GTL Base Oil Synthesis

[MolaKule]

The GTL Group III+ Base Oil Synthesis Process (A Summary derived from various Patents)
by MolaKule​

The Gas-to-Liquid process is executed primarily by using a Fisher-Tropsch process

10.2. Fischer-Tropsch Synthesis

Liquid transportation hydrocarbon fuels and various other chemical products can be produced from syngas via the well-known and established catalytic chemical process called Fischer-Tropsch (FT) synthesis, named after the original German inventors, Franz Fischer and Hans Tropsch in the 1920s...

www.netl.doe.gov

whereby a mixture of Carbon monoxide CO and Hydrogen H2 gases are catalytically converted into liquid hydrocarbons, in a mole ratio of approximately 0.7 to 2.5. (A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change).

The catalyst is in the form of a fluidized bed or a slurry of catalyst particles, usually cobalt, but may also use cobalt mixed with other metals. The synthesis gas mixture of CO and H2 is forced into the bottom of and bubbled up through the catalyst slurry and reacts in the presence of the F-T synthesis catalyst in conditions effective to form hydrocarbons, a portion of which are liquid, and a portion which passes out of the reaction vessel as vapors.

Depending on the final liquid characteristics desired, the reactor vessel may be operating under a temperature of from 320F to 850F, a pressure off from 80psi to 600psi, and varying volumetric flow rates.

Some of these vapors are further condensed to liquid and combined with the other liquid hydrocarbons to affect the final liquid hydrocarbon viscosity, pour point, Viscosity Index, etc.

Purification and clarification of the resulting liquid may be done by filtration, centrifuging, and further hydroprocessing. (See https://bobistheoilguy.com/ A Review of Mineral and Synthetic Base Oils, for definitions of the various Hydroprocessing techniques and other pertinent definitions).

The resulting synthetic GTL liquid base oil may have a viscosity range of from 2 cSt to 50 cSt, with the preferable range being 3.5 cSt to 30cSt. The viscosity index averages 130, for example, for a 4 cSt oil. The pour points average about -45C.

Hopefully, this short technical note removes some of the mystery surrounding GTL base oils.

 

[4WD]

A large portion of GTL production goes into fuels …

 

[MolaKule]

A large portion of GTL production goes into fuels …

True, but the emphasis here in this Tech Note is on the how of the production process whereby the catalysis of CO and H2 gasses produces a synthetic lubricating oil, and the characteristics (oil properties) of that lubricant.

 

[ArthurArgentum]

Hopefully, this short technical note removes some of the mystery surrounding GTL base oils.

In the realm of conventional Group III base oils, it is exceedingly uncommon, if not virtually impossible, to find options with a kinematic viscosity at 100°C exceeding 8.6 cSt. Although there were claims of an ETRO10 base oil, I have yet to come across any tangible evidence of its existence, suggesting it may have been a mere advert. However, when it comes to CTL (Fischer-Tropsch or GTL) base oils, I see the presence of real KV100 10 (10+) cSt bases. This leads me to believe that the utilization of purer feedstocks in processes enables the attainment of such heightened KV100s characteristics.

Base Oils - Dowpol Chemical International Corp.

ICCSYN® CTL base oils are API Group III Plus based on CTL (Coal To Liquid) technology. Their unique synthetic composition, with no aromatics, naphthenic, sulfur and nitrogenous content, is designed to enhance performance over conventional base oils in many extreme applications. The basic...

en.dowpol.com

 

[Revving2Redline]

The GTL Group III+ Base Oil Synthesis Process (A Summary derived from various Patents)
by MolaKule​

The Gas-to-Liquid process is executed primarily by using a Fisher-Tropsch process

10.2. Fischer-Tropsch Synthesis

Liquid transportation hydrocarbon fuels and various other chemical products can be produced from syngas via the well-known and established catalytic chemical process called Fischer-Tropsch (FT) synthesis, named after the original German inventors, Franz Fischer and Hans Tropsch in the 1920s...

www.netl.doe.gov

whereby a mixture of Carbon monoxide CO and Hydrogen H2 gases are catalytically converted into liquid hydrocarbons, in a mole ratio of approximately 0.7 to 2.5. (A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change).

The catalyst is in the form of a fluidized bed or a slurry of catalyst particles, usually cobalt, but may also use cobalt mixed with other metals. The synthesis gas mixture of CO and H2 is forced into the bottom of and bubbled up through the catalyst slurry and reacts in the presence of the F-T synthesis catalyst in conditions effective to form hydrocarbons, a portion of which are liquid, and a portion which passes out of the reaction vessel as vapors.

Depending on the final liquid characteristics desired, the reactor vessel may be operating under a temperature of from 320F to 850F, a pressure off from 80psi to 600psi, and varying volumetric flow rates.

