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12AX7
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| Quote: | Originally posted by Elawr
What does ethyl acetate smell like? |
Not far from ether I'd say. Maybe more, er, "body" or something, but I don't associate it with any particular fruit or anything.
Tim
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stoichiometric_steve
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| Quote: | Originally posted by 12AX7
| Quote: | Originally posted by Elawr
What does ethyl acetate smell like? |
Not far from ether I'd say. Maybe more, er, "body" or something, but I don't associate it with any particular fruit or anything.
Tim |
sometimes cantaloupe melons smell like ethyl acetate.
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CycloKnight
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Acetaldehyde
There is another route to acetaldehyde that I didn't see mentioned in the posts above.
This is the method used here:
http://www.sciencemadness.org/talk/viewthread.php?tid=2223&a...
...to convert cinnamaldehyde to benzaldehyde.
Acetaldehyde is the main byproduct produced in that process.
Read psychokitty's post in the link, it contains a quote from the patent and also mentions the acetaldehyde formation.
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markgollum
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The attachment
I re-scanned the pages on the lowest quality setting and am now at 560Kb so it should work this time.
Attachment: The Hydration of Acetylene.pdf (556kB)
This file has been downloaded 1691 times
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Zinc
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Be careful when working with acetaldehyde. It is a probable carcinogen.
http://en.wikipedia.org/wiki/Acetaldehyde
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JohnWW
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If it really is a "probable carcinogen", then everyone who drinks alcohol is at risk, because it is an intermediate degradation product of ethanol. I
do not think so.
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guy
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That's probably why drinking IS bad for you. 
http://www.reboundhangover.com/acetaldehyde.htm
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Rosco Bodine
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Update :
Found an interesting old German acetaldehyde patent that
needs translation to English ....if anyone would be
so kind .
[Edited on 2-11-2006 by Rosco Bodine]
Attachment: DE422729 Acetaldehyde in 90+% Yield via Air Oxidation of Ethanol using Silver Wire Catalyst.pdf (69kB)
This file has been downloaded 1364 times
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Rosco Bodine
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And for electrolytic oxidation of ethanol to acetaldehyde ,
the yield is quantitative when the electrolysis is carried
out with the voltage limited to the range of 1.3 to 1.66 volts using a platinum anode . See the attached page .
Perhaps another anode material might work adequately well .
Both of these references are from publications in the
ScienceMadness Library .
Attachment: Page 60 from electrochemistry_of_organic_compounds.pdf (435kB)
This file has been downloaded 1448 times
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fractional
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@ Rosco Bodine
Et voilá, the English translation...
I don't think that this process is more interesting than the standard one using copper-wire/ copper-mesh as catalyst.
This method seems not to get many favourable reviews, but I think it is perfectly reasonable once an important modification is applied: External
heating of the copper-catalyst with e.g. a bunsen-burner in order to kick-start the reaction is clearly not practicable on any but the smallest
scales, but one can also use the copper wire as direct heating element by passing an electric current through it. This ensures an equal and controlled
heating of all the copper surface.
The setup to use is a pipe with a spiral of copper-wire inside that's connected to a low-voltage power supply with sufficient current to bring the
wire to red heat. The Volts/Amps rating of course depends on the length and the thickness of the wire used.
Attachment: Method for the Production of Acetaldehyde from Ethanol.pdf (11kB)
This file has been downloaded 2890 times
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Rosco Bodine
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@fractional
Thank you for that translation .
Silver has such a pronounced catalytic effect on the
oxidation of ethanol selectively to acetaldehyde , it
makes me wonder if a silver or silver oxide anode may
have similar value in an electrolytic cell .
Also concerning the value of silver and copper both as
contact catalysts for the air oxidation of ethanol at elevated temperature .....
the old German patent encourages an idea which I have been considering for an experimental method and catalyst which could be useful for the oxidation
of ethanol to acetaldehyde .
There is a familiar example in many chemistry books
about how metallic silver will precipitate from a solution
of silver nitrate upon a piece of copper wire immersed
in the silver nitrate solution .
And there are also methods for the precipitation of metallic copper from solutions of copper salts using organic reducing agents .
