wife Niki, who possesses an

inspiring passion for life and who has stood by my side during all the best and the worst of

times, all while pursuing her own PhD. Degree in the Asthagiri lab. Finally, I thank God,

for without his blessings, none of this would have been possible.

viABSTRACT

This thesis is composed of two separate and unrelated projects. The first part of this

thesis outlines an investigation into the synthesis and characterization of a novel zeolite

supported super-base capable of carbon-carbon olefin addition to alkyl aromatics. A

zeolite supported basic material capable of such reactions would benefit many fine

chemical syntheses, as well as vastly improve the economics associated with production of

the high performance thermoplastic polyester polyethylene naphthalate.

The thermal decomposition of alkali—metal azides impregnated in zeolite X is

investigated as a novel route to the synthesis of a zeolite supported super-base.

Impregnation of the alkali—metal azide precursor is shown to result in azide species

occluded within the pores of the zeolite support by using high speed, solid-state 23Na MAS

and 2D MQMAS NMR, FTIR, and TGA characterization methods. Addition of alkali—

metal azides to the zeolite results in redistribution of the extra-lattice cations in the zeolite

framework. Thermal decomposition of impregnated azide species produces further cation

redistribution, but no neutral metallic clusters are detected by high speed, solid-state 23Na

MAS NMR following thermal activation of the materials. Instead, it is possible that

inactive ionic clusters are formed. The thermally activated materials do not promote base

catalysis for the isomerization of 1-butene, the ethylation of toluene and o-xylene, and the

alkenylation of o-xylene with 1,3-butadiene to produce 5-ortho-tolyl-pent-2-ene (5-OTP).

The lack of catalytic activity in the materials is attributed to failure of the materials to form

neutral metallic clusters during thermal treatment, possibly due to preferential formation of

NMR silent ionic clusters. The formation of neutral metallic clusters is found to be

viiinsensitive to synthesis technique and activation procedure. It is concluded that the

impregnation of alkali—metal azides in zeolite X does not provide a reliable precursor for

the formation of zeolite supported super-basic materials.

The second part of this thesis describes the oxidative dehydrogenation of ethane

over partially reduced heteropolyanions. Niobium and pyridine exchanged salts of

phosphomolybdic (NbPMo12Pyr) and phosphovanadomolybdic (NbPMo11VPyr) acids are

investigated as catalyst precursors to prepare materials for catalyzing the oxidative

dehydrogenation of ethane to ethylene and acetic acid at atmospheric pressure. The effects

of feed composition, steam flow, temperature, and precursor composition on catalytic

activity and selectivity are presented for both ethane and ethylene oxidation. Production of

ethylene and acetic acid from ethane using the catalytic materials exceeds that reported in

the literature for Mo-V-Nb-Ox systems under atmospheric or elevated pressure. Production

of acetic acid from ethylene is also greater than that observed for Mo-V-Nb-Ox systems.

Addition of vanadium reduces catalytic activity and selectivity to both ethylene and acetic

acid while niobium is essential for the formation of acetic acid from ethane. Other metals

such as antimony, iron, and gallium do not provide the same beneficial effect as niobium.

Molybdenum in close proximity to niobium is the active site for ethane activation while

niobium is directly involved in the transformation of ethylene to acetic acid. A balance of

niobium and protonated pyridine is required to produce an active catalyst. Water is found

to aid in desorption of acetic acid, thereby limiting deep oxidation to carbon oxides. A

reaction scheme is proposed for the production of acetic acid from ethane over the catalytic

materials.

viiiTABLE OF CONTENTS

Acknowledgements .......................................................................................................... iii Abstract ..............................................................................................................................vi Table of Contents............................................................................................................ viii List of Tables .....................................................................................................................xi List of Figures ..................................................................................................................xiv List of Schemes.............................................................................................................. xvii Chapter One: Introduction and Organization of Thesis Presentation ....................1 Part One: Synthesis, Characterization, and Base Catalysis of Novel Zeolite Supported Super—basic Materials ....................................................................................5 Chapter Two: Introduction ............................................................................................6

