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guy
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Preparation of ethylene
I'm not sure if there is already a thread on this, but I was wondering if anyone has ever made ethylene from heating LDPE (what milk jugs are made out
of)? I found some instructions on the Microscale Gas Chemistry page, but I was wondering what the yield or purity of the produced gas is?
Thanks
[Edited on 11/9/2006 by guy]
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not_important
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I believe that the yield is fairly low, that PE does not depolymerise very cleanly. You get a lot of other alkenes when doing standard thermal
methods, too high of a temperature gives some alkanes and char (high carbon products). The saving grace is that only the C2 and C4 products are
gases, the C6 has a high vapour pressure as well. After that you have liquid or solid products, so on the small scale route the collection container
servers to help purify the gasses.
On the other hand, LDPE is cheap, so it may not matter that yields are low.
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guy
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I can probably purify it by absorbing most of the ethylene in a solution of [CuCl2]-.
Would this methold be easier? Passing ethanol through a hot tube containing Al2O3?
[Edited on 11/9/2006 by guy]
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Flo
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Ethylene can also be produced by heating ethanol with concentrated sulfuric or phosphoric acid to ~180°C . The yield is lower than that of the Al2O3
method because more sidereactions occur ( production of ether etc.)
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hinz
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Yes I tried it a few years ago, without success.
You might use a big pressurised vessel filled with Al2O3 and crack the polyethylene there. Afterwards you condense all higher boiling products in a
cold trap and you have your ethene. But this is not worth the effort.
I used a pipe filled with PE and heated it (in a chimney), let the vapors flow trough hot Al2O3, but got only a wax like solid and little gas.
Sometimes the wax like liquid (solid when cold) boiled in my catalyst tube and lot of gas was produced, but I recon it was not ethane but some longer
chain alkanes. The gases flow simply far too fast trough the catalyst.
Theoretically it should be possible, in slighly bigger scale, it might yield some highly desired products like benzene.
But in practise I would make my ethene by the "ethanol trough hot sillica or Al2O3 (clay)" method, it's far the simplest, all chemicals are readily
available and the yield is good. Only trap the unreacted ethanol and water in a cold trap or in conc. sulfuric.
The "ethanol with sulfuric acid at 180°C" method has the disadvantage not only to produce diethyl sulfate and ether, the sulfuric acid has also some
nice oxidising power on the ethanol at this temperature, once it has really started, it will runaway and a black jet of fine carbon particles
suspended in acid will shoot out of your reflux condensor (the same as with the sugar).
[Edited on 9-11-2006 by hinz]
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guy
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That is great to hear that the Al2O3/EtOH method works. I have a few questions though:
*How should the catalyst be prepared? I can make Al2O3 easily but do I have to put it on some substrate, or is it porous enough already?
*Also, what should the temperature be about? Can a portable stove do the trick?
*And lastly, how long should the tube be? A JCE article, using the same method to make propene (from isopropanol) uses a 20cm tube; would it be the
same for ethanol?
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hinz
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For the Al2O3 you could use everything, which is porous, like the solid phase in column chromatography, unfused clay used in pottery, aluminium
dissolved in water with the addition of a small amount mercury, hyrolysed aluminium isopropylate, silica gel although it's not Al2O3 etc. Only be
creative and of course don't use crushed pottery.
Temperature should be 350 to 400°C, so a bunsen burner or a stove does it, I used a stove in my first attemps too.
30-40 cm length is enough for the tube, longer is better, just plug the catalyst loosely in the tube and hold it at each end with some glass wool,
don't plug it too strong in it or there is no gas flow anymore. You might also try to fill it with porous stones (those from vulcanos, don't know how
they are called in english) and Al2O3 for better gas flow. Then you heat the tube carefully with your burner and boil some ethanol in a flask
connected with the inlet of the tube.