While researching refractory materials I came across a
high fired granular porous clay material which is used
as an artificial soil for aquatic plants in decorative ponds
and aquariums , as a substitute for ordinary gravel ,
and it occured to me that this might make a useful carrier
for a catalyst . A similar material is a porous alumina
which is used in water filtration as a substrate on which
grow beneficial bacteria and algae , and this ceramic
could be broken up into granules using a hammer , and
the granules could also be useful as a porous substrate
for carrying a finely divided catalyst .
http://www.drsfostersmith.com/product/prod_display.cfm?pcati...
This sort of ceramic filter media is available in different
molded forms from aquarium suppliers and probably
pet shops .
The idea for the catalyst carrier is to agitate the granulated material violently in a copper salt solution
as reduced metallic copper is being precipitated into the pores and onto the surfaces of the granules . And then
subsequently to agitate the copper bearing granules
violently in a solution of silver nitrate so that metallic silver is also deposited . The granular material is then
dried and poured and tamped inside a long copper tube ,
whose inside walls may also have been silvered by
filling the tube previously with silver nitrate . Alternately the copper bearing granules might be placed in the copper tube first , and then the
assembly silvered by circulating silver nitrate solution through , depositing
the metallic silver on the granules and the inside walls
of the copper tube simultaneously . Afterwards the
catalyst filled tube is spiral wrapped into a coil but having
a conical form , as if it were coiled around the outside of
a funnel being used as a form for the winding . This
funnel shaped coil can be inverted above a single burner
on something like a gas hotplate or camp stove burner ,
so that the entire coil catches the heat from the one burner , distributed across a considerable length of
catalyst filled tube which forms the coil , having its free ends brought horizontally away by some distance to provide cooled sections as intake for
the alcohol and air vapor and exhaust of the acetaldehyde to a separate
condenser .
An aquarium pump could supply the airflow to an airstone
at the bottom of a column of ethanol , and the richness
of the entrained vapor in ethanol could be varied simply
by warming or cooling the ethanol through which the air is bubbled . A three way needle valve manifold as is
used on aquariums for balancing the airflow between separate airstones could be used for achieving a proper mixture , if it was found necessary to
blend the vapors
from the ethanol evaporator with additional plain air .
The acetaldehyde vapors exiting the catalytic section
could be initially cooled in a coil air condenser , and then
in a water cooled coil section , then ice water cooled
section , and finally captured by bubbling through an
airstone into icewater in a column cooled by an ice salt bath .
Regarding your suggestion to use electrical heating of
a copper coil , it presents difficulty due to the enormous
current which would be required for causing copper to
get hot from IR heating . What would be required is
some sort of inductive heating of a shorted loop , as
if it was a stalled motor armature and the field coil would be a substantial endeavor . If a copper coil was
to be used , it would be easier to wrap it around some
sort of sheathed cylindrical heating element , and let
the isolated nichrome element in the core do the job of
heating the copper .
An idea that just occurred to me is related to that copper braided sleeve material woven of fine wire that is used as the outer conducter in coaxial
cable . That braided copper
sleeving could be silvered by immersion in silver nitrate ,
and it would probably work beautifully inside a copper tube
loosely filled with parallel pieces of the braid . Alternately
the braid could be cut in short lengths and pushed inside
the open end of the tube by the end of a dowel , like
pushing wads into a muzzle loaded rifle using a ramrod .
Silvered copper may work fine as a catalyst , providing
the greater economy of the copper as a substrate for the
silver which has greater activity and efficiency .
Tinned copper braid is commercially available , and it may just be that silvered copper braid is also available , and if so it could be used directly
. I know that silvered copper wire
is manufactured , so it seems logical that somebody is probably weaving copper braid using silvered copper wire ,
for use in some high end coaxial cable or other application .
[Edited on 2-11-2006 by Rosco Bodine]
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fractional
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I fear I have not been clear enough before: the copper wire is the actual heater, it is not heated by some external source with which it must
exchange heat energy by radiation. The currents needed to heat it up to red heat are not all that outrageous for a typical application. I have done
some back of the envelope calculations:
Used PC power supplies are great and dirt-cheap power sources for low voltages and high Amps. Let's assume one rated at 5 Volts, 20 Amperes. The
external resistance needed to draw the rated current at the rated voltage is 5V / 20A = 0.25 Ohms.
