Mordenite acidity: dependence on the silicon/aluminum ratio and the framework aluminum topology. 1. Sample preparation and physicochemical characterization

Abstract

8473support of the Basic Research Fund administered by the Israeli Academy of Sciences, the contribution of David Yogev to the design of the system and preliminary measurements, and the help of Ofra Levi in some of the calculations. R e t r y NO. Ag, 7440-22-4. References and Notes(1) Yogev, D.; Efrima, S.A series of dealuminated mordenites (with Si/Alf ratios between 7 and 48) was prepared by acid leaching and characterized by using different physicochemical methods. The A1 content of the framework and the distribution of the tetrahedral and octahedral aluminum were determined by 27Al MAS NMR measurements and chemical analysis. Attempts to quantify the number of SiOH defect groups by ' %i MAS NMR measurements (following a procedure given in the literature) failed. The number of silanol groups (and Bransted sites) were determined using 'H MAS NMR investigations. The micro-and mesopore volumes of the samples were derived from measurements of the benzene adsorption isotherms. It was found that low dealumination of the H-mordenites transforms small-into large-port mordenites. The micropore volume diminished again at a high degree of dealumination.

Influence of the Generation of Mesopores on the Hydroisomerization Activity and Selectivity of n-Hexane over Pt/Mordenite

“…These spots are interpreted as mesopores and/or cracks formed in the crystals after acid leaching while the crystallite shape is maintained. The destruction of the mordenite structure, together with the formation of mesopores by acid leaching, has already been mentioned in the literature (5,8,9).…”

“…It is well known that leaching and steaming of mordenite significantly alter the activity of Pt/mordenite (4,5). After dealumination by acid leaching treatments an optimum Si/Al ratio was found for the hydroisomerization of pentane (4,6).…”

Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl

“…8 Recently, the acidity of the zeolite Mordenite has been the subject of much research. [9][10][11][12][13][14] In order to gain better insight into the dynamics of vibrational relaxation and the properties of this surface hydroxyl, we performed a time-resolved vibrational study of deuterated hydroxyls.…”

Catalytic polymerization of N,N-diethanol acrylamide with phthalic anhydride in the presence of H-mordenite and Fe-mordenite zeolites

“…In addition, one has to bear in mind that blocking the internal pores with non-framework species could impose diffusional limitations of organic substrate in the mono-dimensional channel in mordenite and thus restricting the reaction to sites present at the external particle surface and rather substantiate the role of acidity as mentioned earlier. On the other hand, rising the Si/Al ratio (HM1) will increase the number of adsorbed molecules due to the strength of the electrostatic field located in the pores of the zeolite [25]. V p is the total pore volume, r H the value of the average pore radius, S BET the BET surface area.…”