2.1 Overview ...............................................................................................................7 2.2 An Industrial Application: Production of Polyethelene Napthalate ....................8 2.3 Zeolites as Basic Catalysts..................................................................................12 2.4 Strategy for the Synthesis of a Novel Zeolite Supported Super-base ...............16 2.5 References ...........................................................................................................18

Chapter Three: Experimental Synthesis, Methods, and Results.............................21

3.1 Experimental Synthesis and Methods ................................................................22 3.1.1 Purification of Solvents ...........................................................................22 3.1.2 Synthesis of LTL .....................................................................................22 3.1.3 Alkali-ion Exchange of Zeolite X ...........................................................23 3.1.4 Occlusion of Alkali—metal Oxides ........................................................24 3.1.5 Synthesis of Potassium Azide .................................................................25 3.1.6 Occlusion of Alkali—metal Azides ........................................................26 3.1.7 Alkali—metal Azides Supported on Molecular Sieves..........................29 3.1.8 Semi—batch Bulk-phase Alkenylation and Ethylation Reactions.........29 3.1.9 Semi—batch Supported Alkenylation and Ethylation Reactions ..........31 3.1.10 Gas—phase Alkenylation and Ethylation Reactions..............................32 3.1.11 Gas—phase Isomerization of 1-butene ...................................................35 3.1.12 Characterization .......................................................................................35

3.2 Results .................................................................................................................36 3.2.1 Characterization .......................................................................................36 3.2.2 Semi—batch Bulk-phase Alkenylation...................................................52 3.2.3 Semi—batch Alkenylation over Supported Catalysts ............................54 3.2.4 Gas—phase Alkenylation........................................................................55 3.2.5 Gas—phase Ethylation of Toluene and O-xylene ..................................56 3.2.6 Gas—phase Isomerization of 1-butene ...................................................58

ix3.2.7 Summary of Reactivity Results...............................................................59

3.3 References ...........................................................................................................60 Chapter Four: Discussion and Conclusions ...............................................................63

4.1 Discussion ...........................................................................................................64 4.2 Conclusions .........................................................................................................70 4.3 References ...........................................................................................................73

Part Two: Oxidative Dehydrogenation of Ethane over Partially Reduced Heteropolyanion Catalysts ...........................................................................76 Chapter Five: Introduction ..........................................................................................77

5.1 Introduction .........................................................................................................78 5.2 References ...........................................................................................................80

Chapter Six: Experimental Synthesis, Methods and Results...................................83 6.1 Experimental Synthesis and Methods ................................................................84

6.1.1 MxPMo12Pyr (M = Nb, Mo, V) ............................................................. 84 6.1.2 NbxPMo11VPyr ........................................................................................84 6.1.3 PMMo11Pyr (M = Fe, Ga, Sb, Nb) ..........................................................85 6.1.4 MxP[Fe, Ga, Sb, Nb]Mo11Pyr (M = V, Nb, Sb)......................................86 6.1.5 Nb0.68PW11VPyr.......................................................................................86 6.1.6 Catalytic Studies ......................................................................................88 6.1.7 Characterization .......................................................................................90

6.2 Characterization Results .....................................................................................91 6.2.1 Onset of MoO2 Phase Transition.............................................................91

6.3 Results of Ethane Oxidation ...............................................................................93 6.3.1 Effect of Nb Source .................................................................................93 6.3.2 Effect of Nb/P Ratio ................................................................................93 6.3.3 Effect of Pyridinium ................................................................................98 6.3.4 Effect of Temperature..............................................................................99 6.3.5 Effects of Steam.....................................................................................100 6.3.6 Effects of Ethane:Oxygen Ratio............................................................101 6.3.7 Polyatom Substitution............................................................................102

