# Adam's catalyst / PtO2 batch sizes & ratios



## sony (Nov 26, 2012)

Given that one's oven can handle the volume is there any serious problem encountered when upscaling the fusion of sodium nitrate with ammonium hexachloroplatinate to produce the adam's catalyst?

According to Organic Syntheses, Coll. Vol. 1, p.463 (1941); Vol. 8, p.92 (1928). it is stated:


> If a considerable quantity of platinum oxide is desired it is more satisfactory to prepare several runs of the size indicated than one large run, since spattering and the evolution of gases make large amounts inconvenient to handle



However this is in regard to the fusion of chloroplatinic acid with sodium nitrate and chloroplatinic acid is of course much more hygroscopic then ammonium hexachloroplatinate so there will of course still be gas evolution but i have not noticed more then a little bit of spattering with a 50 gr ammonium hexachloroplatinate / 500 sodium nitrate run.

Does anyone know if there will be loss of yield / reduced activity of the catalyst from the result of a 100 or even 200 gr ammonium hexachloroplatinate batch? 

Also i was wondering what an appropriate ammount of sodium nitrate would be, up to now with the smaller batches i have used a 10 times excess by weight but 1kg sodium nitrate per 100 gr ammonium hexchloroplatinate seems a bit excessive.


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## rusty (Nov 26, 2012)

sony said:


> Given that one's oven can handle the volume is there any serious problem encountered when upscaling the fusion of sodium nitrate with ammonium hexachloroplatinate to produce the adam's catalyst?
> 
> According to Organic Syntheses, Coll. Vol. 1, p.463 (1941); Vol. 8, p.92 (1928). it is stated:
> 
> ...



edit to delete unqualified answer.


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## Lou (Nov 26, 2012)

FYI, the fusion makes much more splatter with ammonium hexachloroplatinate unless chunks are added.


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## sony (Nov 27, 2012)

Having only experience with ammonium hexachloroplatinate i was not aware that the fusion makes more spatter then when using chloroplatinic acid thanks for the info.

I'm not sure what you mean by adding chunks, does this mean that the ammonium hexachloroplatinate should be in chunk form ?

Will post back as soon as there is a little experimentation done with ratios and scale.


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## sony (Dec 5, 2012)

There was 94,31 grams ammonium hexachloroplatinate carefully grinded up with 750 grams of sodium nitrate, the whole was grinded up with a mortal and pestle to provide a good mixture and this was placed in a porcelain enamle coated iron container in an oven that was 400 deg celcius the temperature was kept for 10 minutes and then raised to 520 degree celcius, after 10 minutes the temperature og 520 celcius was reached and kept for another 30 minutes and from there allowed to cool down,

The solid plate was of salts was crushed up and dissolved in 3 liter dH20 that was brough to a boil beforre adding, the mass was filtered to provide 46,12 grams of PtO2


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## Lou (Dec 6, 2012)

For production, it is easier to gear up and pour the fusion into a large HDPE tank of cold distilledwater. The tank should be agitated and such that spatter-out can't happen. An inverted large stainless funnel works very well for that.

The catalyst rapidly settles and the bulk of the solution can be siphoned off and reused.


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## 9kuuby9 (Dec 25, 2013)

Any further tips that might improve the process, when dealing whit a larger scale (1kg) ?

Or should it be split up for the convince? But it will take more time however.

Is an oven preferred over a hotplate for completing this task?

Is it possible to dry the catalyst on a hotplate above 100°C?, From PtO2*H2O to PtO2? I noticed when washing the catalyst it becomes hydrated.

Dissolution of Platinum is also a pain.

Thanks in advance!


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## 9kuuby9 (Dec 25, 2013)

sony said:


> There was 94,31 grams ammonium hexachloroplatinate carefully grounded up with 750 grams of sodium nitrate, the whole was grounded up with a mortal and pestle to provide a good mixture and this was placed in a porcelain enamel coated iron container in an oven that was 400 degree Celsius the temperature was kept for 10 minutes and then raised to 520 degree Celsius, after 10 minutes the temperature of 520 Celsius was reached and kept for another 30 minutes and from there allowed to cool down,
> 
> The solid plate was of salts was crushed up and dissolved in 3 liter D.H2O that was brought to a boil before adding, the mass was filtered to provide 46,12 grams of PtO2




The filtered mass was hydrated PtO2 or PtO2*H2O, which has a molar weight of 244,090g/mol While PtO2 has a molar weight of 227,0768g/mol.
when the hydrate is expelled you should have 42,91g left of pure PtO2

You should have also kept the ratio of 1:10, 94,31g ammonium hexachloroplatinate should have been combined with 943,1g of KNO3 or NaNO3.