A copper wire with a diameter of 0.5mm has a resistance of about 0.0876 Ohms per meter. The length of this wire needed to give 0.25 Ohms is 0.25 /
0.0876 = 2.85 meters. This length of wire can be easily fitted as a kind of spool or bobbin inside a reasonably-sized (glas)-pipe.
Let's calculate the expected temperature of this spool operated at 20 Amperes: This depends on the surface area of the wire-assembly (l=2.85m,
dia=0.5mm), which is 0.0045 square-meters. It also depends on the emissivity epsilon, which is 0.13 for polished copper (from published tables of
materials properties).
The temperature assuming radiative heat transfer only (which is of course a major simplification) is given by Stefan-Bolzmann's law:
Texp4 = q / (Sigma*epsilon*SurfaceArea) + Tenv exp4
T is the temperature of the wire in Kelvin, Tenv is the environmental temperature in Kelvin. q is the power, sigma is Bolzmann's constant
(5.67051exp-8).
When you put in the numbers q=100W, Tenv=20 degC = 293 Kelvin, SurfaceArea = 0.0045 m2 the expected temperature of the wire is 1318 Kelvin or 1045
degC, which is actually way beyond red-hot.
Of course there will be losses in the system by conduction and convection, so the temperature will be lower, but I think this is a good starting
point, and I think it shows that such a system is feasible.
I have read with interest your ideas about producing a copper catalyst-bed with a high surface area. I am not sure, however, if this will really help
for the specific purpose of producing acetaldehyde. The main point of the German patent is that too finely divided silver makes the reaction too
violent and reduces the yield, so that "more compact" forms of the catalyst should be used, so I think that the compact form of copper wire should do
the trick nicely.
I have not tried this out yet, because I am currently trying to oxidise ethanol using TCCA, with limited success so far (yield 1ml of acetaldehyde
using 60ml of ethanol...). If this turns out to be a no-go I will come back to this copper-wire method.
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Rosco Bodine
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I have been doing too many ammeter shunt calculations lately and handling too large conductors ....losing perspective Of course you are right , and coiling
the element like a long spiral spring would allow for
even larger wire to be used . If this was wound upon
a solid rod and placed inside a glass tube , the vapor would be forced the travel the spiral groove and
would get very good contact and intermixing in
the reaction zone .
I still think that using silver plated copper may have advantage , as the reported yields for the silver are
much higher than for copper alone , in the references
which I have seen , the yield reported for silver is
increased by 50% over that gotten for copper in
a single pass oxidation .
Also I found that the silvered copper braid material is indeed available in various sizes . Alpha wire products
is one of the suppliers .
http://www.electrospec.com/alpha/product_list.asp?c1=05&...
The silver plated tubular braid material is available down to
1/16" ( 1.6 mm ) size , and depending on the cross sectional
area of the conductors , this may also be within reach for
electrical heating if it was used as a coiled element .
BTW , I didn't do the calculations , but just off hand it would
have been my guess that about 400% or even much more current would have to be put through that nearly 3 meters of copper wire to get it red hot in
free air initially , but of course after the reaction starts , the exotherm of the reaction will keep the catalyst plenty hot , and the power supply
would only need to labor hard for a brief time to initiate the reaction .
[Edited on 2-11-2006 by Rosco Bodine]
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gsd
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Let me make it clear that I have not gone through this thread completely as it is fairly a long one; so kindly excuse me if I am repeating the posted
matter.
While doing my engineering, I had done summer vacational training in an "ethanol to acetaldehyde - air oxidation" plant.
Ethanol vapours and air are premixed and immediately fed into a reactor which is a squat cylindrical vessel having vertical tubes on which several
layers of gauze made from very pure silver metal are tightly wound. The vapour air mixture passes across this layer of catalyst. The reaction is
exothermic and the bed temperature is maintained at 550 Deg C., by coolant circulation in the tubes. The contact time is very short ( < 0.1 sec),
per pass conversion is about 48 % and yield about 85-90 %
The Interesting this about this reactor was the startup procedure. To this big reactor ( Diameter about 1.2 m, I don't recollect exactly) are attached
3 small pilot reactors of 200 mm dia and 300 mm length, at 120 Deg angle. These small reactors are packed completely with copper wire gauze and are
heated with electrical resistance heaters packed within the copper wire gauze layers.