6.4 Results of Ethylene Oxidation..........................................................................109 6.4.1 Effect of Catalyst Composition .............................................................109 6.4.2 Effect of Nb/P Ratio ..............................................................................112 6.4.3 Effects of Steam.....................................................................................114

6.5 Results of Ethanol Oxidation............................................................................115 6.5.1 Effect of Temperature............................................................................116 6.5.2 Effect of Catalyst Composition .............................................................117

6.6 References .........................................................................................................119 Chapter 7: Discussion, Conclusions, and Recommendations ................................122

7.1 Discussion .........................................................................................................123

x7.2 Conclusions .......................................................................................................132 7.3 Recommendations.............................................................................................134 7.4 References .........................................................................................................136

Chapter 8: Summary and Conclusions........................................................................140

xiLIST OF TABLES

Chapter Two Table 2.1: Properties of PEN and PET Films................................................................9 Table 2.2: Base catalyzed reactions facilitated by alkali—metal modified zeolite supports .......................................................................................................14 Table 2.3: The alkenylation of o-xylene with 1,3-butadiene over alkali—metal occluded zeolite X as reported by Davis and co-workers..........................15 Chapter Three Table 3.1: Results from TGA of occluded alkali—metal azides under nitrogen atmosphere ramping at 1 K/min .................................................................40 Table 3.2: Simulation results for dehydrated NaX zeolite ..........................................45 Table 3.3: Peak positions of 23Na MAS NMR and possible number of unique cation sites determined by 23Na 2D MQMAS NMR in dehydrated NaX, (2)NaN3/NaX, (4)NaN3/NaX, and thermally activated (4)NaN3/NaX......51 Table 3.4: Results of gas phase ethylation over (4)NaN3/NaX for two separate experiments using the same catalyst. The second data set was obtained by increasing the flow of o-xylene during start up ....................................58 Table 3.5: Results of 1-butene isomerization over alkali oxide impregnated zeolite X ..................................................................................................................59 Chapter Six Table 6.1: Comparison of reactivity data from ethane oxidation over Nb0.4PMo11VPyr prepared from a) commercially supplied niobium oxalate, and b) niobium oxalate prepared from niobium pentachloride. STY = space time yield (mmol/min/gcat) ...................................................93 Table 6.2: Reactivity data for ethane oxidation over NbxPMo11VPyr. STY = space time yield (mmol/min/gcat)..........................................................................96

xiiTable 6.3: Reactivity data for ethane oxidation over NbxPMo12Pyr. STY = space time yield (mmol/min/gcat)..........................................................................96 Table 6.4: The effect of temperature on ethane oxidation over Nb0.4PMo12Pyr. STY = space time yield (mmol/min/gcat) .................................................100 Table 6.5: Effect of steam flow on ethane oxidation over Nb0.6PMo12Pyr at constant total flow of 60 mL/min. STY = space time yield (mmol/min/gcat) .......101 Table 6.6: Effect of ethane:oxygen ratio at constant space velocity for ethane oxidation over Nb0.6PMo12Pyr. STY = space time yield (mmol/min/gcat) .........................................................................................102 Table 6.7: The effect of polyatom substitution and cation exchange on ethane oxidation. STY = space time yield (mmol/min/gcat) ...............................104 Table 6.8: The effect of Nb/P and Sb/P on ethane oxidation; * indicates data collected at 400oC reaction temperature...................................................105 Table 6.9: Ethane oxidation over Nb0.5PMo11FePyr for various ethane:oxygen ratios. STY = space time yield (mmol/min/gcat) .................................................108 Table 6.10: Effect of steam flow on ethane oxidation over Nb0.5PMo11GaPyr at GHSV = 2250 h-1. STY = space time yield (mmol/min/gcat) .................108 Table 6.11: Effect of composition on ethylene oxidation at GHSV 2250 h-1. STY = space time yield (mmol/min/gcat) .................................................111 Table 6.12: Effect of Nb/P ratio on ethylene oxidation at GHSV 4500 h-1. Acr A = acrylic acid, MA = maleic acid, STY = space time yield (mmol/min/gcat) .........................................................................................113 Table 6.13: Effect of steam flow on ethylene oxidation at GHSV 4500 h-1 and 300oC (total flow = 60 mL/min). Acr A = acrylic acid, MA = maleic acid, STY = space time yield (mmol/min/gcat).........................................115 Table 6:14: Ethanol oxidation over Nb0.6PMo12Pyr at GHSV 4500 h-1. AcAl = acetaldehyde, EtAc = ethyl acetate, Acr A = acrylic acid, MA = maleic acid, STY = space time yield (mmol/min/gcat).........................................117 Table 6.15: Ethanol oxidation as a function of catalyst composition at GHSV 4500 h-1 and 300oC. AcAl = acetaldehyde, EtAc = ethyl acetate, Acr A = acrylic acid, MA = maleic acid, STY = space time yield (mmol/min/gcat) .........................................................................................118

