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  3. Fabrication and characterization of nanotitania-based photocatalysts for desulfurization of the sulfur-resistant compound dibenzothiophene

Fabrication and characterization of nanotitania-based photocatalysts for desulfurization of the sulfur-resistant compound dibenzothiophene

Number of pages: 249 File Format: word File Code: 31890
Year: 2014 University Degree: Master's degree Category: Chemical - Petrochemical Engineering
Tags/Keywords: Catalyst - Desulfurization - Dibenzothiophene - Diesel - GC-MS - Nanotitania - Nanozeolite - nickel - Photocatalyst - Titanium dioxide
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  • Summary of Fabrication and characterization of nanotitania-based photocatalysts for desulfurization of the sulfur-resistant compound dibenzothiophene

    Dissertation for receiving a Master's degree ((M.Sc))

          Major: Applied Chemistry

     

    Persian summary

    According to international standards, sulfur in the fuels used in the transportation industry and As one of the most important polluting industries, transportation should be reduced to about 10 ppmw, while many refineries in the world produce fuels with sulfur content of more than 1000 ppmw. One of the new and cost-effective ways to reduce sulfur among all the existing methods is photocatalytic oxidation. designed, fabricated and analyzed using XRD, XRF, FESEM, EDXA, TEM and BET/BJH characterization techniques. The zeolite base used in the construction of most photocatalysts is fugasite nanozeolite NaX, which is synthesized by hydrothermal method.

    Among all the nanophotocatalysts used in this project, the photocatalyst with the composition of 8% by weight of nickel doped in titanium dioxide based on nanozeolite NaX, prepared by the sol-gel method, With its tetragonal crystal structure, it was determined as the selected catalyst in the oxidative desulfurization process considered in this research. The efficiency rate in the optimal test by the mentioned catalyst and under visible light radiation was 99.99%.

    The average size of the nanoparticles obtained by the Debye-Sherrer method was calculated to be 50.95 nm, which is in good agreement with the electron microscope results (50.36 nm). According to the WAXS method, the crystallinity of this catalyst was over 95% and the distribution of nickel particles on the surface of the catalyst was 43.8% on average.

    In the experiments of the model diesel fuel photocatalytic desulfurization reactor, which includes the resistant compound of dibenzothiophene in Decane solvent (with 100 ppmw of sulfur), it was carried out under mild scientific conditions and without the presence of hydrogen. Operational parameters such as catalyst mass, amount of oxidant, type and amount of light radiation, amount of dopant and type of catalyst on process efficiency were investigated. The measurement of the initial and final concentrations of sulfur as well as the determination of the degradation products have been done by a gas chromatography-mass spectrometry (GC-MS) device.

    Lagergren and Elovich's pseudo-first-order kinetic models and Blanchard's pseudo-second-order model for the photocatalytic degradation reaction of sulfur in a photoreactor designed with a discontinuous system were studied and the degree Reaction and rate constant were determined. According to the highest correlation coefficient, it was determined that the kinetics of the reaction follows the pseudo-first-order model and the obtained rate constant is equal to 0.048.

    A diesel sample was also tested in optimal conditions, and the results indicate the efficiency of the desulfurization technique on the real sample.

    Key words: Photocatalyst, titanium dioxide, nickel, nanozeolite, desulfurization, diesel, dibenzothiophene,
    GC-MS.

    -1. Nano:

    The suffix nano means one billionth (9-10). Therefore, nano technologies and sciences work in areas whose dimensions are in the range of nanometers. Nanoscience:

    Nano science is the study of phenomena and manipulation of materials on an atomic and molecular scale, in this small scale, the properties of materials are different from their properties on a large scale.

