Hi Pavla

in zeolites the number of bronsted sites depende on the ratio of Si/Al and is constant for a specific structure. If the ratio Si/Al increases the number of bronsted sites decreases and de lewis sites increases, leading to distribution of acidic sites on surface of different acidic forces that leads to interesting chemical transformations. If you want to maintain the same ratio of Si/Al, you will have to promote acid bronsted sites with zirconia, for example.

Dear Pavla,

We are currently doing some experimental work on that subject, but didn't advance much yet. Meanwhile, I wonder whether you have seen the enclosed paper.

All the best.

Sincerely,

Carlos

[email protected]

Hello,

You can possibly start from a zeolite in ammonium form and simply do repeated exchanges with a diluted acid (by taking care about the dealumination at low pH). Then avoid calcination ? In this paper, you can find the populations of acid B and L sites in function of the temperature and Si/Al ratio for Y zeolites.

Adsorption and Desorption of a Model Hydrocarbon Mixture Over HY Zeolite Under Dry and Wet Conditions J. Phys. Chem. C 119 (2014) p. 315-331.

Bruno

Dear Carlos,

thanks for the paper, it is very nice work but unfortunatelly this procedure is not suitable for our purposes. We would like to study experimentally and theorethically the role of Lewis and Bronsted sites in one particular reaction. Therefore ion-exchange which maby cause channel constriction or generation of extra-framework alumina Lewis sites is not the best way for us.

Dear Bruno,

I am afarid that by this ion-exchange we will increase the total acid sites amounts and also the ratio of Lewis and Bronsted sites (similarly as reported in the paper, which Carlos posted here). Then it will be hard to judge which factor has influenced the catalytic results.. Anyway thanks for answer and the paper.

Pavla

Pavla Eliášová

Does anybody have experience with the synthesis of purely or mostly Bronsted acid site zeolite? I would like to prepare a zeolite containing mainly Bronsted acid sites and then the same one with mixed Bronsted and Lewis acidity.

Respected, Pavla Eliášová

Had you gotten the answer of this question? If yes, please share your experience.

Bundle of Thanks in advance

I would like to know how to know, and by what method that we know exactly where is Bronsted and whewe is lewis acid sites: any one know NMR solid? for me, I also think that we can got the Bronsted acid site by ion exchange method.

Hi Hieu Do Trung,

Using the thermodesorption of ammonia by the gravimetric metthod, it determines the mmol of NH3/g (total number acid sites), by

Infrared thermodesorption you can know the relationship of bronsted and lewis sites.