Talk:Fluid catalytic cracking

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 Definition A petroleum refining process that cracks the large hydrocarbon molecules in the portion of the petroleum crude oil boiling above 340 °C into lower boiling, more valuable high octane gasoline and olefinic gases. [d] [e]
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The History section is being worked on

The History section will be ready in a few days. - Milton Beychok 20:13, 7 May 2008 (CDT)

Added the completed History section today. - Milton Beychok 03:00, 9 May 2008 (CDT)


Milton what is barg? I know Pa, atm, and bar.--Paul Wormer 02:51, 10 May 2008 (CDT)

Paul, barg is "bar gauge". Bourdon tube pressure gauges display the pressure above atmospheric pressure. Thus, bar = barg + atmospheric pressure.
Just as engineers in the U.S. use psia and psig (meaning psia absolute and psi gauge), many if not most metric country engineers use bara and barg (meaning bar absolute and bar gauge). - Milton Beychok 09:54, 10 May 2008 (CDT)

slurry settler

In your diagram you have fuel oil go from the top of the slurry settler, but you write: The so-called clarified slurry oil is withdrawn from the top of slurry settler ... --Paul Wormer 03:00, 10 May 2008 (CDT)

As explained just below, the oil from the main fractionator bottom contains catalyst fines and for that reason is referred to as a slurry oil. It goes into the slurry settler where most of those fines settle into a thicker slurry which is recyled back to the catalyst riser along with the FCC feedstock. The clarified thinner slurry oil (containing much less catalyst fines) from the top of the settler is referred to as clarified slurry oil and is then routed into the refinery's fuel oil blending system ... or it may be routed into the feedstock of the refinery's delayed coking unit, where the fine would ultimately end up in the petroluem coke, if the refinery has a delayed coker. Does that "clarify" this point? :>) - Milton Beychok 10:27, 10 May 2008 (CDT)


Are (or is) "fines" the same as "particulates"?--Paul Wormer 03:06, 10 May 2008 (CDT)

Paul, the catalyst particles undergo attrition and some of the catalyst gets grinded into smaller sizes that cannot be removed by the cyclones inside the reactor or regegenerator. Those smaller sized particles are called "fines". The fines that get into the main fractionator come out in the fractionator bottoms oil ... hence, the name slurry oil. The fines that get into the flue gas are ultimately removed in the ESP (electrostatic precipitator). Yes, fines are particulates, with "fines" being the industry usage for the attrited small catalyst particles and "particulates" being a generic term that is suitable for any kind of small solid material in the air or other gases. - Milton Beychok 10:10, 10 May 2008 (CDT)

Finished reading

Milton, I found it interesting and have one or two questions (see above).--Paul Wormer 03:22, 10 May 2008 (CDT)


Milton, don't you think that it would be good to somehow incorporate (briefly) the answers to my questions in the article? Other people may have the same questions. Some answers are easy, for instance, barg just needs a brief CZ article. You could append "fines" between brackets to "particulates" in the text and so on.

I see that you posted the same text to WP as a new article, which is a better strategy than trying to correct an existing one, but still ... Good luck. --Paul Wormer 10:56, 10 May 2008 (CDT)

The WP article that I posted does not have the photo of an FCC unit because the permission I got from Valero Oil for using it was for the Citizendium and I don't think it would be good form to go back and ask them for permission to use it on WP as well.
As for incorporating the above answers, I had already decided to do so ... but it may take a little while as my wife has a chore for me right now. - Milton Beychok 13:04, 10 May 2008 (CDT)
I have now created the Bar (unit) article with a section in it that explains the notation and the relation between gauge and absolute pressures. I have linked barg in this article to that new article. I have also linked catalyst fines to Particulate. As for the slurry oil, after re-reading the discussion in this article, I think it is pretty clear as it was and made no changes. Thanks again for your help. Regards, Milton Beychok 17:56, 10 May 2008 (CDT)
Re slurry oil. The text is clear. I overlooked that the slurry oil leaves at the bottom, and in the drawing I saw fuel oil leaving at the top which I thought that had to be the slurry oil. My fault.--Paul Wormer 03:18, 11 May 2008 (CDT)


I will read the NH3 article one of these days. About half a year ago I read the Haber article and found the article to be of very low quality. I was tempted to improve it, but I gave (and still give) priority to new content. I contacted a chemistry editor (who since left) about it and he said that he let it go because he didn't want to discourage the author. Maybe you can have a better look at it (I noticed that you made a minor change). I miss for instance a sentence about the importance of atmospheric nitrogen binding. I've read (and believe it) that, without it, the Earth could not sustain 6 ×109 humans. But also a flow diagram would be nice, and (as far as I know) the electrolysis of water does not have any relation to the Haber-Bosch process. --Paul Wormer 03:32, 11 May 2008 (CDT)

Catalytic vs Thermal Cracking

I recommend to replace "Catalytic cracking of petroleum hydrocarbons was originally done by thermal cracking which has been almost completely replaced by catalytic cracking because..." by "Cracking of petroleum hydrocarbons for conversion of heavy to lighter fractions was originally done by thermal cracking which has been almost completely replaced by catalytic cracking because...". Guido van der Lans 08:49, 16 August 2009 (UTC)

Agreed and done. Thanks, Guido. Milton Beychok 16:16, 16 August 2009 (UTC)

Explanation of olefinic in first paragraph

In the first paragraph it is said that "It also produces byproduct gases that are more olefinic, and hence more valuable,...". This may need a bit more explanation. The term olefins is described further on in the text, in the section Chemistry. In my opinion the term olefinic is not generally known, and also not why olefins (alkenes) are more valuable than paraffins (alkanes). Guido van der Lans 08:55, 16 August 2009 (UTC)

Guido, the FCC produces butenes and other unsaturates. The butenes, in particular, are valuable as alkylation feed stock. As for the term olefinic, in my many years of work as a refinery process design engineer, that was always a common word used to describe olefins. In fact, it was more commonly used than the word alkenes.
Can you suggest some other wording to explain why olefins are valuable? Milton Beychok 16:33, 16 August 2009 (UTC)

Catalysts section

The Catalysts section is quite detailed, especially when compared with the high level Chemistry section. Especially the paragraph starting with "The catalytic sites in the zeolite..." may be too detailed for this article. I would recommend to add a figure here showing the zeolite structure(s). Guido van der Lans 09:01, 16 August 2009 (UTC)

I agree that a drawing or other image showing the structure of zeolite would be helpful. I tried to find such a drawing which was either public domain or for which permission to use could be obtained ... without success.
We are required in CZ to obtain permission to use images if they are not in the public domain. We can use images from Wikimedia Commons or Flickr but only if we can obtain the real name of the person who uploaded the image to Wikimedia Commons or Flickr, which is difficult to do because most Wikipedians participate under pseudonyms, as do most contributors to Flickr. Do you have access to a good image of the structure of zeolite that we can use without violating any copyrights? Milton Beychok 16:47, 16 August 2009 (UTC)
Guido, I finally found two graphics showing the molecular and physical structure of zeolites that could be uploaded into CZ and I just added them into the Catalysts section. I also drew another graphic showing the chemical structure of zeolites, uploaded it and also added it into the Catalysts section. Milton Beychok 23:24, 1 September 2009 (UTC)