    1-1-2. Nanotechnology:

     

    Nanotechnology[1] is the design, identification, production and application of structures, plans and systems using the control of the shape and size of materials at the nanoscale.In other words, nanotechnology is the ability to produce new materials, tools and systems by taking control at the molecular and atomic level and using the properties that appear at those levels [80]. Nanotechnology is a new and important field in various sciences, and the latest developments in this field have led to the production of materials and equipment with completely new characteristics [35]. In fact, nanotechnology is not a new field, but a new approach in all fields that promises to change the direction of technology development in a wide range of applications. The role of this technology in the future undoubtedly evokes a new revolution in today's industrial world [53]. Reducing the particle size from the micrometer scale to the nanometer scale has caused fundamental changes in material properties, so that colloidal nanomaterials[2], compared to similar micrometer materials, show different characteristics in applications such as magnetic, optical, electrical, and catalytic properties, therefore, in recent years, much attention has been paid to zeolite colloidal suspensions with particle sizes smaller than 200 nm. ]23[.

     

    1-2. Nano-structured materials:

     

    Materials with a very fine structure, in which the size of phases or grains is in nanometers, are identified under the name of nano-structured materials [3]. Currently, in a general definition, any material that has grains, layers, or threads on the nanometer scale is called a nanostructure. Due to the very small size of the components of the structure and the high surface to volume ratio, these materials have attracted a lot of attention and interest because they show unique mechanical, optical, electronic and magnetic properties. Among the nanostructure materials, the following can be mentioned: 1- Particles and powders with a diameter of less than 100 nanometers, including metal and ceramic nanopowders. 2- Fibers with a diameter smaller than 100 nanometers, such as nano Rods[4], nanotubes[5] and nanofibers[6].

    3- Layers with a thickness less than 100 nm                                        
    4- Grains smaller than 100 nm, such as nanocrystalline materials [7].

    5- Nano composites, which include metal, ceramic, polymer nano composites and a set of the above.

    1-3. Catalyst:

     

    The word catalyst was used for the first time in 1836 by Brasilius[8]. A catalyst is a substance that usually changes the rate of a chemical reaction. Of course, it is important to mention that reactions that cannot be done thermodynamically cannot be done with the help of a catalyst. Ostwald [9] was the first person who stated that the catalyst changes the speed of a reaction but does not affect the equilibrium position of the reaction, according to this issue, the catalyst must change the speed of a reaction equally. In Figure (1-1), it can be seen that the activation energy is reduced by using the catalyst. Catalysts are of two types:

    homogeneous catalyst in which all the reaction is done in one phase and heterogeneous catalyst in which the reaction is done at the interface between two phases, this type of catalyst is also called proximity or surface catalyst [60].

    Figure (1-1), comparison of activation energy with/without Catalyst

     

    1-3-1. The role of nanostructure catalysts in the removal of environmental pollutants:

    Catalytic materials are among the oldest nanostructure materials that have been known long before the introduction of science and nanotechnology. Catalysts are used in various fields, one of their important applications is the removal of environmental pollutants. The successful application of catalytic processes depends on the effectiveness of the catalyst, which is affected by three factors: activity, selectivity and stability [9]. Today's advanced catalysts are designed in the form of nanocrystalline and nanoporous materials.

  • Contents & References of Fabrication and characterization of nanotitania-based photocatalysts for desulfurization of the sulfur-resistant compound dibenzothiophene

    List:

    Persian..1  

       Chapter One: Generalities

        1-1. Nano ..4

        1-1-1. Nano science..4

        1-1-2. Nano technology..4    

        1-2. Nano structure materials..5

        1-3. Catalyst..5  

        1-3-1. The role of nanostructure catalysts in the removal of environmental pollutants. 6

        1-4. Sol-gel process in the synthesis of nano photocatalysts. 6

        1-5. Photocatalytic decomposition..7

        1-6. Semiconductors..7

        1-7. Photocatalyst..9

        1-8. Titanium dioxide..10

        1-9. TiO2 photocatalyst in the nano scale.10

        1-10. Mechanism of photocatalytic degradation of titanium dioxide.11

     

