Large-Scale Methamphetamine Manufacture

2.6 Oxidation of Ammonium Chloroplatinate to Platinum Dioxide

This is where the rubber meets the road in this procedure. We must mix our ammonium chloroplatinate with sodium nitrate, our oxidizer, and burn it. In the old days, when Adams invented this catalyst, they used a copper-alloy block with a crucible and a hole drilled for the insertion of a thermometer to measure the temperature. Our procedure isn't much better, but if Adams could do it with crude equipment, perhaps we can optimistically expect to do as well. At this point, your humble writer must point out that he has never made a batch of catalyst that did not work, even though experiments were performed over the temperature range of 480-530°C. This is not due to some extraordinary intelligence or experience. It is because this is easy to do. The accompanying poor quality picture shows new brown catalyst on the left and spent black catalyst on the right.
The ammonium chloroplatinate must come into "intimate contact" with the oxidizer, according to Adams. To accomplish this, place 50g of sodium nitrate in a layer at the bottom of your mortar-and-pestle set. Add 5g of ammonium chloroplatinate chunks to the bed and grind until all chunks are thoroughly blended into a homogenous yellow powder. Be thorough here, as it will pay off in catalyst yield. Shake the mixture into the 8"x8" Corningware casserole dish. Do this five times for a total of 25g of ammonium chloroplatinate and 250g of sodium nitrate. Do not attempt to do more than this-it makes a terrible mess inside the oven. A safer amount is 20g, but 25g batches will work reliably if the oven is controlled properly.
Spread the yellow powder evenly across the bottom of the casserole dish, replace the Pyrex cover, and place the dish into the jeweler's oven. The idea here is to place the dish so the temperature on the front meter accurately reflects the temperature inside the vessel. If one has a large oven with the temperature sensor in the center, adjust the position of the dish with varying thicknesses of firebrick. If the heating element runs directly beneath the dish, spot heating should be avoided by placing a thin firebrick across the bottom. We are operating close to the temperature limits of the vessel material, so a little diligence is required. The oven should be placed inside the fume cabinet where the noxious fumes produced can be exhausted, preferably into a stiff wind at night. Secure the latch on the oven. On my oven, the temperature control is graduated from 1 to 10. I set the control on 3.75, having learned the hard way that too-rapid heating will shatter the casserole dish. The temperature will slowly climb over a period of 2.5-3.0 hours to 520°C, at which point the heating element is turned off and the chemist leaves the oven to cool down overnight. He does not open the door of the oven, even a crack, until the temperature is all the way down. Failure to exercise patience will be swiftly punished with a shattered dish and a nasty mess. One should watch the oven carefully, noting that the heating element cycles on and off and correlating that with changes on the temperature indicator. This will improve one's precision in controlling the oven temperature in the event one should desire to experiment, which this writer encourages. A plume of brown fumes should begin to rise from the exhaust hole at the top as the oxidation begins. This usually occurs starting at 380-400°C and can continue all the way up to about 500°C, but not always, and not predictably. This writer has discovered empirically that the temperature range over which catalyst can be successfully produced is 490-520°C, with the best catalyst being made at 510°C. As the meters used on these ovens are the inexpensive current-shunt type, they are accurate to about ±2%, which is about 10°C either way, so there can be as much as 20°C variance in the temperature indicator from unit to unit. In addition, the temperature sensors used have tolerances that can stack up in the wrong direction. The point here is that your oven may read differently than mine, so one should be observant and adjust the setting based upon the results of the previous oxidation. If the stuff turned out burnt, lower the temperature.
Open the door-latch of the cold oven and remove the casserole dish. Pry the top off gently with a screwdriver, as it will be fused with white sodium nitrate residue. Inside will be a layer of hardened sodium nitrate mixed with and covering a layer of brown-black powder which will have spattered and coated the inside surface. Pour some distilled water into the top and gently work it with a plastic spoon to dissolve the sodium nitrate and free up the platinum dioxide particles. Carefully pour the resulting liquid into the clean 5000ml beaker. Repeat to recover the last traces of catalyst stuck to the cover. Pour distilled water into the casserole dish until the bottom layer is covered and break up the hard layer as gently as possible with a clean screwdriver. Work the chunks until they are broken up into pieces small enough to handle. Using surgical gloves, very carefully place the larger pieces into the 5000ml beaker, rinsing one's fingers with distilled water into the beaker. Once the large pieces have been removed, add water and work the dish until one is satisfied as much catalyst as possible has been recovered. Add distilled water to the large beaker until it is almost full and stir until all of the sodium nitrate has dissolved and one is left with a dark brown suspension that gradually settles to the bottom of the beaker. Let it settle overnight then carefully decant the water without disturbing the catalyst layer at the bottom. Decant as much water as possible without losing catalyst, then refill with more distilled water, stir thoroughly for 15 minutes, then let it settle overnight once again. Do this four times to insure all the nitrate is dissolved and removed. Successive washings will result in the catalyst taking longer and longer to settle out, until, on the fourth one, the catalyst may become colloidal and not settle out completely. Using the Whatman Qualitative 5 filter paper and a clean Buchner, filter the catalyst suspension, washing the beaker with distilled water to catch the last grains. One should now have a layer of wet, medium-to-dark brown catalyst in the Buchner. Gently work the small cake loose onto a small glass or porcelain plate and spread it out using a fine-tipped razor-knife. Let it dry in a warm, but not hot, place. Once dry, carefully scrape the loose powder into a clean spice bottle, which makes an ideal container. Do not let it fall freely through the air more than a few inches as this can, and will, result in a display of pyrotechnics as your catalyst explodes while you watch. This is especially true when the temperature drops below freezing or one is in a very dry area. One should now have about 11g of platinum dioxide (PtO2, 227.09g/mole, 0.048mole) for a yield of about 85%.
Repeat the above three steps until all the ammonium chloroplatinate is used. One should have 50-60g of catalyst in the form of a very finely divided dry brown powder. Store in a cool, dry place and avoid static discharges. There is some debate about whether or not this catalyst decreases in activity level over periods of time exceeding 6-12 months. It has been this writer's experience that the catalyst itself maintains it's activity level as long as it has not been pre- reduced or otherwise exposed to concentrated hydrogen. There are many other factors that can easily cause a decrease in yield or an increase in reduction time that can be misinterpreted as a change in catalyst activity. This catalyst is very sensitive to the level of self-oxidation or residual acids in the P2P. In addition, slight variations in agitation effectiveness can appear to be catalyst-related.

3.0 The Hatch-Feinstein Reduction

Application of Platinum Dioxide Catalyst to the Reductive Amination of 1-phenyl-2-propanone (P2P). In this section the chemist pre-reduces the catalyst and reductively aminates both test and production quantities of P2P.