Metabolic pathway of Desulphurization of Dibenzothiophenn

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2. UMM E HABIBA
2021-ag- 2585
Supervisor: DR.M. IRFAN MAJEED
Department of chemistry University of agriculture
Faisalabad (PARS)
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3.  Introduction
 Desulphurization
 Types of desulphurization
 Mechanism
 Sample preparation
 Analysis
 Why prefer Raman spectroscopy
 Conclusion
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4.  3rd most abundant element in petroleum products.
 Production of oxides of sulphur.
 These oxides leads to air pollution, acid rain and many health problems.
 Corrosive product
 Desulphurization
The process by which sulphur is removed from petroleum products (gasoline,
jet fuel, diesel fuel) is called desulphurization. It may be
1- Hydrodesulphurization 2- Biodesulphurization
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5.  Catalytic process
 Bed reactor covered with suitable catalyst
 Standard catalyst are: NiMo/AL2O3, CoMo/AL2O3
 Temperature range 200-425℃ ; Pressure 1-18MPa
Hydrogenolysis
C-X bond break, formation of C-H and H-X bond
Thiols:
 R-SH+ H2 RH+ H2S
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6.  50-95% sulphur content is in the form of thiophenic sulphur.
 Dibenzothiophene is the key heterocyclic organo sulphur compound.
 Metabolism of sulphur compounds take place in the presence of bacteria.
 At room temp: 40 – 70℃ at atmospheric pressure
 Bacterial enzyme are very selective
 Cleavage of C-S bond
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7.  Desulphurization take place in the presence of aerobic bacteria.
 Like; Rhodococcus erythropolis, Gordona sp., Mycobacterial sp.
 Aerobic desulphurization take place by to two mechanism.
Kodama pathway
Kodama were the first to report aerobic conversion of DBT.
Kodama pathway:
 Destructive technique
 In this aromatic ring (C-C) cleavage of DBT take place, due to which calorific
value decrease.
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8.  First selective Rhodococcus erythropolis strain were isolated from soil of
Eucalyptus tree.
 This specie able to carry out selective oxidation of the heterosulphur atom
keeping the ring intact.
 In this 4 enzymatic steps are involved so called 4S pathway.
 Three enzymes are involved DszA, DszB and DszC.
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fig: 1Schematic representation of enzymes
(Chemdraw)

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Fig: 2 mechanism of 4s pathway
(chemdraw)

11.  At elevated temperature and pressure
Temp: 200-425℃
Pressure: 1-18 Mpa
 Expensive method
 Heterocyclic organo sulphur compounds are difficult to removed
 Low calorific value
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12.  Bacterial sample is obtained from soil of Eucalyptus tree.
 Use MG medium (minimum salt glucose media)
 Place bacteria + DBT in MG media and put on shaker.
 Centrifuged at 4000rpm at 20℃ for 20 min
 Supernatant is obtained
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13. In recent studies metabolites are analyzed by HPLC and GC-MS.
In case of HPLC expensive solvent are used.
For GC analysis sample first converted into vapors by using Nitrogen gas.
Drawbacks:
These methods are
 Time consuming
 Trainers are required
 Expensive
Now we moved toward Raman spectroscopy
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14.  Small amount of sample
 No need of sample preparation
 Simple and reliable
 Rapid technique
 Non-invasive
 Give fingerprint of compound
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15. Raman spectroscopy is a spectroscopic technique used to determine the
vibrational modes of the molecule to provide a structural fingerprint by which
molecule can be identified
 Rayleigh scattering
 Stokes scattering
 Anti stokes scattering
Fig:3 Principle of Raman spectroscopy
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16.  We take 50 micro liter of
sample on aluminum slide
substrate.
The laser light was focused
onto the Sample and collects
the spectra.
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Intensity
Raman spectra of DBT and DBTO2

18.  BDS is low cost and greater reaction specificity.
 The removal of sulphur from petroleum products makes our
engine corrosion free.
 Raman helps to reveal the metabolites form during
biodesulphurization.
 As compared to other techniques, Raman gives fingerprint of
compound.
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19. Ahmad, M., M. Yousaf, S. Wang, W. Cai, L. Sang, Z. Li and Z.-P. Zhao.
2022. Development of rapid CO2 utilizing microbial ecosystem onto the
novel & porous FPUF@ nZVI@ TAC@ ASP hybrid for green coal
desulphurization. Chemical Engineering Journal, 433: 134361.
Javadli, R. and A. De Klerk. 2012. Desulfurization of heavy oil. Applied
petrochemical research, 1: 3-19.
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