From 94,31g ammonium hexachloroplatinate you should have gotten around 48,247g anhydrous PtO2 or 51,86g hydrated PtO2.

The loss was either due to improper handling, spattering or incomplete fusion due to the lack of KNO3 or NaNO3.

If by incomplete fusion then the remnants of the ammonium hexachloroplatinate was dissolved by the boiling water you mentioned in your last step.

Always test your solutions for values before handling or disposing of.

You can also apparently either use KNO3 or NaNO3 in the fusion process.


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## 9kuuby9 (Dec 25, 2013)

Here is some literature regarding the possible ways of producing Adam's catalyst.

Platinum Dioxide(Adam's Catalyst)

Platinum dioxide (PtO2) for use in hydrogenations is available commercially. It may 
alternatively be prepared by either of the following methods.
Method 1 (from ammonium chloroplatinate) [2]
Place 3.0 g of ammonium chloroplatinate and 30g of sodium nitrate (AnalaR) (Note 4) in 
a Pyrex beaker or porcelain dish and heat gently at first until the evolution of gas slackens 
and then more strongly until a temperature of 300 °C is reached. This occupies about 15 
minutes, and there is no spattering. Maintain the fluid mass at 500 -530 °C for 30 
minutes, and allow the mixture to cool. Treat the solid mass with 50 ml of water. The 
brown precipitate of platinum oxide (PtO2.H2O) settles to the bottom. Wash it once or 
twice by decantation, filter through a hardened filter paper and wash on the filter until 
practically free from nitrates. Stop the washing process immediately when the precipitate 
tends to become colloidal (Note 5): traces of sodium nitrate do not affect the efficiency of 
the catalist. Dry the oxide in a dessicator, weigh out portions of the dried material a 
required.

Method 2 (from chloroplatinic acid) [2]

Dissolve 3.5 g of the purest commercial chloroplatinic acid in 10 ml of water contained in 
a 250-ml Pyrex beaker or porcelain basin, and add 35 g of sodium nitrate (AnalaR) (Note 
4). Evaporate the mixture to dryness by heating gently over a Bunsen flame while stirring 
with a glas rod. Then raise the temperature to 350-370°C within about 10 minutes: fusion 
will occur accompanied by the evolution of brown oxides of nitrogen and the gradual 
separation of a precipitate of brown platinum oxide. If foaming occurs, stir the mixture 
more vigorously and direct an additional flame at the top of the reaction mixture, if 
necessary. If the burned beneath the beaker is removed when frothing commences, the 
top of the fused mass solidifies and material may be carried over the sides of the vessel. 
After 15 minutes, when the temperature has reached 400°C, the evolution of gas 
decreases considerably. Continue the heating until at the end of 20 minutes the 
temperature is 500-550°C; at this stage the evolution of oxides of nitrogen has practically 
ceased and there is gentle evolution of gas. Maintain the temperature at this point (best 
with the full force of a Bunsen burner) for about 30 minutes, by which time fusion is 
complete. Allow the mass to cool (the Pyrex beaker may crack), add 50 ml of water and 
proceed as in Method 1.

Method 3 [6]

In a fume cupboard, dissolve chloroplatinic acid (H2PtCl6.6H2O, 0.10 g) in water (ca. 
0.5 ml) in a porcelain crucible (3-4 cm diameter). Add sodium nitrate (1 g) and evaporate 
the mixture to dryness, over a low flame, with continuous stirring. Turn the Bunsen 
burner full on and stir the contents of the crucible vigorously until the mass has melted 
completely and the initial decomposition has subsided. Keep the bottom of the crucible at 
a dull redheat for a further 30 min. (too strong a heat decomposes the oxide to the metal). 
Allow the crucible to cool and wash the contents into a 250 ml beaker with hot water 
from a wash bottle. Filter off the brown platinum oxide with a small ('Hirsch') funnel 
(Whatman paper No. 541) and wash the oxide with hot water (about 200 ml) until the 
washings are free from nitrate ion. Dry the catalyst over calcium chloride in a vacuum 
desiccator.

