MCM-41 SUPPORTED Nio-Moo3 CATALYSTS for HYDRODENITROGENATION of SIMPLE AMINES

MCM-41 SUPPORTED NiO-MoO3 CATALYSTS FOR HYDRODENITROGENATION OF SIMPLE AMINES

A THESIS

Submitted by

S.J. SARDHAR BASHA

in fulfilment for the award of the degree

DOCTOR OF PHILOSOPHY

FACULTY OF SCIENCE AND HUMANITIES

ANNA UNIVERSITY : CHENNAI – 600 025

MAY 2006

ANNA UNIVERSITY : CHENNAI 600 025

BONAFIDE CERTIFICATE

Certified that this thesis titled “MCM-41 SUPPORTED
NiO-MoO3 CATALYSTS FOR HYDRODENITROGENATION OF SIMPLE AMINES” is the bonafide work of
Mr. S.J. SARDHAR BASHA who carried out the research under my supervision. Certified further, that to the best of my knowledge the work reported herein does not form part of any other thesis or dissertation on the basis of which a degree or award was conferred on an earlier occasion on this or any other candidate.

Place : Chennai

Date :

ABSTRACT

In an oil refinery, oil is distilled into several fractions, including naphtha and gas oil. These fractions must be purified to diminish the contents of sulfur, nitrogen and metals so that the air-polluting emissions levels of sulfur and nitrogen oxides are minimized formed when these oil fractions are burned in cars and trucks. Furthermore, most catalysts used in a refinery for the processing of oil fractions cannot tolerate sulfur, nitrogen and metals. The removal of sulfur, nitrogen and metals are performed in so-called hydrotreating processes in which the feedstock reacts with hydrogen in the presence of a catalyst.

Over the years, considerable effort has been devoted to the study of the properties of alumina supported, sulfided cobalt-molybdenum,
nickel-molybdenum and nickel-tungsten catalysts. This has included the attempts to define the active catalyst species, the role of promoters, the influence of preparation and activation conditions, etc. The origin of the exclusive use of alumina can be ascribed to its outstanding textural and mechanical properties and its relatively low cost. One important factor also is the ability to regenerate catalytic activity after intensive use under hydrotreating conditions. Due to the necessity to develop hydrotreating catalysts with enhanced properties, other supports have been studied

In order to improve the activity and to reduce the severity of experimental conditions, several approaches have been pursued. One such approach is to choose proper support for the active components. After the discovery of mesoporous materials, MCM-41 has received increasing attention due to its very high surface area and regular pore dimensions. MCM-41 aluminosilicate favors a high dispersion of the active species while increasing the accessibility of the large molecules of the gas feed containing heteroatoms to the catalytic active sites.

The aim of the present investigation was to remove nitrogen using
H-AlMCM-41 as a support for NiO-MoO3 catalyst. This material has been used as support for NiO-MoO3 catalysts. H-AlMCM-41 was impregnated with Mo and Ni precursor salts by sequential impregnation method. The compositions of the catalysts were chosen as 12, 18, 24 and 30 wt.% of MoO3 with constant amount of 7 wt.% NiO. These supported catalysts were characterized using XRD, N2 adsorption–desorption studies, ICP-AES elemental analysis, TGA, SEM, FT-Raman spectroscopy, UV–Vis DRS and FT-IR spectra of CO adsorption measurements to confirm their crystallinity, textural properties, coordination environment and fine dispersion of metal oxides over the support surface. HDN of o-toluidine (OT) and cyclohexylamine (CHA) were performed with various metal loadings to choose the optimum metal loading for these reactions. An activity data show an enhanced performance with respect to the MoO3 loading. An optimum metal loading of 24% MoO3 has been chosen to study all the
experiments. The order of activity of the catalyst was 7% NiO – 24% MoO3 > 7% NiO – 18% MoO3 > 7% NiO – 30% MoO3 > 7% NiO – 12% MoO3 /H-AlMCM-41 (100)

The NiO-MoO3/H-AlMCM-41 catalysts were prepared by different procedures like co-impregnation and by sequential impregnation method (normal order and reverse order). These materials were characterized by TEM, XRD, N2 adsorption-desorption studies, XPS and FT-IR spectra of CO adsorption studies. The activity of these catalysts was tested for HDN of OT and CHA. Reverse order impregnated catalyst (24%MoO3-7%NiO) shows higher activity than other catalysts. This may be due to the fine dispersion of the active metal species and complete reduction of metal oxide to its lower oxidation state. The activity of the catalysts followed the order 24 wt.% MoO3 – 7 wt.% NiO > 7 wt.% NiO – 24 wt.% MoO3 > (7 wt.% NiO.24 wt.% MoO3). The reverse order of impregnation of MoO3 and NiO was chosen for further studies.