The same feed of ethanol + air mixture is passed thru' each of there reactors and the outcoming hot vapours from small reactors are directed onto the
silver wire gauze of main reactor. These vapours slowly heat up the silver catalyst and after it is above 300 Deg C., Feed is stared to the main
reactor and the pilot reactors are discontined.
gsd
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Jdurg
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I haven't had a chance to read through the entire thread and while it's been many years since I had biochemistry, would it not be possible to take
some ground up beef liver (which should be fairly cheap) and use the alcohol dehydrogenase contained within to convert the ethanol to acetaldehyde?
Or, as I'm guessing, is the yield so poor and the extraction so complex that it's really not worth it?
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
http://maddox.xmission.com. |
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Rosco Bodine
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I wonder what the catalytic heater element used on
those propane fueled portable camping and icefishing heaters would do if it was fed an ethanol vapor fuel
instead of propane ?
There may already even be such infrared heaters designed
to operate on denatured alcohol , and it could very well
be that acetaldehyde is an intermediate oxidation product ,
which could be made the principal product if the air supply
was restricted to prevent its further oxidation .
Mooooo......Mooooooo , Mooooooooo 
Sorry , I couldn't resist
@ fractional
Have you taken a look at that Dony-Henault article
reporting a quantitative yield of acetaldehyde via
electrolysis at a specifically limited voltage of 1.3 to 1.66 ?
That was on a platinum anode , and I wonder what silver
would do .
Anybody got access to that reference ?
Dony-Henault
Ztschr. f. Elektrochemie 6 , 533 , ( 1900 )
[Edited on 2-11-2006 by Rosco Bodine]
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S.C. Wack
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Tried that when the sportcats came out a few years ago. Oddly enough I found those better at making formaldehyde (with MeOH obviously) than
acetaldehyde, though my experiments were crude and so far just for hahas. Not being engineering-minded, I felt that experiments with it were best
directed elsewhere.
Vapor indeed. Unless the feed of either air or vapor is dilute much of the alcohol will burn off due to the exothermic self-sustaining nature of the
reaction and the small amount of heat necessary to get it going.
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Rosco Bodine
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What I was thinking is maybe put the catalytic burner head inside a sealed chamber with an observation port
and a thermometer , and control the air supply and the
alcohol vapor flow to the burner . Fire it up in a normal
heat producing mode where it is getting plenty of air
to burn the fuel all the way to CO2 , and then start
reducing the air until it is outputting CO , and then gradually reduce the air further until hopefully the
aldehyde is what is being produced . There may be
a niche condition of temperature and mixture where
the reaction would proceed pretty well at a stable rate
and produce lots of the desired aldehyde .
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fractional
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Rosco,
I also think that silver-plated wire is the way to go. It gives you the catalytic performance of silver at the price of copper wire (or just a bit
more). The conductivity of the wire will not change much, but the emissivity will. I found a figure for the emissivity of silver plating of 0.06. For
the previous example of a length of 2.85m of 0.5mm dia. wire siver-plating would yield a temperature of 1326 degC which is probably too high, even
considering losses. A 0.6mm dia. wire, length 4.1m, brings you back to 1123 degC, which is probably more realistic.
All these calculations show that the emissivity is a crucial factor in the calculations and the published figures are often miles apart, so if one
wants to put such a system in place one should perform a few dry-runs first, using a power source that can be regulated somewhat.
> @ fractional
> Have you taken a look at that Dony-Henault article
> reporting a quantitative yield of acetaldehyde via
> electrolysis at a specifically limited voltage of 1.3 to 1.66 ?
> That was on a platinum anode , and I wonder what silver
> would do .
> Anybody got access to that reference ?
> Dony-Henault
> Ztschr. f. Elektrochemie 6 , 533 , ( 1900 )
Yes, I did read it and I find it extremely interesting. A platinum electrode is one of those things one would like to have, isn't it? Electrochemistry
is not my strong side (to put it mildly) so I don't know what the use of a different anode material would do, e.g. the effects of overvoltage, etc. I
tried to find an article from 1899 also in the "Zeitschrift f. Elektrochemie" on the production of Chloral by electrolysis, but with no success so
far.