Preparation of Platinum Oxide from Chloroplatinic Acid [9]

Platinum Oxide for catalytic hydrogenations can be prepared more conveniently from 
ammonium chloroplatinate than from chloroplatinic acid by the well-known procedure of 
Adams (1). By adding an excess of ammonia to a solution of chloroplatinic acid, 
ammonium chloroplatinate is precipitated. This is the basis for a convenient method of 
recovering platinum in spent catatlysts (2). The amount of catalyst produced from a given 
weight of ammonium chloroplatinate is almost exactly ½ the weight of the ammonium 
salt and is therefore very easily calculated. Ammonium chloroplatinate is not hygroscopic 
and is therefore weighted more easily than chloroplatinic acid. In starting from the 
ammonium salt, no water is used, and hence no spattering occurs in heating the mixture 
to the fusion temperature.
By the new procedure a given weight of ammonium chloroplatinate is well mixed with 
ten times its weight of powdered sodium nitrate, and the mixture is heated gradually to 
the fusion point. During this process much gas is evolved, due presumably to the 
decomposition of ammonium nitrate, but the evolution is gentle and no spattering occurs. 
The fused mixture is held at 500*C for 25-30 minutes and the platinum oxide is isolated 
according to Adam’s directions. From 3.0g of the salt was obtained 1.51g of platinum 
oxide, no different in general appearance or activity from that prepared in the usual way. 
This experiment has been duplicated in several other laboratories and shortens the 
procedure for converting spent catalyst to platinum oxide by 25% or more.

Platinum Recovery [2]

Platinum residues from hydrogenation reactions should be carefully preserved and 
subsequently recovered by conversion into ammonium chloroplatinate by the following 
method. Dissolve the platinum or platinum residues in aqua regia, evaporate just to 
dryness several times with concentrated hydrochloric acid, dissolve the final residue in a 
little water and filter. Precipitate ammonium chloroplatinate from the filtrate by addition 
of excess of a saturated solution of ammonium chloride. Filter and dry the precipitate at 
100°C.

Notes:
Sodium acetate trihydrate can be made from equimolar amounts of acetic acid and an 
aqueous solution of sodium hydroxide, followed by concentrating the solution and 
filtering off the precipitated NaOAc*3H2O as large clear crystals, which are air 
dried. The sodium acetate trihydrate loses its water and becomes powdery 
anhydrous NaOAc upon heating over 100°C, so do not heat it too much while 
drying it. 

Any of the commercial forms of activated charcoal/carbon ("Norit", "Darco", "Big K 
Brand", GNC etc.) may be employed; the carbon should be heated on a steam 
bath with 10% nitric acid for 2-3 hours, washed free of acid with water and dried 
at 100-110°C before use. If the acid washed form of "Norit" charcoal is available, 
it may be used directly without further purification. 

The filtrates should be clear and colorless; if they show a yellow-orange opalescence, 
some of the oxide has become colloidal. The palladium may be recovered [7,8]as 
the oxide by evaporating the filtrates to dryness and re-fusing, or as palladium 
black by rendering the filtrates slightly alkaline with sodium carbonate and 
heating with formaldehyde. 

The use of an equivalent quantity of potassium nitrate (AnalaR) is said to produce a 
more active catalyst. 

It is advisable to test a small portion of the filtrate from platinum by acidifying with 
hydrochloric acid and adding a few drops of SnCl2 solution: a yellow or brown 
colour develops according to the quantity of platinum present. The yellow colour 
is soluble in ether, thus rendering the test more sensitive. If platinum is found, 
treat the filtrate with excess of formaldehyde and NaOH solution and heat; 
platinum black separates on standing and may be filtered and worked up with 
other platinum residues. 


References
[1]R. Mozingo, Organic Synthesis Collective Volume 3, 685 (1955) 
[2] Vogel's Textbook of Practical Organic Chemistry, 5th ed, p 452-460 (1989) 
[3]H. Wieland, Chem. Ber., 45, 484 (1912) 
[4]D. Starr, Organic Synthesis Collective Volume 2, p 566 
[5]A. Lindlar, Helv. Chim. Acta., 35, 446 (1952) 
[6]R. Adams, Organic Synthesis Collective Volume 1, 463 (1941) 
[7]R. Adams, J. Am. Chem. Soc. 46, 1684 (1924) 
[8]R. Adams, J. Am. Chem. Soc. 47, 1147 (1925) 
[9]W. F. Bruce, J. Am. Chem. Soc. 58, 687-688 (1936)


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