Dear hossein Aref,

The most efficient method of oil desulfurization is to cause the sulfur hydrogenation catalytic reaction according to the following equation:

S + H2 = H2S. H2S is a gas of bad odor.

Then, the H2S will be separated by washing in a liquid-gas absorption column. The liquid solvent may generally be mono or di or triethanolamine. It is a chemical absorption activated by the drop in temperature.

Hopefully this answer will help you meet your needs.

Best regards.

Dr. Adel OUESLATI 

CoMo or NiMo catalyst is typically used.  Reactions are slightly different based on the type of sulfur compound  Mercaptans  require 1 mole of H2 per mole of S (RSH+ H2=> H2S + RH) sulfidies require 2 moles of H2  per mole of S.  Thiophenes , Benzothiphenes and Dibenzothiophenes require at least 3 moles of H2 per mole off S and often more dependent on the amount of aromatic ring saturation required.   Commercial Hydrodesulfurization units typical operate at 600-700 F (315 to 370 C) and about 1-2 LHSV (V/H/V).  These reactors often also have some  side reactions occurring including olefin saturation, aromatic ring saturation and sometimes ring opening, Hydrodenitrogenation (N removal to form NH3) and hydrocracking to form lighter/lower boiling Hydrocarbons. 

pubs.acs.org/doi/full/10.1021/ef900876j

https://en.wikipedia.org/wiki/Flue-gas_desulfurization

www.sciencedirect.com/science/article/pii/S187853521300453X

Hydrodesulfurization is the most commonly used method

in the petroleum industry to reduce the sulfur content of

crude oil

Extractive desulfurization

Desulfurization via extraction depends on the solubility of

the organosulfur compounds in certain solvents. It is a

liquid–liquid extraction process and the two liquid phases

must be immiscible.

Ionic liquid extraction

The extractive desulfurization of fuels such as diesel oil by

ionic liquids (ILs) as opposed to traditional organic solvents

is an interesting alternative to provide ultra clean diesel oils.

Adsorptive desulfurization

Desulfurization by adsorption depends on the ability of a

solid sorbent to selectively adsorb organosulfur compounds

from the oil. The efficiency of this method depends on the

properties of the sorbent material: selectivity to organosulfur

compounds relative to hydrocarbons, adsorption

capacity, durability, and regenerabilityThere are two

approaches that can be taken for adsorptive d esulfurization

You may also like to check these interesting papers related to your subject of interest.

https://link.springer.com/article/10.1007/s13203-012-0006-6

http://www.refiningnz.com/visitors--learning/classroom--learning-resources/learning-centre/how-it-works---the-refining-process/desulphurisation.aspx

http://nptel.ac.in/courses/103107082/module6/lecture8/lecture8.pdf

https://en.wikipedia.org/wiki/Hydrodesulfurization

http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072010000200007

http://www.sciencedirect.com/science/article/pii/S187853521300453X

http://www.sciencedirect.com/science/book/9780128013472

Dear Raju Thapa, 

Thanks a lot.  we can add something: the prcoesse of sulfur removal depends on several parameters, such as the type of crude oil, the operating conditions, the quality of product to be obtain, the catalyst used in the process and the chemical analysis of the crude oil.

best wishes and kind regards!

Dr. Adel OUESLATI 

H2S is preferred economically because it is needed to produce sulfur and sulfuric acid. In previous economies calcium salts of oxidized sulfur were preferred when sulfur was available from lower cost sources. 

Hello everyone. Does anyone know alternative methods for the desulfurization techniques of bunker/heavy fuels?

Generally there is a plethora of information for the diesel desulfurization, but it becomes more difficult for the bunker fuels.

Panagiotis,  Removing Sulfur from vacuum redidue is similar to desulrization of diesel except an order of magnitude more catalyst is used (LHSv 0.2 instead of 1-2) and higher pressure..

Exxon Mobil had a process called "Residfining" that operated around 1500 PSIG and 0.2 LHSV (V/H/V of catalyst).  Chevron had a similar process that went with higher pressure (2000-2500 PSIG).and highed spacevelocity (~.5-.7),   Many of these units were built in the 70's and 80s I believe some still operate in Japan but most were converted into higher margin service (FCCU feed Hydrotreating and Mild Hydrocracking).   