It might be good to take a borosilicate or ever quarz glass tube since soda glass will maybe bend or crack when the relativly cold ethanol vapors
enter it
[Edited on 9-11-2006 by hinz]
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Rosco Bodine
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| Quote: | Originally posted by guy
A JCE article, using the same method to make propene (from isopropanol) uses a 20cm tube |
If you have that article please attach it , or if
you have the details for the reference please post that ,
as propylene is of interest also .
Never mind I found it ....article attached .
[Edited on 9-11-2006 by Rosco Bodine]
Attachment: Propanol-Ene-Ane.pdf (180kB)
This file has been downloaded 983 times
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guy
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Would you consider kaowool (rockwool) a porous material?
So will this work for impregnating the Al2O3?
2Na[Al(OH)4](aq) -----heat(rockwool)-------> Al2O3 + 2NaOH + 3H2O -----wash---> Al2O3
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Rosco Bodine
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IIRC Kaowool is an aluminosilicate , and it could be that
the kaowool itself will be catalytic when you get it hot enough .
I have been doing a bit of reading of a section of a phenol patent where propylene is made from isopropanol as a
part of recycling of the byproducts from the phenol synthesis .
US5017729
From this patent and other references , it seems many different catalysts can be used . I would guess that
silica gel should also be effective as a catalyst .
Anyway here is a relevant paragraph from the patent
pasted below .
(e) Step of dehydrating the isopropanol of step (d) into propylene
In dehydrating the isopropanol of step (d) into propylene, a catalyst in the form of an acidic compound may be used. Examples of the catalyst used
herein include compounds generally known as acidic materials, for example, mineral acids such as sulfuric acid, phosphoric acid, hydrochloric acid,
and nitric acid, halo peroxides such as perchloric acid, perbromic acid, and periodic acid, heteropolyacids such as phosphomolybdic acid,
silicomolybdic acid, phosphotungstic acid, and silicotungstic acid. Other useful catalysts are solid acidic materials, for example, ordinary solid
acids such as silica, silica-alumina, alumina and .gamma.-alumina and metal oxides such as titanium oxide, zinc oxide, and zirconium oxide. Various
zeolites which now draw attention as shape selective catalysts and zeolites modified with metal ions may also be used as the catalyst. Among these
catalysts, most preferred are .gamma.-alumina and titanium oxide.
Dehydration of isopropanol may be carried out in either gas or liquid phase. The reaction temperature preferably ranges from about 100.degree. C. to
450.degree. C., more preferably from about 200.degree. C. to 350.degree. C, most preferably from 260.degree. C. to 350.degree. C. The reaction
pressure may be reduced, atmospheric, or increased pressure. In the case of liquid phase reaction, the reaction system should be pressurized to
maintain the system in liquid phase.
Dehydration is preferred to be carried out under increased pressure, especially within a range under which propylene as the reaction product is
obtained in the form of liquid. For example, liquid propylene can be recovered by carrying out the dehydration reaction at an increased pressure of 18
kg/cm.sup.2 and then cooling the reaction mixture at 40.degree. C. or less. Because recovery of liquid propylene renders possible recycle of the
recovered propylene as starting material of step (a) by directly drying the liquid propylene and recycling the dried propylene to step (a) through
step (f). These facilities for the process can be simplified by leaving out booster pump etc. which are essential for the liquefaction of gaseous
propylene in the case of gas phase reaction.
In addition, distillation and purification of liquid propylene can be carried out easily as occasion demands.
In the practice of the invention, the isopropanol dehydration step may be either batchwise or continuous. When a solid catalyst is used, reaction may
adopt a fluidized bed using powder catalyst or a fixed bed using granular catalyst depending on the shape of a particular catalyst used. Fixed bed
reaction is preferred in view of ease of separation of the catalyst from the reaction mixture and simplicity of the reaction system.