Some of these vapors are further condensed to liquid and combined with the other liquid hydrocarbons to affect the final liquid hydrocarbon viscosity, pour point, Viscosity Index, etc.

Purification and clarification of the resulting liquid may be done by filtration, centrifuging, and further hydroprocessing. (See https://bobistheoilguy.com/ A Review of Mineral and Synthetic Base Oils, for definitions of the various Hydroprocessing techniques and other pertinent definitions).

The resulting synthetic GTL liquid base oil may have a viscosity range of from 2 cSt to 50 cSt, with the preferable range being 3.5 cSt to 30cSt. The viscosity index averages 130, for example, for a 4 cSt oil. The pour points average about -45C.

Hopefully, this short technical note removes some of the mystery surrounding GTL base oils.

I believe a long time ago you spoke briefly about this and considered that it may be classified into the group five. I was wondering since then what are your feelings about it? also that it's comparable to Pao, where does GTL thrive that Pao doesn't. maybe just a summary on your thoughts thank you.

 

[Dave P.]

So, tell us MolaKule, since your posts are always the most informative and always catch my eye (even though 99% of what you say is well above me) when you head out to the driveway with your drain plug wrench, filter wrench and oil pan, what oil(s) you pouring in your cars?

 

[ArthurArgentum]

also that it's comparable to Pao, where does GTL thrive that Pao doesn't.

GTL4 (core) -

PAO4 (core) -

PAO & FT (GTL, CTL, etc) - like two peas in a pod..
Btw, isomeric variations within alkanes, such as squalane or triacontane, showcase an analogous C30H62 molecular framework akin to the core C30H62 of PAO4 (1-Decene trimer hydr.) and the core of GTL4. Notwithstanding their a bit dissimilar structural forms, these compounds are unequivocally classified as alkanes (commonly denoted as paraffins). It is crucial to underscore that PAO base oils cannot be classified as olefins due to their hydrogenation process.

 

[MolaKule]

I believe a long time ago you spoke briefly about this and considered that it may be classified into the group five. I was wondering since then what are your feelings about it? also that it's comparable to Pao, where does GTL thrive that Pao doesn't. maybe just a summary on your thoughts thank you.

In the tech paper at https://bobistheoilguy.com/, I mentioned that because of the processes used in the GTL process, I felt the GTL base oil should be placed in a synthetic base oil category. From the above patent review, I still have the same opinion.

It's not exactly the same as PAO because of the resulting molecular structure(s), but shares some of the same attributes.

GTL is derived from refinery gases that are plentiful in situ so it makes sense to capture these gases for lube and fuel production and not to exhaust them into the atmosphere.

API seems to have placed itself into a corner regarding base oil categories which have the effect of not being able to insert new base oil categories as new base oil technologies emerge.

 

[MolaKule]

So, tell us MolaKule, since your posts are always the most informative and always catch my eye (even though 99% of what you say is well above me) when you head out to the driveway with your drain plug wrench, filter wrench and oil pan, what oil(s) you pouring in your cars?

Thanks. I mainly use my own formulations, but I do test and analyze other's PCMO and Lubricant products in my own vehicles and engines as a courtesy and for feedback to the Blender.

 

[MolaKule]

Properties of GTL's may be varied by the specific processing parameters used such as:

"Depending on the final liquid characteristics desired, the reactor vessel may be operating under a temperature of from 320F to 850F, a pressure off from 80psi to 600psi, and varying volumetric flow rates.

Some of these vapors are further condensed to liquid and combined with the other liquid hydrocarbons to affect the final liquid hydrocarbon viscosity, pour point, Viscosity Index, etc."

The resulting paraffinic hydrocarbons may range from C10 to C200.

 

[MolaKule]

.. It is crucial to underscore that PAO base oils cannot be classified as olefins due to their hydrogenation process...

I believe that statement to be incorrect.

PAO | Specification | CAS 68037-01-4 | Connect Chemicals

Poly alpha olefins, widely known as PAO s. The low viscosity PAOs can virtually be found in every modern car engine, acting as a synthetic motor oil.

connectchemicals.com

"Polyalphaolefins Technology​

Polyalphaolefin (PAO) is manufactured through a synthetic chemical process that originates from ethylene.
Ethylene is produced by cracking either crude oil or natural gas. The direct feedstock (normal alpha olefin – NAO) is produced through the chain growth and displacement process for producing petrochemically pure alpha olefins. The PAOs are produced through synthesizing oligomers of either 1-decene or 1-dodecene. These oligomers are distilled and hydrogenated to yield specific molecular weight ranges that meet the viscosity grades that are desired. For example, the fraction that has predominantly the 1-decene trimer (C30 oligomer) has a 100°C viscosity of 4 cSt and is known as PAO 4."

