Hello all,
I am using pure organic compound with good thermal stability and it is practically insoluble in most of the solvents as catalyst for C-C bond formation. I want to determine its nature in catalysis.
1. I am performing reaction in neat cionditions (without solvent) at 100 C temperature, at this I think some of the catalyst is soluble but I can see most of the catalyst solid present in the mixture.
2. som example reactions due occur at room temp where catalyst is completely insoluble
3. without catalyst reaction won't go, increasing catalyst amount has positive effect. but overloading of catalyst reduced yield.
4. catalyst has amine and carbonyl groups at portals
5. Hot filtration method shows reaction stopped after removing catalyst by filtration.
Now kindly answer following queries,
1. How can I decide my catalyst is heterogeneous or homogeneous?
2. is there any specific test to conduct?
3. Is there any small organic compounds known to act as heterogeneous catalysts?
thank you for your interest and support
1. Based on your data, the catalyst seems to be heterogeneous. Increasing the catalyst amount does not increase the concentration of the catalyst in solution. "Hot filtration method shows reaction stopped after removing catalyst by filtration" indicates that the true catalyst is not in solution.
2. You have already conducted the "specific test"
3. I don't know, but why not.
1. Based on your data, the catalyst seems to be heterogeneous. Increasing the catalyst amount does not increase the concentration of the catalyst in solution. "Hot filtration method shows reaction stopped after removing catalyst by filtration" indicates that the true catalyst is not in solution.
2. You have already conducted the "specific test"
3. I don't know, but why not.
1& 2: the filtration result is pretty definitive - heterogeneous
3 - see Article Catalysis by Organic Solids. Stereoselective Diels−Alder Rea...
Filtration could be a good idea, especially while maintaining the temperature of the reaction mixture. But which: microfiltration, ultrafiltration, nanofiltration? What was the mean pore size of the membrane?
What do you mean by "small organic compound"? What is the measure here? Regards,
Thank you Dr. Miroslaw Grzesik ,
I have filtered through the nylon membrane 0.6 micron size from Merck. catalyst particle size is 10-50 micron so ideally it should not go in to filtrate. moreover FTIR of reaction mixture (filtrate shows absence of catalyst peak).
Small organic molecule means, I wanted to convey that t has less molecular weight (190 g/mol), not a polymer and has ring type structure.
Thank you Dr. Yurii V Geletii for your support for my point
1. we are also thinking the catalyst is heterogeneous probably based on results, but as per other researchers point, small organic molecule with low molecular weight can not be a heterogeneous, so I wanted to prove it experimentally.
Thank you Dr. James E Hanson for the article, it is quite useful.
"small organic molecule with low molecular weight can not be a heterogeneous " Why not if it's insoluble?
Small organic molecule catalyst is p-toluenesulphonic acid. It is solid, but it is soluble in water. Perhaps one of the sulphonic derivatives of naphthalene will be insoluble. Regards,
If you need additional evidence you could do something like adding a small amount of mercury to poison the catalyst. There are thousands of small organic molecules that are catalysts, but going through all them is not so useful. As mentioned above, you already have the experiments to have strong evidence to answer these questions.
Homogeneous catalysts are generally solule in the solvents like ethanol where as the heterogeneous catalysts are in soluble which provide surface area for the reaction.
Hello,
If you are using metal catalyst then you can filter your reaction mixture and do the ICP Analysis of the filtrate.Once you'll perform ICP analysis then you may know the metal content in your filtrate .
If you find metal content in your filtrate then that will confirm the presence of catalyst in your filtrate and catalyst will be homogeneous.
If you don't find any traces of metal in filtrate then your catalyst will be heterogeneous.
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