Synthesis of Aromatic Dibenzyl Disulfide using H2S and Solid Reusable Resin as Catalyst

64 Pages·2014·1.7 MB·English

“Synthesis of Aromatic Dibenzyl Disulfide using H S and Solid
2
Reusable Resin as Catalyst”

Thesis Submitted by

DOROTHY CHETIA (212CH1496)
In partial fulfillment for the award of the Degree of
MASTER OF TECHNOLOGY
IN
CHEMICAL ENGINEERING

Under the guidance of
Dr. SUJIT SEN

DEPARTMENT OF CHEMICAL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY
ROURKELA-769008
May, 2014
CERTIFICATE
This is to certify that the thesis entitled “Synthesis of Aromatic Dibenzyl Disulfide using H S and Solid
2
Reusable Resin as Catalyst”, submitted by Dorothy Chetia (212CH1496) to National Institute of Technology
Rourkela, in fulfillment of the requirements of the degree of Master of Technology in Chemical Engineering is a
bonafide record of the research work carried out by her, in the Department of Chemical Engineering, National Institute
of Technology, Rourkela under my supervision and guidance. Miss Dorothy has worked on this topic from July, 2013
until May, 2014 and the thesis, in my opinion, is worthy of consideration for the award of the degree of “Master of
Technology” in accordance with the regulations of this Institute. The results embodied in the thesis have not been
submitted to any other University or Institute for the award of any degree or diploma.

Date: 23 May 2014
Dr. Sujit Sen

Department of Chemical Engineering

National Institute of Technology
Rourkela, Orissa-769008
ACKNOWLEDGEMENT

I wish to express my heartily gratitude to my guide Dr. Sujit Sen for his valuable guidance
with constant flow of existing new ideas and contagious enthusiasm through my work. My
association with my guide will remain a memorable part of my life. I want to thank sir for
constantly motivating me through him valuable counsel as well as excellent tips to build my
research and writing skills.

I want to acknowledge the support and encouragement given by Priya Nakade, Ujjal
Mondal and Gaurav Singh throughout the period of my work.

I also take this opportunity to express my sincere thanks to Dr. R. K. Singh, Head of
Department of Chemical Engineering for making available necessary facilities to complete this
research work. I am also grateful Dr. B. Munshi and all other faculty members of department for
their help whenever sought for.

I am obliged to all my friends for their friendships and encouragements. Finally, the thesis
would not have been completed without the support of the most important people in my life − my
family. I sincerely wish to thank my parents, for their unconditional love and constant
encouragement.

Date- 23/05/2014 DOROTHY CHETIA
(212CH1496)
LIST OF FIGURES
Fig. No. Caption Page No.
Fig. 1.1 Structural formulas of different Alkanolamines 5
Fig. 1.2 Flow diagram of Amine treating process 8
Fig. 1.3 Process flow diagram of Sulfur Recovery unit 9
Fig. 1.4 Stark’s Mechanism 13
Fig. 1.5 Brandstorm Montanari Mechanism 13
Fig. 1.6 Schematic diagram of classification of PTC 14
Fig. 1.7 Two distinct mechanisms for solid liquid are
(a) Heterogeneous solublization, (b) Homogeneous solublization 15
Fig. 1.8 Activity of liquid-liquid-solid tri-phase catalysis 18
Fig. 1.9 Ion exchange resin 19
Fig. 3.1 Schematic diagram for the absorption of H S in MEA solution 26
2
Fig. 3.2 Schematic diagram of Batch reactor 27
Fig. 3.3 A Gas Chromatography 30
Fig. 3.4 (i) Chromatogram at 5 min 31
Fig. 3.4 (ii) Chromatogram at 480 min 31
Fig. 4.1 Mechanism 33
Fig. 4.2 Effect of speed of agitation 34
Fig. 4.3 Effect of elemental sulfur loading 35
i
Fig. 4.4 Effect of Temperature 36
Fig. 4.5 Arrhenius plot for Activation energy 37
Fig. 4.6 Effect of catalyst loading 38
Fig. 4.7 Plot of natural logarithm of initial rate versus the natural logarithm
of catalyst concentration 39
Fig. 4.8 Effect of concentration of Benzyl Chloride 40
Fig. 4.9 Effect of sulfide concentration 41
Fig. 4.10 Mechanism of Triphase Catalysis 43
Fig. 4.11 Conversion of Benzyl Chloride 44

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LIST OF TABLE
Table No. Caption Page No.
Table 1.1: Advantages and Disadvantages of MEA 6
Table 1.2: Advantages and Disadvantages of DEA 6
Table 1.3: Advantages and Disadvantages of MDEA 7
Table 1.4: Various commonly used PT catalyst 16

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LIST OF ABBREVIATIONS

PTC Phase Transfer Catalysis
BC Benzyl Chloride
BM Benzyl Mercaptan
DBS Dibenzyl Sulfide
DBDS Dibenzyl Disulfide
DEA Diethanolamine
DIPA Diisopropanoloamine
GLC Gas Liquid Chromatography
MDEA Methyldiethanolamine
MEA Monoethanolamine
OVAT One variable at a time
ppm Parts per million
TEA Triethanolamine TPC Tri Phase Catalyst