24 wt.% MoO3 and 7 wt.% NiO were sequentionally deposited over
MCM-41 with different Si/Al ratio supported catalysts by reverse order impregnation. Cetyltrimethylammonium bromide was used as the
structure-directing agent for AlMCM-41 synthesis. The materials were characterized by XRD, ICP-AES elemental analysis, SEM,
N2 adsorption–desorption studies, TPD of ammonia using adsorption techniques, UV–Vis DRS, MAS NMR and CO adsorption of FT-IR. XRD of the catalysts clearly show the crystallinity and the phase formation with respect to NiMoO4, MoO3 and NiO. 27Al MAS NMR of AlMCM-41 (100) shows a single peak at 50.85 indicating the presence of aluminium exclusively in the framework further indicating the complete absence of non-framework aluminium. Hence, higher Si/Al ratio was observed to be better for incorporating aluminium exclusively in the framework. The dispersion of metal oxide over support was calculated by FT-IR of CO adsorption.

HDN of aromatic amines and aliphatic amines like OT and CHA respectively, were tested over these catalysts. The aliphatic amines show higher HDN activity than the aromatic amines. Aliphatic amines were found to readily undergo HDN compared with the aromatic amines.

HDN of OT was also tested over different supported metal catalysts such as MCM-41, HZSM-5 and γ-Al2O3 to understand the efficiency level of MCM-41 supported MoO3-NiO. MCM-41 supported MoO3-NiO catalyst showed higher activity compared to the other catalysts which might be due to its high surface area and mild acidity.

ACKNOWLEDGEMENT

It is a great privilege for me to be a student of Dr. K. SHANTHI, Assistant Professor, Department of Chemistry, Anna University, who has suggested the problem, offered constructive criticism and encouragement at every stage of my research work. I pay my gratitude to her, in particular for her valuable guidance, her meticulous attention to this work and her exemplary editing of thesis.

My special thanks to Dr. S. NANJUNDAN, Professor and Head, Department of Chemistry, Anna University for the permission to avail the laboratory facilities. I wish to place on record my sincere thanks to
Dr. M. PALANICHAMY, Professor in Chemistry, Anna University, Chennai, for his valuable suggestions rendered during the course of
my work. My sincere thanks to my doctoral committee members
Dr. T. K. VARADHARAJAN and Dr. G. RANGA RAO, IIT, Madras for their valuable suggestions and encouragement throughout my research career.

I take this opportunity to thank all my seniors, research colleagues and friends for their fullest cooperation throughout the tenure of this work. I sincerely thank the non-teaching staff members for their help and support. I express my deepest appreciation to my parents and brother for their continuous support and constant encouragement throughout the period of this work.

S. J. SARDHAR BASHA

TABLE OF CONTENTS

CHAPTER No. TITLE PAGE No.

ABSTRACT iii

LIST OF TABLES xii LIST OF FIGURES xiii

LIST OF SYMBOLS AND ABBREVIATIONS xvii

1 INTRODUCTION 1

1.1 PETROLEUM REFINING IN PETROLEUM

INDUSTRY 1

1.1.1 Important catalytic processes in

petroleum refineries 3

1.1.1.1 Catalytic Cracking 3

1.1.1.2 Catalytic reforming 4

1.1.1.3 Hydrocracking 5

1.1.1.4 Hydrotreating 6

1.2 NITROGEN CONTAINING COMPOUNDS

IN PETROLEUM CRUDE 9

1.3 CHEMISTRY OF HYDRODENITRO-

GENATION 9

1.4 EFFECT OF PARTIAL PRESSURE OF

HYDROGEN ON HYDRODENITRO-

GENATION REACTION 15

1.5 EFFECT OF MoO3 LOADING ON SUPPORT

FOR HYDROTREATING PROCESS 17

CHAPTER No. TITLE PAGE No.

