University Code: 10384

Student ID No.:204201411154550

MASTER DEGREE THESIS

Preparation and Application of Catalysts for

Catalytic Wet Air Oxidation of

N,N-dimethylformamide

By

SEAF ADDIN ESHAG YAHYA MOHAMED

(SUDAN）

Supervisor: Bing H. Chen

Major: Chemical Engineering

Date of Graduation: May, 2016

A THESIS SUBMITTEDIN FULFILLMENT OF THE REQUIREMENTS FOR THE

AWARD OF THE DEGREE OFMASTER OF ENGINEERING

DEPARTMENT OF CHEMICAL AND BIOCHEMICAL ENGINEERING

COLLEGE OF CHEMISTRY AND CHEMICAL ENGINEERING

XIAMENUNIVERSITY

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厦门大学博硕士论文摘要库

CERTIFICATION

I, Professor ***, hereby certify that I have read this manuscript and recommend for

acceptance by the Xiamen University a dissertation entitled ……………………in

fulfillment of degree of Master of Engineering at Xiamen University, People’s

Republic of China.

Signed………………

Supervisor

Date………………

Department of Chemical and Biochemical Engineering

College of Chemistry and Chemical Engineering

Xiamen University

Xiamen, Fujian Province

P.R. China

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ORIGINAL STATEMENT

The research described in this thesis Masters of Engineering was conducted under the

supervision of Professor Bing H. Chen at the Department of Chemical and Biochemical

Engineering, Xiamen University. I hereby declare that the work submitted is my own

and that appropriate credit has been given where reference has been made to the work

of others. I also confirm that it has not been previously or concurrently submitted for

any other degree, diploma or any other qualifications at Xiamen University, P.R

China or other institutions.

COPYRIGHT DECLARATION

All rights reserved. No part of this dissertation may be reproduced, stored in any

retrieval system, or transmitted in any form by any means: electronic, mechanical,

photographing, recording or otherwise without prior written permission of the author

or Xiamen University.

___________________________

Date:

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Acknowledgements

I

ACKNOWLEDGEMENTS

I am grateful to my supervisor Professor Bing H. Chen for giving me the

opportunity to work within the field of catalytic wet air oxidation thank you for all the

support and encouragement throughout my postgraduate study.

I wish to thank my colleagues within the research group of CWAO for your

friendship, discussions and the great moments we spent together and for creating the

best possible working environment. Huge thanks as well, go to Jile Fumy co-author

for his support, help, discussion and friendship, thanks my dear.

I have great honor to express my gratitude to the following people, who helped me to

be a part of XMU. Omer hammad, Amir Mahmoud, Abd-alazeem hyder, Mohamed

Damry, Nur-addin, Mohamed Abd-alraheem. I am really proud of you.

I don’t have words to say thank you to my mother Mariam. Her encouragement, faith,

and sacrifice.

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Abstract

II

ABSTRACT

Pd catalyst supported on carbon black BP2000, CeO2, C-CeO2 was prepared by

chemical reduction method for catalytic wet air oxidation (CWAO) applications.

These catalysts were tested in the CWAO of N, N-dimethylformamide aqueous

solutions, a simulated waste water, at 150-180oC under 1.4-2MPa. Different

performances were obtained depending on the catalysts used. 3wt%Pd/C showed poor

activity, but the stability against metal leaching was excellent. However, Pd supported

on metal oxide showed the opposite results. Therefore, 3wt%Pd/20%CeO2/C prepared

by the combination of impregnation (denoted as IM) and chemical reduction (denoted

as CR) methods was applied for CWAO of DMF. The 3wt%Pd/20%CeO2/C-CR

showed high activity as well as excellent stability against leaching. The catalysts were

characterized by, CO-TPR, XPS, XRD, EDS, HADDF-STEM images to determine

the structure of the catalysts and to further understand the different activity of the

catalysts. The results showed that the structure from three layers of Pd, CeO2and C,

was formed, where Pd atoms were located on CeO2 and CeO2 was on carbon. On the

other hand, most of the Pd atoms were located on carbon for 3wt%Pd/20%CeO2/C-IM,

which was the reason for low activity compared to 3wt%Pd/20%CeO2/C-CR. From

XPS result, we found that electrons were transformed from carbon to CeO2, which

protected catalyst 3wt%Pd/20%CeO2/C-CR from metal leaching. Thus,

3wt%Pd/20%CeO2/C-CR is a good candidate for CWAO of DMF.