xiiiChapter Seven Table 7.1: Comparison of ethane and ethylene oxidation catalysts. STY = space time yield (mmol/min/gcat)........................................................................124

xivLIST OF FIGURES

Chapter Two Figure 2.1: Structure of polyethylene naphthalate (PEN) and its precursors dimethyl-2,6-naphthalenedicarboxylate (2,6-NDC) and 2,6-naphthalenedicarboxylic acid (2,6-NDA) in comparison to polyethylene terephthalate (PET).................................................................9 Chapter Three Figure 3.1: X-ray diffraction pattern of synthesized KN3. Asterisks mark peaks matching the standard powder diffraction pattern for KN3 .......................26 Figure 3.2: Synthesis routes for (Y#)M1N3/M2X. Y# denotes the alkali azide loading level. ...............................................................................................28 Figure 3.3: Reaction apparatus for bulk phase semi—batch reactions ........................31 Figure 3.4: Zeolite supported base catalysis apparatus ................................................32 Figure 3.5: Gas phase reaction system with thermocouple locations on heated elements of the reactor apparatus. MFC = mass flow controller, GC = gas chromatograph, Ind = indicating................................................34 Figure 3.6: FTIR spectra of a) (2)NaN3/NaX, b) NaX, c) (4)NaN3/NaX, d) NaN3 in KBr ..............................................................................................................38 Figure 3.7: TGA and IR (inlay) analyses of a) (4)NaN3/NaX, and b) (2)NaN3/NaX c) NaX .................................................................................39 Figure 3.8: Possible anchor structures of metallic sodium clusters in zeolite pores following thermal decomposition of the azide...........................................40 Figure 3.9: FTIR spectrum of (4)NaN3/NaX following azide decomposition at 550oC for 10 hours under flowing helium..................................................41 Figure 3.10: Projection of the cage structure of FAU showing potential cation locations. Site III’ is composed of two slightly non-symmetrical sites; sites III’(1,2) and III’(3) are slightly off center of site III .........................42

