February 28, 2020, 09:05:06 PM
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Organic Chemistry Forum / Re: Pyrolysis of wood
« Last post by gatewood on Today at 12:32:58 PM »
I heard that you could extract useful hydrocarbons, such as benzene, xylene and toluene from the destructive distillation of wood and charcoal.

These three compounds are useful but very cheap. Extracted train-wise from petrol, with very little transformation. I can't imagine wood pyrolysis on reasonable scale competing against that. Same for methanol and more compounds.

More generally, petrol and coal too are pyrolysis products of wood and similar substances. You find similar compounds in all of them. They are the compounds that form indistinctly from very rough and uncontrolled reactions. You get aromatics because of the H/C ratio and the stability of aromatic rings. Lighter alcohols, aldehydes and ketones at the beginning, polycyclic aromatics at the end.

In this context, I doubt that a major product of wood pyrolysis has a market value not spoiled by coal and petrol products. What you might try:

Find a minor compound that is not usually extracted from coal nor petrol. Since petrol is already well pyrolysed and coal even more, you might have better chances with the early pyrolysis products. Just a gut feeling. If you obtain for instance a solvent with pleasant odour, different from turpentine, it has more value than white spirit.

Or do more than a bare pyrolysis. Add some cheap compound (natural gas, alcohol, aldehyde, amine...) and check is something more useful comes out. Again, early products should be more differentiated than late ones.

Pyrolysis makes many moderate carcinogens, so you'll have to sort out the products.

" Lighter alcohols, aldehydes and ketones at the beginning"

You know why is that exactly?

Thanks for the input, thats some pretty useful insight right there :)
22
Inorganic Chemistry Forum / Re: Solubility of Calcium hydroxide in water
« Last post by Prof on Today at 12:24:13 PM »
thank you!
23
Organic Chemistry Forum / Re: Grignard Error?
« Last post by clarkstill on Today at 08:50:11 AM »
Wow - I must have written my answer before my morning coffee! mjc is of course correct
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Hi,
i'm writing a thesis involving 3D printing and i'm trying to print different materials. I am curious about how to formulate polymers suitable for 3D printing - both filament and particle-loaded paste extrusion.

Some of the most interesting applications of 3D printing involve trying to stuff as much solid particles (metals, ceramics, etc.) as possible in the print material, but this leads to the obvious problem that the viscosity increases exponentially with the solids loading. Also using shorter-chain polymers decrease melt viscosity but is deleterious to the mechanical properties of the printed object. I'm curious as to what guidelines to follow when formulating a polymer mix for printing, for example i want to make a filament that is (1) flexible so it can be rolled onto a spool, (2) mechanically sturdy enough to print and (3) contains as much solid particles as possible.

In a first attempt i tried a polyvinyl acetate with a suitable melting point ~80 C with a 50% solids loading, but the melt viscosity was too high. I then added 10% dioctylsebecate plasticiser, this resulted in a filament too soft for printing, it just crumbled when being pressed into the extruder.

Aside from the formulation of the polymer binder i'm considering other strategies to try to force the paste out of a small nozzle. May it be worthwhile to coat the inside of the extruder head in PTFE to minimise friction/facilitate wall slip? Could a similiar effect be achieved by adding a surfactant to the print mixture? Could the viscosity of the paste be lowered by a surfactant (since the paste is made up mainly of particles, particle-particle interactions should be very important)? Can the mixture be formulated as to maximise shear-thinning (and avoid shear-thickening)?

Another interesting and by me unanticipated problem arised when i tried to extrude a paste of UV-curable elastomer liquid resin with 50% particles - even though i de-gassed the stuff in a vacuum it didn't stop oozing out of the syringe when i stopped the extruder screw. Is this related to relaxation of the fluid, or is it actually significantly compressible? I've found litterature about the free volume of polymers but it is a complicated subject and there seems to be very little information regarding compressibility.

Just throwing my thoughts out here to see if i get any response, i'll be happy to elaborate if anyone shows an interest!
25
Quote
But the problem arises on what volume should be used to establish an equation from where to find the composition of the mixture.
You don't need to know this. You simply need to assume that the effused volumes of nitrogen and mixture are the same. (The question doesn't say this, but you can't solve it otherwise.) Then the effusion times give you the relative rates of effusion, from which you can work out an effective molecular weight for the mixture, and hence the composition.

But I wonder if there is an error in the question. They seem to assume (at least, this assumption leads to one of the optional answers) that the effective MW is the arithmetic mean, given by
M = x*32 + (1-x)*44, where x is the mole fraction of oxygen.
However, this does not seem to me to be right. From the additivity of the effusion rates of O2 and CO2, I would expect the effective MW to be given by
1/sqrt(M) = x/sqrt(32) + (1-x)/sqrt(44)
This gives a different value for x, which does not correspond to any of the answers. (The composition by the first assumption is very close, but not identical, to the composition I calculate for the effused mixture.)
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High School Chemistry Forum / Re: IF3 lewis properties
« Last post by OuJej1 on Today at 06:33:35 AM »
What's the hybridization of I?
What does its electron configuartion look like?
Try drawing the molecule in Lewis Dot structure.
27
What if I tell you "a certain volume" means exactly 1 mL? Would it help?
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High School Chemistry Forum / Re: Diluting vinegar
« Last post by rêves-tu? on Yesterday at 11:44:24 PM »
You would use a pipette (used for transferring substance) rather than a buret (used to measure quantity of substance)
You rinse the pipette to make sure any residual substance is vinegar and not water so that the transferred vinegar isn't diluted.
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High School Chemistry Forum / IF3 lewis properties
« Last post by rêves-tu? on Yesterday at 09:49:42 PM »
My first thought when looking at the structure of IF3 was that it was a lewis base because it has two lone pairs. However, it turns out that it's an acid. Why is this the case?
30
What is sum of partial volumes of oxygen of carbon dioxide?

It is not given, the problem only states "a certain volume of nitrogen gas", therefore with that given clue and the time for this gas and the mixture of that of the others referring to oxygen and carbox dioxide, is it possible to relate it with the composition of such mixture?. Can this problem be solved?.  ???
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