What I can say is that if some good soul scans the article I will be more than happy to translate it and put it on the board.
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not_important
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SCW is right, once you get above a few hundred C and there is oxygen present then the reaction tends to go to full oxidation and thermal runaway. The
industrial processes use a rather high speed flow of reactants to help avoid too much loss from that route, like NOx production from air - quickly
heat and chill.
Another thing to remember is that the Cu/Ag route will produce aldehyde without any oxygen present, the added O2/air is used to remove hydrogen to
force the reaction further to completion. Those catalytic burners are targeted at full oxidation of hydrocarbons, they may not function well for this
more limited reaction.
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Rosco Bodine
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Some of the campstoves and lanterns which burn white gasoline use a pressurized tank for the liquid fuel which
is squirted under pressure through a very small orifice
into a larger bore tube which is heated by the burner ,
and the liquid spray is flash boiled to a vapor in that
" vapor generator tube " which preheats and vaporizes the liquid fuel on its path to the burner , scavenging heat from the final output for the
preheating of the fuel .
The same principle and indeed the same fuel tank and
fuel generator tube , perhaps with a couple of added
sections in length .....might be directly applicable for
an ethanol vapor generator if the copper tube containing
the catalytic material was coiled around the generator
tube and then insulated around the outside with a sleeve
of kaowool or fiberglass . A thermocouple could be attached to monitor the temperature . The first few inches of the generator tube and the first
three or four
coil loops of catalyst containing tubing could be left partly uncovered with insulation so it could be exposed to
external heating by a bunsen burner for initial heating
when firing up the apparatus . A Tee fitting and needle valve could be interposed between the fuel tank and the vapor generator tube , or perhaps at
a third of the length of the catalyst containing tube , for admitting air as needed to speed the warmup of the apparatus by complete oxidation of the
fuel initially , which should get the converter temperature high enough , that the oxidation could then be transitioned to the more anaerobic
production of acetaldehyde by gradually reducing the airflow .
Supplemental electrical heating could be provided if needed by a cylindrical heating element , a " watt rod " along the
outside of the coil under the insulation , or a few of the coils could be wound around the heating element directly .
The idea of loading the catalyst inside a coil of copper tubing
is perhaps not the optimum arrangement , if a short contact
time with the catalyst is what is desired , a straight
section of larger tubing , or a concentric arangement of
inner vapor tube and an outer tube containing the catalyst
may serve better . A compact assembly the size of a soup can may have superior characteristics to something larger the size of a map case or
blueprint tube .
Another arrangement of catalytic burner which may be applicable is similar to the vertical " fluidized bed " concept . A funnel shaped copper bell ,
like a large reducer adapter sleeve solder fitting at the large opening and threaded at the smaller bottom opening ,
could be filled with layered pieces of silver coated copper wire braid and chopped wire whiskers , and fed with ethanol vapor from the bottom through
a copper tubing having two or three loops of the tubing wound around the outside
of the reducing adapter to provide preheating of the entering vapor . A grid of wires laced across the large opening could be used to keep the spongy
wad of catalyst pieces secured inside the catalytic " burner " head . Something like this would provide a rapid transit and brief
contact time for the ethanol vapor . A length of straight
copper pipe could be added to the copper bell to increase
the depth of the catalyst bed if needed , until the optimum
reaction zone dimension for the particular apparatus was discovered by testing .
To simplify greatly this whole endeavor I think it would be best to first use a modification on the patents method .
The catalytic reactor section need not be made of quartz
nor should the wire material be made of pure silver if
my earlier guess is correct that silvered copper braid material
should work about as well . All that should really be required
is a straight four inch section of 3/4" copper tube stuffed with layers of the catalyst wire mesh and having its ends
fitted with 3/4" to 1/4" brass or stainless compression reducer couplings for the vapor inlet and exit . The catalyst section is compact enough to be
preheated easily by a meker burner with a wing adapter flame spreader . The brass compression couplings on the ends of the catalyst chamber could be
wrapped with fiberglass ribbon for insulation , and the bare 3" middle section heated by the burner . The smaller copper inlet line could be hairpin
bent
( U-bend ) back across the coupling and spiraled around
the catalyst containing section for vapor preheating , a
smaller copper capillary tubing such as is used in refrigeration would be needed for this tight spiral preheater .