1.6 METAL OXIDES AS CATALYSTS FOR

HYDROTREATING PROCESS 18

1.7 METAL CARBIDES AND METAL

NITRIDES AS CATALYSTS FOR HDN 20

1.8 PHOSPHORUS AS A PROMOTER FOR

HDN CATALYST 21

1.9 FLUORINE AS A PROMOTER FOR

HDN CATALYST 22

1.10 SUPPORT EFFECT ON

HYDROTREATING PROCESS 23

1.10.1 Silica 24

1.10.2 1.10.2 Carbon 24

1.10.3 Oxides as support 26

1.10.3.1 Titania and Zirconia 26

1.10.4 Clays 29

1.10.5 Zeolites as support 31

1.10.6 Mesoporous MCM-41 as support 34

1.11 SCOPE OF THE PRESENT STUDY 39

2 EXPERIMENTAL 41

2.1 CHEMICALS 41

2.2 SYNTHESIS OF SUPPORT 42

2.2.1 Synthesis of H-AlMCM-41

support 42

2.2.2 Synthesis of SiMCM-41 support 42

2.2.3 Synthesis of γ-Al2O3 support 43

2.2.4 Synthesis of HZSM-5 support 44

CHAPTER No. TITLE PAGE No.

2.3 PREPARATION OF CATALYSTS 45

2.3.1 Preparation of MCM-41

supported NiO-MoO3 catalyst 45

2.3.2 Preparation of γ-Al2O3 and HZSM-5

supported NiO-MoO3 catalyst 46

2.4 PRETREATMENT OF CATALYSTS 46

2.5 CHARACTERIZATION OF THE

CATALYSTS 46

2.5.1 X-ray diffraction (XRD) 46

2.5.2 Textural Analysis 47

2.5.3 Thermal Analysis 47

2.5.4 ICP-AES 48

2.5.5 Temperature – Programmed

Desorption of Ammonia 48

2.5.6 Nuclear Magnetic Resonance 48

2.5.7 Scanning Electron Microscope 49

2.5.8 FT-Raman Spectroscopy 49

2.5.9 Diffuse Reflectance Spectroscopy

(DRS) 49

2.5.10 Fourier-Transform Infrared

Spectroscopy of CO adsorption 50

2.5.11 Transmission Electron Microscopy

(TEM) 50

2.5.12 X-ray Photoelectron Spectroscopy

(XPS) 51

2.6 ANALYSIS OF SULFUR 51

CHAPTER No. TITLE PAGE No.

2.7 FLOW UNIT FOR CATALYST

ACTIVITY MEASUREMENT 53

2.8 PRODUCT ANALYSIS 55

3 RESULTS AND DISCUSSION 57

3.1 EFFECT OF MoO3 LOADING ON

THE HDN ACTIVITY OF NiO-MoO3/

H-AlMCM-41 SUPPORTED CATALYST 57

3.1.1 Characterization 57

3.1.2 Hydrodenitrogenation activity 69

3.1.3 Effect of Reaction time on the

HDN activity 70

3.1.4 Correlation of HDN activity with the

physico-chemical properties of

the catalysts 75

3.2 INFLUENCE OF THE ORDER OF

IMPREGNATION AND METHOD

OF PREPARATION OF NiO-MoO3/H-

AlMCM-41 CATALYSTS ON THE

HDN ACTIVITY 77

3.2.1 Study of physico-chemical

properties 78

3.2.2 Hydrodenitrogenation activity 92

3.2.3 Correlation of HDN activity with

surface properties of the catalysts 97

3.2.4 Effect of presulfidation on the

HDN activity of the catalyst 99

CHAPTER No. TITLE PAGE No.

3.3 EFFECT OF Si/Al RATIO ON HDN

REACTION OVER H-AlMCM-41

SUPPORTED NiO-MoO3 CATALYSTS 101

3.3.1 Characterization 101

3.3.2 Hydrodenitrogenation of OT and

CHA on various AlMCM-41

supported NiO-MoO3 catalysts 113

3.4 INFLUENCE OF SUPPORT ON

NiO-MoO3 CATALYST FOR HDN 116

4. SUMMARY AND CONCLUSION 118

REFERENCES 123

LIST OF PUBLICATIONS 138

VITAE 140

LIST OF TABLES

TABLE No. TITLE PAGE No.

1.1 Consumer products from a petroleum

refinery and their characteristics 3

1.2 Nitrogen and Sulfur content present in

different crude 8

1.3 Typical nitrogen compounds present in

petroleum crude 10

3.1 Textural and structural characteristics of

AlMCM-41 and 7 wt.% NiO-x wt.%MoO3/

H-AlMCM-41 60

3.2 Textural and structural characteristics of

H-AlMCM-41 and its supported catalysts 82

3.3 XPS binding energies (eV) and its

corresponding wt.% of peak area and the

atomic surface concentration

of Mo (CMo) and Ni (CNi) 84

3.4 Various oxidation states present in NiO-MoO3/

H-AlMCM-41 catalysts 85

3.5 Textural and structural characteristics of

MCM-41 and its supported catalysts 104

3.6 Acidity of H-AlMCM-41 measured by STPD

of ammonia from 353 - 723 K 105

3.7 HDN activity and textural characteristics of

different support and supported catalysts 117

LIST OF FIGURES

FIGURE No. TITLE PAGE No.