In this way, propylene can be recovered from the acetone by-product produced upon preparation of phenol. The thus recovered propylene has a purity of
at least about 99.5% and is ready for use as the reactant in step (a) and also useful as the reactant for the synthesis of polypropylene,
acrylonitrile, propylene oxide, ethylene-propylene rubber and the like.
[Edited on 10-11-2006 by Rosco Bodine]
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solo
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Reference Information
Synthesis of ethylene and ethane by partial oxidation of methane over lithium-doped magnesium oxide
Tomoyasu Ito and Jack H. Lunsford
Nature vol.314, pp721,1985
[Edited on 10-11-2006 by solo]
Attachment: Synthesis of ethylene and ethane by partial oxidation of methane over lithium-doped magnesium oxide.pdf (215kB)
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Rosco Bodine
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It appears that using an alumina catalyst for dehydration of isopropanol , that the porosity and the chemical composition of the catalyst is very
important .
US5227563
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solo
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Reference Information
PREPARATION OF KETENE FROM GLACIAL ACETIC ACID. METHYL ACETATE, AND ETHYL ACETATE
K. K. GEORGIEFF
Canadian Journal of Chemistry 30 332-47 (1952)
Abstract
Laboratory studies were carried out to determine whether methyl and ethyl acetates could be pyrolyzed to give yields and conversions to ketene
comparable to those obtainable from acetic acid. Acetic acid was pyrolyzed to ketene and water in the presence of 0.33% triethyl phosphate or
phosphoric acid catalyst at 680°-760°C. and 140-160 mm. Hg absolute. Maximum yield obtained was 80.6% and maximum conversion 34.5%. Methyl acetate
was cracked to ketene and methanol at 610°-685°C. and 95-400 mm. absolute, using triethyl phosphate,
phosphoric acid, sulphuric acid, dimethyl sulphate, butyl borate, and silica gel boric acid as catalysts. High yields could be obtained only with
phosphates in 2-3% concentration. Maximum yield to ketene, including ketene recovered as acetic acid, was 76% (conversion 31-34%). Maximum yield to
methanol was 81.3% (conversion 33-34%). Methyl acetate containing 18% methanol was also cracked but results were poorer. Ethyl acetate, in the
presence of 0.33% triethyl phosphate, was pyrolyzed to ketene, ethylene, and water at 630°-685°C.
and 140-190 mm. absolute. Maximum yield of ketene, including ketene recovered as acetic acid, was 85.8%. Maximum conversion to ketene was 35.4% and to
ketene plus acetic acid 85.7%. Yields to ethylene were nearly quantitative.
Excerp
The yield of ethylene was determined for only Run No. E7 and was found to be 104% of theory, assuming that all the ethylene was derived from the ethyl
radical. However, it is known that ketene also decomposes to ethylene, carbon monoxide, and other gases, and if it is assumed. that all the acetate
radical which is not recovered as ketene or acetic acid is converted quantitatively to ethylene, carbon monoxide, and water.
Note: Article was posted by Lugh over at WD
Attachment: georgieff.djvu (123kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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roamingnome
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hinz seems to say this works, but i was wonderinng if guys test confirms such??
----------------------------------------------
well needless to say there is some patent info...
http://www.scielo.br/scielo.php?pid=S1516-14392006000200013&...
Therefore, the Lewis acid sites of impregnated samples were stronger than those of pure aluminas. This can be explained by the higher electronegative
feature of phosphorous-alumina bonding and also by the decrease in the aluminum's electronic density, resulting in an increase of the acidity of the
Lewis sites.
alumina alone is a no go, but phosphates increase the goodness...
[Edited on 24-4-2007 by roamingnome]
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roamingnome
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another worthy classic
http://pubs.acs.org/cgi-bin/abstract.cgi/jpchax/1930/34/i12/...
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smuv
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I too am interested in the production of ethylene. I have found an interesting book "Ethylene and Industrial Derivatives" by S. A. Miller.
Here are some excerpts, the first is an overview of all the processes of producing ethylene (both lab and industrial). The most interesting of which
I think is the decomposition of ethyl borate.
The second attachment deals with, industrial vapor phase production from ethanol (mind you this is a dated book).
Attachment: ethylene_industrial_and_lab_production.pdf (332kB)
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smuv
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p.s How can I add multiple attachments to one post?
Attachment: vapor_phase_ethanol_dehydration.pdf (151kB)
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jimmyboy
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ethylene and a bunsen burner --- how much fun!! hahah
please use nichrome -- no open flames.. ether is a byproduct of this reaction.. (kaboom!!)
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Rosco Bodine
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Indeed another worthy classic , and now this link gets the whole 8 pages instead of that first page tease above 
Also this article is good enough to save as an attachment here for further safekeeping .
[Edited on 3-5-2007 by Rosco Bodine]
Attachment: Ethylene from ethanol and phosphoric acid.pdf (442kB)
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smuv
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| Quote: | Originally posted by jimmyboy
please use nichrome -- no open flames.. ether is a byproduct of this reaction.. (kaboom!!) |
Why are you worried about the ether, when ethylene is the MAIN product. Ethylene like ether has very wide explosive limits.
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Rosco Bodine
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That article about the use of phosphoric acid and ethanol
as a source for ethylene , makes me think that some similar routes to ethylene may also occur via ethyl sulfuric acid as an intermediate obtained by
reaction of ethanol
with a bisulfate or a pyrosulfate , reaction carried out at
a high enough temperature . This would be similar to the
reaction which produces ether from ethanol and sulfuric acid , via ethylsulfuric acid as an intermediate , which
occurs at lower temperatures , while at higher temperatures ethylene is the product .
A couple of other threads which are pertinent to what I am thinking about this possiblity are
http://www.sciencemadness.org/talk/viewthread.php?tid=1113&a...
http://www.sciencemadness.org/talk/viewthread.php?tid=4689&a...
It also seems possible that a reagent might be made
which is a mixture of some of these paths , working
in parallel for cracking ethanol to ethylene.
Update: One of the references to the boric acid method was found on Gallica , but referenced back to an earlier journal
which is before the earliest year of scanned journals online .
The original journal article decribing the particulars was
by Ebelman , J. prakt. Chem., 1846, 37 , 347 . I have withdrawn my request as it appears someone would have
to visit a library and get the hard copy , scan and translate .
[Edited on 4-5-2007 by Rosco Bodine]
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Zinc
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| Quote: | Originally posted by guy
I can probably purify it by absorbing most of the ethylene in a solution of [CuCl2]-.
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A solutio of CuCl2 absorbs ethylene? How can it be recovered from the solution?
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guy
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| Quote: | Originally posted by Zinc
| Quote: | Originally posted by guy
I can probably purify it by absorbing most of the ethylene in a solution of [CuCl2]-.
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A solutio of CuCl2 absorbs ethylene? How can it be recovered from the solution? |
[Cu(I)Cl2]-
I guess you can regenerate it by heating.
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DDoS
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Once I synthesized ethene from EtOH (washed in water and NaOH) and the resualt was a nasty head ache.
Just blew ethene from the rubber pipe towards small flame in the video.
Attachment: ethene.avi (1.7MB)
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roamingnome
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Drying Ethylene ( final considerations)
| Quote: |
Once I synthesized ethene from EtOH (washed in water and NaOH) and the resualt was a nasty head ache.
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do you mean this in the process was a headache or the inhaled gas gave you a headache.... hmmm mabye i shouldnt ask...
about to commence with a live fire excercise which i WILL report on. conflicting refs say water will foil the proposed reaction so to be safe i
simply want to scrub the water out, but not polymerize the ethylene or damage it etc...
i have CaCl2, CaSO4, and silica gel available.
none of these should react with ethylene right?
the scrubbing tube will be room temperature but the apparatus will be 300 degrees
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