Keywords: Catalytic wet air oxidation, N,N-dimethylformamide, noble metal, carbon

black, CeO2.

厦门大学博硕士论文摘要库

摘要

III

摘要

Pd 负载在炭黑 BP2000、CeO2 以及 C-CeO2 载体上用于催化湿式氧化过层

（CWAO）。这些催化剂在 150-180 摄氏度，1.4-2.5MPa 氧气下催化湿式氧化处

理 N，N-二甲基甲酰胺（DMF）废水。不同的催化剂有不同的催化性能。3wt%Pd/C

催化剂活性差但稳定性强，然而氧化物载体负载的催化剂则恰恰相反。所以，我

们分别利用化学还原法和浸渍法制备了 3wt%Pd/CeO2/C 催化剂。还原法制备的

催化剂 3wt%Pd/20%CeO2/C-CR 表现出了很高的活性和抗流失性能。为了阐明催

化剂的结构，我们利用 TPR, XPS, XRD, HADDF-STEM 对催化剂进行表征。结

果表明，对于 3wt%Pd/20%CeO2/C-CR 催化剂，Pd 原子几乎都位于 CeO2 上，然

后形成了 Pd，CeO2和 C 的三层结构。而对于 3wt%Pd/20%CeO2/C-IM 催化剂，

大部分的 Pd原子在C上。这就是前者活性高的主要原因。从XPS 结果可以知道，

C 上的电子传递给了 CeO2，从而使得 3wt%Pd/20%CeO2/C-CR 催化剂与 Pd/CeO2

相比有很高抗流失性能。因此，3wt%Pd/20%CeO2/C-CR 催化剂是 CWAO 处理

DMF 废水非常好的选择。

关键字：催化湿式氧化 N，N-二甲基甲酰胺贵金属氧化铈炭黑 CeO2

厦门大学博硕士论文摘要库

Table of Contents

IV

List of Symbols and Abbreviations

AC Active Carbon

AOP Advanced Oxidation

CBC Carbon Black

CNT Carbon Nanotubes

CNW Carbon Nanowires

CR , Chemical Reduction

CWAO Catalytic Wet Air Oxidation

CXb Carbon Xerogel b

DMF N,N-dimethylformamide

ER Eley-Rideal

IARC International Agency for Research on Cancer

IM Impregnation

LHHW Langmuir-Hinshelwood Hougen-Watson

MWCNTc Multi Walled Carbon Nanotube

SWAO Supercritical Wet air Oxidation

WA Wet Air

WAO Wet Air Oxidation

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Table of Contents

V

Table of Content

ACKNOWLEDGEMENTS………………………………………………...….…....I

ABSTRACT………………………………………………………………………….II

摘要…………………………………………………………………………………..III

List of Symbols and Abbreviations………………………………...………………IV

Table of Contents……………………………………………………………..…….V

List of Figures…………………………………………...…………………………VIII

List of Tables………………………………………………………………………..X

Chapter 1 Literature Review …………………………….…………..……………..1

1.1. Introduction…………………………………………………………….…....1

1.2. Wet air oxidation………………………………………………………….....4

1.2.1. Oxygen transfer and solubility during WAO…………………….....……5

1.2.2. Reaction mechanism and Rate Equation in WAO…………….…….…...7

1.2.3. Wet air oxidation kinetics……………..………………………….….…11

1.3. Catalytic wet air oxidation………………………………………..……….12

1.3.1. Homogeneous catalysts……………………………………..…………13

1.3.2. Reaction mechanisms of homogeneous CWAO………………….…….14

1.3.3. Heterogeneous catalysts………………………………………;….…...15

1.3.4. Transition metal and metal oxide catalysts………..………...…;….….....16

1.3.5. Nobel metal…………………………...……………….………;………...18

1.3.6. Carbon materials.................................................................................…...19

1.3.7. Reaction mechanisms of heterogeneous CWAO……..………….………21

1.4. CWAO of N-Containing Compounds…………………..…….…………....22

1.5. Catalytic deactivation…………………………………...…………………...23

1.6. Scope and objective……………………………………...…………………..25

Chapter 2 Materials and Methods…………………………………………….…...26

2.1. Materials chemicals and instruments………..…………………..…………26

