My point is trying to extrapolate other physical properties of a fluid from its flash point isn't something I'd recommend.
I think I can see where you are going, let's try.
Group 1 oils have significant naphthenic and aromatic molecules remaining even after solvent extraction. In the same boiling range, you have quite a mix of molecular forces with different intermolecular as well as intramolecular forces.
Aromatics with the shared pi bond electrons are quite stable in a number of respects. Their density will change less with temperature than similar parrafinic compounds, and their autoignition temperatures will be significantly higher than similar paraffin compounds. Aromatic compounds are good in gasoline for antiknock properties and energy release. In diesel, with no spark for ignition, aromatic compounds lower the cetane rating for the same reasons they increase gasoline octane rating. They also tend to make great solvents but can burn smoky / sooty. They are difficult to destroy in nature.
Naphthenic compounds are cycloparrafins but lack the shared pi bonds of aromatics. They are less dense than similar aromatics but more dense than similar non-cyclo paraffins. They can flex to some degree but their ring structure makes for a large effective molecular diameter.
Isoparrafins are lower boiling than normal paraffins, but would typically have higher autoignition points than similar normal paraffins. They have high octane values (isooctane is 100 octane by definition) and lower cetane rating. They will similarly have lower freezing temperatures than similar normal parrafins and naphthenes, but higher vapor pressures due to their lower boiling points. This is what catalytic dewaxing produces (hydroisomerization); hydrocracking also produces a high fraction of isoparaffins. Hydrogenating polyalphaolefins produces isoparrafins, but the lubricants industry nomenclature is to refer to them as if they were still olefins, or add the suffix (hydrogenated). For example, 1-decene homopolymer (hydrogenated). Hydrogen has been added at the molecular level, and structure is skewed to favor branched chains. This increases the presence of these compounds vs. what was naturally occurring in the crude oil.
Normal paraffins have the lowest octane value (normal octane has an octane value of zero by definition), which can be expected from their lower autoignition temperatures. They conversely are very desirable for diesel cetane rating. However they will form waxes easily. Canning wax like Gulfwax is a good example of something rich in normal parrafins. The natural gasoline fraction of crude oil and natural gas condensate also typically has a high proportion of normal parrafins, requiring skeletal isomerization to raise octane by converting to isoparrafins, which also raises volatility as this lowers boiling point. Or catalytic reforming to not only convert naphthenes to aromatics, but to get normal paraffins to wrap into rings that are then dehydrogenated as well. This raises octane and lowers volatility, but increases freeze point (not really an issue in gasoline though) and more challenging to combust completely.
Hope this helps. There are always tradeoffs.
As for VII's, I can't speak knowledgeably on those. My lubricants production experience included converting naphthenic crude to a variety of hydroprocessed process oils and while working my way through college some marine cargo custody transfer work for Lubrizol and once some base oils for Pemex; never formulating a full retail level engine oil. I'll defer to Molakule on that part of your question / discussion.
I think I can see where you are going, let's try.
Group 1 oils have significant naphthenic and aromatic molecules remaining even after solvent extraction. In the same boiling range, you have quite a mix of molecular forces with different intermolecular as well as intramolecular forces.
Aromatics with the shared pi bond electrons are quite stable in a number of respects. Their density will change less with temperature than similar parrafinic compounds, and their autoignition temperatures will be significantly higher than similar paraffin compounds. Aromatic compounds are good in gasoline for antiknock properties and energy release. In diesel, with no spark for ignition, aromatic compounds lower the cetane rating for the same reasons they increase gasoline octane rating. They also tend to make great solvents but can burn smoky / sooty. They are difficult to destroy in nature.
Naphthenic compounds are cycloparrafins but lack the shared pi bonds of aromatics. They are less dense than similar aromatics but more dense than similar non-cyclo paraffins. They can flex to some degree but their ring structure makes for a large effective molecular diameter.
Isoparrafins are lower boiling than normal paraffins, but would typically have higher autoignition points than similar normal paraffins. They have high octane values (isooctane is 100 octane by definition) and lower cetane rating. They will similarly have lower freezing temperatures than similar normal parrafins and naphthenes, but higher vapor pressures due to their lower boiling points. This is what catalytic dewaxing produces (hydroisomerization); hydrocracking also produces a high fraction of isoparaffins. Hydrogenating polyalphaolefins produces isoparrafins, but the lubricants industry nomenclature is to refer to them as if they were still olefins, or add the suffix (hydrogenated). For example, 1-decene homopolymer (hydrogenated). Hydrogen has been added at the molecular level, and structure is skewed to favor branched chains. This increases the presence of these compounds vs. what was naturally occurring in the crude oil.
Normal paraffins have the lowest octane value (normal octane has an octane value of zero by definition), which can be expected from their lower autoignition temperatures. They conversely are very desirable for diesel cetane rating. However they will form waxes easily. Canning wax like Gulfwax is a good example of something rich in normal parrafins. The natural gasoline fraction of crude oil and natural gas condensate also typically has a high proportion of normal parrafins, requiring skeletal isomerization to raise octane by converting to isoparrafins, which also raises volatility as this lowers boiling point. Or catalytic reforming to not only convert naphthenes to aromatics, but to get normal paraffins to wrap into rings that are then dehydrogenated as well. This raises octane and lowers volatility, but increases freeze point (not really an issue in gasoline though) and more challenging to combust completely.
Hope this helps. There are always tradeoffs.
As for VII's, I can't speak knowledgeably on those. My lubricants production experience included converting naphthenic crude to a variety of hydroprocessed process oils and while working my way through college some marine cargo custody transfer work for Lubrizol and once some base oils for Pemex; never formulating a full retail level engine oil. I'll defer to Molakule on that part of your question / discussion.
