Sciencemadness Discussion Board - using catalyst from the catalytic converter

using catalyst from the catalytic converter

petrichor - 18-8-2017 at 04:52

can a catalytic converter be used as a catalyst for amateur chemistry?.
in many reactions and materials i am thinking about making require catalyst which its metal/compound might be available and cheap but require some metal working/plating abilities which i don't have. can i use catalytic converter for reactions like hydrogenation and the production of benzene from acetylene? from what i readed it can be catalysed by palladium.
in what i see in videos and pictures of dismantled catalytic converters the reduction and oxydation catalysts are seperated so it should be easier to choose appropriate catalyst for the reaction.

someone here tried it? there is something else i should do/know before i could use the catalyst in the catalytic converter?.

[Edited on 18-8-2017 by petrichor]

Melgar - 20-8-2017 at 00:10

You can use it to make aldehydes from alcohols. At least, formaldehyde from methanol and acetaldehyde from ethanol. You just need to control airflow and mixture ratio to optimize your output. You'll need a temperature monitoring / feedback system, like a thermocouple attached to an electric heating element if you want to use it to its full potential. You can also adjust things like the vapor/air mixture, the insulation on the catalyst, the vapor flow rate, etc. and figure out what works by trial and error.

Three-way catalytic converters (any made in at least the last twenty years) only perform all three conversions under very specific conditions, that are maintained by a vehicle's computer. So you don't need to assume that it will perform all three reactions under all conditions. However, because of the way the catalytic converter is designed, the main reactions that you'd be able to use it for are oxidations of organic substrates with air. If you were determined enough, you could probably even oxidize toluene to benzaldehyde and xylene into various phthalic acids.

petrichor - 20-8-2017 at 14:57

Quote: Originally posted by Melgar

You can use it to make aldehydes from alcohols. At least, formaldehyde from methanol and acetaldehyde from ethanol. You just need to control airflow and mixture ratio to optimize your output. You'll need a temperature monitoring / feedback system, like a thermocouple attached to an electric heating element if you want to use it to its full potential. You can also adjust things like the vapor/air mixture, the insulation on the catalyst, the vapor flow rate, etc. and figure out what works by trial and error.

Three-way catalytic converters (any made in at least the last twenty years) only perform all three conversions under very specific conditions, that are maintained by a vehicle's computer. So you don't need to assume that it will perform all three reactions under all conditions. However, because of the way the catalytic converter is designed, the main reactions that you'd be able to use it for are oxidations of organic substrates with air. If you were determined enough, you could probably even oxidize toluene to benzaldehyde and xylene into various phthalic acids.

and what about other reactions like the production of benzene from acetylene? or hydrogenation with hydrogen gas?, do i need to make some changes in the catalytic converter in order to use it for those reactions?.

Melgar - 20-8-2017 at 17:25

It's really designed for significantly exothermic gas-phase reactions, though. The ones you've described are typically liquid-phase and not exothermic enough to provide the necessary heat to maintain catalyst activity, so you're better off using a different form of catalyst.

violet sin - 20-8-2017 at 20:38

I picked up a caty the other day, garage sale $5, it was for a motorcycle of some sort and looked home made or possibly from a different model bike. Crappy welding may have been solely to change bolting flange.

Looks to be fun one of these days for something or other. What I will say, is that the thing is cemented to the sides of the steel housing with some kind of ceramic. Maybe 1/16"-1/8". I would imagine you will reduce a portion of the monolith to dust/bits while extracting it. I bet those pieces could be tried in a smaller tube of your choice, in a more controlled manner, or mixed into a liquid?

petrichor - 21-8-2017 at 09:51

Quote: Originally posted by Melgar

It's really designed for significantly exothermic gas-phase reactions, though. The ones you've described are typically liquid-phase and not exothermic enough to provide the necessary heat to maintain catalyst activity, so you're better off using a different form of catalyst.

you are talking about catalyst activation like with the activation of adam's catalyst? or about something else?. what preventing the platinum/palladium in the catalyst to act as a catalyst below the temperature range of catalytic converter?(which can be as low as 205 celsius from what i readed). from what i readed the reaction in the reduction part in the catalytic converter is the seperation of nitrogen oxides into nitrogen and oxygen, it is a different reaction so why it wouldn't require different conditions for reaction like hydrogenation?.
anyway if it wouldn't work under lower temperature there is something that can be done to change the catalytic converter(chemicaly of physicaly) and make it work under different conditions?.

i insist on catalytic converter cause i don't see an alternative, palladium and platinum catalysts aren't thing that can be bought by anyone and making catalysts out of palladium or platinum objects that can be bought by anyone seems very hard and require other stuff that aren't available for the common person and that is without speaking on the high costs.

there is a better alternative?