        1-11. Improving the efficiency and reactivity of titanium dioxide. 14

        1-12. Photocatalysis..17 

        1-13. Types of semiconductor catalysts (photocatalyst). 17

        1-14. Nanoparticle characterization methods. 18

        1-14-1. Electron microscope analysis. 18

    1-14-2. Structural analysis..20

        1-14-3. Morphological analysis..21

        1-15. The history of the origin of zeolites. 22

        1-16. The structure of zeolites..22

        1-17. Porosity of zeolites..24

        1-18. Characteristics and uses of zeolites. 24

        1-19. Properties of zeolites..25

        1-20. Types of zeolites..25

        1-20-1. Natural zeolites..25

    1-20-2. Synthetic zeolites..26

        1-21. Parameters affecting the synthesis of zeolite. 26

        1-22. Synthesis of zeolite nanocrystals. 28

        1-22-1. Synthesis of zeolite nanocrystals using gel and clear solution. 28

        1-22-2. Synthesis of zeolite nanocrystals in closed space. 29

        1-23. Chemical reactors..29

        1-24. Discontinuous reactors (Batch).30

        1-25. Photoreactor..31

        1-25-1. Types of photocatalytic reactors. 31

        1-25-2. TiO2 Slurry Reactors .32

        1-25-3. Immobilized photocatalytic reactors with stabilized TiO2.33

        1-26. Brief about sulfur, its properties. 33

        1-27. Disadvantages of sulfur and the reasons for its removal. 34

        1-28. Sulfur in diesel fuels. 35

        1-29. Sulfur in gasoline fuel..35

        1-30. The importance of desulfurization..36

        1-31. Investigating the role of thermal and catalytic reactions in the desulfurization process. 38

        1-32. Reasons for proposing photocatalytic oxidation desulfurization methods. 39

        1-33. The purpose of this research. 40

    Chapter Two: Review of past texts

        2-1. Introduction..42 

        2-2. The effect of the amount of sulfur in used fuels on the formation of polluting compounds. 43

        2-3. Global rules for the amount of sulfur allowed in fuels produced by refineries. 45

        2-4. Standards and sulfur content of fuels produced in Iran's refineries. 46

        2-5. Distribution of sulfur compounds in fuels produced by refineries. 46

        2-6. Different methods of desulfurization. 47

        2-7. Desulfurization using hydrogen (HDS).48

        2-7-1. Reactivity of sulfur compounds in HDS.49 2-8. Desulfurization without using hydrogen.50

        2-9. Photocatalytic desulfurization.50

        Chapter Three: Materials and Methods

       3-1. Devices and equipment used in the laboratory. 59

       3-2. Chemicals used in the laboratory. 60

       3-3. The method of conducting tests..62

       3-3-1. Nano photocatalysts used. 62

       3-3-2. Basic preparation: Synthesis of fugasite nanozeolite NaX.64

    3-3-3. Methods of synthesis and characterization of nanophotocatalysts. 65

    3-4. Band-gap determination..99

       3-5. Photocatalytic processes..100

       3-6. Feed used..100

       3-7. Designed photoreactor..101

       3-8. Analysis of feed and products..103

       3-9. Calibration of gas chromatography device. 105

       3-9-1. Draw the calibration curve. 105

       3-10. The method of performing photocatalytic desulfurization tests. 108

       3-11. Isothermal study of the process. 109

    3-12. The study of the kinetics of the process. 137

       3-13. Performance reviewInvestigating the performance of Pcat(29) photocatalyst in the dedusting of the real sample. Synthesis and characterization of fugasite nanozeolite NaX.143 4-1-1. The effect of different parameters on the synthesis of zeolite NaX .143

    4-1-2. Interpretation of the results of NaX.145 fugasite nanozeolite analysis results 4-2. Interpretation and analysis of the results of nanophotocatalysts characterization analysis. 148

