Lesson 7 Overview

Now this a painting in our EMS museum collections from the MS Museum collections. This is a very early refinery, I would think. You can see the oil wells here, and they're refined. The oil is refined right at the site, which is essentially distillation. You can see this must be the distillation tower. You can see the furnace here with the chimney to heat the crude to the required temperatures. And then collect the fractions.

At the time, it was kerosene, obviously, for lighting. And then, later on, maybe light gasoline. See the storage tank, maybe for the gasses and so forth. So in the last lesson, we've talked about thermal cracking processes to make more of the lighter stuff, essentially. Like distillates, or gasoline from the crude oil, by breaking chemical bonds. And we mentioned that pretty soon, the thermal cracking processes could not meet the demand for quality.

And what has changed in the meantime, when we have now close to the Second World War era, where the motors-- now engines-- have higher compression ratios, and they would require higher octane number gasoline. That means they would need gasoline that would not ignite spontaneously with pressure. And it is pressurized with air. That's essentially what the octane number measures, it's anti-knocking property.

So most catalytic processes, catalytic conversion processes, were developed right before and during the Second World War, mainly for making higher quality, higher performance fuels and in higher yields, in higher quantities. So introducing the catalyst to crack, to crude oil, into gasoline boiling range is not done just to increase the rate of cracking, or has anything to do with kinetics, really. That's what catalysts typically do.

In this case, introduction of the catalyst changes the whole chemistry of cracking. Now we've talked about having neutral, reactive species free of radicals and thermal cracking processes. In catalytic cracking, the reactive species are ions. Or cations, actually, cargo cations that are produced on catalyst surfaces. So we need an acid catalyst-- typically aluminum, silica or zeolites-- in order to create these cationic species.

Why do we need that? Because carbo cations go through isomerization reactions very fast. That means we will have now an opportunity to make branched alkanes or isoparaffins because of this isomerization of the ions as opposed to non-isomerization of the free radicals. Isomerization in free radicals is very, very slow. So it doesn't happen.

So pretty much all gasoline production in the US is done through catalytic means. Fluid catalytic cracking is really the most popular processes. It is the heart of a refinery in the United States, FCC process that generates high octane gasoline. It's a very flexible process. It could use a range of feed stocks in the gas oil, boiling range all the way up to light vacuum gas oil.

For heavier materials, something like heavy vacuum gas oil or vacuum distillation residue, we need to introduce hydrogen so that we could convert these heavy fractions without rejecting larger quantities, or very large quantities, of carbon. Then we get into a hydro cracking processes.

So in this lesson we will go over the historical development of catalytic cracking processes, ending up of course with FCC-- which is universally used and accepted now-- and talk about the hydra cracking processes, some of the conditions that are necessary for treating those very heavy ends of crude oil into upgraded products without rejected carbon, so in higher yields.