Solvent deaphalting with propane or butane solvent is also a good way to upgrade (lift) a porttion (60-70%) of the vacuum residue so the light portion can be Hydrodesulfurized at less severe conditions. This has recenlt become a popular way to upgrade tar sands in Canada   My old friend Rich Hood has  very good process to o this. I can give you a lot more info if you are inerseted.

Delayed Coking of vacuum residue is by far the most frequently used process that upgradesvavuum rsidue.

Resdue Hydroprocesseing processes like H-OIl and LC-Fining are also used. This is a more expensive route with some product compatability issues but yields are better.    Let me know if you want more information about how refineries upgrade and or desulfurize Vaccuum Residue. 

I really thank you for your useful and interesting reply. I would be interested and grateful if you could give me some more information.

All these methods I know more or less, but the problem with these method of hydrodesulfurization is that severe conditions are needed and especially for the removal of the refractory sulfur components of the heavy fuels. So I was wondering if there is in industry any alternative method for this desulfurization for example oxidative desulfurization with extraction. I know that this can be implemented for example for the diesel, but I would like to know if currently alternative methods for desulfurization are implemented.

Thank you again!

Panagiotis Kagioulis,

We probably should start another thread instead of Hijacking Amir's question thread but here is a brief description of what refineries do with Vacuum Residue (typically 1050 F + boiling range:

• Some Vacuum Residues have value as:

o Asphalt

 Must meet Viscosity and Penetration Speciation for various grades

 AC-10.AC-20,AC-30 and AC-40 are typical grades

o Lubricants – Viscosity and Viscosity Index (aka VI) specs for Bright Stock

 Often Hydrotreted to achieve these specs

• Most Vac Resids are nor suitable for Asphalt or Lubes and are sold as:

o High Sulfur Fuel oil

 Diluted with Diesel or lighter material to meet viscosty specification

o Low Sulfur Fuel Oil

 Usually Requires Dilution and/or Hydrotreating

 Breakeven value of Vac Residue is near or even below 0

o Dedicate Vacuum Residue upgrading units described below

• Upgrading Options:

o Residue Hydrotreating to produce lower Sulfur Residue and minimal cracking to lighter material

 Most Hydrotreating units built for this service were shut down or converted to other servoces

 A few of these units still operate as designed – mostly in Japan

 Some of these units produce resid boiling range feed to Fluidized Bed Catalytic Cracking Units (FCCU) that primarily produce gasoline.

• Require a more advanced FCCU design

o Thermal Conversion:

 Visbreaking has been used prinarilly in Europe and the Carribean

• Thermal cracking process produces fuel oil

• Max conversion set be product stability (multiple liquid phases) issu

 Delayed Coking:

• Batch wise more severe thermal cracking (typically 16-24 hr drum cycles) to produce:

• Solid petcoke (20-40 Wt%)

o Usually ss olid as an equivalent to coal

o Occasionally higher value as Anode or other specialty grade coke

• Hydrogen Deficient Liquid products (FCCU feed Gasoline and Diesel boiling range

o Requires Hydrotreating to produce finished products

• Fuel Gas

o Olefinic gas sometimes ised as Alkylation feed

 Fluid Coking – Continuous coking process with products similar to Delated Coking

 FlexiCoking - Similar to Fluid coking except petcoke is gasified to produce low Btu fuel gas



o Solvent Deasphalting

• Propane/Butane/Pentane used as solvent to “lift” higher quality material for upgrading at an FCCU

• Heavy materially burned or used as asphalt if it can be blended to meet specs

o Hydroconversion-

 H-Oil and LC-Fining Processes Hydrocrack Residue to lighter products that can be upgraded to Diesel or Gasoline in other refinery units

• Max conversion set be compatability limits similar to issues with visbreaking but at much higher conversion.

o Gasification – Thermal partial oxidation or other catalytic gasification processes

 Synthesis gas used for H2 production or Methanol, Ammonia or even Fischer Tropsch

I think that covers most of the option Refineries have to upgrade residue. The vast majority dilute and blend to produce a fuel oil. Delayed Coking is the most prevalent Vacuum Residue conversion process.

All of these processes require a combination of Carbon Rejection and H2 addition to produce finished product with the correct Hydrogen content to meet finished product specifications.

Let me know if you need additional information.