|
|
Posted by David Sherman [24.32.202.83] on Monday, April 26, 2010 at 14:47:14 :
In Reply to: gas vs diesel posted by clueless [201.197.231.58] on Monday, April 26, 2010 at 13:22:43 :
That doesn't make any sense to me. What is happening is that most of the world is going to diesel and US refiners aren't making any money on gasoline. I just read about how they're closing down some more gasoline refining capacity right now to reduce the oversupply and raise the prices. All this talk that you hear now and then about "we need to build more refineries" is BS because not only are the oil companies not even proposing new refineries, but they're cutting gasoline capacity at the refineries they already have.
Most gasoline is made by cracking the oil in cat (catalytic) crackers. This invention is what made large scale gasoline production possible. Before that, all they had was "natural gasoline", which is the small fraction of the crude oil that came out naturally at roughly the right molecular weight (heavy enough to be liquid, but light enough to evaporate quickly). Correct me if I'm wrong, but I think the reason diesel is also known as "distillate" is that it can be produced by distilling crude oil directly and taking the correct fraction out of it, rather than having to crack the crude first. Some of the lightest crude can be used directly as "diesel oil" without any refining other than some filtering.
All in all, that tells me that diesel is cheaper to make than gasoline, although it's hard to really quantify it since refineries make both, along with lots of other products and it's just a book-keeping game to allocate the costs to one product or the other. It definitely costs money and energy to de-sulfurise the diesel as is required nowadays, but then they also have to desulfurize the gasoline. It may also be that some of the heavy crudes need to be cracked to produce meaningful amounts of diesel. Still, the overall process for making diesel is simpler than for gasoline.
Follow Ups: