I want to build or use a proper heating method for dry distillation eg. sodium benzoate. The proplem is what do I use.
First off I want to choose between electric or gass and I want to use an old lpg bottle that I have adapted using copper pipe and flare fittings.
It seems easier to simply throw the thing on top of a burner and just raise or lower the gass, but I've never used a open flame and how would I
control the temp? Maybe that doesn't matter.
If I go electric, Is it better to get an incoloy element, bent it to fit and wrap the thing with ceramic bankets and put that in a tub so it looks
like a mantle? At first I thought about using castable cement and impregnating it with kanthal then insulating but I don't think it's as easy as it
sounds. Also I've been told by the suppliers that most castables have too much iron which will damage the wire.
Also, castable is heavy and I can't find suppliers who stock the stuff than you can manually groove after it's set so that you can imbed the wire and
cement it in. If I use an incoloy element backed by blankets, I don't think I'll get the even heat distribution that I'm looking for. So in that case
I'm thinking about imbeding it in cement. Surley that's ok, I'm only looking at 400 - 500 deg C. Maybe heat distribution that doesn't matter that
much.
How would you do it?chemrox - 15-5-2009 at 00:24
I don't understand. Is it that you first melt and then boil your material? Or do you sublimate? If you plan to use a metal vessel you should
probably exclude oxygen with an inert gas. Open flames are traditional in our science and you aren't working with a flammable liquid are you? A
gas flame affords an easy temperature control method but a steel vessel makes it hard to see what's going on inside unless you had a quartz window
built in. By the way the words you wanted were, "electricity" and "gas."Lambda-Eyde - 15-5-2009 at 01:30
I think he refers to the production of benzene by distillation of sodium benzoate with NaOH. There's a big thread on it, it's easy to find with the
search function. I believe you will find what you are looking for there. watson.fawkes - 15-5-2009 at 06:02
Also, castable is heavy and I can't find suppliers who stock the stuff than you can manually groove after it's set so that you can imbed the wire and
cement it in.
There's a great trick I've read (and will be trying out soonish) to solve exactly this
problem. Take a length of rubber foam gasket material, closed pore, and wind it in a spiral are the center form when you pour. The void left when you
remove the gasket is the channel for your heating element. Because the gasket material is flexible and compressible, it comes right out of the
channel. Thanks to Dave Gingery for this tip, from his book Li'l Bertha, A Compact Electric Resistance Shop Furnace.
If you're worried about iron contamination when the heating element is in the channel, there are ceramic coatings such as ITC-100 you could use. Magpie - 15-5-2009 at 06:37
It would be good if we knew at what scale you want to do your dry distillations. Ie, 100 mL, 1 liter, 5 liters, etc.
In my small scale experience with dry distillation of Na benzoate the principal problem was the poor heat conductivity of the dry powder. This
problem would only get worse at the larger scales.
Some of the investigators did have some success at the larger scales. Specifically note the work of ordenblitz.
[Edited on 15-5-2009 by Magpie]angelhair - 3-6-2009 at 16:58
Yes I was familiar with the benzene thread but they never really discussed heating methods and temps in detail. My initial question was simply this;
Is electric better than gas as far as ease and quality of control, saftey and quality and yield of product. The answers will probably be subjective.
In any case I've chosen to try the castable route. Ciement fondue looks OK but the iron content is high so I've started with a AlO3/Si02 mix with
total iron content about 0.6%.
I used 5mm x 5mm square EPDM rubber as mentioned for the grove and holes which works very well. The rubber was coiled on to the bottom of the 4.5kg
lpg bottle using hot glue, which to my supprise worked well too but you have to be quick.
I plan to make fenske rings out of 3/4 copper and use that for better heat distribution.
BTW, why is ITC-100 being suggested here and other posts as a coating for the elements? After what I've read the only choice would be ITC-213 which is
apparantly formulated specifically for metal protection. ITC-100 seems to have insulating properties. How could this be good for the element?watson.fawkes - 3-6-2009 at 18:01
Ciement fondue looks OK but the iron content is high so I've started with a AlO3/Si02 mix with total iron content about 0.6%.
I used 5mm x 5mm square EPDM rubber as mentioned for the grove and holes which works very well. The rubber was coiled on to the bottom of the 4.5kg
lpg bottle using hot glue, which to my supprise worked well too but you have to be quick.
