Sciencemadness Discussion Board

Synthetic oils - production and possible feed stocks

RogueRose - 17-12-2016 at 15:47


I'm curious about synthetic vs "normal" engine and transmission/crankcase oils especially the feed stock for the synthetics. The following pages lists 5 grades of oil and it looks like most, even some synthetics come from petroleum.
http://www.synthetic-oil-technology.info/

Group I and II - these are mineral oils derived from crude oil
Group III - this is a highly refined mineral oil made through a process called hydrocracking. In North America this group is considered a synthetic oil, for marketing purposes.
Group IV - these are true synthetic oils, known as Polyalphaolefin (PAO).
Group V - these are synthetic stocks other than PAO's and include esters and other compounds.


One synthetic is classed as a "Polyalphaolefin" - a search for which turns up "polyolefin" and "synthetic oils". Polypropylene and polyethylene are both Polyolefins and they all are made up of carbon and hydrogen. Synthesis of this is stated from petroleum.

What got me curious is an article about recycling oil that stated it took 67 gallons (1.6 barrels) of crude to make a gallon of oil.
http://www.deq.state.ms.us/mdeq.nsf/page/Recycling_UsedMotor...

If synthetic oil needed to be produced and petroleum wasn't available, I'm guessing it could be made from coal or even natural gas similar to the ways other feed stocks are made from them in place of petroleum? If this is possible, how labor and equipment intensive would a process such as this be and what might be the cost comparisons to a petroleum derived product?

Finally I'm not sure what "regular" motor oil is since it seems that the synthetics come from petroleum as well. Is the oil just a base/heavy fraction that is considered "natural"? I looked at some re-refining of oil and it seems like it is basically treaded as crude and put through the distillation process again - hence "re-refining" - is there anything different (before/after) that needs to be done to it for this process?

Edit: Fixed spelling error in title

[Edited on 12-18-2016 by zts16]

DDTea - 17-12-2016 at 17:09

Quote:

If synthetic oil needed to be produced and petroleum wasn't available, I'm guessing it could be made from coal or even natural gas similar to the ways other feed stocks are made from them in place of petroleum? If this is possible, how labor and equipment intensive would a process such as this be and what might be the cost comparisons to a petroleum derived product?


If synthetic oils are poly-a-olefins (polyethylene, polypropylene, with various comonomers and properties tailored to the end use), then yes: they absolutely can be derived from non-petroleum feedstocks. Ethane from natural gas may be dehydrogenated to ethylene. Ethylene, in turn, may be oligomerized to a full range of light-to-midweight, even numbered, alpha olefins via the Shell Higher Olefin Process. These alpha-olefins are used as comonomers for polyethylene, altering its crystallinity, melting point, etc by introducing short-chain branches. Propane, from natural gas, may be dehydrogenated to propylene as well. This is all practiced commercially and is quite practical.

Generating industrial organic chemicals from coal is more round-about and intensive, but the technologies associated with it may have value in a future commodity chemical supply chain starting from renewable resources (CO2, biomass). Coal is first gasified by high temperature steam to form a mixture of CO and H2--synthesis gas--along with some CO2. The composition of the syn gas is tuned through the water gas shift reaction and then is subject to various catalytic processes to generate organic chemicals. Fischer-Tropsch synthesis, for example, provides access to synthetic (very clean-burning) diesel. Syn gas may also be used to generate methanol, a potential future energy carrier and chemical feedstock. Methanol, in turn, can provide propylene, ethanol, and gasoline through the Methanol-to-Hydrocarbon reaction (aka, Methanol-to-Olefin or Methanol-to-Gasoline, depending on how the process is run and the catalysts used). This is not practiced as widely, but is of long-term scientific and industrial interest. In the near term, given their huge volumes of coal, China has been making major headway in coal-to-chemicals.

Taking a different direction with this thread...given that polyolefins have application as lubricating oils, I wonder if a process could be made to depolymerize polyolefin waste into motor-oil? It would certainly be of low-quality, but it's better than proposals to convert polyolefins to fuel (and ultimately CO2 greenhouse gas). Trading one off-loop waste product in society's metabolism for another.