2.2. Experiments sections……………………………..………………..…..…….27

2.2.1. Catalyst preparation…………………..………..………………..…………27

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Table of Contents

VI

2.2.2. Catalytic runs…………………….……………...….............……….……..28

2.3. Analysis of aqueous samples………………….…………….................….…28

2.3.1. Total organic carbon (TOC)…………………………………….......……..28

2.3.2. Inductively coupled plasma optical emission spectroscopy (ICP-OES)......29

2.4. Catalyst Characterization………………………...........……………….…...30

2.4.1. X-ray diffraction………………………….……………..………….…...…30

2.4.2. X-ray photoelectron spectroscopy……………………..……….……….....31

2.4.3. Temperature-Programmed Reduction (TPR)……………..…….……...….31

2.4.4. Line-scan analysis……………………………....…..……………………..32

2.4.5. High angle annular dark field-scanning transmission electron microscopy

(HAADF-STEM)…………………………………………………………….………32

Chapter 3 Results and Discussions……………………………….………….….…33

3.1. Catalytic DMF oxidation…………………………..……………….…..…...33

3.2. Temperature Programmed Reduction (TPR)………..……………..….….36

3.2.1. CO-TPR-MASS-signal of H2profiles of CeO2, C.20CeO2, 3Pd/C, 3wt%Pd

/CeO2,3wt%Pd/C-20CeO2-IM, and3wt%Pd/C-20CeO2-CR….………...……........…36

3.2.2. CO-TPR-MASS-signal of CO2profiles of CeO2, C.20CeO2, 3wt%Pd/C,

3wt%Pd/CeO2, 3wt%Pd/C-20CeO2-IM and 3wt%Pd/C-20CeO2-CR…...….……….38

3.3. X-ray photoelectron spectroscopy (XPS)……………….……...………..…41

3.3.1. XPS measurement of O 1s core level of oxygen species on the catalyst

surface for20CeO2/C, C, CeO2……………………………………………….……....41

3.3.2. XPS Ce3d spectra of CeO2 and CeO2-C with different percentage of

CeO2……………………………………………………………………………..…...42

3.4. X-ray Diffraction of C-CeO2 and Pd/C-CeO2……………..………..…..….44

3.5. HADDF-STEM images and Line-scan analysis of 3wt%Pd/20CeO2-C-CR

and 3wt%Pd/20CeO2-C-IM……………………………………………..…….…...46

3.6. Reusability and leaching of the catalysts…………………….……..….…..50

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Table of Contents

VII

Chapter 4 Conclusions and Future Works......................................................…...51

4.1. Conclusions………………………………………………………….………51

4.2. Future Works…………………………………………………………....…….52

References ..........................................................................................................…...53

厦门大学博硕士论文摘要库

List of Figures

VIII

List of Figures

Figure. 1.1. Basic flow diagram of wet air oxidation process………………………...5

Figure 1.2. Simple diagram for WAO kinetic and mechanism…….………………..10

Figure 1.3.Generalized kinetic model for wet oxidation of organic compounds……

………………………………........................................…………………………..…12

Fig. 1.4. Reaction pathway of heterogeneous CWAO………………………….……23

Figure 3.1.CO-TPR-MASS-signal of H2profiles of CeO2, 3wt%Pd/C, 3Pd/CeO2…..

