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gasoline-ethanol-water system

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TexasChE:
Starting in May, the oxygenate for gasoline wil be 10% ethanol in straight run gasoine. Prior to this, the oxygenate was MTBE. The solubility of water in gasoline with MTBE was 0.02% and the solubility with 10% ethanol is 0.5%. I think this is weight per cent. At 60 deg. F and 0.55% water, a ethanol-water phase separates in the bottom of fuel tanks. If this fuel tank is at a service station, the operation must be shut down, the tank pumped out and the contents disposed of as hazardous waste at a cost of about $1 per gallon. Now what I am working on is a process and a chemistry for prevention and remediation. The chemistry involves a compound that reacts with water and doesn't just soluabilize it into solution. Noe for my question:
Do any of you have any data for the gasoline-ethanol-water system showing solubilities and phases?

billnotgatez:
I know that in aviation jet fuel (read combination of kerosene and gasoline) has additives in it that and anti-moisture and anti-microbial. I have forgotten what makes up those additives. Also when we get water in the gas tank up north, we add dry gas which I think contains iso propyl alcohol.  Dry gas seems to be a cheap authorized option.

I thought people in Iowa were using the gasoline ethanol mix without problems. You know the state that has corn.

eugenedakin:
Hi TexasChE,

There are two-sides-of-the-coin which need to be considered....

Negative aspects - ethanol (because of its polar groups and high concentration) promotes the removal of water vapour from the air.  Just letting ethanol stand in atmospheric air will increase the water concentration of ethanol.

Positive aspects - With the cooling of any fluid with a headspace (usually the headspace contains atmospheric air, such as above ground, and below ground storage tanks), the water that enters these tanks (from a rainstorm, or air) will always exist (in small amounts) in tanks.  Ethanol is a good chemical to have as it is not as toxic as MTBE, it emulsifies water into hydrocarbons (which increases the efficiency of internal combustion engines - to a certain level), and will form a oil in water emulsion (which prevents bottom-side corrosion due to the presence of non-emulsified water in a tank). 

I have developed many corrosion inhibitors, and there are two general methods of deterring corrosion from occuring ... coating, or pH neutralization.  But thats a whole other story .

Feel free to respond if you have any other questions ... keep the great ideas coming !!!!

Eugene

mbeychok:
Texas ChE and Eugene Dakin:

I just want to clarify some points in this discussion:

(1) Ethanol (or any other oxygenate) is not blended into "straight run gasoline" to make product sales gasoline.  In fact, sales gasoline contains very little, if any, "straight run gasoline".  Sales gasoline is a complex blend of butane, reformate gasoline, alkylate gasoline, hydrotreated treated cracked gasoline, hydrocracked gasoline, and various other gasoline components produced in petroleum refineries.

(2) MTBE is being displaced from sales gasoline blends because it has leaked into underground aquifers where it imparts a very unpleasant taste to the aquifer water even at concentrations in the parts per billion range and lower.  However, to the best of my knowledge, there have been no definitive or conclusive toxicological or epidemiological studies indicating that MTBE is "toxic".

(3) Ethanol has been used for many years in Brazil as automotive fuel. Brazil produces and uses about 14,000,000,000 liters per year of ethanol for such use.  In fact, the ethanol usage now accounts for about 40% of Brazil's total automotive fuel usage.

(4) In 2001, the USA consumed about 10,000,000,000 gallons of gasoline (called "gasohol") containing 10% ethanol and about 7,000,000,000 gallons of gasohol containing 5-7% ethanol ... which is only a very small part of our annual gasoline consumption.

(5) In neither Brazil nor the USA am I aware of any major problems caused by moisture in gasohol storage tanks or that it requires costs of $1.00 per gallon to dispose of any water drained from storage tanks.  I would be interested to learn where that statement was obtained.

(6) A fuel known as E85, which is a blend of 85% ethanol and 15% gasoline, is available on a small scale in some of the USA's Midwestern states.  However, using E85 requires special automobiles designed to handle such fuels and very few of such special automobiles are currently produced.

Milton Beychok
(Visit me at www.air-dispersion.com)

eugenedakin:
Hi mbeychok,

1) Chuckle. Your absolutely right, I dont think I know of anyone who uses straight-run-gasoline. It has too many inherent problems.  A portion of the straight-run-gasoline is used in creating the blend of gasoline everyone see's at the pumps.

Hmm... Toxicology of MTBE.  I just performed a quick search on google for MSDS's with MTBE.  Here is the part of an MSDS which I recieved on the first hit.

Toxicology
Possible carcinogen. Harmful by inhalation, ingestion or through skin contact. Irritant. Typical OEL 100 mg/m3.
Toxicity data
(The meaning of any abbreviations which appear in this section is given here.)
ORL-RAT LD50 4000 mg kg-1
IPN-MUS LD50 2400 mg kg-1
IHL-RAT LC50 23500 ppm.

I believe that you are saying there is no difinitive proof of 'MTBE toxicity' at low levels, such as ppm or ppb... right?  I believe that the hard-working environmental folks are just trying to minimize 'known' toxicity agents. 

3) Ethanol is an acceptable additive to fuel.  This depends on your aspect of 'acceptable'.  This can be argued from many different aspects, dealing from environmental to political, to economical. I don't want to go down this road, as no-one wins in this arguement (been there-done that).

4) I would doubt that ethanol blended gasolines would cause problem when water is added to gasohol, since the methanol will allow the water to be dispersed into the gasoline.  Gasoline without this or other emulsifying agents would seperate water from oil and the water would remain on the bottom of the tank.  The bottom of the tank is where most internal tank failures occur due to the presence of water.  Granted, there are many other types of failures. 

5) In practice, when water has been present on the bottom of a tank, and tank failure has not occured, addition of ethanol (with the appropriate additive package) can be added to disperse water into the fuel.   Caution must be exercised when performing this task.  Too much water in gasoline has adverse effects.

I hope this clarifies some of my comments.

Sincerely,

Eugene

 

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