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+ Catalyst characterization
+ Material characterization
+ Adsorption
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+ Lewis acids
+ Zeolites
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Nancy Nichols
What are the methods to find Bronsted and Lewis acid sites of...
Dr. Kazuyuki Nakai , you talked about IRMS-TPD. I read two papers. I just need to know that at present your company presents this instrument to clients or it is merely for some research? Thank you.
Dr. Kazuyuki Nakai , you talked about IRMS-TPD. I read two papers. I just need to know that at present your company presents this instrument to clients or it is merely for some research? Thank you.
IRMS-TPD system which is combined technology of NH3 TPD and FTIR. We developed with Prof. NIWA and Katada of Tottori Univ. Microporous and Mesoporous Materials Volume 82, Issues 1–2, 5 July 2005, Pages 105–112
IRMS-TPD system which is combined technology of NH3 TPD and FTIR. We developed with Prof. NIWA and Katada of Tottori Univ. Microporous and Mesoporous Materials Volume 82, Issues 1–2, 5 July 2005, Pages 105–112
I agree with Aitor Hornes, that NH3-TPD allows us to calculate the acidic strength of catalyst. we cannot calculate the exact amount of lewis or bronsted acidic sites. but from some research articles, we can observe that determination of weak, strong acidic sites from desorption amount of NH3 in diffrent temperature zones.
I agree with Aitor Hornes, that NH3-TPD allows us to calculate the acidic strength of catalyst. we cannot calculate the exact amount of lewis or bronsted acidic sites. but from some research articles, we can observe that determination of weak, strong acidic sites from desorption amount of NH3 in diffrent temperature zones.
Dear Colleague Marakatti, 1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached). The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat. 2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites. Finally if substracted the number of acidic sites from step 2 (Lewis +Bronsted) from step 1 (Bronsted only, you can get the number of lewis acidic sites However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted Hope this helping Have a very good day
Dear Colleague Marakatti, 1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached). The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat. 2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites. Finally if substracted the number of acidic sites from step 2 (Lewis +Bronsted) from step 1 (Bronsted only, you can get the number of lewis acidic sites However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted Hope this helping Have a very good day
Thank you very much for your answers but i am not satisified with the answer that is answered for that question . I know NH3 TPD and Py FTIR are the techiniques :) i want to find the Lewis and bronsted acidity other than these techinique.
Thank you very much for your answers but i am not satisified with the answer that is answered for that question . I know NH3 TPD and Py FTIR are the techiniques :) i want to find the Lewis and bronsted acidity other than these techinique.
Model reactions have been used to a great degree. Model compounds I recall be used include 2-methyl-2-pentene and isobutane. It was a long time ago but I think Exxon did some work chracterizing tungsten oxide via the 2M2P reaction. Search the name Gary Mcvicker. Search this topic more generally and you will reviews on the subject like this: Acc. Chem. Res, 1990, 23, 392. There were also a large number of other indicators used other than pyridine, collectively called Hammett indicators. Again, I would refer you back to texts written on this topic such as that by Tanabe or search for more recent papers that reference these eariler works. Also, be aware that all of these techniques have pitfalls: you might not be measuring what you think you are. Ideally, one would apply multiple techniques to the material at hand to develop the most complete picture of the surface acidity/basicity.
Model reactions have been used to a great degree. Model compounds I recall be used include 2-methyl-2-pentene and isobutane. It was a long time ago but I think Exxon did some work chracterizing tungsten oxide via the 2M2P reaction. Search the name Gary Mcvicker. Search this topic more generally and you will reviews on the subject like this: Acc. Chem. Res, 1990, 23, 392. There were also a large number of other indicators used other than pyridine, collectively called Hammett indicators. Again, I would refer you back to texts written on this topic such as that by Tanabe or search for more recent papers that reference these eariler works. Also, be aware that all of these techniques have pitfalls: you might not be measuring what you think you are. Ideally, one would apply multiple techniques to the material at hand to develop the most complete picture of the surface acidity/basicity.
Dr. Kazuyuki Nakai , you talked about IRMS-TPD. I read two papers. I just need to know that at present your company presents this instrument to clients or it is merely for some research?
Thank you.
Dr. Kazuyuki Nakai , you talked about IRMS-TPD. I read two papers. I just need to know that at present your company presents this instrument to clients or it is merely for some research?