[Edited on 21-8-2017 by petrichor]

Melgar - 21-8-2017 at 14:09

You need entirely different physical properties for the catalyst support depending on whether it's for gas-phase or liquid-phase. PGMs will catalyze both oxidation and reduction depending on conditions, and the reaction is typically driven in a particular direction by changing those conditions.

Catalytic converters use the nitric oxides to oxidize unburned fuel, producing nitrogen gas and CO2. Lean mixtures result in more nitric oxides, while rich mixtures result in partially-oxidized hydrocarbons. Cars monitor the oxygen content of the exhaust to determine whether to make the mixture leaner or richer, so that the catalytic converter has roughly enough of both categories of pollutants to react them with each other and neutralize them. That's also why bad oxygen sensors tend to be a common reason for vehicles to fail inspections.

A gram of Pd/C costs $20 on eBay, and will have a lot more Pd than you'd be able to extract from a catalytic converter. Just trust me when I say extracting the metals is not as easy as you think it will be.

petrichor - 21-8-2017 at 17:16

Quote: Originally posted by Melgar

You need entirely different physical properties for the catalyst support depending on whether it's for gas-phase or liquid-phase. PGMs will catalyze both oxidation and reduction depending on conditions, and the reaction is typically driven in a particular direction by changing those conditions.

Catalytic converters use the nitric oxides to oxidize unburned fuel, producing nitrogen gas and CO2. Lean mixtures result in more nitric oxides, while rich mixtures result in partially-oxidized hydrocarbons. Cars monitor the oxygen content of the exhaust to determine whether to make the mixture leaner or richer, so that the catalytic converter has roughly enough of both categories of pollutants to react them with each other and neutralize them. That's also why bad oxygen sensors tend to be a common reason for vehicles to fail inspections.

A gram of Pd/C costs $20 on eBay, and will have a lot more Pd than you'd be able to extract from a catalytic converter. Just trust me when I say extracting the metals is not as easy as you think it will be.

ok, i think i understand the thing with the catalytic converter.
but what with buying catalyst on eBay? i can buy it as an ordinary person who have no formal relation to the chemistry industry or science? it can be a problem to import it to some countries?.

Melgar - 21-8-2017 at 20:03

Quote: Originally posted by petrichor

It's available for shipping from the US, but I don't know to what countries. Granted, it's not cheap, but palladium plating solution is commonly used by jewelers as a hypoallergenic undercoating for gold and rhodium plating. It'd be very easy to make Pd/C (palladium on carbon) from palladium plating solution and, say, activated charcoal from a water filter. I haven't actually done this though.

The most economical method is to just buy palladium metal as close to the spot price as possible, dissolve in aqua regia, and evaporate to give PdCl2. Then make Pd/C from that.

violet sin - 21-8-2017 at 20:37

Extracting Pd from monolithic ceramic capacitors can be simple if you have patients and the time to exercise those waiting skills. Or easy if you have better means. I used cold pack ammonium nitrate and hydrochloric acid to leach the SMD capacitors to a white powder and an orange solution. Light heating a couple times on a hot-plate and leaving it on the shelf was sufficient, 3+ months. Gassed it with chlorine and gathered a decent bit of bright/brick red PdCl₂. There was more in the way of process than just mix and sit. My notes are hours away.

This was practical to me b/c I work a lot, rarely see the lab. It is not practical for production. But it most definitely uses accessible reagents, minimal equipment, and may serve a basis for effective leaching of a catalytic converter. Or at least the Pd portion.

My intention was to try doping ceramic for a project similar to the propane burner like the Mr.Heater. bored really. Maybe plate something?