xvFigure 3.11: Solid state 23Na MAS NMR of dehydrated NaX zeolite. Asterisks mark spinning sidebands ............................................................................44 Figure 3.12: Simulated 23Na MAS NMR spectrum confirming site assignments. Asterisks mark spinning sidebands on the observed spectrum. The two components of site III, III’(1,2) and III’(3), could not be resolved by simulation....................................................................................................44 Figure 3.13: Solid state 2D MQMAS 23Na NMR spectra acquired from dehydrated NaX zeolite. Asterisks on the projected isotropic axis mark cation sites. The symmetry of the marked sites is determined by examination of the 2D plot along the anistropic axis......................................................46 Figure 3.14: 23Na 1D MAS NMR spectra for a) dehydrated NaX, b) (2)NaN3/NaX, c) (4)NaN3/NaX, and thermally activated (4)NaN3/NaX ..........................47 Figure 3.15: 23Na 2D MQMAS NMR of as made (2)NaN3/NaX showing a decrease in the unique number of cation sites when compared to dehydrated NaX. Asterisks on the projected isotropic axis mark potential uniqe cation sites ...................................................................................................49 Figure 3.16: 23Na 2D MQMAS NMR of as made (4)NaN3/NaX showing a decrease in the unique number of cation sites when compared to dehydrated NaX. Asterisks on the projected isotropic axis mark potential uniqe cation sites ...................................................................................................50 Figure 3.17: 23Na 2D MQMAS NMR of thermally activated (4)NaN3/NaX showing a decrease in the unique number of cation sites when compared to dehydrated NaX. Asterisks on the projected isotropic axis mark potential uniqe cation sites ................................................................51 Figure 3.18: Selectivity versus conversion data for the semi—batch alkenylation of o-xylene with 1,3-butadiene over NaK (22/788, ♦), NaK (44/56, ◊) and K (○) ............................................................................................................53 Chapter Six Figure 6.1: Autoclave engineers reactor system with online HP GCD Plus GCMS...88 Figure 6.2: Flow diagram for Autoclave Engineers reactor system with bypass valve used for ethane, ethylene, and ethanol reactivity studies.................90

xviFigure 6.3: Onset of MoO2 phase transition as measured by TGA-DSC for NbxPMo12Pyr (■) and NbxPMo11VPyr (□) ................................................92 Figure 6.4: Ethane oxidation as a function of Nb/P ratio for a) NbxPMo11VPyr and b) NbxPMo12Pyr; ■ = conversion, ○ = selectivity to COx, Δ = selectivity to ethylene, □ = selectivity to acetic acid ..................................................95 Figure 6.5: Selectivity versus conversion for NbxPMo11VPyr (filled markers) and NbxPMo12Pyr (hollow markers); ●,○ = selectivity to COx, ▲, Δ = selectivity to ethylene, ■,□ = selectivity to acetic acid.................98 Figure 6.6: Space time yield of ethylene in mmol/min/gcat (▲, X = Sb; Δ, X = Nb; ○, X = vanadium) and acetic acid (■, X = Sb; □, X = Nb; ●, X = vanadium)......................................................................................106 Figure 6.7: Ethylene oxidation as a function of Nb/P ratio for NbxPMo12Pyr at 300oC and GHSV 4500 h-1; ■ = conversion, ○ = selectivity to COx, □ = selectivity to acetic acid .....................................................................114 Chapter Seven Figure 7.1: Reaction scheme for the production of ethylene and acetic acid over partially reduced niobium exchanged phosphomolybdic Keggin type heteropolyanions. The major pathway to acetic acid is emphasized by bold arrows................................................................................................131

xviiLIST OF SCHEMES

Chapter Two Scheme 2.1: Sequential production scheme for 2,6-DMN; a) alkenylation, b) cyclization, c) dehydrogenation, d) isomerization. 2,6-DMN is subsequently oxidized to 2,6-NDA ............................................................12 Scheme 2.2: Condensation of SiO4 and AlO4

- tetraheda to form the alumosilicate framework of a zeolite ................................................................................13 Chapter Three Scheme 3.1: Mechanism for the formation of metallic alloys from alkali—metal azides impregnated in faujasite with a different exchange cation. M,C pairs denote (Na, K), (Na, Cs), or (Cs, K) ..........................................................29 Scheme 3.2: Alkenylation of o-xylene with butadiene to give 5-ortho-tolyl-pent-2-ene and heavy byproducts .................................................................................53 Scheme 3.3: Ethylation of o-xylene with butadiene to give mono-, di-, tri-, and tetra-ethylated products...............................................................................57