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ABSTRACT
During hydro desulfurization or hydro treatment of crude oil in petroleum refineries, one
or more gaseous by products are produced with hydrogen sulfide (H S) infused into it. Since the
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presence of H S, corrodes the process equipment and is highly toxic to the environment, it is
2
eliminated from the gas stream and transformed into harmless forms. In general, H S from gas
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stream is removed using amine treating unit and is treated in the Claus unit for the production of
elemental sulfur. This elemental sulfur is used mostly to produce sulphuric acid and also in rubber
industries. But in Claus process valuable hydrogen energy is lost and requires exact process control
over ratio of oxygen to hydrogen sulfide feed. Therefore, an alternative process which could
transform H S to valuable chemicals, is greatly welcome in the process industry in improving the
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sulfur disposal problem. H S laden gas can be used in a more beneficial way by absorbing into
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aqueous alkanolamine like monoethanolamine (MEA) and then use this reagent to produce fine
chemicals like disulfides, thioether, mercaptans, , amines etc., which have high usability and good
market value. These organo-sulfide such as Dibenzyl disulfide (DBDS) find their application in
manufacturing corrosion inhibitors, fragrance compounds, high pressure lubricant additives and
other organic compounds. Since the alkanolamine phase and the organic phase are not miscible,
to carry out this biphasic reaction, phase-transfer-catalyst (PTC) has been tired out a few times and
often the application of PTC gives enhancement in reaction rate, more conversion for reactants
and better selectivity of desired products.
This work was carried out to study the synthesis of fine chemicals like Dibenzyl Disulfide
(DBDS) and using H S-rich monoethanolamine (MEA) and benzyl chloride (BC) under Liquid-
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Liquid-Solid phase transfer catalysis with a tri-phase catalyst. Owing to its solid state, availability,
cost and reusability, Amberlite IR 400 is selected as a PTC. A parametric study was carried out
which emphasized upon the impact of catalyst loading as one of the process variables on the
conversion of benzyl chloride and selectivity of DBDS and parametric study with these substances
revealed 100 % selectivity for desired product at ambient condition. The effects are utilized to
establish a suitable mechanism of the reaction to explain the course of the reaction. The overall
objective of this study is to maximize conversion of reactant BC and selectivity of DBDS.

Keywords: Hydrogen Sulfide; Alkanolamines; Dibenzyl Disulfide; Liquid-Liquid-Solid Phase
Transfer Catalysis; Mechanism; Selectivity; Conversion.
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CONTENTS
Title Page
Certificate by the Supervisor
Acknowledgement
List of Figures i
List of Tables iii
List of Abbreviations iv
Abstract v
Contents vi

Chapter 1 Introduction 1-19
1.1 Source of Hydrogen Sulfide 1
1.2 Reasons for removal of H S 2
2
1.3 Industrial Process for removal and recovery of H S 3
2
1.3.1 Ammonia based process 3
1.3.2 Alkanolamine process 4
1.3.3 Types of amines: Advantages & Disadvantages 6
1.3.4 Process 7
1.4 Claus process of Sulfur recovery from H S gas 8
2
1.5 Other ways to process sour gas 10
1.5.1 CrystaSulf 10
1.5.2 Wet Oxidation Lo-Cat process 11
1.6 Present Work 11
1.7 Phase Transfer Catalysis 12
1.7.1 Mechanism of PTC 12
1.7.2 Major classification of PTC 13
1.7.3 Types of Phase Transfer Catalyst 15
1.7.4 Choice of Immobilized PTC 17
1.7.5 Tri-phase transfer catalysis 17
1.7.6 Catalyst used in tri-phase catalysis 18
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Chapter 2 Literature Survey 20-24
2.1 Use of aqueous alkanolamines for the removal of H S 20
2
2.2 Liquid-Liquid Phase Transfer Catalysis 20
2.3 Synthesis of Dibenzyl-Disulfide 21
2.4 Use of Triphase catalyst 22
Chapter 3 Experimental Setup 25-31
3.1 Chemicals 25
3.2 Preparation of H S-rich aqueous alkanolamine 25
2
3.3 Equipment 26
3.4 Experimental procedure 27
3.5 Method of Analysis 28
3.5.1 Determination of Sulfide concentration 28
3.5.2 Analysis of Organic Phase 29
Chapter 4 Reaction of Benzyl Chloride with H S-rich aqueous mono-etha
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-nolamine under liquid-liquid-solid phase transfer Catalysis 32-44
4.1 Introduction 32
4.2 Results and Discussion 33
4.2.1 Effect of Speed of Agitation 33
4.2.2 Effect of elemental sulfur loading 34
4.2.3 Effect of temperature 35
4.2.4 Effect of catalyst loading 37
4.2.5 Effect of concentration of benzyl sulfide 39
4.2.6 Effect of sulfide concentration 40
4.3 Mechanistic Investigation 41
4.3.1 Mechanism of Triphase Catalysis 41
4.4 Recycle and reusability of catalyst 43
Chapter 5 Summary and Conclusions 45-46
5.1 Conclusion 45
5.2 Future Work 46
5.2.1 Finding out Effect other parameters 46
References 47
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