Thank you.
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IRMS-TPD system which is combined technology of NH3 TPD and FTIR. We developed with Prof. NIWA and Katada of Tottori Univ.
Microporous and Mesoporous Materials
Volume 82, Issues 1–2, 5 July 2005, Pages 105–112
IRMS-TPD system which is combined technology of NH3 TPD and FTIR. We developed with Prof. NIWA and Katada of Tottori Univ.
Microporous and Mesoporous Materials
Volume 82, Issues 1–2, 5 July 2005, Pages 105–112
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Ahmed I. Osman can I use 4-Dimethylaminopyridine instead of 2,6-dimethylpyridine?
Ahmed I. Osman can I use 4-Dimethylaminopyridine instead of 2,6-dimethylpyridine?
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Dear Vijaykumar Marakatti
You are very welcome
Have a very good day
Ahmed
Dear Vijaykumar Marakatti
You are very welcome
Have a very good day
Ahmed
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What methodology did you finally choose?
What methodology did you finally choose?
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I agree with Aitor Hornes, that NH3-TPD allows us to calculate the acidic strength of catalyst. we cannot calculate the exact amount of lewis or bronsted acidic sites. but from some research articles, we can observe that determination of weak, strong acidic sites from desorption amount of NH3 in diffrent temperature zones.
I agree with Aitor Hornes, that NH3-TPD allows us to calculate the acidic strength of catalyst. we cannot calculate the exact amount of lewis or bronsted acidic sites. but from some research articles, we can observe that determination of weak, strong acidic sites from desorption amount of NH3 in diffrent temperature zones.
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Dear Colleague Marakatti,
1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached).
The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat.
2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites.
Finally if substracted the number of acidic sites from step 2 (Lewis +Bronsted) from step 1 (Bronsted only, you can get the number of lewis acidic sites
However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted
Hope this helping
Have a very good day
Dear Colleague Marakatti,
1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached).
The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat.
2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites.
Finally if substracted the number of acidic sites from step 2 (Lewis +Bronsted) from step 1 (Bronsted only, you can get the number of lewis acidic sites
However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted
Hope this helping
Have a very good day
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Thank you very much for your answers but i am not satisified with the answer that is answered for that question . I know NH3 TPD and Py FTIR are the techiniques :) i want to find the Lewis and bronsted acidity other than these techinique.
Thank you very much for your answers but i am not satisified with the answer that is answered for that question . I know NH3 TPD and Py FTIR are the techiniques :) i want to find the Lewis and bronsted acidity other than these techinique.
More
VOTE
Model reactions have been used to a great degree. Model compounds I recall be used include 2-methyl-2-pentene and isobutane. It was a long time ago but I think Exxon did some work chracterizing tungsten oxide via the 2M2P reaction. Search the name Gary Mcvicker. Search this topic more generally and you will reviews on the subject like this: Acc. Chem. Res, 1990, 23, 392.
There were also a large number of other indicators used other than pyridine, collectively called Hammett indicators. Again, I would refer you back to texts written on this topic such as that by Tanabe or search for more recent papers that reference these eariler works.
Also, be aware that all of these techniques have pitfalls: you might not be measuring what you think you are. Ideally, one would apply multiple techniques to the material at hand to develop the most complete picture of the surface acidity/basicity.
Model reactions have been used to a great degree. Model compounds I recall be used include 2-methyl-2-pentene and isobutane. It was a long time ago but I think Exxon did some work chracterizing tungsten oxide via the 2M2P reaction. Search the name Gary Mcvicker. Search this topic more generally and you will reviews on the subject like this: Acc. Chem. Res, 1990, 23, 392.
There were also a large number of other indicators used other than pyridine, collectively called Hammett indicators. Again, I would refer you back to texts written on this topic such as that by Tanabe or search for more recent papers that reference these eariler works.
Also, be aware that all of these techniques have pitfalls: you might not be measuring what you think you are. Ideally, one would apply multiple techniques to the material at hand to develop the most complete picture of the surface acidity/basicity.
More
VOTE
Hello Ahmed,
Thank you very much for your Input on this.
I totally agree with the TG-DTA analysis for determining the both acidic Sites.
Regards
Hello Ahmed,
Thank you very much for your Input on this.
I totally agree with the TG-DTA analysis for determining the both acidic Sites.
Regards
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