…………………………………………………………………………..……………37

Figure 3.2. CO-TPR-MASS-signal of H2profiles of C.20CeO2, 3wt%Pd/C-20CeO2

-IM and 3wt%Pd/C-20CeO2-CR………………………………………………….….38

Figure 3.3.CO-TPR-MASS-signal of CO2 profiles of CeO2, 3wt%Pd/CeO2….….....39

Figure 3.4.CO-TPR-MASS-signal of CO2 profiles of 3wt%Pd/CeO2,3wt%Pd/C…..39

Figure 3.5.CO-TPR-MASS-signal of CO2 profiles of 20CeO2-C, 3wt%Pd/20CeO2-C-

IM and 3wt%Pd/20CeO2-C-CR .........................…....................................................40

Figure 3.6.XPS O 1s core level of oxygen species on the catalyst surface for 20CeO2

/C, C, CeO2………………………….......................…….…………................................................................…………..42

Figure 3.7.XPS Ce3d spectra of CeO2 and CeO2-C....................................................43

Figure 3.8.XPS Ce3d spectra of C-CeO2with different percentages from CeO2……43

Figure.3.9.XRD Patterns of 10CeO2/C, 20CeO2/C, 30CeO2/C, 40CeO2/C, 50CeO2

/C……………………….............….........……………………………………………44

Figure 3.10.RD Patterns of 3wt%Pd/10CeO2/C, 3wt%Pd/20CeO2/C,3wt% Pd/30Ce

O2/C,3wt%Pd/40CeO2/Cand3wt%Pd/50CeO2/C……...................….....……………45

Figure.3.11.XRD Patterns of 3wt%Pd/20CeO2-C-CR and3wt% Pd/20CeO2-C-IM..46

厦门大学博硕士论文摘要库

List of Figures

IX

Figure.3.12.HADDF-STEM images of 3wt%Pd/20CeO2/C-CR and the corresponding

elemental mapping results……………………………………………………………47

Figure.3.13. Line-scan analysis of 3wt%Pd/20CeO2/C-CR……………….………...48

Figure.3.14.HADDF-STEM images of 3wt%Pd/C-20CeO2-IM and the corresponding

elemental mapping results…………………………………………………………....49

Figure.3.16.Catalyst stability……………………………………………………...…50

厦门大学博硕士论文摘要库

List of Tables

X

List of Tables

Table 1.1. Heterogeneous metal catalysts used in CWAO of organic compounds and

industrial wastewaters………………………………………………………………..18

Table 1.2. Carbon materials as catalysts and their supports in CWAO……………...20

Table2.1.Materials and chemicals used in the study…………………………………26

Table 2.2. Types and manufactures of instruments…………………………………………..27

Table3.1.TOCconversion% and metal leaching% for our catalysts…...….…………34

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______________________ Chapter 1 Literature Review

1

Chapter 1 Literature Review

1.1. Introduction

Water is the lifeblood and is a scarce natural resource present on earth. It covers

more than 70% of the Earth's surface. Currently half of the fresh water is appropriate

for human uses indicating a high level of utilization and contamination of the existing

water resource. During the extensive exploitation of the available fresh water resource

by human activities, water pollution may occur from so-called point or non-point

sources. Point sources of water pollution occur when hazardous or toxic substances

are discharged directly into the body of water at a single point of discharge. Most

industrial effluents are considered as a point source of water pollution. A non-point

source on the other hand, arises from a wide range of unspecified area, which makes

water pollution difficult to control. For example fertilizers and pesticides washed out

from agricultural fields by rain fall are considered as a non-point source of water

pollution.

Wastewater coming from a point source can be classified into four broad categories,

according to its origin: domestic, industrial, public and service system loss. All this

polluted water, irrespective of its source has a heterogeneous compositions, which

however can be characterized by the following main groups: Suspended solids,

Dissolved inorganic compounds and heavy metals, Biodegradable organics and

nutrients, on-biodegradable organics and pathogens.