I believe I have seen this small copper capillary tubing used
as supply tubing to pilot lights on gas appliances , and I will
do some shopping and scrounging to see what can be found in the way of fittings for making a modest lab scale device .
The silvered copper braid is something which will have to ordered , but simply treating ordinary copper braid scavenged from coaxial cable with silver
nitrate may be the better approach in keeping the experiment to over the counter materials .
For the vapor - air mixture control , the setup will be based
on a bubbler in ethanol and an aquarium pump as described earlier .
[Edited on 3-11-2006 by Rosco Bodine]
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Eclectic
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There is a knitted copper mesh material available from www.partyman.se and other alcohol oriented places that they sell for column packing. It's used industrially for scouring the crud from plastic
injection molding machinery parts. Chore-Boy (used to be Chore-Girl brand) copper scrubbers are similar.
[Edited on 3-11-2006 by Eclectic]
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Rosco Bodine
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Yeah I think this sort of setup is entirely workable
and could be made into a suitcase sized apparatus .
If ~90% yield is gotten in a single pass through
a catalytic converter of compact size , that is
entirely efficient enough for a practical method
and source for acetaldehyde as an intermediate .
Thinking further on the design , any unreacted
ethanol vapor could be stripped from the output simply by bubbling through an airstone in warm water , the alcohol would enter the water , but the
more volatile acetaldehyde would blow through , while it could
be cooled further in an empty glass jug in an ice bath ,
and then bubbled into cracked ice and water in a
cylinder cooled in an ice salt bath . I believe that this
" Two jug - one tall bottle " sort of arrangement and
using gas dispersion stones in the first and last ,
with a swirling flow in the second , would work better
for purifying and capturing the extremely volatile
product in frigid water solution , than would trying
to condense it in conventional condensers .
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Aqua_Fortis_100%
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Acetaldehyde from PET ?!?!?!
firstly sorry by ressussiting this old thread but when i searched some things about acetadehyde in portuguese , the google show me a special result :
| Quote: | from this page :
O acetaldeído é subproduto da degradação do PET. Ele é formado quando a resina PET é submetida a altas temperaturas, normalmente utilizadas na
fabricação e transformação da resina, onde o polímero é aquecido acima de sua temperatura de fusão.
A preocupação com a presença de acetaldeído nas embalagens de PET se deve à alteração de gosto que este pode causar no produto embalado.
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something as :
" the acetaldehyde is a subproduct of the decomposition of PET. It is formed when the PET resin is submited high temperatures , usually used in
resin manufacture and modification, where the polymer is heated above of their melting point.
The worry with the Acetaldehyde presence in PET containers is due the taste which this can cause in the wrapped products (foods) ."
^sorry, this is a poor english but is some compreensible (eh?) ^
anyone tried getting acetaldehyde from this "method"? what about???
| Quote: | originally posted by vulture:
The main problem with the production of acetaldehyde from ethanol is that when you use water as a solvent, you're always wasting aldehyde by
conversion to acetic acid.
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I'm actually only interested in acetaldehyde due the pentaerythritol manufacture... if i try distill this directely in cooled CHOH (with some
Ca(OH)<sub>2</sub> this will improve the yield of the
CH<sub>3</sub>CHO coleted? Because the acetaldehyde react with formaldehyde (before?) the conversion for acetic acid in contact whit
water..(?????)
or maybe, try DRY destill in the receiving cooled flask, then adding this in calcium hydroxide/formaldehyde solution..
thanks and sorry for anything...
[Editado em 21-1-2007 por Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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guy
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Posts: 982
Registered: 14-4-2004
Location: California, USA
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Mood: Catalytic!
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Ethanol + copper acetate (or palladium) + Sodium acetate(base) ---heat---> Acetaldehyde??
Make sure there is no water or else it will convert to acetic acid.
============
Copper catalyzed alcohol oxidation to ketones and aldehydes
Abstract:
An efficient, copper-based catalyst has been discovered that oxidizes a wide range of
alcohols into aldehydes and ketones under mild conditions. This catalytic system utilizes
oxygen or air as the ultimate, stoichiometric oxidant, producing water as the only
by-product.
[Edited on 1/21/2007 by guy]
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