1.1 Quinoline reaction network 12

1.2 Indole reaction network 13

2.1 Flow unit for catalytic reactions at atmospheric

pressure 54

3.1 X-ray diffractograms of (a) Protonated

AlMCM-41, (b) Calcined AlMCM-41 and

3.2 N2-Adsorption-Desorption isotherm of

AlMCM-41 59

3.3 TGA and DTA curves of mesoporous molecular

sieve for as-synthesized sample of
AlMCM-41 (100) 61

3.4 X-ray diffractograms of 7 wt.% NiO-x wt.% MoO3/

H-AlMCM-41 x = (a) 12, (b) 18 and (c) 24 63

3.5 X-ray diffractogram of 7 wt.%NiO-30 wt.%MoO3/

H-AlMCM-41 63

3.6 SEM pictures of (a) AlMCM-41 (100) and

(b) 7 wt.% NiO-24 wt.% MoO3/H-AlMCM-41 65

3.7 FT-Raman spectra of 7 wt.% NiO-x wt.%

MoO3/H-AlMCM-41 (a) 18, (b) 24, (c) 12 and

(d) 30 66

3.8 Diffuse reflectance spectra of 7 wt.% NiO-x wt.%

MoO3/H-AlMCM-41 (a) 24, (b) 18, (c) 12 and (d) 30 68

FIGURE No. TITLE PAGE No.

3.9 FT-IR spectra of CO adsorbed on reduced

(a) 7 wt.% NiO-18 wt.% MoO3/H-AlMCM-41 and

(b) 7 wt.% NiO-24 wt.% MoO3/H-AlMCM-41

catalysts 68

3.10 Effect of MoO3 loading on the catalytic activity

for the HDN of o-toluidine 71

3.11 Effect of MoO3 loading on the catalytic activity
for the HDN of cyclohexylamine 72

3.12 Effect of reaction time on the catalytic activity
for the HDN of o-toluidine 73

3.13 Effect of reaction time on the catalytic activity
for the HDN of cyclohexylamine 74

3.14 TEM images of reduced H-AlMCM-41 supported

catalysts (a) (7 wt.% NiO.24 wt.% MoO3),

(b) 7 wt.% NiO-24 wt.% MoO3 and

3.15 X-ray diffractograms of H-AlMCM-41

supported catalyst (a) (7wt.% NiO.24wt.% MoO3),

(b) 24wt.% MoO3-7wt.% NiO and

3.16 XPS spectrum of Mo 3d region for reduced

7 wt.% NiO-24 wt.% MoO3/H-AlMCM-41 catalyst 83

3.17 XPS spectrum of Mo 3d region for reduced

(7 wt% NiO.24 wt.% MoO3)/H-AlMCM-41 catalyst 87

3.18 XPS spectrum of Mo 3d region for reduced

24 wt.% MoO3-7 wt.% NiO/H-AlMCM-41 catalyst 87

3.19 XPS spectrum of Ni 2p region for reduced

7 wt.% NiO-24 wt.% MoO3/H-AlMCM-41 catalyst 88

FIGURE No. TITLE PAGE No.

3.20 XPS spectrum of Ni 2p region for reduced

(7 wt.% NiO.24 wt.% MoO3)/H-AlMCM-41 catalyst 88

3.21 XPS spectrum of Ni 2p region for reduced

24 wt.% MoO3-7 wt.% NiO/H-AlMCM-41 catalyst 89

3.22 FT-IR spectra of CO adsorbed on reduced

(a) (7wt.% NiO.24wt.% MoO3)/H-AlMCM-41,

(b) 7wt.% NiO-24wt.% MoO3/H-AlMCM-41 and

3.23 Influence of the impregnation method

on the catalytic activity for the HDN of o-toluidine 93

3.24 Influence of the impregnation method

on the catalytic activity for the HDN
of cyclohexylamine 94

3.25 Effect of reaction time on the catalytic activity
for the HDN of o-toluidine 95

3.26 Effect of reaction time on the catalytic activity

for the HDN of cyclohexylamine 96