Modification Of The Active Metal Center On Zeolite Y And Its Applications

Active site and structure-activity relationship of the catalysts has been a fundamental problem in the field of catalysis.At present,we only have a vague comprehension of the structure-activity relationship of the solid materials.From the purpose of making it feasible to understand the structure-activity relationship,we selected the microporous NaY zeolite with the regular pore structure on the nanometer scale,A catalyst with relatively high crystallinity and uniform distribution of active components was prepared by systematic study of the preparation conditions of the catalyst.Through the exchange of potassium ions on the chromium-based catalyst and calcined after the reaction,we try to study its microstructure,the valence and distribution of the active sites,the structure-activity relationship between the catalytic properties and the structure using the mean of XRD,XRF,TPR,TPD and on-line chromatography.Research found that the activity of the catalyst increases with the increase of the loading amount.However,when the loading exceeds the certain value,the structure of the NaY collapsed,the active components are agglomerated easily and blocked by Cr₂O₃ crystals.The catalyst still keep the high activity after the regeneration.The catalysts for hydrogen reduction pretreatment with other characterization methods,we guess that Cr³⁺restored by Cr⁶⁺is the main catalytic activity center.Meanwhile,we try to study the structure-activity relationship of the catalysts through the adsorption,which is a relatively simple process for us.It was found that the adsorbent obtained by CuY reduction treatment have a high sorption performance in adsorption desulfurization.The adsorbent by H₂ reduction at the high temperature and self-reduction treatment using N₂ under high temperature showed a high desulfurization rate,we suggesting that these two treatment methods may change the structure of the adsorbent and the valence state of the Cu species,resulting in more adsorption active sites.Moreover,with the decrease of the reduction temperature,the desulfurization rate decreased slightly,while the desulfurization effect was decreased obviously at 100℃,which still higher than CuY with no reduction treatment.XRD and TEM shows that their have Cu particle generated after the reduction,and with the increase of the reduction temperature,the Cu particle size increases.TPR results showed that the dependence of Cu species on molecular sieves had a great effect on the reduction temperature...