[...]
BTW, why is ITC-100 being suggested here and other posts as a coating for the elements? After what I've read the only choice would be ITC-213 which is
apparantly formulated specifically for metal protection. ITC-100 seems to have insulating properties. How could this be good for the element?
Glad to be of help.
I suggested ITC-100 to coat the groove, not the element. The main hazard, though, is iron content in the refractory. If you're already using a
low-iron formula, you may not need it at all.
One warning: If you're operating in a reducing environment (pretty much anything with some free carbon or carbon-monoxide) your electrode life will be
greatly reduced. There's a passivating oxide layer that develops on exposed heating elements; a reducing environment removes that. No need to rebuild
your furnace, though. What you need is a muffle for it.
You could also coat the elements. The instructions for ITC-213 tell you how to coat them. If this furnace is for a single purpose, this might be easier. If you want to use it for
multiple processes, to avoid cross-contamination you can use a single muffle per process.entropy51 - 4-6-2009 at 15:01
If you're going for small scale in glassware, I'd recommend using a sand bath to distribute the heat more evenly. For dry distillations, I heat the
sand bath on an old-fashioned hot plate with an exposed spiral-wound nichrome heating element contained in grooves in a ceramic support. I control
the heat with a variac.
If you're going for industrial scale, you will need something more complicated.roamingnome - 4-6-2009 at 18:44
Ive read that benzoate thread and the conventional heat adsorbing problem was indeed the issue.
If carbon/graphite is not suspected to adversely affect the reaction, its use as a sensitizer in the microwave spectrum is unmatched. Benzene carbon
absorption should not be an issue at temperature. people are melting silver with it even.
an intimidate mixture of the three components may produce benzene in under 10 minutes....
i could perform a test tube reaction in 2 minutes from posting this. i guess that's the cart before the horse again...
++++++++++++++++++++++++++++++++++++++++
i apologize.. this mixture readily begins to ignite and burn with a filamentus glow in some spots...
the vapours that wafted around in the larger outer vessel smelled much like styrene. maybe a graphite rod will be better then a fine powder
[Edited on 5-6-2009 by roamingnome]
[Edited on 5-6-2009 by roamingnome]angelhair - 5-6-2009 at 17:44
Quote:
I suggested ITC-100 to coat the groove, not the element. The main hazard, though, is iron content in the refractory. If you're already using a
low-iron formula, you may not need it at all.
Well now it makes sence, Although, ITC-213 is completely unavailable to me. I was at a kiln manufacturer the other day, I told him what I wanted to do
and they gave a mixture that they make up themselves. They use it as an adheasive and it's a good conductor of heat up to 1700 deg C. I'll experement
coating the element with this and I'll also coat the groove with ITC-100 and see what happens.
One of the reasons the adheasive appeals to me is because I was told that fresh refractory cement that I used will not stick to dry cement of the same
type very well and that's what I want to fill the groove and element with. I have air set cement but even that has 0.8% iron. I know there's 0% iron
grout out there but I haven't found any yet.
This is the make up of the adheasive the guy gave me. Including his spelling. I'm sure he mean't sodium Silicate.
Tap water
Cellafas
A60 Sodium Silicar - (small amount)
SF5 Kaolin - Ball clay
Zircon flower - (makes up the bulk)
I believe ITC-100 have some zircon but some one here on another post sugested 5-15%. where the above formulation is more than 50%. I hope it doesn't
act an as insulator on the element.
I have some gif pictures to up load but I don't know how to do it. I wish the instructions on this site were a little more comprehensive for people
like me who find computers allittle heavy. I've tried to upload via a link but I'm at an internet cafe and the staff don't know their own address and
they've hidden it from all the computers.angelhair - 11-6-2009 at 02:11
I'm going to forget about coating the wire, ussless I get some colloidal silica. Filling the groove is more difficult than I thought. I tried using a
air set cement but it shrinks. I then tried using my original castable mix but the grog is rather big so getting a smooth fill is very hard, but it
doesn't shrink.
I've never used an air set before, but I'm going to mix an equal or more portion of grog into it and try it that they. I hope the cement will still
set that way.