    4-2-1. Interpretation of characterization results for photocatalyst Pcat(1).148

    4-2-2. Interpretation of characterization results for photocatalyst Pcat(2).149

    4-2-3. Interpretation of characterization results for photocatalyst Pcat(3).150

    4-2-4. Interpretation of characterization results for photocatalyst Pcat(5).152

    4-2-5. Interpretation of characterization results for photocatalyst Pcat(12).153

    4-2-6. Interpretation of characterization results for photocatalyst Pcat(14).154

    4-2-7. Interpretation of characterization results for photocatalyst Pcat(16).155

    4-2-8. Interpretation of characterization results for photocatalyst Pcat(19).157

    4-2-9. Interpretation of characterization results for photocatalyst Pcat(23).159

    4-2-10. Interpretation of characterization results for photocatalyst Pcat(24).161

    4-2-11. Interpretation of characterization results for photocatalyst Pcat(25).162

    4-2-12. Interpretation of characterization results for photocatalyst Pcat(26).163

    4-2-13. Interpretation of characterization results for photocatalyst Pcat(29).166

    4-3. Interpretation of Band-gap measurement results. 172

    4-4. Conversion percentage.173

       4-5. Investigating the effect of effective parameters on the efficiency of the photocatalytic oxidative desulfurization process. 173

    6-4. Interpretation of the results of other photoreactor desulfurization tests. 188

    4-6-1. The results of desulfurization experiments with group (a) photocatalysts. 188

    4-6-2. The results of desulfurization experiments with group (c) photocatalysts. 191

    4-6-3. Comparison between total loading photocatalysts in desulfurization. 193

    4-6-4. The results of desulfurization experiments with group (d) photocatalysts. 193

    4-6-5. The results of desulfurization experiments with group (e) photocatalysts. 195

    6-4-6. The results of desulfurization experiments with group (T) photocatalysts. 199

    7-4. Determining the type of process used in this research for desulfurization. 203

    4-8. Calculation of dipole moment by the method of quantum chemistry theory. 204

    4-9. Analysis of feed and products. 205

    4-9-1. How to interpret the quantitative results obtained from the GC-MS device. 205

    4-9-2. How to interpret the qualitative results of GC-MS analysis. 206

    4-10. Reaction kinetic studies. 210

       4-10-1. Verification of compatibility with kinetic models. 214

       4-11. Interpretation of the results of the desulfurization tests of the real diesel sample. 214

    Chapter Five: Discussion and suggestions

    1-5. Conclusion. 218

       5-2. Suggestions. 221. References. 222. English summary. 233. Appendices. 235. Source: 1. Aboel-Magd, A., AbdE1-Aal, M., 1998, TiO2-photocatalytic oxidation of selected heterocyclic sulfur compounds, Journal of Photochemistry and Photobiology A Chemistry, Vol. 114, P. 213-218.

    2. Alen, N. S., Edge, M., 2008, Photocatalytic titania based surfaces: Environmental benefits, Polymer Degradation and Stability, Vol. 93, P. 1632-1646.

    3. Alfano, O., Hahnemann, D., Cassano, A., Dillert, R., Goslich, R., 2000, Photocatalysis in water environments using artificial and solar light, Catal. Today, Vol. 58, P. 199-230.

    4. Andreozzi, R., Caprio, V., Insola, A., Marotta, R., 1999, Advanced Oxidation Processes (AOP) for Water Purification and Recovery, J. Catalysis Today, Vol. 53, P. 51-59.

    5. Aye, T., Anderson, W.A., Mehrvar, M., 2003, Photocatalytic Treatment of Cibacron Brilliant Yellow 3G-P (Reactive yellow 2 Textile Dye), J. Environmental Science and Health, Part A: Toxic/Hazardous Substances & Environmental Engineering, Vol. 38, P. 1903-1914.

    6. Babich, I.V., Moulijn, J.A.

Fabrication and characterization of nanotitania-based photocatalysts for desulfurization of the sulfur-resistant compound dibenzothiophene
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