Polyalphaolefins Technology

Chevron Phillips Chemical is one of the world's top producers of ethylene and polyethylene and a leading supplier of aromatics, styrenics, specialty chemicals, plastic pipe and other polymers.

www.cpchem.com

Hydrogenated polyalphaolefins have olefin-carbons saturated with hydrogen, which lends excellent thermal stability to the molecule.

"What is PAO Oil?
Polyalphaolefin oil is a type of synthetic or “man-made” lubricant. Developed in the 1930s, PAO oil’s first commercial use was in the 1970s as a base for engine oils. Since then, PAO oil applications have reached a broader range. Current PAO oil applications include compressor, hydraulic, and turbine fluids, gear oils, and metalworking fluids.

The manufacturing of PAO oil involves a two-step process: synthesis and hydrogenation. First, alpha-olefins are used to synthesize oligomers. Next, the double bonds in these oligomers are hydrogenated to form polyalphaolefin. The PAO is further isolated by distillation to remove the unhydrogenated oligomers."

PAO Oil / Polyalphaolefin - Redlist

Unfamiliar with the terminology in your industry? Our Glossary page is your go-to source for information on the key terms used in your field. Get definitions, synonyms, and explanations of the most commonly used words in a quick and easy-to-reference format so you can stay up to date on the...

www.getredlist.com

 

[MolaKule]

"The final process in the PAO synthesis is to introduce hydrogen at specific temperatures and pressures to create a fully saturated hydrocarbon. This hydrogenation process enhances the oxidation stability of the PAO.

So the PAO development process is essentially: ethylene gas >> 1-Decene, or 1-Dodecene, or 1-Tetradecene liquid monomer >> Oligimerization into liquid polymers >> Hydrogenation of polymer >> Finished PAO."

A Review of Mineral and Synthetic Base Oils - Bob is the Oil Guy

 

[ArthurArgentum]

I believe that statement to be incorrect.

why? -

saturated

Olefins are examples of unsaturated hydrocarbons.
Paraffins (alkanes) are examples of saturated hydrocarbons.
PAO = Alkanes (Saturated, Paraffins) , not olefins (Alkenes). Right?

So PAO cannot be classified as an olefin. Consider the following evidence:

 

[MolaKule]

@ArthurArgentum

This has drifted wildly off the main GTL topic but let me see if I can explain this in terms of molecular bonding:

While alkanes and alkenes are both hydrocarbons, the primary difference is that alkanes are saturated molecules, containing only single covalent bonds (σ-bonds, or alpha-bonds) between the carbon atoms. Alkenes are distinguished by having a double-bond at the primary or alpha position. This location of the alkene double bond enhances the reactivity of this compound and this is what makes it useful in the synthesis of PAO and other chemistrys.

Thus, it can be said, in general, that PAO alkanes are converted Alpha-olefin alkenes. I.e, once the alkene structure becomes Single-bonded (instead of Double-bonded), and with additional hydrogen atoms attached to the carbon atom, they become alkanes.

I think you're missing the importance of the "alpha" position wrt the single and double bonding effects in the synthesis process.

In PAO synthesis linear α-olefins (LAOs) usually have a wide product distribution, so dimers of the α-olefin are usually removed after the completion of the polymerization process.

I know you enjoy 'wordplay' but I still do not see why PAO's cannot be called PolyAlphaOlefins and conventionally understood as such. I think a paper submitted for peer review (to the ACS or another international chemical journal) as to why PAO's cannot be called what they are would be interesting.

 

[MolaKule]

Back to GTL Technology

For those just catching up on GTL technology, Shell has filed over 3500 patents on its technology and here is a set of Shell presentations:

Gas-to-liquids | Shell Global

Our proprietary technology turns natural gas into liquid fuels, base oils for engine lubricants, and ingredients for plastics, detergents and cosmetics.

www.shell.com

 

[4WD]

Back to GTL Technology

For those just catching up on GTL technology, Shell has filed over 3500 patents on its technology and here is a set of Shell presentations:

Gas-to-liquids | Shell Global

Our proprietary technology turns natural gas into liquid fuels, base oils for engine lubricants, and ingredients for plastics, detergents and cosmetics.

www.shell.com

Same with these guys - who in the end stayed with LNG …

Qatar Petroleum & ExxonMobil Sign GTL Heads of Agreement

The Government of the State of Qatar and an Exxon Mobil Corporation subsidiary, ExxonMobil Qatar GTL Limited have entered into a Heads of Agreement (HOA) for a $7 billion, Gas-to-Liquid project.

www.rigzone.com

 

[benjy]

over my head BUT always learning a LITTLE!! always enjoy reading the FACTS from MOLA, thanks for helping others learn more!!