3 replies to this topic

[obsidian_dust]

Dear all,

I need information about gasoline stability related to the existence of gum and olefin. My refinery has to deal with a condition where it has to blend a small amount of untreated delayed coker naphtha to the gasoline product. Even though we can minimize the proportion, still there are some issue related to specification that we need to ask,

1) Once I read a publication mentioned that for long term gasoline storage – up to 6 months – the acceptable olefin content is 3 vol % maximum worldwide. Is it correct? Is the number 3% has already included cyclo-olefin and cyclo-diolefin? Should there be any special concern for the existence of those cyclo-olefin forms? If so, what is the maximum limitation for cyclo-olefin and cyclo-diolefin in gasoline?


2) Is there any correlation between olefin content in a particular blend of gasoline with its induction period and/or the method to analyze the induction period? Once I heard that the induction period should be more than 1000 minute for a sample which has more than 20% olefin.

3) Is it necessary to check again the olefin content and existent gum after oxidation stability test conducted to a gasoline sample (induction period test, such as ASTM D-525)? Once I saw a gasoline sample which has been analyzed twice for its existent gum (both washed and unwashed) and olefin content (once before stability test and once after). It was obvious that there are significant increases in both olefin content and gum after stability test. I just wondering whether one analysis each for olefin and gum before oxidation stability test are adequate and have already represented condition expected during long term storage.

Sorry for my lack of experience. This is a new thing for me since this is the first time we deal with such an issue. Even my country’s gasoline spec hasn’t been specifically prepared for that. Any response will be highly appreciated.

Best regards.

[Zauberberg]

Obsidian,

Go through the thread: http://www.eng-tips.....cfm?qid=174036 and read it carefuly, it was posted by one of my colleagues from refinery once when they started experiencing high deltaP across the Pyro gasoline Hydrotreater reactor. The problem was originating from high diolefin content in Pygas.

I would say that diolefins and not olefins are the main precursors for gum formation but I might be wrong. Let's hope to hear comments from someone who is more familiar with the subject.

[ankur2061]

Obisidian,

For gasoline properties, storage and performance you should refer the following article:

http://www.faqs.org/...art1/index.html

Regards,
Ankur.

[obsidian_dust]

Both links help. Thank you so much.