In particular, wastewater with high organic loads (degradable and non-degradable

bio-toxic organics) and/or inorganic hazardous compounds resulting from numerous

industrial activities has become a worldwide concern for conventional wastewater

treatment facilities. Within this context, the importance of refractory and bio toxic aro

厦门大学博硕士论文摘要库

Chapter 1 Literature Review

2

-matics compounds such as phenol and substituted phenols has to be highlighted[1].

N, N-dimethylformamide (DMF) is a colorless, a powerful polar aprotic solvent,

hygroscopic liquid with a slight amine odor, which odor is due to trace amounts of

dimethylamine. The rate of hydrolysis in the absence of catalysts and at ambient

temperature is quite slow. Therefore DMF is commonly used in the production of

wide range of organic chemicals and polymers, including polyurethane synthetic

leather, dyes, pharmaceuticals, pesticides, polyimide resins, synthetic fibers and

polymeric membranes. It is also used as an extraction agent in the petrochemical

industry.

The global production of DMF was estimated about 270,000 tons per year in 1994

and since then there has been an increasing demand in the production. DMF is

commonly found in high concentrations in many industrial wastewaters. In China

alone the emission amount of DMF wastewater from leather factories is up to 1 billion

tons a year.

The biological studies have shown that inhalation or dermal absorption of DMF in

humans causes gastric irritation, pancreatic disorder and hepatotoxicity. In 1989,

DMF was classified in group 2B (possibly carcinogenic to humans) by International

Agency for Research on Cancer (IARC) of the World Health Organization, DMF is

also known to have adverse impacts on the environment. The pure liquid is kinetically

stable to its boiling point, yet its decomposition is catalyzed by strong bases and some

transition metals, which is also susceptible to photochemical degradation[2-5].

Nowadays wastewater has become a major social and economic problem. Also,

health-quality standards and environmental regulations have gradually become more

restrictive. Innovative technologies become important for water purification and recyc

厦门大学博硕士论文摘要库

Chapter 1 Literature Review

3

-ling industrial waste water. Up to date, the most common abatement technology for

organic pollutant is the conventional biological treatment. Nevertheless, it is an

extremely slow process and produces large volumes of sewage sludge that have to be

disposed off by land fill or incineration, the latter being a costly process. Moreover, it

may be unsuitable for wastewater that is too concentrated, toxic or refractory to

microbial actions[6-8]. Another well-known non-reactive wastewater treatment is

active carbon adsorption. Active carbon can effectively remove a wide range of

organic pollutants from wastewater streams by physical adsorption [2, 8].

Several oxidative techniques such as incineration, catalytic and non-catalytic wet

air oxidation (WAO), supercritical wet air oxidation (SWAO) and more recently

advanced oxidation (AOP) have been considered as efficient treatment techniques for

refractory industrial wastewater. Among them, the incineration of toxic organic wastes

is well established. It can destroy the pollutant completely, though, at high-energy

demand due to application of excessive temperatures (1000 to 1700oC)[9, 10].In

addition, in case of chlorinated compounds, even more toxic chemicals than the parent

pollutant, such as dioxins and furans can be formed in the cooling section after the

combustion.

Advanced oxidation processes (AOP), which use strong oxidants, O3 or H2O2, in

combination with UV is an emerging oxidative treatment at ambient conditions. This

process is mainly based on the presence of highly reactive radical’s species such as

OH radical, which can oxidize a wide range of organic pollutants due to its high

oxidation potential. Nevertheless, the efficiency of AOP is restricted by several

disadvantages: only treatment of low pollutant concentration, use of expensive

oxidants and energy source for UV assisted AOP and need separation of iron after the

reaction for Fenton’s process[11].

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Degree papers are in the “Xiamen University Electronic Theses and

Dissertations Database”.

Fulltexts are available in the following ways:

1. If your library is a CALIS member libraries, please log on

http://etd.calis.edu.cn/ and submit requests online, or consult the interlibrary

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