Would it be possible to hydrogenate titanium dioxide to titanium metal with a platinum catalyst in ammonia, ethylamine or ethylenediamine?
Doesn't look possible to me. Look up the free energy of formation for TiO2 and H2O, for the presumed reaction TiO2 + 2 H2 --> Ti + 2 H2O. The free energy of reaction (which you will calculate yourself using handbook data) is positive and very large, which means that even using high pressure hydrogen (good luck) or high temperature will probably not help. (High temperature will not have a very large effect because you are trying to make 2 molecules of gas - H2O - out of the same number of H2 molecules; the change in entropy involved is therefore rather small.)
The free energy of reaction per Ti(0) atom will be even larger when the hydrogen comes as a part of a stable compound, because you'll need in addition to "invest" in decomposing the hydrogen compound.
And as for catalysts - remember that they can only change the rate of reaction but not the final equilibrium. If a reaction is not possible thermodynamically, a catalyst will not change this.
Hi Emanual,
If the reaction does not proceed with catalytic hydrogenation, could it proceed in an electrolytic cell?
Both titanium dioxide and aluminum oxide are soluable in ethylamine and both solutions conduct electricity.
At a sufficient voltage would the metal oxides be reduced to the metal?
Hi Christian Everett
In principle the way to get the pure metals is by electrolysis, of the oxides or chlorides or fluorides; however, I doubt these two refractory oxides really dissolve in ethylamine. I would be curious to see your reference(s) to this statement.
Thanks.
Emanuel Cooper
Hi Emanuel,
I contacted a manufacturer of ethylamine and they told me that titanium dioxide is soluable in ethylamine and that the solution conducts electricity.
I am attaching a screenshot of the email
Hi Christian Everett
I think I see where the misunderstanding comes from.
Ethylamine has a boiling point of 16 degC - practically a gas at room temperature. Not convenient to work with. Most of the time the suppliers will sell you a concentrated solution of ethylamine in water. Such solutions are quite basic - more basic than concentrated ammonia, for example - and most likely do dissolve amphoteric oxides and hydroxides of, e.g., Al, Cr, maybe Ti. Caveat: if the oxide is of mineral origin and/or if it underwent a high temperature treatment, you may need to wait for a very long time for it to dissolve. (Hydroxides are more cooperative.) The dissolved metal is in a form of oxoanion, such as aluminate, chromite, titanate (with mostly hydroxy groups as ligands).
But for the electrolysis of very electropositive metals such as these you can't use a medium that contains a lot of water. Best case, you'll get a mixture of metal and hydroxide. I think you need to look for something else.
Good luck,
Emanuel Cooper
Hi Emanual,
The manufacturer sells anhydrous ethylamine.
It would not be economical to ship aqueous ethylamine from China.
Isn't it an historical fact that ethylamine was used to separate aluminum oxide from iron oxide in the 19th century?
I am attaching a copy of a paper describing the electrolysis of aluminum salts in ammonia.
Would it be possible for someone to add titanium dioxide to ethylamine and measures the resistance?
Christian
Hi Christian,
I don't know much about the chemistry you are describing here. Yes it makes sense that you can dissolve some titanium and/or aluminum oxide in liquid ethylamine (probably not tens of grams per liter like your supplier states), and conductivity would be a good method to monitor the dissolution (although it won't tell you the concentrations unless you are prepared to engage in a laborious little research project to correlate conductance and concentration).
I think it does make sense NOT to ship anhydrous ethylamine IF what a client wants to use is an aqueous solution. Anhydrous ethylamine is very flammable and of course very volatile, so it's a significant shipping hazard. But if what you need is the anhydrous stuff, it can be done for the right price. Talk with your supplier some more.
If you do embark on this little adventure, please pay a lot of attention to safety, for your sake and for your lab mates'. Also, my hunch is that to get reproducible results you have to work in a tightly closed system under nitrogen or argon, so the amine doesn't absorb water (which will change a lot of parameters) and an errant spark doesn't cause an explosion.
Best of luck!
Emanuel Cooper