I gave up chemistry long time ago but i believe you are very very right. I
think that some more advanced chemical consepts must be in the JTF site for
those interesting. I can contribute more in analytical chemistry
instrumentation setup.
Stelios
----- Original Message -----
From: "bob allen" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, January 14, 2005 7:46 PM
Subject: Re: [Biofuel] Iso-propanol
hello Kieth, Andy, et al,
Why base catalyzed transesterifcation works well with Methanol but not so
well with most other alcohol. (another little chemistry lesson).
Among common alkyl alcohols such as Methanol (MeOH) Ethanol (EtOH),
isopropanol (iPrOH) and higher homologs, only MeOH has a pKa lower than
water.
MeOH 15.5
HOH 15.7
EtOH 16.0
iPrOH 16.7
What this means is that when you mix NaOH or KOH with Methanol,
equilibrium favors formation of the Methoxide ion -OMe :
MeOH + KOH --> K+
+ - OMe + HOH but for the others the Hydroxide ion is favored:
iPrOH + KOH <--- K+ + -OiPR + HOH
Only when the right side of the equation is favored, is a significant
concentration of the alcoxide present. It is the alcoxide which
accomplishes transesterifcation. When the left side is favored,
significant hydroxide is present. Hydroxide causes significant
saponification. The left side of the equation is favored for all
alcohols whose pKa is higher than water.
There are tricks to shift the equilibrium (Le Chatelier's Principle) but
it gets more difficult, expensive or both.
Keith Addison wrote:
Hello Andy
I am helping a friend setup a reactor and he has 4 55 gallon drums of
IPA. He has little time so it is slow going, but I will let you know
how it goes. Since the it has the higher boiling point we will run at
a higher temperatures.
I am interested in trying the BIOX reaction as well but want to make
sure that the reactor is air tight first.
:-) I'd suggest you check on whether the process is watertight before you
start bothering about the reactor. (It ain't!) Rather thoroughly
discussed here previously, a few times. I think calling it "the BIOX
reaction" might be somethinbg of a misnomer, for one thing.
See:
http://infoarchive.net/sgroup/biofuel/35434/
http://infoarchive.net/sgroup/BIOFUEL/35449/
Check the links in those posts.
Best wishes
Keith
Andy
On Fri, 14 Jan 2005 09:12:26 -0300, Andres Yver <[EMAIL PROTECTED]> wrote:
> On Thursday, January 13, 2005, at 05:50 AM, Jan Warnqvist wrote:
>
> > Hello there !
> > Is there anyone who has experience in isopropyl alcohol or its
esters
> > as fuel components ?
> > Jan Warnqvist
>
>
> Here's a pdf out of Iowa State University:
>
> www.me.iastate.edu/biodiesel/Technical%20Papers/Wang%20Intro.pdf
>
> The production of isopropyl esters and their effects on a diesel
engine
>
> "The scope of this research was to improve the cold weather properties
> of neat biodiesel
> by investigating the manufacture of isopropyl esters from soybean oil
> and yellow grease.
> Isopropyl esters have a lower crystallization temperature compared to
> methyl esters from the same source material."
>
> www.me.iastate.edu/biodiesel/Technical%20Papers/
> Wang%20Equip%20Analysis%20Results.pdf
>
> Optimizing the Transesterification Process for Isopropyl Esters
>
> "Producing isopropyl esters requires the use of isopropyl alcohol as
> opposed to methyl
> esters, which utilize methanol, or ethyl esters, which use ethanol.
> Commonly, most biodiesel
> consists of methyl esters and methanol is used since it is cheap and
> widely available.
> Methanol is priced between $.04-.24/lb [14] and is the fourth largest
> organic chemical in the U.S. in terms of volume. Isopropanol, on the
> other hand, is priced between $.20 - .34/lb [14], which makes it more
> expensive to make isopropyl esters. However, the yield for isopropyl
> esters is about 10% more than methyl esters because of the heavier
> molecular weight. So, this partially compensates for the increased
> cost."
>
> hth,
> andres yver
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--
------------------------------------------------------------------
Bob
/ozarker.org/bob ------------------------------------------------------------------
-----------------------------------------------------------------
The modern conservative is engaged in one of Man's oldest exercises
in moral philosophy; that is, the search for a superior moral
justification for selfishness
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