1

CHAPTER 1

INTRODUCTION AND ORGANIZATION OF THESIS PRESENTATION

2

The work presented in this thesis is the result of two separate and unrelated

projects. Part I of this thesis outlines an investigation into the synthesis and

characterization of a novel zeolite supported super-base capable of carbon-carbon olefin

addition to alkyl aromatics. A zeolite supported basic material capable of such reactions

would benefit many fine chemical syntheses, as well as vastly improve the economics

associated with production of the high performance thermoplastic polyester polyethylene

naphthalate. Although zeolites are well known for their acidic properties, their use as solid

bases is much less widespread, despite the obvious advantages associated with solid versus

homogenous base catalysis.

Chapter 2 presents a brief introduction to zeolites and their use in base catalysis.

The utility of a zeolite supported super-basic material is described in the context of the

industrially relevant reaction of o-xylene and 1,3-butadiene to produce 5-ortho-tolyl-pent-

2-ene. The requirements associated with a super-basic solid catalyst and its synthesis are

presented along with prior art supporting the use of alkali—metal azides as precursors to

alkali—metal occluded zeolites. Finally, a strategy for the creation of a novel zeolite

supported super-basic catalyst is presented.

Chapter 3 explores the experimental methods for occluding alkali—metals within

zeolite X using alkali azide precursors. Synthesis conditions such as method of

impregnation, activation technique, alkali—metal azide/alkali exchanged zeolite X pairing,

3and reactive conditions are described. Characterization showing that the azides are easily

occluded within the pores of zeolite X and reactivity results for base catalyzed reactions

requiring weakly basic materials to very strongly basic materials are presented.

Chapter 4 provides a discussion of the results presented in Chapter 3. The results of

base catalysis are analyzed and conclusions about the use of the alkali—metal azide system

as a route to the reliable synthesis of a zeolite supported super-basic materials are made.

Part II of this thesis describes the use of partially reduced heteropolyanions for the

oxidative dehydrogenation of ethane to ethylene and acetic acid in high yield at

atmospheric pressure and moderate temperature. The syntheses of ethylene and acetic acid

are usually performed in separate steps or at high pressures. Acetic acid is traditionally

synthesized from partially oxygenated precursors such as ethylene, the supply of which is

becoming increasing strained. Ethane, on the other hand, is easily obtainable. Thus, a

catalyst capable of producing ethylene and acetic acid directly from ethane is extremely

valuable.

Chapter 5 introduces the state of the art in ethane and ethylene oxidation to ethylene

and acetic acid, respectively, and describes the utility of the heteropolyanion system for use

in direct ethane oxidation to ethylene and acetic acid. A brief survey of heteropolyanions

in oxidation catalysis is given, including previous work from this group.

Chapter 6 outlines the synthesis of the heteropolyanion materials and the results of

their activity for the oxidation of ethane, ethylene and ethanol. The effects of catalyst

composition, reaction temperature, oxygen to hydrocarbon feed ratio, and water on

catalytic oxidation of ethane, ethylene, and ethanol are investigated in an effort to

determine the nature of the active site on the catalysts.

4 Chapter 7 discusses the results of the reactivity data presented in Chapter 5.

Conclusions and recommendations for further investigation into the active site of the

catalyst are also discussed. Catalytic activity of the heteropolyanion system is compared

with data presented in the literature for the most active ethane and ethylene oxidation

catalysts. The active sites for ethane and ethylene oxidation are discussed and a reaction

pathway for the oxidation of ethane to ethylene and acetic acid is presented based on the

findings of this study.

Chapter 8 provides a summary of the work presented in Parts I and II. The results

of Part I are summarized and followed by a discussion of the feasibility of using alkali—

metal azide precursors for the synthesis of a zeolite supported super—basic catalyst. The

reactivity data collected for the partial oxidation of ethane, ethylene, and ethanol in Part II

are summarized. Conclusions and recommendations for the heteropolyanion systems are

also discussed.